1. Functional Decomposition
Design Project Management
Rochester Institute of Technology
Mechanical Engineering Department
Rochester, NY USA

2. 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!
They WILL care about how well you deliver the functions -> metrics and specifications

3. 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.

4. Navigate an individual from Point A to Point B, given A and B (start and end points) and information about the surrounding environment

5. Inputs and Outputs?
Flow through the system that is performing this function
Information
Matter
Energy

6. On Map?
Region Map
Navigate an individual from Point A to Point B, given A and B (start and end points) and information about the surrounding environment
Hardware Health
Nearest Tag ID(s)
Movement Instructions
Destination
ETA
Power
Heat
Information and Energy only for this
We’ve already made assumptions about the form of the design: RFID

7. 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?

8. Navigate an individual from Point A to Point B, given A and B (start and end points) and information about the surrounding environment
Identify current state
Identify target state
Determine Route
Transmit information to user
Support internal components

9. Identify current state On Map?
Region Map
Identify current state
On Map?
Transmit information to user
Nearest Tag ID(s)
Determine Route
Movement Instructions
Identify target state
Destination
ETA
Battery, MCU
Power
Hardware Health
Heat

10. How are you going to do THAT?
How are you going to identify current state?
Identify current location
Identify current orientation

11. Navigate an individual from Point A to Point B, given A and B (start and end points) and information about the surrounding environment
Identify Current State
Identify Current Location
Identify Current Orientation
Import Map
Identify Target State
Accept User Input
Determine Route
Calculate path
Calculate next movement instruction
Transmit Info to User
Convert movement instruction to tactile feedback
Support & Manage Internal Components
Support components
Maintain Temperature
Protect Components
Store Power
Accept Charging Power
Regulate Power

12. 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
Navigate an individual from Point A to Point B, given A and B (start and end points) and information about the surrounding environment
Identify Current State
Identify Current Location
Identify Current Orientation
Import Map
Identify Target State
Accept User Input
Determine Route
Calculate path
Calculate next movement instruction
Transmit Info to User
Convert movement instruction to tactile feedback
Support & Manage Internal Components
Support components
Maintain Temperature
Protect Components
Store Power
Accept Charging Power
Regulate Power
Ask “how”
Ask “why”

13. Movement Instructions
Receive Map Info
Compare current to map
Deliver Information to User
Region Map
On Map?
Record location history
Calculate Velocity
ID current location (RFID)
Calculate ETA
Nearest Tag ID(s)
ETA
Calculate path
Navigation Loop
Calculate next movement instruction
Movement Instructions
Receive User Input
Destination
Monitor Hardware Health
Hardware Health
Some arrows missing
Grey box was a way to mentally separate what was going to happen in software and what was going to happen in hardware
Determine Orientation (Compass)
Magnetic Field
(MCU: Define Interfaces with Power, User Input, Map Input, RFID Reader, Compass, Output Drive Circuitry)
Charging Power
Store on-board Power
Regulate Power
Heat
Enclosure: Support & Manage Internal Components

14. Information Energy Region Map On Map? Nearest Tag ID(s) ETA
Receive Map Info
Compare current to map
Deliver Information to User
Region Map
On Map?
Record location history
Calculate Velocity
Information
ID current location (RFID)
Calculate ETA
Nearest Tag ID(s)
ETA
Calculate path
Navigation Loop
Calculate next movement instruction
Movement Instructions
Receive User Input
Destination
Monitor Hardware Health
Hardware Health
Determine Orientation (Compass)
Magnetic Field
(MCU: Define Interfaces with Power, User Input, Map Input, RFID Reader, Compass, Output Drive Circuitry)
Charging Power
Store on-board Power
Regulate Power
Heat
Energy
Enclosure: Support & Manage Internal Components

15. 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

16. 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)

17. 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

18. 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

19. 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

20. 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?

21. Questions?

22. 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)

23. 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

25. Specifications: Metrics and Target Values
Design Project Management

26. When we left off… Functional decomposition
Function Tree
Flow Diagram
Each product development team should have a draft functional decomposition (or two, or three…) by now

27. 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?

28. 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 come up with these?

29. 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.
Can benchmark on individual functions, not just the whole product.

30. Example #1 ME Thermo/Fluids Demo Hardware: Integrate into classroom:
Integrate into classroom:
Perform demo within class period
Display results so that all students will be able to see
Transport easily between rooms
How can we measure these?
What targets should be set?
Give class a few minutes to consider these

31. Suggestions: Perform demo within class period
Minutes to complete demo (setup to completion)
50? 110? 75 (under semesters)?
Display results so that all students will be able to see
# students who can see results simultaneously
12 (T/F Lab)? 36 (small class)? 50 (large class)?
Direction? Source?

32. Suggestions (cont.) Transport easily between rooms
Size of containing volume, weight
How big a box can you carry?
How heavy a box can you carry?
Do you have a cart to use?
Who is “you”?
Is there a standard container you want to use as a limiting case?
“Complete setup can be transported in 18 gallon Rubbermaid bin #2215”
Direction? Sources?

33. Example #2 Arborloo toilet seat redesign Functions:
Functions:
Support (human) weight
Minimize odor
Withstand environment
Give class a few minutes…

34. Suggestions Support (human) weight Minimize odor # lbs (N?)
How much does the average person weigh?
The average person in Haiti?
Do you want to design for average?
Minimize odor
Stakeholder survey: % rating the odor acceptable
Proximity to Arborloo in order to smell
Direction for each? How to get this information?
Does the seat minimize odor, or does the extra organic material do that?

35. Suggestions (cont.) Withstand the environment
Wind gust that can be survived (mph, kph?)
Hurricane speed?
Sustained wind that can be survived
Hurricane speed? Tropical storm? Less?
Material removal per year (thickness? Volume? Satisfies a standard corrosion test requirement?)
Where do you find these? Do you want to drive them up or down?

36. Remainder of class 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?
Regroup at end, present results