The performance of delay compensation in real-time dynamic substructuring

Abstract

Real-time dynamic substructuring (RTDS) is a state-of-the-art experimental technique for evaluating the dynamic performance of a structural system subjected to time-varying loads in civil engineering. The accuracy and stability of RTDS is affected by the natural dynamics of the constituent transfer system. Of various control strategies, and due to the merits of simple implementation and low computational cost, delay-compensation methods have become most pervasive. In this paper, the performance of delay compensation based methods for RTDS is assessed in terms of accuracy and stability. Three commonly-used delay compensation schemes are considered: two time variant and one time invariant. Stability is assessed analytically, numerically and experimentally. Accuracy is assessed numerically and experimentally. To provide a suitable test for the delay compensation control schemes, a shaking table is adopted as the RTDS transfer system. It is demonstrated numerically, analytically and experimentally that when applied to transfer systems such as these, delay compensation can work to the detriment of test accuracy and test stability. Adequate performance of delay compensated, shaking-table based RTDS is confined a narrow low frequency bandwidth which severely restricts the range of potential application.

Performance extension of shaking table‐based real‐time dynamic hybrid testing through full state control via simulation

“…Even when the excitation frequency is above 10 Hz, the errors between the desired and achieved response are still acceptable. The measured results in Figures 15 and 6 illustrate that FSCS brings a successful shaking table RTDHT for the experiment with high frequency component, which cannot be achieved by the conventional delay compensation methods as revealed by Tang et al 38 using the same shaking table as this work.…”

“…The control scheme of delay compensation [34][35][36][37] is commonly used to compensate the transfer system dynamics in actuator-based RTDHT because of its simple implementation and low computational cost. As Tang et al 38 reported, delay compensation works only when its underlying assumptions that the magnitude error is near to zero and the phase lag is proportional to the frequency of excitation are met. It can be satisfied in actuator RTDHT.…”

“…Owing to the big mass of the seismic platform, shaking table has a relatively narrow operational bandwidth akin to stand-alone actuator, which results in magnitude error and phase lag non-proportional to the frequency of excitation. 38 In order to compensate for the complex dynamic properties of shaking table, the control methodology based on classical control theory has been tailored for RTDHT. A fifth-order transfer function of shaking table was used to develop an inverse dynamic compensation by Lee et al 13 and gave a good performance when the numerical model of shaking table is adequate.…”

Passivity control for nonlinear real-time hybrid tests

“…Tang et al 6 review some of the state-of-the-art delay compensation schemes used in RtHT. For most schemes, the author concludes that improvements in performance were mostly seen within a narrow frequency range.…”

Passivity-based adaptive delay compensation for real-time hybrid tests

“…However, one of its limitations is that it can only correct for delays which are integer multiples of the timestep. More forward predictive schemes have been developed by several authors over the years such as those seen in the work of Darby et al 2 and Ahmadizadeh et al 3 Tang et al 4 present a review of such techniques and conclude that performance gains are mostly seen within a narrow frequency band as amplitude ratio and phase errors are seen at high frequencies.…”