Decoupling Objectives for Segmented Path Planning: A Subtask-Oriented Trajectory Planning Approach

Local trajectory planning (TP) for collision avoidance typically comprises path planning (PP) and velocity planning (VP). Various objectives must be fulfilled in a PP task, and the majority of prior works integrate all objectives into a unified cost function. To prioritize the dominant objectives of each PP stage, we propose to decouple the PP task into two separate subtasks, enabling the logical establishment of subtask-oriented segmented PP methods. First, based on risk evaluation of four vehicle vertices, an improved artificial potential field was established. Second, a novel transit point selection method was applied to decouple the PP task into two segmented subtasks. Then, the optimization problem was converted into a multi-attribute decision-making (MADM) problem and the technique for order preference by similarity to ideal solution (TOPSIS) method was utilized to obtain two optimal segmented paths. Finally, a velocity planner based on cubic polynomial, in conjunction with a support vector machine-based stability classifier, was designed. The proposed trajectory planner was then verified in six typical driving scenarios, including both simulation and real vehicle studies. Verification results demonstrate that the proposed planner effectively decouples the PP task and achieves a safe, comfortable, efficient, and trackable trajectory.