Direct Yaw Moment Control For In-Wheel Motor Electric Vehicles

In recent years, the growing environmental and energy issues brought new opportunities for the new energy vehicles. Because of the short transmission chain, high interior space utilization and good economy, in-wheel motor electric vehicle(IEV) was widely concerned by the industry and have great potential for development. Therefore, subsequent extension studies about the IEVs is very important. Since most of accidents occured due to the instability of automobiles and automotive safety has always valued by the people, this paper focuses on the direct yaw moment control of IEV and did some studies as follows:Firstly, the motor model has been developed. The mathematical model of permanent magnet synchronous motor(PMSM) has been discussed in detail and the SVPWM control method enabled the control of the single motor. Based on the MATLAB/Simulink software, the torque of motor has been controlled. According to the response of the motor in a constant moment incentive, both the response time and control accuracy of the model are able to meet the general control requirements of electric vehicles. Then the correctness of the motor model has been proved.Secondly, an electric vehicle model has been developed. By using the motor model to replace single-wheel model as a power source, an 8-dof electric vehicle model which considered the longitudinal motion, lateral movement, yaw, roll and rotation of the four wheels has been established. The “Magic Formula” tire model which considered tire characteristic in the united conditions has been used in the study. The simulation results of the snake-like conditions show that the electric vehicle model can meet driver's expectations well with rapid response and accurate track.Thirdly, a direct yaw moment controller has been designed. Sideslip angle and yaw rate was selected as the control variables, an observer based on 2-dof vehicle model was established for sideslip angle estimation. Based on the turning condition simulation, feedforward, feedback and “feedforward+feedback” three control structure was comparatively analysised. Finally,the “feedforward+feedback” control algorithm was selected because of the strong anti-jamming capability and good control effect.Finally, the motor traction torques was distributed according to the axle-load proportion, “Lane change” and “J-turn” conditions were used to simulation. Simulation results showed that in both two conditions, sideslip angle and yaw rate were small, the controller has a better control effect. Studies indicate that with the direct yaw moment controller,in-wheel motor electric vehicles handling performance and stability can effectively improved.