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Fault Tree AnalysisFault Tree Analysis
““Faultless to a fault.” - Robert BrowningFaultless to a fault.” - Robert Browning
Albert HsuAlbert Hsu
IntroductionIntroduction
Fault identification, correction and tolerance to Fault identification, correction and tolerance to improve designimprove design
Fault Tree AnalysisFault Tree Analysis “ “A method to decompose it and look for situation A method to decompose it and look for situation
that might lead to that might lead to failurefailure” (Software Engineering)” (Software Engineering) Displayed the logical path from effect to causeDisplayed the logical path from effect to cause
Fault Tree Analysis, Fall 2006
The Fault TreeThe Fault Tree
Begin Fault Analysis by identifying possible failures Begin Fault Analysis by identifying possible failures in design operation or maintenancein design operation or maintenance
Next build a graph whose nodes are failuresNext build a graph whose nodes are failures Single contentsSingle contents System functionSystem function Entire system Entire system
Edge = relationship among nodes by logical descriptor (AND,OR)
Fault Tree Analysis, Fall 2006
The Fault TreeThe Fault Tree
Figure 5.19 Portion of power plant control system
Fault Tree Analysis, Fall 2006
Cut-set TreeCut-set Tree
From Fault tree to cut-set treeFrom Fault tree to cut-set tree To find single points of failure in complex treeTo find single points of failure in complex tree
Figure 5.20 Cut-set tree generated form the fault tree
Fault Tree Analysis, Fall 2006
Fixing the FailureFixing the Failure
RemoveRemove it it
Add components or conditions toAdd components or conditions to preventprevent the the input condition that cause the fault to be input condition that cause the fault to be executedexecuted
Add components that will Add components that will recoverrecover from the from the damage the failure will causedamage the failure will cause
Fault Tree Analysis, Fall 2006
Some faults…Some faults…
Time-consuming in constructing the graphsTime-consuming in constructing the graphs
Many systems involve many dependenciesMany systems involve many dependencies Difficult to detect inconsistenciesDifficult to detect inconsistencies Difficult to focus only on the most critical parts of Difficult to focus only on the most critical parts of
the design on high coupling systemsthe design on high coupling systems
Not always easy to spotNot always easy to spot
Fault Tree Analysis, Fall 2006
ReferenceReference
Atlee, Joanne, Atlee, Joanne, Software Engineering Theory Software Engineering Theory and Practice, and Practice, Pearson Prentice Hall, New Pearson Prentice Hall, New Jersey, ©2006, pg264-266Jersey, ©2006, pg264-266
Fault Tree Analysis, Fall 2006
