It must be admitted that ardupilot-Copter-3.4 has been increased greatly, such as the stability of althold and poshold,functions like throwing,etc.So I really want to thank the developers, because you have brought us endless pleasure of DIY and the chance to fly.But there are still some problems not been solved since the open source code using the EKF, maybe.
I found that EKF will go wrong when the quadcopter in high speed flight. I used ardupilot-Copter-3.4 on PixHawk.It shows “pos vert variance” in Mission Planner 1.3.37.I put “hgtVar” of “getVariances(velVar, posVar, hgtVar, magVar, tasVar, offset);” out,I found it’s incredible,sometimes it over than 8.0 .However,it normally less than 0.02 .Another problem is the attitude algorithm can’t work well in high speed(such as 10m/s).
The conditions can be listed as follows.
1.The sensors on quadrotor include accelerometer/gyroscope/barometer/external compass/GPS,set the flight mode to “stabilize”,after take off from ground about 50
meters,play the full pitch joystick to go ahead. When the plane fly away from the home more than 200 meters, set the flight mode to “althold” immediately,the
plane will triumph in the skies,it’s out of control.It’s important to note,sometimes the speed will more than 20(or 25) meters per second.
2.In addition,set the flight mode to “althold”,after take off from ground about 50 meters,play the full pitch joystick to go ahead. When the plane fly away from the home more than 200 meters,the plane will triumph in the skies too.
3.set the flight mode to “stabilize”.After take off from ground about 50 meters,play the pitch joystick to go ahead and keep the speed above 15m/s. When the plane fly away from the home more than 200 meters, play the pitch joystick to go back until the plane close to home.Then repeat such operations for several times, you will find you can’t correct the attitude of the plane by joystick,the attitude angle is bigger and bigger,in worst case, it may be over 80 degrees.
I found that the complementary filter algorithm seems to not have the problem (triumph in the skies) like ardupilot-Copter-3.1-rc8.But the attitude of ardupilot-Copter-3.1-rc8 will still distortion under high speed. I guess the problems are caused by position(height),velocity and attitude estimation error in hight speed.
As you see, my English is poor, please forgive me.
Really need your help!