Cyber-physical systems (CPS) are the combination of physical, networking, and computational processes. With feedback loops where physical processes influence calculations and vice versa, embedded systems and networks monitor and manage the physical processes. With the use of abstractions and modelling, design, and analytic approaches, CPS blends the dynamics of physical processes with those of software and networking. Standards, protocols, and test techniques that facilitate the discovery, interoperability, and composition of components required to create these CPS will foster innovation while also improving economic viability and enable systems to become more efficient and resource efficient. This chapter presents the basic mechanisms of the CPS such as workflow, characteristics, simple structure, and major applications of CPS. Also, the chapter analyzes the design considerations of CPS based on the security, trust management, energy-efficiency, reliability, service composition, and resource provisioning aspects.
TopOverview Of Cyber Physical Systems
Cyber-physical systems (CPS) is a term first introduced by Helen Gill in 2006 at National Science Foundation (NSF). It stems from the word Cybernetics which was introduced by Norbert Wiener. CPS acts as a bridge between cyber world and physical world. The principal goal of CPS is to monitor the physical process and according to the need they will be actuated to change its behaviour (Edward Lee., 2015). There is a tight integration between cyber and physical world. This tight integration differentiates it from desktop computing, traditional embedded systems, real-time systems and wireless sensor net- work. Many researchers have proposed different definitions of CPS. The definition of CPS is as follows:
“Cyber Physical Systems is defined as the interaction between tightly coupled physical processes and cyber processes in a controlled and coordinated manner to extract deeper knowledge, which enables more accurate actions and tasks and thus provide a set of proactive as well as intelligence-rich services which forms the basis for building smart applications.”
It can also be described as the integration of computing with physical protocols, with both physical and cyber components equally defining the behaviour (Volkan Gunes et al., 2014). A mechanism called a cyber-physical system is one that is meant to be anticipated and managed by computer-based algorithms. The entire CPS system is tangibly connected to the Internet; as a result, the word “cyber” is included in it. Software and physical components work side by side via various temporal and spatial scales in a CPS. A CPS is designed to draw attention to crucial problems like contiguous engineering ethnicities in the physical and cyberspace.
Figure 1. Definition of cyber-physical systems
TopWorkflow Of Cyber-Physical Systems
CPS consistently integrates sensor networks with embedded systems to monitor and regulate the physical environment, including feedback loops that allow this external stimulus to self-activate communication, control, or computing (Eric Ke Wang et al., 2010). An overall workflow of CPS is written off as four key phases and illustrated in Figure 2.
Figure 2. Workflow of cyber physical system
Monitoring
It's the preliminary stage of the CPS process, when historical data is analysed to monitor the physical system from beginning to end. The CPS will then utilise this information to ensure that every method involved is secure for use in the future. Any flaw that CPS notices in the physical system must be fundamentally fixed.
Networking
Data collection is to be done at this stage. Numerous RF modules, sensors, and/or wireless devices may be implicated in a cyber-physical system. Real-time data are produced by sensors and/or RF modules. Later, all of the generated data must be gathered together for further processing. Numerous applications are also interacting and communicating across the network in the meantime.
Computing
During this phase, the obtained data is synopsized and examined during the overseeing review and testing of the physical system's circumstances. Actions must be carried out while running through the physical system's circumstances. For example, utilization of a data prediction model to anticipate valve controller in storage tank operations based on the algorithm intended in accordance with historical data.
Actuation
Actions planned in the computing stage will be carried out in this phase. Actuation will actuate multiple actions such as physical process control, cyber behaviour correction, and so on. As an example, action is to regulate and govern the valve in the storage tank based on historical data.
Characteristics Of Cyber Physical Systems
A general workflow of CPS can be decomposed into four main components which are sensing, communication, computation and control. The inherent characteristics of CPS are as follows: