PiStorms motor issues
 Hardware Related   Started by Daniel Walton   2016-08-26 22:59:05 -04:00   Comments: 5    Viewed: 436

  1. I am having problems controlling a Large EV3 motor using pistorms.  I started off with an older PiStorms board and was using ev3dev, I was seeing an issue where the motor never really stopped, it would just sort of shake after it was supposed to stop.  You can see the video here:
    https://www.youtube.com/watch?v=NjeqUuCAIHc

    I posted about it at ev3dev https://github.com/ev3dev/ev3dev/issues/696 , dltech suggested I had a bad board so I asked mindsensors for a replacement (thank you for the replace).  So now I have a brand new board but I still see the exact same issue.

    dltech asked me to try using the PiStorms software so I gave that a try.  I still see issues but they are a little different.  The motor rotates but it doesn't really move like it does with ev3dev, it does "click" though as if it is trying to move but isn't getting enough power (it shouldn't be moving at all).  Here is a video of my rpi2 with brand new PiStorms board running PiStorms v4.006 with firmware 2.06:

    https://www.youtube.com/watch?v=T-CHCVdhz0s

    I also tried with a rpi3 and see the same issue.

    Thoughts?
    Daniel Walton, 2016-08-26 22:59:05 -04:00
  2. Deepak Patil
    Deepak Patil Administrator Staff Member Richmond
    holdOnCompletion tends to jitter motors.
    also, limit the motor speed to 100.

    in other words, change your function call as follows: 
    line ->> psm.BAM1.runDegs(1000, 400, True, True)
    change it to:
    psm.BAM1.runDegs(1000, 100, True, False)


    Deepak Patil, 2016-08-27 15:27:14 -04:00
  3. Disabling holdOnCompletion fixes it even with speed 400.  Are there plans to fix the holdOnCompletion jitter issue?
    Daniel Walton, 2016-08-28 13:34:36 -04:00
  4. Deepak are there plans to fix the holdOnCompletion jitter issue?
    Daniel Walton, 2016-09-03 14:29:14 -04:00
  5. Deepak Patil
    Deepak Patil Administrator Staff Member Richmond
    my apologies in delay in responding,
    the issue is, holdOnCompletion is meant to hold the motor in position from drifting due to external force.
    To hold that position that, PiStorms applies power and holds the motor to the last encoder value,
    but and under certain conditions, (and we suspect, when the external load is negligible), the motor tends to jitter.
    Our engineering has tried to fix this issue since you reported, but are not able to fix it.
    Deepak Patil, 2016-09-13 15:35:49 -04:00
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