On Unknown-Input Observer Design for Linear Discrete-Time Positive Systems

The objective of this paper is to outline some problems in solving the unknown-input observer design task for linear discrete-time positive systems. Exploiting the set of linear matrix inequalities, warranting the strictly positive structure of the observer system matrix, the conditions are specified to construct such an observer for positive system states and outputs. Because the principle of matrix pseudoinverse leads in this case to the formulas with rank-deficient matrices, some related properties are deduced to demonstrate diagonally conditioned observability of positive systems.