Constructions of interval observers for discrete-time systems of Luenberger type

For a class of discrete-time systems with input, output and uncertain terms, a new interval observer is constructed. Its key feature is that it is composed of two copies of classical observers, whose corresponding error equations are in general not nonnegative. It is shown how this interval observer can be modified to cope with the presence of nonlinear terms and disturbances and how asymptotic stability of the resulting interval observer can be achieved through an appropriate choice of output feedback.