Automatic Emergency Collision Avoidance of Four-Wheel Steering Based on Model Following Control

In order to improve the performance of automatic emergency steering and collision avoidance of intelligent vehicle, two automatic steering control methods under ideal model following control are proposed. The two ideal reference models are the reference model with zero sideslip angle of vehicle gravity center and the reference model with no phase-lag in vehicle lateral acceleration. The control system adopts the combination of outer loop and inner loop. In the design of the outer loop controller, the optimal control is used to get the steering wheel angle needed to avoid collision. The inner loop controller uses feedforward and feedback control to get the required front and rear wheel steering angles. Taking vehicle two degrees of freedom (DOF) lateral dynamics model as the research object, the vehicle collision avoidance reference trajectory is obtained through the fifth-degree polynomial. The simulation test of automatic emergency steering and collision avoidance for vehicles equipped with the above control system is carried out on high and low adhesion roads respectively. The comparison with the control system without reference model is also carried out. The results show that the collision avoidance effect of the control systems with reference model are better than those without reference model. When avoiding collision on a high adhesion road, the reference model control system with zero sideslip angle has the best effect. While when avoiding collision on a low adhesion road, the reference model control system with no phase-lag in lateral acceleration has the best effect.