The Design And Implementation Of Surface Acoustic Wave Torque Sensing System

The discovery of the new sensitive material and the new principle,the application and development of Micro-electro-mechanical Systems(MEMS)technology,accelerate the transformation of the traditional torque sensors.Because of its passive and wireless characteristic,surface acoustic wave(SAW)technology has become a research hotspot in the fields of the sensing.The torque sensing using SAW technology has become the new direction of the torque testing research,and it is especially suitable for complex and harsh environment which can not be applied by conventional sensing technology.So this thesis studies the SAW torque sensing.Firstly,the sensors of the SAW torque sensing system are designed.Based on the analysis of the principle of the SAW torque sensing,this thesis designs the torque sensing axis and establishes a SAW torque sensing theoretical model which is based on the Lagrangian coordinates and describes strain-induced resonant frequency fields.On the basis of the theoretical model,the piezoelectric substrate cut type is optimized according to the torque coefficient of frequency and the electro-mechanical coupling coefficient.According to the results of the cut type optimization and the principle of frequency division multiple access,four kinds of torque sensors with different resonant frequencies are designed.Then the reader of the SAW torque sensing system is designed.According to the response characteristics of the SAW resonator sensors,the segmented loop antenna and the hardware circuit of the reader are designed.In terms of the static torque measurement,the receiver link of the reader using power detection with the advantages of simple structure is designed,and the sweep scheme is optimized.In order to solve the problem of the dynamic torque measurement,the receiver link using the frequency domain interpolation methods is designed.By comparing the accuracy of the different frequency domain interpolation methods,the third-order spline interpolation is verified as the optimal interpolation method.Finally,the SAW torque sensing system is implemented.The wired testing and torque calibration are performed on the static torque sensing experimental platform.On this basis,the static torque is passive and wireless tested and the results show that the SAW torque sensing system can measure the static torque accurately.Similarly the dynamic torque is passive and wireless tested on the dynamic torque sensing experimental platform and the results show that the SAW torque sensing system can monitor the torque variation.