Motor stalls when driving from 0rpm in sensorless mode

Support
1

I am driving the motor in sensorless velocity control mode.

When I drive the motor above 100rpm everything is fine, but when I go below that, or stop the motor I am occasionally unable to return to speed (about 1/3 of the time). Restarting sensorless mode will resolve the issue and bring the motor back to speed.

I understand that sensorless mode has trouble with velocity control below 100rpm, and I dont need to drive slower than that, but I should be able to stop the motor and have it go back to speed on command without having to re-start sensorless mode. .

I have found that if I try to reverse the direction of the target velocity then it will get out of the stall (ie if I’m at 0rpm, I try to go to 1000rpm but the motor doesn’t do so, I then go to -1000 rpm and everything is fine).

Let me know if you need any details of my motor and I can provide it.

2

Hi Andrew,
The sensorless mode is not designed to operate at low speeds. If you require stopping, simply set the mode to idle, and set the mode back to sensorless when you need to start again.

3

Thank you for your reply. I ended up doing that as a hack. It works decently well. I’m having to set the ramp-up target speed to positive or negative depending on what direction I go. For example, if I want to go in the negative direction, by default it would ramp up to the target speed (500) then immediately change direction, so I have to add a bit of state in my code to set that value.