Shaking table tests are the most direct experimental way to evaluate structure performance in earthquake engineering. Because of the complexity of the control systems and the influence of specimen behavior, it is difficult for a conventional controller, whose parameters are fixed, to achieve accurate tracking performance for different reference input signals under different payloads. In this paper, a two-loop control method is proposed by combining three-variable control and model reference adaptive control based on Lyapunov stability theory. The proposed control method can adjust the time-domain drive signal adaptively to improve the tracking accuracy and the robustness to specimen uncertainties. Numerical simulations of a small-scale shaking table are used to verify the effectiveness, and the performance of the controller is compared with that of the conventional three-variable control controller. The simulation results demonstrate that the proposed two loop control method provides better performance in both the time and frequency domains.

Summary The Friction Pendulum System (FPS) isolator is commonly used as a base isolation system in buildings. In this paper, a new tunable FPS (TFPS) isolator is proposed and developed to act as a semi‐active control system by combining the traditional FPS and semi‐active control concept. Theoretical analysis and physical tests were carried out to investigate the behavior of the proposed TFPS isolator. The experimental and theoretical results were in good agreement, both suggesting that the friction force of the TFPS isolator can be tuned to achieve seismic isolation of the structure. A series of numerical simulations of a base‐isolated structure equipped with the proposed TFPS isolator and subjected to earthquake ground motions were also conducted. In the analyses, the linear quadratic regulator (LQR) method was adopted to control the friction force of the proposed TFPS, and the applicability and effectiveness of the TFPS in controlling the structure's seismic responses were investigated. The simulation results showed that the TFPS can reduce the displacement of the isolation layer without significantly increasing the floor acceleration and inter‐story displacement of the superstructure, confirming that the TFPS can effectively control a base‐isolated structure under earthquake ground motions.