I flew my 3DR-B tonight in startlingly windless conditions. It was the first time I've really tried to test Loiter. I got the quad into a nice stable hover (it was hovering practically dead still in these conditions with no control input at all) and flipped to LOITER. It did a pretty good job of staying in place but started to sort of orbit around the spot it started in. These orbits slowly got wider, to the point where I got uncomfortable and switched back to stabilize, though it took a minute or so.
Is this normal? Do I need to tune my LOITER PID? I noticed that the simulator has a default LOITER D of 0 while the default for Arducopter is 0.4. Changing the sim to 0.4 seemed to make it oscillate more in windless conditions, so maybe the answer is to change my D to 0? But will that negatively effect performance in windy conditions?
Here's my log from tonight: 2012-07-09%2023-07%202.log
Thanks for any advice.
Replies
hi,
i've just install 2.9 rc2 on my apm2.5. i have just tried loiter in stock pids, and i see quite oscilations.
since i'm a noob, i need advice in which PID i should tune ? attached is my loiter log and param.
2013-01-11 06-25 1.log
my_param.param
I had some success with reducing the loiter P, I got it to the point where my loiter would stay within a 5m box or so.
Then I got the ublox GPS, which is worlds better in terms of locking on quickly and getting a higher satellite count / lower hdop. However when I did some loiter tests I got a very strange result where the quad started an expanding spiral that rapidly got out of control. Anyone know why this would happen? I haven't had much time to play with it.
Logs from the incident I'm referring to are attached.
Thanks
2012-08-23 23-32 3.log
2012-08-23 23-32 3.kmz
I found that with my small quads it works best to reduce Loiter P to 0.2 and Loiter I to 0.05. It also seems to make a difference when I change Nav P to 0.9 and Nav I to 0.05. Finally got Loiter and waypoint flying OK in wind with purple motors, 10x4.7 APC props, 1250g weight and motors on 570mm pitch diameter.
Problem I have though is that when I fly waypoints and choose Loiter turns, it goes into a 45deg bank and drops out of the sky when it starts executing the command. Any suggestions please?
What your seeing is lag in your GPS input being too much for the rate_P value you have. Try lowering loiter rate P.
The reason it's jumping out of a perfect loiter is the GPS hits a threshold and makes the quad think it's traveling faster than it is. it over-corrects with the High gain and you start an oscillation.
Jason
What version of the code?