Predictive control of smart isolation system for precision equipment subjected to near-fault earthquakes

Recent studies have revealed that a conventional passive seismic isolation system may induce an excessive base displacement when it is subjected to a near-fault earthquake that possesses strong long-period components. In order to improve the performance of seismic isolation used for the protection of precision equipment, a smart isolation system (SIS) that combines an isolation platform with a variable friction device is proposed in this study. The friction force of the variable damper is adjustable in response to the external excitation. In order to effectively regulate the friction force of the variable damper, a predictive control law, which is able to keep the friction damper activated and in its slip state throughout an earthquake with arbitrary intensity, was also derived. The performance of the SIS with predictive control for seismic protection of precision equipment was investigated numerically. The practical concerns about the effects of modeling error and measurement noise on the SIS were also studied. The simulation results demonstrate that in near-fault earthquakes, the SIS effectively reduces the equipment acceleration and prevents an excessive isolator displacement. This usually cannot be easily achieved by a passive isolation system.