Add CAD view of the bench

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Thomas Dehaeze 2021-02-16 21:24:22 +01:00
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commit 77f2339a9d
9 changed files with 579 additions and 78 deletions

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"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en">
<head>
<!-- 2021-02-16 mar. 19:15 -->
<!-- 2021-02-16 mar. 21:23 -->
<meta http-equiv="Content-Type" content="text/html;charset=utf-8" />
<title>Flexible Joint - Test Bench</title>
<meta name="generator" content="Org mode" />
@ -39,27 +39,28 @@
<h2>Table of Contents</h2>
<div id="text-table-of-contents">
<ul>
<li><a href="#org108197d">1. Flexible Joints - Requirements</a></li>
<li><a href="#org0e51a3c">2. Test Bench Description</a>
<li><a href="#org7706130">1. Flexible Joints - Requirements</a></li>
<li><a href="#org2925cfa">2. Test Bench Description</a>
<ul>
<li><a href="#orgd387cac">2.1. Flexible joint Geometry</a></li>
<li><a href="#org8da94ef">2.2. Required external applied force</a></li>
<li><a href="#orgdda06ee">2.3. Required actuator stroke and sensors range</a></li>
<li><a href="#orgb6763c2">2.4. First try with the APA95ML</a></li>
<li><a href="#orge3df316">2.5. Test Bench</a></li>
<li><a href="#org1121b59">2.1. Flexible joint Geometry</a></li>
<li><a href="#org8e5eddc">2.2. Required external applied force</a></li>
<li><a href="#org5baf14d">2.3. Required actuator stroke and sensors range</a></li>
<li><a href="#orge82143e">2.4. First try with the APA95ML</a></li>
<li><a href="#orgfd806d9">2.5. Test Bench</a></li>
</ul>
</li>
<li><a href="#orgb94416f">3. Agreement between the probe and the encoder</a>
<li><a href="#org169b47f">3. Agreement between the probe and the encoder</a>
<ul>
<li><a href="#org57bb37e">3.1. Results</a></li>
<li><a href="#org5ed49b7">3.1. Setup</a></li>
<li><a href="#orga83f29f">3.2. Results</a></li>
</ul>
</li>
<li><a href="#orgaca8c01">4. Measurement of the Millimar 1318 probe stiffness</a>
<li><a href="#org0fbb329">4. Measurement of the Millimar 1318 probe stiffness</a>
<ul>
<li><a href="#org837827a">4.1. Results</a></li>
<li><a href="#orgc7d7173">4.1. Results</a></li>
</ul>
</li>
<li><a href="#orgac55925">5. Experimental measurement</a></li>
<li><a href="#orgda9e689">5. Experimental measurement</a></li>
</ul>
</div>
</div>
@ -67,8 +68,8 @@
<p>This report is also available as a <a href="./test-bench-flexible-joints.pdf">pdf</a>.</p>
<hr>
<div id="outline-container-org108197d" class="outline-2">
<h2 id="org108197d"><span class="section-number-2">1</span> Flexible Joints - Requirements</h2>
<div id="outline-container-org7706130" class="outline-2">
<h2 id="org7706130"><span class="section-number-2">1</span> Flexible Joints - Requirements</h2>
<div class="outline-text-2" id="text-1">
<table border="2" cellspacing="0" cellpadding="6" rules="groups" frame="hsides">
@ -119,8 +120,8 @@
</div>
</div>
<div id="outline-container-org0e51a3c" class="outline-2">
<h2 id="org0e51a3c"><span class="section-number-2">2</span> Test Bench Description</h2>
<div id="outline-container-org2925cfa" class="outline-2">
<h2 id="org2925cfa"><span class="section-number-2">2</span> Test Bench Description</h2>
<div class="outline-text-2" id="text-2">
<p>
The main characteristic of the flexible joint that we want to measure is its bending stiffness \(k_{R_x} \approx k_{R_y}\).
@ -136,23 +137,23 @@ The basic idea is to measured the angular deflection of the flexible joint as a
</p>
<div id="org43c60ee" class="figure">
<div id="org5c42ee1" class="figure">
<p><img src="figs/test-bench-schematic.png" alt="test-bench-schematic.png" />
</p>
<p><span class="figure-number">Figure 1: </span>Schematic of the test bench to measure the bending stiffness of the flexible joints</p>
</div>
</div>
<div id="outline-container-orgd387cac" class="outline-3">
<h3 id="orgd387cac"><span class="section-number-3">2.1</span> Flexible joint Geometry</h3>
<div id="outline-container-org1121b59" class="outline-3">
<h3 id="org1121b59"><span class="section-number-3">2.1</span> Flexible joint Geometry</h3>
<div class="outline-text-3" id="text-2-1">
<p>
The flexible joint used for the Nano-Hexapod is shown in Figure <a href="#org6500c8a">2</a>.
