Experiment and analysis of a fuzzy-controlled piezoelectric seismic isolation system

Because a conventional seismic isolation system is usually a long-period dynamic system, it may easily incur an excessive seismic response when subjected to near-fault earthquakes, which usually contain strong long-period wave components. In order to alleviate this near-fault isolation problem, this paper investigates the possible use of a fuzzy-controlled semi-active isolation system, called a piezoelectric seismic isolation system (PSIS), whose seismic response is attenuated by a variable friction damper driven by an embedded piezoelectric actuator. The studied PSIS adopts a fuzzy controller whose control logic is similar to that of the anti-lock braking systems (ABS) widely used in the automobile industry. This ABS-type fuzzy controller has the advantages of being simple and easily implemented, because it only requires the measurement of the PSIS sliding velocity. In order to investigate its feasibility and isolation effectiveness, in this work both theoretical and experimental studies were carried out on a prototype PSIS. It is observed that the experimental responses of the PSIS can be well predicted by the theoretical responses simulated by the mathematical model and numerical procedure. Furthermore, both theoretical and experimental results have demonstrated that in either a near-fault or a far-field earthquake, the PSIS with the ABS-type fuzzy controller is very effective in suppressing simultaneously the isolator displacement and the acceleration response of the isolated object.