Curve Trajectory Tracking for Autonomous Vehicles Using Linear Time-Varying MPC

Most researches concerning the yaw stability and rollover prevention for autonomous vehicles are studied separately and decoupled the longitudinal and lateral vehicle dynamics control. However, the roll motion influences the yaw stability during high speed curve steering manoeuvres. With this in mind, a curve trajectory stable tracking controller for autonomous vehicles using linear time-varying model predictive control (LTV MPC) is proposed in this paper. The lateral dynamics control employs the LTV MPC to generate a sequence of optimal steering angles considering the constraints of control input, state output, yaw stability and roll stability together in the cost function, in which the prediction model utilizes an 8 degrees of freedom (DOF) vehicle model and the plant utilizes a 14-DOF vehicle model. The longitudinal control adopts PID control embedded in the MPC framework to update the speed at each optimization step and generate the total wheel torque for speed tracking. The trajectory tracking simulation results demonstrate that the vehicle tracks the reference trajectory and speed well with the proposed controller, which satisfies the constraints of control input, state output as well as the boundaries of yaw stability envelope, sideslip angle and roll angle, thereby reducing the risk of vehicle skid and rollover.