On the robustness of sampled-data control to unmodeled high-frequency dynamics

Robustness of sampled-data control designs to unmodeled high-frequency dynamics is studied using singular perturbation theory. It is argued that when the plant is preceded by a zero-order hold, a direct transmission term of the reduced-order model, which results from neglecting high-frequency dynamics, should be modeled as a delay element in order to ensure robustness