A novel underwater piezoelectric thruster with one single resonance mode

In this paper, a novel underwater piezoelectric thruster with one single resonance mode is proposed. The piezoelectric thruster consists of one piezoelectric transducer and two propellers. In order to relieve the bulky problem of underwater thrusters using a DC motor as the power source, the piezoelectric thruster adopts a full-open structure; thus, the piezoelectric thruster does not need additional sealing elements. Compared with underwater thrusters using a DC motor, the piezoelectric thruster has advantages of simple structure and small volume. By using piezoelectric ceramics, the first-order longitudinal mode of the transducer is excited to drive two propellers rotating in opposite directions. A prototype of the piezoelectric thruster is fabricated and experimentally investigated; it is 22 g in weight and 124 mm in length. The experimental results indicate that when the excitation voltage of the piezoelectric transducer is 300 V_pp, the rotational speed of the positive propeller is up to 1267 rpm and the stall torque is 1.71 mN m; meanwhile, the rotation speed of the negative propeller is up to 1203 rpm, and the stall torque is 1.75 mN m. When the piezoelectric thruster is working underwater, the average forward speed reaches 106.01 mm/s at 400 V_pp.