The benchmark for the comprehensive implementation of Industry 4.0 is directly linked to two factors: consistent digitalization and the standardized horizontal and vertical exchange of data or information. Robust communication technology with real-time capability for automation forms the basis of such implementation. And so does a powerful, secure communication platform for production control and data exchange with the cloud and other IT services. Important production features in systems of the Industry 4.0 generation include the synchronized production of item parts distributed over multiple locations of the same manufacturer, or of different manufacturers, and the flexible production of custom products, even down to a lot size of one. This latter feature, in particular, requires the use of new production methods and presents a higher need for standardization in proprietary fields that are being implemented in individual companies today.
Industrial communication will become substantially more critical and more dominant as a result of this changing environment. This changing environment is also the driving force behind the new strategic direction of technological developments at PROFIBUS & PROFINET International (PI), from the previously communication-oriented portfolio to an information-oriented portfolio. Besides PROFINET’s targeted advancement in line with Industry 4.0, innovations also relate to IO-Link, particularly in semantics and information models. These innovations take into account current security-related demands and newly emerging business models.
The IEEE Ethernet standards continue to form the basis for PROFINET. Exciting projects are currently underway in two areas at this standards organization. For one, a real-time Ethernet solution is being developed with TSN, with features designed for industrial automation. For another, a new physical layer is being developed for two-wire lines, for applications that require longer distances to be covered.
Integration of TSN in PROFINET
The development of Ethernet in the IEEE 802.1 standards offers real-time functionality for all industrial automation applications. It preserves a high degree of robustness with high network loads and the necessary determinism for time-sensitive applications, including motion control. In the integration of TSN in PROFINET, the working groups that are responsible for PROFINET drew upon parameters specified in the relevant IEEE 802.1 standards. Here, the most critical functions include synchronization (802.1 ASrev), time aware shaper (802.1Q), and preemption (802.1Q). Since TSN only defines a layer 2 for communication, it was easy to integrate TSN into the PROFINET application protocol. However, a significant finding of the work up to this point was that the simple configuration of TSN network parameters would be crucial for its acceptance by users. That’s why PI largely prefers the IEEE’s decentralized configuration model.
An inherent part of the TSN strategy is that PROFINET can also work with subordinate TSN at the field level. The user layer remains unchanged here – including, in particular, access to data, diagnostics, and profiles such as PROFIsafe. Besides RT/IRT for PROFINET, TSN offers an additional layer 2 access to a convergent Ethernet-TSN network.
The integration of TSN into PROFINET involved the selection of parts from the portfolio of extensive TSN features. Those parts provide the most significant benefit and are defined in a way that can be scaled to fit the specific requirement of the device functions.
Another critical step was to determine which TSN hardware-related features should be made available to support a correspondingly long-term development plan. The features will likely bring about more possibilities for the device design. PI anticipates that new standard Ethernet components will be available with TSN in the near future – which would give PROFINET an easy entry into the Gbps market, besides the 100 Mbps.
Two-wire Ethernet for PROFINET
While with TSN the IEEE has provided several new standards for Ethernet from layer 2 upward, the IEEE also has started a project for a new Ethernet layer 1 standard. Current Ethernet standards (e.g., 100/1000BASE-T) do not meet all of the requirements for connecting process sensors and actuators in the field. Such conditions include two-wire-based communication for greater distances of up to 1,000 m segment length and the supply of power to the process sensors/actuators over the two wires parallel to communication.
To have available solutions that meet these requirements, the 802.3cg Task Force was established in the IEEE. Its goal is to provide a standard for a data rate of 10 Mbps for full-duplex communication over a two-wire line with an optional power supply of the connected terminal devices over the two-wire line (Power over Data Line). Based on the IEEE standards, ASIC manufacturers started the development of Ethernet PHYs, which can be implemented in the areas above and in other domains.
However, the distinctive characteristics of explosion protection, which plays a crucial role in various areas of process automation, are not considered in the IEEE. As a result, PI – in cooperation with the two organizations ODVA and FieldComm Group and with 11 industrial partners – launched the Advanced Physical Layer (APL) project. The project will develop a solution for corresponding enhancements to IEEE 802.3cg, taking NAMUR requirements into account.
Another essential core task of the APL project team is to define the requirements and measures for the interoperability of APL components. The task includes the specification of intrinsically safe communication and power supply with the relevant profiles and associated profiles so that industrial Ethernet field devices can be used. It also includes the stipulation of criteria for assessing the devices’ conformity to the specification.
Horizontal M2M and Vertical Communication
When it comes to horizontal communication between different controllers and vertical communication with higher levels, PI relies on OPC UA. Object orientation, simple browsing, and integrated security mechanisms with OPC UA enable users to implement the requirements at this level more easily. In most cases, this works based on the TCP/IP protocol, which has been available for years and can coexist in PROFINET networks. It also works through the use of new mechanisms such as Pub/Sub and TSN.
The transitions from PROFINET to OPC UA require a standardization of data formats. The solution to this task can be found in the framework of the cooperation between PI and the OPC Foundation to draft an OPC UA PROFINET Companion Specification. The companion specification will define the OPC UA Information Model for the presentation of the standardized PROFINET object model (object dictionary).
This OPC UA information model is intended to enable OPC UA services to access the objects of PROFINET devices independent of the vendor. Access can be established either with an OPC UA server integrated into a PROFINET device or with an OPC UA server that compiles object dictionaries from multiple PROFINET devices. This data access allows horizontal communication between PROFINET devices and OPC UA devices at the field level, and vertical communication that is initiated by devices at the process or company level. In the first step, the topics of asset management and diagnostics were addressed.
Until now, fail-safe communication via a fieldbus or industrial Ethernet has been limited to pure master-slave or controller-device architectures. Since PI decided upon OPC UA for connections between controllers in PROFINET networks, it seemed reasonable also to extend the PROFIsafe mechanisms to OPC UA. To this end, the OPC Foundation and PI cooperated in the development of a “PROFIsafe over OPC UA” standard for the application of fail-safe controller-to-controller communication.
Standardized Classification of Parameters
The realization of a digital factory must be based on a high degree of machine-processable standardized information that is available across companies and industries. PI is already on its way to creating the necessary basis for this. In a first step, this would be accomplished by providing device-related expertise – for instance, in the form of parameters in device profiles and specifications for the application layer, like for an asset management record. However, for these to be used as the basis for a machine-processable flow of data across various systems – from sensor to cloud – the data must be transformed with semantic standards into clearly usable information. In cooperation with [email protected] e.V., the device parameters defined in PI’s specification documents will be expanded to include semantic identifiers. In an initial step, the established joint working group will determine the relevant parameters of the PA Profile 4.0, to then assign semantic identifiers to them. The results are documented in a mapping table, which both organizations can use. On the part of [email protected] e.V., the device parameters being handled in the scope of the cooperation are being incorporated in the [email protected] product description system and provide the necessary semantic identifiers.
Industry 4.0 defines the specific aspects of the digital transformation for production. Today, PROFINET has become established as the leading standard in all production fields worldwide. The increasingly specific topics emerging in this environment have set the course for the development of PI’s technologies – above all for PROFINET. The topics outlined in this article are the first step in the direction of digital transformation and as the basis for further activities. The objective is to follow the promising trends and to recognize what is relevant and vital for the sustainability of PI technologies. After all, the appropriate continued development of these technologies guarantees long-term business success to companies that integrate them into their products. PI has been applying this principle from the very start and accounts for its continued success over nearly 30 years already. And it’s one of the main reasons why companies are increasingly relying on PROFINET solutions.
Dr. Peter Wenzel