Input-to-state stability for parameterized discrete-time time-varying nonlinear systems with applications

Input-to-state stability (ISS) of a parameterized family of discrete-time time-varying nonlinear systems is investigated. A converse Lyapunov theorem for such systems is developed. We consider parameterized families of discrete-time systems and concentrate on a semiglobal practical property that naturally arises when an approximate discrete-time model is used to design a controller for a sampled-data system. Application of our main result to time-varying periodic systems is presented. This is then used to design a semiglobal practical ISS (SP-ISS) control law for the model of a wheeled mobile robot.