From the Digital Factory to the real plant: Speeding up the process

01 November 2007

What is Digital Engineering? It provides a seamless transition from plant planning, to electrical and mechanical design, to virtual commissioning, and support for plant maintenance and servicing.

The Digital Factory is already an integral part in the product development process in many companies and industries and is gaining increasing significance for small and medium-sized companies.

An integrated process chain--from the product idea to production--requires a seamless transition from the Digital Factory to the real plant. This demands a technology-spanning development environment that maps and merges all processes in the plant life cycle.

The speed with which a manufacturing company responds to market requirements is crucial to its success. It must be capable of quickly adapting its existing production equipment to changing conditions. New
plants must be set up quickly and with a high level of planning reliability and quality. Simultaneously, the increasing push from costs makes it necessary to raise productivity.

An established and proven solution to these challenges is the Digital Factory, which intertwines product development with planning of the production processes. In the future, Digital Engineering will provide methods within the scope of the Digital Factory to support all processes within the production process, starting with plant planning to electrical and mechanical design to virtual commissioning and support for plant maintenance and servicing.

All data are fed into configuration tools and collated regardless of the software used. The procedure for
product creation is digitally mapped in its entirety onto the production process.

The transition
When planning, developing, and building a plant, different departments with different software tools are
involved. The planning phase starts with initial data such as parts lists, purchasing conditions, and so on for needed resources such as roller conveyors. The further along in the plant development process, the more data are generated and assigned (see Figure 1).

During the mechanical design phase, basic data for a resource are defined such as a drive and sensor list, flow diagrams (electrical, pneumatic, and hydraulic) and 2D and 3D modules. Electrical design then adds more data such as electrical components, distributed I/Os, and any necessary software blocks. All these
different data are generated with specific software tools.

The data generated are stored in the databases of the respective software tools. A current weakness in the process is insufficient integration of different software tools and their data.

Users need a solution that enables a comprehensive view of all configuration data, supports one-time data entry and guarantees data consistency in all software tools involved. It must be possible to change parameters and attributes of the data without requiring the specific software tools.

The Simatic Automation Designer enables both the integration of any software tools and data objects and
integration into any user-specific system environment. In other words, it is an appropriate foundation for Digital Engineering.

Adaptable model
The performance of a configuration tool is primarily a function of its architectural model and its data model. During planning for the model design, it was necessary to take a more detailed look at the requirements resulting from the Digital Factory and the process environment, especially with regard to IT support. The following insights were paramount:

....A Digital Factory is always based on a user-specific process. The individual steps of this process are mapped onto the respective organisational units;

....Processes are subject to continuous changes based on efforts to optimise them or adapt them to new
circumstances;

....Standardisation of resources is an increasingly important factor for process optimisation. This simplifies
both configuration and plant maintenance;

....The resources are always defined according to their behaviour and properties in the plant. The relationships between resources are also defined in detail;

....The productivity level which can be achieved through software support depends on how well the individual
processes can be supported and how well the existing system environments can be mapped. That means that basic functions must be available which can be expanded with further functions specific to the process; and

....The plant layout serves as the central hub for interdisciplinary communications between different groups of people such as the client, plant engineering company, operator, and so on.

The following crucial model criteria were established based on these insights:

....Openness for integration into an existing process environment;

....Expandability to include new functionality should the processes change;

....Support for standardised resources and groups of resources based on a library concept with technological relationships between the resources;

....Integration of the plant layout to support interdisciplinary communications between all parties involved.

Architectural model
The architecture of a configuration tool for Digital Engineering must particularly support openness and expandability. Data interfaces are available in the form of XML-based import/export interfaces which enable the exchange and synchronisation of vast quantities of data with other software tools. For parallel
configuration tasks, bidirectional data exchange between the involved software tools is required. Change
markers, date information, unambiguous labelling (even for data taken from outside systems) are a central
component of the defined XML scheme.

