Abstract
The current research of autonomous vehicle motion control mainly focuses on trajectory tracking and velocity tracking. However, numerous studies deal with trajectory tracking and velocity tracking separately, and the yaw stability is seldom considered during trajectory tracking. In this research, a combination of the longitudinal–lateral control method with the yaw stability in the trajectory tracking for autonomous vehicles is studied. Based on the vehicle dynamics, considering the longitudinal and lateral motion of the vehicle, the velocity tracking and trajectory tracking problems can be attributed to the longitudinal and lateral control. A sliding mode variable structure control method is used in the longitudinal control. The total driving force is obtained from the velocity error in order to carry out velocity tracking. A linear time-varying model predictive control method is used in the lateral control to predict the required front wheel angle for trajectory tracking. Furthermore, a combined control framework is established to control the longitudinal and lateral motions and improve the reliability of the longitudinal and lateral direction control. On this basis, the driving force of a tire is allocated reasonably by using the direct yaw moment control, which ensures good yaw stability of the vehicle when tracking the trajectory. Simulation results indicate that the proposed control strategy is good in tracking the reference velocity and trajectory and improves the performance of the stability of the vehicle.
Highlights
With the development of science and technology, autonomous vehicles are gradually coming into view
The motion control in an autonomous vehicle is mainly focused on ACC (Adaptive Cruise Control) [2] and trajectory tracking [3]
For the trajectory tracking problem, it is generally considered as a lateral control, which mainly considers the accuracy of the reference trajectory under a constant velocity
Summary
With the development of science and technology, autonomous vehicles are gradually coming into view. The motion control in an autonomous vehicle is mainly focused on ACC (Adaptive Cruise Control) [2] and trajectory tracking [3]. To solve the problem of lateral motion control, a large number of studies assumed that the velocity of the vehicle was a constant. Different control methods are proposed to solve the problems, for example, the longitudinal and lateral control in Ref. MPC, sliding mode control (SMC), gain-scheduling and feedback methods were usually used to solve the control of longitudinal and lateral vehicle dynamics. Most of the relevant research works are carried out on longitudinal and lateral control separately, and the dynamic performance of the vehicle cannot be reflected in the actual operation. Where Fxfl , Fxfr , Fxrl , and Fxrr are the tire longitudinal forces of the left front wheel, right front wheel, left rear wheel, and right rear wheel, respectively; Fyfl , Fyfr , Fyrl , and Fyrr are tire lateral forces of the left front wheel, right front wheel, left rear wheel, and right rear wheel, respectively; lf and lr are the distances from the front axle to the centroid and from the rear axle to the centroid, l lr Fxlr δrl
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