Comparative Study on Tracking Control Methods for Automatic Emergency Steering and Collision Avoidance of Intelligent Vehicles

To improve the active safety of intelligent vehicles, three different tracking control methods for automatic emergency steering collision avoidance are proposed. First, a simplified model of vehicle collision avoidance was developed, by which three different collision avoidance modes of braking, steering, and their combination were compared and analyzed. Second, an 18-degree-of-freedom-(DOF) unified dynamic model of vehicle chassis, including the coupling characteristics of the steering, braking, and suspension subsystems, was developed to study the actual response of the vehicle during collision avoidance. The correctness of the above model was verified by relevant experiments. A control framework for an automatic emergency steering collision avoidance system for intelligent vehicles was constructed. The yaw rates and yaw angular accelerations of the fifth and seventh polynomial reference paths were compared and analyzed. Using the linear two-DOF steering dynamic model as the reference object, three different tracking control systems were designed, including the optimal control of four-wheel steering, optimal control of front wheel steering, and combination of feedforward and feedback of front wheel steering. Using the 18-DOF unified dynamic model of vehicle chassis as the research object, three different types of collision avoidance control system were compared and analyzed by simulation tests. The longitudinal distance required for steering collision avoidance is largely reduced compared to that of the braking collision avoidance. The effect increases with the increase in vehicle speed and decrease in road adhesion coefficient. The lane-changing process of collision avoidance of the seventh-order polynomial reference path is smoother than that of the fifth polynomial reference path. When the actual speed is inconsistent with the speed used by the controller, the performance of the former is higher than that of the latter. The four-wheel steering control system has good collision avoidance performances on high-and low-adhesion roads, followed by the optimal front wheel steering control system, while the feedforward and feedback control system of front wheel steering exhibits a serious instability on a low-adhesion road. © 2021, Editorial Department of China Journal of Highway and Transport. All right reserved.