The reference architecture model of the future project Industrie 4.0 (RAMI 4.0) was first presented at the Hannover Messe 2015 with the publication of the implementation strategy for the fourth industrial revolution. Since then, the Industry 4.0 dialog platform, which has been expanded to include other stakeholders from politics, business and trade unions, has been working on key topics in five working groups under the auspices of the Federal Ministry for Economic Affairs and Energy (BMWi) and the Federal Ministry of Education and Research (BMBF). These include standards, work, security (information security and functional security), law and research.

Due to its complexity and the unfamiliar three-dimensional representation, the use of RAMI 4.0 in associations, standardization organizations and industrial companies sometimes proves to be a challenge. Support is therefore needed that goes beyond the description in the implementation strategy.

Reference models for network protocols: In addition to the OSI model, other reference models adapted to the intended use have become established in technology; the same is also conceivable for RAMI 4.0.

© Phoenix Contact

According to the Industry 4.0 glossary of the VDI/VDE-GMA 7.21 'Industry 4.0' expert committee, a reference model is defined as a model that is generally used and recognized as appropriate (with a recommendation character) to derive specific models. There are many examples in technology. The best known is certainly the OSI model (later ISO/OSI model) as a reference model for network protocols, which was developed at the end of the 1970s and is still used in network and communication technology today. The OSI model is made up of seven layers. Each layer is assigned specific tasks that are required for data transmission between two end devices.

In addition to the OSI model, slightly modified models have been established that address other application domains - for example, the Internet model with four layers or the TCP/IP reference model with five layers. However, all modified variants can be transferred to the OSI model. The advantage of using such reference models lies in the common understanding of the functionality to be provided by each layer and the defined interfaces between the layers. In this way, competing implementations can be created, which are then documented in widely used norms and standards. An example of this are the Ethernet standards developed under IEEE 802, which are assigned to layers 1 and 2 in the OSI model.

Industrial production as a field of application

When developing RAMI 4.0, the focus was on industrial production as an area of application. The spectrum ranges from discrete manufacturing to process technology. The focus on industrial production (smart production) distinguishes the future-oriented Industry 4.0 project from the broader IoT (Internet of Things) approach of the Industrial Internet Consortium (IIC). In addition to smart production, IoT includes areas such as smart home, smart mobility and healthcare.

... the SGAM framework, which was published by CEN, CENELEC and ETSI in 2012 to enable European standardization organizations to identify and further develop relevant standards in the field of smart grids.

© Siemens

In the committees of the association platform, it became clear that an architecture model, which should serve as a reference and enable a targeted discussion, for example with regard to standardization, requires a three-dimensional representation. Accordingly, the three axes of RAMI 4.0 describe the hierarchy levels of a production plant networked via the Internet, the life cycle of plants and products and the IT representation of an Industry 4.0 component. The already established Smart Grid Architecture Model (SGAM), which focuses on energy generation and distribution, served as a template for this.

The hierarchy levels of a production plant essentially resemble the levels of the familiar automation pyramid. Formally, the plant hierarchy is derived from IEC 62264 and IEC 61512, but products and field devices (from the automation pyramid) have been added at the lower end. The addition of the product proves to be necessary so that the control of the production plant can be represented by the product in the model. This is a key feature of Industry 4.0.

Necessary addition to the automation pyramid

The hierarchy of an Industrie 4.0 production plant can be derived from the levels of the extended automation pyramid; the functionality of the levels dissolves with Industrie 4.0.

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At the upper end of the hierarchy, the Connected World was added in order to represent the Internet-based networking of production plants that are located at different sites, for example.

The description of the life cycle of plants and products in RAMI 4.0 with its four characteristic value chains contained in the cycle ('Product and product line development', 'Process and plant development', 'Product production and after sales services', 'Technical plant') is based on the draft of IEC 62890. The standard distinguishes between type and instance in the life cycle. The type of a product is created in several phases during the development process. It is completed with the release of a special product version. Based on the type released for series production, the plant then manufactures products that are instances of the type. Component discontinuations or improvements may necessitate changes to the products. They are made to the type and, once the adaptation has been completed and released, are introduced into production as a new product version.

