Emergency Steering Evasion Control by Combining the Yaw Moment with Steering Assistance

The coordinated control of stability and steering systems in collision avoidance steering evasion has been widely studied in vehicle active safety area, but the studies are mainly aimed at autonomous vehicle without driver or conventional combustion engine vehicle. This paper focuses on the control of hybrid vehicle integrated with rear hub in emergency steering evasion situation, and considering the driver’s characteristics. First, the mathematics model of vehicle dynamics and driver has been given. Second, based on the planned steering evasion path, the model predictive control method is presented for achieving higher evasion path tracking accuracy under driver’s steering input. The prediction model includes an adaptive preview distance driver model and a vehicle dynamics model to predict the driver input and the vehicle trajectory. The rolling optimization balances not only the lateral tracking error, but also the driver acceptance with considering the vehicle stability, the limitation of motor ability and the state of charge of battery are considered as well. The real input from driver and vehicle real time trajectory is used as feedback correction and the characteristics of the driver is considered as a coefficient during correction. Third, a distribution strategy is designed with the combination of active front steering system and yaw moment control system, because of the faster and more accurate regulation, the rear hub motors based differential braking generates the yaw moment compensation before the electric stability control system is triggered due to the loss of vehicle stability. By using the yaw moment and steering combined assistance, the tracking accuracy and vehicle stability in emergency steering evasion has been improved. The effectiveness of the proposed control method is verified by CarSim-MATLAB/Simulink driving simulator.