Abstract-First, time-invariant interval observers are proposed for a family of nonlinear systems. Second, it is shown that, for any time-invariant exponentially stable discretetime linear system with additive disturbances, time-varying exponentially stable discrete-time interval observers can be constructed. The result relies on the design of time-varying changes of coordinates which transform a linear system into a nonnegative linear system.

We consider continuous time nonlinear time varying systems that are globally asymptotically stabilizable by state feedbacks. We study the stability of these systems in closed loop with controls that are corrupted by both delay and sampling. We establish robustness results through a Lyapunov approach of a new type.

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