“Automation has several levels, with the bottom two—control and field—being the most relevant for manufacturers implementing the IIoT,” says Klaus Leuchs, strategic product manager of Industrial Ethernet—passive at Weidmüller Interface GmbH & Co. KG. “The problem is, companies have different systems at each level, and this leads to discontinuity of communication between devices and higher infrastructure costs.”

Leuchs points out that Industrial Ethernet has been the established communication means for control-level devices, including PLCs, for many years. At the field level, however, where sensors, actuators and hardware dominate, fieldbus networks with an interface card are still required. A gateway is required to connect both levels when using Ethernet. To obtain seamless communication through all levels of automation, Ethernet at the field level is needed.

“Feedback from manufacturers at this year’s Hannover Messe Fair was positive when we discussed the need to implement single-pair Ethernet (SPE) in their field-level devices,” notes Leuchs, whose company makes SPE. “The interest is from companies worldwide, and they are very receptive to doing this. We are hopeful to see a big increase sometime during 2023 or in 2024.”

Regardless of if or when this happens, manufacturers creating a factory of the future will still need to implement assembly equipment that is compatible with the latest communication standards and protocols to ensure optimum performance. Among the most important to understand are Industrial Ethernet, Profinet, IO-Link, CC-Link and OPC UA.

Industrial Ethernet

Rather than being a simple standard, Industrial Ethernet is an umbrella term referring to a set of Ethernet protocols based on standard Ethernet hardware (physical and data link layers), Internet protocols (networking and transport layers) and a proprietary application layer. Common Ethernet protocols include EtherCAT, EtherNet/IP, Profinet and SERCOS III.

“The standard Ethernet used in an office isn’t suitable for the factory floor, because there we need much faster response times, as well as easy installation of cables and connectors” explains Leuchs. “Through the Ethernet protocols, manufacturers can create a deterministic environment, where preset amounts of data are guaranteed to be sent and received at a specific time and place for a specific operation.”

The protocols achieve determinism through the use of an architecture known as Open Software/Modified Ethernet. This architecture is based on standard Ethernet, and additional complimentary, hardware, with each protocol utilizing different hardware and transport mechanisms.

Another way that Industrial Ethernet differs from standard Ethernet is the use of robust cables and connectors to withstand harsh environmental conditions. This equipment may also require specific shielding, grounding and filtering to handle electromagnetic noise in a factory setting.

The increasing importance of the IIoT and Industry 4.0 in recent years requires an Ethernet solution at the field level, says Leuchs. The SPE System Alliance has been working on this, regarding both system and component standardization, since forming in November 2019, with a particular emphasis on connectors.

“The trend towards SPE cannot be denied; the only point of discussion is which connector standard will be used, and which connector best meets that standard,” opines Leuchs. “Our point of view is that the IEC 63171-2/-5 standard offers the broadest product portfolio and is supported by multiple connector manufacturers. There are various candidates [to be the approved connector], but the advantage of our SPE patch cable, which meets IEC 63171-2, is that it’s the most compact of all the SPE connector variants.”

Introduced in the 1990s, DeviceNet enjoyed great popularity for many years because it is a device-level network with an open protocol that supports multiple vendors. However, the advent of better switching technologies, along with the increased robustness of the Ethernet/IP, in the last decade has led to the practical demise of DeviceNet. Many manufactures are converting these networks to Ethernet/IP to ease maintenance and increase control.

Profinet

“Although more than 66 million Profibus (process fieldbus) network devices have been installed in factories worldwide, the Profinet (process field net) protocol offers manufacturers faster and more flexible communication between equipment on the assembly line,” says Michael Bowne, executive director of PI North America. “Companies know this, which is why sales of Profinet-compatible devices have exceeded those of Profibus-compatible ones every year since 2016.”

Profibus & Profinet International (PI) developed Profinet in 2003, nearly 25 years after BMBF (the German department of education and research) created and began promoting the Profibus standard. According to Bowne, data is easily exchanged between Profinet-compatible controllers and devices. Controllers can be PLCs, distributed control systems or programmable automation controllers; devices include I/O blocks, vision systems, RFID readers, drives, process instruments, proxies or even other controllers.

“Profinet is important because it gives end-users many more capabilities on the factory floor,” says Bowne. “A big one is performing diagnostics, thanks to the protocol’s advanced mechanisms. Alarms, HMI screens, special-purpose tools, and standard IT protocols all help manufacturers perform troubleshooting to prevent downtime.”

Synchronizing motion control and achieving functional safety of people and assets are two more benefits. Versatility is another, as the protocol operates over standard copper or fiber optic cable, as well as wirelessly via Wi-Fi and Bluetooth.

Being Ethernet based, Profinet runs at 100 megabits per second, all the way up to Gigabit Ethernet and higher. Utilizing Ethernet-based communication enables the protocol to offer higher bandwidth and a larger message size than Profibus.

PI conducts a yearly audit to count new Profibus and Profinet devices sold. In 2016, Profinet sales exceeded Profibus for the first time: 3.6 million devices compared to 2.4 million. Five years later, according to Bowne, the difference was even greater: 8.5 million Profinet devices to 1.5 million Profibus.

“In many plants, manufacturers must establish communication between the fieldbus and Ethernet networks,” notes Bowne. “Profibus-to-Profinet proxies ensure that this communication is seamless by translating Profibus device data to the Profinet protocol.”

IO-Link

As manufacturers look for ways to maximize productivity and eliminate waste, sensors are taking on a new role on the assembly line. For decades, sensors were only used to provide detection or measurement data so the PLC could process it and run the machine.

