By cable, radio and light

Thanks to Industry 4.0, increasing numbers of objects are interchanging increasingly large volumes of data. In order to handle this deluge of data, robust, high-performance communications technologies are essential.

With machines and sensors producing an ever-increasing amount of data, companies are facing an unprecedented challenge. They need to act in real time with the incoming data and work within the limits of available bandwidth,” comments Kip Compton, Vice President and General Manager of the IoT Systems and Software Group at Cisco. At the same time, demands in terms of minimising runtime and of reliability are also rising. These are all reasons why the Industrial Ethernet standard is being used increasingly widely at field level – that is to say, in the sensors and actuators used in production. It is based on the long-established Ethernet standard in the PC and office sector, and as such uses the base technology for the world’s biggest network: the World Wide Web, or Internet for short. “In many respects, the value proposition for industrial Ethernet parallels those for emerging concepts such as Industry 4.0 and the Industrial Internet of Things, adding further substance to its longevity prospects. Industrial Ethernet aligns well with both of these concepts by providing flexibility and ease of integration to support Industry 4.0 and connectivity for the Industrial Internet of Things,” according to Vice President Chantal Polsonetti, the principal author of ARC’s “Industrial Ethernet Devices Global Market Research Study”. In fact, according to a study by Swedish company HMS Industrial Networks, the number of Industrial Ethernet network nodes is growing at around 17 percent a year.

Into the gigabit age

But unfortunately, not all Ethernet is the same. There are over 20 different application protocols for Industrial Ethernet, such as Profinet, EtherNet/IP, EtherCAT, FLNet, and many others. Those systems differ, among other ways, in their application areas, their technical properties and their real-time capabilities, but above all they are mutually incompatible. So open communications need interfaces with network processors which support all protocols as far as possible.
Industry experts expect that so-called Gigabit Ethernet will become the general standard for handling Big Data in future. It can manage transfer rates of 1 gigabit per second – though researchers are already working on Ethernet systems capable of running at up to 400 gigabits per second (by comparison: current commonly used DSL connections have maximum transfer rates of 100 to 200 megabits per second – 2,000 times slower).

Flexibility based on wireless ­communications

A key factor in the Smart Factory, however, is wireless communications, as Dr Barbara Staehle, group leader Wireless Automation Networks at the Fraunhofer Institute for Embedded Systems and Communication Technologies ESK, highlights: “For the Industry 4.0 idea to work with flexible, adaptively self-configuring production plants, reliable wireless technologies are essential. This is where cable-bound solutions come up against their limits, particularly when mobile machine components or production items have to be localised within the process and need to communicate in order to interact.” For long-range transmission within a factory, WLAN based on IEEE (Institute of Electrical and Electronics Engineers) standard 802.11 will predominate. The new specifications 802.11ac and 802.11ad permit data transfer rates of one gigabit per second and more.

Robustness in demand

“The use of wireless technologies in industry offers lots of benefits. Wireless devices not only reduce installation costs compared to wired components, they also give mobility to applications with difficult cabling. Users should nevertheless be sure to verify the reliability and availability of wireless devices when using them in mission-critical applications,” says Paul Hsu, Business Development Manager Industrial Wireless with Moxa Europe. Because there are numerous obstacles to stable wireless connections in warehouses and factory buildings. Ceiling or wall claddings, machinery, shelving or items in storage can all block wireless signals. “Industrial wireless devices need robust design, including advanced EMC protection against electrical interference as well as uninterrupted wireless roaming for extended network availability,” Hsu adds. This is achieved using so-called Seamless Roaming. In this, the “client”, such as a forklift truck, is connected to two access points simultaneously. If it loses contact with one of them, it automatically searches for the nearest and connects to it. This means seamless data traffic is continuously maintained even when such “clients” are moving around.

Chip as digital memory

Not only WLAN technology will be found in Industry 4.0, however. For short-range communications, systems such as NFC, Zigbee, Bluetooth or RFID may also be used. RFID (Radio Frequency Identification) in particular offers interesting possibilities for Industry 4.0. Objects fitted with an RFID chip can not only transmit information, such as their identity, they can also receive and store data, so creating a digital memory. This means that a workpiece fitted with an RFID chip can provide information at any time indicating which process steps it has already passed through and what the next step will be. The demands placed on industrial wireless systems are very high however, as Dr Staehle points out: “They must above all be stable and robust, and have real-time capability, so as to guarantee cable-like quality. So the key factors are choosing the right standards, protocols and algorithms for the specific application scenario, as well as thorough planning and careful monitoring of wireless data transfer.”

Communication by light

As an alternative to data transfer over radio waves, research is currently also being conducted into optical systems. Back in late 2013, Dr Frank Deicke, group leader for optical sensors and data transfer at the Fraunhofer Institute for Photonic Microsystems IPMS, presented an optical wireless communications module capable of transferring data at speeds of up to 5 gigabits per second. He has since succeeded in doubling that speed. Deicke and his team developed a transceiver for optical wireless communication which is the size of a sugar cube and can transmit data at speeds of up to 10 gigabits per second via infrared. Compared to familiar wireless technologies such as Bluetooth or WLAN, this communications module offers much higher data throughput, extremely low bit error rates and substantial energy savings. It does require line of sight between the transmitter and receiver, however.

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