Research On Algorithm Of Indirect TPMS Based On Statistics Of Wheel Speed Extremum

Indirect tire pressure monitoring system is based on the negative correlation relationship between the tire pressure and wheel speed,the signal measured by speed sensor is used to analyse and determine the abnormal tire pressure. It can make an alarm when the tire pressure is abnormal to protect the vehicle’s safety, ride comfort and feul economy.The system has some shortcomings, for example, judgment about the tire pressure made by the system needs a certain time to accumulate the wheel speed signals,so it takes a long period to make an alarm; the wheel speed has a great impact on the stability of the alarm system, when the vehicle is attached low road, it is prone to slip, easily causing false alarms or alarm leakage. The traditional indirect tire pressure monitoring system has some shortcomings on the alarm time and stability. So this paper presents a new algorithm based on extreme value statistics, when the vehicle slips, it can use slip rate to make a correction to the wheel speed, and it can make a rapid alarm when air shortage is serious. The main contents are as follows:Firstly, the relationship between the wheel speed and the tire pressure is analyzed to provide wheel speed extremum statistics. Calculate the number of extremum appears of each wheel speed over a period of time, and perform the tire pressure identification. Analysis the required basic parameters in the process of tire pressure identification and the calculation method of the basic parameters including the wheel speed.Then design the wheel speed acquisition circuit and wheel speed sensor selection, select microcontroller system, and design the wheel speed processing circuit, power circuit and CAN communication circuit.And then design the wheel speed calibration and correction method, judge the wheel speed under the same standard. Design the standard alarm mode and quick alarm mode, when the tires lack the less gas, go into the standard alarm mode, when the tire lack gas seriously, go into the fast alarm mode, it can alarm within short time and distance.Finally, collect the wheel speed data under different speeds and different tire pressure when the vehicles running in low attached pavement, using the wheel speed extremum statistics to verify the effect of the method.Through the analysis of experimental data,the method in this paper works well,it can improve the stability of the system when it is at low attached road. When the tire pressure is low,it is possible to achieve rapid alarm,effectively improve the indirect tire pressure monitoring system’s situation as alarm slowly and easily affected by road condition.