Evaluation of manipulators based on a kinematic accuracy index considering task-directions

Some manipulation tasks have directions of required manipulator's motion, and directions for which kinematic accuracy is required in the motion. This paper proposes an index (KAIT: Kinematic Accuracy Index for Task-directions) that allows us to evaluate the kinematic accuracy of manipulators considering the task-directions. The KAIT is applicable to tasks which require consideration of not only the position of the manipulator's endpoint but also the orientation of it. First, we derive the KAIT. Second, we evaluate some postures of a 2-degrees of freedom (DOF) planar manipulator on the basis of some indices that have been proposed (Salisbury's condition number, Yoshikawa's manipulability measure and Chiu's task compatibility) and the KAIT, respectively. Further, we evaluate some postures of a 3-DOF planar manipulator on the basis of the KAIT. Finally, from the evaluation results, we discuss the usefulness of the KAIT.