Optical flow + Sonar ---- velocity close to the ground

ArduCopter Copter 3.5
1

Dear all,
my combination of optical flow and the sonar (SF-20) is working really well.
Theire is only one phenomenon wich I didnt get solved.

As closer I fly to the ground as less max. velocity i´m able to reach.

-65cm max. 0,8 m/s
-100cm max. 1 m/s
-120cm max. 1,5 m/s
-+ 200cm everything seems to be normal

anybody an Idea where I can adjust that?

Wich I also recognized is that the copter accelerate normal but slows down after a moment.

Thanks alot for any help!

2

Yes I confirm the phenomenon , I think that this is related to the scaling of the OF signal , that does not seem to be linear within the EKF

3

Have you got an Idea where to change that?