Research Of Tyre Pressure Sensor System Based On Surface Transverse Wave

When the traffic accidents become more common, people's expectations for safe driving get even more urgent. The reasons to most of all the accidents are the nonstandard tyre pressure when driving. So it's important to research and invent the 2nd generation of TPMS, which is passive and wireless, to improve the qualities in the harsh environment.There are some stringent requirements as a TMPS with high qualities: high precision, well stability, and can still be used under severe conditions. The paper designed a new tyre pressure sensor system based on surface transverse wave (STW), and the principles of surface acoustic waves and the design process of the sensor are analysed.The outstanding features of this sensor are: one-port STW resonator as the sensor part; equi-intensity cantilever beam used to be the piezoelectric substrate based on (0,38°,90°)-cut quartz; and also an appropriate design of the pressure conductor.A FEM (Finite Element Analysis) analysis tool, ANSYS 11.0, is used to do some static analysis for the cantilever and dynamic analysis for the surface acoustic wave principles. Also the analysis results can be used to improve the design of the sensor to reach a better performance of the whole sensor system.The system is combined with a sensor and the SAW-RFID platform, which is used to stimulate the sensor and interrogate the signals from sensor. The paper also compared some frequency estimation methods using MATLAB simulations, and a FFT+DFT method is chosen to be estimate the frequency offsets, which can worked high precision and well stability.The final experiments' results show that the designed sensor's resonant frequency is 921 MHz, and the pressure sensitivity is 0.65Hz/Pa(65 kHz/bar) in the applied pressure range, and also their relative frequency shift varies linearly with the pressure loading.