5 - PLC-Automata
Published online by Cambridge University Press: 06 January 2010
Summary
In industrial automation the aim is to control and optimise production processes and to provide high-quality and reliable products and services by minimising material, cost, and energy waste. Automation systems rely on smart sensors, actuators, and other industrial equipment like robotic and mechatronic components. Open and standardised communication networks are employed for the communication as well as configuration and control of the various automation components. The standard architecture consists of PLCs (Programmable Logic Controllers) or DCS (Distributed Control Systems), fieldbus systems, and PCs serving as man/machine interfaces as well as intelligent sensors and actuators (e.g. frequency converters). The fieldbus systems gather the signals from the process level or the sensors and actuators with fieldbus interfaces, and are directly connected to distributed or centralised control devices, such as PLCs.
The standard IEC 61131-3 of the International Electrotechnical Commission provides a range of programming notations suitable for implementation on PLCs. It comprises basic notations close to those in electrical engineering like contact plans, instruction lists, and function plans as well as graphical and textual programming notations called sequential function charts and structured text. Currently, the development of software in automation technology proceeds step by step along the life cycle using the notations of this standard and different tools provided by different PLC vendors.
A problem is that different PLC vendors use their own variants of the standard with different syntax, semantics, and tool sets. Also, the approaches based on the standard are not well suited for the development of distributed applications and applications with hard real-time requirements.
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- Real-Time SystemsFormal Specification and Automatic Verification, pp. 189 - 240Publisher: Cambridge University PressPrint publication year: 2008