Abstract
Curved path tracking control is one of the most important functions of autonomous vehicles. First, small turning radius circular bends considering bend quadrant and travel direction restrictions are planned by polar coordinate equations. Second, an estimator of a vehicle state parameter and road adhesion coefficient based on an extended Kalman filter is designed. To improve the convenience and accuracy of the estimator, the combined slip theory, trigonometric function group fitting, and cubic spline interpolation are used to estimate the longitudinal and lateral forces of the tire model (215/55 R17). Third, to minimize the lateral displacement and yaw angle tracking errors of a four-wheel steering (4WS) vehicle, the front-wheel steering angle of the 4WS vehicle is corrected by a model predictive control (MPC) feed-back controller. Finally, CarSim® simulation results show that the 4WS autonomous vehicle based on the MPC feed-back controller can not only significantly improve the curved path tracking performance but also effectively reduce the probability of drifting or rushing out of the runway at high speeds and on low-adhesion roads.
Highlights
Path tracking control enables autonomous vehicles to travel accurately, smoothly, and safely along a predetermined path and to remain stable under all driving conditions [1]
Kim et al [7] used an model predictive control (MPC) path tracking control method based on quadratic programming (QP) optimization to improve the path tracking performance of autonomous vehicles
Schwarting et al [8] used a receding horizon planner based on nonlinear model predictive control (NMPC) to ensure safety collision avoidance
Summary
Path tracking control enables autonomous vehicles to travel accurately, smoothly, and safely along a predetermined path and to remain stable under all driving conditions [1]. In a recent study by Liu et al [20], a feed-forward controller that can adjust the steering sensitivity coefficient of the 4WS vehicle based on zero-sideslip angle according to the steering angular frequency and vehicle speed is proposed, but this controller is not suitable for low-adhesion curved roads.
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