Yaw moment Lyapunov based control for In-Wheel-Motor-Drive Electric Vehicle

Abstract

The new generation of electric vehicles, also called in-wheel-motor-drive electric vehicles (IWM-EVs), will replace the traditional power-train by on-hub motors. Consequently, it will offer new options and flexibilities in motion control due to its structural merits, i.e the longitudinal force of each wheel could be controlled independently. This paper proposes an advanced direct yaw moment control strategy to improve IWM-EV steerability and stability. The proposed integrated control involves two coordinated standalone Lyapunov model-based controllers. Coordination is ensured according to the vehicle dynamic states evolution in the phase plane defined by the body sideslip angle and its rate. The control objective in the linear driving zone is to enhance the vehicle steering response by tracking a certain reference yaw rate. However, when the vehicle reaches the handling limits, the primary objective becomes to stabilize the vehicle while reducing a vehicle stability index. The yaw moment generated to provide control goals is then converted into four torque inputs of the four in-wheel motors. An algorithm is proposed for an effective torques distribution to maintain vehicle longitudinal velocity. Simulation results carried out on a full nonlinear IWM-EV model confirm the ability of the developed control scheme to improve vehicle handling and directional stability.