Algorithm Research Of Vehicular Lateral Stability Control System Based On Slip Control

Control system of vehicular lateral stability (VLS) based on braking system is the most effective technology to improve vehicular active safety .It is the most important part of Electronic Stability Program (ESP). Now, ESP is the international research focus in the vehicle active safety field. Electronic Stability Program is gradually equipped to the moderate and top cars, while in China, the research in this field is at very beginning.The dissertation pays more attention to control algorithm and simulation of Control system of vehicular lateral stability. Based on the abroad achievements in this field, the following issues are discussed:1,Overview of the hardware for control system of vehicular lateral stability.2,Design of control logic and control strategy of control system of vehicular lateral stability.3,Develop of dynamics simulation software.4,Validate of control system of vehicular lateral stability via vehicle test on road .There are six chapters in the dissertation.In Chapter One, the function of control system of vehicular lateral stability are introduced; the history of the vehicle stability control and its present status are discussed; the key condition that further development of electronic stability program are discussed; the contents of the dissertation are put forward.In Chapter Two, the total configuration of the control system of vehicle lateral stability is introduced detailed. The control system consisted of sensors, actutor unit and Electronic control unit (ECU). The main variables which describe the motion of vehicle are measure by sensor system. The sensor system includes four wheel-speed sensors, one brake-pressure sensor, one steering-wheel angle sensor, and one yaw-rate sensor integrated with a lateral-acceleration sensor. Control system adjusts the motion of vehicle through brake-pressure modulation and Engine management system, which compose the actuator unit. ECU is the head of the control system. It concludes two controller, a lateral stability controller and a slip-rate controller. ECU calculates and determines the estimated values of vehicle motion variables according to the signals from sensors, and calculates required yaw motion which keeps the vehicle stability. Then, it sends the control instruction to actuator, making the motion of vehicle follow dirver's manipulation.In Chapter Three, control algorithm of vehicle stability control is brought forward. The error of yaw rate can represent vehicle's steering characteristics. When slip-angle is very large, driver can't control vehicle by steering wheel. So the errors of yaw rate and slip-angle are chose as control parameter of stability control. The nominal yaw rate and nominal slip-angle are confirmed by the two degree of freedom vehicle model (bicycle model). Yaw rate and Slip-angle PID control is applied to yaw moment control. The required yaw moment is calculated by PID controller, and then ECU transmits the required moment into pressure of brake system. To prevent braked wheels been locked, the max pressure of brake system can not overhead the pressure threshold which calculated by slip controller. By yaw moment distributing logic, the best braking wheel and target brake pressure are confirm.In Chapter Four, dynamics simulation software is built. A vehicle model can describe the vehicle non-linear characteristics under limit condition is needed for simulation control system of vehicle lateral stability. This chapter adopts HSRI tire model in tire's ISO coordinate, in which the tire's longitudinal slip property and lateral slip property are considered. Except for tire model, the dynamics simulation software is a 7-DOF vehicle model, which including engine model, brake model, driveline model, vehicle model, assistant model and driver model. Finally, Simulink model of dynamics simulation software and graphics user interface based on Matlab are worked out. The controller model is built in this chapter too. Based on the vehicle dynamics model and controller model, a simulation study is made on driver step input, sin input double lane input. The correctness and practicability of control system of vehicle lateral stability are validated.The Chapter Five is about vehicle test on road. We have had a road test with M6 and handled the datum from the test. The results of the test has shown LSC can effectively improve the vehicle handling and stability particularly during cornering, by ensuring stability and tire cornering force on various road surfaces.The Chapter Six is the summary and conclusion of the dissertation.The following conclusions can be derived from the simulation study of control system of vehicle lateral stability when vehicle is steering.The scheme put forward at beginning of this dissertation is feasible.Yaw angle rate and slip-angle are very important control parameter of vehicle stability control system. The lateral stability of vehicle can be enhanced by controlling yaw angle rate and slip-angle.Software in loop simulation can quicken the development of vehicle stability control algorithm.