Ethernet has proven itself to be an economical, flexible medium suitable for universal use. The widest range of utilities (e-mail, Internet, data transfer, and audio and video communications), device types (PCs, printers, digital cameras, servers, and telephones) and transport media (copper or fibre-optic cable, radio or laser) can all be used as required.
Ethernet is understood to represent all properties and utilities in their entirety. On closer technical examination, however, it forms only basic communication, comprising the communications medium (the Physical Layer on OSI Layer 1) and the Data Link Layer (OSI Layer 2). Other utilities such as TCP, SMTP, and FTP use Ethernet and build upon it.
“For plant design … SafetyNET p offers a universal platform on which all utilities can communicate, from sensor to control level.”
Ethernet for industrial communications
Unlike office communications, industrial and process automation are based on a multitude of different fieldbus systems (such as ASI, CAN, DeviceNet, Interbus and PROFIBUS). Particular versions with additional performance features have established themselves in parallel for specific applications such as drive or safety technology. Generally, these fieldbuses are not compatible with one another.
If Ethernet is considered a network in which all devices and utilities can communicate with each other via the same medium, the idea of Industrial Ethernet seems completely natural. Because of technical restrictions in its current standard form, Ethernet requires some fundamental additions to make it suitable for industrial purposes. These are necessary to enable it for use both in new industrial applications as well as existing applications. The office world’s demands for robustness and reliability do not come close to satisfying the rugged environmental conditions of a body shell line at a car production plant or power station.
Industrial Ethernet is based on the actual performance features, cabling structures, and available devices of office communication. Standard features of fieldbus cabling are then added. These include the ability to form linear structures without using switches or hubs, or the definition of robust industrial connection technology in higher protection types (IP65/67). It is intended that components employed in office communication such as switches, routers, printers, and laptops are still usable.
For universal usability, real-time communication support is absolutely essential. Deterministically guaranteed scan times of 100 µs and less are required to implement highly dynamic drive applications. Directly integrating a security protocol for machinery safety purposes is equally essential. This security protocol is necessary for communicating information used to protect humans, machines, and the environment from hazards.
Add to this the demand for dynamic networks in which subscribers can log in and out or that allow subscribers to change to other power supplies. This was not possible using conventional fieldbus systems.
For the purposes of modular systems, stand-alone units, setup mode, or diagnostics, users also want data traffic from subscriber to subscriber without a centralized controller.
Above all these requirements, the ultimate preference is for an integrated, economical, and flexible solution that can be applied universally for office and industrial applications. To meet this requirement, it is imperative that the corresponding drivers are available and an open standard enabled so that each manufacturer can apply this technology. SafetyNET p takes these requirements into consideration.
Based on these prerequisites, Germany’s Pilz GmbH & Co. KG specified and developed SafetyNET p as an open network with optimum frame data. To ensure this system is open and widely propagated, Safety Network International e. V., a fast-growing organization of SafetyNET users, is supporting integration. The organization offers its affiliated member companies product-neutral integration utilities and development support.
(cont. part two)
