Abstract

While robotic dexterity is the common measure of a manipulator’s ability to adequately and effectively position and orient a tool, it is position and direction dependent and therefore variable throughout the manipulator’s workspace. Since the ability to pose (position and orient) is the robot’s fundamental task, a parameter for evaluating this ability over all the workspace, proposed and referred to in this paper as the “dexterous measure,” is extremely important for use in selecting and evaluating manipulators. This work demonstrates that uniformity in dexterity is the essential feature of a dexterous manipulator and thus provides a correct basis for comparison of manipulators, all other factors being equal. Uniformity of dexterity is of tantamount importance because of the ability to select the relative magnitude of dexterity at the actuator level, for example by means of transmission gearing or in actuator selection. Arguments are presented for a holistic evaluation of the dexterous properties of manipulators based on the variation of dexterity over the workspace for a specific task. Application of the new measure is demonstrated by the analysis of three mechanical pointing devices for two common tasks over a hemispherical workspace.

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