Diagnose Automated drone flipping several times in air and crashing


I recently had a crash with the PX4 on a TBS Discovery. I added a 3 axis gimbal to the front of the drone with a GoPro. Since adding the gimbal, the drone has become very sensitive to flight controller inputs in the roll and pitch axis. The drone itself COG is fairly center of the frame with batteries and everything mounted. It is a fairly heavy craft. I programmed an automated flight for it. It took off, and at the 9:12.695 it rolls to the left, and continues to roll around several times until crashing into the ground. Any help as to why it might’ve done this? Thanks!

here’s the log: log file


Where on the vertical axis is the camera mounted? If the CG is higher with the camera addition, then the craft would become more unstable. In this case, the copter acts somewhat like an inverted pendulum. Since it rotates about the CG, moving the CG toward the plane the propellers are in makes the craft sensitive to force imbalances. You could try reducing the gains on pitch and roll to make it less responsive.

Thanks for the reply Jonathan! Yes I did actually raise the COG with the camera, plus the battery being higher. I will mount the battery beneath the craft and report back.

I didn’t adjust the PID settings so I’m concerned they might be off. Would you mind looking at them to see? Thanks!

It’s really hard to tell about the PID gains without having the vehicle on hand or an accurate model. But the main idea is that your gains are too strong with such a high CG. So a small perturbation causes way too strong of a response, resulting in the instability you see.

Try seeing how the craft flies with the new configuration first. If it is still unstable, try reducing the gains.