Motor saturation causing loss of control?

ArduPlane VTOL Plane
1

My plane is a QuadPlane tailsitter - a flying wing with no control surfaces, so it relies on motor thrust for all controls.

The plane hovers well and transitions to horizontal flight smoothly, but in Auto missions it always loses control immediately after transition and starts to fly erratically. Inspecting the logs reveals that this loss of control is accompanied by motor saturation - with all 4 motors clipping at 100% throttle. See example log below.

Why are my motors saturating after transition? I’ve tried commanding a range of airspeeds between 20mph to 40mph with no success. I’m new to tuning so I’d appreciate any insight I can get.

Servo output screenshot:

servos
servos1920×623 268 KB

Flight log and param file: quad-tailsitter - Google Drive

2
  1. You have ARMING_CHECK set to 0 which disables all arming checks this is not recommended.
  2. Your TRIM_THROTTLE is set very high leaving little margin for control.
  3. Your vehicle is practically unable to reach attitude suitable for horizontal flight.
  4. Your airspeed is unreliable as the vehicle is at very high angle of attack, meaning high throttle is comaned.

PS you should not be testing using AUTO mode.

1 Like
3

Thanks for the feedback.

Can you explain #3? The plane has plenty of thrust to climb vertically before transition - around 2:1 thrust to weight ratio.

For #4, what’s the recommended approach for using airspeed sensors? AoA will vary throughout the flight, especially when flying slow.

4

Not really, tailsitters aren’t my department. I would suspect negative stability, especially at high AoA.