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<p>Forward from Dave Ackley</p>
<p>dpa</p>
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<th valign="BASELINE" nowrap="nowrap" align="RIGHT">Subject:
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<td>My Robot Chassis Dynamometer</td>
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<th valign="BASELINE" nowrap="nowrap" align="RIGHT">Date: </th>
<td>Tue, 22 Jun 2021 21:12:34 -0500</td>
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<th valign="BASELINE" nowrap="nowrap" align="RIGHT">From: </th>
<td>David Ackley <a class="moz-txt-link-rfc2396E" href="mailto:dackley@verizon.net"><dackley@verizon.net></a></td>
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<td><a class="moz-txt-link-abbreviated" href="mailto:dackley@verizon.net">dackley@verizon.net</a></td>
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<th valign="BASELINE" nowrap="nowrap" align="RIGHT">To: </th>
<td>'Anderson, David' <a class="moz-txt-link-rfc2396E" href="mailto:dpa@mail.isem.smu.edu"><dpa@mail.isem.smu.edu></a></td>
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<p class="MsoNormal"><span style="color:#1F497D">Hi David<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">I found the
email I had sent you and modified it for the DPRG mailing
list.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">I tried sending
it via the DPRG list, but it didn’t seem to go out.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">So I’d
appreciate it if you would send it out to the DPRG mailing
list.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Thanks<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Dave<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b>From:</b> David Ackley
[<a class="moz-txt-link-freetext" href="mailto:dackley@verizon.net">mailto:dackley@verizon.net</a>] <br>
<b>Sent:</b> Tuesday, June 22, 2021 9:05 PM<br>
<b>To:</b> 'DPRGlist'
<a class="moz-txt-link-rfc2396E" href="mailto:dprglist-bounces@lists.dprg.org"><dprglist-bounces@lists.dprg.org></a><br>
<b>Subject:</b> My Robot Chassis Dynamometer<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span style="color:black">Hi All<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:black">My “Robot Chassis
Dynamometer” is what I tried to show at the</span> <span
style="color:black">9/24/2020 VRBNO meeting, but I’m not
sure whether it ever showed up when I was discussing it or
that people followed my description.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:black">Just in case it
didn’t show up I’ve attached a picture of the bare “Robot
Chassis Dynamometer” and a picture of my “Build-More-Robots”
robot sitting on it that I’m going to try tuning the PID on.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:black">I really like the
size, cost, and characteristics of the “Build-More-Robots”
robot, so I have several different versions of it.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black">I decided that
what I really wanted was a way of running this robot in
place while analyzing and tuning up its PID.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black">So I came up with
the idea of building a “Robot Chassis Dynamometer” where
load/inertia on the robot’s wheels is a reasonable
approximation to what the robot would see if it was actually
running around “In-The-Wild”.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:black">In theory, the
inertia that a robot’s wheels see is roughly the robot’s
mass (Mr) times its wheel radius (Rr) squared <o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black">(i.e.~ Mr*Rr**2).<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:black">So I built a
“Robot Chassis Dynamometer” with two flywheels that the
robot’s two wheels drive that try to approximate the effect
of the robot’s inertia. <o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:black">The inertia of a
solid flywheel is <b><i>one half</i></b> its mass (Mrcd)
times its radius (Rrcd) squared <o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black">(i.e. ˝ Mrcd *
Rrcd **2).<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:black">So I got a chunk
of metal with a suitable mass and radius such that its
inertia approximates my robot’s mass and wheel radius to
build the “Robot Chassis Dynamometer” shown in the attached
pictures.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:black">Enjoy<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:black">Dave<o:p></o:p></span></p>
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