Prop and rudder boat turn in circle in auto and steering mode

Hi, I have a boat with one motor and one rudder. I did radio calibration, accel calibration, level calibration… Manual mode works good.
I know i should tune the acro mode now, but the rudder have really weird behavior in this mode i don’t understand : sometimes the rudder change the direction for no reason. So I tried steering mode and it seems to work. But when i try auto mode, the boat turn in circle and don’t go to the wp. It seems he wants to correct the angle in the wrong direction.
I don’t know what to do now.
Thank you for the help

Forgot to say : I use a pixhawk 4 mini with ardurover firmware and mission planner

Check the following things and see if it solves the problem:

  • you can invert the servo output for the rudder and try auto mode again (because maybe the steering is inverted in your remote and that is why it does the right thing in manual mode)
  • it can have something to do with the orientation settings of the autopilot in the software. is the roll pitch and yaw doing the right movements in the missionplanner “cockpit” when you move the boat around?
  • it can have something to do with the orientation and the location of the Autopilot in your boat…and also if you have a big boat with Metal parts or a big battery or other things that create magnetic fields for example…try to move the autopilot away from these things because the Compass is disturbed by them.
  • is your gps working OK? (for Acro and Auto modes you need a working gps and good signal)
  • if you have a big boat, the steering pid controller values (in mission planner configuration → basic tuning) could be too high…try lowering P, Imax and FF (but not all at once) and see if it changes the behavior
    good luck
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Thank you for your answer.
I already tried to reverse the servo output but same result.
Compass and artificial horizon works great. GPS too

Today I try to put everything on a little wood char just for testings.
What I don’t understand is : why the rudder servo does not move enough in auto or acro and no parameters seems to change this? Why the servo is not moving when the vehicle’s orientation is the opposite of the wp? not logic to me… when I set up a gyro on my old helicopters, we can clearly see the tail rotor moving. why not here?


Any chance you could post an onboard log of the problem? This will give us a lot more detail of what is going on.

I suspect this is the common problem we see with inputs and outputs being reversed. If you use Mission Planner’s motor test feature it should show the problem.

Hi this problem is solved, I needed to adjust the mechanical link between rudder and servo in order to have more resolution.

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