First full rewrite

nass-introduction.org

@@ -1672,43 +1672,28 @@ CLOSED: [2025-04-17 Thu 16:48]
 :END:
 **** Accelerating electrons to produce intense X-ray
 
-- Explain what is a Synchrotron:
+Synchrotron radiation facilities function as particle accelerator light sources, where electrons are accelerated to near the speed of light.
-  - A particle (electrons) accelerator light source
+As these electrons traverse magnetic fields, typically generated by insertion devices or bending magnets, they produce exceptionally bright light known as synchrotron light.
-  - Electrons produce very bright light, called synchrotron light
+This intense electromagnetic radiation, particularly in the X-ray spectrum, is subsequently utilized for the detailed study of matter.
-  - This very intense light, in the X-ray regime, is then used to study matter.
+Approximately 70 synchrotron light sources are operational worldwide, with prominent facilities illustrated in Figure ref:fig:introduction_synchrotrons.
-- There are around 70 Synchrotron light sources in the world
+The global distribution underscores the significant utility of synchrotron light for the scientific community.
-  Some of the main ones are shown in Figure ref:fig:introduction_synchrotrons.
-  This shows how useful the produced light is for the scientific community.
 
 #+name: fig:introduction_synchrotrons
 #+caption: Major synchrotron radiation facilities in the world. 3rd generation Synchrotrons are shown in blue. Planned upgrades to 4th generation are shown in green, and 4th generation Synchrotrons in operation are shown in red.
 #+attr_latex: :width \linewidth
 [[file:figs/introduction_synchrotrons.png]]
 
-There are two main parts in the Synchrotron:
+These facilities fundamentally comprise two main parts: the accelerator complex, where electron acceleration and light generation occur, and the beamlines, where the intense X-ray beams are conditioned and directed for experimental use.
-- The accelerator where electrons are accelerated close to the speed of light
-  The generation of the synchrotron light is made by placing magnetic fields on the electron beam path.
-  These are called Insertion device or Bending magnet.
-- The beamlines where the intense X-ray beam is used to study matter
 
 **** The European Synchrotron Radiation Facility
 
-European Synchrotron Radiation Facility (ESRF):
+The European Synchrotron Radiation Facility (ESRF), shown in Figure ref:fig:introduction_esrf_picture, is a joint research institution supported by 19 member countries.
-- Joint research facility situated in Grenoble, France
+Since commencing user operations in 1994, the ESRF was recognized as the world's first third-generation synchrotron source.
-- supported by 19 countries
+Its accelerator complex, schematically depicted in Figure ref:fig:introduction_esrf_schematic, includes a linear accelerator, a booster synchrotron for accelerating electrons close to light speed, and an 844-meter circumference storage ring where electrons are maintained for light production.
-- Opened for user operation in 1994: World's first third generation synchrotron (i.e. integrating )
+Radiating from the storage ring are over 40 beamlines, each equipped with specialized instrumentation catering to a diverse range of scientific disciplines, including structural biology and materials science under various conditions.
-
-Accelerator (Schematically shown in Figure ref:fig:introduction_esrf_schematic):
-- The Linear accelerator: where the electrons are
-- Booster: electrons are accelerated closed to the speed of light
-- Storage Ring: where the electrons are stored. Circumference of 844m.
-
-Then, there are over 40 beamlines all around the storage ring:
-- Large diversity in terms of instrumentation and science
-- Science that can be performed: structural biology, structure of materials, matter at extreme, ...
 
 #+name: fig:instroduction_esrf
-#+caption: Schematic (\subref{fig:introduction_esrf_schematic}) and picture (\subref{fig:introduction_esrf_picture}) of the European Synchrotron Radiation Facility
+#+caption: Schematic (\subref{fig:introduction_esrf_schematic}) and picture (\subref{fig:introduction_esrf_picture}) of the European Synchrotron Radiation Facility, situated in Grenoble, France
 #+attr_latex: :options [htbp]
 #+begin_figure
 #+attr_latex: :caption \subcaption{\label{fig:introduction_esrf_schematic} Schematic of the ESRF. The linear accelerator is shown in blue, the booster synchrotron in purple and the storage ring in green. There are over 40 beamlines, the ID31 beamline is highlighted in red}
@@ -1727,16 +1712,15 @@ Then, there are over 40 beamlines all around the storage ring:
 
 **** 3rd and 4th Generation Light Sources
 
-ESRF–EBS (Extremely Brilliant Source): [[cite:&raimondi21_commis_hybrid_multib_achrom_lattic]]
+In August 2020, following an extensive 20-month upgrade period, the ESRF inaugurated its Extremely Brilliant Source (EBS), establishing it as the world's premier fourth-generation synchrotron [[cite:&raimondi21_commis_hybrid_multib_achrom_lattic]].
-- In August 2020, after a 20-month shutdown, the ESRF is the first fourth-generation
+This advancement was predicated on a novel storage ring concept engineered to significantly enhance the brilliance and coherence of the emitted X-ray beams.
-- It uses a new storage ring concept that allows increased brilliance and coherence of the X-ray beams
+Brilliance, a key figure of merit for synchrotron sources, experienced an approximate 100-fold increase with the implementation of EBS, as shown in the historical evolution depicted in Figure ref:fig:introduction_moore_law_brillance.
-  The brilliance (also called brightness) is figure of merit for Synchrotron.
+While this enhanced beam quality presents unprecedented scientific opportunities, it concurrently introduces considerable engineering challenges, particularly concerning sample positioning.
-  It corresponds to ...
+# TODO - Say that regarding what is interesting for us: sample positioning
-  100x increase with the EBS
-- This new beam offers many new scientific opportunities, but also creates many engineering challenges.
 
 #+name: fig:introduction_moore_law_brillance
 #+caption: Evolution of the peak brilliance (expressed in $\text{photons}/s/mm^2/mrad^2/0.1\%BW$) of synchrotron radiation facilities. Note the vertical logarithmic scale.
+#+attr_latex: :scale 0.9
 [[file:figs/introduction_moore_law_brillance.png]]
 
 ** The ID31 ESRF Beamline
@@ -1745,16 +1729,16 @@ ESRF–EBS (Extremely Brilliant Source): [[cite:&raimondi21_commis_hybrid_multib
 :END:
 **** Beamline Layout
 
-Beamline "layout" refers to the series of elements located in between the "light source" and the sample.
+# TODO - Make a short introduction to the beamline goal
-- Each beamline start with a "white" beam, which is just generated by the insertion device (i.e. the "source").
+
-  This beam has very high power (typically above kW), and is typically not directly used on the sample.
+The term "beamline layout" encompasses the sequence of optical components situated between the X-ray source (an insertion device in this context) and the sample.
-- Instead, the beam goes through a series of optical elements (absorbers, mirrors, slits, monochromators, etc.) to filter and "shape" the x-ray beam as wanted.
+Initially, a "white" beam, characterized by high power (often exceeding several kilowatts) and a broad energy spectrum, is generated by the source.
-  These elements are located in several Optical Hutches as shown in Figure Figure ref:fig:introduction_id31_oh
+This "white" beam is generally unsuitable for direct sample irradiation and is therefore processed through a series of optical elements housed within shielded enclosures known as Optical Hutches (OH), illustrated for ID31 in Figure ref:fig:introduction_id31_oh.
-- Then, there is the Experimental Hutch (Figure ref:fig:introduction_id31_cad).
+These elements, including absorbers, mirrors, slits, and monochromators, are employed to filter, shape, and select the desired energy range of the X-ray beam.
-  For some experiments (that are especially of interest here), focusing optics are used.
+Following the optical hutches, the conditioned beam enters the Experimental Hutch (Figure ref:fig:introduction_id31_cad), where, for experiments pertinent to this work, focusing optics are utilized.
-  The sample is located on the sample stage (also called "end-station"), as is used to position the sample with respect to the x-ray.
+The sample is mounted on a positioning stage, referred to as the "end-station," which facilitates precise alignment relative to the X-ray beam.
-  Detectors are used to capture the image formed by the x-ray going through the sample
+Detectors are used to capture the X-rays transmitted through or scattered by the sample.
-- Explain the XYZ frame for all the thesis (ESRF convention: X: x-ray, Z gravity up)
+Throughout this thesis, the standard ESRF coordinate system is adopted, wherein the X-axis aligns with the beam direction, Y is transverse horizontal, and Z is vertical upwards against gravity.
 
 #+name: fig:introduction_id31_oh
 #+caption: Schematic of the two ID31 optical hutches: OH1 (\subref{fig:introduction_id31_oh1}) and OH2 (\subref{fig:introduction_id31_oh2}). Distance from the source (the insertion device) is indicated in meters.
@@ -1779,19 +1763,12 @@ Beamline "layout" refers to the series of elements located in between the "light
 
 **** Positioning End Station: The Micro-Station
 
-The end station on the ID31 beamline is called the "micro-station":
+The specific end-station employed on the ID31 beamline is designated the "micro-station".
-- It is composed of several stacked stages, shown in Figure ref:fig:introduction_micro_station_dof:
+As depicted in Figure ref:fig:introduction_micro_station_dof, it comprises a stack of positioning stages: a translation stage (blue), a tilt stage (red), a spindle for continuous rotation (yellow), and a micro-hexapod (purple).
-  - A translation stage (blue)
+The sample itself (cyan), potentially housed within complex sample environments (e.g., for high pressure or varying temperatures) and weighing up to 50kg, is mounted on top of this assembly.
-  - Tilt stage (red)
+Each stage serves distinct positioning functions; for example, the micro-hexapod enables fine static adjustments, while the Ty translation and Rz rotation stages are utilized for specific scan types.
-  - Spindle (yellow) for continuous rotation
+The design objectives prioritized maximum stiffness and minimal positioning errors across its operational stroke.
-  - Micro hexapod (purple)
+The main components within the experimental hutch—focusing optics, sample stage, sample, and detector—are affixed to a common granite base for enhanced stability, as shown in Figure ref:fig:introduction_id31_cad.
-  - The sample (cyan), which can weight up to 50kg
-    Typically the samples are fixed inside a sample environment, to provide special environment: high pressure, low or high temperatures, high magnetic field, etc.
-
-Presentation of the Micro-Station in details:
-- Goal of each stage (e.g. micro-hexapod: static positioning, Ty and Rz: scans, ...)
-- Stroke
-- Initial design objectives: as stiff as possible, smallest errors as possible
 
 #+name: fig:introduction_micro_station
 #+caption: CAD view of the ID31 Experimal Hutch (\subref{fig:introduction_id31_cad}). There are typically four main elements: the focusing optics in yellow, the sample stage in green, the sample itself in purple and the detector in blue. All these elements are fixed to the same granite. CAD view of the The micro-station with the associated degrees of freedom (\subref{fig:introduction_micro_station_dof}).
@@ -1800,41 +1777,33 @@ Presentation of the Micro-Station in details:
 #+attr_latex: :caption \subcaption{\label{fig:introduction_id31_cad} Experimental Hutch}
 #+attr_latex: :options {0.52\textwidth}
 #+begin_subfigure
-#+attr_latex: :width 0.95\linewidth
+#+attr_latex: :height 5cm
 [[file:figs/introduction_id31_station_detector.png]]
 #+end_subfigure
 #+attr_latex: :caption \subcaption{\label{fig:introduction_micro_station_dof} Micro-Station}
 #+attr_latex: :options {0.44\textwidth}
 #+begin_subfigure
-#+attr_latex: :width 0.95\linewidth
+#+attr_latex: :height 5cm
 [[file:figs/introduction_micro_station_dof.png]]
 #+end_subfigure
 #+end_figure
 
 **** Example of Scientific experiments performed on ID31
 
-Such end station, being composed of several stacked stages, has an high mobility and allow for various scientific experiments (i.e. imaging techniques).
+The high mobility afforded by the multi-stage configuration of the micro-station enables diverse imaging techniques.
+Two illustrative examples are provided.
 
-Two examples are here given to showcase the possibility offers by
+Firstly, tomography experiments are conducted as illustrated schematically in Figure ref:fig:introduction_tomography_schematic.
+In this technique, the sample is placed in the X-ray beam path, and its orientation is controlled via a rotation stage.
+Projection images are acquired by the detector at numerous discrete angular positions.
+Provided the point of interest within the sample remains accurately centered on the beam throughout the rotation, a three-dimensional reconstruction, such as the one presented in Figure ref:fig:introduction_tomography_results, can be generated [[cite:&schoeppler17_shapin_highl_regul_glass_archit]].
 
-
+Secondly, mapping or scanning experiments are performed, often involving focused X-ray beams, as depicted in Figure ref:fig:introduction_scanning_schematic.
-Tomography experiment:
+The sample is translated, typically in the plane perpendicular to the beam (Y and Z directions), while data is collected at each position.
-- Experimental setup illustrated in Figure ref:fig:introduction_tomography_schematic.
+An example [[cite:&sanchez-cano17_synch_x_ray_fluor_nanop]] of a resulting two-dimensional map, acquired with 20nm step increments, is shown in Figure ref:fig:introduction_scanning_results.
-- A sample is place on the X-ray beam, and its vertical angle is controlled using a rotation stage.
+The fidelity and resolution of such images are intrinsically linked to the focused beam size and the precision with which the sample position relative to the beam can be maintained.
-- The detector images are captures for many different rotation angles.
+Positional instabilities, such as vibrations and thermal drifts, inevitably lead to blurring and distortion in the acquired data.
-- A 3D image of the sample, such as the one shown in Figure ref:fig:introduction_tomography_results (taken from [[cite:&schoeppler17_shapin_highl_regul_glass_archit]]), can then be reconstructed if the sample's point of interest stays on the beam while it is being rotated.
+Other advanced imaging modalities practiced on ID31 include reflectivity, diffraction tomography, and small/wide-angle X-ray scattering (SAXS/WAXS).
-
-
-Mapping/Scanning experiments:
-- Experimental setup illustrated in Figure ref:fig:introduction_scanning_schematic
-- Optics are used to focus the X-ray beam on the sample.
-- Then, the sample is moved perpendicularly to the beam (i.e. in the Y and Z directions)
-- Example of obtained imagine in Figure ref:fig:introduction_scanning_results, the position of the sample is scanned with 20nm step increments [[cite:&sanchez-cano17_synch_x_ray_fluor_nanop]]
-- The quality/accuracy of the obtained image is directly linked to the beam size and the positioning accuracy of the sample with respect to the focused X-ray beam.
-  Any vibrations and drifts would blur and deforms the obtained image.
-
-
-Other imaging techniques used on ID31 include reflectivity, diffraction tomography, small and wide angle X-ray scattering.
 
 #+name: fig:introduction_tomography
 #+caption: Exemple of a tomography experiment. The sample is rotated and images are taken at several angles (\subref{fig:introduction_tomography_schematic}). Example of one 3D image obtained after tomography (\subref{fig:introduction_tomography_results}).
@@ -1878,9 +1847,8 @@ Other imaging techniques used on ID31 include reflectivity, diffraction tomograp
 :END:
 **** A push towards brighter and smaller beams
 
-Thanks to the improvement of both the light source and the instrumentation, smaller and more stable beams are available.
+Continuous advancements in both synchrotron source technology and X-ray optics have led to the availability of smaller, more intense, and more stable X-ray beams.
-
+The ESRF-EBS upgrade, for instance, resulted in a significantly reduced source size, particularly in the horizontal dimension, coupled with increased brilliance, as illustrated in Figure ref:fig:introduction_beam_3rd_4th_gen.
-First, the EBS upgrade allowed for a smaller source (especially in the horizontal direction) as illustrated in Figure ref:fig:introduction_beam_3rd_4th_gen.
 
 #+name: fig:introduction_beam_3rd_4th_gen
 #+caption: View of the ESRF X-ray beam before the EBS upgrade (\subref{fig:introduction_beam_3rd_gen}) and after the EBS upgrade (\subref{fig:introduction_beam_4th_gen}). The brilliance is increased, whereas the horizontal size and emittance are reduced.
@@ -1900,31 +1868,23 @@ First, the EBS upgrade allowed for a smaller source (especially in the horizonta
 #+end_subfigure
 #+end_figure
 
-- At the start of the ESRF, spot sizes for micro-focusing were in the order to $10\,\mu m$ [[cite:&riekel89_microf_works_at_esrf]].
+Concurrently, substantial progress has been made in micro- and nano-focusing optics since the early days of ESRF, where typical spot sizes were on the order of $10\,\mu m$ [[cite:&riekel89_microf_works_at_esrf]].
-- Since then, lots of developments were perform to decrease the spot size, whether using Zone plates, Mirrors or Refractive lenses [[cite:&barrett16_reflec_optic_hard_x_ray]].
+Various technologies, including zone plates, Kirkpatrick-Baez mirrors, and compound refractive lenses, have been developed and refined, each presenting unique advantages and limitations [[cite:&barrett16_reflec_optic_hard_x_ray]].
-- Each with their advantages and drawbacks.
+The historical reduction in achievable spot sizes is represented in Figure ref:fig:introduction_moore_law_focus.
-- Such evolution is illustrated in Figure ref:fig:introduction_moore_law_focus
+Presently, focused beam dimensions in the range of 10 to 20 nm (Full Width at Half Maximum, FWHM) are routinely achieved on specialized nano-focusing beamlines.
-- Today, spot size in the order of 10 to 20nm FWHM are common for specialized nano-focusing beamline.
 
