With respect to the first edition as Volume 218 in the Lecture Notes in
Con- trol and Information Sciences series the basic idea of the second
edition has remained the same: to provide a compact presentation of some
basic ideas in the classical theory of input-output and closed-loop
stability, together with a choice of contributions to the recent theory
of nonlinear robust and 1foo control and passivity-based control.
Nevertheless, some parts of the book have been thoroughly revised and/or
expanded, in order to have a more balanced presen- tation of the theory
and to include some of the new developments which have been taken place
since the appearance of the first edition. I soon realized, how- ever,
that it is not possible to give a broad exposition of the existing
literature in this area without affecting the spirit of the book, which
is precisely aimed at a compact presentation. So as a result the second
edition still reflects very much my personal taste and research
interests. I trust that others will write books emphasizing different
aspects. Major changes with respect to the first edition are the
following: - A new section has been added in Chapter 2 relating L2-gain
and passivity via scattering, emphasizing a coordinate-free, geometric,
treatment. - The section on stability in Chapter 3 has been thoroughly
expanded, also incorporating some recent results presented in [182J.