<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
</head>
<body>
<p>PS, forgot to mention. Since the bottom end of his pendulum is
fixed, an IMU is not really needed. A simple low-friction pot
will do to deduce the angle. That's how I began my balancing
robot experiments back in the before time:
<a class="moz-txt-link-freetext" href="http://www.geology.smu.edu/dpa-www/robo/nbot/polebot.mpg">http://www.geology.smu.edu/dpa-www/robo/nbot/polebot.mpg</a><br>
</p>
<p>cheers!</p>
<p>dpa</p>
<p><br>
</p>
<div class="moz-cite-prefix">On 8/21/22 7:03 PM, David P. Anderson
via DPRGlist wrote:<br>
</div>
<blockquote type="cite"
cite="mid:35a09750-1d15-2fba-4fba-062cebff663a@smu.edu">
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<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://secure-web.cisco.com/1g7ebb1_wK9t-D5bNCuP4C6VZZxAWhxSmwXEA80v1rBMyxz45grwCKHTrltpsnplE2uZK-aD0gOw3T_QDBoodfGQF7iN9JB7Yb08AmFOl5MtHtkdMGsIMRceB7ZMOnD0VflGDxW9tX0iRAFRHBQ3R--12pQi8S7sqm7FFzqBUoEOQcBg_QHM1f4-ByM_D81qg5HvnfWy8bt_ZIrLLb4oVdH9T4XhkoODMSSL-hPSqT8K9Vo-hqu6Y9XVsQeLHmk877Ev7wAnKvkf_afrqtBxgMpOvh7OhhIMOIDnmGIjj918/https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DNdbODkTNvp4"
moz-do-not-send="true">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://secure-web.cisco.com/1eofDntL9pzGQ8zQ2siZtPMyQiqYcM-lHUy9mesofY7rIWDRHBE4IS1-05YFxe4Dh6IgKuRjsjPkwyuonHubPuciNVCoD3ckiBXGkAJ8Xq6nHfUquR_MVAPm-rY7Pis7OfeTFr0f_NJ_zS4T83ac0sOgKR4fkREQNRP-5aE4wO5DpvFAEHeyxHBm2MEn7t9kysciN-TZjKO5fXsPJfWFYOqBl6XshnZgsV6OE_IcriUykrHS0xj2YJuRFQTNNVB3UQ7nwYthVnAW1RiHgMkvB8YVPczcJRtnyTZpDopHDgYI/https%3A%2F%2Fwww.wikiwand.com%2Fen%2FPID_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"
moz-do-not-send="true">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">
<p style="background-color: #f4eaa5;color: #000000
;margin:5px;padding: 2px;text-align: left !important;
align-content: center; display: block; border: 1px solid
#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>
<fieldset class="mimeAttachmentHeader"></fieldset>
<pre class="moz-quote-pre" wrap="">_______________________________________________
DPRGlist mailing list
<a class="moz-txt-link-abbreviated" href="mailto:DPRGlist@lists.dprg.org" moz-do-not-send="true">DPRGlist@lists.dprg.org</a>
<a class="moz-txt-link-freetext" href="http://lists.dprg.org/listinfo.cgi/dprglist-dprg.org" moz-do-not-send="true">http://lists.dprg.org/listinfo.cgi/dprglist-dprg.org</a>
</pre>
</blockquote>
<br>
<fieldset class="mimeAttachmentHeader"></fieldset>
<pre class="moz-quote-pre" wrap="">_______________________________________________
DPRGlist mailing list
<a class="moz-txt-link-abbreviated" href="mailto:DPRGlist@lists.dprg.org">DPRGlist@lists.dprg.org</a>
<a class="moz-txt-link-freetext" href="http://lists.dprg.org/listinfo.cgi/dprglist-dprg.org">http://lists.dprg.org/listinfo.cgi/dprglist-dprg.org</a>
</pre>
</blockquote>
</body>
</html>