Heavy Lift Drone Oscillations (PID issue?)

PX4 Autopilot
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I’ve built a prototype heavy lift agricultural drone! It is by far the biggest quad I’ve ever built. This much power in the motors ( https://uav-en.tmotor.com/2024/a_series_0821/1228.html ) and lifting capability (over 50Kg of thrust per motor) has definitely put the PID adjustments into a new category. I can takeoff, hover and land safely, but as soon as I start horizontal translation, it starts oscillating badly and crashes. You can watch the latest crash flight here:

https://drive.google.com/file/d/1NmoJvafcP4J66X4d6mjuj2tFHU53LSqW/view?usp=drive_link

I’m assuming a PID issue, but if you think it might be something else, please let me know. If it is a PID issue, what is the most likely culprit to adjust first. This is a heavy lift drone, but it is currently being tested without anything in the payload, so it is very overpowered for its empty payload weight!

Some more details: aluminum frame with motors 7’ apart on center, 56” propellers, PX4: v1.15 on a Cube Black, QGroundControl: 4.4.2 on a Herelink 1.1 controller. Current flight weight (no payload) 125lbs/57kg (including the 25lb/11.4kg battery pack).

Thank you!

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No access to your link. Please share logfiles using logs.px4.io.

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Sorry about that. I’ve updated the link and permissions to the video. I’ll see if I can recover the log from that flight.

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Now I see it. Didn’t realize it was a video.

Sorry about the crash!

So, obviously needs tuning but you don’t want to have more crashes like this during tuning, so what I always suggest for first testing is to fix it to the ground with a rope and e.g. only allow it to go up to 1m or less if you can fly that. Then you want to do really small hops and figure out how it behaves.

If you want to go safer than that, you have to suspend it somehow, so you have it fixed with a rope from above and from below, and that way you can always use the kill switch to stop all motors and catch it. Then you iterate on the controls in stabilized, mostly MC_ROLLRATE/PITCHRATE_P for a start. Also, start with MC_ROLL_P and MC_PITCH_P lower than default, e.g. 3-4 instead of 5-6 to just make everything less aggressive.

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Thank you for the suggestions with those specific four parameters to adjust. I will definitely make them less aggressive. Here is the logfile from that flight (https://review.px4.io/plot_app?log=8f6b25a2-f1ba-42d7-913d-d8dd45f97be4).

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Hello,
We are experiencing the same problems with a drone (takeoff weight over 50 kg) as described in RaMansell’s post. Takeoff, climb, and landing work, but as soon as there is any roll or pitch movement or wind (regardless of flight mode), the drone becomes uncontrollable.
The drone flies stably under Adrupilot. We have transferred the PID values from the Adrupilot parameters to PX4 and set the PID controller factor to K=1.
Are there any other parameters (as MC_ROLLRATE/PITCHRATE_P for a start. So, start with MC_ROLL_P and MC_PITCH_P) that would allow the drone to fly stably and reliably under PX4?
Are there any other tips for heavy lift drones?

(Aluminum frame, 1.5 m x 1.5 m center motor to center motor, MTOW 65 kg, T-Motor Flame 200A HV ESC, Cupe Orange, Here 3+,

Thank you

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Assuming you have worked through?

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