Structural and Analytical Modeling of a Long Stroke Variable Stiffness Magnetic Spring with Application to Wave Energy Converter

In this paper, a new structure of long-stroke variable stiffness magnetic spring (MS) applied to wave energy converter device is proposed, and the corresponding analytical model (AM) is presented according to its structure. The main part of the MS consists of an inner mover, an outer stator and a back iron, and the main part is connected to a stepper motor through a shaft, and the stepper motor rotates the intermediate shaft so as to control the change of the stiffness of the MS. The simulated stroke of the MS is 120mm and the maximum elasticity is about 1.7kN. Then an AM combining surface current method and equivalent magnetic circuit method is proposed for the structure of MS. The accuracy of the AM can be verified by comparing the AM with the finite element method (FEM).