The Industry 4.0 network

For machine manufacturers who take advantage of this unprecedented flexibility and productivity, the transition could be a profitable one. "This means more than just boosting the level of automation, however," explains Stefan Schönegger, managing director of the Ethernet POWERLINK Standardization Group (EPSG). "It also means pursuing a more dynamic, networked approach to production."

Conventional fieldbus systems were not designed to handle the deluge of big data. Nevertheless, many machine manufacturers have attempted to get by with conventional fieldbus technology – laying out separate networks for motion control, safety and sensor data. "Not only are these parallel systems expensive and high-maintenance, they are also difficult to synchronize and prone to errors," describes Schönegger. This explains the increasing popularity of more powerful Ethernet-based networks.

"In terms of both speed and bandwidth, industrial Ethernet runs circles around conventional fieldbus systems," says Schönegger. As the fourth industrial revolution progresses, however, another problem is becoming evident. The number of network nodes found in each machine is exploding – thanks to the proliferation of intelligent sensors, auxiliary axes and the extensive safety solutions needed for human-robot collaboration. Typically, as you increase the number of network nodes, systems become slower as a result.

POWERLINK is different. By broadcasting data simultaneously to every station in the network, this technology eliminates the delays that occur when all traffic is funneled through a central location. The deviation from the clock signal, known as jitter, is less than 1 microsecond. "Even for a real-time network, this is an outstanding level of precision," says Schönegger.

Not every industrial Ethernet protocol is cut out for Industry 4.0. Some were developed with the focus solely on cycle time, ignoring the huge volumes of data that a bus system must sometimes transmit. A large share of the data in a real-time network is not time-critical, however. This includes service data for device configuration and diagnostics, process data for archiving, and safety data or video data from a surveillance camera – all of which contribute to the general trend known as big data. POWERLINK transmits this data during its asynchronous phase, a part of the cycle that has no influence on time-critical data. If necessary, protocols such as TCP/IP can be implemented in this asynchronous phase.

Typically, a machine or plant will have only a small number of truly time-critical processes, such as motion control tasks. Using a procedure known as multiplexing, it is possible to poll the time-critical nodes in every cycle, whereas general status information such as temperature values can be read much less frequently. This optimizes data volume and perfectly adapts the duration of a cycle to the application at hand. "There's one particularly impressive example of how effective this concept can be," recounts Schönegger. "On a two-dimensional film stretching machine from Brückner Maschinenbau, we synchronized 728 axes with a cycle time of 400 microseconds using POWERLINK. That's a world record."

POWERLINK is fully compliant with the IEEE 802.3 Ethernet standard. "This compatibility is a huge advantage for POWERLINK users," says Schönegger. As Ethernet technology continues to evolve, they are able to benefit from the latest advancements. With complex machines generating more and more data, it's only a matter of time until the current bandwidth of 100 Mbit/s runs up against its limitations. By maintaining full compliance with the Ethernet standard, POWERLINK ensures that, when the time comes, upgrading to Gigabit Ethernet will be quick and painless. "For Ethernet-based networks that deviate from the standard, increased bandwidth will come at the cost of extensive development and possibly even new proprietary hardware."