Expandability is ensured through
functional interfaces. Extension packages can be added via these interfaces. These packages provide further functions and data structures and can analyse existing configuration data. For example, users can add on their own generators for the control programs of programmable logic controllers (PLCs) or other software tools. Extension packages can be obtained as an optional add-on from Siemens or from other suppliers.

Data model
Creating a data model basically requires mapping hierarchical plant structures, the use of libraries, and the inclusion of properties sorted according to different criteria. The following description only elucidates the parts of the data model which essentially contribute to increasing the productivity of plant configuration
(see Figure 2).

Plant components such as work stations, conveyor belts, and sensors are mapped using the element Resource. With Ports, users can describe the relationships between the plant sections. This includes both the 'make-up' relationships (for example, a conveyor belt is made up of belt, sensor, and motor) and functional structure relationships such as the material flow between Conveyor1 and Conveyor2.

In other words, one resource consists of various data which describe specific properties. For instance, this can be the PLC program part of a conveyor with a parameter such as the conveyor speed and the related sequential control. Furthermore, the data can provide interface definitions which can be assigned to the ports of the resource. This assignment literally provides resources 'with sockets and plugs.' Based on this, it is possible to derive several necessary signal relationships through one single port relationship.

Layout-based plant configuration As explained above, the plant layout is one of the main components of a
technology-oriented procedure. Therefore, graphical configuration of the automation solution is an elementary part of the Digital Engineering concept. This involves reading the plant plans (layout) into the configuration environment. Templates for resources which can consist of various data are available in libraries. These are placed on the layout and connected to it. Then, the material flow is configured (the
upstream / downstream relationships between he different resources) and the different functional groups such as the PLC areas, the console areas, the emergency-off circuits, the operating mode groups etc.

Digital Engineering enables layoutbased configuration of all resources and a description of the relationship
between the resources. By including the plant layout, users get a technological view of the plant which is useful for a transparent depiction of the plant and easy navigation.

The projects for the linked software tools are subsequently created nearly automatically by means of specific
program generators and always at the same high level of quality (as opposed to manual programming).

Near-real simulation
The next step in the engineering environment is virtual commissioning. Here, the virtual plant model already
used in the layout-based plant configuration is switched and controlled by the actual automation technology,
which consists of hardware and software. This phase of virtual commissioning acts as a near-real simulation of the real world without having to actually set up the real plant. That way, users can identify and eliminate any faults in the plant configuration before real commissioning.

What does virtual commissioning entail?
The first step involves testing the generated software project with the virtual data model of the plant in a
simulation environment. In the next step, the software is already running on the real PLC. The connected
field devices are still virtual. Then a real operator console can be integrated into this environment to verify operator control of the plant in advance. In other words, the virtual components are replaced by the real plant components step-by-step.

Virtual commissioning ensures high quality configuration at an early stage. That means less time is required for commissioning the real plant.

User support for the plant on-site
Another important step in future engineering environments will be user support for the plant on-site. The plant layout will be included in the HMI system. By linking the plant layout to process signals from the plant, users get a transparent overview of the plant. All information from the automation system--such as diagnostic information--is displayed directly in the plant layout.

The road ahead
Digital Engineering enables uniform methods, applications, and processes with a uniform database. As a result, this new engineering approach reduces costs, cuts planning time and improves the functional reliability of developed plants. The transition from the Digital Factory to the real plant is a substantial
contribution to advancing interdisciplinary co-operation across different departments.

With the technical solution approach presented here and the advanced technology it employs, Siemens
Automation and Drives (A&D) is a partner for further development and practice-oriented realisation of
innovative solutions.

We have made the first step in the direction of an integrated engineering world. There is still a great deal of
development ahead, but the achievements thus far have already proven themselves in initial user projects
for conveyor applications.

Dipl.-Ing. (FH) Maximilian Sackerer, and Dipl.-Inform. (FH) Soeren Moritz are at Siemens AG, Automation and
Drives, Nurmberg, Germany


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