Principles of Engineering System Design Dr T Asokan

Developed by US Air force Answers definitive questions about the transformation of inputs to outputs Is a coordinated set of diagrams, using both a graphical language and natural language A-0 page is the context diagram A0,A1, A2,.. Level 0,1,2,.. diagrams IDEF0 ( Integrated Definition for Function Modeling)

A-0 page: Context or system function diagram. Defines inputs, controls, outputs, and mechanisms (ICOMs) for the single top- level function, labelled A0.( Contains A0) A0 Page: Level 0 diagrams with first tier functions specified  A1,A2,..: Level 1 diagrams with second tier functions specified.  A11,A12, …A21,A22…. : Level 2 diagrams with third tier functions

Functional Structure IDEF0- Example: Elevator NODE:TITLE:NUMBER: P. PROVIDE ELEVATOR SERVICES A0 Passenger Characteristics Electric Power & Emergency Communication Response Service, Tests & Repairs Request for Emergency Support & Emerency Message Request for Floor & Exit Support Request for Elevator Service & Entry support Structural Support, Alarm Signals & Building Environment ModifiedElevator Configuration & Expected Usage Patterns Passenger Environment Acknowledgment that Request Was Recieved & Status Information Diagnostic & Status Messages Elevator Entry/Exit Opportunity Emergency Support Emergency Communication Elevator System 2 Provide Elevator ServicesA-0

A2 Control elevator car

Evaluation of Functional Hierarchy: Scenario Tracing Shortfall: is the absence of a functionality that is required to produce a desired output. Absence of the proper functionality Inability to produce a desired output Insufficient control signals to produce O/P overlap: is a redundancy in functionality that is needed to achieve additional performance. Functional overlaps, unlike physical overlaps, are not needed

Evaluation of Functional Hierarchy: Scenario Tracing