[Dprglist] straight lines

[David P. Anderson]

Paul,

Sorry for the confusion.  I believe I answered this question in the 
previous post.

dpa


On 1/15/22 5:32 AM, Paul Bouchier via DPRGlist wrote:
>
> */[EXTERNAL SENDER]/*
>
> 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?
>
> 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?
>
> Thanks
>
> Paul
>
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