Grasp Planning for Occluded Objects in a Confined Space with Lateral View Using Monte Carlo Tree Search

In the lateral access environment, the robot behavior should be planned considering surrounding objects and obstacles because object observation directions and approach angles are limited. To safely retrieve a partially occluded target object in these environments, we have to relocate objects using prehensile actions to create a collision-free path for the target. We propose a learning-based method for object rearrangement planning applicable to objects of various types and sizes in the lateral environment. We plan the optimal rearrangement sequence by considering both collisions and approach angles at which objects can be grasped. The proposed method finds the grasping order through Monte Carlo tree search, significantly reducing the tree search cost using point cloud states. In the experiment, the proposed method shows the best and most stable performance in various scenarios compared to the existing TAMP methods. In addition, we confirm that the proposed method trained in simulation can be easily applied to a real robot without additional fine-tuning, showing the robustness of the proposed method.