Study On Envelope Integrated Chassis Control System Based On Model Predictive Control

In order to cope with the complicated operation conditions and to improve vehicle safety and comfort, various active control systems(such as EBS/ABS, 4WS, ESC, etc.) have been eqqipped on modern vehicles. Generally speaking, these control systems are developed and supplied by different manufacturers. With each of these systems, the enhancement of vehicle performance is obvious. However, when they work together, many problems may occur because of the coupling of vehicle dynamics. Therefore, since the mid-1980 s, the research on integrated vehicle dynamics control has become a focus and attracted much attention.Based on the projects, namely ‘Study on Integrated Vehicle Dynamics Control based on Optimal Tire Force Distribution(NSFC Grant No. 50875163)’ and ‘Research on the Envelope Control for Vehicle Motion Control based on Driver-Vehicle Interaction(NSFC Grant No. 51375299)’, which are sponsored by ‘National Natural Science Foundation of China’, and the practical project, ‘Research and Development on Handling Quality Evaluation Syetem of the Vehicles based on Dricer-vehicle-road Closed-loop System(SAIC Grant No.1007)’, which is sponsored by ‘Shanghai Automobile Incorporation Company Industrial Technology Development Fund of China’, the study on the envelope integrated chassis control system based on model predictive control is presented in this dissertation, which deals with the following problems: 1) how to avoid the conflicts and interventions among different subsystems; 2) how to prevent vehicle accidents and reduce crash fatalities, when a risk of crossing the dynamics limits occurs, which is often caused by a miscalculated action of the driver or a sudden change of the road condition.Firstly, through the establishment of a mathematical model of the vehicle, the vehicle information can be estimated, such as the tire ground longitudinal / lateral values and their limits. Furthermore, the vehicle information is important for the improvement of the performance of the integrated chassis control system based on model predictive control.Secondly, an envelope integrated chassis control system based on model predictive control with a main-loop/servo-loop structure is designed and implemented. The main-loop control system, i.e. Envelope Integrated Chassis Control System(EICCS), concerns the calculation of the desired tyre forces of and the angle of active steering system(AFS) which are executed in the servo loop to stabilize the vehicle by keeping it within a safe region of the yaw rate-sideslip state space. Via analyzing the established vehicle model, the vehicle dynamics envelope, e.g. the maximum steering angle a driver can apply under different driving conditions, can be acquired, based on which the optimal allocation strategy of control forces/torques is determined by the model predictive control system, and therefore the overall vehicle performance can be improved through controlling of the steering angle.As for the servo-loop control system, on one hand, an EBS/ESC system, based on nonsingular and fast terminal sliding mode method, is built to implement the desirable tyre force, and an AFS control system is built to implement the desirable steering angle. On the other hand, by analyzing and fusing the information of the servoloop control system, some effective information about vehicle dynamics, e.g. longitudinal forces/torques estimated via electronic braking system(EBS/ESC), lateral stiffness and lateral forces estimated from aligning torque sensored by AFS, etc., can be fed back to the EICCS.At last, numerical simulation results are used to verify the envelope integrated chassis control system. The simulations show that the designed system can be used to prevent unintended vehicle behavior, assisting drivers in maintaining control of their vehicles and co-ordinate EBS/ESC and AFS effectively, and the handling performances can be significantly improved, compared to individual EBS/ESC or AFS controllers.