An enormous range of device manufacturers, service providers, and software makers stand to build entirely new businesses addressing the IoE opportunity. However, this opportunity brings more security and privacy concerns for the consumers and businesses that support various applications.
Networked embedded systems have emerged under various names such as Internet/Web of Things/Objects, Internet of Everything, smart objects, Cooperating Objects, Industry 4.0, the Industrial Internet, cyber–physical systems, M2M, the Internet of Everything, the Smarter Planet, TSensors (Trillion Sensors), or the Fog (like the cloud, but closer to the ground). The vision is of a technology that deeply connects our physical world with our information world, although one may argue on the differences and their focus. In this research paper [Karnouskos 2011], the author argues that does not really differentiate when it refers to them as an amalgamation of computational and physical properties.
However, the trend is toward integration and interaction of the physical world with the information world. Recently, the community has come to understand that the principal challenges in embedded systems stem from their interaction with physical processes, and not from their limited resources. Since CPS emerge as a distinct category, the following section is an overview of this concept.
2.1.3 Cyber–Physical Systems
The term cyber–physical systems was coined by Helen Gill at the National Science Foundation in the United States in 2006 [CPS 2006]. CPS comprise interacting digital, analog, physical, and human components engineered for function through integrated physics and logic [NIST CPS].
A CPS is an integration of computation with physical processes whose behavior is defined by both cyber and physical parts of the system [Lee 2015a]. The authors argue that it is not sufficient only to separately understand the physical components and the computational components, but we must also understand their interaction. CPS is about the intersection, not the union, of the physical and the cyber [Lee 2010], [Lee 2015a], [Lee 2015b]. The embedded computers and networks monitor and control the physical processes, usually with feedback loops where physical processes affect computations and vice versa. This work [Lee 2015a] provides methodology and techniques for designing CPS. Figure 2.7 is a simple representation of a CPS with the components, computation, communication, and control that interact continuously.
Figure 2.7 Simple cyber‐physical representation.
CPS are heterogeneous blends by nature. They combine computation, communication, and physical dynamics [Lee 2015a]. The authors envision that several CPS applications may be based on a structure to include three main parts:
First, the physical plant is the physical part of a CPS, not realized with computers or digital networks; it can include mechanical parts, biological or chemical processes and human operators.
Second, there are one or more computational platforms, which consist of sensors, actuators, one or more computers, and (possibly) one or more operating systems (OS).
Third, there is a network fabric, which provides the mechanisms for the computers to communicate; the platforms and the network fabric form the cyber part of the CPS.
A more detailed and current definition of CPS is provided by NIST [NIST SP1500‐201]:
Cyber–physical systems integrate computation, communication, sensing, and actuation with physical systems to fulfill time‐sensitive functions with varying degrees of interaction with the environment, including human interaction.
A CPS conceptual model is shown in Figure 2.8. This CPS representation highlights the potential interactions of devices and systems in a system of systems (SoS) (e.g. a CPS infrastructure).
Figure 2.8 NIST CPS conceptual model.
Source: [NIST SP1500‐201]. Public Domain.
As shown in Figure 2.8, CPS may be as simple as an individual device (a device that has an element of computation and interacts with the physical world through sensing and actuation), or a CPS can consist of one or more cyber–physical devices that form a system or can be an SoS, consisting of multiple systems that consist of multiple devices. This pattern is recursive and depends on one's perspective (e.g. a device from one perspective may be a system from another perspective). Ultimately, a CPS must contain the decision flow together with at least one of the flows for information or action. The information flow represents digitally the measurement of the physical state of the physical world, while the action flow impacts the physical state of the physical world. This allows for collaborations from small and medium scale up to city/nation/world scale.
The scope of CPS is very broad by nature; there are large number and variety of domains, services, applications, and devices. Also, CPS controls have a variety of levels of complexity ranging from automatic to autonomic. CPS go beyond conventional product, system, and application design traditionally conducted in the absence of significant or pervasive interconnectedness. There are many differences that characterize CPS from traditional systems. Examples of characteristics are listed in Table 2.1.
Table 2.1 CPS characteristics.
Source: Adapted from [NIST SP1500‐201].
| Characteristic | Description | Remarks |
| Cyber and physical | Combination of cyber and physical components | |
| Connectedness | Generally involves sensing, computation and actuation | Involves combination of IT and OT with associated timing constraints |
| System of systems (SoS) | May bridge multiple purposes and time and data domains | Different time domains may reference different time scales or have different granularities or accuracies Time scale: a system of unambiguous ordering of events |
| Emergent behaviors | Open nature of CPS composition | Understanding a behavior that cannot be reduced to a single CPS subsystem, but comes about through the interaction of possibly many CPS subsystems |
| Methodology | A methodology needed to ensuring interoperability, managing evolution, and dealing with emergent effects | Example: NIST 1500‐201 framework |
| Repurposed |
Other purpose use beyond applications that were
|