[Paparazzi-devel] Constant ground speed and altitude control

[Rokas Adiklis]

Good evening,

I'm trying to figure out two things:

1. how to set up constant ground speed?
2. how to make it decrease altitude with pitch and without decreasing throttle?

The reasons for this is that I need to fly reasonably far distance (~8 km) forth and back, while having pretty high wind (~9m/s). While at wide throttle (70%) and Auto 1 mode it does pretty well, but in Auto 2 it wobles around like a snake and does not go straight. I have noticed, that it usually flies 15-25 meters above target altitude (it has non-symetrical wing with rather good lift). When this happens, it holds lower throttle to decrease altitude, but then there is not enough thrust to keep it stable and it starts to fight with incoming wind. When I command to shift desired altitude +30 meters, it instantly adds throttle, climbs these ~30m and decreases throttle to a low value again (as it is too high again). When I changed the navigation mode to constant throttle, it was rathe stable against wind, however the altitude was not controlled, and the plane was constantly going up. 

What shoud I do, to configure minimal throttle and (pitch-based) altitude control at the same time? I've google out something about "pitch_of_vz" parameter. Could it help it given situation?

Also, is it possible to set constant ground speed? I'm trying to searched the archives, but just don't seem to be able to find the solution (or don't realize to have found one).

Thanks in advance for any help or hint!

Rokas