This paper covers the energy-saving features of a robotics system by redundant actuation. By installing more actuators than the degrees of freedom, the actuating torques can be distributed This distribution can reduce the overall energy loss, which reduces the overall energy consumption. An experiment was conducted with a 2-DOF general manipulator and redundant actuated manipulator; these were made to follow a typical welding pathway used in an automotive factory. The results showed that the redundant manipulator saved up to 38% electrical energy for actuation compared to the general manipulator.

A kinematic optimization procedure for redundantly actuated parallel manipulator is developed to ensure the isotropic antagonistic stiffness in a workspace. The kinematic parameters of the mechanism are optimized to maximize and equal out antagonistic stiffness of the redundantly actuated manipulator when size and shape of the usable workspace are given but position in the entire workspace is not. The proposed procedure is verified with a 2-DOF planar manipulator by experiments. The experimental results show that the proposed procedure is useful for designing the redundantly actuated parallel manipulator with isotropic antagonistic stiffness in a predefined usable workspace as a design constraint.

In this paper, two torque assignment methods of the antagonistic stiffness for a 2-DOF planar parallel manipulator are presented and verified by experiments. The first method is equalizing the magnitude of the stiffness in all directions at a desired position. The second method is maximizing the active stiffness in one direction at a given path. A 2-DOF parallel mechanism with four actuators is used for verification tests, where the internal torque of the mechanism exists on the two dimensional null space. In the experiment, passive and active stiffness are tested when endowing the external force at the moving platform and compared with the estimated results.