Research Of The Passive Wireless Tire Pressure Sensor Based On The SAWR And Tire Impedance

With the popularity of cars and the increasing requests of the safety of driving, the requirements for the Tire Pressure Monitoring System (abbreviations: TPMS) are increasing higher and higher. Traditional TPMS usually works in an active sensing approach which has many defects such as battery life, battery chemical pollution etc. It can not meet people's needs gradually any more.Therefore, passive technology for the tire pressure sensor is a trend for TPMS development.Surface Acoustic Wave(abbreviations: SAW)sensors are considered to be the most promising wireless sensor which could take the place of the active device. Therefore, there will be a very important social and economic significance to apply the SAW sensors to the passive-oriented for the tire pressure sensors.In this paper, we used tire impedance as the characterized amount for tire pressure, combined with SAW Resonator (abbreviations: SAWR), proposed a wireless tire pressure sensor based on the tire impedance and SAWR. Different from the traditional SAW sensors that usually add the measured amount directly to its route of transmission, this new sensor first converts the responsive of the tire pressure to the changes of the tire impedance, and then transforms the changes to the frequency changes of the sensor, after which we can measure wirelessly the vary of this frequency to get the initial pressure change. This approach greatly extends the range of the wireless passive of the SAW devices.To sum up, this paper has reached the following conclusions:Firstly,we got the theoretical principle for the following designs for the tire pressure sensors by analyzing and exploring the SAW devices and SAW wireless passive technology, stressing especially on the time-frequency characteristics of the passive wireless external impedance sensors.Secondly,researched the concept of tire impedance, and discus the characterization of the relationships between the tire pressure and the tire impedance,and making the tire impedance as the external impedance of SAW sensor to build the structure of the tire pressure sensors. Work out the specific parameters for each device in the sensor by modeling and analyzing the sensor matching-network, after which the final designs for the passive wireless tire pressure sensor is completed.Finally,making the CycloneⅢas the core processing chip, design and achieve the relevant test system of the passive wireless tire pressure sensors, which mainly consists of RF transceiver and frequency measurement module. After the designs being completed, we test the sensor and analysis the data. The results show that the design of the passive wireless tire pressure sensors based on SAWR and tire impedance can testify the tire pressure in higher precision, which indicates that we have achieved the desired objective of the sensor design.The main innovation research results of the this papers are fellowing:1st. Proposed a wireless tire pressure sensor method based on the tire impedance and SAWR.2nd. Achieved the measurement of high-frequency signal frequency by CycloneⅢFPGA and related peripheral circuits.