I am currently facing dynamic stability issues while designing a new model. On doing manual calculations to find the resultant moment acting on C.B, we are getting high pitch value during the surge motion probably due to lower C.G - C.B distance and righting moment. Nevertheless, the values seem pretty unrealistic.
Is there any record of data/ manual calculation of Blue ROV that we could use as reference data to verify our results.? If any thumb rule that should be kept in mind while designing to maintain dynamic stability is available, would you please share it?
I don’t think we have any data for the BlueROV2 that we can share but I can give some general pointers.
Having a large distance between the center of gravity (low) and center of buoyancy (high) will increase static stability and the tendency to float upright.
The thrusters will act around the center of gravity and should ideally be in line with the center of gravity.
Drag is significant underwater, so you generally want an even amount of drag from top/bottom, left/right, front/back so that the ROV doesn’t rotate when it’s moving.
It is really hard to balance these things perfectly, especially when you want to have flexibility to expand the vehicle and add payloads. For this reason, we also rely on feedback stability control from the onboard controller to keep the vehicle stabilized.