“Faultless to a fault.” - Robert Browning Albert Hsu Fault Tree Analysis “Faultless to a fault.” - Robert Browning Albert Hsu

Introduction Fault identification, correction and tolerance to improve design Fault Tree Analysis “A method to decompose it and look for situation that might lead to failure” (Software Engineering) Displayed the logical path from effect to cause Fault Tree Analysis, Fall 2006

The Fault Tree Begin Fault Analysis by identifying possible failures in design operation or maintenance Next build a graph whose nodes are failures Single contents System function Entire system Edge = relationship among nodes by logical descriptor (AND,OR) Fault Tree Analysis, Fall 2006

The Fault Tree Figure 5.19 Portion of power plant control system Fault Tree Analysis, Fall 2006

Cut-set Tree From Fault tree to cut-set tree To 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 Failure Remove it Add components or conditions to prevent the input condition that cause the fault to be executed Add components that will recover from the damage the failure will cause Fault Tree Analysis, Fall 2006

Some faults… Time-consuming in constructing the graphs Many systems involve many dependencies Difficult to detect inconsistencies Difficult to focus only on the most critical parts of the design on high coupling systems Not always easy to spot Fault Tree Analysis, Fall 2006

Reference Atlee, Joanne, Software Engineering Theory and Practice, Pearson Prentice Hall, New Jersey, ©2006, pg264-266 Fault Tree Analysis, Fall 2006