Robust control of time-variant systems with time-varying delay and nonlinear perturbations

This paper considers the problem of robust stabilization of a general uncertain time-varying system with time-varying delays. The system does not need to satisfy the so-called matching conditions. The uncertainties may appear in the state, control, statedelay, and control-delay. Sufficient conditions, in terms of a critical mismatch threshold, which guarantee closed-loop system stability are given. Under the conditions, feedback controller gains can be constructed from the knowledge of the upper bounds of the time-varying delay and uncertainties.