[Dprglist] KD01 Rotate in Place video

[Doug Emes]

The insight about the caster is huge, great thought my friend.

On Tue, Jan 26, 2021 at 2:13 AM John Swindle via DPRGlist
<dprglist at lists.dprg.org> wrote:
>
> The slight surge is likely due to windup. The gears were at limit when the first rotation stopped, so the second rotation would have a delay and then a jerk.
>
> Also, the caster has to rotate, and that creates an effect that the control system might not know about.
>
> Suggest a windup preamble in all motor commands.
>
> I am not a mech eng, but I joined DPRG to learn relevant mechanical things, and I've learned more than I expected.
>
> Later,
> John Swindle
>
>
> -----Original Message-----
> From: Murray Altheim via DPRGlist <dprglist at lists.dprg.org>
> To: dprglist at lists.dprg.org
> Sent: Mon, Jan 25, 2021 1:52 am
> Subject: Re: [Dprglist] KD01 Rotate in Place video
>
> I've just updated the KD01 Rotate-in-Place Test video on YouTube, which now
> performs a bit better than the previous version: the KD01 accelerates properly
> up to speed counter-clockwise, maintains that for 10 seconds, then decelerates
> to a stop, then does the same thing clockwise:
>
>   KD01 Rotate in Place Test
>   https://youtu.be/HICrQzAZPow
>
> The position of the robot at the end of the test is about 4cm from its initial
> position, which isn't too bad all things considered. There is a noticeable
> surge when the robot starts again clockwise after a pause. I'm not sure what
> this is caused by -- nothing in the code is indicative -- but I'm overall
> happy with the result. I think it helped that I ran the test this time on
> some smooth particle board.
>
> The NZPRG Python robot code can be found at:
>
>     https://github.com/ifurusato/ros
>
> with the rotate-in-place test file at:
>
>   https://github.com/ifurusato/ros/blob/master/rotate_in_place.py
>
> The KD01 is a differential drive robot that uses a Raspberry Pi with a
> PiBorg ThunderBorg motor controller, an OSEPP drive train and hall effect
> motor encoders, a tiny Adafruit Mini PiTFT 135x240 Color display that I
> use as a console window, which includes two small buttons I've wired up
> to initiate/control the test. The rear caster is an OSEPP wheel installed
> into the frame of a commercially-available caster.
>
> Cheers,
>
> Murray
>
> On 23/01/21 4:04 pm, Murray Altheim via DPRGlist wrote:
> > Sometimes it's important to prove one is making progress. Not that this is
> > advancing the science at all but I've just posted a video showing the KD01
> > differential drive robot rotating in place using its PID controllers: [...]
> ...........................................................................
> Murray Altheim <murray18 at altheim dot com>                      = =  ===
> http://www.altheim.com/murray/                                     ===  ===
>                                                                     = =  ===
>     In the evening
>     The rice leaves in the garden
>     Rustle in the autumn wind
>     That blows through my reed hut.
>             -- Minamoto no Tsunenobu
>
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