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<p>Cool experiment. <br>
</p>
<p>Accelerometers don't help that much because when you are falling,
they are in free fall -- as it were -- and therefore don't have
any useful information to impart. However, gyros tell when the
body is rotating. That and the speed of rotation are all that's
needed. <br>
</p>
<p>If the inverted pendulum has a moveable bottom end, like a wheel
for example, rather than fixed in place like the example, then the
gyro and wheel feedback together totally constrain the movement of
the plant. Same with the classic printer carriage inverted
pendulum, like for example this one:
<a class="moz-txt-link-freetext" href="https://www.youtube.com/watch?v=NdbODkTNvp4">https://www.youtube.com/watch?v=NdbODkTNvp4</a><br>
</p>
<p>The lego experiment does seem to have to deal with lots of edge
cases, which always raises some red flags for me. Simpler is
usually more robust, as a general rule.</p>
<p>And speaking of PID, found this great article, very complete,
with some nifty history:</p>
<p><a href="https://www.wikiwand.com/en/PID_controller"
target="_blank" rel="nofollow"
data-saferedirecturl="https://www.google.com/url?hl=en-US&q=https://www.wikiwand.com/en/PID_controller&source=gmail&ust=1661212316294000&usg=AOvVaw1q7lmzx9uyvlbs7uRQYYRt">https://www.wikiwand.com/en/PID_controller</a></p>
<p>thanks Karim!</p>
<p>dpa</p>
<p><br>
</p>
<div class="moz-cite-prefix">On 8/21/22 6:33 PM, Karim Virani via
DPRGlist wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAKtnkiy91Wjd3Sa+Kgi2NMPuXaRkdegmvRiai28rRhB_bLy2zg@mail.gmail.com">
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#000000; font-size: large; font-family: sans-serif;"><strong><em
style="font-size: 11px;"> [EXTERNAL SENDER]</em></strong></p>
<div dir="ltr"><a
href="https://secure-web.cisco.com/16B_Ej4RXqIrh14ouP6NBo6mR_R4YDFOjBp9ZRQrDroxM9mYDkppWw8HBFDb8IRHvKuMa4GHn3IinBk2kHgEIGLz_7vBowU3xS11L2MQ-mXk0KPmX--LlwRq8dZTdicAw8oaqBoX8f4FEaxCNITE5k8HzNRPefFM-mS8jIQ7jSJt9Q5eLOnRIzyv_Yhfwm5IzExp3pW33v1cOAEjkF_krlxS6ZoTx0o0s1Jha1jHr9XXjZJvfBu_tkdppwm_ahsAenUpKi7hDBTlcXfj3S5-cDKIYpPLgsyER3SJ1favI-Lo/https%3A%2F%2Fyoutu.be%2FWObG2LoSEwQ"
moz-do-not-send="true">https://youtu.be/WObG2LoSEwQ</a><br>
<div><br>
</div>
<div>Just wanted to share this very nice example of deliberate
and experimental improvement of real world control of an
inverted pendulum (like walking) in this case using a reaction
wheel.<br>
</div>
<div><br>
</div>
<div>The number of configurations and variations tested is very
cool.</div>
<div><br>
</div>
<div>It also helps to clarify some concepts
around dynamic balance. Like accelerometers don't really help
because you are not actually chasing where up is, you are only
chasing the orientation where the gyro tends to flip direction
and change the slowest, and gyro drift doesn't really matter.
This is well demonstrated at 11:25.<br>
<br>
I'm tempted to say some things about their usage of Angle Fix
Rate and whether they really got the optimal PID values, but
I've had my fill of PID discussions for a while.</div>
<div><br>
</div>
<div>I just appreciate the thoroughness of the approach they
took and how well it was documented and communicated in the
video edit.</div>
</div>
<br>
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