Method for Approaching the Cyber-Physical Systems

Abstract

Abstract-The main topics of the Cyber-Physical Systems (CPSs) cover the specification, modeling, control, design, verification and testing. The CPSs implementation consists of reactive programs conceived using models that are capable to sustain the mentioned activities. Component diagrams (introduced by Unified Modeling Language) are used here for the architecture design, with the goal to split the CPS complexity into smaller entities that are easier to tackle. All the components are modeled by Fuzzy Logic Enhanced Time Petri Nets (FLETPNs) that can simultaneously describe the discrete event and the time discrete features. This unique and compact approach facilitates the control synthesis, the software design, the verification and the testing.An example of application to the control of a system composed of a wind turbine generator, a photo-voltaic generator and loads is used to show the model utilization and its benefits. I. APPROACHES OF THE CYBER-PHYSICAL SYSTEMSCPSs integrate the dynamics of the physical processes with those of the software and communication. There are some surveys that present the main characteristics, the main domains where they are applied and the main topics of the CPSs [10], [11], [12]. The main topics of the CPSs cover the specification, the modeling, the control, the design, the verification and the testing. The CPSs implementation consists of reactive programs that are based on models that are capable to support the mentioned activities.The main goal of the current research is to conceive a control system that concurrently reacts to discrete events and continuous modifications of plant state. The target is a set of interacting dynamic models capable to approach the following specification:• the reaction to synchronous and asynchronous (plant) events that are signaled by continuous variables (instead of single level events) • the continuous time reaction to modification of some (plant output) variables • the reaction control signals that belong to continuous domains (the discrete domains, as the binary set, should be particular cases) Some reactions require the execution of activities involving non-ignorable durations and could have real-time constraints that have to be fulfilled. This requirement leads to the conclusion that the target model has to be capable to describe concurrent behavior.A relevant issue is to conceive a model that is capable to describe the controller behavior and its structure. A practical goal is to make possible the verification that the implemented model fulfills the specified requirements.The implementation of controllers on digital computers supposes that the information of continuous variables can be represented with a limited and tolerated accuracy (due to the limited length of the number representation) and the calculus can add other losses of the precision. On the other hand, the continuous time reactions are not possible to be implemented on digital computers. For this reason, instead of continuous time models, the discrete time models are used. The l...