Analysis and Experimental Verification of a Magnetic Lead Screw Actuator With Step Skew Structure

Actuators for collaborative robots require high power, compact structure, and safety human-robot interaction. Series elastic actuators (SEAs) are expected to apply to the robots. SEAs consist of a mechanical lead screw and spring and are elastic during contact. However, general lead screws have friction, noise, and heat generation problems. We developed a magnetic lead screw actuator (MLSA) with the integrated structure of a magnetic lead screw and synchronous motor to solve these problems. An attractive magnetic force drives the MLSA without mechanical contact. However, the MLSA has a spiral groove structure that is difficult to manufacture, and structural simplification is a remaining problem. This study describes a new MLSA with a step skew structure to simplify the structure. The basic structure and operating principle are described. Using a prototype, a three-dimensional finite element method and experimental verification, the torque and thrust characteristics are evaluated and discussed. To improve the thrust characteristics, the step skew structures with the different splits are compared. Furthermore, the effects on the thrust of the interior permanent magnet arrangements are investigated.