Roll stability issues

I am using the BlueRobotics advanced electronics package, but my own frame and 3D printed thrusters. Just starting water testing and in manual all works well, in every direction.
When selecting stabilised mode, if the vehicle is disturbed a rocking motion starts, up to 10 degrees each way. Of course this happens in depth mode as well, but it does hold the depth exactly!
Any ideas?


I believe roll is disabled: Below is from another forum topic. It may help:

Roll trim will require active roll stabilization to be turned on. We disable active roll stabilization by default in order to conserve battery. To enable it, find the ATC_ANG_RLL_P parameter in the Parameters tab of the Vehicle Setup page. Set it to 6.0, and the ROV will actively try to maintain a level angle. Decreasing the value will make the ROV put less effort into maintaining a level angle.

I use the value of 6, and it works well.

Thanks, I will give it a try.

Terry Eglinton

Terry, can you show us what your vehicle looks like? You can adjust the gains for attitude control with the ATC_* parameters.


Here is a picture of its first trial. To give a sense of scale it is 340mm wide. The origin brief was to build an ROV that would fit down a well!

Hi @Teggles,

This could be caused by a few things that I can think of. If you can take a video of the oscillations that would be really helpful to diagnose this. Here are a few thoughts:

  1. The thrusters could be reversed (left/right swapped). That would still depth hold but oscillate in roll. It would probably be pretty dramatic if this happened.

  2. Since you have a different frame, the PID control values may have to be adjusted. As Ken mentioned, the ATC_ANG_RLL_P value changes the leveling strength, but the ATC_RAT_RLL_* values change the rate of roll. Change those will help to “damp” the system. I would start by adjusting ATC_RAT_RLL_P down a little bit.

Hope this helps! Let us know what happens.


Thanks Rusty, I will give it a try.