Effects of magnetization conditions on dynamic characteristics of spacecrafts with superconducting flux pinning docking interfaces

Depending on the self-stable levitation characteristics of superconductors with trapped magnetic flux, superconducting flux pinning docking interfaces (FPDIs) provide a promising approach for space applications. In this paper, we investigate the influence of magnetization conditions on the dynamic response between two satellites equipped with FPDIs. The flux pinning interactions between a high-temperature superconductor and a source magnet are approximated using a frozen image model. An analytic model of the docking process is derived based on the Kane method to simulate the dynamic response. A linearized dynamic model is derived, and linear quadratic regulator (LQR) control is applied to the FPDI to minimize the relative attitude deviations. The results show that improving the frozen magnetic flux density of superconductors is beneficial to the capture ability of the FPDI. Increasing the damping coefficient is also an efficient approach to improving the docking performance, but this approach is limited by the field cooling height. Damping materials with a lower density and a higher damping coefficient are proposed to be employed in the FPDI. The LQR control contributes to suppressing the amplitude of the oscillation and reducing the settling time in the docking process. Although the amplitude of oscillation in a noncontrol scheme converges more slowly than the LQR control scheme, it does not require the high dynamic response speed of a control system like the LQR control scheme, which contributes toward simplifying the structure of the FPDI. The principles presented above provide a guide for the design and implementation of FPDI in space docking missions.