Consideration on mechanical properties of a Redundant Drive manipulator for reducing the endpoint inertia

The basic structure and the impedance control of Redundant Drive Joints with Double Actuation, RDJ-DAs, have been proposed to produce compliant joint motions with a higher bandwidth. Although RDJ-DAs could reduce the inertia of the actuators, it cannot reduce the inertia of the output link. In this paper, we propose a basic structure of Redundant Drive Manipulators, RDMs, which can reduce the total endpoint inertia. Therefore, the RDMs can be proper to produce compliant motions with a higher bandwidth. First, a problem statement on mechanical design in order to produce compliant motions is described using a basic 1-DOF manipulator, where its endpoint inertia is calculated under the specified condition to produce the endpoint force. Second, we discuss how a proposed RDM can reduce a set of joint and link inertias along the moving direction, comparing the inertias of a simple 1-DOF manipulator, a 1-DOF manipulator with RDJ-DA, and a proposed RDM. Then, the effects of the design parameter which determines the ratio of the joint torque used for driving the second joint are discussed in details.