Local and remote control measures for networked control systems

In this article we propose a novel approach for networked control systems with unknown constant time delay. A distributed controller is considered, under the assumption that static controllers directly connected to the plant, can be implemented. Stability and sensitivity to time delay goals can be conjointly defined. The necessary and sufficient conditions for the existence of a controller which guarantees delay-independent stability and a frequency dependent maximum of the norm of the sensitivity function with respect to time delay are formulated as a feasibility problem with polynomial matrix inequality constraints. In a numerical example we show that the proposed formulation can give useful solutions in non-trivial cases.