A process control system is an
|“||integrated hardware and software system specifically engineered to monitor, evaluate, and regulate complex, large-scale processes.||”|
Such a system can be characterized as one or more of the following forms:
- Discrete: Found in many manufacturing, motion and packaging applications. Robotic assembly, such as that found in automotive production, can be characterized as discrete process control. Most discrete manufacturing involves the production of discrete pieces of product, such as metal stamping.
- Batch: Some applications require that specific quantities of raw materials be combined in specific ways for particular durations to produce an intermediate or end result. One example is the production of adhesives and glues, which normally require the mixing of raw materials in a heated vessel for a period of time to form a quantity of end product. Other important examples are the production of food, beverages and medicine. Batch processes are generally used to produce a relatively low to intermediate quantity of product per year (a few pounds to millions of pounds).
- Continuous: Often, a physical system is represented through variables that are smooth and uninterrupted in time. The control of the water temperature in a heating jacket, for example, is an example of continuous process control. Some important continuous processes are the production of fuels, chemicals and plastics. Continuous processes in manufacturing are used to produce very large quantities of product per year (millions to billions of pounds).
Examples include the Supervisory Control and Data Acquisition (SCADA) systems that manage the electric power grid and the PCSs that control the timing and volume of processes in the chemical industry. PCS technologies also control the distributed sensor and actuator elements of pipeline systems for gas, oil, and water distribution. They manage supply chains and associated transportation systems, and they increasingly control building security, fire protection, environmental systems, lighting, and communications.
System security Edit
Because attacks interrupting or damaging key PCSs could have rippling impacts across the economy, these systems may increasingly be viewed by adversaries as attractive targets that can be exploited to weaken or incapacitate U.S. industry and infrastructure. Critical infrastructure sectors debate whether or not an exclusively electronic attack on control technologies could indeed have significant impact, given the industries' backup power systems and investment in "fail safe" or otherwise resilient designs for physical systems. But trends in the application of IT in these sectors point to increasing rather than decreasing levels of vulnerability and exposure in the infrastructure.
In the past, many PCS technologies used proprietary designs. Today, in the interest of reducing cost and improving maintainability, these systems mainly rely on standardized equipment and technologies, including general-purpose computers, mainstream operating systems, and standard Internet protocols, which are more vulnerable to attack. Many organizations view increasing use of the Internet as well as wireless and Web-based control systems as not only cost-effective but inevitable developments. Furthermore, cost-reduction measures are resulting in growing linking of networks that support control systems with internal and external corporate networks that support ordinary business operations, further increasing the exposure of control systems to external attacks.
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