Arlobot DHB-10 motor board bug with encoders

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  • VonSzarvasVonSzarvas Posts: 1,257
    edited August 7 Vote Up0Vote Down
    Roy Eltham wrote: »
    Ken,
    Can I just get the latest firmware to update my boards? Or is there a hardware revision?

    At the moment this is a hardware revision.

    It may not impact everyone. The issue relates to rapid direction changes and more-so when the 3 motor bolts are not tightened to the same amount, which pulls the motors off-parallel to the motor mounting blocks, putting uneven strain on the wheel shaft.

    More likely those with DHB-10's bought in the last year using encoders bought in the last year (identified as those with pre-soldered headers) are affected.
    Note... the encoders are not an issue, but just to use those as an approx. timeline.


    Firmware:

    The latest firmware is the same v1.0 version that shipped with DHB-10's, and also available here: https://www.parallax.com/downloads/dhb-10-motor-controller-firmware

    Earlier in this thread, David Carrier posted a special version of v1.0, which added a STATUS command to return the last error code. (That was the only difference from v1.0).
    David's version could be used as direct replacement to v1.0, but it didn't get pushed to an official release.


    GitHub:

    Some other news.... Parallax are looking into pushing the source code into GitHub, subject to summer work queues/etc.!
    Once that happens, someone will get David's update included too. Either me for sure, or whoever beats me to it! (as I think there are a few interested parties watching for the GitHub moment)


  • Thanks for the update VonSzarvas. I haven't been having any issues, and I believe all my DHB-10s are more than a year old. I never noticed any issues with the aluminum blocks or mounting bolts binding on my Arlo's.

    I, also, don't really do rapid direction changes. My code is such that when any of the sensors indicate "getting close to something" I slow down first, then stop or change direction when it get's inside of a second threshold. Helps keep my walls and furniture from getting banged up. :)

  • Ken GraceyKen Gracey Posts: 6,285
    edited August 10 Vote Up0Vote Down
    We're starting to send out new DHB-10s to customers who've bought and had issues. Please destroy the old hardware so it doesn't get mixed up in the process.

    The picture is our latest production run.

    Ken Gracey
    2016 x 1512 - 1012K
  • Ken Gracey wrote: »
    We're starting to send out new DHB-10s to customers who've bought and had issues. Please destroy the old hardware so it doesn't get mixed up in the process.

    This is the reason I will ALWAYS be a Parallax customer! You all are incredible! Amazing customer service.

    Whit+

    "We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney
  • Indeed Whit, they do their best to take care of the customer and make things right! That's why I love Parallax too!
    Plus Ken and Chip and all the others I have met from there are super nice and smart folks! Several of them I count as friends, even if long distance ones.
  • Update: Our preliminary testing on one robot with the new controller board shows the problem has been resolved. We have been able to:
    - Switch back to the closed loop GOSPD instead of the open loop GO commands.
    - Increase command frequency back to 30Hz
    - Give extremely low values of velocities to the robot without the controller seizing up. We were unable to go below 0.2 m/s previously, but we have now run the robot successfully at all lower speeds.

    We will be testing on three other robots in the upcoming weeks, including one we never got to work even with our workarounds in place. I'll report back once that is complete.
  • Thanks for keeping us posted!

    Good news so far, I'm glad things are working out.

  • How is everybody doing with their new boards? Have not heard from anyone but @piyushk.
    Infernal Machine
  • I received a new DHB-10 board a couple of weeks ago, plugged it in and ran one of the first tests posted in this thread. Initially, the board did not behave any differently than my original board. It faulted out in about the same amount of time.
    I made a change to the firmware requiring 3 consecutive reads of a fault on the HB chip before stopping, tested that, and could not get the board to fault out. Ok, great.
    Then to attempt to make sure my firmware was doing what I thought it should be doing, I changed the fault threshold back to 1 and re-tested. I could not get the board to fault out.
    I re-loaded the first version of debug firmware from David Carrier and tested. I could not get the board to fault out (I was removing the prop-plug in each case).
    I re-loaded the (presumably) original firmware and could not get the board to fault out.
    I have been unable to recreate the original fault out scenario since I have reprogrammed the board.
    I guess this is good news, but I am puzzled by it. There were no mechanical changes between any of the above tests.
    After the testing above, I decided to make some mechanical modifications as well to attempt to further improve my operating margins.
    I went ahead and drilled out the large holes in the aluminum blocks to enlarge them slightly. I did not alter the smaller holes that the bolts pass through.
    I also spent considerable time trying to improve the centering of the encoder wheel in the optical sensor channel on one side of my platform.
    Finally, I added 0.0055" shims (aluminum soda can material) between the window motor attachment points and the standoffs, to relieve some of the pressure on the bearings. There is still a noticeable difference in play, or lack thereof, between the two sides after doing this.
    Since doing all of the above, and running with my modified firmware, I have done considerable driving of the robot (all based on GOSPD ) and have not had the DHB-10 board fault out.
    It remains to be seen how good the odometry is.
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