Robustly stabilizing controllers for dissipative infinite-dimensional systems with collocated actuators and sensors

We derive formulas for normalized doubly coprime factorizations over H-infi nity for a class of nonexponentially stabilizable systems. Using these resu lts, we solve the problem of robust stabilization with respect to normalize d coprime factor perturbations for a class of infinite-dimensional systems Sigma(A, B, B*, D), with finite-rank inputs and outputs and dissipative ope rator A; these systems are not exponentially stabilizable. We give a parame terization of controllers that achieve a given robustness margin. (C) 2000 Elsevier Science Ltd. All rights reserved.