 #+name: fig:introduction_moore_law_focus
 #+caption: Evolution of the measured spot size for different hard x-ray focusing elements. CRL, KB, FZP, MLL. Adapated from\nbsp{}[[cite:&barrett24_x_optic_accel_based_light_sourc]]
+#+attr_latex: :scale 0.9
 [[file:figs/introduction_moore_law_focus.png]]
 
 **** New Dynamical Positioning Needs
 
-- Higher brilliance / flux density => "Radiation damage".
+The increased brilliance and flux density associated with modern synchrotron sources exacerbate the issue of radiation damage, particularly for sensitive samples and at high-energy beamlines like ID31.
-- This is especially true for high energy beamlines such as ID31.
+Consequently, prolonged exposure of a single sample area to the focused beam must be avoided.
-- This means that the focused beam should not be kept on the sample for long period of time with the risk of damaging the sample.
+Traditionally, experiments were conducted in a "step-scan" mode, illustrated in Figure ref:fig:introduction_scan_step.
-
+In this mode, the sample is moved to the desired position, the detector acquisition is initiated, and a beam shutter is opened for a brief, controlled duration to limit dose before closing; this cycle is repeated for each measurement point.
-Two solutions:
+While effective for mitigating radiation damage, this sequential process can be time-consuming, especially for high-resolution maps requiring numerous points.
-- Traditional way of performing experiments, illustrated in Figure ref:fig:introduction_scan_step.
-  The sample is positioned as wanted, the detector acquisition (i.e. "photon integration") starts, and then a beam shutter is opened for a short period of time to avoid radiation damage.
-  Then it goes to the next position, and this process is repeated.
-  This process can takes of lot of time when high resolution is wanted.
-- An alternative is to perform what is called /fly-scan/ of /continuous-scan/, [[cite:&xu23_high_nsls_ii]].
-  This is illustrated in Figure ref:fig:introduction_scan_fly.
-  As the sample undergoes continuous movement, the detector is triggered either based on the measured position of the sample of based on the time elapsed since the start of the motion.
-  This allows to perform experiments much faster [[cite:&huang15_fly_scan_ptych]] (i.e. better use of the beam time), and have potentially smaller pixel size.
 
 #+name: fig:introduction_scan_mode
 #+caption: Two acquisition modes. In step-by-step mode (\subref{fig:introduction_scan_step}), the motor moves at the wanted imaged position, the detector acquisition is started, the shutter is openned briefly to have the wanted exposition, the detector acquisition is stopped, and the motor can move to a new position. In /fly-scan/ mode (\subref{fig:introduction_scan_fly}), the shutter is openned while the sample is in motion, and the detector is acquired only at the wanted positions, on the /fly/.
@@ -1933,32 +1893,29 @@ Two solutions:
 #+attr_latex: :caption \subcaption{\label{fig:introduction_scan_step} Step by step scan}
 #+attr_latex: :options {0.55\textwidth}
 #+begin_subfigure
-#+attr_latex: :height 6cm
+#+attr_latex: :height 5.5cm
 [[file:figs/introduction_scan_step.png]]
 #+end_subfigure
 #+attr_latex: :caption \subcaption{\label{fig:introduction_scan_fly} Fly scan}
 #+attr_latex: :options {0.44\textwidth}
 #+begin_subfigure
-#+attr_latex: :height 6cm
+#+attr_latex: :height 5.5cm
 [[file:figs/introduction_scan_fly.png]]
 #+end_subfigure
 #+end_figure
 
+An alternative, more efficient approach is the "fly-scan" or "continuous-scan" methodology [[cite:&xu23_high_nsls_ii]], depicted in Figure ref:fig:introduction_scan_fly.
+Here, the sample is moved continuously while the detector is triggered to acquire data "on the fly" at predefined positions or time intervals.
+This technique significantly accelerates data acquisition, enabling better utilization of valuable beamtime and potentially finer spatial sampling [[cite:&huang15_fly_scan_ptych]].
 
-Recent detector developments:
+Furthermore, recent developments in detector technology have yielded sensors with improved spatial resolution, lower noise characteristics, and substantially higher frame rates [[cite:&hatsui15_x_ray_imagin_detec_synch_xfel_sourc]].
-- Better spatial resolution, lower noise and higher frame rates [[cite:&hatsui15_x_ray_imagin_detec_synch_xfel_sourc]].
+Whereas typical integration times for scanning or tomography experiments were previously in the range of 0.1 to 1 second, modern detectors permit integration times on the order of milliseconds, corresponding to frame rates of 100 Hz or higher.
-- For typical scanning/tomography experiments: the detector integration time was in the order to 0.1s to 1s
+This reduction in integration time has two major implications for positioning requirements.
-- This long integration time (i.e. averaging) effectively "filters" out high frequency vibration in the beam position or of the sample's position, resulting in a apparent stable beam (but having bigger apparent size)
+Firstly, for a given spatial sampling ("pixel size"), faster integration necessitates proportionally higher scanning velocities.
-- With higher x-ray beam flux and lower noise in the detector, the integration time can be reduced.
+Secondly, the shorter integration times make the measurements more susceptible to high-frequency vibrations.
-  Typical integration time can be in the over of 1ms, with frame rate in the order of 100Hz or more.
+Previously, longer integration effectively averaged out rapid positional fluctuations, resulting in an apparently larger but stable effective X-ray beam.
-
+With millisecond-scale integration, however, vibrations up to the kilohertz range can significantly degrade data quality.
-This has two main implications related to positioning requirements:
+Therefore, not only must the sample position be stable against long-term drifts, but it must also be actively controlled to minimize vibrations, especially during dynamic fly-scan acquisitions.
-- First: need for faster scans. For a same "pixel size", having an integration time reduced means that the scanning velocity is increased by the same amount.
-- Second: the measurement is more sensitive to high frequency vibration.
-  This means that there is a need to control the position up to higher frequency, typically in the kHz range.
-  When performing dynamic error budgeting, the vibration needs to be integrated up to higher frequencies.
-  Not only the sample position need to be stable (i.e. free of drifts) with respect to the x-ray beam, it also need to be vibration-less
-  Combined with /fly-scan/ mode, this means that the position needs to be well controlled, even during scans.
 
 ** Existing Nano Positioning End-Stations
 :PROPERTIES:
@@ -1966,24 +1923,15 @@ This has two main implications related to positioning requirements:
 :END:
 **** Introduction                                                  :ignore:
 
-In order to highlight the specificity of the developed system:
+To contextualize the system developed within this thesis, a brief overview of existing strategies and technologies for high-accuracy, high-dynamics end-stations is provided.
-- Options to tackle the need of higher accuracy and better dynamical characteristics of end-station is briefly discussed.
+The aim is to identify the specific characteristics that distinguish the proposed system from current state-of-the-art implementations.
-- The goal is to extract specific characteristics of the developed system that puts it apart from currently developed end-station.
 
 **** End-Station with Stacked Stages
 
-Distinction between serial and parallel kinematics: Example of an end-station with 3DoF (Dx, Dy, Rz): Figure ref:fig:introduction_kinematics
+Positioning systems can be broadly categorized based on their kinematic architecture, typically serial or parallel, as exemplified by the 3-Degree-of-Freedom (DoF) platforms in Figure ref:fig:introduction_kinematics.
-- Stack stages (serial kinematics): Figure ref:fig:introduction_serial_kinematics
+Stacked stages, representing serial kinematics (Figure ref:fig:introduction_serial_kinematics), offer decoupled control for each DoF and generally provide larger ranges of motion.
-  Each DoF is decoupled and positioned by only one actuator.
+However, positioning errors (e.g., guiding inaccuracies, thermal expansion) accumulate through the stack, compromising overall accuracy.
-  This usually lead to higher mobility.
+Similarly, the overall dynamic performance (stiffness, resonant frequencies) is limited by the softest component in the stack, often resulting in poor dynamic behavior when many stages are combined.
-  But positioning errors / guiding errors of different stages are combined, and the overall positioning accuracy may be poor.
-  Similarly, the stiffness (i.e dynamical performances) of the overall end-station depends on the stiffness of the individual stages in all DoF, requiring extremely stiff stages.
-  When too many stages are stacked up, the overall stiffness is usually poor, and dynamical performances are not great.
-- Parallel architecture: Figure ref:fig:introduction_parallel_kinematics
-  Motion induced by several actuator are combined to obtain the wanted DoF.
-  Theoretically, the controlled DoF are the same as the stacked stages architecture.
-  But in practice, motion are limited to very small strokes.
-  However, this has the advantage of having much higher stiffness, and therefore better dynamical performances.
 
 #+name: fig:introduction_kinematics
 #+caption: Two positioning platforms with $D_x/D_y/R_z$ degrees of freedom. One is using serial kinematics (\subref{fig:introduction_serial_kinematics}), while the other uses parallel kinematics (\subref{fig:introduction_parallel_kinematics})
@@ -2003,18 +1951,15 @@ Distinction between serial and parallel kinematics: Example of an end-station wi
 #+end_subfigure
 #+end_figure
 
-Most of end-station, because of the wanted high mobility, are composed of stacked stages.
+Conversely, parallel kinematic architectures (Figure ref:fig:introduction_parallel_kinematics) involve the coordinated motion of multiple actuators to achieve the desired end-effector pose.
-In such case, their positioning performance solely depends on the accuracy of each of the individual stages.
+While theoretically capable of similar DoFs, practical implementations are often restricted to smaller workspaces.
+The primary advantage lies in significantly higher structural stiffness and consequently superior dynamic performance.
 
-To have acceptable performance / stability:
+Due to the requirement for extensive mobility in many synchrotron experiments, most end-stations are constructed using stacked stages.
-- A limited number of high performances stages, such as air bearing spindles, are used [[cite:&riekel10_progr_micro_nano_diffr_at]]
+Achieving acceptable stability and accuracy in such systems relies heavily on the inherent precision of individual components and environmental control.
-- Extremely stable hutch temperature, while wanted stability usually reached only after several days without intervention in the hutch [[cite:&leake19_nanod_beaml_id01]]
+Strategies include employing a limited number of high-performance stages, such as air-bearing spindles [[cite:&riekel10_progr_micro_nano_diffr_at]], and maintaining extremely stable thermal environments within the experimental hutch, often requiring extended stabilization times [[cite:&leake19_nanod_beaml_id01]].
-
+Examples of such end-stations, including those at beamlines ID16B [[cite:&martinez-criado16_id16b]] and ID11 [[cite:&wright20_new_oppor_at_mater_scien]], are shown in Figure ref:fig:introduction_passive_stations.
-Two examples of such end-stations are shown in Figure ref:fig:introduction_passive_stations.
+However, when a large number of DoFs are required, the cumulative errors and limited dynamic stiffness of stacked configurations can make experiments with nano-focused beams extremely challenging or infeasible.
-- ID16b [[cite:&martinez-criado16_id16b]]: uses a limited number of stacked stages, and uses extremely accurate air bearing spindle for tomography experiments
-- ID11 [[cite:&wright20_new_oppor_at_mater_scien]]: Spindle, XYZ stage for scanning purposes and small hexapod used for pre-positioning
-
-But when many degrees of freedom are wanted, the overall accuracy and stability usually does not allow (or maybe is making working with nano-focused beam very difficult) for experiments with a nano-beam.
 
 #+name: fig:introduction_passive_stations
 #+caption: Example of two nano end-stations without online metrology: (\subref{fig:introduction_endstation_id16b}) [[cite:&martinez-criado16_id16b]] and (\subref{fig:introduction_endstation_id11}) [[cite:&wright20_new_oppor_at_mater_scien]]
@@ -2036,30 +1981,17 @@ But when many degrees of freedom are wanted, the overall accuracy and stability
 
 **** Online Metrology
 
-The idea of having an external metrology to correct for errors is not new.
+The concept of employing external metrology systems to measure and potentially correct for positioning errors is well-established.
+Ideally, the relative position between the sample's point of interest and the X-ray beam focus would be measured directly.
+In practice, direct measurement is often impossible; instead, the sample position is typically measured relative to a reference frame associated with the focusing optics or defining apertures, providing an indirect measurement.
 
-Ideally, the relative position between the sample and the x-ray beam is measured.
+This metrology data can be utilized in several ways: for post-processing correction of acquired data; for calibration routines to compensate for repeatable, systematic errors; or, most relevantly here, for real-time feedback control.
-In practice, it is not possible, but instead the position of the sample is measured with respect to the focusing optics and/or slits, providing an indirect measurement.
+For applications demanding precise position control, such as maintaining a nanoparticle within a nano-beam during tomography, real-time feedback is essential.
+Various sensor technologies have been employed, with capacitive sensors [[cite:&schroer17_ptynam;&villar18_nanop_esrf_id16a_nano_imagin_beaml;&schropp20_ptynam]] and, increasingly, fiber-based interferometers [[cite:&nazaretski15_pushin_limit;&stankevic17_inter_charac_rotat_stages_x_ray_nanot;&holler17_omny_pin_versat_sampl_holder;&holler18_omny_tomog_nano_cryo_stage;&engblom18_nanop_resul;&schropp20_ptynam;&nazaretski22_new_kirkp_baez_based_scann;&kelly22_delta_robot_long_travel_nano;&xu23_high_nsls_ii;&geraldes23_sapot_carnaub_sirius_lnls]] being prominent choices.
 
-Several strategies:
+Two examples illustrating the integration of online metrology are presented in Figure ref:fig:introduction_metrology_stations.
-- Used for know the relative position of the sample with respect to the x-ray beam.
+The system at NSLS X8C utilized capacitive sensors for rotation stage calibration and image alignment during tomography post-processing [[cite:&wang12_autom_marker_full_field_hard]].
-  Used during the post processing of the obtained data
+The PtiNAMi microscope at DESY P06 employs interferometers directed at a spherical target below the sample for position monitoring during tomography, with plans for future feedback loop implementation [[cite:&schropp20_ptynam]].
-- For calibration purposes. In that way repeatable errors can be compensated.
-- For real time positioning control
-  For some applications, it is not only important to know the relative position of the sample with respect to the X-ray, but it is equality important to precisely control this position.
-  For instance, in order to keep a nano-particle on the beam while a tomography experiment is performed.
-
-Several Sensors have been used, but mainly two types:
-- Capacitive: [[cite:&schroer17_ptynam;&villar18_nanop_esrf_id16a_nano_imagin_beaml;&schropp20_ptynam]]
-- Fiber Interferometers Interferometers: more and more used
-  - Attocube FPS3010 Fabry-Pérot interferometers: [[cite:&nazaretski15_pushin_limit;&stankevic17_inter_charac_rotat_stages_x_ray_nanot;&engblom18_nanop_resul;&nazaretski22_new_kirkp_baez_based_scann]]
-  - Attocube IDS3010 Fabry-Pérot interferometers: [[cite:&holler17_omny_pin_versat_sampl_holder;&holler18_omny_tomog_nano_cryo_stage;&kelly22_delta_robot_long_travel_nano]]
-  - PicoScale SmarAct Michelson interferometers: [[cite:&schroer17_ptynam;&schropp20_ptynam;&xu23_high_nsls_ii;&geraldes23_sapot_carnaub_sirius_lnls]]
-
-Two examples are shown in Figure ref:fig:introduction_metrology_stations, in which metrology systems are used ot monitor the sample's position:
-- Figure ref:fig:introduction_stages_wang: X8C beamline at National Synchrotron Light Source (NSLS). Capacitive sensors are used to calibrate the errors of the rotation stage, and are used during the alignment of different images captures during a tomography experiment [[cite:&wang12_autom_marker_full_field_hard]].
-- Figure ref:fig:introduction_stages_schroer: PtiNAMi microscope at P06 beamline at DESY. Three interferometers are pointed at a ball lens (1cm in diameter) located just below the sample. The spheres allows the sample to be rotated to perform tomography experiments.
-  Interferometers were reported to be used for monitoring, and is planned to be further used in a feedback loop with the piezoelectric stage located just below the sample [[cite:&schropp20_ptynam]].
 
 #+name: fig:introduction_metrology_stations
 #+caption: Two examples of end-station with integrated online metrology. (\subref{fig:introduction_stages_wang}) [[cite:&wang12_autom_marker_full_field_hard]] and (\subref{fig:introduction_stages_schroer}) [[cite:&schroer17_ptynam]]
@@ -2081,25 +2013,16 @@ Two examples are shown in Figure ref:fig:introduction_metrology_stations, in whi
 
 **** Active Control of Positioning Errors
 
-For some applications (especially when using a nano-beam), the sample's position has not only to be measured, but to be controlled using feedback loops.
+For applications requiring active compensation of measured errors, particularly with nano-beams, feedback control loops are implemented.
+Actuation is typically achieved using piezoelectric actuators [[cite:&nazaretski15_pushin_limit;&holler17_omny_pin_versat_sampl_holder;&holler18_omny_tomog_nano_cryo_stage;&villar18_nanop_esrf_id16a_nano_imagin_beaml;&nazaretski22_new_kirkp_baez_based_scann]], 3-phase linear motors [[cite:&stankevic17_inter_charac_rotat_stages_x_ray_nanot;&engblom18_nanop_resul]], or voice coil actuators [[cite:&kelly22_delta_robot_long_travel_nano;&geraldes23_sapot_carnaub_sirius_lnls]].
+In published studies, feedback bandwidth specifications are often omitted.
+Historically, the feedback bandwidth reported for such systems has often been relatively low (around 1 Hz), primarily targeting the compensation of slow thermal drifts.
+More recently, higher bandwidths (up to 100 Hz) have been demonstrated, particularly with the use of voice coil actuators [[cite:&kelly22_delta_robot_long_travel_nano;&geraldes23_sapot_carnaub_sirius_lnls]].
 
