Moderator Comment by Chris Anderson on March 9, 2009 at 6:55pm

Very nice! What gain values worked best for you?

Comment by smguest on March 10, 2009 at 5:49am

The settings used for the video -

heading_max 60
heading_min -60

Kp_heading 3
Ki_heading 0.01
Kd_heading 0.05

Background - a friend of mine did put an ArduPilot on his car and learned through experimentation that a heading limit of +/-30 worked fairly well. Looking at what +/-30 did for the Telemaster rudder looked like it might be a reasonable deflection. Flight testing indicated that turning into the wind, it seemed ok, but the downwind turns were so large that I wasn't sure if the airplane was ever going to make it back. I upped the heading limit to +/-60 and on subsequent testing, the airplane would oscillate or "hunt" +/-45 degrees from the desired course going downwind but not as much going into the wind. I then played with the Kd gain, first I tried 0.01, which seemed to dampen out the oscillations, but not completely. I then when I upped it to 0.05 and I got the results indicated in the video. It still overshoots the heading to waypoint 2 but recaptures it pretty well with a single correction.

I couldn't be happier with the results. The airplane flew completely hands off for several circuits of the waypoints. I thought that the altitude hold worked fairly well too. If you watch the video, I did rotate the camera down and you can see how perfectly it overflies the shed and that waypoint was just selected from Google Earth.

Cool stuff - thanks to everyone involved!

Moderator Comment by Chris Anderson on March 10, 2009 at 8:48am

Excellent! Many thanks for sharing that information and the advice on tweaking gains. For our Superstar, +-60 would have been too much, but it's good to know what the right settings are for larger planes.

Comment by smguest on April 25, 2009 at 6:03am

I need to make an update in case anyone else is using a Telemaster. My rudder linkage was very soft in that I didn't realize the pushrod was flexing under a light load. After fixing that, the gains I was using before were way too much and causing a lot of hunting. I'm still dialing in what I think the appropriate gains and deflections shouuld be but I'm zeroing in on the following -

heading_max 45
heading_min -45

Kp_heading 1
Ki_heading 0.01
Kd_heading 0.5

I've flown with 2/.01/.05 (and +/-45 deflection) and it is still too prone to overshoot. So as soon as the winds die down, I'll try out the new gains and post here.

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