Control of Manipulators With Redundancy

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This project addresses research in the control of redundant manipulators. Manipulators currently in use are configured with six degrees of freedom, which is the minimum number of joints required to achieve an arbitrary position and orientation of the end effector. However, due to singularities throughout the manipulator workspace, a six degree of freedom manipulator is functionally only a five degree of freedom manipulator. This research examines the utilization of additional, or redundant, degrees of freedom to contend with singularities, and to avoid obstacles and joint and torque limits. Four basic issues are addressed herein, including : a) determination of self motion (joint motion which does not cause end effector motion) to optimize performance criteria, b) optimization of performance criteria for redundant manipulators (smooth switching from one criteria to another and assignment of varying weights to different criteria), c) task based utilization of redundancy resulting in joint configurations requiring lower joint torques, and d) automatic adjustment of end effector speed to avoid obstacles, singularities, and joint limits. This research should expand the application of redundant manipulators to a wider range of tasks requiring high speed and dexterity, thus justifying the additional cost associated with redundant joints.