Robust Analysis of Networked Control Systems with Time-Varying Delays

In this paper, a comparison of polytopic and norm-bounded approach is sought for stability analysis of networked control systems (NCS) with uncertain time-varying delays. The delays are considered to be general in the sense that these could be either smaller or greater than the sampling time. For stability analysis, first the continuous-time NCS plant is represented remodeled into an equivalent discrete time one. The uncertainties in the NCS model arises due to the time varying delays are modeled using both polytopic and norm-bounded approach. Considering a state-feedback controller, LMI conditions are used to exploit the stability region in the controller and delay parameter plane using two numerical examples. It is observed that the norm-bounded (NB) approach is slightly conservative whereas higher computational complexities are involved in the polytopic one.