Methods for Safety Verification of Time-Delay Systems

This paper addresses the safety verification of systems with time-delay. It extends the barrier certificate methodology previously proposed for safety verification of systems described by ordinary differential equations to the functional differential equations setting. For verifying the safety of a time-delay system, a functional of states is used as a barrier certificate. The forms of the functionals resemble the Lyapunov-Razumikhin functions or the Lyapunov-Krasovskii functionals used in stability analysis of time-delay systems. When the description of the system is given in terms of polynomials, such a barrier certificate can be searched using sum of squares programming.