A novel structural–functional integration piezoelectric thruster for miniature unmanned underwater vehicles

Unmanned underwater vehicles (UUVs) play a vital role in marine exploration, and can achieve an extension of human hands and eyes to help researchers reach inaccessible and complex underwater spaces. However, the developed UUVs are driven by electromagnetic motors that also make it difficult to miniaturize due to the existence of the transmission system. Additionally, electromagnetic motors need to be protected to against water intrusion, especially in the deep sea. Therefore, in order to solve the above-mentioned problems, a novel structure-functional integration piezoelectric thruster for miniature UUVs is proposed in this study. Based on the converse piezoelectric effect and the direct friction drive principle, rudders and propellers can be alternately driven by a piezoelectric actuator, constructing the thrust unit and the steering unit of the piezoelectric thruster, respectively. Therefore, this makes the structure and function of the piezoelectric thruster integrated. Finite element simulations are first conducted to determine the geometrical sizes of the proposed actuator. The efficiency of the designed piezoelectric actuator is then confirmed using an underwater vibration measurement. Finally, experimental evaluations of the output performance of the piezoelectric thruster are performed. In the propulsion mode, the maximum rotation speed and thrust of the positive and negative propeller of the prototype with an excitation voltage of 600 Vpp were 404 rpm/0.10 N and 413 rpm/0.11 N, respectively. In the cooperative working mode, 20.00 kHz was used as the driving frequency, and the yaw and pitch rudders had the maximum average angle velocities of 92 deg s−1 and 90 deg s−1 for an excitation voltage of 600 Vpp, respectively. The maximum rotation speed and thrust of the positive and negative propellers of the prototype with an excitation voltage of 600 Vpp were 133 rpm/0.01 N and 132 rpm/0.01 N, respectively. According to experimental findings, the prototype piezoelectric thruster exhibits excellent mechanical properties.