-In that case, mainly three actuator types are used:
+Figure ref:fig:introduction_active_stations showcases two end-stations incorporating online metrology and active feedback.
-- Piezoelectric: [[cite:&nazaretski15_pushin_limit;&holler17_omny_pin_versat_sampl_holder;&holler18_omny_tomog_nano_cryo_stage;&villar18_nanop_esrf_id16a_nano_imagin_beaml;&nazaretski22_new_kirkp_baez_based_scann]]
+The ID16A system at ESRF (Figure ref:fig:introduction_stages_villar) uses capacitive sensors and a piezoelectric hexapod to compensate for rotation stage errors and perform accurate scans [[cite:&villar18_nanop_esrf_id16a_nano_imagin_beaml]].
-- 3-phase linear motor: [[cite:&stankevic17_inter_charac_rotat_stages_x_ray_nanot;&engblom18_nanop_resul]]
+Another example, shown in Figure ref:fig:introduction_stages_nazaretski, employs interferometers and piezoelectric stages to compensate for thermal drifts [[cite:&nazaretski15_pushin_limit;&nazaretski17_desig_perfor_x_ray_scann]].
-- Voice Coil: [[cite:&kelly22_delta_robot_long_travel_nano;&geraldes23_sapot_carnaub_sirius_lnls]]
+A more comprehensive review of actively controlled end-stations is provided in Section [...].
-
-In the literature, the feedback bandwidth for such end-station is rarely specificity.
-It is usually slow (in the order of 1Hz), so that only (thermal) drifts are compensated.
-Only recently, high bandwidth (100Hz) have been reported with the use of voice coil actuators [[cite:&kelly22_delta_robot_long_travel_nano;&geraldes23_sapot_carnaub_sirius_lnls]].
-
-Two examples of end-station integrating online-metrology and feedback loops are shown in Figure ref:fig:introduction_active_stations:
-- Figure ref:fig:introduction_stages_villar: ID16a beamline at ESRF (short stroke) Piezoelectric hexapod, rotation stage, Online metrology using many capacitive sensors.
-  The feedback loop (between the capacitive sensors and the piezoelectric hexapod) is used to compensate for errors of the rotation stage, and also to perform accurate scans with the hexapod.
-- Figure ref:fig:introduction_stages_nazaretski: interferometers are used to measure the position of the sample. multi-layer Laue lenses (MLLs) are used to focus the beam down
-  Feedback control is used to compensate for drifts of the positioning stages.
-
-More extensive review of end-station with feedback loops based on online metrology will be given in section [...].
-# TODO - Add section to the review of stages with active vibration control ref:sec:nhexa_platform_review
 
 #+name: fig:introduction_active_stations
 #+caption: Example of two end-stations with real-time position feedback based on an online metrology. (\subref{fig:introduction_stages_villar}) [[cite:&villar18_nanop_esrf_id16a_nano_imagin_beaml]]. (\subref{fig:introduction_stages_nazaretski}) [[cite:&nazaretski17_desig_perfor_x_ray_scann;&nazaretski15_pushin_limit]]
@@ -2119,33 +2042,19 @@ More extensive review of end-station with feedback loops based on online metrolo
 #+end_subfigure
 #+end_figure
 
-For tomography experiments, correcting for guiding errors of the rotation stage is of primary concern.
+For tomography experiments, correcting spindle guiding errors is critical.
-Two approaches can be used:
+Correction stages are typically placed either below the spindle [[cite:&stankevic17_inter_charac_rotat_stages_x_ray_nanot;&holler17_omny_pin_versat_sampl_holder;&holler18_omny_tomog_nano_cryo_stage;&villar18_nanop_esrf_id16a_nano_imagin_beaml;&engblom18_nanop_resul;&nazaretski22_new_kirkp_baez_based_scann;&xu23_high_nsls_ii]] or above it [[cite:&wang12_autom_marker_full_field_hard;&schroer17_ptynam;&schropp20_ptynam;&geraldes23_sapot_carnaub_sirius_lnls]].
-- Having the stage used for correcting the errors below the Spindle. [[cite:&stankevic17_inter_charac_rotat_stages_x_ray_nanot;&holler17_omny_pin_versat_sampl_holder;&holler18_omny_tomog_nano_cryo_stage;&villar18_nanop_esrf_id16a_nano_imagin_beaml;&engblom18_nanop_resul;&nazaretski22_new_kirkp_baez_based_scann;&xu23_high_nsls_ii]]
+In most reported cases, only translational (XYZ) corrections are applied.
-- Having the stage correcting the errors above the Spindle: [[cite:&wang12_autom_marker_full_field_hard;&schroer17_ptynam;&schropp20_ptynam;&geraldes23_sapot_carnaub_sirius_lnls]]
+Payload capacities for these high-precision systems are usually limited, typically handling calibrated samples on the micron scale, although capacities up to 500g have been reported [[cite:&nazaretski22_new_kirkp_baez_based_scann;&kelly22_delta_robot_long_travel_nano]].
-  In all these cases, only XYZ stages are used to compensate for the guiding errors of the spindle.
+The system developed in this thesis aims for payload capabilities approximately 100 times heavier (up to 50 kg) than previous stations.
-
-# Only for mapping: [[cite:&nazaretski15_pushin_limit;&kelly22_delta_robot_long_travel_nano]]
-
-In terms of payload capabilities:
-- All are only supported calibrated, micron scale samples
-- Higher sample masses to up to 500g have been reported in [[cite:&nazaretski22_new_kirkp_baez_based_scann;&kelly22_delta_robot_long_travel_nano]]
-
-100 times heavier payload capabilities than previous stations with similar performances.
 
 **** Long Stroke - Short Stroke architecture
 
-As shown in the previous examples, end-stations integrating online-metrology for nano-positioning are typically limited to only few degrees of freedom with only short stroke capabilities (in the order of $100\,\mu m$).
+End-stations integrating online metrology for active nano-positioning often exhibit limited operational ranges, typically constrained to a few degrees of freedom with strokes around $100\,\mu m$.
-
+An alternative strategy involves a "long stroke-short stroke" architecture, illustrated conceptually in Figure ref:fig:introduction_two_stage_schematic.
-An other strategy, illustrated in Figure ref:fig:introduction_two_stage_schematic, is to use two stacked stages for a single DoF:
+In this configuration, a high-accuracy, high-bandwidth short-stroke stage is mounted on top of a less precise long-stroke stage.
-- A long stroke, with limited accuracy is combined with short stroke stage with good dynamical properties.
+The short-stroke stage actively compensates for errors based on metrology feedback, while the long-stroke stage provides the coarse, large-range motion.
-  The short stroke stage is used to position the sample based on the metrology measurement, while the long stroke is performing large motion.
+This approach allows combining extended travel with high precision and good dynamic response, but is often implemented for only one or a few DoFs, as seen in Figures ref:fig:introduction_two_stage_control_example and ref:fig:introduction_two_stage_control_h_bridge.
-
-Such strategy is typically limited to few degrees of freedom:
-- 1DoF as shown in Figure ref:fig:introduction_two_stage_control_example
-- 3DoF as shown in Figure ref:fig:introduction_two_stage_control_h_bridge
-
-With such strategy, it is possible to obtain an overall stage with long stroke capability and with good accuracy and dynamical properties (brought by the short stroke stage).
 
 #+name: fig:introduction_two_stage_schematic
 #+caption: Typical Long Stroke - Short Stroke architecture. The long stroke stage is ...
@@ -2172,47 +2081,26 @@ With such strategy, it is possible to obtain an overall stage with long stroke c
 * Challenge definition
 **** Introduction                                                  :ignore:
 
-Based on the positioning requirements brought by the 4th light sources, improved focusing optics and development in detector technology, there are several challenges that need to be addressed.
+The advent of fourth-generation light sources, coupled with advancements in focusing optics and detector technology, imposes stringent new requirements on sample positioning systems.
+For the ID31 beamline, the smallest anticipated beam size is approximately 200 nm (horizontal, Dy) by 100 nm (vertical, Dz).
+To effectively utilize such beams, the positioning system must maintain the sample's point of interest within the beam profile throughout the experiment.
+This translates to required peak-to-peak positioning stability better than 200 nm in Dy and 100 nm in Dz, corresponding to RMS values of approximately 30 nm and 15 nm, respectively.
+Furthermore, tilt errors (Ry) must be controlled to below approximately 1.7 µrad peak-to-peak (250 nrad RMS).
 
+Crucially, these specifications must be met even when considering high-frequency vibrations, owing to the use of high-frame-rate detectors.
+These demanding stability requirements must be achieved within the specific context of the ID31 beamline, which necessitates building upon the existing micro-station infrastructure, accommodating a wide range of experimental configurations requiring high mobility, and handling substantial payloads up to 50 kg.
 
-Smallest beam-size foreseen to be used on ID31 is around 200nm x 100nm
+The existing micro-station, despite being composed of high-quality stages, exhibits positioning accuracy limited to approximately $10\,\mu m$ and $10\,\mu\text{rad}$ due to inherent factors such as backlash, mechanical play, thermal expansion, imperfect guiding, and vibrations.
-- During the experiments, the goal is therefore to keep to point of interest of the sample on the beam
+While individual stage encoders can correct motion along their primary axis, they do not compensate for parasitic motions in other degrees of freedom.
-- Therefore, the peak to peak positioning errors should be below 200nm in Dy and 100nm in Dz
+The primary objective of this project is therefore defined as enhancing the positioning accuracy and stability of the ID31 micro-station by roughly two orders of magnitude, to fully leverage the capabilities offered by the ESRF-EBS source and modern detectors, without compromising its existing mobility and payload capacity.
-- RMS errors (/ by 6.6) gives 30nmRMS in Dy and 15nmRMS in Dz.
-- Also the tilt angle Ry error should be below <1.7urad, 250nrad RMS
-
-
-As high frame rate detectors can be used, the specified position errors of the sample should hold even when taking into account high frequency vibrations.
-
-
-Combined with the specificity of ID31:
-- Build on top of the existing micro-station
-- High required mobility to be able to perform many different experiments
-- Handle large payloads (up to 50kg)
-
-
-The current micro-station, while being composed of high performance positioning stages, the positioning accuracy is still limited by several effects:
-- Backlash, play, thermal expansion, guiding imperfections, ...
-- Give some numbers: straightness of the Ty stage for instance, change of $0.1^oC$ with steel gives x nm of motion
-- Vibrations
-- Possibility to have linear/rotary encoders that correct the motion in the considered DoF, but does not change anything to the other 5DoF
-
-Typically, the final position accuracy is around 10um and 10urad.
-
-The goal of this project is therefore to increase the positioning accuracy of the micro-station to fully exploit the new beam and detectors.
 
 **** The Nano Active Stabilization System Concept
 
-In order to address the new positioning requirements, the concept of the Nano Active Stabilization System (further referred to as the "NASS") is proposed.
+To address these challenges, the concept of a Nano Active Stabilization System (NASS) is proposed.
-
+As schematically illustrated in Figure ref:fig:introduction_nass_concept_schematic, the NASS comprises four principal components integrated with the existing micro-station (yellow): a 5-DoF online metrology system (red), a 5- or 6-DoF active stabilization platform (blue), and the associated control system and instrumentation (purple).
-It is composed of mainly four elements (Figure ref:fig:introduction_nass_concept_schematic):
+This system essentially functions as a high-performance, multi-axis vibration isolation and error correction platform situated between the micro-station and the sample.
-- The micro station (in yellow)
+It actively compensates for positioning errors measured by the external metrology system.
-- A 5 degrees of freedom metrology system (in red)
+The overarching goal is to improve the effective positioning accuracy from the micro-station's native $\approx 10\,\mu m$ level down to below $100\,\text{nm}$, while preserving the full mobility and 50 kg payload capability of the underlying stages.
-- A 5 or 6 degrees of freedom stabilization platform (in blue)
-- Control system and associated instrumentation (in purple)
-
-It therefore corresponds to a 5 DoF vibration control platform on top of a complex positioning platform that correct positioning errors based on an external metrology.
-That way, the goal is to improve the positioning accuracy of the micro-station from ~10um to less than 100nm, while keeping the same mobility and payload capabilities.
 
 #+name: fig:introduction_nass_concept_schematic
 #+caption: The Nano Active Stabilization System concept
@@ -2220,63 +2108,47 @@ That way, the goal is to improve the positioning accuracy of the micro-station f
 
 **** Online Metrology system
 
-As the position of the sample is actively controlled based on the measured position, the accuracy of the NASS depends on the accuracy of the metrology system.
+The performance of the NASS is fundamentally reliant on the accuracy and bandwidth of its online metrology system, as the active control is based directly on these measurements.
-
+This metrology system must fulfill several criteria: measure the sample position in 5 DoF (excluding rotation about the vertical Z-axis); ideally, measure position relative to the X-ray focusing optics; possess a measurement range compatible with the micro-station's extensive mobility and continuous spindle rotation; achieve accuracy commensurate with the sub-100 nm positioning target; and offer high bandwidth for real-time control.
-Such metrology system should:
-- Measure the sample's position along 5 DoF (only the rotation along the vertical axis is not measured)
-- Ideally measure the position with respect to the focusing optics
-- Long stroke, as the micro-station as high mobility, compatible with the spindle continuous rotation
-- Have an accuracy compatible with the positioning requirements
-- High bandwidth
-
-Initial Concept:
-- A spherical reflector with flat bottom is fixed just under the sample
-- The center of the sphere coincide with the focused point of the X-ray
-- Fiber interferometers are pointed both on spherical surface and on the bottom flat surface.
-- A tracking system (tip-tilt mechanism) is used to keep the beam perpendicular to the mirror surface: Spherical mirror with center at the point of interest => No Abbe errors
-
-In that case:
-- XYZ positions can be measured from at least 3 interferometers pointing at the spherical surface
-- Rx/Ry angles are measured from at least 3 interferometers pointing at the bottom flat surface
-
-Such metrology system is a complex mechatronics system on its own.
-This metrology system is not further discussed in this thesis as it is still under active development.
-In the following of this thesis, it is supposed that the metrology system is accurate, and high bandwidth.
 
 #+name: fig:introduction_nass_metrology
 #+caption: 2D representation of the NASS metrology system.
 [[file:figs/introduction_nass_metrology.png]]
 
+An initial concept, depicted in Figure ref:fig:introduction_nass_metrology, involves a spherical reflector with a flat bottom surface fixed beneath the sample.
+The sphere's center is intended to coincide with the X-ray focus.
+Fiber interferometers are directed at both the spherical and flat surfaces.
+A tracking system is needed to maintain interferometer alignment, eliminating Abbe errors by measuring directly relative to the point of interest.
+Translational positions (XYZ) are derived from measurements on the spherical surface, while tilt angles (Rx/Ry) are determined from measurements on the flat bottom surface.
+The development of this complex metrology system constitutes a significant mechatronic project in itself and is currently ongoing; it is not further detailed within this thesis.
+For the work presented herein, the metrology system is assumed to provide accurate, high-bandwidth 5-DoF position measurements.
+
 **** Active Stabilization Platform
 
-The Active stabilization platform, located in between the sample and the micro-station should:
+The active stabilization platform, positioned between the micro-station top plate and the sample, must satisfy several demanding requirements.
-- Be able to move the sample in 5 DoF (the vertical rotation is not controlled)
+It needs to provide active motion compensation in 5 DoF (Dx, Dy, Dz, Rx, Ry).
-- Have good dynamical properties such that the sample's position can be controlled up to high frequency
+It must possess excellent dynamic properties to enable high-bandwidth control capable of suppressing vibrations and tracking desired trajectories with nanometer-level precision.
-- Be capable to control the position down to nanometers.
+Consequently, it must be free from backlash and play, and its active components (e.g., actuators) should introduce minimal vibrations.
-  It should therefore be free of play, backlash.
+Critically, it must reliably support and actuate payloads up to 50 kg.
-  Low level of vibration should be induced by the active parts of the platform (such as actuator noise).
+
-- It should accept payloads up to 50kg.
+A suitable candidate architecture for this platform is the Stewart platform (or hexapod), a parallel kinematic mechanism capable of 6-DoF motion.
+Stewart platforms are widely employed in positioning and vibration isolation applications due to their inherent stiffness and potential for high precision.
+Various designs exist, differing in geometry, actuation technology, sensing methods, and control strategies, as exemplified in Figure ref:fig:introduction_stewart_platform_piezo.
+A central challenge addressed in this thesis is the optimal mechatronic design of such an active platform tailored to the specific requirements of the NASS.
 
