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First Ardupilot test flights with some strange behaviour

Posted by Magnus on April 30, 2010 at 5:17am
Today i made my first testflights with my Ardupilot setup. It almost worked...

The setup:
* The plane is a high wing aileron trainer with a 160 cm span and lots of wing area. Very stable.
* Ardupilot running ver. 25_04.
* No shield.
* x,y and Z sensor from paparazzi
* Telemetry downlink
* u-Blox GPS

Flight preparations:
The first thing i noticed was that the software didn't follow the startup routine in the manual:
(I'm not using throttle at this time)
  1. Power on  CHECK
  2. Check the Remove Before Fly plug is connected CHECK
  3. Twitch servos to indicated startup has begun CHECK
  4. Record Radio Trims to memory CHECK
  5. Begin looking for a GPS fix - Flash the blue LED until a fix CHECK
  6. Set the Blue LED to solid to indicate a GPS fix CHECK
  7. Twitch servos once CHECK
  8. Calibrate Radio Min and Max (and optionally XY IR sensors) How is this done?
  9. Twitch servos until Remove before Fly pin is removed Did not work
  10. Save home location and flight settings to memory CHECK
Another thing i noticed was that the yellow LED never blinked at all.

This didn't discourage me from taking off to do some test flights. I had uploaded a few waypoints but the first flight was made with RTL and STABILIZE modes available.

First flight
STABILIZE worked perfect. Flying with it enabled was no problem and it recovered from quite steep angles without to much oscillation.

RTL. This is where the problem started. The plane tries to fly away from home. Its doing steep turns away from home alternating left and right. My first thought was that i didn't store a home position and that the plane was oscillating away.  I decided to test AUTO mode instead.

Second Flight:
I auto mode i experienced exactly the same behavior. The plane tried to reach the waypoint by turning away from it. when flying in the opposite direction it started to oscillate with 40 degree turns left and right.

Summary:
I am not sure what went wrong, but it seems like the AP is trying to turn the plane but it banks in the wrong direction. I have looked in mu Setup file but it looks OK.

When looking at the plane from behind and rolling it, which way should be positive angles. Clockwise or counter clockwise?

Any other ideas what went wrong?


Regards

Magnus


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Replies

  • Developer
    Doug Weibel September 1, 2010 at 4:51pm
    @Florin - Only if you had really done a bad job choosing the gain values could the cross track correction "overpower" the homing calculation. We run a PID loop on error between the ground course and the course to the waypoint, and then add in a track following component. I think it would be possible to set up the gain values so that it would go the opposite direction, but you would almost have to deliberately choose them to do that.

    Start with P gain for the nav loop with no I or D gain, and no crosstrack gain. That will get you started. Tune for optimal performance, then start adding the other gains.

    I should add that it is possible to mis-configure the hardware so that it will always fly the opposite direction, or try to fly upside down, or other amusing things ;)
  • 3D Robotics
    Chris Anderson April 30, 2010 at 7:36am
    Three suggestions.

    --Upgrade to the latest software (now 2.6)
    --If that doesn't help, please try with throttle connected (jumper wires soldered)
    --If that doesn't do it, please upload your config file and I'll take a look.
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