Networked Control Systems: A time-delay approach

Networked control systems (NCSs) are spatially distributed systems for which the communication between sensors, actuators, and controllers is supported by a shared communication network. This paper gives an overview of the time-delay approach to NCSs. Firstly, the modelling on the Networked Control Systems (NCSs) with one sensor node is recalled. Then, for the NCSs with distributed sensor nodes and Round-Robin (RR) protocol, the closed-loop system can be presented as a switched system with multiple ordered delays. Next, a continuous-time hybrid system model for the closed-loop system, where time-varying delays appear in the dynamics and in the reset equations, is introduced to NCSs under RR and Try-Once-Discard (TOD) protocols. Lastly, the hybrid system modelling for the closed-loop system is extended to the discrete-time case. Differently from other approaches to NCSs in the presence of scheduling protocols (in the frameworks of hybrid and discrete-time systems), the time-delay approach allows the communication delays to be greater than the sampling intervals.