Phase Lag Compensation in Real-Time Substructure Testing Based on Online System Identification

Abstract eng:
In control of real-time substructure tests, time delay or phase lag of actuators is a very important issue. Research on phase lag of actuators shows that phase lag induces negative damping in such tests (Horiuchi et al. 1999). This can cause error and may lead to instability. Thus, phase lag of actuators should be reduced to improve accuracy and performance of real-time substructure tests. Some compensation methods can be used to compensate phase lag in real-time substructure tests. The time delay compensations proposed by Horiuchi et al. (1996, 1999, 2001) use extrapolation techniques to predict displacements for the future. In these methods, there is no feedback mechanism to minimize the error of the prediction. The adaptive polynomial method (Wallace et al. 2005) and the compensation with feed-forward and feed-back control (Spencer et al. 2007) are more advanced since they have mechanisms to minimize error. This paper introduces a new phase lag compensation, which is based on online system identification in the time domain. Since error of movement due to phase lag of actuator is very well related to the dynamic response of the system, this error can be estimated and then compensated. An advantage is that the compensator has a feedback mechanism to minimize the error of estimation and there is a possibility to develop the compensator to cope with time-varying or nonlinear systems. Numerical and experimental results on hydraulic systems with earthquake loads show the applicability of this compensation method for substructure tests in civil engineering.

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