Study Of Indrect TPMS Based On OBD Informationof Vehicle

Puncture is an important factor endangers traffic safety, and the one of main reasons for tire blow-out is tire overworking under insufficient pressure. Tire Pressure Monitoring System(TPMS) can monitor the pressure of tires in real time in the driving process of automobile, automatically alarm the driver to take reasonable measures when it monitoring a tire in an abnormal pressure. So it helps the driver to improve driving safety.TPMS has direct and indirect two types. Among them, the indirect type, which has features of install easily, long life and low price, is more easily recognized by the majority of vehicle manufacturers. The key technology of indirect TPMS is to collect wheel speed signals, select processing methods of the signals and obtain parameter signals which related to tire pressure. The method of reading out wheel speed signal data from ABS and other relevant data through OBD interface, not only are workload of signal acquisition and processing of signals reducing, but also are vehicle condition and road conditions adding, making the tire pressure monitoring system working more accurately.According to the analysis of relations between the wheels rolling radius and the wheel speed signal data from ABS system, this paper established demonstrated the rationality of the indirect monitor tire pressure using the method by comparing the cumulative value of the number of kilometers pulses and wheel speed(turning angle of wheel). This paper established the algorithm model of indirect TPMS, processed the handle for tire calibration alarm threshold calibration, took out the invalid data based on recognition of vehicle and road condition, introduced a standardized conduct, cumulative segmentation method and three-average co MParison method for processing wheel speed signal data, developed the classification criterion to distinguish the speed of gas shortage, to ensure the stability, accuracy and reliability of the entire indirect tire pressure monitoring system.The PCB of TPMS was designed and made according to the above principles, so did proofing and patch, prototype trial-production of TPMS are completed. It is make the functions of data acquisition, processing algorithms and alarm output come true that the design of the software based on the chip of ARM Cortex-M3. The prototype trial- production conducted three road tests of tire calibration, alarm thresholds calibration and TPMS system functions. Many real vehicle tests on road show that the system performed well, it can alarm timely and accurately, the false positive rate and false negative rates are low.