A Path Planner in Changing Environments by Using W-C Nodes Mapping Coupled with Lazy Edges Evaluation

This paper presents a path planner based on PRM framework for robots operating in changing environments, in which obstacles can move randomly and robots may change their original shapes, e.g. a robot manipulator grasps an object. W-C nodes mapping coupled with lazy edges evaluation is used to ensure a generated path containing only valid nodes and edges when constructed probabilistic roadmap becomes partially invalid in changing environments. Our method combines merits of DRM and Lazy PRM methods. W-C nodes mapping, which is constructed in pre-processing phase by mapping every basic cell in workspace to nodes of roadmap, is preserved to indicate invalid nodes of roadmap fast whenever obstacles move. W-C edges mapping, which is another mapping relationship of DRM method, is skipped since it is much more complicated and time-consuming for construction. The simplified mapping with smaller size can be recomputed or modified fast when robots change their original shapes. Instead, lazy edges evaluation is used to ensure all edges valid along a found path. Simulated experiments for a dual-manipulator system show that our method is efficient for path planning in changing environments