Locked at full speed - out of control multiple motors with same shaft - PPM app issue over CANbus

How-Tos & Esk8 mechanics Esk8 Mechanics
25

Hey Guys,

So, I’ve been playing around to get some more inputs on this subject of having the motors locked at full speed with duty cycle control and it seems it’s really nothing related with Canbus communication or interference on the lines or any of those things.

Current control does not have it, having a separated vesc with PPM receiver (far from interference) does not solve it and I can see with the VescTool all the inputs from the remote are still responding well while locked at full speed.

I did tried PID speed controll and the motors don’t get locked at full speed. I just didn’t switched already to PID because the slave motors keeps jittering and whining a bit while no throttle input, which is not pleasant to se all machine shaking a bit while in idle (any ideas on how to remove this behavior?)

Other things that might be relevant to this discussion:

  • I had some locking at full speed even with the DutyCycle below 84%

  • I did tried a custom PPM device that can send a “stop” command to the VESC if the throttle is released and it does stop the locking at full speed, but it works as a hard stop, so it is not a solution.

  • If I go full throttle with 95% Duty Cycle and it gets locked, when I release the throttle, the master vesc keeps reporting negative current (below screen capture “A”) and slaves keeps reporting the max amps defined in “motor max current” (screen “B”)
    This is unloaded test, so the system usually only gets 2 or 3 amps to run (screen “C” and “D”), but when the "locking gets in place, it shows max amps on the motor…

A)

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B)
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image1190×718 158 KB

C)
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image1193×720 189 KB

D)
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image1194×721 191 KB

So, I don’t know what else to do to have this sorted, but I would really like someone with deeper knowledge on firmware to give some input on this.
I think I can go with PID speed control if I solve the whining issues, but I think this Dutycycle thing would be interesting also to solve, as dutycycle is straight forward and does not require to mess with PID settings that can take a while to figure out.

Thank you again for all the inputs. If you guys wanted me to be making more test, let me know, I will try everything until we can find a solution.

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