When I engage Depth Hold, the vertical thrusters run with no vert command from pilot. Even occurs when pressure has been calibrated and the vehicle is not in the water.
The motors will always run in any mode other than MANUAL. The problem is that the ROV is trying to correct the depth, but isn’t moving according to the sensor in air.
Roger. Thanks Jacob
@gcelec, just FYI, this will also happen in Stabilize Mode if the ROV is moved in such a way that the system tries to correct for it. For instance, if you have the ROV in air and you turn it 90deg, it will turn on the thrusters to try to turn back and they will keep running since they can’t actually cause it to turn.
Thanks for the advice Rusty. If I engage Stability Mode while the vehicles on the floor, the thrusters don’t run unless I move the vehicle, which makes sense. I thought that Depth Mode would be the same i.e. the vertical thrusters wouldn’t run until the depth changed, so when they started running as soon as DM was engaged, it didn’t make sense.
There is a ‘ceiling’ for the ROV that exists ~5cm beneath the surface of the water. This prevents the ROV from trying to fly out of the water in depth hold mode. The ROV is trying to get below that ceiling. Besides that, even if the depth is off by a millimeter or the angle off by a fraction of a degree, the ROV will try to fix it. These sorts of tiny errors could be introduced by variation of the sensor readings.
Hi Jacob
You say the Depth hold and stabilises mode should run the vertical thrusters while on deck as the ROV is trying to get 5cm below the surface. Can this be changed in the settings?
For my application, I need the BlueROV on the surface, but would like to keep the heading stabilised as much as possible.
Colin
Hi @ColinS1, welcome to the forum 
This only applies in Depth Hold mode - in Stabilize mode there is no depth stabilisation, so the autopilot’s control systems do not try to modify the depth.
If you want to maintain a particular depth at or near the surface, the SURFACE_DEPTH parameter should help with enabling that.
I may have a problem then, as the vertical thrusters run in stabilised mode?
If I move the ROV, then the lateral thrusters operate as they should.
is there a setting i have wrong?
The vertical thrusters will still run in stabilise if they have pitch and roll contribution factors and the vehicle is detected as not being exactly level - they just won’t be running to consistently push the vehicle down or up. If that’s not the behaviour you’re seeing then you may need to recalibrate your sensors, but per Jacob’s latest response the changes that could trigger that could be from near-negligible fluctuations of the sensor readings.
It is strongly recommended not to use any kind of automated control mode while the vehicle is out of the water, as running the thrusters in air for extended periods can permanently damage them.
Hi Eliot
I have done a re-cal, and yes, it is better now. I will test the system in the water next week.
thank you
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