Modelling and Control of Discrete Halbach Magnetic Screw for Wave Energy Application

Magnetic screws utilize permanent magnets for a contact-free power conversion between a low-speed, high-force linear motion and a high-speed, low-torque rotational motion. Arranging the permanent magnets in a discrete Halbach structure can increase the power transfer capability. This article proposes control methods for the discrete Halbach magnetic screw. First, a model for the discrete Halbach magnetic screw is developed. Then, the classical control of magnetic screws using PI controller is presented. Finally, two controllers are proposed. These include the proportional resonant controller and the observer-based state feedback with integral action and reference feedforward controller. Simulation results showed that the state feedback controller has improved performance compared to conventional control.