OUTPUT TRACKING CONTROL OF UNCERTAIN NONLINEAR 2ND-ORDER SYSTEMS

The solution of a tracking problem for a second-order nonlinear system with uncertain dynamics and incomplete state measurement is obtained by means of a procedure directly inspired by the solution of the class ical minimum-time optimal control problem. Two different types of unce rtainty are considered in the paper: in the first case a constant boun d on the uncertain dynamics is assumed to be known; in the second case , the bound is a function of both the measurable and the unmeasurable state variable of the system. In both cases, the possibility of applyi ng the proposed control algorithms is proved to be determined by a pro per choice of the control signal features. The resulting system is cha racterized by a suitable feedback switching logic and the convergence of the system trajectory to the desired one (or to a delta-vicinity of this latter) is proved also in the uncertain case. (C) 1997 Elsevier Science Ltd. All rights reserved.