Discrete-time adaptive control of output-feedback nonlinear systems

We propose a novel approach which guarantees global stability and regulation for the class of discrete-time output-feedback nonlinear systems. There are no growth conditions imposed on the nonlinearities; however, since we assume that only the output is available for measurement, the nonlinearities are required to depend only on that output. Our approach represents a drastic departure from traditional "certainty-equivalence"-based schemes, since it adopts a two-part control strategy which begins with a finite-duration active identification phase followed by the actual control phase.