Using High Frequency injection for Better Control of Underwater Propellers at Low Speed and StartUp

[MarcoMota]

Hi everyone,

I was wondering if anyone has ever done tests with high-frequency injection techniques to underwater motors to improve a motor’s current and speed behaviour at low speeds.

I am under the impression that High-Frequency Injection (HFI) with PMSM or Brushless motors can drastically improve low-speed control and startup precision, which is usually a weak spot for sensorless algorithms. (btw, does anyone know the algorithm used by normal underwater ESC?).

Some benefits of using this advanced control solution for a ROV could be:

Reliable control from zero speed (no need to hit 10-20% nominal speed like typical sensorless systems).
Reduced Rotating starting current = better energy efficiency.
Improving precise ROV movements in tight or challenging underwater environments.

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I’ve been doing some background evaluations using MotorBench for the dsPIC33CK DIM for Motor Control and have seen some interesting results (I was able to confirm that with some, not all, brushless motors, this is achievable).

Would love to hear if anyone’s tried this approach or has thoughts on improving underwater propulsion systems.

To have success it seems that this rule must be satisfied:

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