-A good candidate for the active platform is the Stewart platform:
-- Parallel architecture, capable of controlling the motion in 6DoF
-- Very popular for positioning and vibration control applications
-- Many different designs, in terms of geometry, actuators, sensors and control strategies
-  Figure ref:fig:introduction_stewart_platform_piezo
 # TODO - Review of Stewart platform ref:sec:detail_kinematics_stewart_review
 
-*Challenge*: Optimally designing such active platform
-
 #+name: fig:introduction_stewart_platform_piezo
 #+caption: Example of Stewart platforms. (\subref{fig:introduction_stewart_du14}) [[cite:&du14_piezo_actuat_high_precis_flexib]] and (\subref{fig:introduction_stewart_hauge04}) [[cite:&hauge04_sensor_contr_space_based_six]]
 #+attr_latex: :options [htbp]
 #+begin_figure
-#+attr_latex: :caption \subcaption{\label{fig:introduction_stewart_du14}PZT based, for positioning purposes}
+#+attr_latex: :caption \subcaption{\label{fig:introduction_stewart_du14}Piezo based, for positioning purposes}
 #+attr_latex: :options {0.49\textwidth}
 #+begin_subfigure
 #+attr_latex: :width 0.95\linewidth
 [[file:figs/introduction_stewart_du14.png]]
 #+end_subfigure
-#+attr_latex: :caption \subcaption{\label{fig:introduction_stewart_hauge04}Voice coil based, Cubic architecture, for vibration isolation}
+#+attr_latex: :caption \subcaption{\label{fig:introduction_stewart_hauge04}Voice coil based, for vibration isolation}
 #+attr_latex: :options {0.49\textwidth}
 #+begin_subfigure
 #+attr_latex: :width 0.95\linewidth
@@ -2286,161 +2158,111 @@ A good candidate for the active platform is the Stewart platform:
 
 **** MIMO robust control strategies
 
-The NASS also includes feedback control:
+The NASS inherently involves multi-input, multi-output (MIMO) feedback control.
-- from the measured position of the sample using the online metrology
+The control system must process position measurements from the online metrology system and reference positions derived from the desired micro-station movements, commanding the active platform in real time to stabilize the sample and compensate for all error sources, including stage imperfections, thermal drifts, and vibrations.
-- from the wanted position of the sample (based on the wanted motion of each of the micro-station stages)
+Ensuring the stability and robustness of these feedback loops is paramount, especially within the demanding operational context of a synchrotron beamline, which requires reliable 24/7 operation with minimal intervention.
-- the active platform is controlled in real time to stabilize the sample's position, compensating for all the errors of the micro-station stages, thermal drifts, etc.
+This contrasts with many traditional synchrotron instruments built using proven, passively stable components like stepper motors and conventional bearings.
 
-When feedback control is being used, attention should be made on the stability of the feedback loop.
+Several factors complicate the design of robust feedback control for the NASS.
-This is especially important in the context of a beamline application, as the instrument should be able to 24/7 with minimum intervention.
+The system must perform reliably across diverse experimental conditions, including different scan types (tomography, linear scans) and velocities (slow drifts to fast fly-scans).
-That is why most of end-stations are based on well-proven design (stepper motors, linear guides, ball bearing, ...).
+The continuous rotation of the spindle introduces gyroscopic coupling effects and means actuators rotate relative to stationary sensors, altering the system dynamics.
-
+Perhaps the most significant challenge is the wide variation in payload mass, from potentially 1 kg up to 50 kg.
-This need for robust feedback control is there made difficult due to:
+High-performance positioning controllers often assume a fixed, well-characterized payload, as seen in applications like lithography or atomic force microscopy (AFM).
-- Many different configurations (tomography, Ty scans, slow fast, ...)
+Designing for robustness against large payload variations typically necessitates larger stability margins, which can compromise achievable performance.
-- Rotation aspect, gyroscopic effects, actuators are rotating with respect to the sensors
+Furthermore, unlike many systems where the active stage and sample are significantly lighter than the underlying coarse stages, the NASS payload mass can be substantially greater than the mass of the micro-station's top stages.
-- The variety of payloads that will be used, with masses ranging from 1kg to 50kg.
+This leads to strong dynamic coupling between the active platform and the micro-station structure, resulting in a more complex MIMO system with significant cross-talk between axes.
-  Typically, high performance position feedback controllers are working with calibrated payloads (lithography machines, AFM, ...)
+These variations in operating conditions and payload translate into significant uncertainty or changes in the plant dynamics that the controller must handle.
-  Being robust to change of payload inertia means larger stability margins and therefore less performance.
+Therefore, the feedback controller must be designed to be robust against this plant uncertainty while still delivering the required nanometer-level performance.
-- For most of end-stations, the top stages (for small stroke scans) as well as the sample are quite light compared to the long stroke stages.
-  This way, the short stroke stage dynamics is not coupled to the dynamics of the stages bellow.
-  In the NASS case, the payload's mass may be one order of magnitude heavier than the mass of the long stroke top platform.
-  This induce a high coupling between the active platform and the micro-station.
-  This there may lead to a MIMO system with more complex dynamics and more coupling.
-- This translates in change on the plant dynamics.
-  The feedback controller therefore need to be robust against plant uncertainty, while providing the wanted level of performance.
 
 **** Predictive Design / Mechatronics approach
 
-- The performances of the system will depend on many factors:
+The overall performance of the NASS will be determined by the interplay of numerous factors, including sensor accuracy and noise, actuator force and bandwidth, mechanical design stiffness and resonances, and the achievable control bandwidth.
-  - sensors
+To navigate this complexity and ensure the final system meets its stringent specifications, a predictive design methodology, specifically a mechatronics approach, is essential.
-  - actuators
+The goal is to rigorously evaluate different concepts, predict performance limitations, and guide the design process towards an optimal solution that functions correctly upon first assembly, given the significant cost and complexity involved.
-  - mechanical design
+Key challenges within this approach include developing appropriate design methodologies, creating accurate simulation models capable of comparing different concepts quantitatively, and converging on a final design that demonstrably achieves the target performance levels.
-  - achievable bandwidth
-- Need to evaluate the different concepts, and predict the performances to guide the design
-- The goal is to design, built and test this system such that it work as expected the first time.
-  Very costly system, so must be correct.
-- *Challenge*:
-  - Proper design methodology
-  - Have accurate models to be able to compare different concepts
-  - Converge to a solution that gives the wanted level of performance
 
 * Original Contributions
 **** Introduction                                                  :ignore:
 
-# TODO - All the papers should be cited
+This thesis presents several original contributions aimed at addressing the challenges inherent in the design, control, and implementation of the Nano Active Stabilization System, primarily within the fields of Control Theory, Mechatronics Design, and Experimental Validation.
-
-In order to address the challenges associated with the development of the Nano Active Stabilization Systems, this thesis proposes several original contributions in the fields of Control, Mechatronics Design and Experimental validation.
 
 **** 6DoF vibration control of a rotating platform
 
-Long stroke / short stroke architectures are usually limited to 1DoF or 2DoF.
+While long stroke-short stroke architectures have been implemented for 1-DoF or 2-DoF systems, this work extends the concept to a fully coupled 6-DoF system operating on a continuously rotating base.
-It is here extended to 6DoF.
+The active platform is designed not merely to correct rotational errors but to simultaneously compensate for errors originating from all underlying micro-station stages.
-
+The application of a continuously rotating Stewart platform for active vibration control and error compensation in this manner is believed to be novel in the reviewed literature.
-The active platform will not only compensate for errors of the rotation stage, but also of all other stages.
-
-To the author's knowledge, the use of a continuously rotating stewart platform for vibration control has not been proved in the literature.
 
 **** Mechatronics design approach
 
-For the design of the NASS, a rigorous mechatronics design approach was conducted.
+A rigorous mechatronics design methodology was applied consistently throughout the NASS development lifecycle [[cite:&dehaeze18_sampl_stabil_for_tomog_exper;&dehaeze21_mechat_approac_devel_nano_activ_stabil_system]].
-
+Although the mechatronics approach itself is not new, its comprehensive application here, from initial concept evaluation using simplified models to detailed design optimization and experimental validation informed by increasingly sophisticated models, is noteworthy.
-[[cite:&dehaeze18_sampl_stabil_for_tomog_exper;&dehaeze21_mechat_approac_devel_nano_activ_stabil_system]]
+Dynamical models were employed at every stage: for initial concept selection, detailed component optimization, understanding experimental observations, and optimizing control strategies.
-
+This thesis documents this process chronologically, illustrating how models of varying complexity can be effectively utilized at different project phases and how design decisions were systematically based on quantitative model predictions and analyses.
-While not new, this approach is here applied from start to finish:
+While the resulting system is highly specific, the documented effectiveness of this integrated design approach may contribute to the broader adoption of mechatronics methodologies in the design of future synchrotron instrumentation.
-- From first concepts using basic models, to concept validation using mode accurate models
-- Detailed design phase: models were used to optimize each individual components
-- Experimental phase: models were still found to have great use.
-  For instance to better understand the observed behavior, and also to optimize the implemented control strategy.
-
-The use of dynamical models were used all along the development.
-
-This document, being written chronologically:
-- Make clear how each models can be useful during different parts of the project
-- Clearly show how each design decision are based on facts / clear conclusions extracted from the models
-- While the developed system is quite specific for the presented application, it shows the effectiveness of this design approach
-
-# TODO - Use passive voice
-I hope this document can make a small contribution in the adoption of the mechatronics approach for the design of future end-station and synchrotron instrumentation.
 
 **** Multi-body simulations with reduced order flexible bodies obtained by FEA
 
-One of the key tool that were used
+A key enabling tool employed extensively in this work was a combined multi-body simulation and Finite Element Analysis technique, specifically utilizing Component Mode Synthesis (CMS) to represent flexible bodies within the multi-body framework [[cite:&brumund21_multib_simul_reduc_order_flexib_bodies_fea]].
-
+This hybrid approach, while established, was experimentally validated in this work for components critical to the NASS, namely amplified piezoelectric actuators and flexible joints.
-Combined multi-body / FEA techniques and experimental validation on a Stewart platform containing amplified piezoelectric actuators
+It proved invaluable for designing and optimizing components intended for integration into a larger, complex dynamic system.
-Super-element of amplified piezoelectric actuator / combined multibody-FEA technique, experimental validation on an amplified piezoelectric actuator and further validated on a complete stewart platform
+This methodology, detailed in Section [...], is presented as a potentially useful tool for future mechatronic instrument development.
-
-While not new:
-- Experimentally validated with both an amplified piezoelectric actuator as well as a flexible joint
-- It proved to be a very useful tool for the design/optimisation of components that have to be integrated in a larger system
-- Believed to be quite useful for the development of future mechatronics instrumentation
-
-Subject of one publication [[cite:&brumund21_multib_simul_reduc_order_flexib_bodies_fea]]
-Further detailed in Section [...].
 # TODO - Section ref:sec:detail_fem
 
 **** Control Robustness by design
 
-One of the main challenge is to design a system that is robust for all the experimental conditions:
+Addressing the critical challenge of robustness across varying experimental conditions (rotation speeds, payloads up to 50 kg) was approached through "robustness by design" rather than relying solely on complex robust control synthesis techniques (like $\mathcal{H}_\infty$ or $\mu\text{-synthesis}$).
-- various rotational velocities used
+The strategy involved selecting a system architecture (mechanics, sensors, actuators) inherently conducive to robust control.
-- payload used can weight up to 50kg
+An example is the deliberate use of collocated actuator/sensor pairs, enabling the potential application of passivity-based control principles to guarantee stability.
-
+Informed architectural choices were made by systematically evaluating different sensor combination strategies (e.g., HAC/LAC, sensor fusion, two-sensor control) and comparing various MIMO decoupling approaches.
-Instead of relying on complex controller synthesis (such as $\mathcal{H}_\infty$ synthesis or $\mu\text{-synthesis}$) to guarantee the robustness and performance, the approach was to:
+This comparative analysis of control architectures, presented in Section [...], was identified as somewhat lacking in existing literature.
-- Choose an adequate architecture (mechanics, sensors, actuators) such that controllers are robust by nature
-- An example is the use of collocated actuator/sensor pairs, such that controller stability can be guaranteed using passivity principles
-- To make informed choices on the chosen architecture:
-  - different ways to combine sensors (HAC-LAC, sensors fusion, two sensor control) were evaluated
-  - different decoupling strategy were compared
-  Such discussion, presented in Section [...] ,were found to be lacking in the literature.
-  # TODO - Section ref:sec:detail_control
 
 **** Active Damping of rotating mechanical systems using Integral Force Feedback
 
-During the conceptual design, it was found the guaranteed stability of the active damping technique called "Integral Force Feedback" (IFF), is lost for rotating platforms as is the case for the NASS.
+During conceptual design, it was found that the guaranteed stability properties of the established active damping technique known as Integral Force Feedback (IFF) are compromised when applied to rotating platforms like the NASS.
-
+To address this instability issue, two modifications to the classical IFF control scheme were proposed and analyzed.
-To overcome this issue, two modifications of the classical IFF control scheme are proposed.
+The first involves a minor adjustment to the control law itself, while the second incorporates physical springs in parallel with the force sensors.
-The first consists of slightly modifying the control law while the second consists of adding springs in parallel with the force sensors.
+Stability conditions and optimal parameter tuning guidelines were derived for both modified schemes.
-Conditions for stability and optimal parameters are derived.
+This is further discussed in Section [...] and was the subject of publications  [[cite:&dehaeze20_activ_dampin_rotat_platf_integ_force_feedb;&dehaeze21_activ_dampin_rotat_platf_using]].
-
-[[cite:&dehaeze20_activ_dampin_rotat_platf_integ_force_feedb;&dehaeze21_activ_dampin_rotat_platf_using]]
-
 # TODO - Section ref:sec:rotating
 
 **** Design of complementary filters using $\mathcal{H}_\infty$ Synthesis
 
-One way to combine sensors is to use "sensor fusion".
+For implementing sensor fusion, where signals from multiple sensors are combined, complementary filters are often employed.
-In such case, complementary filters are used to filter and combine the sensors.
+A novel method for designing these filters using $\mathcal{H}_\infty$ synthesis techniques was developed [[cite:&dehaeze19_compl_filter_shapin_using_synth]].
-
+This method allows explicit shaping of the filter norms, providing guarantees on the performance of the sensor fusion process.
-A method for designing such filter is proposed [[cite:&dehaeze19_compl_filter_shapin_using_synth]], that allows to shape the complementary filters norm, which allows to guarantee the performance of the fusion.
+This design strategy, discussed further in Section [...], has subsequently found application in optimizing sensor fusion for gravitational wave detectors [[cite:&tsang22_optim_sensor_fusion_method_activ]].
-This was latter applied for optimal sensor fusion in gravitational wave detectors [[cite:&tsang22_optim_sensor_fusion_method_activ]].
+The integration of such filters into feedback control architectures can also lead to advantageous control structures, as proposed in [[cite:&verma20_virtual_sensor_fusion_high_precis_contr]] and further studied in Section [...].
-The design strategy is discussed in Section [...].
-# TODO - Section ref:sec:detail_control_sensor
-
-The use of such complementary filters for feedback control can also lead to interesting control architecture, as discussed in [[cite:&verma20_virtual_sensor_fusion_high_precis_contr]] and further developed in Section [...].
 # TODO - Section ref:sec:detail_control_cf
 
 **** Experimental validation of the Nano Active Stabilization System
 
-The positioning performances of the Nano Active Stabilization System is experimentally evaluated/demonstrated on the ID31 beamline.
+The conclusion of this work involved the experimental implementation and validation of the complete NASS on the ID31 beamline.
-
+Experimental results demonstrate that the system successfully improves the effective positioning accuracy of the micro-station from its native ~10 µm level down to the target ~100 nm range during representative scientific experiments.
-The positioning accuracy of the micro-station is effectively improved from the ~10um down to ~100nm while performing experiments.
+Crucially, robustness to variations in sample mass (up to 39 kg tested) and diverse experimental conditions (e.g., tomography scans) was verified.
-Robustness to sample's mass, and different experimental conditions are also verified.
+The NASS thus provides a versatile end-station solution, uniquely combining high payload capacity with nanometer-level accuracy and stability, enabling optimal utilization of the advanced capabilities of the ESRF-EBS beam and associated detectors.
-
+To the author's knowledge, this represents the first demonstration of such a 5-DoF active stabilization platform being used to enhance the accuracy of a complex positioning system to this level.
-This therefore lead to a very versatile end-station, with high payload capabilities and nano-meter accuracy, allowing for full exploitation of the x-ray beam and associated instrumentation.
-
-To the author's knowledge, this is the first time such active platform is used to improve the accuracy of a positioning stage in 5DoF.
 # TODO - Section ref:sec:test_id31
 
 * Thesis Outline - Mechatronics Design Approach
 **** Introduction                                                  :ignore:
 
-This thesis is organized:
+This thesis is structured chronologically, mirroring the phases of the mechatronics development approach employed for the NASS project.
-- to follow the mechatronics development approach, i.e. it is chronologically written.
+It is divided into three chapters, each corresponding to a distinct phase of this methodology: Conceptual Design, Detailed Design, and Experimental Validation.
-
+A brief overview of each chapter's content, is provided below.
-The three chapters corresponds to the three mains parts of the proposed mechatronics approach.
-A brief overview of these three chapters is given bellow.
 
