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Design Process
중앙대학교
전자전기공학부
2. Design Process
 Engineering
: Problem solving through specialized scientific and mathematical knowledge
 Engineer
: People who solves a variety of problem as a routine part of their job
 Engineering problem
: So complex, the engineer cannot instantly see the solution. therefore,
the methodological approach becomes more important
In chapter 2, we will focus on the methodological
engineering design process to tackle a complex problem
Design for Electrical and Computer Engineers
2.1 General engineering process
Customer needs
Engineer’s translation of needs including
desired outcomes
Synthesis : Putting together of parts or elements
so as to form a whole, typically associated with
a new system
REPEAT (Find Solutions)
Analysis: A separating or breaking up of any
whole into its part, especially with an
examination of these parts to find out their
nature, proportion, function, inter relationship,
etc
Decision: Best solution being among the
solution found increase number of solution
generated,
how many solution needed to explored?
TRADE - OFF
Design for Electrical and Computer Engineers
Let’s cast a die!!! (Example 2.1)
Each face of the die has one of six possible solutions!
We don’t know the value of six possible solution until casting
The cost of obtaining a solution is 1 M$.
How much money is required
for the first solution?
- Only one casting needed : 1M$
How much money is required for
the 6th solution?
-Probability problem >> 6 M$
Engineer does not know the worth of any solution that has not been obtained, the
only way the engineer can be sure to obtain the best solution is to obtain all six,
however, the cost of all solution is relatively high. And the most expensive is
likely to obtain 6th solution
Decision making whether further solutions are developed is very important
Design for Electrical and Computer Engineers
2.2 Applying the general engineering process
Oops, Engine block heater
is out of order
1. Symptom, Problem:
1. AC outlet circuit to power block heater get overloaded time
to time, the unsuspecting user plug their block heaters into
dead outlets
2. Block heaters burn out and go open circuit
3. Customer has to know if things were not working properly
when they plugged in their block heaters.
Block heater: preventing engine oil
from getting viscous on the cold
winter days
2. Problem definition
Design a device to be integrated with an extension cord that
will detect the difference 0.5 A (not working) and 3 A
(working). The device must not consume more than 5 Watt and
its manufactured cost including the cost integration must be
less than 6 dollars
3. Synthesis
First attempt using LED
4. Analysis
High current LED is too expensive
3A (working)
0.5A (Out of order)
Design for Electrical and Computer Engineers
Repeat synthesis/analysis again!
3.1 Synthesis
1st solution using current transformer
3.2 Synthesis
2st solution using Light bulb with momentary switch
4.1 Analysis
- Transformer equation v  N  d dt 
- Cost : 4.5$
4.2 Analysis
- User has to push the switch when he or she uses
- Cost : 4.0 $
Which one is better?
Ask to the Customer
Design for Electrical and Computer Engineers
2.3 Evaluation of alternative solutions
 General engineering process has been described in terms of arriving
at a “best” or “optimum” solution.
 In most practical situations, true optimum solutions are impossible
to derive. The best that can be achieved is near optimum, or the best
among several alternative.
 How we decide which of several solution is the best alternative? The
problem definition is the yardstick for judgment and therefore it
becomes a critical step in the design process.
Main factor judging the design
performance
Reliability
maintainability
cost
If a decision is difficult to make, it is probably because there is not much
difference in the worth of the alternatives. Do not waste time agonizing
over these decisions.
Simply flip the coin!!!
Design for Electrical and Computer Engineers
2.4 Design methodologies
Given 10,000 4-digit numbers.
Add the numbers with a hand-held calculator and submit their
answers. Contestants whose answer is correct are ranked in the
order of submission. Contestants submitting incorrect answer
disqualified. The object is to finish with a high rank.
Methodology A
Methodology B
- Focusing on getting correct answer
- Add all numbers and do it again until
two sums are the equal
- Focusing on minimizing key strokes
- Partitions numbers to 100 pieces
- Same tactics for 100 number
- Same tactics for 100 pieces
If both contestants make no errors
A is more faster than B
If both contestants make the same number of errors
B is more faster than B
Design for Electrical and Computer Engineers
2.4 Design methodologies
Methodology A
Methodology B
- Considers only one possible solution
- Considers a number of solution at a time
- Completes the detailed design, implement
the solution and evaluates according to
design criteria
- Does not carry them to the detailed design
and implementation stage instead, only
completes initial or block-level design
- Repeat until satisfactory solution is
obtained
- Evaluate the block-level design and discard
some solution not satisfying the criteria
- Select some promising solution for further
investigation
- More effort and thought is devoted to
unused solution
- Less expensive, Fast development time
Design methodology affects both the efficiency and effectiveness of engineer.
Design for Electrical and Computer Engineers
Design methodologies
 A subjective comparison of design methodologies is an onerous task for
the primary reason that engineering problems have multidimensional
evaluation criteria.
Design Criteria
Consumer product
Industrial product
Sensitive to Cost
Sensitive to Performance
 A good design methodology must determine early in the process
whether or not the problem can be solved
Design for Electrical and Computer Engineers
2.5 A methodology for high quality
documentation
Design criteria
- Consumer product: Cost
- Industrial product: Quality
Ideal design methodology (does not allow for correction of mistakes)
Practical design methodology
Design for Electrical and Computer Engineers
2.5 A methodology for high quality
- Action item 1
- Action item 2
- Action item 3
Requirement specification
- Action item 1
- Action item 2
- Action item 3
System specification
Documentation
- Action item 1
- Action item 2
- Action item 3
Functioning module
- Action item 1
- Action item 2
- Action item 3
This chapter provides us an overview of a design
methodology, In next chapter, the associated concept
will be explained
Ideal design methodology (does not allow for correction of mistakes)
Practical design methodology
Design for Electrical and Computer Engineers