Functional interval observer for discrete-time systems with disturbances.

• This paper further investigates the design problem of the functional interval observer for discrete-time systems with disturbances and mainly has three highlights: • We design an FIO for linear discrete-time systems by using monotone system theory, and the sufficient conditions are presented by Sylvester equations. • The design constraints are reduced and the estimation accuracy is improved by using the zonotope method. • By comparing the two methods, the approach of the zonotope can reduce the constraints of observer design and improve the performance of the proposed FIO. This paper further investigates the design problem of the functional interval observer for discrete-time systems with disturbances. Two methods are given to design functional interval observers. Given monotone system theory, a Luenberger-like functional interval observer is constructed and sufficient conditions are achieved by Sylvester equations in the first method. The second approach is known as the two-step method. An H ∞ functional observer of the system is presented by the H ∞ technique, and then the approach of the zonotope is used to estimate its upper and lower boundaries to improve the estimation accuracy. The above methods are applied to two examples for comparison and to show the correctness. [ABSTRACT FROM AUTHOR]