Title :
Robust approximate control of time-varying uncertain nonlinear systems
Author :
Motlagh, M. R Jahed ; Motlagh, R. Banirazi ; Bolandi, H.
Author_Institution :
Dept. of Electr. Eng., Iran Univ. of Sci. & Technol., Tehran, Iran
Abstract :
We present an approach for control of a class of nonlinear systems with unknown, time-varying parameters or disturbances whose bounds are known, but are not required to enter linearly in the state equations. Control scheme is presented for nonlinear systems which fail to have a well defined relative degree, minimum phase property, and feedback linearizability condition. Therefore, this scheme is applicable to a wide class of nonlinear systems. By a Taylor series of the system about the nominal parameter vector coupled with the approximate feedback linearization concepts and subject to a structure matching condition, it is proved that the presented control law leads to an asymptotically stable closed loop system with bounds on tracking error. Also, when the nonlinear system has a well defined relative degree and is minimum phase on its operating range, the tracking error converges exponentially to zero. Furthermore, we present a parallel scheme for robust state regulation. It is proved that the regulation error converges exponentially to zero
Keywords :
asymptotic stability; closed loop systems; feedback; linearisation techniques; nonlinear control systems; robust control; time-varying systems; tracking; uncertain systems; Taylor series; approximate feedback linearization; asymptotically stable closed loop system; disturbances; minimum phase system; nominal parameter vector; regulation error convergence; robust approximate control; structure matching condition; time-varying uncertain nonlinear systems; tracking error bounds; tracking error exponential convergence; unknown time-varying parameters; Control systems; Feedback loop; Linear approximation; Linear feedback control systems; Nonlinear control systems; Nonlinear equations; Nonlinear systems; Robust control; Taylor series; Time varying systems;
Conference_Titel :
American Control Conference, 1999. Proceedings of the 1999
Conference_Location :
San Diego, CA
Print_ISBN :
0-7803-4990-3
DOI :
10.1109/ACC.1999.786310