Improvement of Analysis Accuracy in Torque Calculation of Multi-Degree-of-Freedom Spherical Actuators

Multi-degree-of-freedom (multi-DOF) spherical actuators have been developed for the fields of robotics and industrial machinery. We have proposed an outer rotor type three-DOF spherical actuator that can realize a high torque density. Its input current of each coil is calculated using the torque generation equation based on the torque constant matrix. Although a control method to calculate the current value has already been proposed, the analysis accuracy of the torque model is not sufficiently examined for a precision robot that requires the positioning accuracy of about 0.1 mm. In this paper, for the purpose of applying our three-DOF spherical actuator to such a precision robot, we investigated the factors that affect the analysis accuracy of a dynamic analysis method and improved the analysis accuracy.