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maytech mto91hbm-nh motors hal sensor

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nolander
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VESC Free
Joined: 2018-11-30 01:54
Posts: 3
maytech mto91hbm-nh motors hal sensor

Hello, 

I am using maytech mto91hbm-nh motors and the RPM measurement in the VESC tool is pretty good when the motors are spinning in one direction, but in the other direction the RPM measurement will suddenly spike to the opposite direction, which causes the speed control to fail (Seems the vesc stalls the motor when this happens, and i have to reload the motor config in order to make the speed control responsive again). 

All four motors seem to have the same issue.

Has any body experienced something similar to this and can give me advice on how I might fix the problem?

UPDATE: The rpm measurements seem to be just fine actually (I can successfully read them when controlling the duty cycle directly), but the problem seems to be that the speed control (PID) only works in one direction, and I still don't know why.

Thanks.

sunsam8
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Last seen: 1 week 2 days ago
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Joined: 2018-04-02 13:27
Posts: 9

It seems that maytech positioned the hall sensors with an offset. That means the hall signal is not in the 0 crossing of the magnetic field from the rotor magnet. The user should not need to adjust timing in their ESC when using the right rotation direction

Also the case: the hall sensors have a hysteresis and a different switch point (not zero) for N to S or S to N magnetic field strength crossing. Exact same hall timing when changing rotation is therefore not possible.

Different motor timing from sensor,  dependend on rotation direction, leads to the problems descriped.

Suggestion would be to run a seperate FOC hall sensor entry offset table for each direction.