A new hierarchical yaw Stability Control approach for Four-Wheel Independent Driving electric vehicles

Electronic Stability Control (ESC) belongs to an over-actuated control system, in which the torque distribution is a key point issue. This paper proposes a novel yaw dynamics controller for high vehicle stability and handling performance. A hierarchical control structure, consisting of an upper and a lower controller, is proposed to obtain optimal torque distribution for Four-Wheel Independently Driving (FWID) electric vehicles. In order to maintain the vehicle actual motions, that is, yaw rate and vehicle body side-slip angle, close to desired responses, the upper controller calculates the desired yaw moment by Sliding Mode Control (SMC) method. Considering the contributions of tire longitudinal and lateral forces to yaw motion, the lower controller based on Direct Yaw Moment Control (DYC) outputs the optimal torque command for four wheels. By analysis and comparison with prior control methods, simulation results obtained from various maneuvers indicate that the proposed two-level controller is shown to enhance the yaw rate response and ride performance.