Information and communication technologies play a key role in implementing Industry 4.0 concepts. Cyber-physical systems such as sensors, actuators, embedded computers, smartphones and machines are connected to one another and exchange data both between themselves and outside of the factory work floor. Today’s automation networks and fieldbus systems must therefore not only guarantee that machines and facilities can carry out production with safety, precision and efficiency, but they must also help towards establishing a universal solution for integrating different IT systems on different rungs of the organizational ladder within a factory.
The fourth industrial revolution will result in dramatic upheavals within the industry similar to those we have already experienced in the private sector when introducing the Internet and mobile communication. One can expect flexibility from Industry 4.0 in production processes that has never before been available. Processes will become more energy and resource efficient. The machines are therefore able to influence production/planning systems or stock management directly. It also means that manufacturers can be contacted directly when their products experience gradual wear and tear so that condition monitoring and preventative maintenance can be started, therefore minimizing dead time and optimizing productivity.
When we have a closer look at today’s situation, we recognize that an increasing number of manufacturers are using Industrial Ethernet solutions to implement new machine concepts and to connect systems. The advantages over traditional fieldbus systems are obvious. There is sufficient bandwidth available to transmit safety-critical data as well as IT protocols via a common medium in addition to fast real-time data transmission. In addition, users and manufacturers benefit from the use of standardized Ethernet hardware, such as passive and active infrastructure components.
However, a uniform standard remains a dream: There is a large number of competing communication solutions and although they all use the widespread Ethernet technology, they specify different protocols and profiles in the superimposed ISO/OSI layers. Thus, devices that support different Industrial Ethernet standards are not compatible or interoperable with each other. Moreover, most devices that support different real-time Ethernet protocols cannot coexist in a common network, thereby losing the advantages of a common network standard. Most real-time Ethernet solutions use the network on an exclusive basis, meaning that only devices of one’s “own” protocol can be operated on the network. Devices that support other real-time Ethernet protocols, as well as standard Ethernet protocols, can be connected only via gateways or special switches. Other protocols can only be transmitted over the network by tunnelling them over the underlying real-time protocol, which can significantly harm the functioning and performance of a system. The future Ethernet IEEE 802.1 TSN (Time Sensitive Networks) standard will eventually make time-controlled transmission of real-time critical messages via standard Ethernet components possible. Most likely, this Ethernet TSN technology will have a significant impact on improving the heterogeneous landscape of real-time Ethernet dialects.

Important Role of OPC UA

OPC UA plays a very important role in advancing the convergence of IT and automation technology, thus enabling the consistent exchange of information from the corporate level down to the control or field level. From a technical perspective, OPC UA is characterized by the fact that it contains both, mechanisms for data exchange and an information model which allows the structure and semantics of the information exchanged to be defined. This technology can not only be integrated into devices on any platform with various programming languages, but systems of any degree of complexity can be fully described with it. In addition, the OPC UA technology is standardized on an international basis and has very wide acceptance from manufacturers and users worldwide.
However, although OPC UA is in fact a communication standard that extends from the enterprise level down to the control & field level, it has two key limitations. One is that OPC UA can use or replace existing fieldbus and Industrial Ethernet systems only where there are no specialized and sophisticated time- and deterministic-communication requirements. The other limitation is that OPC UA only defines how data are described and exchanged. The actual meaning of the data, which is generally understood and defined as semantics, is not defined.
A very promising approach is therefore to combine and map the existing real-time Ethernet protocols and the respective profiles with OPC UA. In doing so, process and device data are made available not just locally via the respective real-time network but also via any superordinate network infrastructure, e.g. the Internet or Intranet, via OPC UA, in a uniform and cross-manufacturer manner. Thus, not only is data exchange between the machine periphery and superordinate IT systems simplified, but the requirements of Industry 4.0 with respect to semantic interoperability are also supported.
In this scenario, real-time capabilities of OPC UA are not required, as the real-time performance is guaranteed by the respective underlying real-time network. Of course, application scenarios are possible in which a real-time capability of OPC UA is necessary, for example in machine-to-machine communication or in the linking of process-related machine periphery via OPC UA. For this, the so-called OPC UA publisher-subscriber protocol extension in combination with the future Ethernet TSN standard is positioned.
In order to apply OPC UA in a consistent way down to the field level, without affecting the performance and real-time characteristic of the underlying real-time network, the real-time networks need to be capable of supporting the multi-protocol capability, meaning that real-time protocols and IP based protocols can coexist and at the same time can run independent of each other.
If these requirements are fulfilled, today’s bus systems in combination with technologies such as OPC UA and Ethernet TSN can make a significant contribution to the further convergence of information and automation technologies. Let’s make it happen.