Add matlab file names
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@@ -1,3 +1,7 @@
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% Matlab Init :noexport:ignore:
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%% test_id31_1_metrology.m
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%% Clear Workspace and Close figures
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clear; close all; clc;
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@@ -33,10 +37,10 @@ specs_ry_rms = 0.25; % [urad RMS]
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% Metrology Kinematics
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% <<ssec:test_id31_metrology_kinematics>>
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% The developed short-stroke metrology system is schematically shown in Figure ref:fig:test_id31_metrology_kinematics.
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% The proposed short-stroke metrology system is schematized in Figure ref:fig:test_id31_metrology_kinematics.
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% The point of interest is indicated by the blue frame $\{B\}$, which is located $H = 150\,mm$ above the nano-hexapod's top platform.
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% The spheres have a diameter $d = 25.4\,mm$, and indicated dimensions are $l_1 = 60\,mm$ and $l_2 = 16.2\,mm$.
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% In order to compute the pose of the $\{B\}$ frame with respect to the granite (i.e. with respect to the fixed interferometer heads), the measured (small) displacements $[d_1,\ d_2,\ d_3,\ d_4,\ d_5]$ by the interferometers are first written as a function of the (small) linear and angular motion of the $\{B\}$ frame $[D_x,\ D_y,\ D_z,\ R_x,\ R_y]$ eqref:eq:test_id31_metrology_kinematics.
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% The spheres have a diameter $d = 25.4\,mm$, and the indicated dimensions are $l_1 = 60\,mm$ and $l_2 = 16.2\,mm$.
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% To compute the pose of the $\{B\}$ frame with respect to the granite (i.e. with respect to the fixed interferometer heads), the measured (small) displacements $[d_1,\ d_2,\ d_3,\ d_4,\ d_5]$ by the interferometers are first written as a function of the (small) linear and angular motion of the $\{B\}$ frame $[D_x,\ D_y,\ D_z,\ R_x,\ R_y]$ eqref:eq:test_id31_metrology_kinematics.
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% \begin{equation}\label{eq:test_id31_metrology_kinematics}
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% d_1 = D_y - l_2 R_x, \quad d_2 = D_y + l_1 R_x, \quad d_3 = -D_x - l_2 R_y, \quad d_4 = -D_x + l_1 R_y, \quad d_5 = -D_z
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@@ -45,7 +49,7 @@ specs_ry_rms = 0.25; % [urad RMS]
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% #+attr_latex: :options [b]{0.48\linewidth}
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% #+begin_minipage
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% #+name: fig:test_id31_metrology_kinematics
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% #+caption: Schematic of the measurement system. Measured distances are indicated by red arrows.
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% #+caption: Schematic of the measurement system. The measured distances are indicated by red arrows.
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% #+attr_latex: :scale 1 :float nil
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% [[file:figs/test_id31_metrology_kinematics.png]]
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% #+end_minipage
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@@ -58,7 +62,7 @@ specs_ry_rms = 0.25; % [urad RMS]
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% [[file:figs/test_id31_align_top_sphere_comparators.jpg]]
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% #+end_minipage
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% The five equations eqref:eq:test_id31_metrology_kinematics can be written in a matrix form, and then inverted to have the pose of the $\{B\}$ frame as a linear combination of the measured five distances by the interferometers eqref:eq:test_id31_metrology_kinematics_inverse.
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% The five equations eqref:eq:test_id31_metrology_kinematics can be written in matrix form, and then inverted to have the pose of the $\{B\}$ frame as a linear combination of the measured five distances by the interferometers eqref:eq:test_id31_metrology_kinematics_inverse.
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% \begin{equation}\label{eq:test_id31_metrology_kinematics_inverse}
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% \begin{bmatrix}
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@@ -90,16 +94,16 @@ Hm = [ 0 1 0 -l2 0;
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% Fine Alignment of reference spheres using interferometers
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% <<ssec:test_id31_metrology_sphere_fine_alignment>>
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% Thanks to the first alignment of the two reference spheres with the spindle axis (Section ref:ssec:test_id31_metrology_sphere_rought_alignment) and to the fine adjustment of the interferometers orientations (Section ref:ssec:test_id31_metrology_alignment), the spindle can perform complete rotations while still having interference for all five interferometers.
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% This metrology can therefore be used to better align the axis defined by the two spheres' center with the spindle axis.
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% Thanks to the first alignment of the two reference spheres with the spindle axis (Section ref:ssec:test_id31_metrology_sphere_rought_alignment) and to the fine adjustment of the interferometer orientations (Section ref:ssec:test_id31_metrology_alignment), the spindle can perform complete rotations while still having interference for all five interferometers.
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% Therefore, this metrology can be used to better align the axis defined by the centers of the two spheres with the spindle axis.
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% The alignment process is made by few iterations.
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% First, the spindle is scanned and the alignment errors are recorded.
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% The alignment process requires few iterations.
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% First, the spindle is scanned, and alignment errors are recorded.
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% From the errors, the motion of the micro-hexapod to better align the spheres with the spindle axis is computed and the micro-hexapod is positioned accordingly.
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% Then, the spindle is scanned again, and the new alignment errors are recorded.
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% Then, the spindle is scanned again, and new alignment errors are recorded.
