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In a networked control system (NCS), the plant and the controller are spatially separated and the control loop is closed through a communication network. Communication time delay in an NCS degrades the performance and may lead to instability. In this paper, the scattering transformation is applied to NCS, for the first time, in order to guarantee stability in the presence of unknown constant time delay. The scattering transformation approach in its original version relies on the assumption that all subsystems are passive. This paper extends the approach to nonpassive, static-output-feedback-stabilizable plants. We consider linear time-invariant (LTI) systems here. It is furthermore shown that no knowledge of the time delay value is necessary for the analysis and design of the closed-loop system. Lastly, experimental validation shows that the proposed approach is superior to a delay-dependent controller and the Smith predictor, as far as stability, performance, and sensitivity to time delay are concerned.
Date of Publication: Jan. 2009