1. Voice of the Engineer (VOE)
Function Trees
Fall

2. Functions (VERB NOUN pairs)
Start with ranked groups of needs
Create a list of functions that need to be accomplished to meet those needs
VERB NOUN pair (support load, apply torque, store data, etc.)
Does it need:
Power
Information
User interface
Supports
Enclosures

3. Step 1: Formulate – Identify Core Functions
Shopping carts
That leaves us with…
Function 1: Handle Products
Function 2: Transport Products

4. Step 2: Assume – Identify the subfunctions which Each Primary function must achieve
Next, identify the further details or subfunctions that the shopping cart needs to provide.
Focus on WHAT the shopping cart needs to do, in order to provide the functionality of each primary function.

5. Step 2: Assume – Identify the subfunctions which Each Primary function must achieve
Function 1: Handle Products
Support Products
Contain Products
Protect Products
Function 2: Transport Products
Translate products
Stop moving
Rotate products

6. Transport the Products
Step 3: Chart - Function Tree in Graphical Form Describe HOW you plan to meet your shopper’s need:
Design a device to enable a customer to collect products and easily move them through the store.
Handle Products.
Support Products
Contain Products
Protect Products
Transport the Products
Translate products
Stop moving
Rotate products

7. Step 4: Execute – Fill in the details of the function tree, (and articulate the interface specifications)
Performance Specifications will define what each of the top level subsystems must do for the customer.
Design Specifications will define how each of the top level subsystems will connect, or interface, with one another.
Typically, the customer worries, and cares, more about the performance specifications.
As engineers, we tend to focus, worry, and care more about the design specifications.
It’s important to make sure we always insure that our natural attention to the design interfaces does not detract our attention away from the customer’s needs, which are more accurately represented by the performance specifications.
We will look at interfaces next week in class.
Needs Assessment

8. Step 4: Execute – Fill in the details of the function tree, and articulate the interface specifications
Design a shopping cart.
Handle Products.
Support Products
Mass of product (kg)
Contain Products
Max volume of product (m3)
Min volume of product (m3)
Max surface area of product (m2)
Min surface area of product (m2)
Protect Products
Transport products without damage? (Y/N)
Transport the Products
Translate products
Force to initiate motion to # speed (N)
Stop moving
Force to stop moving from # speed in # sec (N)
Rotate products
Turning radius (rad)
Force to change direction (N)

9. Constraints
There might be other things that have to be met that are not functions
-cost limits
-production methods
These constraints can be listed alongside the functions

10. Step 5: Test
Engineering Judgment – Ask your mentor to punch some holes in your function tree, interface specifications, and complete understanding of the customer need. Invite them to be critical now – before you spend a lot of time solving the wrong problem!
Quality Review – Seek buy-in from
Your mentor and professor,
your clients, the students, instructors, robot users, etc.
The shop staff and others who will help you design & build
Insure that this function tree addresses all aspects of the mission statement and objective tree, and will result in a satisfied customer!
Concept Development

11. Functions interrelate
Flow of power (mechanical, electrical)
Flow of information (signals, sensors, actuators)
Flow of material (water, widgets)

12. Example

13. Functions (focus of brainstorming)
Brainstorming focuses on ways to achieve the functions

14. Brainstorm on
Shopping cart handle

15. Brainstorm on
Obtain direction information from user

16. Specifications Objective Can be measured
Practical (test costing $10,000 won’t work)
Need to be measured
Complete - Relate to the customer needs

17. Needs vs. Metrics
Metrics translate needs into objective things that can be measured.
“I need it to be light”
Product and battery but not charger must have a mass <= 1.5kg
This allows you to objectively see if a design meets the customer needs
One metric may meet more than a single need
House of Quality

18. Specifications cover all needs
“House of Quality”
Some needs are covered by more than one metric
Some metrics cover more than one need

19. House of Quality bicycle shock
From Ulrich and Eppinger

20. Metrics also can protect you
What if the customer is unhappy with the thing you produce which meets all the specifications (list of metrics)

21. Non-standard metrics “The system needs 3 different diameter wheels”
Yes/no
Spread in diameters
“The product must instill pride in the user”
Subjective
Focus groups/ surveys

22. Caution! Try not to spec. your project so that:
It is impossible (no solutions)
It requires costly exotic materials (unless needed)
There is only a single solution
It requires too much time to analyze or build
It requires fabrication processes that we don’t have access to
It is exceedingly dangerous or risky
It is not challenge at all
It’s ok to have 1 or 2 “reach” specs but not all of them
Specifications can drastically change the outcome

23. Simple initial hand calculations
It’s very easy to set up an “impossible” set of metrics to be met
Weight: < 0.01 g
Volume: > 10 m^3
Load carrying capacity: > 10 kN
Engineering analysis will help you determine a reasonable set of specifications

24. Exercise
Mass of shopping cart: < 2 kg
Is this a reasonable spec?

25. Shopping cart initial analysis
Load bearing capacity
Mass of cart
Frictional losses
Power consumption
Refueling times
Cost
Can you come up with a design that you can show will meet the specifications you list?

26. Negotiation What if you agree to meet an impossible specification?
How do you deal with creeping elegance?
What is creeping elegance?
Types of customers that you may have to manage.

27. Next week
Continue specifications