Study On Tire Pressure Monitoring Technology Based On The Estimation Theory Of Tire Longitudinal Stiffness

When a car is running at a high speed, tire blowout is one of the main reasons of the malignant traffic accidents. Running at a high speed for long hours under abnormal pressure, particularly low pressure, is the most primary cause of tire blowout. The key point of avoiding tire blowout is to keep normal pressure and detect the leakage of tire in time. Tire Pressure monitoring system (TPMS) is mainly used to monitor tire pressure when running and alarm the leakage and low pressure of tire, so it is a safeguard to drivers and passengers. In view of the existence problems of TMPS market and research recently, the article conducts the research to the methods of indirect tire pressure monitoring by taking tire longitudinal stiffness as the object of study.Setting about the concept of tire stiffness, the idea using tire longitudinal stiffness to monitor the change of tire pressure is put forward in this research, and the tire modes which is used to study the perormance is analysed. As well as this foundation, the influence of tire pressure to tire longitudinal stiffness is analyzed based on the tire brush model. The correlation between tire longitudinal stiffness and tire longitudinal force is set up based on the theory of vehicle dynamics. From this the mathematical model of the estimation to tire longitudinal stiffness is established. Using this model, the tire longitudinal stiffness can be estimated using the signals of wheel speed only, and the tire pressure monitoring can be realized.First the main factors effectting the calculating precision of wheel speed are researched. For the quantitative error, the disposal method is determined to use the self-adapted one through the comparision and analysis on the different calculating methods of wheel speed.On this basis, the method to calculate the vehicle speed and acceleration using wheel speed is researched. According to the theory of auto-adapted non-linear filter, a non-linear filter arithmetic which can calculate the auto driving speed is developed using the wheel speeds. For calculate the automotive traveling acceleration, the method based on the estimating of tire longitudinal force is adopted. According to the state equation to estimate the tire longitudinal force, the methods of input estimation from state equation is investigated. The optimal differential filter is designed which is used to the estimating of vehicle acceleration, and the optimized characteristic of the structure of the optimal differential filter was analysed and justified. In the end, the methods to solve the optimal differential filter is determined and also applied to the estimation of the automobile's driving acceleration. Under various conditions, the comparative result between the calculating result of vehicle speed and acceleration obtained by the test dates and the real value obtained by the sensor direct shows that the calculating result of vehicle speed and acceleration is accurate, and the calculating method which is applied to the research in this paper is practicable.According to the systematic identification theory, the estimate method about tire longitudinal stiffness based on the searching pattern is investigated finally. The result of simulation through MATLAB and the estimated results by tentative data show that there is great difference among the estimate value of tire longitudinal stiffness under different tire pressure, and the change of tire pressure can be monitored, but under the same condition there is no significantly difference among the estimate value of tire rolling radius, it can not be used to monitor the change of tire pressure.In the last, the composition and the principle of the system of acquisition and processing develop by ourselves is introduced. Through this system, the estimating of tire longitudinal stiffness in real time can be put up.The experiment results show that the tire pressure has great influence to the estimating valve of the driving tire longitudinal stiffness. Using the estimating valve of the tire longitudinal stiffness to monitor the rire pressure is feasible and the accuracy is high. According to the driving tire, the tire pressure of driven wheel can be monitored using the method of compare mutual between the wheel speed on the same side of the car, and the monitoring of the tire pressure to each tire in the car can be realized.