Altitude Fluctuation in Missions

When flying a basic mission with constant altitude waypoints, the drone’s altitude erroneously fluctuates several meters. When at a waypoint, the drone climbs to the correct altitude–but while it travels to the next waypoint, it slowly loses altitude. Here’s a snippet from the flight log:


These results have repeated on Pixhawk 1, Pixhawk Cube, PX4 v1.8.2, and PX4 v1.9.2, and different GPSs. The problem doesn’t exist when flying in other auto altitude-controlled modes, and the drone is not under-powered.

Mission:

  • Mission Start - 0m
  • Takeoff - 8m rel to home
  • Waypoint - 8m rel to home, 5sec hold
  • Waypoint - 8m rel to home, 5sec hold
  • Waypoint - 8m rel to home
  • Waypoint - 8m rel to home
  • Waypoint - 8m rel to home
  • Waypoint - 8m rel to home

Video of Flight
Log File Analysis (Flight Review)

Any input is appreciated. Thanks a lot!

I see heavy vibrations. You need to isolate your Flight Controller. https://docs.px4.io/v1.9.0/en/assembly/vibration_isolation.html

Thanks for the suggestion. We tested this a different time with a different aircraft with low vibration levels, but still had the same problem.