 **** Conceptual design development
 
+
+
+
+
+
+
+
+
+
+
+
 - Talk about dynamic error budgeting
 - Talk about used model
 

nass-introduction.tex

@@ -1,4 +1,4 @@
-% Created 2025-04-17 Thu 17:23
+% Created 2025-04-17 Thu 19:01
 % Intended LaTeX compiler: pdflatex
 \documentclass[a4paper, 10pt, DIV=12, parskip=full, bibliography=totoc]{scrreprt}
 
@@ -27,17 +27,11 @@
 \section*{Synchrotron Radiation Facilities}
 \subsubsection*{Accelerating electrons to produce intense X-ray}
 
-\begin{itemize}
+Synchrotron radiation facilities function as particle accelerator light sources, where electrons are accelerated to near the speed of light.
-\item Explain what is a Synchrotron:
+As these electrons traverse magnetic fields, typically generated by insertion devices or bending magnets, they produce exceptionally bright light known as synchrotron light.
-\begin{itemize}
+This intense electromagnetic radiation, particularly in the X-ray spectrum, is subsequently utilized for the detailed study of matter.
-\item A particle (electrons) accelerator light source
+Approximately 70 synchrotron light sources are operational worldwide, with prominent facilities illustrated in Figure \ref{fig:introduction_synchrotrons}.
-\item Electrons produce very bright light, called synchrotron light
+The global distribution underscores the significant utility of synchrotron light for the scientific community.
-\item This very intense light, in the X-ray regime, is then used to study matter.
-\end{itemize}
-\item There are around 70 Synchrotron light sources in the world
-Some of the main ones are shown in Figure \ref{fig:introduction_synchrotrons}.
-This shows how useful the produced light is for the scientific community.
-\end{itemize}
 
 \begin{figure}[htbp]
 \centering
@@ -45,34 +39,13 @@ This shows how useful the produced light is for the scientific community.
 \caption{\label{fig:introduction_synchrotrons}Major synchrotron radiation facilities in the world. 3rd generation Synchrotrons are shown in blue. Planned upgrades to 4th generation are shown in green, and 4th generation Synchrotrons in operation are shown in red.}
 \end{figure}
 
-There are two main parts in the Synchrotron:
+These facilities fundamentally comprise two main parts: the accelerator complex, where electron acceleration and light generation occur, and the beamlines, where the intense X-ray beams are conditioned and directed for experimental use.
-\begin{itemize}
-\item The accelerator where electrons are accelerated close to the speed of light
-The generation of the synchrotron light is made by placing magnetic fields on the electron beam path.
-These are called Insertion device or Bending magnet.
-\item The beamlines where the intense X-ray beam is used to study matter
-\end{itemize}
 \subsubsection*{The European Synchrotron Radiation Facility}
 
-European Synchrotron Radiation Facility (ESRF):
+The European Synchrotron Radiation Facility (ESRF), shown in Figure \ref{fig:introduction_esrf_picture}, is a joint research institution supported by 19 member countries.
-\begin{itemize}
+Since commencing user operations in 1994, the ESRF was recognized as the world's first third-generation synchrotron source.
-\item Joint research facility situated in Grenoble, France
+Its accelerator complex, schematically depicted in Figure \ref{fig:introduction_esrf_schematic}, includes a linear accelerator, a booster synchrotron for accelerating electrons close to light speed, and an 844-meter circumference storage ring where electrons are maintained for light production.
-\item supported by 19 countries
+Radiating from the storage ring are over 40 beamlines, each equipped with specialized instrumentation catering to a diverse range of scientific disciplines, including structural biology and materials science under various conditions.
-\item Opened for user operation in 1994: World's first third generation synchrotron (i.e. integrating )
-\end{itemize}
-
-Accelerator (Schematically shown in Figure \ref{fig:introduction_esrf_schematic}):
-\begin{itemize}
-\item The Linear accelerator: where the electrons are
-\item Booster: electrons are accelerated closed to the speed of light
-\item Storage Ring: where the electrons are stored. Circumference of 844m.
-\end{itemize}
-
-Then, there are over 40 beamlines all around the storage ring:
-\begin{itemize}
-\item Large diversity in terms of instrumentation and science
-\item Science that can be performed: structural biology, structure of materials, matter at extreme, \ldots{}
-\end{itemize}
 
 \begin{figure}[htbp]
 \begin{subfigure}{0.49\textwidth}
@@ -87,40 +60,30 @@ Then, there are over 40 beamlines all around the storage ring:
 \end{center}
 \subcaption{\label{fig:introduction_esrf_picture} European Synchrotron Radiation Facility}
 \end{subfigure}
-\caption{\label{fig:instroduction_esrf}Schematic (\subref{fig:introduction_esrf_schematic}) and picture (\subref{fig:introduction_esrf_picture}) of the European Synchrotron Radiation Facility}
+\caption{\label{fig:instroduction_esrf}Schematic (\subref{fig:introduction_esrf_schematic}) and picture (\subref{fig:introduction_esrf_picture}) of the European Synchrotron Radiation Facility, situated in Grenoble, France}
 \end{figure}
 \subsubsection*{3rd and 4th Generation Light Sources}
 
-ESRF–EBS (Extremely Brilliant Source): \cite{raimondi21_commis_hybrid_multib_achrom_lattic}
+In August 2020, following an extensive 20-month upgrade period, the ESRF inaugurated its Extremely Brilliant Source (EBS), establishing it as the world's premier fourth-generation synchrotron \cite{raimondi21_commis_hybrid_multib_achrom_lattic}.
-\begin{itemize}
+This advancement was predicated on a novel storage ring concept engineered to significantly enhance the brilliance and coherence of the emitted X-ray beams.
-\item In August 2020, after a 20-month shutdown, the ESRF is the first fourth-generation
+Brilliance, a key figure of merit for synchrotron sources, experienced an approximate 100-fold increase with the implementation of EBS, as shown in the historical evolution depicted in Figure \ref{fig:introduction_moore_law_brillance}.
-\item It uses a new storage ring concept that allows increased brilliance and coherence of the X-ray beams
+While this enhanced beam quality presents unprecedented scientific opportunities, it concurrently introduces considerable engineering challenges, particularly concerning sample positioning.
-The brilliance (also called brightness) is figure of merit for Synchrotron.
-It corresponds to \ldots{}
-100x increase with the EBS
-\item This new beam offers many new scientific opportunities, but also creates many engineering challenges.
-\end{itemize}
-
 \begin{figure}[htbp]
 \centering
-\includegraphics[scale=1]{figs/introduction_moore_law_brillance.png}
+\includegraphics[scale=1,scale=0.9]{figs/introduction_moore_law_brillance.png}
 \caption{\label{fig:introduction_moore_law_brillance}Evolution of the peak brilliance (expressed in \(\text{photons}/s/mm^2/mrad^2/0.1\%BW\)) of synchrotron radiation facilities. Note the vertical logarithmic scale.}
 \end{figure}
 \section*{The ID31 ESRF Beamline}
 \subsubsection*{Beamline Layout}
 
-Beamline ``layout'' refers to the series of elements located in between the ``light source'' and the sample.
+The term ``beamline layout'' encompasses the sequence of optical components situated between the X-ray source (an insertion device in this context) and the sample.
-\begin{itemize}
+Initially, a ``white'' beam, characterized by high power (often exceeding several kilowatts) and a broad energy spectrum, is generated by the source.
-\item Each beamline start with a ``white'' beam, which is just generated by the insertion device (i.e. the ``source'').
+This ``white'' beam is generally unsuitable for direct sample irradiation and is therefore processed through a series of optical elements housed within shielded enclosures known as Optical Hutches (OH), illustrated for ID31 in Figure \ref{fig:introduction_id31_oh}.
-This beam has very high power (typically above kW), and is typically not directly used on the sample.
+These elements, including absorbers, mirrors, slits, and monochromators, are employed to filter, shape, and select the desired energy range of the X-ray beam.
-\item Instead, the beam goes through a series of optical elements (absorbers, mirrors, slits, monochromators, etc.) to filter and ``shape'' the x-ray beam as wanted.
+Following the optical hutches, the conditioned beam enters the Experimental Hutch (Figure \ref{fig:introduction_id31_cad}), where, for experiments pertinent to this work, focusing optics are utilized.
-These elements are located in several Optical Hutches as shown in Figure Figure \ref{fig:introduction_id31_oh}
+The sample is mounted on a positioning stage, referred to as the ``end-station,'' which facilitates precise alignment relative to the X-ray beam.
-\item Then, there is the Experimental Hutch (Figure \ref{fig:introduction_id31_cad}).
+Detectors are used to capture the X-rays transmitted through or scattered by the sample.
-For some experiments (that are especially of interest here), focusing optics are used.
+Throughout this thesis, the standard ESRF coordinate system is adopted, wherein the X-axis aligns with the beam direction, Y is transverse horizontal, and Z is vertical upwards against gravity.
-The sample is located on the sample stage (also called ``end-station''), as is used to position the sample with respect to the x-ray.
-Detectors are used to capture the image formed by the x-ray going through the sample
-\item Explain the XYZ frame for all the thesis (ESRF convention: X: x-ray, Z gravity up)
-\end{itemize}
 
 \begin{figure}[htbp]
 \begin{subfigure}{\textwidth}
@@ -141,36 +104,23 @@ Detectors are used to capture the image formed by the x-ray going through the sa
 \end{figure}
 \subsubsection*{Positioning End Station: The Micro-Station}
 
-The end station on the ID31 beamline is called the ``micro-station'':
+The specific end-station employed on the ID31 beamline is designated the ``micro-station''.
-\begin{itemize}
+As depicted in Figure \ref{fig:introduction_micro_station_dof}, it comprises a stack of positioning stages: a translation stage (blue), a tilt stage (red), a spindle for continuous rotation (yellow), and a micro-hexapod (purple).
-\item It is composed of several stacked stages, shown in Figure \ref{fig:introduction_micro_station_dof}:
+The sample itself (cyan), potentially housed within complex sample environments (e.g., for high pressure or varying temperatures) and weighing up to 50kg, is mounted on top of this assembly.
-\begin{itemize}
+Each stage serves distinct positioning functions; for example, the micro-hexapod enables fine static adjustments, while the Ty translation and Rz rotation stages are utilized for specific scan types.
-\item A translation stage (blue)
+The design objectives prioritized maximum stiffness and minimal positioning errors across its operational stroke.
-\item Tilt stage (red)
+The main components within the experimental hutch—focusing optics, sample stage, sample, and detector—are affixed to a common granite base for enhanced stability, as shown in Figure \ref{fig:introduction_id31_cad}.
-\item Spindle (yellow) for continuous rotation
-\item Micro hexapod (purple)
-\item The sample (cyan), which can weight up to 50kg
-Typically the samples are fixed inside a sample environment, to provide special environment: high pressure, low or high temperatures, high magnetic field, etc.
-\end{itemize}
-\end{itemize}
-
-Presentation of the Micro-Station in details:
-\begin{itemize}
-\item Goal of each stage (e.g. micro-hexapod: static positioning, Ty and Rz: scans, \ldots{})
-\item Stroke
-\item Initial design objectives: as stiff as possible, smallest errors as possible
-\end{itemize}
 
 \begin{figure}[htbp]
 \begin{subfigure}{0.52\textwidth}
 \begin{center}
-\includegraphics[scale=1,width=0.95\linewidth]{figs/introduction_id31_station_detector.png}
+\includegraphics[scale=1,height=5cm]{figs/introduction_id31_station_detector.png}
 \end{center}
 \subcaption{\label{fig:introduction_id31_cad} Experimental Hutch}
 \end{subfigure}
 \begin{subfigure}{0.44\textwidth}
 \begin{center}
-\includegraphics[scale=1,width=0.95\linewidth]{figs/introduction_micro_station_dof.png}
+\includegraphics[scale=1,height=5cm]{figs/introduction_micro_station_dof.png}
 \end{center}
 \subcaption{\label{fig:introduction_micro_station_dof} Micro-Station}
 \end{subfigure}
@@ -178,32 +128,20 @@ Presentation of the Micro-Station in details:
 \end{figure}
 \subsubsection*{Example of Scientific experiments performed on ID31}
 
-Such end station, being composed of several stacked stages, has an high mobility and allow for various scientific experiments (i.e. imaging techniques).
+The high mobility afforded by the multi-stage configuration of the micro-station enables diverse imaging techniques.
+Two illustrative examples are provided.
 
-Two examples are here given to showcase the possibility offers by
+Firstly, tomography experiments are conducted as illustrated schematically in Figure \ref{fig:introduction_tomography_schematic}.
+In this technique, the sample is placed in the X-ray beam path, and its orientation is controlled via a rotation stage.
+Projection images are acquired by the detector at numerous discrete angular positions.
+Provided the point of interest within the sample remains accurately centered on the beam throughout the rotation, a three-dimensional reconstruction, such as the one presented in Figure \ref{fig:introduction_tomography_results}, can be generated \cite{schoeppler17_shapin_highl_regul_glass_archit}.
 
-
+Secondly, mapping or scanning experiments are performed, often involving focused X-ray beams, as depicted in Figure \ref{fig:introduction_scanning_schematic}.
-Tomography experiment:
+The sample is translated, typically in the plane perpendicular to the beam (Y and Z directions), while data is collected at each position.
-\begin{itemize}
+An example \cite{sanchez-cano17_synch_x_ray_fluor_nanop} of a resulting two-dimensional map, acquired with 20nm step increments, is shown in Figure \ref{fig:introduction_scanning_results}.
-\item Experimental setup illustrated in Figure \ref{fig:introduction_tomography_schematic}.
+The fidelity and resolution of such images are intrinsically linked to the focused beam size and the precision with which the sample position relative to the beam can be maintained.
-\item A sample is place on the X-ray beam, and its vertical angle is controlled using a rotation stage.
+Positional instabilities, such as vibrations and thermal drifts, inevitably lead to blurring and distortion in the acquired data.
-\item The detector images are captures for many different rotation angles.
+Other advanced imaging modalities practiced on ID31 include reflectivity, diffraction tomography, and small/wide-angle X-ray scattering (SAXS/WAXS).
-\item A 3D image of the sample, such as the one shown in Figure \ref{fig:introduction_tomography_results} (taken from \cite{schoeppler17_shapin_highl_regul_glass_archit}), can then be reconstructed if the sample's point of interest stays on the beam while it is being rotated.
-\end{itemize}
-
-
-Mapping/Scanning experiments:
-\begin{itemize}
-\item Experimental setup illustrated in Figure \ref{fig:introduction_scanning_schematic}
-\item Optics are used to focus the X-ray beam on the sample.
-\item Then, the sample is moved perpendicularly to the beam (i.e. in the Y and Z directions)
-\item Example of obtained imagine in Figure \ref{fig:introduction_scanning_results}, the position of the sample is scanned with 20nm step increments \cite{sanchez-cano17_synch_x_ray_fluor_nanop}
-\item The quality/accuracy of the obtained image is directly linked to the beam size and the positioning accuracy of the sample with respect to the focused X-ray beam.
-Any vibrations and drifts would blur and deforms the obtained image.
-\end{itemize}
-
-
-Other imaging techniques used on ID31 include reflectivity, diffraction tomography, small and wide angle X-ray scattering.
 
 \begin{figure}[htbp]
 \begin{subfigure}{0.65\textwidth}
@@ -239,9 +177,8 @@ Other imaging techniques used on ID31 include reflectivity, diffraction tomograp
 \section*{Need of Accurate Positioning End-Stations with High Dynamics}
 \subsubsection*{A push towards brighter and smaller beams}
 
-Thanks to the improvement of both the light source and the instrumentation, smaller and more stable beams are available.
+Continuous advancements in both synchrotron source technology and X-ray optics have led to the availability of smaller, more intense, and more stable X-ray beams.
-
+The ESRF-EBS upgrade, for instance, resulted in a significantly reduced source size, particularly in the horizontal dimension, coupled with increased brilliance, as illustrated in Figure \ref{fig:introduction_beam_3rd_4th_gen}.
-First, the EBS upgrade allowed for a smaller source (especially in the horizontal direction) as illustrated in Figure \ref{fig:introduction_beam_3rd_4th_gen}.
 
 \begin{figure}[htbp]
 \begin{subfigure}{0.69\textwidth}
@@ -259,96 +196,61 @@ First, the EBS upgrade allowed for a smaller source (especially in the horizonta
 \caption{\label{fig:introduction_beam_3rd_4th_gen}View of the ESRF X-ray beam before the EBS upgrade (\subref{fig:introduction_beam_3rd_gen}) and after the EBS upgrade (\subref{fig:introduction_beam_4th_gen}). The brilliance is increased, whereas the horizontal size and emittance are reduced.}
 \end{figure}
 
-\begin{itemize}
+Concurrently, substantial progress has been made in micro- and nano-focusing optics since the early days of ESRF, where typical spot sizes were on the order of \(10\,\mu m\) \cite{riekel89_microf_works_at_esrf}.
-\item At the start of the ESRF, spot sizes for micro-focusing were in the order to \(10\,\mu m\) \cite{riekel89_microf_works_at_esrf}.
+Various technologies, including zone plates, Kirkpatrick-Baez mirrors, and compound refractive lenses, have been developed and refined, each presenting unique advantages and limitations \cite{barrett16_reflec_optic_hard_x_ray}.
-\item Since then, lots of developments were perform to decrease the spot size, whether using Zone plates, Mirrors or Refractive lenses \cite{barrett16_reflec_optic_hard_x_ray}.
+The historical reduction in achievable spot sizes is represented in Figure \ref{fig:introduction_moore_law_focus}.
-\item Each with their advantages and drawbacks.
+Presently, focused beam dimensions in the range of 10 to 20 nm (Full Width at Half Maximum, FWHM) are routinely achieved on specialized nano-focusing beamlines.
-\item Such evolution is illustrated in Figure \ref{fig:introduction_moore_law_focus}
-\item Today, spot size in the order of 10 to 20nm FWHM are common for specialized nano-focusing beamline.
-\end{itemize}
 
 \begin{figure}[htbp]
 \centering
-\includegraphics[scale=1]{figs/introduction_moore_law_focus.png}
+\includegraphics[scale=1,scale=0.9]{figs/introduction_moore_law_focus.png}
 \caption{\label{fig:introduction_moore_law_focus}Evolution of the measured spot size for different hard x-ray focusing elements. CRL, KB, FZP, MLL. Adapated from~\cite{barrett24_x_optic_accel_based_light_sourc}}
 \end{figure}
 \subsubsection*{New Dynamical Positioning Needs}
 
