Motion planning in the presence of movable obstacles

Abstract

Most motion planning algorithms have dealt with motion in a static workspace, or more recently, with motion in a workspace that changes in a known manner. We consider the problem of finding collision-free motions in a changeable workspace. That is, we wish to find a motion for an object where the object is permitted to move some of the obstacles. In such a workspace, the final positions of the movable obstacles may or may not be part of the goal. In the case where the final positions of the obstacles are specified, the general problem is shown to be PSPACE-hard. In the case where the final positions of the obstacles are unspecified, the motion planning problem is shown to be NP-hard. Algorithms that run inO(n 3) time are presented for the case where there is only one movable obstacle in a polygonal environment withn corners and the object to be moved and the obstacle are convex polygons of constant complexity.