A novel U-shaped piezoelectric actuator for underwater robotic finger

In order to reduce the structural complexity of underwater robotic manipulators using electric and hydraulic driving techniques, a novel U-shaped piezoelectric actuator is proposed for underwater robotic finger in this study. Without complicated equipment to protect the piezoelectric actuators from water ingress, the robotic finger can adopt an open configuration in underwater environment, effectively reducing structural complexity. Firstly, the elitist non-dominated sorting genetic algorithm II is used to determine the geometric parameters of the U-shaped piezoelectric actuator, to satisfy a tradeoff between the frequency difference of two operation modes and amplitudes of the piezoelectric actuator. Then prototypes of the U-shaped piezoelectric actuator are manufactured and articulated to construct a robotic finger. Finally, experimental investigation is carried out to evaluate mechanical performances of the robotic finger prototype. Experimental results indicate that the angular velocity and stalling torque of the finger prototype in water are 304 deg s⁻¹ and 13.9 mN · m under an excitation voltage of 500 V_pp, respectively. (paper)