CBR for Fault Analysis in DAME Max Ong University of Sheffield

Distributed Aircraft Maintenance Environment - DAME Overview Overview of presentation Introduction to Case-Based Reasoning (CBR) technology CBR for Fault Analysis –Maintenance Advisor –Grid Service Implementation –User interface to the Grid Service Related Work –MEAROS –CBR Workflow Advisor

Distributed Aircraft Maintenance Environment - DAME CBR is a mature, low-risk subfield of A.I. Primary knowledge source –a memory of stored cases recording specific prior episodes –not generalised rules New solutions generated by adapting relevant cases from memory to suit new situations Retrieve Propose Solution AdaptJustify Criticize Evaluate Store Case-Based Reasoning “Reasoning by remembering, reasoning is remembered.”

Distributed Aircraft Maintenance Environment - DAME What is a case? “A case is a contextualised piece of knowledge representing an experience that teaches a lesson fundamental to achieving the goals of the reasoner.” (Kolodner, 1993) Cases link together knowledge that belongs together: –Information concerning the fault –Response to the fault –Effects of those responses Description of situation Description of problem in that situation Description of how problem was addressed Results or outcome of addressing the problem in that way “CASE” Case-Based Reasoning

Distributed Aircraft Maintenance Environment - DAME Casebase Repository of fault cases Cases represent individual engine fault events and maintenance actions Knowledge Model Contains general knowledge about a specific field of application Comprises the data structure (data model), the relationship between values within the data (valuation models) and information for defining application- specific vocabulary in the data Valuation Model Defines the similarities and evaluations of individual pieces of data in relation to each other Facilitates knowledge-based, intelligent searches (directed search) CBR Knowledge

Distributed Aircraft Maintenance Environment - DAME CBR Tool Implements Nearest Neighbour (k-NN) algorithm CBR Search

Distributed Aircraft Maintenance Environment - DAME Inductive Retrieval –Induction - ID3 Algorithm –Knowledge-Guided Induction Example: 1. Discriminate by EPR CBR Induction

Distributed Aircraft Maintenance Environment - DAME CBR Maintenance Advisor:  Emulates the diagnostic skill of an experienced maintenance engineer  Provides the user with ‘best practice’ advice when confronted with a set of fault symptoms  Provides a confidence measure for each suggested solution  Facilitates the processing of logistic data, current and historical fault data to intelligently isolate an engine problem Some common misconceptions: xCBR is a relational database of engine faults xCBR is only a search engine CBR Maintenance Advisor

Distributed Aircraft Maintenance Environment - DAME Why the Grid?  Collaborative working environment (virtual organisation)  Distributed data  Interaction with other services  High performance computing (large casebase computation)  Scalability  Delivery via Grid Services with security CBR Maintenance Advisor

Distributed Aircraft Maintenance Environment - DAME CBR Maintenance Advisor Implementation l Import fault and maintenance data from SQL database l Creation of datatypes within CBR l Map fault information to Analysis and Valuation Model l Pre-indexed casebase, knowledge and valuation models are stored in XML

Distributed Aircraft Maintenance Environment - DAME CBR Maintenance Advisor Implementation CBR Maintenance Advisor - Grid Service Deployed as a service on the Grid with Globus 3 Toolkit Accessible by user via a web browser across the Internet Secure access with user and host authentication, SSL encryption. Access to fault information and knowledge gained from fault diagnosis processes Obtain maintenance advice in form of appropriate maintenance action

Distributed Aircraft Maintenance Environment - DAME ` CBR Maintenance Advisor Implementation

Distributed Aircraft Maintenance Environment - DAME CBR Maintenance Advisor Implementation

Distributed Aircraft Maintenance Environment - DAME CBR Maintenance Advisor Implementation

Distributed Aircraft Maintenance Environment - DAME Quick summary Case-Based Reasoning (CBR) technology CBR for Fault Analysis –“Maintenance Advisor” Service in DAME –Globus 3 Grid Service Implementation Related work –MEAROS –CBR Workflow Advisor

Distributed Aircraft Maintenance Environment - DAME MEAROS Modular Engine Arisings & Overhaul Simulation MOGA MEAROS Client MEAROS Module Failure Rate Data Distribute Solutions Collect Results Send Population of Solutions Receive Evaluation Results Multi-objective Optimisation with Genetic Algorithms : selection crossover mutation re-insertion Interprets the results from MEAROS using a costing model Provides a way of distributing solutions to MEAROS and collecting the results Stochastic model for the simulation of operation, maintenance and supply of gas turbine engines to fleets of aircraft The module failure rate data is used to improve the failure distributions for the components inside the model. Removal of aircraft engines is expensive, significant fraction of operating costs MEAROS enables ‘optimal’ preventative maintenance strategies to be determined MEAROS within virtual maintenance environment can enhance fleet management of aircraft and engines MEAROS simulation is a very compute-intensive process The Grid offers high-performance computing resources, enabling faster results and quicker decisions to facilitate maintenance planning