Assessment of controller strategies for real-time dynamic substructuring of a lightly damped system

The concept of real-time substructuring enables a complex engineering system to be tested via physical experimentation on one of its subcomponents, which then interacts with a numerical model of the remaining parts of the overall system. In the present paper, the substructuring technique is used to emulate a two degree-of-freedom mechanical system which has a low level of damping. The numerical model displacement, determined at the interface between the physical and numerical components, is used by a substructuring controller to impose the same displacement onto the physical component. This is achieved via a servohydraulic actuator, with the simultaneously measured reactive force at the interface being passed back to the numerical model, using a load cell attached to the physical test rig. In this paper, several forms of controllers are proposed to compensate for the substructured system actuator dynamics, thus ensuring minimal interface error between the two components for accurate emulation of the complete system. Experiments are presented to illustrate the performance of these controllers, which ranged from fixed-gain linear algorithms to an adaptive scheme. Analysis of the results highlight the salient features of substructuring and substructured system control for lightly damped systems.