Configuration control of redundant manipulators: theory and implementation

A simple approach for controlling the manipulator configuration over the entire motion, which is based on augmentation of the manipulator forward kinematics, is presented. A set of kinematic functions is defined in Cartesian or joint space to reflect the desirable configuration. The user-defined kinematic functions and the end-effector Cartesian coordinates are combined to form a set of task-related configuration variables as generalized coordinates for the manipulator. A task-based adaptive scheme is then utilized to control directly the configuration variables so as to achieve tracking of some desired reference trajectories throughout the robot motion. This accomplishes the basic task of desired end-effector motion, while utilizing the redundancy to achieve any additional task through the desired time variation of the kinematic functions. Simulation results for a direct-drive two-link arm are given to illustrate the proposed control scheme. The scheme has also been implemented for real-time control of three links of a PUMA 560 industrial robot, and experimental results are presented and discussed. The simulation and experimental results validate the configuration control scheme, and demonstrate its capabilities for performing various realistic tasks