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.

I. Introduction

Motion planning is one of the most fundamental problems in robotics. The objective of motion planning is to break down a high-level task into low-level actuator commands. An important aspect of motion planning is path planning, which addresses the geometric concerns of robot motion without regard to time [21]. In this paper, we address the problem of moving a set of actuated and constrained robot links from a start configuration to a goal configuration in a static obstacle environment.