Research On Surface Acoustic Wave Torque Measurement

In order to meet the different needs of industrial applications, a lot of research institutions have been working on the research of new torque sensing technology. Surface acoustic wave technology is popular and emerging technology in recent years, due to its passive and wireless characteristics, it has unique advantages in sensing for temperature, pressure,, stress, torque and so on. Hence, the torque measurement based on surface acoustic wave technology is becoming a new direction of torque sensors research.Firstly, this paper introduces the basic working principle of torque measurement using SAW technology. According to the characteristic of SAW resonator sensor, this paper presents the design of torque sensing shaft and carries out the finite element simulation in COMSOL,analyzing the stress and strain on the working plane of the shaft for sticking sensors. This paper studies the SAW torque sensing mechanism, analyzes the changes of wave equation, elastic constant, substrate density in the effect of initial stress and stain, and then establishes the torque sensing theoretical model. Based on this model, this paper using quartz as the substrate, simulates and optimizes the torque sensitivity, the electromechanical coupling factor and the temperature coefficient of frequency of the SAW torque sensor at different Euler angle cut, which provides a theoretical basis for designing the sensor. This paper also designs two different resonant frequency SAW torque sensors, then computes and optimizes the parameters of the inter-digital transducer and reflectors of the resonator sensors.In order to realize the wireless sensing of the torque, a PCB loop antenna suitable for installing on the shaft is designed, produced and tested with a network analyzer in this paper. According to the test results, impedance match for the loop antenna is optimized by the simulation. Finally a loop antenna meeting the performance requirements is achieved.In the end, a torque test experimental platform is established. In according to the actual manufacture situation and the existing cut of the SAW sensors, this paper chooses the quartz whose Euler angel is(118°,108°,4°) as the substrate and makes the wired experiment of the torque sensors. The test result shows that the sensors have good linearity and repeatability;The sensitivity and coincidence degree are not good. Based on the characteristic of the SAW echo signal, this paper illustrates the processing algorithm of the echo signal. The torque sensors connected with the rod antenna are tested wirelessly while the reader connected with the loop antenna, which verifies the feasibility of SAW technology using for the wireless torque measurement.