Design and analysis of a new spherical actuator

Usually, multi-degree-of-freedom (multi-DOF) systems consist of a number of single-DOF actuators, making the structure of these systems complicated. Furthermore, they have a slow response and low positioning accuracy due to their inevitable problems such as a large backlash, non-linear friction and kinematic singularities in the operation range. The number of actuators and the weight of the overall system can be reduced by constructing a single multi-DOF actuator. Multi-DOF actuators are particularly suitable for applications such as robot wrists, elbows, shoulders and eyes. Due to the numerous possibilities, various multi-DOF actuators have been proposed. In this paper, a new multi-DOF actuator which is based on a rotational voice coil motor (VCM) is proposed. Originally, the VCMs are a type of linear DC motor where the mover reciprocates due to the interaction of the coil current and the magnetic flux generated by the permanent magnets in the air gap. The VCMs have a simple operational principle and a certain torque constant. The proposed 3-DOF actuator realize large tilt angle (±40 degree), high tilt torque constant (0.5 Nm/A), and small diameter (80 mm). The effectiveness of the actuator was confirmed through 3-D FEM.