Study Of Tire Model Under Driving And Braking Condition

As widely application of the dynamic simulation technology in the R&D of whole vehicle and its assembly, engineers want the whole vehicle dynamic model to be more and more accurate. Tire model is the media which transfers several of force and vibration from road to the body, the quality of whole vehicle model attaches most importance to the accuracy, foresight ability and robustness of tire model. The tire's barking and driving characteristic is related to the study of whole vehicle's longitudinal and lateral dynamic which has especially irregular meaning in vehicle's braking and corning condition. In the past, some experts had done much research in tire's longitudinal slip characteristic which sees tire's braking and driving characteristic as the same one. In some extend, these research have met the needs of vehicle dynamics simulation. However, there are many differences in tire's driving and braking characteristic. In order to improve the accuracy of vehicle dynamic model, it is necessary to develop a high precision tire model.In the experiment, the test of tire's mechanical characteristic under driving condition needs more complex equipment, which causes the lack of tire's driving testing data and restricts tire models to be more accuracy. Based on previous researches, this paper studies the relation and differences between tire's braking and driving characteristic. Moreover, forecasting tire's driving mechanical property form its braking characteristic has been studied. The mainly studying aspects are as follows:Firstly, the tire's mechanical property is directly related to the vertical load distribution in contact patch. In chapter 3, tire's mechanical characteristic under braking and driving condition is analyzed. In addition, the movement of contact patch, the offset of vertical load distribution and the formation of rolling resistance under braking and driving condition are also analyzed in this paper. In order to study the difference of vertical load distribution under braking and driving condition, the theoretical model of physical tire is established. The analysis shows that the distribution offset will be forward under braking condition and be backward under driving condition. For the sake of verifying the result of theoretical tire, three dimension FEM tire model is established. Using the FEM tire model, the virtual tire experiment under braking and driving condition is conducted in ABSQUS. The virtual experiment shows the same result as the theoretical tire model.Secondly, the arbitrary vertical load distribution function is introduced to simulate the difference vertical load distribution under braking and driving condition. Later, the pure longitudinal slip tire model under braking and driving condition is respectively established. The effect of the different offset of vertical load distribution to tire longitudinal force, slip-starting point has been studied. In chapter 4, the braking-lateral and driving-lateral tire model is established. The effect of the different offset of vertical load distribution to tire longitudinal force, lateral force and aligning torque also has been studied.Thirdly, the dynamic distribution of vertical load and dynamic fraction in contact patch are introduced to accurately simulate tire's combined condition mechanical characteristic. In the chapter 4, the comparison between the theoretical data and the test data shows that the theoretical tire model is accurate.Finally, in the chapter 5, from tire's braking test data, we identify tire's characteristic and fraction characteristic parameters. Based on the assumption that, tire has the same characteristic parameters and fraction characteristic parameters, the prediction of tire's driving characteristic from its braking characteristic has been studied. The forecasting data fits close to the test data. The prediction method can conquer the lack of driving test data and provide more accurate tire model for vehicle dynamic analysis.