Indicators of stability, performance and robustness

Abstract

It is well-known that characteristic values (eigenvalues) are of fundamental importance for assessing the closed-loop stability of a system. For the assessment of performance, however, principal gains (singular values) are used for they give a more accurate measure of gain. In this chapter, it has been shown that the divergences between the magnitude of characteristic values and principal gains give an indication of the normality of a system. A normality indicator MS is defined and its relationship with gain divergences is also demonstrated.