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