© 1988 by Institute of Mathematics and its Applications
Perturbation Properties of a Class of Infinite-Dimensional Systems with Unbounded Control and Observation
Rijksuniversiteit Groningen, Mathematisch Instituut Postbus 800 9700 AV Groningen, The Netherlands
We define a class of infinite-dimensional systems with unbounded input and output operators which are closed under state-feedback, output-injection, and output-feedback perturbations. We give an explicit criterion for spectral systems to belong to this class. As an application, we extend the finite-dimensional result on the equivalence of inputoutput stability and exponential stability to this class. The theory is illustrated by a p.d.e. model of a beam with viscous damping.