Functional Analysis - Applying Systems Engineering - Lecture Slides, Slides of Systems Engineering

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Functional Analysis

Objectives

• Discuss key terminology
• Define functions and functional analysis
• Describe functional decomposition process
• Describe requirements allocation
• Describe interface development
• Define the functional analysis products

Mission Analysis / Requirements Analysis

Alternatives Analysis /System Synthesis

System Verification

IntegrationSystem

Systems Engineering Planning

TradeoffStudies

Baseline Management

Functional Analysis

Functional Hierarchy

Functional System Architecture

Objectives:

 Identify system functionality in generic terms

 Validate completeness of functional system description

Where are We in the

SE Process?

Key Terminology;

Terms we should know

• Allocation Matrix
• Allocation of Requirements
• Child Functions
• Decomposition
• External Interface
• Flow Connection
• Function Block
• Function Numbering
• Functional Analysis
  • Functional Flow Block

Diagram (FFBD)

• Functional Hierarchy

Diagrams

• Functions
• “How” Functions
• Internal Interface
• N-squared Diagram
• Parent Function
• “What” Functions

Functions and Functional

Analysis (cont.)

 Functional analysis draws out any

additional requirements the system must

meet to represent a complete system.

 Following synthesis, functional analysis

identifies all “how” functions necessary to

implement the synthesized solution.

Functional Analysis Activities

• Decomposition
• Allocation of Requirements
• Interface Identification

System Thinkers

Program Management

Subject Matter Experts

Customer

Functional Analysis Activities

It’s a

Team effort

Project to Provide a Home

(This is the Mission Plan)

Provide a newly constructed single family home ready for occupancy on a

Landscaped lot in a plotted subdivision in Idaho Falls within a one year

Period for a cost not to exceed $300 K.

The house floor plan shall contain approximately 2500 square foot above

Ground level with the floor plan arrangement approved by the prospective

owner. The house shall include a minimum of 4 bedrooms, 2 baths, a formal

dinning area, living room, family room, and a 3-car garage. The house design

shall comply with the Good Sense Standard.

The lot shall have a minimum of 12,000 square feet with the surrounding homes

of comparable or larger size. Natural gas shall be available to the lot.

The landscaping shall include trees, low shrubs, and grass arranged over the

Complete lot area with some area available for planting annual plants. The

landscaping design shall blend with the layout of the house on the lot and the

adjacent properties. A minimum of 75% of the lot area (minus the house and

driveway footprint) shall be in grass. The lot shall be watered by an automatic

underground sprinkler system.

Provide a home

Alternatives Analysis and System Synthesis

What must

be done

How it

will be done Pour foundation Construct wood frame

Produce house and lot

Provide house on lot

Developing

System Functions

Landscape lot

Decomposition

Hierarchical and Functional

• Hierarchical Decomposition breaks down the

system from the highest to the lowest

hierarchical level

• Functional Decomposition breaks down the

system in terms of what the system must do

(i.e., the functions it must perform)

Functional Decomposition is just a type of

Hierarchical Decomposition

The element

Basic elements

or

components

Parent element

Child elements

Child element Child element

Child element

Basic elements

or

components

Parent element

Decomposition —

Hierarchical Representation

Example of a Multi-level FFBD

Provide a Home

Accompany inspector

Call for final inspection Note problems Fix problems^ Re-inspect

Obtain occupancy or permit

Select house

Obtain build ready lot

Arrange financing

Provide house on lot

Landscape lot

Manage work

Obtain occupancy permit and

Second Level - Obtain Occupancy Permit

Completed home on lot

Completed house Permit

First Level - Provide a Home

System Requirement Set Project End Objective

Example of a Multi-level FFBD

Provide a Home

Development of the

System Solution Concept

Functional Architecture

Functions necessary to produce the solution

Functions necessary to disposition the system assets

System Requirements Set

Functionality of the solution concept

Functions necessary to operate system elements

Extract functional requirements from system requirements set

System requirements set and Mission Objectives Statement

Arrange in logical grouping/order

• Use primary functions as guidance
• Reflect customer imposed WBS

Add missing functions

• Include all appropriate life-cycle functions

Assure child functions fully accomplish parent

• A hierarchical arrangement best supports this assessment

Propose additional system level requirements where appropriate

Re-cycle through requirements analysis

• Add needed system level requirements
• Develop/document derived requirements

Document results in System Description Document (SDD)

Add functions to system technical baseline

Reconcile function set with program/project work breakdown structure (WBS)

Represent all required physical systems by its functional architecture

• Perform necessary analysis to support functional development

Create appropriate function(s)

Functional Decomposition Process

Stop and Review—Functions

(True or False)

• A function is a verb initiated statement
• All necessary Functions to accomplish the system level

requirements must be represented in the functional hierarchy

• Functions not required to accomplish a system level requirement

are not necessary and must be eliminated.

• The resulting functions represent the “who” needs to satisfy the

system level requirements

• The “how” functions will result from the Alternatives Development,

Analysis, and Synthesis activities and are added to the set of

functions as developed