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Process models – Cinderella among design models

Process models – Cinderella among design models. Chris McMahon. Outline. Modelling in engineering design Product models Process and activity models Exploiting process models Recording the outcome of design processes A framework for capture of engineering experience

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Process models – Cinderella among design models

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  1. Process models – Cinderella among design models Chris McMahon

  2. Outline • Modelling in engineering design • Product models • Process and activity models • Exploiting process models • Recording the outcome of design processes • A framework for capture of engineering experience • As a basis for design reuse • Questions

  3. Modelling in Engineering Design Modelling pervades engineering design • The output from the design process is a collection of models of the designed artefact • Models are used to allow designers to work with the artefact in the abstract • Models are used to allow analytical and computational techniques to be applied in the evaluation of the artefact • Models are used to assist in manufacture

  4. Models of the Designed Artefact Engineering drawing picture here

  5. Models of the Designed Artefact Engineering diagram picture here

  6. Models of the Designed Artefact http://www.idtnet.co.uk/Idtweb_home1%20SR%20IR%20mirror%20CAD%20model.jpg here

  7. Models that Help to Work in the Abstract http://www.hq.nasa.gov/office/pao/History/SP-4009/images/1-086.gif here

  8. Models that Help to Work in the Abstract http://www.architecture.ca/firms/gearch/casaddledome/rendering.jpg here

  9. Models for Analytical Support FE and CFD pictures here

  10. Models for Analytical Support http://www.mfg.mtu.edu/cyberman/machtool/machtool/vibration/aniabsor.gif here

  11. Models for Analytical Support http://www.itl.nist.gov/div898/handbook/apr/section1/apr166.htm here

  12. Models to Help Manufacture Mould analysis picture here

  13. Models to Help Manufacture Machining toolpath picture here

  14. The Historical Growth of Modelling • The growth of modelling is part of a general growth in the codification of design. • Codification is used to help cope with complexity, and as a means of exercising control over the manufacturing process

  15. Process Modelling • Process models are used to describe and assist in planning and monitoring the design process and design activities. • Process modelling is used • To describe the overall process • To describe activities, information flows etc. • To help plan and manage the process • To assist in standards development, training, knowledge management . . .

  16. High-level Models: Bombardier Bombardier stage gate model here

  17. High-level Models: Airbus Airbus stage gate model here

  18. DESIGN STAGE DESIGN ACTIVITIES DESIGN PHASE TASK • Clarify task TASK • Elaborate the specification CLARIFICATION SPECIFICATION • Identify essential problems • Establish function structures CONCEPTUAL • Search for solution principles DESIGN • Combine into concept variants • Evaluate against technical & economic criteria CONCEPT • Develop preliminary layouts & form designs UPGRADE & IMPROVE • Select best preliminary layouts TIME • Refine against technical & economic criteria PRELIMINARY EMBODIMENT LAYOUT DESIGN • Optimise & complete form designs • Check for errors & cost effectiveness • Prepare preliminary parts list DEFINITIVE • Prepare preliminary production documents LAYOUT • Finalise details DETAIL • Complete detail drawings & production documents DESIGN • Check all documents DOCUMENTATION SOLUTION Pahl and Beitz Model

  19. Design Structure Matrix Design structure matrix picture here

  20. Integrated Definition, IDEF

  21. Integrated Definition, IDEF IDEF0 picture here

  22. IDEF0 in Standards IDEF0 picture here

  23. Petri Nets; UML

  24. How May Process Models be Used? • Let us start with two simple examples: • A conceptual phase design activity • concept selection • E.g. selection of a drive mechanism • A detail phase design activity • analysis • E.g. fatigue analysis of an automotive part

  25. Concept Selection High Level Conceptgenerationmethod Specification Selection methodology C Function model Concept selection Selected concept I O Product information M Designer

  26. Concept Selection Low(er) Level Conceptgenerationmethod Selection methodology Specification Functional model Possibleconcepts ChosenConcept Concept Selection Concept Generation Product information Designer

  27. Analysis guidelines Geometry Fatigueanalysis Estimated fatigue life Materialsdata Load cases Analyst Software& workstation Design Analysis High Level

  28. Design Analysis Low(er) Level Analysisguidelines Estimated fatigue life Geometry Fatiguelifeestimation Stresses Stressanalysis Materialsdata Load cases Analyst Software &workstation

  29. Recording the Design Process • The design process is currently recorded through text documents that provide reports on the outcome of activities/processes – e.g. (for the two examples given) concept design report, analysis report • By using more formal representations of process outcomes it will be possible for the information-dependencies and decision-making in the design process to be traced. • This will integrate product and process models. • It might build on XLANG, XRL, WSDL, PSL etc.

