Abstract: Quasi-cavitation is caused by the vortex formed between the propeller and water surface when the propeller rotates at high speed near the water surface, which leads to a great reduction of thruster's efficiency, thrust loss and noise. As the only power source of most underwater vehicles, quasi-cavitation on the thruster will significantly decrease the stability of motion control. A novel approach for thrust prediction of underwater blade-propeller-type thrusters under quasi-cavitation is proposed, which can realize thrust prediction with high accuracy. The mechanism of quasi-cavitation is introduced and revealed. A Bayesian estimation based thrust model (BETM) is established to perform accurate thrust prediction without quasi-cavitation. On this basis, a quasi-cavitation thrust model based on Gaussian process (QCTM-GP) is proposed, which utilizes BETM and error compensation based on Gaussian process to complete the prediction of quasi-cavitation. The accuracy and validity of the proposed prediction model are verified via experiments. QCTM-GP lays a foundation for the high accurate motion control of underwater vehicles near surface.

Key words: underwater blade-propeller-type thruster, quasi-cavitation, thrust prediction, Bayesian estimation, Gaussian process