Kalle M. Mikkola

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It is known that a matrix-valued transfer function P has a stabilizing dynamic controller Q (i.e., h I −Q −P I i −1 ∈ H ∞) iff P has a right (or left) coprime factorization. We show that the same result is true in the operator-valued case. Thus, the standard Youla–Bongiorno parameteriza-tion applies to every dynamically stabilizable function. We then derive(More)
We generalize the classical theory on algebraic Riccati equations and optimization to infinite-dimensional well-posed linear systems, thus completing the work of George Weiss, Olof Staffans and others. We show that the optimal control is given by the stabilizing solution of an integral Riccati equation. If the input operator is not maximally unbounded, then(More)
During the past decades much of finite-dimensional systems theory has been generalized to infinite dimensions. However, there is one important flaw in this theory: it only guarantees complex solutions, even when the data is real. We show that the standard solutions of many classical problems with real data are also real. We call a (possibly matrix-or(More)
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