Safety Functionals for Time Delay Systems

This paper considers the stability and safety of nonlinear time delay systems. Utilizing a Lyapunov-Krasovskii functional we state and prove Lyapunov's theorem in its modern form and prove it with the help of the comparison lemma. Based on this we establish the notion of safety functional that allows us to ensure invariance of sets in the infinite-dimensional state space. The applicability of the results are also demonstrated using an illustrative example.