  30. How Might This be Done? • Document templates and mark-up may allow process outcomes to be recorded in a straightforward manner, e.g. <ACTIVITY RECORD> <ACTIVITY ID>Activity name</ACTIVITY ID> <ACTIVITY METADATA> Metadata describing activity </ACTIVITY METADATA> <SUMMARY> Activity summary </SUMMARY> <INPUT> Reference to input – URI, metadata </INPUT> : <MECHANISM> Reference to mechanism – e.g. staff input</MECHANISM> : <CONTROL> Reference to control – URI, metadata </CONTROL> : <DESCRIPTION> Activity descriptionand commentary – text </DESCRIPTION> <OUTPUT> Reference to output – URI, metadata </OUTPUT> : <COMMENTARY> Commentary on output </COMMENTARY>

  31. XML Record of Analysis Process <ACTIVITY RECORD> <ACTIVITY ID>Stress analysis</ACTIVITY ID> <ACTIVITY METADATA> Metadata describing activity – component, project, date, etc</ACTIVITY METADATA> <SUMMARY> Activity summary – objectives etc., and overall result </SUMMARY> <INPUT> Reference to input – URI, metadata for CAD model, material and load case data </INPUT> <CONTROL> Reference to control – URI, metadata for best practice advice </CONTROL> <MECHANISM> Reference to mechanism – staff and software details </MECHANISM> <DESCRIPTION> Activity descriptionand commentary – text </DESCRIPTION> <OUTPUT> Reference to output – FE output files and analysis summary data </OUTPUT> <COMMENTARY> Commentary on output </COMMENTARY> • Combined with consistent metadata this may make it very much more straightforward to audit the design process.

  32. Capture of Engineering Experience • Process modelling provides a basis for accumulation of engineering knowledge: • It provides a framework for representing understanding of the state of data, information and analytical relationships to be developed. • It allows verification and validation feedback from comparison of experimental and analytical results • It allows use of service experience to correct and update the understanding of the imprecision in engineering models, and to provide improved use case models for incorporation into future design processes.

  33. What is the nature of the error between analytical and experimental transfer function? • is it explained by uncertainty in data? Stress analysis Geometry Estimated stresses Materialsdata Load cases Transfer function Activity as Transfer Function

  34. Categories of Evidence • Design knowledge may be categorised according to the extent to which comparison of analytical and experimental results are available • Narrow or wide range of design parameters (e.g. one-off – narrow; mass production – wide) • Narrow or wide range of load cases (i.e. do we understand the way this artefact can be loaded in use?) • Point values or statistical variation in parameters and load cases

  35. Categories of Evidence • Direct evidence - evidence available for the specific design case. E.g. correlated analysis and experimental results for particular products • Indirect evidence - evidence is only available for related design cases and/or for parts of the process; evidence may be limited to qualitative evidence • Evidence of performance of similar techniques using similar models • Evidence of performance of parts of the process • Evidence of satisfactory/unsatisfactory performance of actual artefacts – e.g. some designs are known to exhibit weaknesses.

  36. Design Reuse • At present we largely concentrate on reuse of components and concepts: • E.g. part carry-over in automotive design; standardisation etc. – reduces inventory, tool costs etc. • Reuse can involve systems, sub-assemblies, parts, features – but so far little effort on reuse of activities

  37. Design Reuse • Knowledge of process may assist with conventional design reuse: • Using the “input information” for an activity assists in searching for outputs (case-based reasoning). • E.g motor selection based on motor application requirements • Capture of the design history, rationale and intent may give more confidence in reusing components and sub-systems.

  38. Design Reuse • But in terms of engineering activity, is there more scope for reuse of the process information itself? • Research in workflow modelling - standardisation of descriptions for reuse of workflow models. • Can we extend that to the reuse of the information processing patterns in design activities? • Example – INTEREST project Best Practice Adviser • Assembled best practice advice giving general advice, context-specific advice and examples, using a dynamic hypermedia approach and a repository of design advice and examples

  39. IINTEREST Approach Web Browser Internet - HTTP Web Server Dynamic BPA Page (XML or HTMLor DHTML) 3-tier Architecture BPA Assembler BPA Page template Virtual Repository Indexed JDBC BPA storage Virtual Repository Database

  40. INTEREST Project Topic Description At this stage, one may choose to simplify and idealise the CAD geometry. For example, only take a half model into account due to the symmetry, and remove some unimportant small details. However, this step could be skipped if analysts choose to model the whole geometry instead. General Information General information for activity "Simplify and idealise CAD geometries"General information on "How to simplify geometries"General information on "How to take advantage of symmetry" Context-specific information on its Geometric Features How to simply the geometry of filletsHow to simplify the geometry of radii Search results of the close matching algorithm

  41. Questions • Do process representations provide the opportunities that I have described, and do they work in an HCI context? • Do we need different fundamental modelling techniques for different process applications, or is there a “UPML”? • Can we integrate the representation of processes in general with the recording and representation of actual processes. Are different modelling methods necessary? • Does the model drive the design or does the design drive the model?

  42. Thank You for your attention Contact me at: Email: c.a.mcmahon@bath.ac.uk

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