R. I. T Mechanical Engineering Functional Decomposition Design Project Management Rochester Institute of Technology Mechanical Engineering Department Rochester,

R . I . TMechanical Engineering

Functional Decomposition

Design Project Management

Rochester Institute of TechnologyMechanical Engineering Department

Rochester, NY USA


Purpose of the functional decomposition:• Identify a small number of functions (the WHAT) that your

product must deliver to the customer to satisfy their need (the WHY)

• Prepare to map those functions back to customer needs.

• As long as you provide the correct “WHAT” to your customer, they will often not care “HOW” you deliver the functions.

• Modularize the product

• Provide a structure around which to specify the problem

• Provide a structure around which to brainstorm

• We will try two different approaches today – both may have value for your team!


What is the core function?

• What is the one core function that the device/product/process needs to accomplish?

• What subfunctions need to be performed in order to achieve that function?• This allows you to begin distinguishing your

problem/solution from others.


Navigate an individual from Point A to Point B, given A and B (start and end points) and information

about the surrounding environment


Inputs and Outputs?

• Flow through the system that is performing this function• Information• Matter• Energy




Region Map

Nearest Tag ID(s)

Destination

Power

On Map?

Hardware Health

Movement Instructions

ETA

Heat


How are you going to perform that function?

• Verb-Noun

• Examples:• Identify current location/state• Identify destination• Determine route

• How is that information, matter, or energy being transformed or moved through the system?




Identify current state

Identify target state

Determine Route

Transmit information

to user

Support internal

components


Region Map

Nearest Tag ID(s)

Destination

Power

On Map?

Hardware Health


ETA

Identify current state

Identify target state

Determine Route

Transmit information

to user

Heat

Battery, MCU


How are you going to do THAT?

• How are you going to identify current state?• Identify current location• Identify current orientation



Or: Brainstorm a list of tasks, then sort

• Sort tasks into hierarchical order

• Ask how you will complete each task

• Ask why you must complete each task

Ask “how”

Ask “why”


Region Map

Nearest Tag ID(s)

Destination

Charging Power

On Map?

Hardware Health


ETA

Receive Map Info

Record location history

Regulate Power

Enclosure: Support & Manage Internal Components

Receive User Input

Calculate path

Determine Orientation (Compass)

ID current location (RFID)

Compare current to map

Calculate next movement instruction

Calculate Velocity

Calculate ETA

Monitor Hardware Health

(MCU: Define Interfaces with Power, User Input,

Map Input, RFID Reader, Compass, Output Drive

Circuitry)Store on-

board Power

Navigation Loop

Heat

Magnetic Field


Region Map

Nearest Tag ID(s)

Destination

Charging Power

On Map?

Hardware Health


ETA

Receive Map Info


Regulate Power


Receive User Input

Calculate path





Calculate Velocity

Calculate ETA




Circuitry)Store on-

board Power

Navigation Loop

HeatEnergy

Information

Magnetic Field


Consider last week’s example…

• I said, “We need a better ladder”.

• What if I had said, “We need a device that provides access to objects above human reach”?• Core fuction: Provide access to objects above

human reach.• Define problem further in the subfunctions


Point of Confusion #1• Functions ≠ Constraints

• Constraints are system-wide parameters, like cost, weight, overall footprint

• Functions are actions, what your device/system will do (verb-noun)


Point of Confusion #2

• Engineering Metrics and Target Specifications define how well you need to perform these functions/subfunctions, or what constraints you must meet• Metrics = what to measure, units• Specifications = magnitude• Consider specifications for minimally acceptable,

target, and ideal conditions


Examples of Functions• Some functions that your product may perform

(from Otto & Wood Product Design):• Import, export, transfer, transmit, guide, translate,

rotate, allow degrees of freedom

• Stop, stabilize, secure, position

• Couple, mix, separate, remove, refine, distribute, dissipate

• Store, supply, extract

• Actuate, regulate, change, form, condition

• Sense, indicate, display, measure


In-Class Example

• Develop a functional decomposition for a device that will enable a person with one hand to secure their hair in a ponytail.

