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SUMMARY Real‐time pseudodynamic (PSD) and hybrid PSD testing methods are displacement controlled experimental techniques that are used to investigate the dynamic behaviour of complex and load rate‐dependent structures. Because the imposed command displacements are not predefined but generated during the test based on measured feedback, these methods are inherently prone to error propagation, which can affect the accuracy and even the stability of the entire experiment. As a result, to have these experimental methods as reliable tools, the accuracy of the test results needs to be assessed by carefully monitoring, and if possible, quantifying the errors involved. In this paper, phase and amplitude error indices (PAEI) are introduced to identify the experimental errors through uncoupled closed‐form equations. Unlike the indicators that have been previously introduced in the literature for error identification purposes, PAEI do not use test setup specific parameters in their formulation, and can quantify the errors independent of the amplitude of the command displacements. As such, PAEI can be used as standard tools for assessing the quality of the experiments performed in different laboratories or under different conditions. Additionally, because they can quantify the error, when implemented online, PAEI have the potential to be incorporated in the control law and thereby improve the actuator control during the tests. The formulation and implementation of PAEI are provided in this paper. The enhanced performance of the proposed indices is demonstrated by processing several different measured and command signals using PAEI and comparing the results with those revealed by the previous indicators. Copyright © 2011 John Wiley & Sons, Ltd.

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Real-time hybrid simulation (RTHS) is a testing method which combines the response from an experiment (i.e., experimental substructure) with that of a computer model (i.e., analytical substructure) in real-time. The accuracy and stability of the RTHS are prone to the propagation of error in the measured signals. Thus, critical developments in servo-hydraulic actuator control are needed to enable a wide application of this testing technique. In this study, a new tracking error compensation strategy for servo-hydraulic actuator control is developed, and numerically and experimentally evaluated. This compensation procedure is formulated based on a new set of tracking error indicators, namely, frequency domain-based (FDB) error indicators, which uncouple phase (lag and lead) and amplitude (overshoot and undershoot) errors and quantify them. These indicators are then incorporated into a two degree-of-freedom (d.f.) controller to develop closed-form equations to design an adaptive servo-hydraulic controller with improved tracking performance. The FDB indicators and the new adaptive controller are studied through numerical simulations in Simulink and LabVIEW and also verified experimentally. The proposed controller is computationally efficient, it can be implemented in real-time and it does not require any user-defined (i.e., predetermined) coefficients. As a result of its two d.f. formulation, this adaptive controller can be introduced to any closed-loop servo-controller through a digital or analog interface depending on the experimental setup properties. As such, it can be used to improve the tracking capability of any single hydraulic actuator system, which is essential in RTHS.

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