Another topic about control modes

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  1. Hi! I don’t know will someone help me but I hope So, I’ve had an expirience of using original Odrive 3.6 and Odrive pro controllers, but currently need to build high power ugv (more that 10 kW per motor) and should switch to vesc With some expirience with vesc on smaller projects I found that vesc speed mode is different in compare of Odrive. For me odrive speed mode looks right, but vescs isn’t. What I actually mean is that Odrive will create some kind of resistance when speed is zero and try to hold the motor at zero speed, with different pid gains this hold will be less or more significant. But with the vesc I see that when the speed command is zero speed, driver just “release” the motor and it could spin freely. Does some one know is it the classic beahivour of speed mode, because I’ve also used bunch of different chinese controller in speed mode and the works the same way as an odrive. Could someone deeply describe what is actually happend and who is “more” correct for speed mode behaviour. Thanks a lot if someone helps!

  2. My thoughts about that is vesc implement some kind of tricky speed mode that don’t try to hold zero speed beacuse of domain of vesc (e vechicles, not robotics). So I hope to find some kind of advice and knowledge, may be it’s possible to tweak vesc firmware based on Odrive opensource code to behave similar way.

  3. Or I’m wrong, and that mode is not the speed mode, but somekind of speed-position mode?

The real life case scenario:
UGV moves downhill and stop in the middle of the paths. When It stops It should go down freely.

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Hi! I believe I responded to your question on the Discord, but I’ll give the quick notes for anyone else who may be interested:

Essentially, the ODrive does actual closed-loop speed control, changing the motor torque based on the measured speed, to set it to zero. Typically VESCs don’t do closed loop speed control, it acts more as a “throttle” input, where both the torque commanded and maximum speed is proportional to the “throttle”. This is like controlling a brushed DC motor with a voltage source, or the gas pedal in a car. VESC might have a closed-loop speed control mode, but I’m not sure.