Thanks Randy! This is an outdoor flight from today: https://www.youtube.com/watch?v=tsZDdXIjgkM
Understandably the pitch is proving by far the most difficult axis to tune - even with notch filtering on the system instability (25Hz) I’m not able to raise kP or kD high enough to get the tune very crisp. What I’m finding is that I’m having to run quite high kI values to compensate which is causing some unwanted behaviour, especially in dynamic or windy flight.
So next steps are:
- Investigate the use of the feed-forward (ATC_RAT_PIT_FF) to supplement P, as in the heli code
- Convert to Chinook layout, as a good pitch tune is more valuable for the kind of flying I do than a good roll tune.
- Look into changing to an Oblique Active Tilting design (http://www.reports.ias.ac.in/report/21006/stability-and-control-of-vtol-tilt-rotor-bi-copter-uavs), whereby the action of tilting the props forward also imparts a gyroscopic torque on the airframe. I expect the pitch response to benefit quite a bit. A video of an OAT bicopter can be found here: https://www.youtube.com/watch?v=usiaKOpi4kE