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Stopping Gradually

Hello, while controlling the thrusters from the pixhawk, the T200s suddenly stop when I suddenly stop the vehicle. For example, when I stop suddenly at the last throttle, the motors suddenly cut off, is there a way to prevent this, I want the motors to stop gradually, not suddenly, will instantaneous movements damage the motors?

Hi @Furkan, welcome to the forum :slight_smile:

Our BasicESCs use the BLHeli_S firmware, which automatically does regenerative braking. Beyond that, the water itself is heavy enough that it would tend to stop the thrusters quite quickly on its own.

Because the motors are brushless and filled with water, and the propellers are light-weight plastic, the main potential issue with a sudden stop due to stopped controls is a spike of backemf. That can cause issues with insufficiently-balanced power supplies but is generally not an issue with battery-powered systems, especially the large capacity batteries that tend to be used in ROVs. If you’re designing a power-over-tether system then it’s something that’s worth considering, specifically with regards to smoothing capacitors and the like, but if you’re using a battery powered vehicle it’s likely a non-issue.

Sudden motor stops are more problematic with robotic actuators in air and/or with large loads. A robot arm that comes to a very sudden stop can cause significant stress in the joints and members because the stopping reaction force needs to go somewhere. For an ROV suspended in water the relatively small reaction from each stopping thruster just dissipates into the surrounding water, whereas something that’s rigidly mounted or has a sufficiently large load that the reaction causes a large tipping action can be much more negatively effected.

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Thanks a lot!

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