Mechatronics modeling methodology and semantic orientated knowledge base.

Sell, Raivo ; Seiler, Sven

1. INTRODUCTION

At a present moment many new established SME-s in Europe are trying to start their own mechatronic or robotic product in this rapidly growing market. The main problem is that the initial start is usually a resource demanding process if company does not have previous knowledge. Big companies have several advantages over the newcomers with their human resources and knowledge bases. However new companies are much more flexible and can develop custom solution for mechatronic problem which might not be interesting for big companies due the small market or low profit. According to these issues we propose the open mechatronic knowledge base environment for universities and SME-s to collaborate and share the models of a common mechatronic and robotic solutions. The design concept is based on Model Based System Engineering approach by using new System Modeling Language (SysML, 2008) technique. For the knowledge base a new web based environment with a semantic orientated approach is used. The research proposes the methodology and tools for flexible and rapid start-up of a mechatronic product.

2. STATE-OF-ART

A knowledge base (also known as A or KB) is a special kind of database for knowledge management and presentation purposes. A knowledge base is providing the means for the computerized collection, organization and retrieval of knowledge. Two types of KB can be distinguished, machine-and human readable ones. We are talking here only about web based solutions; there are also KB software products with rich clients available on the market.

A special kind of KB, also worth to mention would be a common sense knowledge base, which stands for the representation of facts and information an average person is expected to know. This knowledge accumulation is used by artificial intelligence programs to reason about it by using natural language. This database, which is in fact ontology, shall be created in the research.

On the market several solutions for knowledge bases, like "Knowledge base Manager Pro" exists. Only a few, like "Open Mind Common Sense" by MIT Media Lab (OMCS, 2009), which are common sense knowledge bases are offering semantic technologies.

These solutions are good for the general representation of knowledge, but we are developing a more special KB for the system engineering and mechatronic area and representing the content of system modelling software, like Artisan Studio or any other SysML product, by the use of special XML interfaces for each product to convert the data from one data model to another.

3. DESIGN METHODOLOGY AND ROBOTIC MODEL KNOWLEDGE BASE

The mechatronic system design methodology for conceptual stage developed in cooperation with Tallinn University of Technology and Helsinki University of Technology (Sell et al., 2008; Christophe et al., 2009) is a base framework for the web environment. The web environment is a knowledge base with user interface providing the mechatronic model browsing, exchange, update and traceability. The model repository is freely available for engineers from universities and SME-s. Following to this, new profiles and models can be created by the practicing engineers in industry and researchers in academic institutions. The knowledge base is as a free environment for mechatronics community. This is extremely important for SME-s to get the benefit from unified product development methodology and free, already validated component and modules for innovative product development.

3.1 Framework for mechatronics product design

The framework approach represented at Fig. 1, describes the framework concept on tackling the entire conceptual design process from the refinement of ill-defined problems to the evaluation of the ecological impact of the product through its life-cycle.

[FIGURE 1 OMITTED]

The first stage of conceptual design involves an important part of problem solving issues: the refinement of ill-define problems with the refinement of verbal requirements into formal requirements represented with SysML Requirement diagrams. This type of diagram defines requirements hierarchically with relationships and custom parameters. Concurrently, the verbal requirements are analyzed in order to extract the expected functionalities of the future product. This analysis allows the creation of Use Case diagrams presenting the system-to-be and its surrounding environment i.e. external actors. More detailed insight into the needed functionalities enables the creation of functional architectures developing different functional structures represented as "black boxes" with SysML Block Definition diagrams and functional blocks (Chiron & Kouiss, 2007).

Following the refinement phase of conceptual design, the synthesis of concepts phase has the aim to transform functional models into structural models enabling the system's organisation in sub-systems and components. The evaluation phase of conceptual design is done with the help of behavioural diagrams of different types. Activity diagrams, Sequence diagrams and State Machine diagrams are derived from both requirements and functional architectures and represent the behaviour expected from the system. Similarly, the same set of diagrams represents the structural behaviour of the system and is derived by designers from the Block Definition diagrams representations. Additionally, SysML gives the possibility to use several libraries of existing subsystems as well as libraries for the simulation of the system's behaviour. Proposed KB is providing these libraries for the engineers.

3.2 Technical overview of knowledge base design

The whole system is based on a open database for storing the meta information according to imported data and files and for the user management relevant information. The files themselves are stored directly in a hierarchical file system structure on hard disk. The programming is realized using the Prototype framework for Ajax functionality and PHP in version 5 for the logical implementation to create an intuitive GUI for the user. Based on meta information and the data extracted from the XML based models are used to make automated cross linking between different models. Therefore the system is possible to "self-train", as new information is uploaded. According to the commonsense knowledge base approach mentioned in the State of Art section, a ontology based on the models (Seiler, 2009) can be built up to share them with SME-s and other experts. The general KB is able to interchange between different modelling tools, as presented in Fig. 2.

[FIGURE 2 OMITTED]

The knowledge base uses a hierarchical, file system like structure which allows browsing through the different models and will reason with them, when they were uploaded.

4. CONCLUSION

The proposed solution together with knowledge base support enables to develop the mechatronic systems based on the synergy principle focused on the early stage of the product development process.

The relevance for the economy is the easier start of the new and innovative product development process. A knowledge base with pre-defined models and toolkits enables for SME-s to compete with big companies on the complex and high tech mechatronics system (e.g. service robot) market. SME-s can use his advantages like flexibility to develop the innovative product without having big resources for research and component development. Already validated and pre-defined components and models with supported methodology can be freely acquired from the knowledge base. In addition the common environment activates the cooperation and communication between SME-s and research institutes. The solution has however risks, mainly related with human behaviour and working experience. Making a conceptual step from document based design to model based design might be difficult for designers, especially for older generation. Educating and hands-on training can be used to minimize this risk.

In the next step, we will extend the knowledge base further to be open to implement more external data sources (from the web) and link them to our existing ones. This shall lead to a new kind of interconnected commons sense knowledge base for the domain of system engineering. It is planned to develop converter from different modelling tools for SysML to a generic XML (XMI), which will then be used in the knowledge base. This XML data can also converted to other formats or on the fly for displaying the models directly out of the KB.

5. ACKNOWLEDGEMENTS

This research was supported by the Estonian Scientific Foundation grant ETF7542.

6. REFERENCES

Chiron, F.; Kouiss, K. (2007). Design of IEC 61131-3 Function Blocks using SysML, Proceedings of Mediterranean Conference on Control and Automation, pp 915-919, ISBN: 978-1-4244-1281-5, Greece, July 2007, Athens

Christophe, F.; Sell, R.; Bernard, A.; Coatanea, E. (2009). Ontology Processing For Assisted Synthesis of Conceptual Design Solutions. Proceedings of the ASME 2009 International Design Engineering Technical Conferences & Design Automation Conference. USA, ISBN: 978-0-78183856-3, August-September 2009, San Diego

Seiler, S (2009). Approaches to use Semantic Web Technologies in Smart houses, Master Thesis, Estonia, 2009, Tallinn

Sell, R.; Coatanea, E.; Christophe, F. (2008). Important Aspects of Early Design in Mechatronic. Proceedings of the 6th International Conference of DAAAM Baltic Industrial Engineering, Kyttner, R. (Ed.), pp 177-182, ISBN: 978-9985-59783-5, Estonia, April 2008, Tallinn

*** (2008) http://www.omg.org/spec/SysML/--System Modeling Language (SysML) specification, Object Management Group, Accessed on:2009-09-01

*** (2009) http://commons.media.mit.edu/--Open Mind Common Sense, Accessed on:2009-09-01