I. Introduction
The mobile robot technic is beneficial for reducing labor and improving production efficiency, so it has become a hot research topic in recent years. Path planning is a key module of the mobile robot. The goal of this module is to generate a collision-free, smooth, and energy-friendly path in a complex environment. High time efficiency is the most important requirement to achieve this goal, so many studies focus on how to reduce the time cost of the path planning module. Despite that much progress has been made by previous research, path planning in a crowded environment is still a challenging job.