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<p>Paul,</p>
<p>Sorry for the confusion. I believe I answered this question in
the previous post. <br>
</p>
<p>dpa</p>
<p><br>
</p>
<div class="moz-cite-prefix">On 1/15/22 5:32 AM, Paul Bouchier via
DPRGlist wrote:<br>
</div>
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<div>David - going back to your description of how you manually
turned the wheel a little bit when the speed was supposed to
be zero, and the integral of speed error built up until it
overpowered you and drove the wheel back to where it started -
I'm confused because I don't understand how you must be
calculating speed for that to be true. A naive implementation
of speed-measurement would be to count the number of encoder
counts in each 40ms tick. So when you manually moved the
wheel, let's imagine there were a few ticks when a few counts
were detected, then no more counts in any subsequent ticks.
Speed should be zero after motion stops, so where's the error
to integrate and cause corrective force to build up over time?
Put another way, there was a speed error a few seconds ago but
now there's no speed error; when does that error "go away",
and when does the PID loop stop remembering it and trying to
fight against it?</div>
<div><br>
</div>
<div>This is relevant to my current concerns with Mowbot, since
it was discovered at Tuesday's meeting that the low rate of
encoder ticks on Mowbot means I'll only see 2 or 3 counts per
tick (hard to control), so I'm thinking about adopting Pat's
approach (which he gave up on) of measuring the period between
count incrementing. Pat - I'm also wondering why you gave up
on that approach and changed encoders to one that has more
counts - was there some basic flaw in the approach?<br>
</div>
<div><br>
</div>
<div>Thanks</div>
<div><br>
</div>
<div>Paul<br>
</div>
</div>
<br>
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