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Expert Systems Presentation - Dr. George Power
Transcript of Expert Systems Presentation - Dr. George Power
Expert system-based optimization in wrought copper alloy productionDr.-Ing. George Power, Universidad de [email protected]
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Contents
Introduction to expert systemsRule-based expert system for job preparation in wrought copper alloy productionProgramming componentsResults obtainedSummary and conclusions
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What is an expert system?
Software for specific problem areas involving expert knowledgeDeveloped after AI’s failure of “General Problem Solver”Commercial XPS can be:
Case-basedRule-basedDecision trees
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Case-based expert systems
Databases of specific problems and their solutionsFor a given problem, the expert system tries to find a similar case and its solutionExample: Medical diagnosis –appropriate treatment for a patient with concrete symptoms
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Rule-based expert systems
Have a large set of “if-then-else”rules, algorithms, formulas, databases, etc.Business Rule Management Systems (BRMS) are specific for business aplicationsRules represent general cases from which solutions are drawnRules must be entered and maintained by experts
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Decision trees
Expert systems for classification tasksInductive learning based on a set of examplesObject attributes are knots of a search path or tree, characteristics represent linksGoal is the leaf or end knot gives the object class to be assigned
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Individual roles in expert systems
End-userInteracts with the XPS and can also supply some expertise
Problem domain expertBuilds and supplies the knowledge base, can also be the programmer
Knowledge (software) engineerAssists the expert in representing his knowledge
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Semis of wrought copper alloys
Source: www.wieland.de
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Manufacturing of flat products
Source: www.wieland.de
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Some fabrication parameters for Cu alloy sheet and strip
Material description (alloy type, temper, standards, …)Other technological properties (flexural, die wear, soldering tests) Hardening and softening behaviour (cold-work and annealing curves)Surface finish, protectionFabrication steps: hot rolling, cold rolling, annealing, pickling, stretching, slitting, traverse winding, etc.
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Why an expert system for job preparation?
Time-consuming consults to expertsHuge amount of data in production and customer specific proceduresDelays in job preparation increase lead times in PPSOrder changes and cancellations (storno)Reduce overhead costs
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Team structure
Material properties, machine specifications, databases, formulas
Quality Engineer
Machine setup, production, maintenance and down time, cost factors
Time and cost calculation
Object structure, production steps, resources (machines, materials), input and output forms
Job preparation
Programming tasksDepartment
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enginObject: An object-oriented programming tool for XPS
MaterialsMachines
Tools
tn = …
Preparation
Set up
SolderingDecision tables Databases
Formulas
Texty blocks
Development system
Planingdocuments Knowledge base Planing
algorithms
Shop specific planingknow-how
Job plans
CAD
CAM
PPS
SQLCreate plan
Edit / actualize job plans
SML
User system
Source: camos GmbH, 1994
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enginObject structureComponents:
Decision tablesProceduresDatabasesForms2D tablesFormulasMethodsObjectsVariables
Development system:
Class browser“Compiler”Interpreter / Debugger
User system:Class browserRun-time Interpreter
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Decision tablesAllow precise modelling of complex logic structures in a compact formatClear table structure replaces several nested “if-then-else” clausesConditions, rules and actions are coded as enteredStandardized in DIN 66241 (1979): “Decision tables for information exchange”A special case of decision tables are two-dimensional (2D) tables
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Decision tables
Conditions
Rules
Actions
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More examples
Decision table with priorization of machine selection
2D table for rolling cost factor assignment.
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Procedures
Allow semi-structured text programming of sentences, loops, arrays, etc.Syntax similar to Basic or Pascal without strict variable declarationCalls to other components (decision tables, formulas, other procedures) within the same object
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Procedures
Logical decision
Call decision table
Call formula
Comment line
String constant
Numeric constant
Reserved word
Variable (variant type)
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Databases
Allow access to structured data (material properties, standard tempers, etc.)Simple query structuresAdvanced queries with SQL server for accessing external databases
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Databases (example: material properties)
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Forms (input/output)
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Class browser (object tree)
Colapsed treestructure
Expanded treestructure
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Interpreter and debugger
Useful for test runs during program developmentOnce tested, a run-time version of the expert system can be “compiled”File extension is “.knb” (knowledge base)Users access expert system from a local or remote server through the run-time interpreter.
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Interpreter
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ResultsSystem programmed and maintaned by same experts. Realization time ca. 8 months10+ years in use, extended to other production sites running remotely on same Citrix serverReduction of personnel in job preparation, employes can be reoriented to other activitiesReduced lead timesIncreased product qualityMore precision in cost calculationXPS never forgets a single rule or procedure less quality claimsSuccesful experience in job preparation applied for another expert system: technical assistance of sales department.
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ConclusionsExpert systems allow efficient management of one of the company’s main assets: technical know-howProgramming tools are easy to learn. Expert and programmer tasks can be performed by the same personnel within the company, freeing IT resourcesKnowledge base can be accesed remotely and must be maintained regularly by the same programming teamLimitations in structured programming aren’t a drawback: they simplify documentation and maintenance.