This paper discusses the demonstration of a stable levitation (SL) system for a magnetic levitation type seismic isolation device using a high-temperature superconducting (HTS) bulk. The SL system utilizes a restoring force between an HTS bulk and permanent magnet (PM) to maintain the stable levitation of a base-isolation object. We first measured the restoring force between the HTS bulk and PM, and then demonstrated the performance of the SL system using a magnetic levitation type seismic isolation model device with a radial arrangement of HTS bulks and a PM rail. The SL system with the HTS bulk can reduce small vibration and displacement during the normal period of operation without experiencing a large disturbance. We also demonstrated that, when a large disturbance was applied, the transmission of horizontal vibration to the base-isolation object via the SL system was eliminated by decoupling the magnetic coupling between the HTS bulk and PM. Furthermore, the vibration transmissibility at any vibration frequency to the base-isolation object was reduced by incorporating an HTS bulk damper and eddy current damper in the model device. These results suggest that a SL system used together with an HTS bulk can realize both the stable levitation of a base-isolation object during the normal period of operation as well as the elimination of the horizontal vibration transmission when a large vibration is applied.
