Collision avoidance using a free space enumeration method based on grid expansion

Abstract

This paper describes a general and simple method for planning collision-free paths of manipulators. Many algorithms have been proposed for the collision avoidance problem, but no general and simple method has been developed which can be applied to any type of manipulator. The method based on the configuration space approach seems promising, but the configuration space is a multi-dimensional space and the amount of data concerning free space is enormous. However, most of these data are not used to plan a single motion of a manipulator. The free space concerned in planning a motion can be determined independently of the kinematic characteristics of the manipulator by a method based on grid expansion. The algorithm is as follows. First, collisions are detected during a linear movement in the configuration space and a set of collision-free configurations is calculated. Then the collision checking operations are propagated to neighbouring configurations. This process is continued until the wavefront from the initial configuration and that from the final configuration meet. This method has been implemented on a solid-model-based robot programming system and has been applied to an articulated manipulator.