Integrated control strategy of semi-active suspension and in-wheel motors for handling limit of electric race car

An integrated control strategy is proposed to deal with extreme driving conditions for race cars using magnetorheological (MR) semi-active suspension and in-wheel motors. A novel controllable boundary is introduced as the vehicle state supervisor based on the phase portrait of yaw rate and side slip angle. Compared with the traditional stable region, it can better cope with the aggressive behaviors of racing drivers. The proposed integrated control algorithm consists of a controllable boundary-based hierarchy direct yaw moment controller (HDYC) and acceleration-based scheduling MR damper controller. The HDYC will generate the correct yaw moment based on the sliding mode method when vehicle states exceed the critical area of the controllable region. The MR damper controller includes vehicle attitude control (VAC) mode and maneuverability control (MC) mode. The switch of control mode is determined by vehicle states as well. According to the analysis of load transfer, the acceleration scheduling strategy based on the "g-g" ellipse is utilized to generate the desired current command. Three typical scenarios are conducted through co-simulation of Carsim and Simulink to verify the control strategy, including accelerating and hard braking test, double lane change test, and duration circuit test. Especially, the limit of actuators is taken into consideration. The simulation results show that the proposed integrated control strategy could reduce the lap time and increase the maneuverability as well as stability of race cars, compared with traditional direct yaw moment control. The ultimate acceleration of the vehicle is improved significantly.