Design Considerations for a Radially Magnetized Permanent Magnet Worm Drive Actuator

In this paper, a worm drive actuator (WDA) is proposed and design considerations for the development of its experimental prototype is presented. The WDA is basically a permanent magnet synchronous motor (PMSM). It consists of multiple stator-worm and a centrally positioned wheel. As the name suggests, in both mechanism and structure it mimics the mechanical worm drive gear. However, while the worm gear has threads wound on its worm and wheel, those of the WDA contain appropriately shaped, radially magnetized permanent magnets (PMs). This project is an extension of a linear actuator based on the magnetic screw concept. The authors hope for adoption of this technology in mechatronics applications, namely robots and industrial machines, where direct-drivable actuators that can support complex joints, in addition to providing multiple degrees of freedom (DOF) are desirable. Three-dimensional (3-D) finite element analyses (FEA) computed for the linear version of this device show a high force density capacity of up to 6 MN/m(3). Estimates show that torque capable of being delivered to the wheel by a single stator-worm could be up to 10 N.m.