Metric uncertainty and nonlinear feedback stabilization

Defines a generalization of the gap metric for nonlinear systems. The authors prove two results which specialize to known results for linear systems. First, the authors show that a feedback system remains stable if the distance between the plant and its perturbation is less than the inverse of the norm of a certain parallel projection operator. Second, the authors show that every “continuously robust” metric on nonlinear systems is equivalent to the metric introduced in this paper