Robust stabilization for SISO linear systems via output feedback

The authors consider the problem of the robust stabilization, via output feedback, SISO linear systems. A dynamic output feedback controller is proposed under the assumptions that the relative degree is known, the system is minimum phase, and the sign of the high-frequency gain and a bound for its modulus are known. The proposed procedure is widely applicable because the dynamics of the system can be completely unknown, e.g., the number of poles, stable and/or unstable, can be unknown and arbitrarily large, and the high-frequency gain is bounded but can be unknown