-\begin{itemize}
+The increased brilliance and flux density associated with modern synchrotron sources exacerbate the issue of radiation damage, particularly for sensitive samples and at high-energy beamlines like ID31.
-\item Higher brilliance / flux density => ``Radiation damage''.
+Consequently, prolonged exposure of a single sample area to the focused beam must be avoided.
-\item This is especially true for high energy beamlines such as ID31.
+Traditionally, experiments were conducted in a ``step-scan'' mode, illustrated in Figure \ref{fig:introduction_scan_step}.
-\item This means that the focused beam should not be kept on the sample for long period of time with the risk of damaging the sample.
+In this mode, the sample is moved to the desired position, the detector acquisition is initiated, and a beam shutter is opened for a brief, controlled duration to limit dose before closing; this cycle is repeated for each measurement point.
-\end{itemize}
+While effective for mitigating radiation damage, this sequential process can be time-consuming, especially for high-resolution maps requiring numerous points.
-
-Two solutions:
-\begin{itemize}
-\item Traditional way of performing experiments, illustrated in Figure \ref{fig:introduction_scan_step}.
-The sample is positioned as wanted, the detector acquisition (i.e. ``photon integration'') starts, and then a beam shutter is opened for a short period of time to avoid radiation damage.
-Then it goes to the next position, and this process is repeated.
-This process can takes of lot of time when high resolution is wanted.
-\item An alternative is to perform what is called \emph{fly-scan} of \emph{continuous-scan}, \cite{xu23_high_nsls_ii}.
-This is illustrated in Figure \ref{fig:introduction_scan_fly}.
-As the sample undergoes continuous movement, the detector is triggered either based on the measured position of the sample of based on the time elapsed since the start of the motion.
-This allows to perform experiments much faster \cite{huang15_fly_scan_ptych} (i.e. better use of the beam time), and have potentially smaller pixel size.
-\end{itemize}
 
 \begin{figure}[htbp]
 \begin{subfigure}{0.55\textwidth}
 \begin{center}
-\includegraphics[scale=1,height=6cm]{figs/introduction_scan_step.png}
+\includegraphics[scale=1,height=5.5cm]{figs/introduction_scan_step.png}
 \end{center}
 \subcaption{\label{fig:introduction_scan_step} Step by step scan}
 \end{subfigure}
 \begin{subfigure}{0.44\textwidth}
 \begin{center}
-\includegraphics[scale=1,height=6cm]{figs/introduction_scan_fly.png}
+\includegraphics[scale=1,height=5.5cm]{figs/introduction_scan_fly.png}
 \end{center}
 \subcaption{\label{fig:introduction_scan_fly} Fly scan}
 \end{subfigure}
 \caption{\label{fig:introduction_scan_mode}Two acquisition modes. In step-by-step mode (\subref{fig:introduction_scan_step}), the motor moves at the wanted imaged position, the detector acquisition is started, the shutter is openned briefly to have the wanted exposition, the detector acquisition is stopped, and the motor can move to a new position. In \emph{fly-scan} mode (\subref{fig:introduction_scan_fly}), the shutter is openned while the sample is in motion, and the detector is acquired only at the wanted positions, on the \emph{fly}.}
 \end{figure}
 
+An alternative, more efficient approach is the ``fly-scan'' or ``continuous-scan'' methodology \cite{xu23_high_nsls_ii}, depicted in Figure \ref{fig:introduction_scan_fly}.
+Here, the sample is moved continuously while the detector is triggered to acquire data ``on the fly'' at predefined positions or time intervals.
+This technique significantly accelerates data acquisition, enabling better utilization of valuable beamtime and potentially finer spatial sampling \cite{huang15_fly_scan_ptych}.
 
-Recent detector developments:
+Furthermore, recent developments in detector technology have yielded sensors with improved spatial resolution, lower noise characteristics, and substantially higher frame rates \cite{hatsui15_x_ray_imagin_detec_synch_xfel_sourc}.
-\begin{itemize}
+Whereas typical integration times for scanning or tomography experiments were previously in the range of 0.1 to 1 second, modern detectors permit integration times on the order of milliseconds, corresponding to frame rates of 100 Hz or higher.
-\item Better spatial resolution, lower noise and higher frame rates \cite{hatsui15_x_ray_imagin_detec_synch_xfel_sourc}.
+This reduction in integration time has two major implications for positioning requirements.
-\item For typical scanning/tomography experiments: the detector integration time was in the order to 0.1s to 1s
+Firstly, for a given spatial sampling (``pixel size''), faster integration necessitates proportionally higher scanning velocities.
-\item This long integration time (i.e. averaging) effectively ``filters'' out high frequency vibration in the beam position or of the sample's position, resulting in a apparent stable beam (but having bigger apparent size)
+Secondly, the shorter integration times make the measurements more susceptible to high-frequency vibrations.
-\item With higher x-ray beam flux and lower noise in the detector, the integration time can be reduced.
+Previously, longer integration effectively averaged out rapid positional fluctuations, resulting in an apparently larger but stable effective X-ray beam.
-Typical integration time can be in the over of 1ms, with frame rate in the order of 100Hz or more.
+With millisecond-scale integration, however, vibrations up to the kilohertz range can significantly degrade data quality.
-\end{itemize}
+Therefore, not only must the sample position be stable against long-term drifts, but it must also be actively controlled to minimize vibrations, especially during dynamic fly-scan acquisitions.
-
-This has two main implications related to positioning requirements:
-\begin{itemize}
-\item First: need for faster scans. For a same ``pixel size'', having an integration time reduced means that the scanning velocity is increased by the same amount.
-\item Second: the measurement is more sensitive to high frequency vibration.
-This means that there is a need to control the position up to higher frequency, typically in the kHz range.
-When performing dynamic error budgeting, the vibration needs to be integrated up to higher frequencies.
-Not only the sample position need to be stable (i.e. free of drifts) with respect to the x-ray beam, it also need to be vibration-less
-Combined with \emph{fly-scan} mode, this means that the position needs to be well controlled, even during scans.
-\end{itemize}
 \section*{Existing Nano Positioning End-Stations}
-In order to highlight the specificity of the developed system:
+To contextualize the system developed within this thesis, a brief overview of existing strategies and technologies for high-accuracy, high-dynamics end-stations is provided.
-\begin{itemize}
+The aim is to identify the specific characteristics that distinguish the proposed system from current state-of-the-art implementations.
-\item Options to tackle the need of higher accuracy and better dynamical characteristics of end-station is briefly discussed.
-\item The goal is to extract specific characteristics of the developed system that puts it apart from currently developed end-station.
-\end{itemize}
 \subsubsection*{End-Station with Stacked Stages}
 
-Distinction between serial and parallel kinematics: Example of an end-station with 3DoF (Dx, Dy, Rz): Figure \ref{fig:introduction_kinematics}
+Positioning systems can be broadly categorized based on their kinematic architecture, typically serial or parallel, as exemplified by the 3-Degree-of-Freedom (DoF) platforms in Figure \ref{fig:introduction_kinematics}.
-\begin{itemize}
+Stacked stages, representing serial kinematics (Figure \ref{fig:introduction_serial_kinematics}), offer decoupled control for each DoF and generally provide larger ranges of motion.
-\item Stack stages (serial kinematics): Figure \ref{fig:introduction_serial_kinematics}
+However, positioning errors (e.g., guiding inaccuracies, thermal expansion) accumulate through the stack, compromising overall accuracy.
-Each DoF is decoupled and positioned by only one actuator.
+Similarly, the overall dynamic performance (stiffness, resonant frequencies) is limited by the softest component in the stack, often resulting in poor dynamic behavior when many stages are combined.
-This usually lead to higher mobility.
-But positioning errors / guiding errors of different stages are combined, and the overall positioning accuracy may be poor.
-Similarly, the stiffness (i.e dynamical performances) of the overall end-station depends on the stiffness of the individual stages in all DoF, requiring extremely stiff stages.
-When too many stages are stacked up, the overall stiffness is usually poor, and dynamical performances are not great.
-\item Parallel architecture: Figure \ref{fig:introduction_parallel_kinematics}
-Motion induced by several actuator are combined to obtain the wanted DoF.
-Theoretically, the controlled DoF are the same as the stacked stages architecture.
-But in practice, motion are limited to very small strokes.
-However, this has the advantage of having much higher stiffness, and therefore better dynamical performances.
-\end{itemize}
 
 \begin{figure}[htbp]
 \begin{subfigure}{0.49\textwidth}
@@ -366,22 +268,15 @@ However, this has the advantage of having much higher stiffness, and therefore b
 \caption{\label{fig:introduction_kinematics}Two positioning platforms with \(D_x/D_y/R_z\) degrees of freedom. One is using serial kinematics (\subref{fig:introduction_serial_kinematics}), while the other uses parallel kinematics (\subref{fig:introduction_parallel_kinematics})}
 \end{figure}
 
-Most of end-station, because of the wanted high mobility, are composed of stacked stages.
+Conversely, parallel kinematic architectures (Figure \ref{fig:introduction_parallel_kinematics}) involve the coordinated motion of multiple actuators to achieve the desired end-effector pose.
-In such case, their positioning performance solely depends on the accuracy of each of the individual stages.
+While theoretically capable of similar DoFs, practical implementations are often restricted to smaller workspaces.
+The primary advantage lies in significantly higher structural stiffness and consequently superior dynamic performance.
 
-To have acceptable performance / stability:
+Due to the requirement for extensive mobility in many synchrotron experiments, most end-stations are constructed using stacked stages.
-\begin{itemize}
+Achieving acceptable stability and accuracy in such systems relies heavily on the inherent precision of individual components and environmental control.
-\item A limited number of high performances stages, such as air bearing spindles, are used \cite{riekel10_progr_micro_nano_diffr_at}
+Strategies include employing a limited number of high-performance stages, such as air-bearing spindles \cite{riekel10_progr_micro_nano_diffr_at}, and maintaining extremely stable thermal environments within the experimental hutch, often requiring extended stabilization times \cite{leake19_nanod_beaml_id01}.
-\item Extremely stable hutch temperature, while wanted stability usually reached only after several days without intervention in the hutch \cite{leake19_nanod_beaml_id01}
+Examples of such end-stations, including those at beamlines ID16B \cite{martinez-criado16_id16b} and ID11 \cite{wright20_new_oppor_at_mater_scien}, are shown in Figure \ref{fig:introduction_passive_stations}.
-\end{itemize}
+However, when a large number of DoFs are required, the cumulative errors and limited dynamic stiffness of stacked configurations can make experiments with nano-focused beams extremely challenging or infeasible.
-
-Two examples of such end-stations are shown in Figure \ref{fig:introduction_passive_stations}.
-\begin{itemize}
-\item ID16b \cite{martinez-criado16_id16b}: uses a limited number of stacked stages, and uses extremely accurate air bearing spindle for tomography experiments
-\item ID11 \cite{wright20_new_oppor_at_mater_scien}: Spindle, XYZ stage for scanning purposes and small hexapod used for pre-positioning
-\end{itemize}
-
-But when many degrees of freedom are wanted, the overall accuracy and stability usually does not allow (or maybe is making working with nano-focused beam very difficult) for experiments with a nano-beam.
 
 \begin{figure}[htbp]
 \begin{subfigure}{0.49\textwidth}
@@ -400,38 +295,17 @@ But when many degrees of freedom are wanted, the overall accuracy and stability
 \end{figure}
 \subsubsection*{Online Metrology}
 
-The idea of having an external metrology to correct for errors is not new.
+The concept of employing external metrology systems to measure and potentially correct for positioning errors is well-established.
+Ideally, the relative position between the sample's point of interest and the X-ray beam focus would be measured directly.
+In practice, direct measurement is often impossible; instead, the sample position is typically measured relative to a reference frame associated with the focusing optics or defining apertures, providing an indirect measurement.
 
-Ideally, the relative position between the sample and the x-ray beam is measured.
+This metrology data can be utilized in several ways: for post-processing correction of acquired data; for calibration routines to compensate for repeatable, systematic errors; or, most relevantly here, for real-time feedback control.
-In practice, it is not possible, but instead the position of the sample is measured with respect to the focusing optics and/or slits, providing an indirect measurement.
+For applications demanding precise position control, such as maintaining a nanoparticle within a nano-beam during tomography, real-time feedback is essential.
+Various sensor technologies have been employed, with capacitive sensors \cite{schroer17_ptynam,villar18_nanop_esrf_id16a_nano_imagin_beaml,schropp20_ptynam} and, increasingly, fiber-based interferometers \cite{nazaretski15_pushin_limit,stankevic17_inter_charac_rotat_stages_x_ray_nanot,holler17_omny_pin_versat_sampl_holder,holler18_omny_tomog_nano_cryo_stage,engblom18_nanop_resul,schropp20_ptynam,nazaretski22_new_kirkp_baez_based_scann,kelly22_delta_robot_long_travel_nano,xu23_high_nsls_ii,geraldes23_sapot_carnaub_sirius_lnls} being prominent choices.
 
-Several strategies:
+Two examples illustrating the integration of online metrology are presented in Figure \ref{fig:introduction_metrology_stations}.
-\begin{itemize}
+The system at NSLS X8C utilized capacitive sensors for rotation stage calibration and image alignment during tomography post-processing \cite{wang12_autom_marker_full_field_hard}.
-\item Used for know the relative position of the sample with respect to the x-ray beam.
+The PtiNAMi microscope at DESY P06 employs interferometers directed at a spherical target below the sample for position monitoring during tomography, with plans for future feedback loop implementation \cite{schropp20_ptynam}.
-Used during the post processing of the obtained data
-\item For calibration purposes. In that way repeatable errors can be compensated.
-\item For real time positioning control
-For some applications, it is not only important to know the relative position of the sample with respect to the X-ray, but it is equality important to precisely control this position.
-For instance, in order to keep a nano-particle on the beam while a tomography experiment is performed.
-\end{itemize}
-
-Several Sensors have been used, but mainly two types:
-\begin{itemize}
-\item Capacitive: \cite{schroer17_ptynam,villar18_nanop_esrf_id16a_nano_imagin_beaml,schropp20_ptynam}
-\item Fiber Interferometers Interferometers: more and more used
-\begin{itemize}
-\item Attocube FPS3010 Fabry-Pérot interferometers: \cite{nazaretski15_pushin_limit,stankevic17_inter_charac_rotat_stages_x_ray_nanot,engblom18_nanop_resul,nazaretski22_new_kirkp_baez_based_scann}
-\item Attocube IDS3010 Fabry-Pérot interferometers: \cite{holler17_omny_pin_versat_sampl_holder,holler18_omny_tomog_nano_cryo_stage,kelly22_delta_robot_long_travel_nano}
-\item PicoScale SmarAct Michelson interferometers: \cite{schroer17_ptynam,schropp20_ptynam,xu23_high_nsls_ii,geraldes23_sapot_carnaub_sirius_lnls}
-\end{itemize}
-\end{itemize}
-
-Two examples are shown in Figure \ref{fig:introduction_metrology_stations}, in which metrology systems are used ot monitor the sample's position:
-\begin{itemize}
-\item Figure \ref{fig:introduction_stages_wang}: X8C beamline at National Synchrotron Light Source (NSLS). Capacitive sensors are used to calibrate the errors of the rotation stage, and are used during the alignment of different images captures during a tomography experiment \cite{wang12_autom_marker_full_field_hard}.
-\item Figure \ref{fig:introduction_stages_schroer}: PtiNAMi microscope at P06 beamline at DESY. Three interferometers are pointed at a ball lens (1cm in diameter) located just below the sample. The spheres allows the sample to be rotated to perform tomography experiments.
-Interferometers were reported to be used for monitoring, and is planned to be further used in a feedback loop with the piezoelectric stage located just below the sample \cite{schropp20_ptynam}.
-\end{itemize}
 
 \begin{figure}[htbp]
 \begin{subfigure}{0.49\textwidth}
@@ -450,28 +324,17 @@ Interferometers were reported to be used for monitoring, and is planned to be fu
 \end{figure}
 \subsubsection*{Active Control of Positioning Errors}
 
-For some applications (especially when using a nano-beam), the sample's position has not only to be measured, but to be controlled using feedback loops.
+For applications requiring active compensation of measured errors, particularly with nano-beams, feedback control loops are implemented.
+Actuation is typically achieved using piezoelectric actuators \cite{nazaretski15_pushin_limit,holler17_omny_pin_versat_sampl_holder,holler18_omny_tomog_nano_cryo_stage,villar18_nanop_esrf_id16a_nano_imagin_beaml,nazaretski22_new_kirkp_baez_based_scann}, 3-phase linear motors \cite{stankevic17_inter_charac_rotat_stages_x_ray_nanot,engblom18_nanop_resul}, or voice coil actuators \cite{kelly22_delta_robot_long_travel_nano,geraldes23_sapot_carnaub_sirius_lnls}.
+In published studies, feedback bandwidth specifications are often omitted.
+Historically, the feedback bandwidth reported for such systems has often been relatively low (around 1 Hz), primarily targeting the compensation of slow thermal drifts.
+More recently, higher bandwidths (up to 100 Hz) have been demonstrated, particularly with the use of voice coil actuators \cite{kelly22_delta_robot_long_travel_nano,geraldes23_sapot_carnaub_sirius_lnls}.
 
