From 1763a4bdca61c1113aad8b935d9fd938dcf2a278 Mon Sep 17 00:00:00 2001 From: Thomas Dehaeze Date: Sun, 20 Apr 2025 10:39:35 +0200 Subject: [PATCH] Christophe's review of introduction --- phd-thesis.org | 52 ++++++++++++++++++++++++-------------------------- 1 file changed, 25 insertions(+), 27 deletions(-) diff --git a/phd-thesis.org b/phd-thesis.org index 0adc9d8..0fa63bb 100644 --- a/phd-thesis.org +++ b/phd-thesis.org @@ -119,7 +119,6 @@ | frf | FRF | Frequency Response Function | | iff | IFF | Integral Force Feedback | | rdc | RDC | Relative Damping Control | -| drga | DRGA | Dynamical Relative Gain Array | | rga | RGA | Relative Gain Array | | hpf | HPF | high-pass filter | | lpf | LPF | low-pass filter | @@ -323,10 +322,10 @@ This global distribution of such facilities underscores the significant utility #+attr_latex: :options [h!tbp] [[file:figs/introduction_synchrotrons.png]] -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. +These facilities fundamentally comprise two main parts: the accelerator and storage ring, where electron acceleration and light generation occur, and the beamlines, where the intense X-ray beams are conditioned and directed for experimental use. The European Synchrotron Radiation Facility (ESRF), shown in Figure\nbsp{}ref:fig:introduction_esrf_picture, is a joint research institution supported by 19 member countries. -The ESRF commenced user operations in 1994 as the world's first third-generation synchrotron. +The ESRF started user operations in 1994 as the world's first third-generation synchrotron. Its accelerator complex, schematically depicted in Figure\nbsp{}ref:fig:introduction_esrf_schematic, includes a linear accelerator where electrons are initially generated and accelerated, a booster synchrotron to further accelerate the electrons, and an 844-meter circumference storage ring where electrons are maintained in a stable orbit. Synchrotron light are emitted in more than 40 beamlines surrounding the storage ring, each having specialized experimental stations. @@ -395,7 +394,7 @@ These components are housed in multiple Optical Hutches, as depicted in Figure\n #+end_subfigure #+end_figure -Following the optical hutches, the conditioned beam enters the Experimental Hutch (Figure\nbsp{}ref:fig:introduction_id31_cad), where, for experiments pertinent to this work, focusing optics are utilized. +Following the optical hutches, the conditioned beam enters the Experimental Hutch (Figure\nbsp{}ref:fig:introduction_id31_cad), where, for experiments pertinent to this work, focusing optics are used. The sample is mounted on a positioning stage, referred to as the "end-station", that enables precise alignment relative to the X-ray beam. Detectors are used to capture the X-rays transmitted through or scattered by the sample. 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. @@ -403,7 +402,7 @@ Throughout this thesis, the standard ESRF coordinate system is adopted, wherein The specific end-station employed on the ID31 beamline is designated the "micro-station". As depicted in Figure\nbsp{}ref:fig:introduction_micro_station_dof, it comprises a stack of positioning stages: a translation stage (in blue), a tilt stage (in red), a spindle for continuous rotation (in yellow), and a micro-hexapod (in purple). The sample itself (cyan), potentially housed within complex sample environments (e.g., for high pressure or extreme temperatures), is mounted on top of this assembly. -Each stage serves distinct positioning functions; for example, the micro-hexapod enables fine static adjustments, while the $T_y$ translation and $R_z$ rotation stages are utilized for specific scanning applications. +Each stage serves distinct positioning functions; for example, the micro-hexapod enables fine static adjustments, while the $T_y$ translation and $R_z$ rotation stages are used for specific scanning applications. #+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 micro-station with associated degrees of freedom (\subref{fig:introduction_micro_station_dof}). @@ -478,7 +477,7 @@ Other advanced imaging modalities practiced on ID31 include reflectivity, diffra :UNNUMBERED: t :END: -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. +Continuous progress 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\nbsp{}ref:fig:introduction_beam_3rd_4th_gen. #+name: fig:introduction_beam_3rd_4th_gen @@ -546,7 +545,7 @@ With higher X-ray flux and reduced detector noise, integration times can now be This reduction in integration time has two major implications for positioning requirements. Firstly, for a given spatial sampling ("pixel size"), faster integration necessitates proportionally higher scanning velocities. Secondly, the shorter integration times make the measurements more susceptible to high-frequency vibrations. -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. +Therefore, not only the sample position must be stable against long-term drifts, but it must also be actively controlled to minimize vibrations, especially during dynamic fly-scan acquisitions. **** Existing Nano Positioning End-Stations :PROPERTIES: @@ -610,11 +609,11 @@ The concept of using an external metrology to measure and potentially correct fo 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, providing an indirect measurement. -This measured position can be utilized in several ways: for post-processing correction of acquired data; for calibration routines to compensate for repeatable errors; or, most relevantly here, for real-time feedback control. +This measured position can be used in several ways: for post-processing correction of acquired data; for calibration routines to compensate for repeatable