Design and analysis of an underwater vectored thruster employing spherical actuator

Underwater vectored thruster is an important development direction for the propulsion system of autonomous underwater vehicles. However, conventional vectored thruster systems generally consist of multiple actuators and complex transmission structures, which results in large system mass, accumulation of errors and poor dynamic performance. In this paper, a spherical-actuator underwater vectored thruster system (SAUVTS) is proposed to address the issues. The spherical actuator can directly generate 3-DOF motion by electromagnetic direct drive technology, rather than the multiple sets of motors in conventional vectored thruster, which helps to achieve lower system weight, smaller error accumulation and better dynamic performance, simultaneously. The work principle of the proposed SAUVTS is introduced, including its structure, attitude measurement, and control method. An analytical model, defining the mechanical output characteristics, is established, and computational fluid dynamics analysis is implemented to analyze the hydrodynamic characteristics of the SAUVTS. Finally, a research prototype is developed and underwater experiments are carried out. The prototype achieves a dynamic response time of 0.3 s, thereby validating the design concept of the SAUVTS.