An efficient algorithm which finds collision free paths for a manipulator with 5 or 6 revolute joints is described. It solves the problem for four degree of freedom pick and place operations. Examples are given of paths found by the algorithm in tightly cluttered workspaces. The algorithm first describes free space in two ways: as freeways for the hand and payload ensemble and as freeways for the upperarm. Freeways match volumes swept out by manipulator motions and can be "inverted" to find a class of topologically equivalent path segments. The two freeway spaces are searched concurrently under projection of constraints determined by motion of the forearm.