Sensible clustering of complex processes

The data generated in the process chains - such as the layout, parts lists or quality data from production - is already largely available in digital form. They are then processed in PLM (Product Lifecycle Management) and ERP (Enterprise Resource Planning) systems. However, there is potential for optimization with regard to the standardization and harmonization of this data, as depending on the system used, the data has to be converted and sometimes reworked manually. This makes it difficult to exchange digital information across manufacturers. At this point, the manufacture of individual products also requires the possibility of storing data that the customer has transferred to the manufacturer for the production of their instances in a suitable form electronically in the IT systems with the instance-related data. It must be available over the entire life cycle of the instance and linked to the associated type.

In line with the IT mindset, the IT representation of an Industrie 4.0 component is visualized on the vertical axis using six stacked layers. The layers illustrate the view of business processes, functional descriptions, data images, communication behavior including quality of service (QoS) and the connection of assets via an integration layer. This approach, which is unusual for automation technology, is successfully used in IT to cluster complex processes.

In connection with the asset layer, the question often arises as to which elements belong to this layer. In addition to physical elements such as products, parts, components, machines or systems, the asset layer also includes data from the development process.

An example of this is a product document, which contains all the data generated during the development process for the construction of the item, as well as the device firmware created during the development process. The data generated during production, some of which is customized for the specific instance, should also be considered an asset. In this sense, the human operator, service technician or programmer who interacts with the assets via the integration layer must also be located on the asset layer. By clearly identifying all Industry 4.0 components, the arrangement of all assets offers greater scope for asset management, which can already be found in IT environments today. Such a scenario also simplifies the threat analysis of the production plant that needs to be carried out for IT security reasons.

RAMI 4.0 does not envisage a separate layer for IT security - or functional security - as the topic is an integral part of the future project and must therefore be considered as part of the design of an Industry 4.0 solution. The assets must have or provide the security properties required for their task and protection at all hierarchy levels. The respective owner - for example, the developer or plant operator - must take IT security into account over the entire life cycle of the assets. In short: from an IT perspective, security affects all layers and must therefore be assessed holistically.

Communication via the established protocols

Role-based representation in RAMI 4.0: The image clearly shows the different views of an asset for component manufacturers, machine builders and plant operators.

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A use case that includes the roles of component supplier, machine builder and plant operator, for example, should be mapped in RAMI 4.0 in such a way that a RAMI 4.0 image is drawn for each role. The example of the asset layer shows that the position of the asset on the asset layer in RAMI 4.0 changes depending on the role and life cycle.

In the context of Industry 4.0, many users are asking themselves where the established industrial communication systems - such as fieldbuses - should be classified and whether their role will change in the future. It should be noted that the protocols continue to connect assets (e.g. field devices and controllers) via the integration layer and the communication layer (e.g. Profinet). This does not contradict Industry 4.0. With the further refinement of the Industry 4.0 component and the associated asset administration shell, the first implementations of Industry 4.0-compliant communication and a representation of the information will emerge in 2016 and can be tested in test applications. In particular, the profiles and feature definitions developed by the user organizations can be transferred to the Industry 4.0 world. This simplifies mapping to an Industry 4.0-compliant 'information layer' or 'function layer'.

New results for the Hannover Messe 2016

The ZVEI seal committee 'Models and Standards' has further detailed the definition of the Industry 4.0 component and the structure of the asset administration shell since April 2015. The results will be published at Hannover Messe 2016. Visitors to the Industry 4.0 Forum (Hall 8, Stand D19) will have the opportunity to find out about the current status of the work and enter into dialog with the experts from the Industry 4.0 Platform working groups.

Author:
Frank Schewe is Master Project Manager in the Development Network Technology division at Phoenix Contact Electronics.