Unique Joint Displacement Generation for Redundant Robotic Systems

摘要

Abstract This paper presents a novel, practical, and theoretically sound kinematic control strategy for redundant serial manipulators. This strategy yields repeatability in the joint space of a redundant serial manipulator whose end effector undergoes some general cyclic type motion. This is accomplish by defining a potential energy function that is based on springs being theoretically or conceptually located in the joints of the manipulator (torsional springs for revolute joints, translational springs for prismatic joints). Previous researchers have also minimized potential energy functions to solve the inverse kinematic problem for redundant serial manipulators. However, to the authors’ knowledge, the new strategy is the first to include the free angles of torsional springs and the free lengths of translational springs. This is important because it provides a meaningful reference for zero potential energy i.e. when all joints are at their free angles or free lengths. This reference for zero potential energy ensures the repeatability in the joint space of a redundant serial manipulator whose end effector undergoes a cyclic-type motion. Choices for the free angle and torsional stiffness of a joint (or the free length and translational stiffness) are made based upon the mechanical limits of the joint. For instance, the free angle of a joint is that angle which is midway between joint limits. Joint stiffnesses are chosen so that the most dexterous joint is the most pliable, and so that the least dexterous joint is the stiffest. This strategy ensures that joints of the manipulator are kept away from their respective joint limits.