Research On The Method Of Driving Deep-sea Robotic Arms With Piezoelectric Actuators

Equipping Autonomous Underwater Vehicles?AUVs?with robotic arms is practical to improve their abilities,and of significant importance to ocean exploration and deep-sea work.The hydraulic underwater robotic arms are too large and heavy for AUVs,especially for mini-AUVs.The underwater robotic arms driven by brushless DC motors are still not able to work properly under high hydraulic pressure.In this work,the method to drive the robotic arms with piezoelectric actuators is studied.Utilizing the merits of piezoelectric actuators such as able to work underwater,having compact structure and easy to be miniaturized,fast response and self-lock,and adopting open-structure design to eliminate the hydraulic pressure problem,a robotic arm is proposed.The main work of this paper are as follows:1.Based on the existing bar-shaped multi-DOF piezoelectric actuators and aimed at solving the stable and easy-adjusting preloading force problem,a novel multi-DOF piezoelectric actuator with a single stator is proposed.A prototype is fabricated then studied.2.Because of lacking feedback devices,it is hard to control the rotational direction of the robotic arm.According to the working principle of robotic arms,a new robotic arm driven by single-DOF piezoelectric actuator is proposed.The joint can be driven to rotate along two vertical axes,and the equipment for adjusting the preloading force is set inside the joint.3.A prototype with two joints and three arms is fabricated and assembled,it is 573 g in weight and412 mm in length.The mechanical characteristics of the robotic arm prototype are investigated by experiments.The results indicate that,when the excitation frequency of one sandwich piezoelectric transducer is 37.4 kHz,the arms on its two sides rotate in opposite directions with an average rotational velocity of 320 deg/s at 330 V_pp,a startup and shutdown response time of 40 ms and 30 ms at 230 V_pp,respectively,a resolution of 100?rad at 230 V_pp,and a output torque of 0.07 N·m at 310 V_pp.The experiments results shows the good characteristics of the robotic arm which indicate its potential to work properly on AUVs.