Noise on Lift+Cruise VTOL Motor Outputs

Flight Testing & Log Analysis
1

Hello everyone,

I’m reaching out for some guidance on an issue I’ve encountered with my VTOL setup, and I’d greatly appreciate any insights or suggestions from those with more experience.

Quick Setup Overview:
I’m flying a lift + cruise VTOL with a total mass of about 16 kg. It features 8 hover motors and 2 pusher motors for forward flight, all controlled via UAVCAN v0. The flight controller is running a custom version of the latest stable release, and everything has been tuning quite nicely for basic hover and transition maneuvers.

The Issue:
As shown on the pictures, I’m seeing quite noticeable noise/oscillations on the hover motor outputs. I am not entirely certain but I suspect this is causing the ESCs to run quite hot (up to 70-80°C after 5 minutes of hover). The vehicle handles the flights stably, but I’d like to address this before I destroy an ESC and crash. The PX4 vibration metric is always in the green.

What I’ve Tried So Far:

Reduced the MC rate controller D-gain and P-gain for roll and pitch axes. This did not help to mitigate the noise. Further, I am using a slew rate limit, which also does not help much due to the low amplitude of the noise. Increasing it further would mean to trade control authority.

My Questions:

  1. Based on the vehicle size and config, does this level of motor output noise sound excessive for a 16 kg VTOL, or is it within expected range?

  2. What additional tuning steps can you recommend?

I’d be thrilled to hear your thoughts and if this is just normal or requires more extensive tuning of filters and controller gains.

Thank you so much in advance for your help :slight_smile:

Best,

Jan

image
image759×341 59.4 KB

image
image772×341 67.9 KB

image
image783×678 83.9 KB

image
image816×670 128 KB

Just as example: Noisy roll angle setpoint

image
image759×341 41.3 KB

2

Have you tried reducing the filter bandwidth cutoffs?

And have you tried reducing the D gain quite a bit? I think even setting it to 0 might be worth a (careful) try. @dakejahl that’s what you said, right?

3

Hi Julian, thanks for your help! I will definitely try that.

Best,

Jan

1 Like
4

Just wanted to support Julian’s advice. We saw similar traces when we first set up our vehicles. The default filter (something like 50 Hz cutoff) was way too high. For your size, you are likely going to want something along the lines of 5-10 Hz depending on the speed of your inner-loop controllers.