Study On Stability Control Of Front Wheel Drive Electric Vehicle Based On Direct Yaw Moment Control

Compared to traditional driving system, in-wheel motor takes up less space,responds quickly and has high transmission efficiency. The independence between in-wheel motors allows combination with automotive active safety technology.Control strategy which can improve vehicle driving stability is designed based on research on steering stability.The research significance of vehicle sideslip angle and yaw rate has for vehicle handling stability is confirmed by analysis of 2-DOF model, the 5-DOF vehicle model is built as well as dugoff nonlinear tyre model. For the purpose of studying factors which have influence on vehicle steering stability, 2-DOF nonlinear vehicle model is built. Change regulation of vehicle stable region is analyzed as speed, steering angle and road adhesion coefficient vary along with yaw rate-vehicle sideslip angle phase-plane diagram, which lay a theoretical foundation for design of control strategy.The experiment platform used to measure mechanical properties of in-wheel motors is constructed and achieve torque-speed curves in different control voltage of in-wheel motors, which can provide reference for subsequent control. In order to improve steering stability, layer control strategy including body posture control layer and torque distribution control layer is designed. Specifically, the up controller is based on model reference adaptive control theory with yaw rate taken as control object and use2-DOF linear model as reference model; The down controller takes proportionate allocation to distribute driving force.The vehicle model and modules of all controller are built in simulink.Simulations are conducted according to different vehicle speed or steering wheel angle step-input condition in road adhesion coefficient. Results show vehicle with control can follow desired yaw rate of reference model well during driving, so this control system can improve vehicle driving stability effectively.