Input-output decoupling of discrete-time nonlinear systems by dynamic measurement feedback

The paper addresses the input-output decoupling problem for discrete-time nonlinear systems. The algebraic method based on difference algebra and differential forms is used to solve the problem by measurement feedback, i.e., by feedback depending only on some measured functions of state variables. Constructive necessary and sufficient solvability conditions are given separately for cases when the system is described by the state equations or by the input-output equations. By specifying the measured functions, one recovers the known conditions for the state feedback or obtains the conditions for the output feedback solution.