-In that case, mainly three actuator types are used:
+Figure \ref{fig:introduction_active_stations} showcases two end-stations incorporating online metrology and active feedback.
-\begin{itemize}
+The ID16A system at ESRF (Figure \ref{fig:introduction_stages_villar}) uses capacitive sensors and a piezoelectric hexapod to compensate for rotation stage errors and perform accurate scans \cite{villar18_nanop_esrf_id16a_nano_imagin_beaml}.
-\item Piezoelectric: \cite{nazaretski15_pushin_limit,holler17_omny_pin_versat_sampl_holder,holler18_omny_tomog_nano_cryo_stage,villar18_nanop_esrf_id16a_nano_imagin_beaml,nazaretski22_new_kirkp_baez_based_scann}
+Another example, shown in Figure \ref{fig:introduction_stages_nazaretski}, employs interferometers and piezoelectric stages to compensate for thermal drifts \cite{nazaretski15_pushin_limit,nazaretski17_desig_perfor_x_ray_scann}.
-\item 3-phase linear motor: \cite{stankevic17_inter_charac_rotat_stages_x_ray_nanot,engblom18_nanop_resul}
+A more comprehensive review of actively controlled end-stations is provided in Section [\ldots{}].
-\item Voice Coil: \cite{kelly22_delta_robot_long_travel_nano,geraldes23_sapot_carnaub_sirius_lnls}
-\end{itemize}
 
-In the literature, the feedback bandwidth for such end-station is rarely specificity.
-It is usually slow (in the order of 1Hz), so that only (thermal) drifts are compensated.
-Only recently, high bandwidth (100Hz) have been reported with the use of voice coil actuators \cite{kelly22_delta_robot_long_travel_nano,geraldes23_sapot_carnaub_sirius_lnls}.
-
-Two examples of end-station integrating online-metrology and feedback loops are shown in Figure \ref{fig:introduction_active_stations}:
-\begin{itemize}
-\item Figure \ref{fig:introduction_stages_villar}: ID16a beamline at ESRF (short stroke) Piezoelectric hexapod, rotation stage, Online metrology using many capacitive sensors.
-The feedback loop (between the capacitive sensors and the piezoelectric hexapod) is used to compensate for errors of the rotation stage, and also to perform accurate scans with the hexapod.
-\item Figure \ref{fig:introduction_stages_nazaretski}: interferometers are used to measure the position of the sample. multi-layer Laue lenses (MLLs) are used to focus the beam down
-Feedback control is used to compensate for drifts of the positioning stages.
-\end{itemize}
-
-More extensive review of end-station with feedback loops based on online metrology will be given in section [\ldots{}].
 \begin{figure}[htbp]
 \begin{subfigure}{0.49\textwidth}
 \begin{center}
@@ -488,38 +351,18 @@ More extensive review of end-station with feedback loops based on online metrolo
 \caption{\label{fig:introduction_active_stations}Example of two end-stations with real-time position feedback based on an online metrology. (\subref{fig:introduction_stages_villar}) \cite{villar18_nanop_esrf_id16a_nano_imagin_beaml}. (\subref{fig:introduction_stages_nazaretski}) \cite{nazaretski17_desig_perfor_x_ray_scann,nazaretski15_pushin_limit}}
 \end{figure}
 
-For tomography experiments, correcting for guiding errors of the rotation stage is of primary concern.
+For tomography experiments, correcting spindle guiding errors is critical.
-Two approaches can be used:
+Correction stages are typically placed either below the spindle \cite{stankevic17_inter_charac_rotat_stages_x_ray_nanot,holler17_omny_pin_versat_sampl_holder,holler18_omny_tomog_nano_cryo_stage,villar18_nanop_esrf_id16a_nano_imagin_beaml,engblom18_nanop_resul,nazaretski22_new_kirkp_baez_based_scann,xu23_high_nsls_ii} or above it \cite{wang12_autom_marker_full_field_hard,schroer17_ptynam,schropp20_ptynam,geraldes23_sapot_carnaub_sirius_lnls}.
-\begin{itemize}
+In most reported cases, only translational (XYZ) corrections are applied.
-\item Having the stage used for correcting the errors below the Spindle. \cite{stankevic17_inter_charac_rotat_stages_x_ray_nanot,holler17_omny_pin_versat_sampl_holder,holler18_omny_tomog_nano_cryo_stage,villar18_nanop_esrf_id16a_nano_imagin_beaml,engblom18_nanop_resul,nazaretski22_new_kirkp_baez_based_scann,xu23_high_nsls_ii}
+Payload capacities for these high-precision systems are usually limited, typically handling calibrated samples on the micron scale, although capacities up to 500g have been reported \cite{nazaretski22_new_kirkp_baez_based_scann,kelly22_delta_robot_long_travel_nano}.
-\item Having the stage correcting the errors above the Spindle: \cite{wang12_autom_marker_full_field_hard,schroer17_ptynam,schropp20_ptynam,geraldes23_sapot_carnaub_sirius_lnls}
+The system developed in this thesis aims for payload capabilities approximately 100 times heavier (up to 50 kg) than previous stations.
-In all these cases, only XYZ stages are used to compensate for the guiding errors of the spindle.
-\end{itemize}
-
-In terms of payload capabilities:
-\begin{itemize}
-\item All are only supported calibrated, micron scale samples
-\item Higher sample masses to up to 500g have been reported in \cite{nazaretski22_new_kirkp_baez_based_scann,kelly22_delta_robot_long_travel_nano}
-\end{itemize}
-
-100 times heavier payload capabilities than previous stations with similar performances.
 \subsubsection*{Long Stroke - Short Stroke architecture}
 
-As shown in the previous examples, end-stations integrating online-metrology for nano-positioning are typically limited to only few degrees of freedom with only short stroke capabilities (in the order of \(100\,\mu m\)).
+End-stations integrating online metrology for active nano-positioning often exhibit limited operational ranges, typically constrained to a few degrees of freedom with strokes around \(100\,\mu m\).
-
+An alternative strategy involves a ``long stroke-short stroke'' architecture, illustrated conceptually in Figure \ref{fig:introduction_two_stage_schematic}.
-An other strategy, illustrated in Figure \ref{fig:introduction_two_stage_schematic}, is to use two stacked stages for a single DoF:
+In this configuration, a high-accuracy, high-bandwidth short-stroke stage is mounted on top of a less precise long-stroke stage.
-\begin{itemize}
+The short-stroke stage actively compensates for errors based on metrology feedback, while the long-stroke stage provides the coarse, large-range motion.
-\item A long stroke, with limited accuracy is combined with short stroke stage with good dynamical properties.
+This approach allows combining extended travel with high precision and good dynamic response, but is often implemented for only one or a few DoFs, as seen in Figures \ref{fig:introduction_two_stage_control_example} and \ref{fig:introduction_two_stage_control_h_bridge}.
-The short stroke stage is used to position the sample based on the metrology measurement, while the long stroke is performing large motion.
-\end{itemize}
-
-Such strategy is typically limited to few degrees of freedom:
-\begin{itemize}
-\item 1DoF as shown in Figure \ref{fig:introduction_two_stage_control_example}
-\item 3DoF as shown in Figure \ref{fig:introduction_two_stage_control_h_bridge}
-\end{itemize}
-
-With such strategy, it is possible to obtain an overall stage with long stroke capability and with good accuracy and dynamical properties (brought by the short stroke stage).
 
 \begin{figure}[htbp]
 \centering
@@ -543,54 +386,25 @@ With such strategy, it is possible to obtain an overall stage with long stroke c
 \caption{\label{fig:introduction_two_stage_example}(\subref{fig:introduction_two_stage_control_example}) \cite{shinno11_newly_devel_long_range_posit}, (\subref{fig:introduction_two_stage_control_h_bridge}) \cite{schmidt20_desig_high_perfor_mechat_third_revis_edition}}
 \end{figure}
 \chapter{Challenge definition}
-Based on the positioning requirements brought by the 4th light sources, improved focusing optics and development in detector technology, there are several challenges that need to be addressed.
+The advent of fourth-generation light sources, coupled with advancements in focusing optics and detector technology, imposes stringent new requirements on sample positioning systems.
+For the ID31 beamline, the smallest anticipated beam size is approximately 200 nm (horizontal, Dy) by 100 nm (vertical, Dz).
+To effectively utilize such beams, the positioning system must maintain the sample's point of interest within the beam profile throughout the experiment.
+This translates to required peak-to-peak positioning stability better than 200 nm in Dy and 100 nm in Dz, corresponding to RMS values of approximately 30 nm and 15 nm, respectively.
+Furthermore, tilt errors (Ry) must be controlled to below approximately 1.7 µrad peak-to-peak (250 nrad RMS).
 
+Crucially, these specifications must be met even when considering high-frequency vibrations, owing to the use of high-frame-rate detectors.
+These demanding stability requirements must be achieved within the specific context of the ID31 beamline, which necessitates building upon the existing micro-station infrastructure, accommodating a wide range of experimental configurations requiring high mobility, and handling substantial payloads up to 50 kg.
 
-Smallest beam-size foreseen to be used on ID31 is around 200nm x 100nm
+The existing micro-station, despite being composed of high-quality stages, exhibits positioning accuracy limited to approximately \(10\,\mu m\) and \(10\,\mu\text{rad}\) due to inherent factors such as backlash, mechanical play, thermal expansion, imperfect guiding, and vibrations.
-\begin{itemize}
+While individual stage encoders can correct motion along their primary axis, they do not compensate for parasitic motions in other degrees of freedom.
-\item During the experiments, the goal is therefore to keep to point of interest of the sample on the beam
+The primary objective of this project is therefore defined as enhancing the positioning accuracy and stability of the ID31 micro-station by roughly two orders of magnitude, to fully leverage the capabilities offered by the ESRF-EBS source and modern detectors, without compromising its existing mobility and payload capacity.
-\item Therefore, the peak to peak positioning errors should be below 200nm in Dy and 100nm in Dz
-\item RMS errors (/ by 6.6) gives 30nmRMS in Dy and 15nmRMS in Dz.
-\item Also the tilt angle Ry error should be below <1.7urad, 250nrad RMS
-\end{itemize}
-
-
-As high frame rate detectors can be used, the specified position errors of the sample should hold even when taking into account high frequency vibrations.
-
-
-Combined with the specificity of ID31:
-\begin{itemize}
-\item Build on top of the existing micro-station
-\item High required mobility to be able to perform many different experiments
-\item Handle large payloads (up to 50kg)
-\end{itemize}
-
-
-The current micro-station, while being composed of high performance positioning stages, the positioning accuracy is still limited by several effects:
-\begin{itemize}
-\item Backlash, play, thermal expansion, guiding imperfections, \ldots{}
-\item Give some numbers: straightness of the Ty stage for instance, change of \(0.1^oC\) with steel gives x nm of motion
-\item Vibrations
-\item Possibility to have linear/rotary encoders that correct the motion in the considered DoF, but does not change anything to the other 5DoF
-\end{itemize}
-
-Typically, the final position accuracy is around 10um and 10urad.
-
-The goal of this project is therefore to increase the positioning accuracy of the micro-station to fully exploit the new beam and detectors.
 \subsubsection{The Nano Active Stabilization System Concept}
 
-In order to address the new positioning requirements, the concept of the Nano Active Stabilization System (further referred to as the ``NASS'') is proposed.
+To address these challenges, the concept of a Nano Active Stabilization System (NASS) is proposed.
-
+As schematically illustrated in Figure \ref{fig:introduction_nass_concept_schematic}, the NASS comprises four principal components integrated with the existing micro-station (yellow): a 5-DoF online metrology system (red), a 5- or 6-DoF active stabilization platform (blue), and the associated control system and instrumentation (purple).
-It is composed of mainly four elements (Figure \ref{fig:introduction_nass_concept_schematic}):
+This system essentially functions as a high-performance, multi-axis vibration isolation and error correction platform situated between the micro-station and the sample.
-\begin{itemize}
+It actively compensates for positioning errors measured by the external metrology system.
-\item The micro station (in yellow)
+The overarching goal is to improve the effective positioning accuracy from the micro-station's native \(\approx 10\,\mu m\) level down to below \(100\,\text{nm}\), while preserving the full mobility and 50 kg payload capability of the underlying stages.
-\item A 5 degrees of freedom metrology system (in red)
-\item A 5 or 6 degrees of freedom stabilization platform (in blue)
-\item Control system and associated instrumentation (in purple)
-\end{itemize}
-
-It therefore corresponds to a 5 DoF vibration control platform on top of a complex positioning platform that correct positioning errors based on an external metrology.
-That way, the goal is to improve the positioning accuracy of the micro-station from \textasciitilde{}10um to less than 100nm, while keeping the same mobility and payload capabilities.
 
 \begin{figure}[htbp]
 \centering
@@ -599,61 +413,34 @@ That way, the goal is to improve the positioning accuracy of the micro-station f
 \end{figure}
 \subsubsection{Online Metrology system}
 
-As the position of the sample is actively controlled based on the measured position, the accuracy of the NASS depends on the accuracy of the metrology system.
+The performance of the NASS is fundamentally reliant on the accuracy and bandwidth of its online metrology system, as the active control is based directly on these measurements.
-
+This metrology system must fulfill several criteria: measure the sample position in 5 DoF (excluding rotation about the vertical Z-axis); ideally, measure position relative to the X-ray focusing optics; possess a measurement range compatible with the micro-station's extensive mobility and continuous spindle rotation; achieve accuracy commensurate with the sub-100 nm positioning target; and offer high bandwidth for real-time control.
-Such metrology system should:
-\begin{itemize}
-\item Measure the sample's position along 5 DoF (only the rotation along the vertical axis is not measured)
-\item Ideally measure the position with respect to the focusing optics
-\item Long stroke, as the micro-station as high mobility, compatible with the spindle continuous rotation
-\item Have an accuracy compatible with the positioning requirements
-\item High bandwidth
-\end{itemize}
-
-Initial Concept:
-\begin{itemize}
-\item A spherical reflector with flat bottom is fixed just under the sample
-\item The center of the sphere coincide with the focused point of the X-ray
-\item Fiber interferometers are pointed both on spherical surface and on the bottom flat surface.
-\item A tracking system (tip-tilt mechanism) is used to keep the beam perpendicular to the mirror surface: Spherical mirror with center at the point of interest => No Abbe errors
-\end{itemize}
-
-In that case:
-\begin{itemize}
-\item XYZ positions can be measured from at least 3 interferometers pointing at the spherical surface
-\item Rx/Ry angles are measured from at least 3 interferometers pointing at the bottom flat surface
-\end{itemize}
-
-Such metrology system is a complex mechatronics system on its own.
-This metrology system is not further discussed in this thesis as it is still under active development.
-In the following of this thesis, it is supposed that the metrology system is accurate, and high bandwidth.
 
 \begin{figure}[htbp]
 \centering
 \includegraphics[scale=1]{figs/introduction_nass_metrology.png}
 \caption{\label{fig:introduction_nass_metrology}2D representation of the NASS metrology system.}
 \end{figure}
+
+An initial concept, depicted in Figure \ref{fig:introduction_nass_metrology}, involves a spherical reflector with a flat bottom surface fixed beneath the sample.
+The sphere's center is intended to coincide with the X-ray focus.
+Fiber interferometers are directed at both the spherical and flat surfaces.
+A tracking system is needed to maintain interferometer alignment, eliminating Abbe errors by measuring directly relative to the point of interest.
+Translational positions (XYZ) are derived from measurements on the spherical surface, while tilt angles (Rx/Ry) are determined from measurements on the flat bottom surface.
+The development of this complex metrology system constitutes a significant mechatronic project in itself and is currently ongoing; it is not further detailed within this thesis.
+For the work presented herein, the metrology system is assumed to provide accurate, high-bandwidth 5-DoF position measurements.
 \subsubsection{Active Stabilization Platform}
 
-The Active stabilization platform, located in between the sample and the micro-station should:
+The active stabilization platform, positioned between the micro-station top plate and the sample, must satisfy several demanding requirements.
-\begin{itemize}
+It needs to provide active motion compensation in 5 DoF (Dx, Dy, Dz, Rx, Ry).
-\item Be able to move the sample in 5 DoF (the vertical rotation is not controlled)
+It must possess excellent dynamic properties to enable high-bandwidth control capable of suppressing vibrations and tracking desired trajectories with nanometer-level precision.
-\item Have good dynamical properties such that the sample's position can be controlled up to high frequency
+Consequently, it must be free from backlash and play, and its active components (e.g., actuators) should introduce minimal vibrations.
-\item Be capable to control the position down to nanometers.
+Critically, it must reliably support and actuate payloads up to 50 kg.
-It should therefore be free of play, backlash.
-Low level of vibration should be induced by the active parts of the platform (such as actuator noise).
-\item It should accept payloads up to 50kg.
-\end{itemize}
 
