Quantitative analysis of time-varying delay for real-time hybrid simulation

Real-time hybrid simulation is an effective method to study the seismic performance of large or complex structures. Time delay of the hydraulic servo system is unavoidable, which affects test accuracy and may cause instability. Previous studies shown that the reality of time-varying delay has a substantial negative effect on system stability than the assumption of constant delay. However, there is currently a lack of research for the actuating system with time-varying delay in the reality time domain. Therefore, a quantitative analysis method of time-varying delay is proposed in this study. The advantage is that only the command and the measured displacement signals are needed to obtain the time-varying delay in the time domain without any prior knowledge of the system. To overcome the influence of the amplitude error on the solution results, a processing method for the amplitude modulation of the measured displacement is proposed. To accurately search for the command corresponding to the measured signal, it is proposed to solve the time-varying delay by taking segment operation on the signal according to the maximum and minimum points. The efficiency of the proposed method is verified by numerical simulation, actuator displacement tracking test, and RTHS.