Design Process 중앙대학교 전자전기공학부

Design for Electrical and Computer Engineers 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 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 REPEAT (Find Solutions) 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) 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 6 th solution 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$. How much money is required for the first solution? -Probability problem >> 6 M$ - Only one casting needed : 1M$ How much money is required for the 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 3. Synthesis First attempt using LED Oops, Engine block heater is out of order Block heater: preventing engine oil from getting viscous on the cold winter days 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. 4. Analysis High current LED is too expensive 3A (working) 0.5A (Out of order) 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

Design for Electrical and Computer Engineers Which one is better? Ask to the Customer Repeat synthesis/analysis again! 3.1 Synthesis 1 st solution using current transformer 4.1 Analysis - Transformer equation - Cost : 4.5$ 3.2 Synthesis 2 st solution using Light bulb with momentary switch 4.2 Analysis - User has to push the switch when he or she uses - Cost : 4.0 $

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. 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!!!  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. performancecost Main factor judging the design Reliability maintainability

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. - Focusing on getting correct answer- Focusing on minimizing key strokes Methodology AMethodology B - Add all numbers and do it again until two sums are the equal - Partitions numbers to 100 pieces - Same tactics for 100 number - Same tactics for 100 pieces If both contestants make no errors If both contestants make the same number of errors A is more faster than B B is more faster than B

Design for Electrical and Computer Engineers - Considers only one possible solution- Considers a number of solution at a time Methodology AMethodology B - 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 - Less expensive, Fast development time - More effort and thought is devoted to unused solution Design methodology affects both the efficiency and effectiveness of engineer. 2.4 Design methodologies

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 productIndustrial product Sensitive to CostSensitive 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 Ideal design methodology (does not allow for correction of mistakes) Design criteria - Consumer product: Cost - Industrial product: Quality documentation Practical design methodology

Design for Electrical and Computer Engineers - Action item 1 - Action item 2 - Action item 3 Requirement specification 2.5 A methodology for high quality - Action item 1 - Action item 2 - Action item 3 System specification - Action item 1 - Action item 2 - Action item 3 Functioning module - Action item 1 - Action item 2 - Action item 3 Ideal design methodology (does not allow for correction of mistakes) Practical design methodology This chapter provides us an overview of a design methodology, In next chapter, the associated concept will be explained Documentation