The field level - the basis of industrial networking

Part 1 of our field series:

Cloud computing, digitization, industry 4.0 - These terms are on everyone's lips. Machine networking, data evaluation and intelligent control systems are designed to optimize production processes and reduce failure rates. But how can production data acquisition be successful in industry? Where does the data come from and how can it be transferred? In our professional article series about the field we clarify these and other questions.

 

The field level - the basis of industrial networking

Where at home a few network cables and a router or switch are sufficient to connect computers, media players and Internet radio, networking is much more complex on an industrial scale - and not only because different proprietary and industrial standards and protocols exist.

When machines with control stations and both communicate directly with management, then we are in the middle of the so-called "automation pyramid". This pyramid classifies systems and techniques into different levels of industrial manufacturing. Their basis is the so-called field level and in it the field buses.

 

Time before fieldbus

In early industrial times, measured values were still obtained entirely analogously by looking at the displays of the machines. For this reason, the company began early on to transmit the measured values to a control station via simple two-wire cabling. However, the measured values could not be completely trusted. Because interfering signals could distort the data flow. In addition, the effort was immense: For each machine, quite a few cables had to be laid. At the end of the 80s it became modern and clear: The first so-called field bus systems came up and with them digital industrial data transmission technology.

 

1 and 0: the digital fieldbus

The fieldbus today uses a wide variety of wiring - or as a radio standard can even do without cables. The data from countless sensors and actuators are now transmitted via the digital fieldbus. This was made possible by the equipment with microelectronics. Thus the digital connection with control and regulation technology (programmable logic controller, SKADA, etc.) takes place. Among other things, the sensors measure temperature, pressure, voltage or current and transmit the values serially to a central unit via the fieldbus. From there, actuators such as motors can be controlled.

This industrial network of fieldbus systems is based on a large number of protocols and standards. This diversity was due to the fact that almost every major customer of such systems had special requirements that the suppliers had to meet. In addition, the manufacturers established their own systems with self-imposed standards. The companies use these in a targeted manner to create a fixed circle of users for themselves.

"CAN", "Modbus", "PROFIBUS", "KNX", "INTERBUS" and "DALI" belong to the well-known fieldbuses today - to name only a small selection of more than 50 available systems. What all buses have in common is that they have been developed for optimum latency times, high interference immunity and data security during transmission. Internationally standardized fieldbuses can be found in IEC standard 61158.

Different layers: The automation pyramid

The fieldbus belongs to the field level, the lowest level of the automation pyramid. The control level, the process or management level, the plant management level and at the top of the pyramid the company level build on this.

The control level bundles and processes the data. Control commands are derived from the information obtained and sent to the actuators via the field level. In the next stage, the process and control level, the information and commands for status overviews are visualized. This enables plant operators to monitor industrial production.

The plant control level is then the higher level, which is primarily responsible for networking the administration, but also acts with data from the lower levels. At the enterprise level, planning is carried out using Enterprise Resource Planning (ERP) systems. It is based on data from the previous levels. From one level of this pyramid to another, the most diverse techniques and standards pose an ever-increasing challenge.

All alone and each for himself

The fieldbuses are mostly incompatible with each other. This means that they cannot be operated together, but require a "simultaneous translator". It is not uncommon for a wide variety of fieldbuses to be used in parallel in one production process. Gateways that harmonize the signals serve today as "simultaneous translators". Edge controllers such as the sysWORXX CTR-700, for example, record the signals of the various buses and convert them into common exchange formats such as OPC UA or MQTT almost in real time. On the basis of these data formats, the higher levels can then evaluate and process the data and make decisions.

 

Future: IP

With the advancing development in the field of microelectronics, microprocessors have become cheaper and more powerful. This goes hand in hand with the fact that an Ethernet stack in the microprocessor or chipset is almost a matter of course today. This also opens up the possibility of networking on the field level based on the Internet Protocol (IP) and thus networking via Ethernet.

Thanks to a layer model that consistently separates data transmission (transport and switching) from network access (bit transmission and security), industrial networking opened up entirely new paths with regard to the transmission medium. In addition to copper cable-based transmission, transmission via radio (Wi-Fi), for example, became possible. At the same time, the IP guarantees high data permeability between the layers of the automation pyramid without the need to convert the data.

Currently, the established Internet protocol version 4 (IPv4) with its 32-bit addresses is mostly used for industrial networking at field level. In the foreseeable future, the change to the successor protocol IPv6 is also pending here.

 

For all: a lots of IP addresses

In IPv4 only a limited number of possible IPv4 addresses - maximum 4,294,967,296 addresses - can be assigned globally. The potential global address pool has already been exhausted for a long time. For field networking, however, this still plays a subordinate role, since networking in the industrial segment is carried out locally. For this purpose, local networks with subnets and address translation are created. As a rule, access from global networks should not be possible. Where it should be possible, special routing procedures and redirects are used.

The limited address space will belong to the history with further development of Internet Protocol Version 6 (IPv6). Thanks to 128-bit long addresses, it is possible to assign a unique address to almost every electronic device in the world. However, IPv6 is not unproblematic either, as the necessary IP stack requires comparatively high computing power and bandwidth during transmission. This problem was solved by streamlined and optimized implementations.

Field level and industry 4.0

With the introduction of the Internet Protocol, the field level can be connected to the Internet of Things (IoT). This opens up completely new possibilities for the interaction of sensors and actuators in industrial production at this lowest level of the automation pyramid. The scenarios are summarized in the concept of industry 4.0, also called Industrial Internet.

Modern gateways such as the sysWORXX CTR-700 edge controller pave the way for industry 4.0. They ensure that the worlds of analog, digital, non-IP-based and IP-based transmission are reliably connected.

SYS TEC electronic: Reliable service provider - not only - on the field level

Regardless of the type of field networking, companies are often faced with the challenge of collecting data at the field level and processing and evaluating it at the other levels of the automation pyramid. This is where SYS TEC specialists can help. You know exactly how the data is generated at field level, forwarded, and preprocessed for processing. It does not matter whether sensors and actuators are to be connected via processes such as CANopen, networked via protocols such as MQTT or the data passed on to a cloud. SYS TEC electronic supports its customers with comprehensive and interdisciplinary know-how in the areas of interfaces, protocols and buses.

 

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