Hi- I'm a new (noob) Ardupilot user (just installed the V2 purple kit in a Sky Surfer) and I'm having an issue with the stabilize mode. I set the plane up on a bench stand (everything level), let the board boot up (I let it sit for a few minutes) and flipped the switch on my tx to stabilize. The ailerons stayed level but the elevator went up about 15 degrees. What the heck am I doing wrong? Moving the plane manually on all 3 axis causes the control surfaces to move in the proper direction, but the elevator is still deflected up higher than it should be. The RTL mode works great with nice lazy circles about 200 or so feet above me.
Try clicking the "Level" button in the MP config screen.
I did that a few times already. I just reinstalled the firmware/ started over and now it works. I think the problem was I uploaded the Bixler parameters and that made things goofy.
Here's what was probably happening:
The controllers that ardupilot uses to control pitch and roll are called proportional-integral-derivative (PID) controllers. They have 4 tunable parameters:
Proportional (P): how much the control surface deflects for a given angle error. Angle error is in centidegrees, control surface is between -4500 and 4500. So, with P gain 1.0, you will get full elevator deflection when the pitch is off by 45 degrees.
Integral (I): There is an integrator (just a stored number) which is added to the control surface output. This gain determines how much is added to that integrator every second for a given error. This is likely where you had trouble. Even with the smallest error, the integrator will keep slowly pushing the elevator up, trying to get rid of the error. Thus, you had a steady deflection on your elevator.
Integrator limit (IMAX): Maximum value of the integrator, so if you set this to 5 in the mission planner, it will limit the integrator to 5 degrees of deflection.
Derivative (D): This gain adds deflection based on rate of change in your angle. So if there's a sudden disturbance, it will react instantly to it. This also acts to kind of slow the whole loop down, since it adds opposite deflection when the other gains are trying to do things.
OK- I'm starting to figure it out. Thanks for the response.