The flexible joint used for the Nano-Hexapod is shown in Figure <a href="#org4639f1b">2</a>.
Its bending stiffness is foreseen to be \(k_{R_y}\approx 20\,\frac{Nm}{rad}\) and its stroke \(\theta_{y,\text{max}}\approx 20\,mrad\).
</p>
<div id="org6500c8a" class="figure">
<div id="org4639f1b" class="figure">
<p><img src="figs/flexible_joint_geometry.png" alt="flexible_joint_geometry.png" />
</p>
<p><span class="figure-number">Figure 2: </span>Geometry of the flexible joint</p>
@ -174,8 +175,8 @@ Let&rsquo;s define the parameters on Matlab.
</div>
</div>
<div id="outline-container-org8da94ef" class="outline-3">
<h3 id="org8da94ef"><span class="section-number-3">2.2</span> Required external applied force</h3>
<div id="outline-container-org8e5eddc" class="outline-3">
<h3 id="org8e5eddc"><span class="section-number-3">2.2</span> Required external applied force</h3>
<div class="outline-text-3" id="text-2-2">
<p>
The bending \(\theta_y\) of the flexible joint due to the force \(F_x\) is:
@ -207,8 +208,8 @@ The measurement range of the force sensor should then be higher than \(20\,N\).
</div>
</div>
<div id="outline-container-orgdda06ee" class="outline-3">
<h3 id="orgdda06ee"><span class="section-number-3">2.3</span> Required actuator stroke and sensors range</h3>
<div id="outline-container-org5baf14d" class="outline-3">
<h3 id="org5baf14d"><span class="section-number-3">2.3</span> Required actuator stroke and sensors range</h3>
<div class="outline-text-3" id="text-2-3">
<p>
The flexible joint is designed to allow a bending motion of \(\pm 20\,mrad\).
@ -233,8 +234,8 @@ The measurement range of the displacement sensor should also be higher than \(0.
</div>
</div>
<div id="outline-container-orgb6763c2" class="outline-3">
<h3 id="orgb6763c2"><span class="section-number-3">2.4</span> First try with the APA95ML</h3>
<div id="outline-container-orge82143e" class="outline-3">
<h3 id="orge82143e"><span class="section-number-3">2.4</span> First try with the APA95ML</h3>
<div class="outline-text-3" id="text-2-4">
<p>
The APA95ML as a stroke of \(100\,\mu m\) and the encoder in parallel can easily measure the required stroke.
@ -262,17 +263,25 @@ And the tested angular range is:
</div>
</div>
<div id="outline-container-orge3df316" class="outline-3">
<h3 id="orge3df316"><span class="section-number-3">2.5</span> Test Bench</h3>
<div id="outline-container-orgfd806d9" class="outline-3">
<h3 id="orgfd806d9"><span class="section-number-3">2.5</span> Test Bench</h3>
<div class="outline-text-3" id="text-2-5">
<div id="org2a1f8c7" class="figure">
<p><img src="figs/test-bench-schematic.png" alt="test-bench-schematic.png" />
<div id="org0957ecc" class="figure">
<p><img src="figs/test_bench_flex_overview.png" alt="test_bench_flex_overview.png" />
</p>
<p><span class="figure-number">Figure 3: </span>Schematic of the test bench to measure the bending stiffness of the flexible joints</p>
</div>
<div class="note" id="orgf1de4cf">
<div id="org5b8e491" class="figure">
<p><img src="figs/test_bench_flex_side.png" alt="test_bench_flex_side.png" />
</p>
<p><span class="figure-number">Figure 4: </span>Schematic of the test bench to measure the bending stiffness of the flexible joints</p>
</div>
<div class="note" id="org96d3620">
<ul class="org-ul">
<li><b>Translation Stage</b>: <a href="doc/V-408-Datasheet.pdf">V-408</a></li>
<li><b>Load Cells</b>: <a href="doc/A700000007147087.pdf">FC2231-0000-0010-L</a> and <a href="doc/FRE_DS_XFL212R_FR_A3.pdf">XFL212R</a></li>
@ -285,73 +294,101 @@ And the tested angular range is:
</div>
</div>
<div id="outline-container-orgb94416f" class="outline-2">
<h2 id="orgb94416f"><span class="section-number-2">3</span> Agreement between the probe and the encoder</h2>
<div id="outline-container-org169b47f" class="outline-2">
<h2 id="org169b47f"><span class="section-number-2">3</span> Agreement between the probe and the encoder</h2>
<div class="outline-text-2" id="text-3">
</div>
<div id="outline-container-org57bb37e" class="outline-3">
<h3 id="org57bb37e"><span class="section-number-3">3.1</span> Results</h3>
<div id="outline-container-org5ed49b7" class="outline-3">
<h3 id="org5ed49b7"><span class="section-number-3">3.1</span> Setup</h3>
<div class="outline-text-3" id="text-3-1">
<p>
The measurement setup is made such that the probe measured the translation table displacement.
