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Fault Tree Based Diagnosis with Optimal Test Sequencing for Field Service EngineersWhen field service engineers go to customer sites to service equipment, they want to diagnose and repair failures quickly and cost effectively. Symptoms exhibited by failed equipment frequently suggest several possible causes which require different approaches to diagnosis. This can lead the engineer to follow several fruitless paths in the diagnostic process before they find the actual failure. To assist in this situation, we have developed the Fault Tree Diagnosis and Optimal Test Sequence (FTDOTS) software system that performs automated diagnosis and ranks diagnostic hypotheses based on failure probability and the time or cost required to isolate and repair each failure. FTDOTS first finds a set of possible failures that explain exhibited symptoms by using a fault tree reliability model as a diagnostic knowledge to rank the hypothesized failures based on how likely they are and how long it would take or how much it would cost to isolate and repair them. This ordering suggests an optimal sequence for the field service engineer to investigate the hypothesized failures in order to minimize the time or cost required to accomplish the repair task. Previously, field service personnel would arrive at the customer site and choose which components to investigate based on past experience and service manuals. Using FTDOTS running on a portable computer, they can now enter a set of symptoms and get a list of possible failures ordered in an optimal test sequence to help them in their decisions. If facilities are available, the field engineer can connect the portable computer to the malfunctioning device for automated data gathering. FTDOTS is currently being applied to field service of medical test equipment. The techniques are flexible enough to use for many different types of devices. If a fault tree model of the equipment and information about component failure probabilities and isolation times or costs are available, a diagnostic knowledge base for that device can be developed easily.
Document ID
20020014794
Acquisition Source
Ames Research Center
Document Type
Conference Paper
Authors
Iverson, David L.
(NASA Ames Research Center Moffett Field, CA United States)
George, Laurence L.
(Abbott Labs. Santa Clara, CA United States)
Patterson-Hine, F. A.
(NASA Ames Research Center Moffett Field, CA United States)
Lum, Henry, Jr.
Date Acquired
August 20, 2013
Publication Date
January 1, 1994
Subject Category
Quality Assurance And Reliability
Meeting Information
Meeting: Technology 2004
Location: Washington, DC
Country: United States
Start Date: November 8, 1994
End Date: November 10, 1994
Funding Number(s)
PROJECT: RTOP 233-03-05
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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