The soaring feature has recently been improved for better stability, usability and performance. These changes are now available in the latest builds from within Mission Planner and will be in future beta and stable releases.
I’ve also added a small feature that isn’t in master yet and needs some testing - automatic learning of the glide polar parameters SOAR_POLAR_CD0 and SOAR_POLAR_B during a still air calibration flight. The method seems to work well in simulation and in early flight tests and should make tuning easier on new aircraft.
This only works if you are flying in still air with the new parameter SOAR_POLAR_LEARN set to 1 (set it to 0 again after the calibration flight). It’s still important to set the wing loading parameter SOAR_POLAR_K first by measuring all up weight and looking up the wing area. 5 seconds of data with zero throttle output, steady airspeed target and roll angle below 10 degrees are needed before any learning is done to minimize noise.
The best way to use this is with the RC switch for SOAR_ENABLE_CH in the middle position and with periods at several different airspeed targets - e.g. see attached plot from a simulated flight. This can be done either in FBWB mode using the throttle stick or in AUTO mode with DO_CHANGE_SPEED mission items - see attached example mission file (don’t load this directly as it’s in Australia!).
After the flight the log items PLRN.CD0 and PLRN.B show the convergence of the estimates, and the parameters SOAR_POLAR_CD0 and SOAR_POLAR_B will be updated to the final values.
CMAC-glidepolar.txt (1.1 KB)
I’m keen to see any logs involving this feature - the firmware builds are here (edited), let me know if you need a different board built.