A motion planning based approach for inverse kinematics of redundant robots: the kinematic roadmap

Abstract

We propose a new approach to solving the point-to-point inverse kinematics problem for highly redundant manipulators. It is inspired by recent motion planning research and explicitly takes into account constraints related to joint limits and self-collisions. Central to our approach is the novel notion of kinematic roadmap for a manipulator. The kinematic roadmap captures the connectivity of the configuration space of a manipulator in a finite graph-like structure. The standard formulation of inverse kinematics problem is then solved using this roadmap. Our current implementation, based on Ariadne's Clew Algorithm, is composed of two sub-algorithms: EXPLORE, an appealingly simple algorithm that builds the kinematic roadmap by placing landmarks in the configuration space; and SEARCH, a local planner, that uses this roadmap to reach the desired end-effector configuration. Our implementation of SEARCH is an extremely efficient closed form solution, albeit local, to inverse kinematics that exploits the serial kinematic structure of serial manipulator arms. Initial experiments with a 7- dof manipulator have been extremely successful.