Study on Algorithms for Semi-Active Control of Isolation System with Variable Friction

Abstract

The semi-active isolation system with energy dissipating by friction force has been proved effective, and friction force is a natural mechanism of energy disssipation. The proposed control laws are designed by a pre-selected far-field earthquake. These control laws in displacement, velocity and state feedback are investigated numerically. The maximum platform displacements with the proposed three ddifferent kinds of controllers are all smaller than that with the passive system no matter what intensity or seismic waveform is. In acceleration ratio, the proposed control laws can be more effective than the passive system when the intensity is larger than the design earthquake. However, if the intensity is smaller than the design earthquake, the effectiveness of acceleration with the proposed control laws may be worse than or close to the passive one due to the sufficient paassive friction force. Generally, the velocity and state feedback cases with a larger exponent can perform apparently better than the displacement feeedback case. Besides, the state feedback case could perform better than the corresponding individual displacement and velocity feedback cases. These results of proposed simple nonlinear control laws hold true for both far-field El Centro and near-fault Imperial Valley earthquakes.