Name: ______________________________
EE411 Lesson 3:
Concept Generation & Evaluation
This lesson assumes that you have completed KPR 3.
Concept Generation


Enhancing Creativity
o Certain types of puzzles are known to enhance creativity.
 http://www.thecourse.us/students/lateral_thinking.htm
o Allow time for brainstorming
o Use your background research and apply SCAMPER (Substitute Combine Adapt Modify Putto-other-use Eliminate Rearrange)
o Make curiosity a habit. The more you know about other things, the more fodder you have
for new ideas.
Team Brainstorming Methods
o 5 Basic Rules for Brainstorming
 Suspend criticism or judgment
 Wild ideas are encouraged
 Quantity over quality
 Build upon and modify the ideas of others
 All ideas are recorded
o The Nominal Group Technique (NGT)
1. The leader/facilitator should read the problem statement out loud.
2. Each member should restate the problem in his/her own words and the group
should discuss any differences. This is to make sure that everyone in the group fully
understands and agrees on the problem.
3. As individuals, silently generate and record ideas.
4. Collect ideas in a round-robin fashion. Each person presents one idea at a time until
all ideas are exhausted. The facilitator should clarify ideas and record them where
all can view them.
5. The facilitator then leads a discussion to clarify and rephrase ideas. Similar ideas
should be grouped or combined.
6. The group should then prioritize ideas to explore, either by vote or consensus. The
outcome is a set of prioritized ideas to further discuss and pursue.
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A common brainstorming technique for engineering systems is to break down the system into its functions
or characteristics, and then to brainstorm ways to achieve each function or characteristic. There are 2
tools particularly mentioned by the text that you might find useful for your project:

Concept tables— The column headings represent functions or characteristics of the system, and
the items beneath them are options for achieving that characteristic or function. Here’s the
example from the KPR again:
Pet Incentive
Ball
Squeaker
Treat
Mechanical rabbit
Exercise Mechanism
Swim current
Treadmill
Exercise wheel
Pulling weight
Ball Chase
Track
Power
AC Power
Battery
Dog powered
Solar power
Operation Location
Indoors
Outdoors
Portable
Note that rows have no correlation (the mechanical rabbit isn’t particularly associated with “pulling weight” or
“solar power”). After discussion, the group would then circle the idea(s) to try to combine in a design to
represent options for further consideration. For example, this might represent one option:
Pet Incentive
Ball
Squeaker
Treat
Mechanical rabbit
Power
Operation Location
AC Power
Battery
Dog powered
Solar power
Indoors
Outdoors
Portable
Exercise Mechanism
Power
Operation Location
Swim current
Treadmill
Exercise wheel
Pulling weight
Ball Chase
Track
AC Power
Battery
Dog powered
Solar power
Indoors
Outdoors
Portable
Exercise Mechanism
Swim current
Treadmill
Exercise wheel
Pulling weight
Ball Chase
Track
And this would represent another:
Pet Incentive
Ball
Squeaker
Treat
Mechanical rabbit

Concept Fans or Function-Means Trees
A related tool is the “concept fan,” (aka “function-means tree”) which is particularly good for decomposing
systems with hierarchical design decisions. In these charts, circles represent functions or characteristics of
the system, and rectangles represent means. (This is slightly different from what our textbook says—the truth
is that the shape isn’t critical--- whether it’s a function of a means is usually clear from context). Here is the
start for a concept fan for a smart phone biometric ID app:
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Droid
Platform
iPhone
Near IR
Spectrum
Visible
Iris
Take Picture
RED
Algorithm
Biometric
App
Neural Network
Biometric
Capacitance
Read print
Optical
Fingerprint
Image correlation
Voice
User
Interface
Matching
algorithm
Phase matching
Keyboard
Minutiae matching
Don’t marry your first design idea. Keep an open mind and try to come up with several different ideas
before you move on to the concept evaluation stage of design.
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Concept Evaluation



Every design decision point needs to be justified.
Initial evaluation
o Don’t rush to prune the design space.
o Discard only those concepts that are completely unfeasible.
Strengths and weaknesses analysis
o A simple chart of strengths and weaknesses between approaches
o Useful when comparing apples and oranges
o Example: NIR vs. visible spectrum for iris recognition:
Spectrum
NIR
Strengths
Weaknesses
 Potentially covert
 Can’t use phone camera
 Could be done in the dark
with a peripheral light source
 Can use phone’s camera
 Dependent on ambient
lighting or built-in flash
 Better established—
freeware more readily
available
Visible
Decision matrices
o A more analytical approach—particularly appropriate for choosing between similar options.
o Can be applied at the “micro” scale or the “macro” scale
o To establish scoring system, need to consider the performance sweet spot:
Point of
diminishing
returns. Set to 100
Benefit

