Observers for differential-difference representations of discrete-time systems

In this paper an observer design procedure is proposed for nonlinear discrete-time systems. The approach relies on the equivalence to a canonical observer form through coordinates change. The study is based on the description of discrete-time dynamics as coupled differential/difference equations. The equivalence to the canonical observer form is performed through a stepwise procedure worked out on successive polynomial approximations of increasing degree around the linear part. This formulation results in a possibly approximate observer design procedure.