Thruster issue - rotation direction changing randomly

Hi there,

My team just did a major update on our BlueROV2 this year. We upgraded to the Heavy kit and we also replaced the Pixhawk with the new Navigator system. We just went out to test it and our ROV would not go forward or backwards. All other directions seemed to at least go even if they were a little touchy.

Taking it out of the water to do very short tests, we found that when individually testing the thrusters (under the motors tab in QGC) when giving the same command (i.e. forward) sometimes thrusters 3 and 4 would go clockwise and sometimes they would go counterclockwise even when given the same command (i.e. clicking on exactly the same location on the sliders in the motors set up tab).

We have checked and it appears that all of the wiring is correct, and that the connections between the thrusters and the ECS components are good. Further, when doing the motor testing each motor command corresponds to the correct thruster suggesting to us that our issue is not having mis-connected the thrusters to the navigator. We’ve also checked that the propellers are in the right direction and they all appear to be correctly oriented.

I’ve searched through the forums and haven’t been able to find anyone else with the same issue.

That said, has anyone faced a similar problem or does anyone have any further troubleshooting suggestions?

Thanks for your help!


Hi @bhob, welcome to the forum :slight_smile:

A couple of questions to clarify:

  1. Are you certain you didn’t check any of the “Reverse Motor Direction” boxes or run the “Automatic Motor Direction Detection” functionality in between tests?
  2. Is this consistently/statistically reproducible (e.g. it switches direction at least within every N tests)

This would also seem to rule out electrical noise from cross-talk, which I wouldn’t expect to be an issue but is at least physically possible.

Accordingly, if the directions weren’t being changed in the parameters then I’ve got not idea how the motors could change directions for the same input signal, unless you’re running a custom firmware that modifies the outputs, or there’s some hardware issue with your PWM outputs or ESCs (both of which seem unlikely, especially if it’s sometimes working correctly).