Model reduction of large space structures using approximate component costanalysis

State-space model reduction methods, such as the component cost analysis (C CA), requires the solution of Lyapunov equations of order equal to the orde r of the system. However, for many engineering applications, the storage re quirements and computational time needed for the solution of such large Lya punov equations is often prohibitive. In this work, the use of Krylov-subsp ace iterative methods is examined to obtain low-rank approximate solutions of Lyapunov equations for use in CCA model reduction of large space structu res. The methods are applied to obtain reduced-order models of the Internat ional Space Station multibody assembly stages for simulation and control pu rposes. In addition, closed-form expressions for cost-equivalent and cost-d ecoupled realizations are derived based on the approximate Lyapunov solutio ns. It is shown that using the proposed methods, approximate CCA reduced-or der models can be obtained with a significant reduction in the computationa l effort and time.