It should then measure the same displacement as the encoder.
Using this setup, we should be able to compare the probe and the encoder.
</p>
</div>
</div>
<div id="outline-container-orga83f29f" class="outline-3">
<h3 id="orga83f29f"><span class="section-number-3">3.2</span> Results</h3>
<div class="outline-text-3" id="text-3-2">
<p>
Let&rsquo;s load the measurements.
</p>
<div class="org-src-container">
<pre class="src src-matlab">load(<span class="org-string">'meas_probe_against_encoder.mat'</span>, <span class="org-string">'t'</span>, <span class="org-string">'d'</span>, <span class="org-string">'dp'</span>, <span class="org-string">'F'</span>)
</pre>
</div>
<p>
The time domain measured displacement by the probe and by the encoder is shown in Figure <a href="#orgfed4851">5</a>.
</p>
<div id="org090f800" class="figure">
<div id="orgfed4851" class="figure">
<p><img src="figs/comp_encoder_probe_time.png" alt="comp_encoder_probe_time.png" />
</p>
<p><span class="figure-number">Figure 4: </span>Time domain measurement</p>
<p><span class="figure-number">Figure 5: </span>Time domain measurement</p>
</div>
<p>
If we zoom, we see that there is some delay between the encoder and the probe (Figure <a href="#org8b829e0">6</a>).
</p>
<div id="orgeedac3e" class="figure">
<div id="org8b829e0" class="figure">
<p><img src="figs/comp_encoder_probe_time_zoom.png" alt="comp_encoder_probe_time_zoom.png" />
</p>
<p><span class="figure-number">Figure 5: </span>Time domain measurement (Zoom)</p>
<p><span class="figure-number">Figure 6: </span>Time domain measurement (Zoom)</p>
</div>
<div class="org-src-container">
<pre class="src src-matlab">finddelay(d, dp)
</pre>
</div>
<p>
This delay is estimated using the <code>finddelay</code> command.
</p>
<pre class="example">
316
The time delay is approximately 15.8 [ms]
</pre>
<div class="org-src-container">
<pre class="src src-matlab">Ts<span class="org-type">*</span>finddelay(d, dp)
</pre>
</div>
<pre class="example">
0.0158
</pre>
<p>
The measured mismatch between the encoder and the probe with and without compensating for the time delay are shown in Figure <a href="#org325c41d">7</a>.
</p>
<div id="org196ee5e" class="figure">
<div id="org325c41d" class="figure">
<p><img src="figs/comp_encoder_probe_mismatch.png" alt="comp_encoder_probe_mismatch.png" />
</p>
<p><span class="figure-number">Figure 6: </span>Measurement mismatch, with and without delay compensation</p>
<p><span class="figure-number">Figure 7: </span>Measurement mismatch, with and without delay compensation</p>
</div>
<p>
Finally, the displacement of the probe is shown as a function of the displacement of the encoder and a linear fit is made (Figure <a href="#org6b2fa2a">8</a>).
</p>
<div id="org4c16552" class="figure">
<div id="org6b2fa2a" class="figure">
<p><img src="figs/comp_encoder_probe_linear_fit.png" alt="comp_encoder_probe_linear_fit.png" />
</p>
<p><span class="figure-number">Figure 7: </span>Measured displacement by the probe as a function of the measured displacement by the encoder</p>
<p><span class="figure-number">Figure 8: </span>Measured displacement by the probe as a function of the measured displacement by the encoder</p>
</div>
<div class="important" id="orgd63f29c">
<p>
From the measurement, it is shown that the probe is well calibrated.
However, there is some time delay of tens of milliseconds that could induce some measurement errors.
