ESC not supplying the correct RPM

[andrespalomino]

Hi,
I was using ESC correctly for a while but after a small crash it is not working correctly. Next time I armed the drone, two motors burned (Motors 0 and 3 that matches the weird output bellow). I'm looking at the esc-tools and motors spin correctly when they are separately but when all 4 are working RPM, current, power are very badly.

What could I check to solve it?
Thanks

Bellow there's a short section of output for python voxl-esc-spin.py --id 255 --rpm 4500 --timeout 1

[2] RPM: 4473, PWR: 16, VBAT: 10.45V, TEMPERATURE: 36.30C, CURRENT: -0.49A
[3] RPM: 1418, PWR: 54, VBAT: 10.44V, TEMPERATURE: 35.21C, CURRENT: 24.40A
[0] RPM: 1659, PWR: 54, VBAT: 10.45V, TEMPERATURE: 35.99C, CURRENT: 21.18A
[1] RPM: 4482, PWR: 16, VBAT: 10.46V, TEMPERATURE: 35.41C, CURRENT: 0.04A
[2] RPM: 4473, PWR: 16, VBAT: 10.45V, TEMPERATURE: 36.30C, CURRENT: -0.49A
[3] RPM: 1418, PWR: 54, VBAT: 10.44V, TEMPERATURE: 35.21C, CURRENT: 24.40A
[0] RPM: 1659, PWR: 54, VBAT: 10.45V, TEMPERATURE: 35.99C, CURRENT: 21.18A
[1] RPM: 4496, PWR: 15, VBAT: 10.57V, TEMPERATURE: 35.55C, CURRENT: 0.18A
[2] RPM: 4473, PWR: 16, VBAT: 10.45V, TEMPERATURE: 36.30C, CURRENT: -0.49A
[3] RPM: 1418, PWR: 54, VBAT: 10.44V, TEMPERATURE: 35.21C, CURRENT: 24.40A
[0] RPM: 1659, PWR: 54, VBAT: 10.45V, TEMPERATURE: 35.99C, CURRENT: 21.18A
[1] RPM: 4496, PWR: 15, VBAT: 10.57V, TEMPERATURE: 35.55C, CURRENT: 0.18A
[2] RPM: 4586, PWR: 13, VBAT: 11.40V, TEMPERATURE: 36.14C, CURRENT: -0.16A
[3] RPM: 1418, PWR: 54, VBAT: 10.44V, TEMPERATURE: 35.21C, CURRENT: 24.40A
[0] RPM: 1659, PWR: 54, VBAT: 10.45V, TEMPERATURE: 35.99C, CURRENT: 21.18A
[1] RPM: 4496, PWR: 15, VBAT: 10.57V, TEMPERATURE: 35.55C, CURRENT: 0.18A
[2] RPM: 4586, PWR: 13, VBAT: 11.40V, TEMPERATURE: 36.14C, CURRENT: -0.16A
[3] RPM: 1553, PWR: 54, VBAT: 10.84V, TEMPERATURE: 35.27C, CURRENT: 24.09A
[0] RPM: 1366, PWR: 54, VBAT: 10.57V, TEMPERATURE: 36.34C, CURRENT: 20.84A
[1] RPM: 4496, PWR: 15, VBAT: 10.57V, TEMPERATURE: 35.55C, CURRENT: 0.18A
[2] RPM: 4586, PWR: 13, VBAT: 11.40V, TEMPERATURE: 36.14C, CURRENT: -0.16A
[3] RPM: 1553, PWR: 54, VBAT: 10.84V, TEMPERATURE: 35.27C, CURRENT: 24.09A
[0] RPM: 1366, PWR: 54, VBAT: 10.57V, TEMPERATURE: 36.34C, CURRENT: 20.84A
[1] RPM: 4499, PWR: 15, VBAT: 10.53V, TEMPERATURE: 35.42C, CURRENT: 0.18A
[2] RPM: 4586, PWR: 13, VBAT: 11.40V, TEMPERATURE: 36.14C, CURRENT: -0.16A
[3] RPM: 1553, PWR: 54, VBAT: 10.84V, TEMPERATURE: 35.27C, CURRENT: 24.09A

[andrespalomino]

@Vinny Hi, any inputs on this topic would be appreciated,

Thanks

[Alex Kushleyev]

Hello @andrespalomino ,

It is possible that during crash the motors have sustained some critical damage. Since you indicated the motors "burned" that usually means the winding insulation has melted and there is probably internal short inside the motor.

when you say motors spin correctly when they are separately - are all 4 motors spinning at the desired 4500 rpm with very little current, if tested individually?

Hopefully the ESC is still working fine (please check it for any indication of burned components).

You can do a quick test in open loop mode before replacing the motors:

python voxl-esc-spin.py --id 255 --power 10 --timeout 1

This will apply a fixed power of 10% and it is a very "gentle" test mode to make sure the new motors and ESC are working properly. You can test with propellers or without (maybe better without propellers at first). All 4 ESCs should spin around the same RPM and current should be very low. You can increase the test duration from 1 second if all goes well.

As next step, I would suggest replacing the two motors that are not spinning correctly. Burned motors typically means they need to be replaced. After motor replacement, you should repeat the spin test in open loop mode (in previous step).

Also, are you able to share the motor and propeller used on your vehicle?

Alex