Improved control performance of sloped rolling-type isolation devices using embedded electromagnets

Abstract

Sloped rolling-type isolation devices incorporating built-in friction damping and pounding preventer have been verified to be effective for mitigation of seismic risks posed to critical equipment and facilities. Although the built-in damping design can effectively suppress excessive displacement responses, it also increases the acceleration transmitted to the protected object above the isolation device. In this study, a novel mechanism using embedded electromagnets is proposed to improve the control performance of the isolation device. By varying the input currents to the electromagnets, the corresponding magnetic force becomes controllable and can appropriately adjust the normal force applied to the sliding interface, leading to indirect semi-active control of friction damping force. The efficacy of the proposed mechanism is verified through several shaking table tests. Experimental results demonstrate that the control target of the isolation device can be semi-actively achieved using the electromagnetic mechanism. Accordingly, a numerical model of such a smart isolation system, the incorporation of the proposed controllable damping mechanism into the conventional sloped rolling-type isolation device, is proposed and calibrated by the experimental data. Its effectiveness and advantage can be clearly observed particularly when appropriate control algorithms are applied to calculating input currents for the electromagnets. Copyright © 2016 John Wiley & Sons, Ltd.