Surface Elastic Bo Mada Research And Design

Surface acoustic wave (SAW) motor is a novel micro actuator,which generates SAW with the electroacoustic transducer and transfers it to the power of SAW motor by the frictional force between the slider and the stator. It overcomes the disadvantages of the other actuators,and has the advantages of high speed,big driving force,small step size and fast response. It is a very promising micro actuator. In this thesis,the technology of SAW motor is studied on the aspects of the theories,simulations and experiments. The main achievements are concluded in the following paragraphs.The elastic wave equations and the boundary conditions of SAW in different media are studied,and the behaviors of SAW in the isotropic,anisotropic and piezoelectric media are fully discussed. The effectivity of the approximation of Rayleigh wave in semi-infinite media to the plane mode in the stator transducer of SAW motor with finite thickness (much bigger than the wavelength of the SAW) is evaluated first time by us.Three possible contact driving mechanisms of SAW motor are discussed,and the frictional drive of SAW motor is shown by the linear relation between the speed of the slider and the driving voltage. The motion model of SAW motor is set up by the formulae of Hertz's theory and Coulomb's friction law. The transient responses of SAW motor under different working conditions are simulated by the Euler method,and many factor that affect the motion of the SAW motor are introduced.On the 128 degrees rotated,y-cut and x-propagation substrate of LiNbO3,the interdigital SAW transducer of 400um in electrode pitch and 100um in electrode strip is designed and fabricated by the technique of photolithography. The input impedance of the interdigital SAW transducer is measured by the equivalent circuit method. The experimental results show that the synchronized frequency of 9.586 MHz,the acoustic radiation resistance of 44.6 and the static electrode capacity of 194pF all agree with those design values.The method of using the tip of atomic force microscopy and beam-deflection to on-line detect the nanometer vibration of the particle in the SAW is introduced,and the SAW amplitude of 6.7 nm is measured when a driving voltage of 3.5 V is applied.The RF power amplifier and mechanical system of SAW motor is fabricated,anda SAW motor is developed successfully. The average speed of SAW motor of 20 mm /S is measured under a diving voltage of 80 V (the peak-to-peak amplitude) by the method of measuring the speed with a digital camera.