Robot motion planning by a hierarchical search on a modified discretized configuration space

In this paper, a hierarchical A*-based method for motion planning of robot manipulators is presented. The algorithm's advantage is its simplicity. The algorithm is also shown to be resolution complete. The algorithm searches the robot's configuration space with many different "step sizes" at the same time. The step size denotes the distance between the nodes A* expands during the search. When a path candidate goes far from the obstacles, a big step size is used. When it goes near the obstacle surfaces, a smaller step size is used. Two simulated robot workcells are provided for experimental study. The motion planning of 5 and 6-degrees-of-freedom industrial robots appears to be reasonably fast.