-A good candidate for the active platform is the Stewart platform:
+A suitable candidate architecture for this platform is the Stewart platform (or hexapod), a parallel kinematic mechanism capable of 6-DoF motion.
-\begin{itemize}
+Stewart platforms are widely employed in positioning and vibration isolation applications due to their inherent stiffness and potential for high precision.
-\item Parallel architecture, capable of controlling the motion in 6DoF
+Various designs exist, differing in geometry, actuation technology, sensing methods, and control strategies, as exemplified in Figure \ref{fig:introduction_stewart_platform_piezo}.
-\item Very popular for positioning and vibration control applications
+A central challenge addressed in this thesis is the optimal mechatronic design of such an active platform tailored to the specific requirements of the NASS.
-\item Many different designs, in terms of geometry, actuators, sensors and control strategies
-Figure \ref{fig:introduction_stewart_platform_piezo}
-\end{itemize}
-
-\textbf{Challenge}: Optimally designing such active platform
 
 \begin{figure}[htbp]
 \begin{subfigure}{0.49\textwidth}
@@ -672,159 +459,92 @@ Figure \ref{fig:introduction_stewart_platform_piezo}
 \end{figure}
 \subsubsection{MIMO robust control strategies}
 
-The NASS also includes feedback control:
+The NASS inherently involves multi-input, multi-output (MIMO) feedback control.
-\begin{itemize}
+The control system must process position measurements from the online metrology system and reference positions derived from the desired micro-station movements, commanding the active platform in real time to stabilize the sample and compensate for all error sources, including stage imperfections, thermal drifts, and vibrations.
-\item from the measured position of the sample using the online metrology
+Ensuring the stability and robustness of these feedback loops is paramount, especially within the demanding operational context of a synchrotron beamline, which requires reliable 24/7 operation with minimal intervention.
-\item from the wanted position of the sample (based on the wanted motion of each of the micro-station stages)
+This contrasts with many traditional synchrotron instruments built using proven, passively stable components like stepper motors and conventional bearings.
-\item the active platform is controlled in real time to stabilize the sample's position, compensating for all the errors of the micro-station stages, thermal drifts, etc.
-\end{itemize}
 
-When feedback control is being used, attention should be made on the stability of the feedback loop.
+Several factors complicate the design of robust feedback control for the NASS.
-This is especially important in the context of a beamline application, as the instrument should be able to 24/7 with minimum intervention.
+The system must perform reliably across diverse experimental conditions, including different scan types (tomography, linear scans) and velocities (slow drifts to fast fly-scans).
-That is why most of end-stations are based on well-proven design (stepper motors, linear guides, ball bearing, \ldots{}).
+The continuous rotation of the spindle introduces gyroscopic coupling effects and means actuators rotate relative to stationary sensors, altering the system dynamics.
-
+Perhaps the most significant challenge is the wide variation in payload mass, from potentially 1 kg up to 50 kg.
-This need for robust feedback control is there made difficult due to:
+High-performance positioning controllers often assume a fixed, well-characterized payload, as seen in applications like lithography or atomic force microscopy (AFM).
-\begin{itemize}
+Designing for robustness against large payload variations typically necessitates larger stability margins, which can compromise achievable performance.
-\item Many different configurations (tomography, Ty scans, slow fast, \ldots{})
+Furthermore, unlike many systems where the active stage and sample are significantly lighter than the underlying coarse stages, the NASS payload mass can be substantially greater than the mass of the micro-station's top stages.
-\item Rotation aspect, gyroscopic effects, actuators are rotating with respect to the sensors
+This leads to strong dynamic coupling between the active platform and the micro-station structure, resulting in a more complex MIMO system with significant cross-talk between axes.
-\item The variety of payloads that will be used, with masses ranging from 1kg to 50kg.
+These variations in operating conditions and payload translate into significant uncertainty or changes in the plant dynamics that the controller must handle.
-Typically, high performance position feedback controllers are working with calibrated payloads (lithography machines, AFM, \ldots{})
+Therefore, the feedback controller must be designed to be robust against this plant uncertainty while still delivering the required nanometer-level performance.
-Being robust to change of payload inertia means larger stability margins and therefore less performance.
-\item For most of end-stations, the top stages (for small stroke scans) as well as the sample are quite light compared to the long stroke stages.
-This way, the short stroke stage dynamics is not coupled to the dynamics of the stages bellow.
-In the NASS case, the payload's mass may be one order of magnitude heavier than the mass of the long stroke top platform.
-This induce a high coupling between the active platform and the micro-station.
-This there may lead to a MIMO system with more complex dynamics and more coupling.
-\item This translates in change on the plant dynamics.
-The feedback controller therefore need to be robust against plant uncertainty, while providing the wanted level of performance.
-\end{itemize}
 \subsubsection{Predictive Design / Mechatronics approach}
 
-\begin{itemize}
+The overall performance of the NASS will be determined by the interplay of numerous factors, including sensor accuracy and noise, actuator force and bandwidth, mechanical design stiffness and resonances, and the achievable control bandwidth.
-\item The performances of the system will depend on many factors:
+To navigate this complexity and ensure the final system meets its stringent specifications, a predictive design methodology, specifically a mechatronics approach, is essential.
-\begin{itemize}
+The goal is to rigorously evaluate different concepts, predict performance limitations, and guide the design process towards an optimal solution that functions correctly upon first assembly, given the significant cost and complexity involved.
-\item sensors
+Key challenges within this approach include developing appropriate design methodologies, creating accurate simulation models capable of comparing different concepts quantitatively, and converging on a final design that demonstrably achieves the target performance levels.
-\item actuators
-\item mechanical design
-\item achievable bandwidth
-\end{itemize}
-\item Need to evaluate the different concepts, and predict the performances to guide the design
-\item The goal is to design, built and test this system such that it work as expected the first time.
-Very costly system, so must be correct.
-\item \textbf{Challenge}:
-\begin{itemize}
-\item Proper design methodology
-\item Have accurate models to be able to compare different concepts
-\item Converge to a solution that gives the wanted level of performance
-\end{itemize}
-\end{itemize}
 \chapter{Original Contributions}
-In order to address the challenges associated with the development of the Nano Active Stabilization Systems, this thesis proposes several original contributions in the fields of Control, Mechatronics Design and Experimental validation.
+This thesis presents several original contributions aimed at addressing the challenges inherent in the design, control, and implementation of the Nano Active Stabilization System, primarily within the fields of Control Theory, Mechatronics Design, and Experimental Validation.
 \subsubsection{6DoF vibration control of a rotating platform}
 
-Long stroke / short stroke architectures are usually limited to 1DoF or 2DoF.
+While long stroke-short stroke architectures have been implemented for 1-DoF or 2-DoF systems, this work extends the concept to a fully coupled 6-DoF system operating on a continuously rotating base.
-It is here extended to 6DoF.
+The active platform is designed not merely to correct rotational errors but to simultaneously compensate for errors originating from all underlying micro-station stages.
-
+The application of a continuously rotating Stewart platform for active vibration control and error compensation in this manner is believed to be novel in the reviewed literature.
-The active platform will not only compensate for errors of the rotation stage, but also of all other stages.
-
-To the author's knowledge, the use of a continuously rotating stewart platform for vibration control has not been proved in the literature.
 \subsubsection{Mechatronics design approach}
 
-For the design of the NASS, a rigorous mechatronics design approach was conducted.
+A rigorous mechatronics design methodology was applied consistently throughout the NASS development lifecycle \cite{dehaeze18_sampl_stabil_for_tomog_exper,dehaeze21_mechat_approac_devel_nano_activ_stabil_system}.
-
+Although the mechatronics approach itself is not new, its comprehensive application here, from initial concept evaluation using simplified models to detailed design optimization and experimental validation informed by increasingly sophisticated models, is noteworthy.
-\cite{dehaeze18_sampl_stabil_for_tomog_exper,dehaeze21_mechat_approac_devel_nano_activ_stabil_system}
+Dynamical models were employed at every stage: for initial concept selection, detailed component optimization, understanding experimental observations, and optimizing control strategies.
-
+This thesis documents this process chronologically, illustrating how models of varying complexity can be effectively utilized at different project phases and how design decisions were systematically based on quantitative model predictions and analyses.
-While not new, this approach is here applied from start to finish:
+While the resulting system is highly specific, the documented effectiveness of this integrated design approach may contribute to the broader adoption of mechatronics methodologies in the design of future synchrotron instrumentation.
-\begin{itemize}
-\item From first concepts using basic models, to concept validation using mode accurate models
-\item Detailed design phase: models were used to optimize each individual components
-\item Experimental phase: models were still found to have great use.
-For instance to better understand the observed behavior, and also to optimize the implemented control strategy.
-\end{itemize}
-
-The use of dynamical models were used all along the development.
-
-This document, being written chronologically:
-\begin{itemize}
-\item Make clear how each models can be useful during different parts of the project
-\item Clearly show how each design decision are based on facts / clear conclusions extracted from the models
-\item While the developed system is quite specific for the presented application, it shows the effectiveness of this design approach
-\end{itemize}
-
-I hope this document can make a small contribution in the adoption of the mechatronics approach for the design of future end-station and synchrotron instrumentation.
 \subsubsection{Multi-body simulations with reduced order flexible bodies obtained by FEA}
 
-One of the key tool that were used
+A key enabling tool employed extensively in this work was a combined multi-body simulation and Finite Element Analysis technique, specifically utilizing Component Mode Synthesis (CMS) to represent flexible bodies within the multi-body framework \cite{brumund21_multib_simul_reduc_order_flexib_bodies_fea}.
-
+This hybrid approach, while established, was experimentally validated in this work for components critical to the NASS, namely amplified piezoelectric actuators and flexible joints.
-Combined multi-body / FEA techniques and experimental validation on a Stewart platform containing amplified piezoelectric actuators
+It proved invaluable for designing and optimizing components intended for integration into a larger, complex dynamic system.
-Super-element of amplified piezoelectric actuator / combined multibody-FEA technique, experimental validation on an amplified piezoelectric actuator and further validated on a complete stewart platform
+This methodology, detailed in Section [\ldots{}], is presented as a potentially useful tool for future mechatronic instrument development.
-
-While not new:
-\begin{itemize}
-\item Experimentally validated with both an amplified piezoelectric actuator as well as a flexible joint
-\item It proved to be a very useful tool for the design/optimisation of components that have to be integrated in a larger system
-\item Believed to be quite useful for the development of future mechatronics instrumentation
-\end{itemize}
-
-Subject of one publication \cite{brumund21_multib_simul_reduc_order_flexib_bodies_fea}
-Further detailed in Section [\ldots{}].
 \subsubsection{Control Robustness by design}
 
-One of the main challenge is to design a system that is robust for all the experimental conditions:
+Addressing the critical challenge of robustness across varying experimental conditions (rotation speeds, payloads up to 50 kg) was approached through ``robustness by design'' rather than relying solely on complex robust control synthesis techniques (like \(\mathcal{H}_\infty\) or \(\mu\text{-synthesis}\)).
-\begin{itemize}
+The strategy involved selecting a system architecture (mechanics, sensors, actuators) inherently conducive to robust control.
-\item various rotational velocities used
+An example is the deliberate use of collocated actuator/sensor pairs, enabling the potential application of passivity-based control principles to guarantee stability.
-\item payload used can weight up to 50kg
+Informed architectural choices were made by systematically evaluating different sensor combination strategies (e.g., HAC/LAC, sensor fusion, two-sensor control) and comparing various MIMO decoupling approaches.
-\end{itemize}
+This comparative analysis of control architectures, presented in Section [\ldots{}], was identified as somewhat lacking in existing literature.
-
-Instead of relying on complex controller synthesis (such as \(\mathcal{H}_\infty\) synthesis or \(\mu\text{-synthesis}\)) to guarantee the robustness and performance, the approach was to:
-\begin{itemize}
-\item Choose an adequate architecture (mechanics, sensors, actuators) such that controllers are robust by nature
-\item An example is the use of collocated actuator/sensor pairs, such that controller stability can be guaranteed using passivity principles
-\item To make informed choices on the chosen architecture:
-\begin{itemize}
-\item different ways to combine sensors (HAC-LAC, sensors fusion, two sensor control) were evaluated
-\item different decoupling strategy were compared
-\end{itemize}
-Such discussion, presented in Section [\ldots{}] ,were found to be lacking in the literature.
-\end{itemize}
 \subsubsection{Active Damping of rotating mechanical systems using Integral Force Feedback}
 
-During the conceptual design, it was found the guaranteed stability of the active damping technique called ``Integral Force Feedback'' (IFF), is lost for rotating platforms as is the case for the NASS.
+During conceptual design, it was found that the guaranteed stability properties of the established active damping technique known as Integral Force Feedback (IFF) are compromised when applied to rotating platforms like the NASS.
-
+To address this instability issue, two modifications to the classical IFF control scheme were proposed and analyzed.
-To overcome this issue, two modifications of the classical IFF control scheme are proposed.
+The first involves a minor adjustment to the control law itself, while the second incorporates physical springs in parallel with the force sensors.
-The first consists of slightly modifying the control law while the second consists of adding springs in parallel with the force sensors.
+Stability conditions and optimal parameter tuning guidelines were derived for both modified schemes.
-Conditions for stability and optimal parameters are derived.
+This is further discussed in Section [\ldots{}] and was the subject of publications  \cite{dehaeze20_activ_dampin_rotat_platf_integ_force_feedb,dehaeze21_activ_dampin_rotat_platf_using}.
-
-\cite{dehaeze20_activ_dampin_rotat_platf_integ_force_feedb,dehaeze21_activ_dampin_rotat_platf_using}
 \subsubsection{Design of complementary filters using \(\mathcal{H}_\infty\) Synthesis}
 
-One way to combine sensors is to use ``sensor fusion''.
+For implementing sensor fusion, where signals from multiple sensors are combined, complementary filters are often employed.
-In such case, complementary filters are used to filter and combine the sensors.
+A novel method for designing these filters using \(\mathcal{H}_\infty\) synthesis techniques was developed \cite{dehaeze19_compl_filter_shapin_using_synth}.
-
+This method allows explicit shaping of the filter norms, providing guarantees on the performance of the sensor fusion process.
-A method for designing such filter is proposed \cite{dehaeze19_compl_filter_shapin_using_synth}, that allows to shape the complementary filters norm, which allows to guarantee the performance of the fusion.
+This design strategy, discussed further in Section [\ldots{}], has subsequently found application in optimizing sensor fusion for gravitational wave detectors \cite{tsang22_optim_sensor_fusion_method_activ}.
-This was latter applied for optimal sensor fusion in gravitational wave detectors \cite{tsang22_optim_sensor_fusion_method_activ}.
+The integration of such filters into feedback control architectures can also lead to advantageous control structures, as proposed in \cite{verma20_virtual_sensor_fusion_high_precis_contr} and further studied in Section [\ldots{}].
-The design strategy is discussed in Section [\ldots{}].
-The use of such complementary filters for feedback control can also lead to interesting control architecture, as discussed in \cite{verma20_virtual_sensor_fusion_high_precis_contr} and further developed in Section [\ldots{}].
 \subsubsection{Experimental validation of the Nano Active Stabilization System}
 
-The positioning performances of the Nano Active Stabilization System is experimentally evaluated/demonstrated on the ID31 beamline.
+The conclusion of this work involved the experimental implementation and validation of the complete NASS on the ID31 beamline.
-
+Experimental results demonstrate that the system successfully improves the effective positioning accuracy of the micro-station from its native \textasciitilde{}10 µm level down to the target \textasciitilde{}100 nm range during representative scientific experiments.
-The positioning accuracy of the micro-station is effectively improved from the \textasciitilde{}10um down to \textasciitilde{}100nm while performing experiments.
+Crucially, robustness to variations in sample mass (up to 39 kg tested) and diverse experimental conditions (e.g., tomography scans) was verified.
-Robustness to sample's mass, and different experimental conditions are also verified.
+The NASS thus provides a versatile end-station solution, uniquely combining high payload capacity with nanometer-level accuracy and stability, enabling optimal utilization of the advanced capabilities of the ESRF-EBS beam and associated detectors.
-
+To the author's knowledge, this represents the first demonstration of such a 5-DoF active stabilization platform being used to enhance the accuracy of a complex positioning system to this level.
-This therefore lead to a very versatile end-station, with high payload capabilities and nano-meter accuracy, allowing for full exploitation of the x-ray beam and associated instrumentation.
-
-To the author's knowledge, this is the first time such active platform is used to improve the accuracy of a positioning stage in 5DoF.
 \chapter{Thesis Outline - Mechatronics Design Approach}
-This thesis is organized:
+This thesis is structured chronologically, mirroring the phases of the mechatronics development approach employed for the NASS project.
-\begin{itemize}
+It is divided into three chapters, each corresponding to a distinct phase of this methodology: Conceptual Design, Detailed Design, and Experimental Validation.
-\item to follow the mechatronics development approach, i.e. it is chronologically written.
+A brief overview of each chapter's content, is provided below.
-\end{itemize}
-
-The three chapters corresponds to the three mains parts of the proposed mechatronics approach.
-A brief overview of these three chapters is given bellow.
 \subsubsection{Conceptual design development}
 
+
+
+
+
+
+
+
+
+
+
+
 \begin{itemize}
 \item Talk about dynamic error budgeting
 \item Talk about used model

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