Robust output tracking for uncertain/nonlinear systems subject to almost constant disturbances

• Published in: Automatica (Oxford) Vol. 38; no. 11; pp. 1919 - 1926
• Main Authors: Açıkmeşe, Ahmet Behçet, Corless, Martin
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.11.2002
• Subjects: Disturbance rejection; Nonlinear control systems; PI controllers; Robustness; Tracking; Uncertain dynamic systems; Nonlinear control systems; Disturbance rejection; Robustness; Tracking; Uncertain dynamic systems; PI controllers
• ISSN: 0005-1098; 1873-2836
• DOI: 10.1016/S0005-1098(02)00071-7

In this paper, we consider uncertain/nonlinear systems subject to unknown constant disturbance inputs. We wish to design state feedback controllers which ensure that the system output asymptotically tracks a specified constant reference signal and all states are bounded. The controllers we consider are PI in the sense that they consist of a piece which depends linearly on the state and another piece which depends on the integral of the output tracking error. Our main result reduces the original problem to a stabilization problem for an associated augmented system which we call the derivative augmented system. We obtain controller design procedures for specific classes of uncertain/nonlinear systems. Then we extend these results to the situation in which the reference signal and the disturbance are not necessarily constant but asymptotically approach a constant.