Analysis Accuracy in Positioning Calculation for Three-Degree-of-Freedom Spherical Actuator

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. Each coil input current is calculated using a torque-generating equation based on the torque constant matrix. Although a control method to calculate the current has already been proposed, the analysis accuracy of the torque model is not sufficiently examined for a precision robot that requires a positioning accuracy of 1 mm or less. To apply our three-DOF spherical actuator to such a precision robot, we have developed a dynamic analysis method that directly positions the robot. In this article, we report on the factors that affect the analysis accuracy and accuracy improvement.