Development Of Deep-sea Resonant Sandwich Linear Ultrasonic Motor

The important task of marine engineering is exploration and exploitation of the rich metal composite ore and petroleum res ources in deep sea.Deep-sea biological diversity and geological structure is scientific research object.At the same time,the deep-sea environment,which is low temperature and brightness,is extremely harsh,so the working reliability and the seal of components of deep-sea actuator are hardly assured.A shell-mounted motor,a motor or hydraulic system with a pressure or compensation mechanism are solutions for traditional actuator,which leads to the huge and heavy system,complicated structures and low working reliability.Properties of smart actuators used in underwater robot are not perfect and the research on smart material is at the initial stage,which can not be applied to project.As the underwater transducer can work in the deep-sea environment,resonant ultrasonic motor,whose working principle is the same as the underwater transducer should have the ability.Resonant ultrasonic motor convert electrical signals into micron-level vibration by the converse piezoelectric effect of piezoelectric mate rials,the stator and the rotor convert micron-level vibration into macroscopic motion by friction.Piezoelectric actuator,with its fast response speed,robust structure,low speed and high torque as well as nonuse of bearings and lubrication,can be appl ied to deep-sea environment.The thesis designed a deep-sea resonant sandwich linear piezoelectric actuator,which could be assembled to actuating mechanism directly.Ultrasonic motor,which was different from traditional actuators,could bring out linear driving effect directly without integral sealing device,because piezoelectric ceramic and metal could withstand more than 300 MPa pressure.The project left out the design of the compressive cabin,dynamic sealing,transmission mechanism and pressure compensation device under the premise of ensuring normal operation of the actuator,which simplifies the overall structure of the actuator and improves the power weight ratio and working reliability of the actuator.In this thesis,a sandwich linear ultrasonic motor using longitudinal and bending hybrid modes was designed,which using the d 33 operating mode of the PZT.Firstly,the structure of the USM was designed,which was symmetrical,and the driving foot was in the center position.The arrangement and polarization direction of the piezoelectric ceramics were analyzed.Piezoelectric ceramics were designed as square and the bending ceramics were designed as two halves of ceramic in the opposite polarization direction while each pair of longitudinal ceramics was in the opposite polarization direction.Then the actuating principle of the USM was analyzed and the exciting method was determined.Then the equivalent circuit model of the USM was established and the formula of the model parameters was obtained,which provides theoretical support for the subsequent experimental part.In this thesis,the finite element parametric model of the longitudinal and bending hybrid sandwich linear ultrasonic motor in the air was established by ANSYS software.Then the fifth order bending vibration mode and the second order longitudinal vibration mode were obtained by modal analysis,and the resonant frequency were calculated to be about 30 k Hz by adjusting the structure parameters.So the optimal structure parameters were determi ned.Then the finite element parametric model of the USM under the water was established by ANSYS software.The required vibration mode was obtained by wet modal analysis,and the final structure parameters w ere obtained after adjusting the structure parameters to get the resonant frequency.According to the structure of the piezoelectric vibrator,the overall of the USM was designed and the experimental prototype was fabricated.The deep-sea high pressure simulation experiment platform was built.The vibra tion modes and the resonant frequency were obtained by the laser vibrometer in modal vibration shape test.The impedance-frequency curves were measured by impedance analyzer in impedance characteristics test and the electromechanical coupling characteristics of the two USMs was researched.The experiment platform was built to test the mechanical output characteristics of the ultrasonic motor in the air and under the water.