Model reduction of large-scale systems in the neighborhood of crossover frequency

A new model reduction concept and approach is proposed. In this approach the order of a large-scale system is reduced in the neighborhood of crossover frequency in order to retain stability and performance of the full order system. This concept very closely preserves the gain and phase of the original system. In this approach, the full order system is perturbed and reduced within its specified frequency bandwidth. The concept is applicable to both open and closed-loop systems. To illustrate the effectiveness of the proposed concept and approach a benchmark 4th order plant model is reduced to a 2nd order. For the same 4th order system, two distinct approaches are applied to design two distinct 2nd order H_∞ controllers. The simulation results of the two controllers are compared.