Augmented Lyapunov functional for the calculation of stability interval for time-varying delay

The stability problem of systems with a time-varying interval delay is investigated. An augmented Lyapunov functional is introduced to establish some improved delay-dependent stability criteria using a simple and alternative proving method. It is shown that some recently published results are the special cases considered here. The resulting criteria are extended to the stability analysis of systems with time-varying structured uncertainties. A numerical example is given to demonstrate the benefits and effectiveness of the proposed method.