Trajectory Tracking Control for Self-driving Vehicle Considering Road Slope and Adhesion Condition

There are strict constraints of vehicle location and running time in trajectory tracking. When a self-driving vehicle with a two-dimensional tracking strategy drives on ramps, the demand trajectory will be lengthened due to the existence of road slope, resulting in low tracking accuracy. Moreover, the existing techniques are difficult to cope with sudden changes in road adhesion. Here we discuss a series of studies on trajectory tracking control with the consideration of road slope and adhesion condition. A tridimensional vehicle kinematics model is constructed, based on which a basic tracking controller is designed to adjust front wheel steering angle. The obtained vehicle speed is not directly applied to the self-driving vehicle, but is sent as a control target to a motor torque command controller based on a constructed longitudinal vehicle dynamics model. In this process, the control of slip ratio is taken into account to prevent wheels from being locked by regulating the torque command. The two controllers are linked by the vehicle speed. Some comparative tests are carried out by a software-in-loop experimental platform. The test results demonstrate that the adaptability of the self-driving vehicle to the road slope and adhesion variation during the trajectory tracking can be improved.