Robust real-time substructuring techniques for under-damped systems

This paper considers the hybrid simulation of under-damped dynamical systems using numerical–experimental real-time substructuring. Substructuring joins together a physical plant with a numerical model using real-time control techniques, such that the combined model emulates the behaviour of the entire system. Due to the low damping, the control of substructured systems can be highly sensitive to delay and uncertainty. We present a technique for calculating the critical delay of the substructured system using a phase margin approach. In addition, it is shown that robustness techniques, drawn from feedback control theory, can be used to reduce the destabilising effect of uncertainty. To demonstrate this, a comparison of three different robustness compensators is presented, using a well-known linear system. The level of uncertainty is deliberately increased to compare their performances and a discussion is made on when each may be most useful. Copyright © 2006 John Wiley & Sons, Ltd.