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By the end of this chapter, you should: Understand the importance of creativity,

innovation, concept generation, and critical evaluation in engineering design.

Be familiar with barriers that hinder creativity. Be able to apply strategies and formal

methods to generate concepts. Be able to apply techniques for the evaluation

of design concepts.

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Perceptual blocksPrevent people from clearly seeing the problem

for what it is. A common perceptual block is the tendency to delimit the problem space.

A tendency to stereotype or see a solution to a problem that one is biased to see. For example, if you used a microcontroller to solve a type of problem, chances are you are going to consider using a microcontroller in a related problem.

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Perceptual blocks

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Emotional blocksOne of the most common emotional blocks is the

fear to failure. It is a cliché to hear that you must fail often to succeed, but true.

Another emotional block is the tendency to critically judge ideas, rather than generate and build upon them.

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Environmental blocksRefer to those things in our environment that limit

creative ability. This could be in the form of poor teamwork where members distrust each other and criticize each other’s ideas.

There are also cultural biases against creativity.

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Intellectual and Expressive blocksThe designed needs to have an understanding of

intellectual tools that are applied to solve problems. Examples in digital design are truth tables Refer to those things in our environment that limit creative ability. This could be in the form of poor teamwork where members distrust each other and criticize each other’s ideas.

There are also cultural biases against creativity.

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Have a questioning attitudeOne of the key is to have a questioning attitude

and challenge assumptions. Asking basic questions stimulates creativity and is applicable to technical designs.

Practice being creativeResearch shows that people can improve their

creative ability through conscious effort.

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Suspend judgmentIt is easy to criticize and immediately dismiss

ideas, so it is important do defer judgment and be flexible in thinking.

Allow timeThe creative process needs time for incubation.

The human mind needs time to work on problems, so set aside time to reflect on the problem.

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Think like a beginnerNew solutions often come from novices. The

reason is that novices don’t have preconceived ides as to the solution of the problem.

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External searching• Literature search• Review of existing patents• Interview with experts• Benchmark similar products

Internal searchingUse the well-known method of brainstorming

• No criticism or judgment on ideas• Quantity is stressed of quality• All ideas are recorded

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Thermal Sensing Conversion to Voltage

Display

Thermistor Op Amp Design Seven-Segment LEDs

RTD Transistor Designs

LCD

Thermocouple Analog Dial Indicator

A concept table is a tool for identifying different combinations, arrangements, and substitutions. In this example, the table implies a three-stage architecture

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Another tool is the concept fan, which is a graphical representation of design decisions and choices. The decisions are identified by circles; solutions are indicated by squares

RTD

Sensor

Thermo-couple

Therm-istor

WasherType

WireTube andWire

Temp toVoltage

Conversion

Op Amp

InvertingNon-Inverting

Transistor

SingleTransis-

tor

CurrentMirror

Display

7Segment

LEDLCDAnalog

Dial

LED BarLevel

Indicator

Design

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The concepts generated are evaluated to determine which are the most promising to pursue.

Initial EvaluationThe concepts generated should be initially reviewed and those that are completely infeasible should be discarded.

Strengths and Weaknesses AnalysisThis method is good for examining problems of moderate complexity. It suffers in that it does not require uniform criteria for comparison.

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Analytical Hierarchy Process and Decision MatricesIn this method, design alternatives are compared against preselected criteria, such as the engineering or marketing requirements.

Step 1. Determine the Selection CriteriaStep 2. Determine the Criteria WeightingsStep 3. Identify and Rate Alternatives Relative to the Criteria.Step 4. Compute Scores for the Alternatives

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∑=

=m

iiiS

111 αω∑

=

=m

iiiS

122 αω∑

=

=m

iininS

1αω

Design Option 1 Design Option 2 Design Option n

Criteria 1 α11 α12 α1n

Criteria 2 α21 α22 α2n

Criteria m αm1 αm2 αmn

Score

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Assume that the criteria for comparing the concepts are:

High accuracyLow costSmall sizeAvailability

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Accuracy Cost Size Availability Weights

Accuracy 1 5 3 1/4 0.42

Cost 1/5 1 2 1/4 0.12

Size 1/3 1/2 1 1 0.12

Availability 4 4 1 1 0.34

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Select a current source circuit for current measurement. Each circuit supplies a current I = 1mA, and a VT that varies with temperature.

◦ Single Transistor Inverting Op Amp Current Mirror

RTDRREF

VCC

+VT-

I

RTD

RE

-VEE

VCC

+VT-

IV

+

-

RTD

R

+ VT -

I

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The accuracy of each design was evaluated by a sensitivity analysis, using a SPICE circuit simulation package assuming 10% resistors. The deviation of the output voltage for the 3 designs is 9.2%, 1.3% and 1.9%.

The objective is to minimize the deviationα=min{deviation}/deviation

This produces the normalized design ratings for accuracy:

α11=0.08, α12=0.55, α13=0.37

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The part costs are the following:Resistors =$0.05BJTs=$0.15Op amps=40.35RTDs=$0.25

Using a measure of cost similar to the used for the accuracy. This produces the following normalized cost ratings:

α21=0.49, α22=0.21, α23=0.29

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Assume that to manufacture each circuit on a printed circuit board requires the following dimensions:Design 1: 1 in2

Design 2: 1.56 in2

Design 3: 2.25 in2

The objective is to minimize size, so we need to used again a similar measure for size. This produces the following normalized size ratings:

α31=0.48, α32=0.30, α33=0.21

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Assume that part are available 95%, 70%, 90%, and 80% of the time for resistors, BJTs, RTDs, and Op Amps respectively.

The probability that a design will be available to be manufactured on the basis of part availability.

P(design 1 can be produced)=(.95)(.90)(.70)=.60P(design 2 can be produced)=(.95)(.90)(.80)=.68P(design 3 can be produced)=(.95)(.90)(.70)(.70)=.42

This produces the following normalized decision ratings:

α31=0.35, α32=0.40, α33=0.25

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Single BJT Op Amp Current Mirror

Accuracy 0.42 0.08 0.55 0.37

Cost 0.12 0.41 0.28 0.31

Size 0.12 0.48 0.31 0.21

Availability 0.34 0.35 0.40 0.25

Score 0.26 0.44 0.30

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Remember that this is a semiquantitative method. The final ranking indicates that design options 1 and 3 are quite similar, while both are inferior to option 2.

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The following advice is provided for teams in the concept generation and evaluation phase:

Set aside time specifically for concept generation and evaluation.

Search externally, including literature reviews and patent searches.

Search internally using brainstorming, brainwriting. Examine solutions for the entire design, for

subfunctions of the design, and for individual components.

Critically and objectively evaluate concepts against common criteria.

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Open your mind to creativity◦ Innovation is important◦ There are strategies to apply

Apply Methods of Concept Generation◦ Search externally: Patents, research, experts◦ Search internally: SCAMPER, Morph Charts, Concept Fans,

Brainstorming, Nominal Group Technique Evaluate Concepts Critically◦ Strengths/Weaknesses◦ Decision Matrices◦ Pugh Concept Selection

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