I. Introduction
Autonomous vehicle is a new generation of ground wheeled vehicle equipped with advanced on-board sensors, controllers, actuators, and other technologies that enable functions such as complex environmental perception, intelligent decision-making, and precise control. It is ultimately expected to replace human driving operations. Trajectory planning, as a critical module in autonomous vehicles, is responsible for planning a collision-free path between the current position and the target position of the vehicle, considering certain constraints based on the given scenario. Planning techniques, therefore, play a crucial role as they directly reflect the intelligence level of an autonomous vehicle [1], [2].