Lateral and longitudinal coordinated control for ramp road vehicle with spatio-temporal trajectory planning

Aiming at the problem of merging and obstacle avoidance of intelligent vehicles in ramp road, in which the main road is usually a three-lane road and the ramp is a single-lane road, this study proposes a lateral and longitudinal coupling trajectory tracking control method for ramp road vehicle with spatio-temporal trajectory planning. Firstly, according to the ramp road structure and vehicle driving criteria, the main road and ramp potential field are established, and the obstacle vehicle potential field is presented based on the shape, speed, and direction of this obstacle vehicle on road. Secondly, a variable step path planner is proposed in accordance with the improved artificial potential field (APF) and the safe driving distance of the vehicle, by which the optimal driving path can be predicted in view of the current environment. Meanwhile, the host vehicle speed can be planned by detecting the collision relationship between the host vehicle and the obstacle vehicles on the planned optimal driving path, then the path and speed planning are combined to form a spatio-temporal trajectory planner to ensure the safe driving of the host vehicle in different road environments. Furthermore, considering the vehicle lateral and longitudinal coupling relationship, a coupling model predictive control (MPC) trajectory tracking control method is put forward. In the end, the simulation is carried out in the ramp road scenario based on the CarSim-Simulink joint simulation platform, whose results show that the strategy exhibits better security and stability in the process of merging and obstacle avoidance.