PROSA, a reference architecture for holonic manufacturing systems dr. ir. Jo Wyns KULeuven / RealSoftware PMA KULeuven the key to support evolution and reconfiguration

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

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

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

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

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

Hierarchical control (ex.)

Heterarchical control (ex.)

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

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

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

PROSA: basic holons

Basic holons

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

Aggregation

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

Specialisation

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

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

Staff holons (3)

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

Flexible assembly system

Example

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;

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)

Self-similarity (3)

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

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

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

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 , K.U.Leuven.

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

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

Integration with scheduling

Man-machine interface