• R13002, R13201, and R13301 use function tree/FAST diagram

• R13401, R13701, and R13904 use flow diagram


Regroup

• Two teams share function trees

• Discussion:• How are these different from yours?• Is one right or wrong? Better or worse?• Are you (or they) missing functions?• Are you (or they) prescribing solutions?• Other questions?


Questions?


Rest of Today…

• Refine VOC, problem background• Feedback from guide• Follow-up with stakeholders

• Prepare for next week’s presentation• What information do you want to convey?• What information are you still missing?

• Begin considering core function(s) for your project(s)


Next Steps

• Assign metrics and specifications• Metrics = what to measure, units• Specifications = magnitude• Consider specifications for minimally acceptable,

target, and ideal conditions

• Performance Specifications: what the customer sees

• Design Specifications: define interfaces



Specifications:Metrics and Target Values



When we left off…

• Functional decomposition• Function Tree• Flow Diagram

• Each product development team should have a draft functional decomposition by now


Context

• Objective Tree: What the customer needs

• Function Tree: How the overall project goal will be achieved

• Specifications: How well do the functions need to be performed?


Metrics and Specifications

• Indicate units of measure (metrics)

• Indicate preferred direction• Up, maximize• Down, minimize• Target value• Range or list of values• Binary• Survey results

• Min. acceptable, target, and ideal values


How do we define specifications?

• Benchmarks• You should already have identified some benchmark

products

• Analysis• You should already have identified relevant

governing equations, course material, etc.

• Stakeholder requirements• Business goals, must interface with existing system,

stakeholder characteristic, etc.


Example #1: RC Camera Car


How will you measure a “good job”?

Function Metric (s)

Convert input to wireless

Transmit control signal to car

Convert signal to mechanical response

Power components

Protect components



Function Metric [direction]

Convert input to wireless Delay time (msec)

Transmit control signal to car Transmit range (m), transmit rate (bytes/sec)

Convert signal to mechanical response Delay time (msec), sensitivity (deg/deg, N/N, ...)

Power components Voltage (V), current (A), time between charges (h)

Protect car components Max collision speed (m/s)

Protect console components Max drop height (m)

Metrics


What is the “good job” threshold?

• Ideal• Reach goal

• Target• What you can reasonably expect to achieve

• Marginal• Performance barely acceptable to customer

Specifications



Function Metric [direction] Target Marginal

Convert input to wireless Delay time (msec) [↓]


Transmit range (m) [↑]transmit rate (bytes/sec) [↑]


Delay time (msec) [↓]sensitivity (deg/deg, N/N, ...)

Power components Voltage (V), current (A)time between charges (h) [↑]

Protect car components Max collision speed (m/s) [↑]

Protect console components

Max drop height (m) [↑]



Function Metric [direction] Target Marginal

Convert input to wireless Delay time (msec) [↓]


Transmit range (m) [↑]transmit rate (bytes/sec) [↑]

30 m1500 kbps

10 m500 kbps


Delay time (msec) [↓]sensitivity (deg/deg, N/N, ...)

Power components Voltage (V), current (A)time between charges (h) [↑]

Protect car components Max collision speed (m/s) [↑]

Protect console components

Max drop height (m) [↑] 1 m 0.1 m

Specifications


How to define values for specs?

• Benchmark products (by function)

• Spec sheets

• Customer criteria

• Basic feasibility analysis

• Remember: there may be dependency between specs! Learn more when we cover House of Quality


Reflect on the Process

• Do the results make sense?

• Are all the functions/specs appropriate?• Are you willing/able to do the test to get the

measurement (e.g., destructive testing, infinite life testing)?

• Have all the functions been captured?• Is there an expected performance metric that doesn’t

show up? Could mean you missed a function!