Today, IO-Link-compatible sensors measure environmental conditions like temperature, humidity, ambient pressure, vibration, inclination, operating hours and signal strength. They also let operators set alarm thresholds, so a PLC can use the resulting condition monitoring data to keep machines running smoothly.

“Data is the ‘new gold’ that enables manufacturers to squeeze out every possible bit of additional equipment efficiency,” says Bowne. “IO-Link provides more helpful data by taking simple sensors and turning them into smart ones. An IO-Link proximity sensor, for example, no longer simply tells an operator that an item is present or not. It also provides some data if an item of a certain size or color is present on the assembly line.”

Manufacturers have benefitted from IO-Link-compatible sensors and actuators since 2006, when the interface was developed through a cooperative forum between the IO-Link Consortium and PI. An open standard (IEC61131-9), IO-Link is fieldbus independent and can be integrated into all fieldbus systems worldwide. These features account for its growing popularity among manufacturers and machine builders of all sizes.

They especially like that the standard allows for bidirectional and transparent data exchange between sensors, actuators and other devices that support IO-Link and are connected to a master. Enabling point-to-point communication based on widely used three-wire cable connections is also quite appealing and cost effective, according to Bowne.

Other advantages include standardized and reduced wiring, and real-time remote configuration and monitoring. The latter allows operators to address issues as they arise on the assembly line, so problems can be resolved before they escalate and cause the line to shut down.

Installation and commissioning time are greatly improved as well since the communication medium is the same for both digital and analog sensors. Equally important, the IO-Link interface helps engineers determine if a device is behaving the way it should and identify any malfunctions or avoid them by replacing it at the right time.

CC-Link

Similar to Industrial Ethernet, CC-Link is not a single entity. Rather, it’s a group of open-technology automation networks that enable devices from numerous manufacturers to communicate.

The original CC-Link fieldbus network, based on serial communication, was released in 2000. CC-Link IE (Industrial Ethernet) appeared in 2008 and is the first open network standard based on 1-gigabit-per-second Ethernet. Both CC-Link and CC-Link IE have received certification from the IEC, ISO and Semiconductor Equipment and Materials International, notes Thomas Burke, global strategic advisor at the CC-Link Partner Association (CLPA).

CC-Link handles both control and production data in a high-speed deterministic manner between a wide range of devices. These include industrial PCs, PLCs, robots, servos, drives, valve manifolds, and digital and analog I/O modules. Others, according to Burke, are temperature and mass flow controllers, and bar code and RFID readers.

Key benefits of CC-Link include having a simple memory map architecture, and enabling fast throughput of large amounts of data. It also lets companies bypass nonworking network devices without disrupting network traffic.

CC-Link IE incorporates general, synchronous motion and safety control communications in a deterministic manner across multiple devices. Its twisted-pair-cable topology increases system configuration flexibility and decreases installation cost. Comprehensive diagnostic functions minimize control system disruptions, while the cable’s noise resistance ensures communications integrity.

To meet the growing trend of smart factories, CLPA developed the CC-Link IE TSN (time sensitive networking) specification in December 2018. This spec operates at layer two of the Open Systems Interconnection model, and supports Transmission Control Protocol/Internet Protocol traffic, wireless communications and the integration of third-party network protocols on a standard Ethernet infrastructure.

Burke says TSN works well with diagnostic software that uses the Simple Network Management Protocol interface to troubleshoot network devices. The spec also supports time-stamping network event errors to help evaluate their actual cause.

“TSN evolves conventional Ethernet, rather than disrupting the status quo,” says Arno Stock, business development manager at Renesas Electronics, a member of CLPA. “This means TSN is compatible with legacy standards, [while] accommodating the higher number of network devices and nodes resulting from converged architectures. Additional advantages of mixing TSN and gigabit Ethernet include shorter cycle times, increased accuracy and precision of control loops, and the ability of a network to transfer various types of data, such as video.”

OPC UA

Manufacturers of wire processing machines have developed proprietary interfaces for decades, but that era may soon be coming to an end. The reason? A group at the VDMA, the German mechanical engineering association, is working to develop a standard based on the OPC Unified Architecture (OPC UA) IEC 62541 standard for communication between automation equipment.

“Equipment in thousands of factories globally is compatible with the OPC Classic interface, which was introduced in 1996,” notes Dr. Rajive Joshi, chair of the connectivity task group at the Industry IoT Consortium, and principal solution architect at Real-Time Innovations. “Luckily, adapters are available to bridge the gap between this interface and OPC UA, which offers unified specifications and cross-platform support for robots, PLCs, presses and conveyors.”

The OPC Foundation introduced OPC UA in 2006 for several reasons, including to help manufacturers more easily interchange devices on the assembly line. Joshi says the cross-platform, open-source standard also helps facilitate communication of these devices with higher-level control and management systems. One example is sending data from sensors to the cloud.

“At its core, OPC UA targets device interoperability and access from HMIs, historians, maintenance systems, and manufacturing execution and enterprise resource planning systems,” explains Joshi. “Before OPC interfaces, manufacturers accessed devices directly through proprietary ones provided by their vendors. Unfortunately, this made companies dependent on the particular device they controlled. Worse, higher-level applications such as HMIs, had no easy way to find, connect to or control the various devices in factories.”

According to Joshi, the UA version has better syntactical data typing and semantic-information modeling capabilities. It can be implemented on devices with restricted hardware resources, such as sensors and actuators, and has a standardized gateway to the Data Distribution Service (DDS) framework for software integration and autonomy.

The OPC UA divides system software into clients and servers that may use X.509 Web standard certificates for authentication before they can communicate with each other. A client is software that connects to and controls one or more end devices. A server usually resides on, and provides a way to access, the device. Each manufacturer must provide a server to connect to a particular device.