[Dprglist] KD01 Rotate in Place video

[John Swindle]

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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