Robust stability analysis of sampled-data control systems with input delay

The robust stability analysis of sampled-data control systems with continuous-time input delay is considered. Based on the verification and analysis of the approach in the former literature, the conservativeness is pointed out, and then an improvement plan is proposed. By using an equivalent discrete-time uncertainty to replace the continuous-time uncertainty, the analysis for sampled-data control system is transformed into analysis for traditional discrete-time control system, and the resulting conservativeness is thus greatly reduced. In order to provide a simple and intuitive robust stability analysis method, the sampled-data control system with input delay is regarded as the interconnection of two parts. One is the delay-independent sampled-data control system, and the other is dependent on the uncertain delay. The frequency response of the delay-independent sampled-data control system is computed, and then the robust stability uncertainty delay is determined according to the frequency characteristic of these two parts. The proposed method is not conservative. An example is given in the paper for further verification and comparison with the approach in the former literature.