1. PROSA, a reference architecture for holonic manufacturing systems dr. ir. Jo Wyns KULeuven / RealSoftware PMA KULeuven Jo.Wyns@advalvas.be http://www.mech.kuleuven.ac.be/~jwyns the key to support evolution and reconfiguration

2. Manufacturing control logistical planning technological planning, late design decisions resource allocation downloading of NC- programs tracking of materials, tools, people,... etc. => but broad in space and time

3. Problem statement Disturbances –machine break-down –rush order –missing tools –missing materials –absenteism –etc. On-line manufacturing control algorithm Changes –new technology –new markets –new products –new organisational structures –etc. Manufacturing control system architecture

4. Reference architecture Manufacturing control system System architecture Reference architecture HW/SW, implementation blueprint, components, interactions style, types of components and interactions executeabstraction, communication, indicate vital components reduce development time, increase quality, unif. terminology buildingplans, sketches, specifications building style, construction elements,... What Goal Analogy

5. Requirements low price (build & maintain) predictable operational performance broad working range (flexible, robust, availability,...) Manufacturing control system System architecture Reference architecture reuse of components customised logistical and technological solutions extendable & adaptable decoupling generic applicability self-similarity

6. Evaluation of reference architectures Direct comparison hierarchical and heterarchical architectures Objective evaluation –compose list of requirements –find metrics Critique of end-users, developers, researchers,... REMARK: Paradigm dependency

7. Hierarchical control (ex.)

8. Heterarchical control (ex.)

9. Hierarchical vs. heterarchical control Every child node has only 1 parent. Master - Slave Low Adaptability Low support for Evolution => for large systems => not for dynamic systems (changes/disturbances) Distributed No supervisory control Negociation No global optimisation => for homogeneous systems => not for large systems

10. Lessons learned New approach shall provide –Dynamic structure –Decoupling of system structure from control algorithm –Reactive scheduling and process planning –Generic applicability

11. Holonic manufacturing systems (HMS) Manufacturing holon Holon whole, autonomy part, co-operation Stability decoupling self-similar

12. PROSA: basic holons

13. Basic holons

14. Aggregation hiding details in aggregated structures open-ended at top and bottom multiple aggregations (not tree-shaped) not static, may change dynamically resource, product, order aggregations

15. Aggregation

16. Specialisation Different types of resources: –Processing resources, workstations, –Transport resources, transport system –... Different types of orders and products: –Stock orders, customer orders –Different product families

17. Specialisation

18. Staff holons Basic holons + aggregation + specialisation –only heterarchical control (aggregation contains no control functionality) –distributed system But... –centralised problem solving is sometimes easier (e.g. scheduling) –hierarchical structures in factories

19. Staff holons Expert gives advise to the basic holons Holonisch manufacturing system –distributed system: robust and adaptable –ability for centralised functions Behaviour: hierarchical, heterarchical, and mengvormen zijn mogelijk

20. Staff holons (3)

21. Flexible assembly system Apply PROSA to real machines (robots & PLC) Switch between real machines and simulation (virtual factory) Logistical decisions –replaceable dynamic market mechanism –reactive centralised scheduler and schedule execution

22. Flexible assembly system

23. Example

24. Horizontal self-similarity Specialisation uses inheritance (OO) All kind of resource holons share common interface and behaviour; idem for order holons and product holons => Special cases/types can be handles similar to nominal ones e.g. rush order; first-of order; high volume vs. high quality product;

25. Vertical self-similarity Holarchy is a resource holon on itself; resource holon can internally be a holarchy Homogeneity in internal functioning of holarchies Resource holon is independent of holarchy to which it belongs e.g. belong to multiple holarchies at the same time (human)

26. Self-similarity (3)

27. Conclusion PROSA: Product-Resource-Order-Staff Architecture –necessary basic holons –optional staff holons –generalisation of hierarchical and heterarchical architectures –software framework

28. Conclusion Evolution & reconfiguration –decoupling of control algorithm from system architecture –decoupling of logistical and technological aspects –self-similarity

29. New opportunities On-line technological planning and design decisions Hybrid control algorithms Self-generating manufacturing control systems

30. More details on PROSA Van Brussel, H., J. Wyns, P. Valckenaers, L. Bongaerts, P. Peeters, (1998) Reference Architecture for Holonic Manufacturing Systems: PROSA, Computers In Industry, Special Issue on Intelligent Manufacturing Systems, Vol. 37, No. 3, pp. 255 – 276. Wyns, J. (1999), Reference architecture for holonic manufacturing systems - The key to support evolution and reconfiguration, Ph.D. thesis, ISBN 90-5682- 164-4, K.U.Leuven. http://www.mech.kuleuven.ac.be/pma/research/hms http://www.mech.kuleuven.ac.be/~jwyns

31. Software framework Translate reference architecture into software Framework –co-operating abstract classes –basis for implementing a specific manufacturing control system Add classes to support implementation

32. Integration with scheduling Planning = advise: –what, when, how? –not: invent standard for planning advise –but: design pattern for integration Solution: multiple decision taking algorithms + one selection algorithm in order holons

33. Integration with scheduling

34. Man-machine interface