I. Introduction
Stabilization problem of linear or nonlinear dynamic systems with time delay is receiving much attention. The existence of a delay in a nonlinear system may induce more complex dynamical behaviors such as instability, oscillations, and chaos, e.g., in Mackey-Glass model [1] and Chua's circuit system with delay [2]. Some important control methods have been developed for stabilizing dynamic systems without delay or with delay, which include state feedback control [3], [4], adaptive control [5], fuzzy control [6], variable structure control [7], etc.