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% This iterative process is first performed for angular errors (Figure ref:fig:test_id31_metrology_align_rx_ry) and then for lateral errors (Figure ref:fig:test_id31_metrology_align_dx_dy).
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% The remaining errors after alignment is in the order of $\pm5\,\mu\text{rad}$ in $R_x$ and $R_y$ orientations, $\pm 1\,\mu m$ in $D_x$ and $D_y$ directions and less than $0.1\,\mu m$ vertically.
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% The remaining errors after alignment are in the order of $\pm5\,\mu\text{rad}$ in $R_x$ and $R_y$ orientations, $\pm 1\,\mu m$ in $D_x$ and $D_y$ directions, and less than $0.1\,\mu m$ vertically.
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%% Angular alignment
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@@ -167,9 +171,9 @@ ylim([-8, 14]);
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% Estimated measurement volume
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% <<ssec:test_id31_metrology_acceptance>>
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% Because the interferometers are pointing to spheres and not flat surfaces, the lateral acceptance is limited.
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% In order to estimate the metrology acceptance, the micro-hexapod is used to perform three accurate scans of $\pm 1\,mm$, respectively along the $x$, $y$ and $z$ axes.
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% During these scans, the 5 interferometers are recorded individually, and the ranges in which each interferometer has enough coupling efficiency to be able to measure the displacement are estimated.
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% Because the interferometers point to spheres and not flat surfaces, the lateral acceptance is limited.
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% To estimate the metrology acceptance, the micro-hexapod was used to perform three accurate scans of $\pm 1\,mm$, respectively along the $x$, $y$ and $z$ axes.
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% During these scans, the 5 interferometers are recorded individually, and the ranges in which each interferometer had enough coupling efficiency to be able to measure the displacement were estimated.
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% Results are summarized in Table ref:tab:test_id31_metrology_acceptance.
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% The obtained lateral acceptance for pure displacements in any direction is estimated to be around $+/-0.5\,mm$, which is enough for the current application as it is well above the micro-station errors to be actively corrected by the NASS.
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@@ -228,25 +232,25 @@ end
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% Estimated measurement errors
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% <<ssec:test_id31_metrology_errors>>
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% When using the NASS, the accuracy of the sample's positioning is determined by the accuracy of the external metrology.
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% However, the validation of the nano-hexapod, the associated instrumentation and the control architecture is independent of the accuracy of the metrology system.
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% When using the NASS, the accuracy of the sample positioning is determined by the accuracy of the external metrology.
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% However, the validation of the nano-hexapod, the associated instrumentation, and the control architecture is independent of the accuracy of the metrology system.
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% Only the bandwidth and noise characteristics of the external metrology are important.
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% Yet, some elements effecting the accuracy of the metrology are discussed here.
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% However, some elements that affect the accuracy of the metrology system are discussed here.
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% First, the "metrology kinematics" (discussed in Section ref:ssec:test_id31_metrology_kinematics) is only approximate (i.e. valid for very small displacements).
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% First, the "metrology kinematics" (discussed in Section ref:ssec:test_id31_metrology_kinematics) is only approximate (i.e. valid for small displacements).
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% This can be easily seen when performing lateral $[D_x,\,D_y]$ scans using the micro-hexapod while recording the vertical interferometer (Figure ref:fig:test_id31_xy_map_sphere).
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% As the interferometer is pointing to a sphere and not to a plane, lateral motion of the sphere is seen as a vertical motion by the top interferometer.
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% As the top interferometer points to a sphere and not to a plane, lateral motion of the sphere is seen as a vertical motion by the top interferometer.
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% Then, the reference spheres have some deviations with respect to an ideal sphere [fn:6].
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% They are initially meant to be used with capacitive sensors which are integrating the shape errors over large surfaces.
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% Then, the reference spheres have some deviations relative to an ideal sphere [fn:test_id31_6].
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% These sphere are originally intended for use with capacitive sensors that integrate shape errors over large surfaces.
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% When using interferometers, the size of the "light spot" on the sphere surface is a circle with a diameter approximately equal to $50\,\mu m$, and therefore the measurement is more sensitive to shape errors with small features.
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% As the light from the interferometer is travelling through air (as opposed to being in vacuum), the measured distance is sensitive to any variation in the refractive index of the air.
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% Therefore, any variation of air temperature, pressure or humidity will induce measurement errors.
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% For instance, for a measurement length of $40\,mm$, a temperature variation of $0.1\,{}^oC$ (which is typical for the ID31 experimental hutch) induces an errors in the distance measurement of $\approx 4\,nm$.
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% As the light from the interferometer travels through air (as opposed to being in vacuum), the measured distance is sensitive to any variation in the refractive index of the air.
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% Therefore, any variation in air temperature, pressure or humidity will induce measurement errors.
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% For instance, for a measurement length of $40\,mm$, a temperature variation of $0.1\,{}^oC$ (which is typical for the ID31 experimental hutch) induces errors in the distance measurement of $\approx 4\,nm$.
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% Interferometers are also affected by noise [[cite:&watchi18_review_compac_inter]].
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% The effect of the noise on the translation and rotation measurements is estimated in Figure ref:fig:test_id31_interf_noise.
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% The effect of noise on the translation and rotation measurements is estimated in Figure ref:fig:test_id31_interf_noise.
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%% Interferometer noise estimation
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