Linear Vernier actuator with two movers

Background: Linear motion devices for industrial machines and robots are expected to realize their high efficiency drive and simple structure. Usually, a feed screw mechanism composed of a rotary motor and a ball-screw or slide-screw is employed. However, it has some problems such as the decrease of the drive efficiency, flexibility against external forces, noise, etc. Various linear actuators and motors have been developed utilizing the feature of a direct drive. Aim: In this paper, we propose a novel linear actuator which 2 movers can be independently controlled using 3-phase and 6-phase superimposed currents for decreasing the size and weight of the system. The proposed linear actuator is driven by the operating principle of a vernier motor which is expected to achieve a high thrust force density per permanent magnet volume. Methods: The operating principle and the static thrust force characteristics of the proposed linear actuator are verified by an electromagnetic field analysis using 3-D finite element method, and the back electromotive force characteristics are also analyzed. In addition, the dynamic characteristics under position feedback control are analyzed. The control system uses a vector control using PID controller, and the control input is given by the 3-phase and 6-phase superimposed currents. Results: The static force characteristics were investigated. From the analyzed results, the force interference between the two movers was small. Moreover, the interference of the back electromotive force of the 3-phase and 6-phase movers were not observed. The movers could be independently driven under position feedback control using 3-phase and 6-phase superimposed currents. The dynamic characteristics analyses showed that the mover well followed a target position. From a step response, the time constant and the response of the position feedback system were investigated. Conclusion: This paper presents a linear vernier actuator with two movers. The basic structure and operating principle of the actuator were described. Moreover, the static characteristics and the dynamic characteristics under position feedback control were analyzed. It was found that the movers can be independently driven.