Research on path planning methods for underground roadheader robots

In order to solve the problems of difficulty and low efficiency in the movement of robotic roadheaders under conditions of non-full-section roadways in coal mines, the characteristics of unstructured environments in coal mines and the motion characteristics of robotic roadheaders were analyzed, and a path planning method for robotic roadheaders based on deep reinforcement learning was proposed. The tunnel environment was constructed in real time using depth cameras, a virtual model for detecting roadheader-tunnel collisions was established, collision detection was performed in a virtual environment using the hierarchical bounding box method, and an obstacle avoidance strategy under the restrictions of tunnel boundary was developed. Considering the size of the roadheader robot and the single goal in the path planning process, the HER-SAC algorithm was proposed based on the traditional SAC algorithm by introducing the retrospective experience playback technology. The algorithm expands the target subset through the trajectory obtained by the initial target in the environment to increase training samples and training speed. On this basis, an agent was established based on the reward and punishment mechanism, and its state space and action space were defined according to the motion characteristics of the roadheader robot. The agent was trained using three algorithms under the same scenario, and the performances of these algorithms were comparatively analyzed using four indicators, namely, the average reward value, the maximum reward value, the number of steps to reach the maximum reward value, and robustness. In order to further verify the reliability of the proposed method, a virtual-real combination method was adopted, roadheader path planning was performed in two experimental scenarios set by adjusting the target position, and the results produced by the traditional SAC algorithm and the HER-SAC algorithm were compared. The results show that the HER-SAC algorithm converges faster and generally performs better than the PPO and SAC algorithms; in the two experimental scenarios, the path planned by the HER-SAC algorithm is smoother and shorter than that planned by the traditional SAC algorithm, and the error between the end point of the path planned by the HER-SAC algorithm and the target position is less than 3.53 cm, indicating that the HER-SAC algorithm can effectively execute and complete path planning tasks. This study lays a theoretical foundation for autonomous transfer control of roadheader robots and provides a new approach to the automation of coal mining equipment.