So I’ve been thinking about a couple of things related to the fixed wing autoland. Basically I’d like to include some of the features that are implemented in Ardupilot or could make the landing very precise even with just a low range sonar.
Ardupilot handles the change in altitude (the “rangefinder bump”) when the distance sensor gets its first reading by steepening/flattening the glide slope. Is there a safety mechanism in PX4 for avoiding possible deep dives near the ground?
What has been my solution for this in PX4 is that the glide slope + flare part are just moved further away if the vehicle is too high when the rangefinder gets its reading. If the moved distance is too high, the vehicle will just abort the landing. What do you think, is this even required?
Possibly a better solution for the pitch control in flare? Now the pitch just seems to be increased to the minimum flare pitch at touchdown. There is an elegant path calculated for the flare (in landingslope.cpp), could this be utilized with the tecs controller?
I think I read that in Ardupilot, if the rangefinder bump can’t be handled (too steep resulting glide slope), the vehicle will abort the landing and save the terrain altitude for the next landing try.
I implemented (3) for PX4 so that the terrain altitude is tracked while landing (while having a valid reading). In case of a go-around, the difference between the actual terrain altitude and the landing altitude setpoint is added to all the following waypoint altitudes. What do you think? Here is the branch: https://github.com/PX4/Firmware/compare/master...almaaro:land-terrain-alt-adjusting