Near-field Acoustic Levitation Transportation Characteristics Analysis And Experimental Study Of An Ultrasonic Motor

The surface of precision component is very fragile and easily damaged during processing and transportation.Traditional contact processing and transportation methods which use surface friction to fix objects and then transmit,which can no longer satisfy the requirements of precision component in processing and transportation.Near-field Acoustic Levitation(NFAL)is a technology with huge application prospects in the field of precision machining and manufacturing.It has the advantages of non-contact,no pollution and no noise.Based on the principle of NFAL,this paper studies the levitation and transportation characteristics of uneven matters in NFAL.Besides,A non-contact ultrasonic motor is designed based on NFAL principle and experimental study was conducted.The details are as follows:(1)Based on fluid lubrication theory,a theoretical model of near-field acoustic levitation and transportation for uneven matters is established.Based on the NavierStokes equation and combined some assumptions in fluid lubrication,the Reynolds equation is derived;the gas film thickness equation is established and the initial conditions and boundary conditions are given;the motion model of the levitated object is established by analyzing the force of the object and the motion equation is given.Reynolds equation and motion equation are then nondimensionalized.The Finite Difference Method is used to discretize the dimensionless Reynolds equation and the Newton–Raphson method is used to linearise the discreted Reynolds equation.The calculation program written by MATLAB is used to solve the Reynolds equation and obtain the air pressure distribution.By integrating the air pressure distribution in the solution area,the distribution of the squeeze film force is obtained.By combining the equation of motion,the levitation process and transportation process are obtained.(2)The ANSYS finite element analysis was used to design the vibration rail for near-field acoustic levitation and transportation,which mainly included the design of vibration mode and vibration frequency.The vibration amplitude and frequency of the ultrasonic vibrator were measured to provide a basis for the design parameters of the vibration rail.A experiment platform was built,and the experimental vibration mode and vibration frequency of the vibration rail were measured and compared with the calculation.The levitation height,air pressure distribution,levitation deflection angle,thrust and transportation speed during the levitation process were theoretically analyzed based on the theoretical model;the transportation speed was measured and compared with the theoretical calculation for verification.(3)A non-contact ultrasonic motor based on near-field acoustic levitation is designed.The structure of the ultrasonic motor is designed,and the driving mod e and driving frequency are designed by using ABAQUS;A experimental platform is built for testing the performance,and the actual driving mode and driving frequenc y of the ultrasonic motor are measured through experiments,and the relationship between surface amplitude and driving voltage ar e measured.The effects of driving voltage and load on the load-bearing characteristics of ultrasonic motors,the influence of driving voltage and load on continuous changes in speed,and the influence of driving voltage and drive frequency on stable speed are all studied through experiments.