RPM PID Tuning - Instability on deceleration

[Kalyan_Sriram]

Hello,

I am currently tuning the Myxa ESC for RPM control mode driving this 50V 130KV motor

I have followed the guide to set max eangvel accel to 15,000 and decel to 9000. Voltage ramp is 1000V/s and current ramp is 1000A/s.

After tuning the PID controller for acceleration, very good performance was achieved:

Integral gain was increased after the above screenshot was taken, so steady state response is perfect now.

However, severe instability is observed when decelerating:

Decreasing Kd (which is already very small) does not resolve the issue, nor does decreasing Ki. Reducing the eangvel decel to 3000-4000 or decreasing Kp gain resolves the issue but reduces tracking performance and responsiveness. The drive is being used on a multirotor so quick response is critical.

Are there any other parameters I need to adjust to resolve deceleration instability?

Here are my parameters:
config.yml (1.9 KB)

Thanks,
Kalyan

[pavel-kirienko]

The voltage ramp is not used in RPM control mode but the current ramp is, and I suspect that 1000 A/s might be a bit too extreme in your case. Consider using a less steep current ramp and see if it helps. You may need to slightly adjust the PID gains afterward.

Edit: disregard the last part. You will need to configure a less steep deceleration ramp to avoid this issue. The current ramp setting appears adequate in your case.