Tuesday, September 11, 2018

Model-Driven Vertical Integration: Transforming between Production System Models and MES/ERP Models

Introduction

Manufacturing companies usually run a number of different software systems to monitor and control their operations from business aspects to their production systems. A fundamental concept to describe the different levels of control is captured in the functional hierarchy model.

Functional hierarchy model for a manufacturing enterprise, depicting the five hierarchy levels in industrial automation.

This systems' separation leads to technical barriers. In order to overcome these barriers, international standards have been developed, such as the IEC 62264 series of standards that tries to harmonize levels 3 (MES) and 4 (ERP) and thus foster vertical integration.
In further steps, modern and smart manufacturing in production companies require deeply integrated IT systems to provide flexibility and rearrangement. Approaches like Industry 4.0 aim at flexible production network that additionally require horizontal integration across companies. Thus, there is also production related information exchanged in the network, which must be vertically forwarded to the corresponding service endpoints of the local production system.
To fulfill above requirements, two kinds of system integrations are required:
  1. Horizontal integration for the linking and seamless communication of systems in the network on the same hierarchy level.
  2. Vertical integration for the integration within one production system, from the business floor to shop floor. Vertical integration can go far beyond the manufacturing or management layers and down to programmable logic controllers and even single sensors. Practically all companies share the same vision for the future, automation and individualization of the complete manufacturing process, from product description, over order production to logistics and delivery. In order to create this vision in the real world, different business partners are required for executing specific processes, provide these capabilities in service and work with standardized horizontal and vertical information linking.
Model-Driven Engineering (MDE) is a software engineering development methodology that focuses on creating and exploiting domain models, which are conceptual models of topics related to a specific problem. MDE has developed a rich palette of tools and techniques for the description and manipulation of software models including model-to-model transformations, model validations, querying and many more.
In this blog post, we will showcase the application of Model-Driven Engineering in the field of automated production systems, focusing on vertical integration by aligning AutomationML, IEC 62264 and B2MML. For example, a digitized shop floor is much more flexible and open to adaptations when digital standardized system models are used, rather than it has been the case in the past when required rapid adaptations in the business models were necessary to provide up-to-date service descriptions.
Our digital shop floor is encoded in XML-based AutomationML (AML), for the MES to ERP integration we are using IEC 62264 (specifically, its second part) and its XML serialization B2MML. The focus in the implementation is on transforming between these three standards and extracting information into persistent document files.

Implementation

In this section we give an overview of the different transformation implementations between AutomationML, IEC 62264-2 and B2MML, based on the ATL Transformation Language for Model2Model (M2M) transformations and the Xtend Java dialect for Model2Text (M2T) transformations.

Implementation tasks overview

  1. ATL M2M Transformation: AutomationML <-> IEC 62264-2 pure.
  2. ATL M2M Transformation: B2MML <-> IEC 62264-2.
  3. Xtend M2T Transformations:
    1. 3.a AutomationML model to .aml document file.
    2. 3.b B2MML model to .b2mml document file.
  4. Additional Tasks:
    1. 4.a ATL M2M Transformation: AutomationML <-> IEC 62264-2 light.
    2. 4.b Unidirectional cross references from .aml document files to .b2mml document files.
The pure transformation considers all components and details, whereas the light transformation only transforms main components and leaves details to separate B2MML files which are referenced. The metamodels of AutomationML and IEC 62264 were provided in advance, whereas the B2MML metamodel was generated from an XML schema.

Conclusion

In our technical section we implemented model transformations, code generation and Java programs for adapting the model instances to achieve the goal that one single model is available in three different languages which are B2MML, IEC 62264 and AML and in their XML representation as files. The translation between all of these instances is very fast and can be used to improve collaboration between tools using one of the languages. One future task would be the implementation of bidrectional transformations between IEC 62264, AML and B2MML. With this improvement it would be possible to change between the languages very fast and so the model can always be adapted to the language currently needed. Other tasks which can be done after this project would be the changes in the transformations like the generation of real GUIDs or the transformation of other concepts in these languages which had been neglected such as transformations of ProcessSegmentCapabilityModel etc.


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