Discrete-time modelling methodology of networked control systems under packet delay and dropout

Models and control techniques for networked control systems (NCSs) can be divided into continuous-time and discrete-time types. Unlike the continuous-time analysis, literature on discrete-time analysis and control of NCSs under packet delay and dropout shows a variety of different models. However, a systematic study of these models is absent in the literature. This article is a methodology for these models. Different factors involved in making this variety are discussed. The models are described and it is shown how they are different or related to each other. The models are from the existing literature. However, to complete the methodology some of the models are introduced by the authors. Furthermore, the concept of sequence matrix is introduced which helps to differentiate some models and should be considered when NCS is analysed as a switched linear system. This methodology can be used as a basis for selecting the suitable model in analysis and design of NCSs. Denial of service (DoS) attack and time delay switch (TDS) attack can be considered as packet dropout and packet delay respectively. Thus, this methodology can also be used in analysis and design of NCS under these cyber-physical attacks.