errors; or, most relevantly here, for real-time feedback control. Various sensor technologies have been employed, with capacitive sensors\nbsp{}[[cite:&schroer17_ptynam;&villar18_nanop_esrf_id16a_nano_imagin_beaml;&schropp20_ptynam]] and, increasingly, fiber-based interferometers\nbsp{}[[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. Two examples illustrating the integration of online metrology are presented in Figure\nbsp{}ref:fig:introduction_metrology_stations. -The system at NSLS X8C (Figure\nbsp{}ref:fig:introduction_stages_wang) utilized capacitive sensors for rotation stage calibration and image alignment during tomography post-processing\nbsp{}[[cite:&wang12_autom_marker_full_field_hard]]. +The system at NSLS X8C (Figure\nbsp{}ref:fig:introduction_stages_wang) used capacitive sensors for rotation stage calibration and image alignment during tomography post-processing\nbsp{}[[cite:&wang12_autom_marker_full_field_hard]]. The PtiNAMi microscope at DESY P06 (Figure\nbsp{}ref:fig:introduction_stages_schroer) employs interferometers directed at a spherical target below the sample for position monitoring during tomography, with plans for future feedback loop implementation\nbsp{}[[cite:&schropp20_ptynam]]. #+name: fig:introduction_metrology_stations @@ -706,7 +705,7 @@ Given the high frame rates of modern detectors, these specified positioning erro These demanding stability requirements must be achieved within the specific context of the ID31 beamline, which necessitates the integration with the existing micro-station, accommodating a wide range of experimental configurations requiring high mobility, and handling substantial payloads up to 50 kg. -The existing micro-station, despite being composed of high-performance 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. +The existing micro-station, despite being composed of high-performance stages, exhibits positioning accuracy limited to approximately $10\,\mu m$ and $10\,\mu\text{rad}$ due to inherent factors such as backlash, thermal expansion, imperfect guiding, and vibrations. 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. @@ -790,17 +789,17 @@ This leads to strong dynamic coupling between the active platform and the micro- These variations in operating conditions and payload translate into significant uncertainty or changes in the plant dynamics that the controller must handle. Therefore, the feedback controller must be designed to be robust against this plant uncertainty while still delivering the required nanometer-level performance. -***** Predictive Design / Mechatronics approach +***** Predictive Design The overall performance achieved by the NASS is determined by numerous factors, such as external disturbances, the noise characteristics of the instrumentation, the dynamics resulting from the chosen mechanical architecture, and the achievable bandwidth dictated by the control architecture. -Ensuring the final system met its stringent specifications requires the implementation of a predictive design methodology, also known as a mechatronics design approach. +Ensuring the final system meets its stringent specifications requires the implementation of a predictive design methodology, also known as a mechatronic design approach. The goal is to rigorously evaluate different concepts, predict performance limitations, and guide the design process. Key challenges within this approach include developing appropriate design methodologies, creating accurate models capable of comparing different concepts quantitatively, and converging on a final design that achieves the target performance levels. ** Original Contributions ***** Introduction :ignore: -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. +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, Mechatronic Design, and Experimental Validation. ***** 6DoF vibration control of a rotating platform @@ -808,14 +807,14 @@ Traditional long-stroke/short-stroke architectures typically operate in one or t This work extends the concept to six degrees of freedom, with the active platform designed not only 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. -***** Mechatronics design approach +***** Mechatronic design approach -A rigorous mechatronics design methodology was applied consistently throughout the NASS development lifecycle\nbsp{}[[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, potentially offers useful insights to the existing literature. -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 the resulting system is highly specific, the documented effectiveness of this design approach may contribute to the broader adoption of mechatronics methodologies in the design of future synchrotron instrumentation. +A rigorous mechatronic design methodology was applied consistently throughout the NASS development life-cycle\nbsp{}[[cite:&dehaeze18_sampl_stabil_for_tomog_exper;&dehaeze21_mechat_approac_devel_nano_activ_stabil_system]]. +Although the mechatronic 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, potentially offers useful insights to the existing literature. +This thesis documents this process chronologically, illustrating how models of varying complexity can be effectively used at different project phases and how design decisions were systematically based on quantitative model predictions and analyses. +While the resulting system is highly specific, the documented effectiveness of this design approach may contribute to the broader adoption of mechatronic methodologies in the design of future synchrotron instrumentation. -***** Multi-body simulations with reduced order flexible bodies obtained by FEA +***** Experimental validation of multi-body