Research On Ultrasonic Motor Technology For Driving Micro Underwater Robot

As a new concept of motor,ultrasonic motor(USM)based on piezoelectric functional materials has many unique advantages,such as fast response,self-locking,compact structure,and electromagnetic compatibility.It has broad applications in many areas such as aerospace,optical imaging system,precision control and weapon systems.In recent years,the successful application of the ultrasonic motors in Chang’e series space probes designed by NUAA fills in the blank of the ultrasonic motor technology in the field of aerospace in China.Based on the successful experience of USM in aerospace,the research of ultrasonic motor applied in deep water environment is carried out to solve the reliability and safety problems of existing underwater robots in deep water environment.Up to now,the current research on the application of USM in underwater has just started,including a few native ultrasonic motor research teams.Although some achievements have been made,there are still many key technical problems needing to be solved.The objective of this research is to design ultrasonic motor driving the micro underwater vehicles in deep water environment.In this paper,several novel ultrasonic motors are proposed and a transfer matrix model of ultrasonic motor is built up.Meanwhile,a new type of underwater propeller is designed and the corresponding design of spherical underwater vehicle under multiple working modes is conducted.The special requirements for the structure design of the ultrasonic motor in the underwater environment are clarified,which provides a reference for the design and use of the ultrasonic motor in the underwater environment,and provides a new idea for the development of a new generation of high-performance micro underwater robot.The major contents and achievements are as follows:1.Based on the purpose of simplifying the structure of the ultrasonic motor and increasing the rotation speed of the motor,two kinds of micro ultrasonic motors are proposed.The principle verification and experiments are carried out on them respectively.The purpose of the novel structure design is to overcome the shortcomings of the traditional ultrasonic motor,such as small amplitude of the stator and low speed of the motor.Finally,the prototype motors are manufactured and assembled.Besides,the output performances of the prototype motors are tested through a series of characteristic experiments.2.According to the classical transfer matrix method,the transfer equations of radial vibration and torsional vibration of the ring elastomer are established.Combined with the piezoelectric constitutive equation,the electromechanical coupling dynamic model for the ring piezoelectric element is built up based on radial vibration and torsional vibration respectively.Then,the mechanical and electrical coupling dynamic model based on radial vibration is established by using transfer matrix method.3.Focusing on the proposed novel mode conversion ultrasonic motor,the vibration transfer equation of each element of stator structure,the connection conditions between adjacent elements and the boundary conditions of piezoelectric system are defined by using the transfer matrix method.Combined with the proposed dynamic modeling method,the electromechanical coupling dynamic model of the motor is established.Finally,the reliability of the theoretical model is verified through the relevant experiments.4.A micro underwater propeller based on ultrasonic motor drive is firstly proposed.Then,the finite element model of the propeller is established with the aid of the finite element software and the influence of the underwater environment on the vibration characteristics is analyzed,including the influence on the resonant frequency and amplitude of the stator,and the displacement time response of the driving surface particle.The results show that the influence of the underwater environment on the characteristic frequency of the stator is smaller than that on the amplitude of the stator.The characteristic frequency of the stator in the working mode is reduced by 1.99 k Hz(2.62%),and the amplitude is reduced by 4.1μm(35.3%).The results of underwater experiments show that the resonance frequency of the propeller is 2.4 k Hz lower than that in the air(the decrease range is 3.12%),and the maximum underwater speed of the propeller is 1200 r/ min.5.A spherical underwater vehicle model is proposed with a new propeller used as the power device.Then,the electromagnetic field is applied to reconstruct the structure of different robot models and a series of underwater actions are completed through certain control strategies.The results of underwater experiments show that the maximum moving speed of the robot unit model is 80 mm/s and the maximum thrust is 4.6 m N.After combing the several element models through electromagnetic field,different motion modes such as underwater U-shaped trajectory swimming,hovering,rising,diving and straight-line swimming are realized based on certain control strategies.