Manipulator path planning by decomposition: algorithm and analysis

Path planning is achieved by a special decomposition of the robot manipulator, an offline preprocessing stage, and a three phase online path planning scheme. The decomposition consists of separating the robot into several chains where a chain is a combination of several consecutive links and joints. Preprocessing is performed by defining a set of postures for each chain and setting up a collision table which re-integrates the chains into the full robot and stores the collision states of various discretized robot configurations with the obstacles. Path planning using a local search is performed independently in joint subspaces associated with robot chains. The paths found for the chains are synthesized to obtain a collision-free path for the robot. This decomposition reduces the exponential growth of computation with robot degrees of freedom (DOF) to that of the much lower chain DOF. As a result, it is possible to achieve short planning times for practical robots operating in three-dimensional work spaces. Analysis of computation time and space of the proposed method are presented. Results supporting the analysis are provided for a large number of path-planning trials with two practical robots operating in relatively cluttered environments.