OBSERVER DESIGN FOR NONLINEAR-SYSTEMS WITH DISCRETE-TIME MEASUREMENTS

This paper focuses on the development of asymptotic observers for nonl inear discrete-time systems. It is argued that instead of trying to im itate the linear observer theory, the problem of constructing a nonlin ear observer can be more fruitfully studied in the context of solving simultaneous nonlinear equations. In particular, it is shown that the discrete Newton method, properly interpreted, yields an asymptotic obs erver for a large class of discrete-time systems, while the continuous Newton method may be employed to obtain a global observer. Furthermor e, it is analyzed how the use of Broyden's method in the observer stru cture affects the observer's performance and its computational complex ity. An example illustrates some aspects of the proposed methods; more over, it serves to show that these methods apply equally well to discr ete-time systems and to continuous-time systems with sampled outputs.