Robustness of solutions of an infinite-dimensional algebraic Sylvester equation under bounded perturbations

The output regulation problem for distributed parameter systems, see e.g. Byrnes, Lauko, Gillian and Shubov (2000) and Paunonen (2011), and the observer design problem for such systems, see e.g. Emirsajłow (2012), are examples of import ant control problems, where analysis of infinite-dimensional algebraic Sylvester equations plays a crucial role. This paper studies bounded perturbations of the unbounded operators of the algebraic infinitedimensional Sylvester equation. We derive some estimate on the perturbation operator under which the algebraic Sylvester equation preserves a unique solution or, in the control systems terminology, a solution is robust under small bounded perturbations. In our approach we employ the concept of an implemented semigroup, see e.g. Alber (2001) and Emirsajłow (2012), which is a special case of the so-called bi-continuous semigroup, e.g. Farkas (2004).