Integrated Control of Braking and Steering Subsystems for Autonomous Vehicle based on an Efficient Yaw Moment Distribution

This paper presents an Integrated Chassis Control (ICC) strategy for Electronic Stability Control (ESC) and Active Four Wheel Steering (AFWS) based on an efficient optimal yaw moment distribution. To further enhance the handling and lateral stability of vehicle equipped with ESC, a new Weighted Pseudo- inverse Control Allocation (WPCA) based ICC is proposed. The cornering forces of both front and rear wheels are used to cooperate with the ESC braking forces, so as to further extend the operational envelope of the vehicle. A bi-level hierarchical control structure is employed. In the upper level, the sliding mode control with a combined sliding surface is used to generate the desired virtual control. In the lower level, a revised optimal function is defined to tune the control authority of actuators, and an algebraic operation based WPCA method is adopted. To avoid tire forces saturation and enforce a certain stability margin, a boundary layer constraint is further considered in the proposed optimization problem. A severe lane change maneuver is used to investigate the performance via closed-loop driver-vehicle- controller simulations using CarSim and MATLAB/Simulink. Simulation results demonstrate that the proposed algorithm outperforms current control practice without violating the actuators physical limitation.