Signal and System Norms

Many control objectives can be stated in terms of the size of some particular signals. Therefore, a quantitative treatment of the performance of control systems requires the introduction of appropriate norms, which give measurements of the sizes of the signals considered. Another concept closely related to the size of a signal, is the size of a LTI system. The latter concept is of great practical importance because it is the basis of technical control \(\mathbf{H}_{\infty}\) and the study of robustness (see Chap. 6). These different concepts are detailed in this chapter.