| Abstract: | The effectiveness of comprime factor techniques in L2 and L∞ model reduction of unstable linear systems is analysed. Asymptotic estimates are given of the achievable error in the stable and unstable parts of the approximate system, measured in a number of different norms, some involving the associated Hankel operators. The chordal metric is introduced as a measure of approximation and is shown to yield the graph topology. Finally it is deduced that asymptotically optimal L2 and L∞ convergence rates can be obtained for a large class of unstable systems. |