simulations with reduced order flexible bodies obtained by FEA A key tool employed extensively in this work was a combined multi-body simulation and Finite Element Analysis technique, specifically utilizing Component Mode Synthesis to represent flexible bodies within the multi-body framework\nbsp{}[[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. @@ -857,8 +856,7 @@ To the author's knowledge, this represents the first demonstration of such a 5-D ** Outline ***** Introduction :ignore: -This thesis is structured chronologically, mirroring the phases of the mechatronics development approach employed for the NASS project. -It is divided into three chapters, each corresponding to a distinct phase of this methodology: Conceptual Design, Detailed Design, and Experimental Validation. +This is divided into three chapters, each corresponding to a distinct phase of this methodology: Conceptual Design, Detailed Design, and Experimental Validation. While the chapters follow this logical progression, care has been taken to structure each chapter such that its constitutive sections may also be consulted independently based on the reader's specific interests. ***** Conceptual design development @@ -3259,9 +3257,9 @@ Finally, an /acquisition system/[fn:modal_3] (figure\nbsp{}ref:fig:modal_oros) i <> To obtain meaningful results, the modal analysis of the micro-station is performed /in-situ/. -To do so, all the micro-station stage controllers are turned "ON". +To do so, all the micro-station stage controllers are turned on. This is especially important for stages for which the stiffness is provided by local feedback control, such as the air bearing spindle, and the translation stage. -If these local feedback controls were turned OFF, this would have resulted in very low-frequency modes that were difficult to measure in practice, and it would also have led to decoupled dynamics, which would not be the case in practice. +If these local feedback controls were turned off, this would have resulted in very low-frequency modes that were difficult to measure in practice, and it would also have led to decoupled dynamics, which would not be the case in practice. The top part representing the active stabilization stage was disassembled as the active stabilization stage will be added in the multi-body model afterwards. @@ -6142,7 +6140,7 @@ As anticipated by the control analysis, some performance degradation was observe :END: Following the validation of the Nano Active Stabilization System concept in the previous chapter through simulated tomography experiments, this chapter addresses the refinement of the preliminary conceptual model into an optimized implementation. -The initial validation utilized a nano-hexapod with arbitrary geometry, where components such as flexible joints and actuators were modeled as ideal elements, employing simplified control strategies without consideration for instrumentation noise. +The initial validation used a nano-hexapod with arbitrary geometry, where components such as flexible joints and actuators were modeled as ideal elements, employing simplified control strategies without consideration for instrumentation noise. This detailed design phase aims to optimize each component while ensuring none will limit the system's overall performance. This chapter begins by determining the optimal geometric configuration for the nano-hexapod (Section\nbsp{}ref:sec:detail_kinematics). @@ -9454,7 +9452,7 @@ Each instrument is characterized individually, measuring actual noise levels and The measured noise characteristics are then incorporated into the multi-body model to confirm that the combined effect of all instrumentation noise sources remains within acceptable limits. #+name: fig:detail_instrumentation_plant -#+caption: Block diagram of the NASS with considered instrumentation. The RT controller is a Speedgoat machine. +#+caption: Block diagram of the NASS with considered instrumentation. The real time controller is a Speedgoat machine. #+attr_latex: :width 0.9\linewidth [[file:figs/detail_instrumentation_plant.png]] @@ -10824,7 +10822,7 @@ It serves several functions, as shown in Figure\nbsp{}ref:fig:test_joints_iso, s #+caption: Geometry of the optimized flexible joints #+attr_latex: :options [htbp] #+begin_figure -#+attr_latex: :caption \subcaption{\label{fig:test_joints_iso}ISO view} +#+attr_latex: :caption \subcaption{\label{fig:test_joints_iso}Isometric view} #+attr_latex: :options {0.38\textwidth} #+begin_subfigure #+attr_latex: :scale 1 @@ -12301,7 +12299,7 @@ At higher frequencies, no resonances can be observed in the model, as the top pl <> Another desired feature of the model is that it effectively represents coupling in the system, as this is often the limiting factor for the control of MIMO systems. -Instead of comparing the full 36 elements of the $6 \times 6$ FFR matrix from $\bm{u}$ to $\bm{d}_e$, only the first "column" is compared (Figure\nbsp{}ref:fig:test_nhexa_comp_simscape_de_all), which corresponds to the transfer function from the command $u_1$ to the six measured encoder displacements $d_{e1}$ to $d_{e6}$. +Instead of comparing the full 36 elements of the $6 \times 6$ FRF matrix from $\bm{u}$ to $\bm{d}_e$, only the first "column" is compared (Figure\nbsp{}ref:fig:test_nhexa_comp_simscape_de_all), which corresponds to the transfer function from the command $u_1$ to the six measured encoder displacements $d_{e1}$ to $d_{e6}$. It can be seen that the coupling in the model matches the measurements well up to the first un-modeled flexible mode at 237Hz. Similar results are observed for all other coupling terms and for the transfer function from $\bm{u}$ to $\bm{V}_s$.