Industrial Ethernet
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Industrial Ethernet is the name given to the use of the Ethernet Communications Interface in an industrial environment, for automation and production machine control.
Industrial Ethernet is a plant, production, process and control focused technology unlike the standard IT technology which is user focused. Industrial Ethernet (IE) is focused on the production of items that make a company profitable through some manufacturing process. Industrial Ethernet, sometimes referred to as Production Ethernet is designed to maintain control of a production process while monitoring many production items traditionally relegated to the analog world, like temperature, humidity, PH, pressure, flow, viscosity, density, weight, vibration, torque, RPM, voltage, current, radiation, full motion robotic control with feedback, satellite access and control, HD CCTV with motion, voice and intercom, two way radio access and control etc.
What Industrial Ethernet is not, is that it is not just a more robust IT version of Ethernet. Industrial Ethernet is focused on the production environment and should not be ever confused with the traditional IT environment. IE does require much more stringent standards for the products that are deployed since they are usually in factory environments, near large EMI (Electro Magnetic Interference) devices like motor, mechanical switches, high humidity, high heat or cold, high chemical content, vaporous atmosphere…etc where most of the IT devices we use were designed for office environments.
Industrial Ethernet (IE) components are usually deployed on or are in plant areas and must be designed to work and survive in these very harsh environments, where normal IT equipment would easily fail and without the stringent backup, survivability and MTBF requirements. Industrial Ethernet environments often involve unknown, hazardous environments and factors that can strongly influence the overall operation of standard Ethernet devices, as described above. In fact IE supports many factors that when loss of control occurs could cause serious disasters or the loss of life, property not to mention serious financial losses. In environments like Oil, Gas and Chemical production this is especially true. A one day offshore issue could cost $500K to $1M, so Industrial Ethernet has a much more demanding focus so component failure and problems must be resolved quickly or serious losses will occur.
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[edit] A Production Ethernet Example (Beer production)
Beer takes several days to weeks to produce and requires the monitoring and management of temperature, pressure, liquid flow, stirring, adding ingredients and much more that is handled by the Production IE network. This is commonly referred to as ICT or Industrial Control Technology that is connected through the IE.
A major beer brewer once had his Production Network (IE) go down for a period of several hours and during that time they could not be sure that the brew was being kept at the correct temperature and that the correct items had been added on time and given the correct time to mix or cure. The result was that the brew had to be dumped. Not only did this result in a lot of non productive work, the cost of a lost brew of several thousand bottles of beer but the clean up and loss of all the ingredients and the time lost. If this beer had been bottled and it was bad or spoiled it would have resulted in lawsuits and loss of market share another major cost. This is a simple but powerful example of the need for IE and that it cannot be managed as the best effort, user focused IT world of today. If this had been a chemical plant the results could have been deadly and an even more expensive cost/loss.
[edit] Advantages and Difficulties
Industrial Ethernet Protocols - Until recently, a PLC (Programmable logic controller) would communicate with a slave machine using one of several possible open or proprietary protocols, such as Modbus, Sinec H1, Profibus, CANopen, DeviceNet or FOUNDATION Fieldbus. However, there is now increasing interest in the use of Ethernet as the link-layer protocol, with one of the above protocols as the application-layer (see OSI model).
Some of the advantages are:
- Increased speed, up from 9.6 kbit/s with RS-232 to 1 Gbit/s with IEEE 802 over Cat5e/Cat6 cables or optical fiber
- Increased overall performance
- Increased distance
- Ability to use standard access points, routers, switches, hubs, cables and optical fiber, which are immensely cheaper than the equivalent serial-port devices
- Ability to have more than two nodes on link, which was possible with RS-485 but not with RS-232
- Peer-to-peer architectures may replace master-slave ones
- Better interoperability
The difficulties of using Industrial Ethernet are:
- Migrating existing systems to a new protocol (however, many adapters are available)
- Real-time uses may suffer for protocols using TCP (but some use UDP and layer 2 protocols for this reason)
- Managing a whole TCP/IP stack is more complex than just receiving serial data
- The minimum Fast Ethernet frame size including inter-frame spacing is about 80 bytes, while typical industrial communication data sizes can be closer to 1-8 bytes. This often results in a data transmission efficiency of less than 5%, negating any advantages of the higher bitrate.
- On Gigabit Ethernet the minimum frame size is 512Bytes, reducing the typical efficiency to less than 1%.
- Some of the Industrial Ethernet protocols introduce modifications to the Ethernet protocol to improve efficiency.
[edit] Main protocols
| Serial | Ethernet | Protocol | Network | Standards |
|---|---|---|---|---|
| Modbus-RTU | Modbus-TCP | TCP/IP | IEC 61158 and IEC 61784 | |
| Profibus | PROFINET IO | Isochronous real time protocol (IRT), Real time protocol (RT), Real time over UDP protocol (RTU) |
Switches, router and wireless, from 100 Mbit/s up to 1 Gbit/s |
IEC 61158 and IEC 61784 |
| DeviceNet (CIP); ControlNet (CIP) | EtherNet/IP (CIP) | TCP/IP; UDP/IP | Switches, router and wireless, from 100 Mbit/s up to 1 Gbit/s |
IEC 61158 and IEC 61784; ODVA EtherNet/IP standard |
| Foundation Fieldbus H1 | Foundation Fieldbus High Speed Ethernet (HSE) | |||
| CANopen | Ethernet Powerlink | Ethernet 100Mbit/s | by EPSG (Ethernet Powerlink Standardization Group) | |
| CANopen | EtherCAT | EtherCAT, EtherCAT/UDP | Ethernet 100Mbit/s | IEC 61158, IEC/PAS 62407, IEC 61784-3, ISO 15745-4 |
| VARAN Versatile Automation Random Access Network |
VARAN, TCP/IP, Safety | Ethernet 100Mbit/s | VARAN-BUS USER GROUP - VNO | |
| SERCOS I / II | SERCOS III | Ethernet 100Mbit/s | IEC 61491, merged into IEC 61158 | |
| FL-Net (OPCN-2) | UDP/IP | Ethernet 10Mbit/s | by JEMA (Japan Electrical Manufacturers' Association) |
(Note the highly ambiguous name given the Ethernet version of DeviceNet. The "IP" in EtherNet/IP stands for Industrial Protocol.)
[edit] References
- Arndt Lüder, Kai Lorentz (Editor), IAONA Handbook Industrial Ethernet, Industrial Automation Open Networking Alliance e.V., 150 S., Magdeburg (Germany), 2005, ISBN 3-00-016934-2, free copy at handbook(at)iaona.org.
