RESEARCH ON THREE-VARIABLE CONTROL TECHNOLOGY OF SEISMIC SIMULATING SHAKING TABLES

The seismic simulating shaking table is a typical electro-hydraulic servo test system and is controlled by a servo valve. The test system is widely used in the structural anti-seismic test. The seismic simulating shaking table usually has a low frequency response and a low damping which greatly limit its application for the wide bandwidth test. To further expand the bandwidth of the seismic simulating shaking table and increase its damping TVC (three-variable control) algorithm is proposed. In this paper, we research the TVC (three-variable control) algorithm for the seismic simulating shaking table, and also analyze its correction actions on the system characteristics of the shaking table achieved by both the TVC feedback and TVC feedforward loops. Then we further verify the improvement effects on the system's frequency response characteristics of the shaking table taken by the TVC algorithm. The algorithm can expand the system bandwidth by introducing a velocity feedback and can increase the system damping by introducing an acceleration feedback. The TVC feedforward loop can eliminate the system poles near to the imaginary axis of system's closed-loop transfer function and can also further expand the system bandwidth. Finally, we conduct two types of tests on a seismic simulating shaking table: sine sweep tests and seismic waveform replication tests. The results of the sine sweep tests show that the TVC algorithm can effectively improve the system's frequency response characteristics of the shaking table and also improve its response speed. And the results of the seismic waveform replication tests show that the TVC algorithm can improve the replication accuracy of the seismic waveform.