A novel 3-DoF piezoelectric robotic pectoral fin: design, simulation, and experimental investigation

Abstract The fish pectoral fins, which play a vital role for fish swimming mobility, can perform three degree-of-freedom movements (rowing, feathering, and flapping motions), promoting that a lot of bionic robotic pectoral fins have been proposed and developed. However, these developed robotic pectoral fins driven by electromagnetic motors or smart materials still cannot fully realize the aforementioned three movement modes. To solve this problem, a novel piezoelectric robotic pectoral fin based on the converse piezoelectric effect and friction drive principle is proposed in this study, to achieve the three motion modes. Using a piezoelectric actuator, the robotic pectoral fin can be driven to move with three degree-of-freedom motion modes. Firstly, the overall structures of the proposed piezoelectric robotic pectoral fin and the designed piezoelectric actuator are explained in detailed. Additionally, a finite element simulation and a combination of vibration measurement and impedance analysis experiments are carried out to verify the effectiveness of the proposed piezoelectric actuator. Finally, an experimental investigation is conducted to evaluate output performances of the robotic pectoral fin prototype. Experimental results indicated that (a) the maximum average velocities of the rowing and flapping motions of the pectoral fin prototype under an excitation voltage of 550 V pp are 290 and 241.7 deg s −1 , respectively, and the maximum rotation speed of the feathering motion is 6.03 deg s −1 ; (b) the maximum output forces of the rowing and flapping motions of the pectoral fin are 2.156 and 2.107 N, respectively; (c) rowing motion start stop response times are 13 and 10.6 ms, flapping motion start and stop response times are 14.2 and 9.2 ms, and feathering motion start/stop response times are 34 and 56.8 ms, respectively.