Robustification tools for nonlinear control design

We demonstrate the usefulness of the so-called κ-terms as a robustification tool for nonlinear control. The inclusion of these terms in the design procedure renders the disturbance-to-state operator bounded without the need for high gain in the control, and can make the gain of the disturbance-to-output operator arbitrarily small. Using this tool, we construct a new design procedure for strict feedback systems whose state measurements are corrupted by bounded multiplicative and additive disturbances, and show that the state of the resulting closed-loop system will remain bounded even if the bounds on the disturbances are unknown