Research On The Piezoelectric Driving Method Of Underwater Open Robotic Finger

Deep sea manipulators are necessary equipment for marine exploration.The industrial hydraulic deep-sea manipulator has a large volume and the structure of the gripper finger is not dexterous enough,so it is difficult to be applied in small-scale submersible and capture the active marine organisms.The dexterous small-scale underwater manipulator mostly uses the electromagnetic type brush less motor as the actuator,and adopts the oil filling method to balance the sea water pressure.However,with the increase of water depth and the increase of water pressure,the deformation of sealing elements not only leads to the decrease of motor output capacity,but also has the risk of seawater infiltration or oil leakage.This project is aimed at the micro submarine,using the piezoelectric excitation and friction drive principle to build the underwater full-open mechanical fingers.There is no chamber inside the open piezo-actuated underwater robotic finger,and there is no pressure difference between the finger and the seawater.The structure will not be damaged under the high-water pressure environment.It is hoped to eliminate the restriction of deep sea pressure on the mechanical joint drive system.In addition,each mechanical finger joint has two degrees of freedom,and adjacent phalanges can move in two perpendicular planes,and the structure is simple,compact and very dexterous.The main contents of this article include:1.In order to eliminate the chamber of the existing sandwich-type piezoelectric transducer due to the pre-tensioned piezoelectric ceramic plate,a bonded-type piezoelectric transducer with double acting heads for driving a robotic finger is proposed.The bonded-type piezoelectric transducer uses the d₃₁ mode of the piezoelectric ceramic plate to work,and the piezoelectric ceramic plate does not need to be pre-tightened.Compared with the sandwich-type piezoelectric transducer,the volume of bonded-type transducer is smaller and lighter.2.Aiming at the problem of inconsistent output torque caused by different preload pressures at different joint angles,a constant preload application method was proposed.The structure of a bonded-type piezoelectric transducer with double acting heads was optimized.The output torque was increased by amplifying the amplitude of the actuating head,and the weight of the entire mechanical finger was reduced.3.The prototype of the underwater robotic finger was manufactured,with a mass of 83 g and a total length of 220 mm.The working angle range of each joint was-75°to 75°.In order to prevent short circuit of the power supply,the piezoelectric ceramic sheet is insulated and water-proofed.Comparative experiments in water and air show that there is no significant difference in the optimal driving frequency and bandwidth of piezoelectric transducers.Under the conditions of 69 k Hz and450 V_pp,the maximum output torque of mechanical fingers in water environment is reduced by about two-thirds compared with air environment.Although the water environment causes the friction coefficient and thus the maximum output torque of the mechanical fingers to decrease,the stability of the drive system and the service life are expected to be improved due to the lubricating effect of water.