Abstract
A three-degree of freedom (DOF) same-stiffness permanent magnetic spring is proposed, which comprises three groups of permanent annular and cylindrical magnets. The three groups of magnets are symmetrically arranged on a concentric circle. In each group, the permanent cylindrical and annular magnets are coaxial and the same magnetic poles are opposite. The repulsive force in the radial direction is regarded as the magnetic spring force between the permanent cylindrical and annular magnets. The repulsive forces of three groups of magnets can realize the three DOF same-stiffness magnetic spring forces on a plane. In this paper, a mathematical model of the magnetic spring force is established for one group of magnets. The mechanical characteristics of the magnetic spring force are analyzed by calculations with the mathematical model, simulations with the FEM (finite-element method) model, and verifications with the experimental prototype. The results suggest that the force characteristics of the magnetic spring resemble those of a mechanical spring and the different stiffness of the magnetic spring force can be obtained by changing the structural parameters.