Comments on "Stabilization and estimation for perturbed discrete time-delay large scale systems

In the above-mentioned paper (Wang and Mau, 1997), the authors have developed a criterion to guarantee the robust stabilization and state estimation of a class of discrete-time interconnected systems. They have claimed that the developed criterion is independent of the time delay and that the unknown delay is constant but unknown. This paper highlights an error in the paper which can only be remedied by stating that the delay factor is a known constant.