Compensation of actuator dynamics in real-time hybrid tests

Abstract

Real-time hybrid testing is a novel approach to the dynamic testing of structures, in which the system under test is split into physical and numerical substructures which are tested and analysed in parallel, with data passed between them in real time. The success of a test is highly dependent on the performance of the actuators which provide the interface forces and displacements between the two substructures. This paper presents several numerical schemes to compensate for the non-ideal dynamics of typical servohydraulic actuators and evaluates them through a series of real-time hybrid tests on simple mass-spring systems. It is shown that effective schemes can be developed on the basis of a simple representation of the actuator response as combination of a delay and an amplitude error, both of which can vary during a test. The use of a modified online delay estimator, together with one of three simple forward extrapolation schemes, is found to be highly effective in minimizing experimental errors related to the actuator dynamics.