Minimum for
consideration. Set
to 0 on metric.
Quality
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o Example: battery choice for a small robot
 Requires: >5 V & ~100 mA
 Objectives: low cost, low weight, long life
 Relevant engineering requirements:
 “Total system should weigh less than 1 kg”
 “Total system should cost less than $200”
 “Battery life should be > 5 h”
 Statistics for the options (assuming rechargeable batteries):
Battery Voltage Capacity/ Weight/ Cost/
Necessary
Tot.
battery
battery
battery Config.
Weight
AAA
1.5 V
850 mAh
13 g
$2.75
4 batteries
in series
AA
1.5 V
2500 mAh 30 g
$4.40
4 batteries
in series
C
1.5 V
4500 mAh 50 g
$6.79
4 batteries
in series
D
1.5 V
9000 mAh 80 g
$11.79 4 batteries
in series
9V
9V
250 mAh
42 g
$10.88 2 batteries
in parallel*
*2 in parallel needed to make minimal lifetime from requirements
Tot.
Cost
Tot.
Life
1) Determining weightings for objectives
Light
Low Cost
Long Life
Light
1
Low Cost
1/5
1
Long Life
1/3
3
1
2) Establish metrics for each objective
Light?
Weight
Score
Range
>500 g
0
<50 g
Would be half of total system allotted weight. Even though
we expect the batteries to be a significant part of the system
weight, we still need to leave room for other components.
Would be < 5% of total system allotted weight--- negligible
to total weight
Interpolates between min and max scores with straight line.
100
AAA
weight
Justification
50-500g
Option
“Light” Score
avg
AA
C
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D
9V
Long Life?
 Could use similar model but upper limit harder to define since battery lifetime directly determines
system lifetime.
 Alternate model (particularly if there is no upper limit to a desired quantity)—score options relative to
“Best in Class”
 However, this also assumes that you’ve included all of the realistic options.
Option
Lifetime
Lifetime/Best
Lifetime
AAA
AA
C
D
9V
Low cost?
 A similar system is used for rating cost relative to best in class, except it needs to be flipped so that low
cost = high score.
Option
Cost
Best Cost/Cost
AAA
AA
C
D
9V
3) Score the options.
AAA
The Decision Matrix
AA
C
D
9V
Light
Low Cost
Long Life
Score
4) Review




___ is the winner—largely based on cost and despite relatively short lifetime.
Does the result feel right?
Cost played a big role, such that even though long life was prioritized above weight, one of the shortest
lifetime options was chosen. Is that okay with the customer?
Are there other options that should have been considered? For example, would there be a benefit to
looking at adding more batteries in parallel to boost lifetime (at expense of cost and weight)?
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Pugh concept selection
A more qualitative method for comparing concepts—better for apples & oranges than the decision matrix.
1.
2.
3.
4.
5.
Generate lots of concepts.
Choose the one that looks best to the group—set as baseline.
Rank other concepts against it (+1 = better, 0 = equal, -1 = worse)
Compute weighted scores for other concepts.
Use results to generate a new concept set and repeat until the superior concept is clear
Example: pet exercise eq.
Baseline: Existing treadmill modification with sidewalls for safety and treat dispenser
Option 2: Ball shooter that dispenses treat upon ball return
Option 3: Outdoor track with electric, erratically moving, squeaking rabbit
Option 4: Doggie TRX with squeaking lure and treat reward
Great Dane appeal
Capability for
autonomy
Canine energy
dissipation
Cost
Space it takes up
Score
3
2
2
3
2
Baseline
Concept
---
Option 2
----
Option 3
Option 4
0
+1
0
+1
+1
+1
-1
+1
-1
+1
+1
-1
-1
+1
+1
Based on these results, a new set of options would be considered:



Is there a way to make the track more consumer friendly?
What could we do with the Doggie TRX and ball shooter options to increase dane appeal or energy
dissipation?
Is there a way to make the treadmill autonomous
New Baseline: TRX with erratically moving, squeaking rabbit lure & treat dispenser
Option 2: Ball shooter that launches squeaking rabbit
Option 3: Squeaking rabbit robot that runs around house—track idea without the track.
Option 4: Treadmill that can sense dog’s presence and position, and autostart and stop
Then you would do a new chart for this and continue until a clear idea emerges…
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