Research On The Stability Of The Automobile Lateral Motion And Its Chaos Control Based On EPS/ESP

In recent years, with the rapid development of the automobile industry in our country, the automobile has gradually gone into people’s daily life. Due to the driver’s improper operation and other reasons, during the process of automobile moving, the traffic accidents cased by the lateral instability increasingly, which will bring huge losses of the personal and property safety. The active safety technology that can keep the automobile lateral stability during the rapid steering and high-speed obstacle avoidance and other extreme driving conditions has become a research focus. The electric power steering system(EPS), vehicle stability control system(ESP) and the chaos of the lateral motion have been mainly studied in this article to improve the automobile lateral stability.In this dissertation, the development of the automobile stability research has been reviewed firstly, the work principle of the EPS and ESP system and the research on improving automobile stability have been introduced, then the study of the integrated control of the steering system and ESP system was discussed, finally the research on the chaos in the automobile field. The current research status also was summarized in the automobile stability.In view of the problem that the current EPS controller was build based on the precise mathematical model, the EPS system linear parameter varying(LPV) model was established, which consider the varying of the steering column stiffness, assist motor inductance and the reduction gear ratio of the electric motor transmission device. The H-infinity robust controller was designed, the hardware in the loop test and the numerical simulation were carried out, both of the results show that the robust controller proposed in this dissertation has better effect than the traditional one, the assist performance, the steering road feel and the automobile’s handling performance were all improved.In current ESP system research, the parameters in the reference model ware constant, but the centroid position of the automobile will change in the real driving because the acceleration and deceleration drive conditions. To solve this problem, the vehicle model including the yaw, longitudinal, vertical, lateral and four wheel movement was build. The front and rear suspension force were estimated by using the calman filter observer, the forgetting factor least squares method was used to realized the estimation of the centroid position, and the desired values of the yaw rate and the side slip angle calculated by the reference model were revised by using the estimation value of the cntroid position. Then the self-adjusting PID controller of the ESP system was designed. Fanlly, the simulation results show that the control method of the ESP system considering the centroid position change has better effect than the without considering one, which can improve the lateral stability during the high speed steering.The function of the EPS and ESP systems were analyzed, when the automobile was during the rapid steering and high-speed obstacle avoidance and other extreme driving conditions. The upper function allocation coordination controller was designed by using multi-objective fuzzy decision method to realize the coordination control of the EPS and ESP systems. The two cases about coordination control and without coordination control were simulated, which results show that the coordination control can keep the vehicle lateral stability better during the rapid steering and high-speed obstacle avoidance and other extreme driving conditions. Finally, The 3-DOF nonlinear vehicle model was established. Then based on the Lyapunov method the chaos of the lateral movement was analysed and the numerical simulation was carried out. The results show that under certain conditions, the chaotic phenomenon would appear during the vehicle lateral movement.The SMVSC controller was designed by using the sliding mode variable structure control (SMVSC) method to suppress the chaos which appears during the vehicle lateral movement. Finally, the uncontrol, SMVSC control and SMVSC control based on the adaptive reaching law were simulated, which results show that the SMVSC control based on the adaptive reaching law can present better performance than that of others by effectively suppressing the chaos.The real vehicle testing system was built based on the VBox Ⅲ data acquisition system. Based on the centroid position correction of the ESP control algorithm, the ESP controller was designed, and which was used to implement the double lane change test on the dry and wet pavement. The results of the real vehicle test were consistent with the numerical simulation results, which verified the effectiveness of the proposed control strategy.