Robustness preserving antiwindup: Examples and counterexamples

An anti-windup scheme is said to be robustness preserving if it inherits the robustness properties of the corresponding unsaturated loop. It has recently been shown in the literature that anti-windup based on internal model control preserves robustness against additive uncertainty. In this paper we illustrate examples where other anti-windup schemes are also robustness preserving. We also demonstrate by counterexample that internal model control need not preserve robustness against multiplicative uncertainty. We consider both single-input single-output and multivariable control loops.