Inconsistent current values during RL measurement

[GrantFreese]

Hi all,

I’m trying to tune a motor for use with a propeller (currently running with no load) with VESC on a Little FOCer v4. When I run the motor with 8% duty cycle, it will show 1.5-1.9 amps. Raising the duty cycle will make the current drop until it goes negative at 12% duty. The motor sounds like it’s running rough, so I don’t think it’s tuned correctly.

The other issue I noticed is that when doing the RL measurement with I=15A, I’ll sometimes have measurements that reach 18 amps, but some measurements cannot even reach 2 amps. In screenshot below, three RL detections were low current (less than 2 amps), with one high current that reached 18 amps.

In another test I did, three measurements reached 18 amps, while one only reached about 5 amps.

controller/motor: Little FOCer v4
firmware version: VESC 6.05
package version (and name): None
configuration details: XCELL Turbine V2 6565

Test setup is a 60V 16A bench power supply connected up to a 15S bank of 45F supercaps to simulate a pack, with a 45uF film cap in parallel.

Edit: Tried a second motor and motor controller, but I get the same the result. Also noticed that if I run with duty cycle=20% then switch to duty cycle=10%, the motor will rapidly increase in RPM, and the duty cycle will shoot past 50% despite not being commanded to do so.

Thanks,

Grant

[GrantFreese]

After digging into this a bit more, I’m thinking that the actual issue is that the observer is having a hard time keeping track of the rotor angle.

The phase currents look like a modulated waveform, even though the FOC motor phase line looks like a nice clean sawtooth. This is still a problem, right?

I think I’ve poked around with it enough to get pretty consistent RL readings of about ~12 mOhm and ~8 uH. Are these too low for the Little FOCer v4, or should it be able to handle this?

[GrantFreese]

Also, here’s a plot of duty cycle from 0% to 50%. The plot shows that power goes negative once we get past about 25% duty cycle.