Coupling Mechanism and Compensation Control Method for a Frequency Bandwidth Expansion Compound Shaking Table

The frequency bandwidth expansion compound shaking table (FBECST) provides an effective solution for synchronously achieving large-load, long-stroke, and wide-band excitation. FBECST consists of an upper shaking table (UST) and a lower shaking table (LST) cooperating to realize the compound excitation, which results in a high system complexity compared to the traditional shaking table. However, the coupling mechanism and model-based compensation control method of FBECST have rarely been studied, which greatly limits the ability of FBECST to simulate earthquake excitation. In this paper, a closed-loop transfer function matrix theoretical model of FBECST is developed. Then, the coupling mechanism of FBECST is revealed by theoretical analysis, and the correctness of the mechanism analysis is verified by simulation. Finally, a closed-loop feedforward decoupling compensation control (C-FDCC) method based on the coupling mechanism of FBECST is proposed. A series of numerical analysis results show that even considering the influence of a high natural frequency specimen, the proposed C-FDCC method can achieve good control precision with a time-domain correlation coefficient near 0.98, whereas the three-variable control(TVC) provides insufficient control. This work provides strong support for large-load, long-stroke, and wide-band seismic excitation reproduction through the FBECST.