Dynamics of a non-hysteretic superconductive passive magnetic linear bearing

In the present work the dynamical behavior of a magnetic levitating linear bearing suitable for working in the non-hysteretic range of forces is presented. The presented bearing device is composed of a high temperature superconductor with semi-cylindrical shape and a levitating slider made of a permanent magnet. Meissner repulsion forces of the superconductor provides stable equilibrium and restoring forces in 4 degrees of freedom (DOF), allowing the magnet to displace linearly along the axis of the superconducting semi-cylinder. A custom-made model based on numerical integration of coupled electromechanical equations has been developed, demonstrating good accuracy between the solution obtained and commercial FEM software ones. Radial and axial stiffness of the bearing have been calculated using this model. The vertical equilibrium as a stable position of the linear bearing displacement was found. Dynamical and transient simulation was done in order to determine the position of the levitating magnet for different external perturbations. Moreover, the calculation of the maximum pressures and thus the magnetic field applied for each position of the displacement proves that it can operate at 100 K or below. It can be assured that a complete Meissner state occurs; hence the displacement will be completely non-hysteretic. Such a non-hysteretic passive linear bearing can be very suitable for long-stroke precision positioning. The high translational symmetry of the magnetic field seen by the permanent magnet assures a usable long stroke of around ± 90 mm with full performance and ± 150 mm with reduced performance. This linear bearing in combination with an actuating system for only one DOF can be used for accurate precision positioning systems for cryogenic environments with zero hysteresis in the movement.