I have a BLDC motor on a controller I built running in both forwards and reverse.
However the reverse direction is substantially noisier than the other and the motor vibrates more almost as if the commutation sequence were wrong.
I am using the same sequence for iterating through the 6 commutation states in either direction based on the hall status.
For going forwards I take the position from the hall sensors and map that to N "state" in my list of 6 states, I then set the motors to N+1 state.
For going backwards I do the same but use the N-2 state. (modulo 6)
I am working on the assumption that N+1 is magnetic field in advance of the poles by of 60-120 degrees, N is 0-60 degrees, N-1 is -60 to 0 degrees and N-2 is -120 to -60 degrees – this seems to hold true experimentally using the N and N-1 states, the move, but slowly and jerkily.
I'm using a very low duty cycle PWM (10%) at the moment with a 32V power source (the motor is rated for 48V – this motor specifically https://en.nanotec.com/products/2873-db59c048035-a/)
Why would it consistently behave fine in one direction, but not the other?
Thanks
Best Answer
When I was running slot cars with brushed motors in the late 60s I played with advancing the timing, by rotating the brush assembly until the forward rotation was fastest at a given voltage. This of course made the motor asymmetrical with regard to forward and reverse operation.
Your noisy reverse operation may be from a very similar situation. The motor with sensors may be "factory tuned" to operate more efficiently in the nominal forward direction.
One might try playing with the timing in the reverse direction to try to compensate for the (possibly) asymmetrical motor timing and remove the reverse direction noise. Tuning timing for minimum noise may do the trick. Hope this helps!