History of Robotics Research and Development of Japan1984ManipulationManipulator/Research on Manipulability

Tsuneo Yoshikawa

Kyoto University

One of the most important factors we need to consider when we determine the mechanism and size of a robot manipulator at the design stage and when we determine the posture of the manipulator in the workspace for performing a given task at the operation stage will be the ease of changing arbitrarily the position and orientation of the end-effector at the tip of the manipulator. The concept “manipulability” has been proposed for representing this ability quantitatively from the viewpoint of kinematics. Specifically, we consider the set of all end-effector velocities under the condition that the magnitude of the joint velocity vector is not more than 1. Then this set turns out to be an ellipsoid. This set is called the manipulability ellipsoid and its volume is called the manipulability measure. The validity of these concepts for designing manipulators and avoiding singular configurations of redundant manipulators has been shown by various numerical examples. The concept of manipulability has clear physical meaning and can be formulated using the singular value decomposition of the Jacobian matrix. It also has a close relation with the singular configuration of manipulators. Hence this concept has been developed in various directions. For example, (1) developing control strategy and planning trajectory for singularity avoidance of redundant robot mechanisms, (2) manipulability analysis considering the dynamics of the manipulator (dynamic manipulability), and (3) performance evaluation index for designing master-slave systems.

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