</p>
</div>
</div>
</div>
</div>
<div id="outline-container-orgaca8c01" class="outline-2">
<h2 id="orgaca8c01"><span class="section-number-2">4</span> Measurement of the Millimar 1318 probe stiffness</h2>
<div id="outline-container-org0fbb329" class="outline-2">
<h2 id="org0fbb329"><span class="section-number-2">4</span> Measurement of the Millimar 1318 probe stiffness</h2>
<div class="outline-text-2" id="text-4">
<div class="note" id="org2b211f7">
<div class="note" id="org8fed4a1">
<ul class="org-ul">
<li><b>Translation Stage</b>: <a href="doc/V-408-Datasheet.pdf">V-408</a></li>
<li><b>Load Cell</b>: <a href="doc/A700000007147087.pdf">FC2231-0000-0010-L</a></li>
@ -362,37 +399,40 @@ And the tested angular range is:
</div>
<div id="org68dec3a" class="figure">
<div id="org2cc75ab" class="figure">
<p><img src="figs/setup_mahr_stiff_meas_side.jpg" alt="setup_mahr_stiff_meas_side.jpg" />
</p>
<p><span class="figure-number">Figure 8: </span>Setup - Side View</p>
<p><span class="figure-number">Figure 9: </span>Setup - Side View</p>
</div>
<div id="org28e5fd0" class="figure">
<div id="org91485ce" class="figure">
<p><img src="figs/setup_mahr_stiff_meas_top.jpg" alt="setup_mahr_stiff_meas_top.jpg" />
</p>
<p><span class="figure-number">Figure 9: </span>Setup - Top View</p>
<p><span class="figure-number">Figure 10: </span>Setup - Top View</p>
</div>
</div>
<div id="outline-container-org837827a" class="outline-3">
<h3 id="org837827a"><span class="section-number-3">4.1</span> Results</h3>
<div id="outline-container-orgc7d7173" class="outline-3">
<h3 id="orgc7d7173"><span class="section-number-3">4.1</span> Results</h3>
<div class="outline-text-3" id="text-4-1">
<p>
Let&rsquo;s load the measurement results.
</p>
<div class="org-src-container">
<pre class="src src-matlab">load(<span class="org-string">'meas_stiff_probe.mat'</span>, <span class="org-string">'t'</span>, <span class="org-string">'d'</span>, <span class="org-string">'dp'</span>, <span class="org-string">'F'</span>)
</pre>
</div>
<p>
The time domain measured force and displacement are shown in Figure <a href="#orged81df2">10</a>.
The time domain measured force and displacement are shown in Figure <a href="#orgd45dfc2">11</a>.
</p>
<div id="orged81df2" class="figure">
<div id="orgd45dfc2" class="figure">
<p><img src="figs/mahr_time_domain.png" alt="mahr_time_domain.png" />
</p>
<p><span class="figure-number">Figure 10: </span>Time domain measurements</p>
<p><span class="figure-number">Figure 11: </span>Time domain measurements</p>
</div>
@ -410,25 +450,33 @@ This is very close to the 0.04 [N/mm] written in the <a href="doc/tmp3m0cvmue_78
</p>
<p>
And compare the linear fit with the raw measurement data (Figure <a href="#orgba688b9">11</a>).
And compare the linear fit with the raw measurement data (Figure <a href="#org4939523">12</a>).
</p>
<div id="orgba688b9" class="figure">
<div id="org4939523" class="figure">
<p><img src="figs/mahr_stiffness_f_d_plot.png" alt="mahr_stiffness_f_d_plot.png" />
</p>
<p><span class="figure-number">Figure 12: </span>Measured displacement as a function of the measured force. Raw data and linear fit</p>
</div>
<div class="summary" id="org18e09dc">
<p>
The Millimar 1318 probe has a stiffness of \(\approx 0.04\,[N/mm]\).
</p>
</div>
</div>
</div>
</div>
<div id="outline-container-orgac55925" class="outline-2">
<h2 id="orgac55925"><span class="section-number-2">5</span> Experimental measurement</h2>
<div id="outline-container-orgda9e689" class="outline-2">
<h2 id="orgda9e689"><span class="section-number-2">5</span> Experimental measurement</h2>
</div>
</div>
<div id="postamble" class="status">
<p class="author">Author: Dehaeze Thomas</p>
<p class="date">Created: 2021-02-16 mar. 19:15</p>
<p class="date">Created: 2021-02-16 mar. 21:23</p>
</div>
</body>
</html>

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@ -174,9 +174,16 @@ And the tested angular range is:
** Test Bench
#+name: fig:test-bench-schematic
#+name: fig:test_bench_flex_overview
#+caption: Schematic of the test bench to measure the bending stiffness of the flexible joints
[[file:figs/test-bench-schematic.png]]
#+attr_latex: :width 0.8\linewidth
[[file:figs/test_bench_flex_overview.png]]
#+name: fig:test_bench_flex_side
#+caption: Schematic of the test bench to measure the bending stiffness of the flexible joints
#+attr_latex: :width 0.25\linewidth
[[file:figs/test_bench_flex_side.png]]
#+begin_note
- *Translation Stage*: [[file:doc/V-408-Datasheet.pdf][V-408]]

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