Cyber-Physical Systems

A cyber-physical system (CPS) is an integration of computation with physical processes. Embedded computers and networks monitor and control the physical processes, usually with feedback loops where physical processes affect computations and vice versa. As an intellectual challenge, CPS is about the intersection, not the union, of the physical and the cyber. It is not sufficient to separately understand the physical components and the computational components. We must instead understand their interaction. The design of such systems, therefore, requires understanding the joint dynamics of computers, software, networks, and physical processes. It is this study of joint dynamics that sets this discipline apart.

About the Term "Cyber-Physical Systems"

The term "cyber-physical systems" emerged around 2006, when it was coined by Helen Gill at the National Science Foundation in the United States. While we are all familiar with the term "cyberspace," and may be tempted to associate it with CPS, the roots of the term CPS are older and deeper. It would be more accurate to view the terms "cyberspace" and "cyber-physical systems" as stemming from the same root, "cybernetics," rather than viewing one as being derived from the other. The term "cybernetics" was coined by Norbert Wiener (Wiener, 1948), an American mathematician who had a huge impact on the development of control systems theory.

During World War II, Wiener pioneered technology for the automatic aiming and firing of anti-aircraft guns. Although the mechanisms he used did not involve digital computers, the principles involved are similar to those used today in a huge variety of computerbased feedback control systems. Wiener derived the term from the Greek kybernetes, meaning helmsman, governor, pilot, or rudder. The metaphor is apt for control systems.

Wiener described his vision of cybernetics as the conjunction of control and communication. His notion of control was deeply rooted in closed-loop feedback, where the control logic is driven by measurements of physical processes, and in turn drives the physical processes. Even though Wiener did not use digital computers, the control logic is effectively a computation, and therefore cybernetics is the conjunction of physical processes, computation, and communication.

Wiener could not have anticipated the powerful effects of digital computation and networks. The fact that the term "cyber-physical systems" may be ambiguously interpreted as the conjunction of cyberspace with physical processes, therefore, helps to underscore the enormous impact that CPS will have. CPS leverages a phenomenal information technology that far outstrips even the wildest dreams of Wiener's era.

Source: Lee and Seshia, Introduction to Embedded Systems - A Cyber-Physical Systems Approach,, 2011.