Research On Vehicle Stability Control System Based On Sliding Mode Varible Structure Control

Vehicle Stability Control (VSC) is an active safety device, which lets the vehicle run following the driver's intension to prevent vehicle from losing stability. Now, VSC is the international research focus in the vehicle active safety field. With development of control techniques and decrease of control system cost, VSC will replace ABS to be the standard device of modern vehicles. In recent years, VSC gets great development aboard, and is gradually equipped to the moderate and top class cars; while in China, the research in this field is at very beginning. So, to study VSC has great significance for our country and also has broad application prospect.The dissertation analyze systematically about modeling of vehicle stability control system, analysis of theory, study of control strategy and simulation analysis, based on the home and abroad achievements in this field.Firstly, a whole vehicle dynamic and simulation model with two degree of freedom (2DOF) is built on the basis of H.B.Pacejka tire model (Magic Formula) in this paper, and also an ideal linear vehicle model of 2DOF. Studying on the vehicle stability control system in theory, the side-slip angle and yaw rate are chosen to be the main control variables, then the relation between them and vehicle stability is analyzed in deep. And then, the mechanism of the Direct Yaw Moment Control (DYC) method enhancing curve accelerating (or braking) capability at limiting behavior, improving automobile control stability is explained. This provides the theory for vehicle stability control. Using the Direct Yaw Moment Control (DYC), the control arithmetic of the stability controller is studied and their control modules are built in the application of sliding mode variable structure control theories with different control strategies.Based on the step simulation analysis, the designed control system can control the vehicles driving to lose stability, and variation of controlling parameter has important effect to the control effect. With the step simulations, the control effect of the stability controllers and the following characteristic of front steering angle are analyzed and compared synthetically in different driving conditions. Based on 2DOF vehicle model, the controllers can enhance the vehicle stability with various degrees, and have different effects. Because the stability controller is mainly working on low coefficient road, focusing on the driving condition of the research object and synthesizing two aspects of stability control effect and following characteristic to analyze, the control strategy of side-slip angle and the combined control are better than yaw rate control, considering the factors of the applicability with different condition,the responsibility and the realization of structure etc.