Remainder of hour (if time)

• For each of your functions, determine:• Metric(s)• Source for target value (observation, measurement,

analysis, research, benchmark, etc.)• Direction you want to drive the value (up, down,

target, etc.• Is the function appropriate?


Brainstorming



Why?

• How often is the first idea to come to mind the best possible solution?

• Are you looking for incremental improvements or significant change?


When?

• After you’ve decomposed your problem into a series of functions• Manageable pieces• Easy to brainstorm ways to perform a single function

• When creative ideas are sought• This is NOT always the case• Ask yourself, “Does it make sense?”

• Example: Navigation Aid for Blind User


Region Map

Nearest Tag ID(s)

Destination

Charging Power

On Map?

Hardware Health


ETA

Receive Map Info


Regulate Power


Receive User Input

Calculate path





Calculate Velocity

Calculate ETA




Circuitry)Store on-

board Power

Navigation Loop

Heat

Magnetic Field


Region Map

Nearest Tag ID(s)

Destination

Charging Power

On Map?

Hardware Health


ETA

Receive Map Info


Regulate Power

Receive User Input

Calculate path





Calculate Velocity

Calculate ETA




Circuitry)Store on-

board Power

Navigation Loop

Heat

Magnetic Field


Pre-defined solution, or

heavily constrained


Region Map

Nearest Tag ID(s)

Destination

Charging Power

On Map?

Hardware Health


ETA

Receive Map Info


Regulate Power

Receive User Input

Calculate path





Calculate Velocity

Calculate ETA




Circuitry)Store on-

board Power

Navigation Loop

Heat

Magnetic Field



heavily constrained

Limited opportunities for creative problem

solving


Region Map

Nearest Tag ID(s)

Destination

Charging Power

On Map?

Hardware Health


ETA

Receive Map Info


Regulate Power

Receive User Input

Calculate path





Calculate Velocity

Calculate ETA




Circuitry)Store on-

board Power

Navigation Loop

Heat

Magnetic Field



heavily constrained

Limited opportunities for creative problem

solving

Good opportunity to seek creative

solutions


Approaches & Tools

• Many!

• Some example from Otto & Wood Product Design:• Mind Maps• 6-3-5 method• Analogies• Separate by physical principles


Rules (IDEO)

IDEO video: http://youtu.be/M66ZU2PCIcM


6-3-5 Method

• Teams sit in circles• Each team member draws or writes down 3 ideas on a

piece of paper (3 minutes)• Pass paper to the left• For 1 minute, make comments, additions, sketches on

the paper in front of you• Repeat 4 more times (5 turns, total)


Analogies

• Identify an element of nature that performs a function analogous to the one you are charged with.

• Develop concept(s) based on those elements of nature.


• For each function, consider the physical principles that could govern it. For example, you can store energy in several different ways (example from Otto & Wood):

• Mechanical

• Electrical

• Chemical

Search by Physical Principles


Example #2: PMTR


Example: Solution-Independent!

User actuation Convert input to

displacement

Type of test (F or d control)

Test sample Accept test

sampleSecure test

sample

Measure Force

Measure displacement

Deformed sample

Force value

Displacement value

Apply displacement to

sample

Disclaimer: not a perfect functional decomposition, but a step toward solution-independence!


Brainstorm

User actuation Convert input to

displacement

Type of test (F or d control)

Test sample Accept test

sampleSecure test

sample

Measure Force

Measure displacement

Deformed sample

Force value

Displacement value

Apply displacement to

sample


Take 15 minutes

• Boeing, Library: Physical principle

• Assistive Technology, AQM: 6-3-5

• Test Rigs, Student-Initiated: Analogy


Discussion, questions?

• R13002: 61 ideas/6 people• R13201: 52 ideas/8 people• R13301: 25 ideas/5 people• R13401: 49 ideas/9 people• R13701: 44 ideas/6 people• R13904: 38 ideas/3 people (12.6 ideas/team member)

Documents

R. I. T Mechanical Engineering Functional Decomposition Design Project Management Rochester Institute of Technology Mechanical Engineering Department Rochester,