1. Requirement Analysis 중앙대학교 전자전기공학부

2. Design for Electrical and Computer Engineers 3. Requirement analysis Our plans miscarry because they have no aime. When a man does not know what harbour he is making for, no wind is the right wind - Seneca, 4 BC to AD 65

3. Design for Electrical and Computer Engineers How will everyone with a stake know when it is done? Important check point check point for the “go, no-go” decisions that are a part of the design process from beginning to end 3. Requirement analysis

4. Design for Electrical and Computer Engineers 3.1 The importance of the requirement specification Costs accumulate exponentially as the design proceeds  Fewer than one in ten design projects results in a commercially viable product Identifying a design that should not be pursued, and doing so early in the design cycle will make a positive contribution to the company’s bottom line 계산서의 맨 밑줄, 손익 Methodological approach: Requirement Analysis

5. Design for Electrical and Computer Engineers 3.2 Developing the requirements specification In this requirement analysis stage, The focus is on a customer who needs a solution to a problem  In this step, engineer’s concern is not - to solve problem - but rather to understand what the problem is.  Engineering Goal is - to clarify, define, quantify the design objectives - to state these in the requirement specification.  Customers can - take different forms: client or marketing department - informed customer, frontier customer Design engineer should be prepared to act as a coach, mentor, expert, careful listener and adviser

6. Design for Electrical and Computer Engineers Probability of proceeding to next stage design Relative highRelatively low Informed customerFrontier customer Customer’s knowledge High - customer knows and understands what the design accomplish Low – No appropriate experience or example Availability of information - Customer - Equipment supplier - Competitor - Book, Journal - No existing equipment - No similar design Requirements specification Relative easyRelative difficult 3.2 Informed and Frontier customer

7. Design for Electrical and Computer Engineers 3.2.1 Bell Lab’s Example Bell Labs engineers are assigned the task of a new telecommunication equipment with low back-ground noise What is the maximum allowable level of back ground electronic noise on the telephone circuit? Customer’s needs How will I know when I am done? Design criteria needed Very subjective

8. Design for Electrical and Computer Engineers dBrnc represents an audio level measurement, typically in a telephone circuit, relative to the level of circuit noise, They conducted several years effort on noise measurement The result is a characterization of noise in terms of power and frequency noise signal

9. Design for Electrical and Computer Engineers 3.2.2 Two stage approach for requirement specification Output of this process is a document!!! - What exactly is the design team to do? - How will everyone know when the design is done? First stage  Assess the need of the customer  Organize the input into a statement of the design problem Second stage  Refine the problem statement by adding additional detail (a technical and quantified specification)

10. Design for Electrical and Computer Engineers 3.2.3 Real world consideration Real world inputs to the Design Process How?

11. Design for Electrical and Computer Engineers 3. 3 Needs assessment – stating the problem Nontechnical - Problem should be state in language of customer Specifiable - Although the problem statement is subjective, it should align with the more detailed and quantitative requirements specification Non-quantifiable - No specific dimension, quantities, and cost Complete - The problem statement should cover all aspect that engineer anticipate during the design First opportunity to understand the requirement of design

12. Design for Electrical and Computer Engineers To define the design problem  What is the problem to be solved?  Why is there a problem?  What is my role in solving the problem?  How will I know when I am done? Budget and schedule constraints  When is the solution needed?  What is the upper limit of cost?  What are your expectation of production cost, in high volume Reliability and maintenance  What are the consequences of the system failing once in operation?  What resource are available for maintenance? Question of contract  How will it be determined when the design is completed?  How will it be determined that the design is acceptable?  How will I be paid?  Is the work that I am to do legal? Engineer have to take initiative in questioning the customer on the needs 3. 3.1 Question the Customer

13. Design for Electrical and Computer Engineers 3.3.2 Needs and Wants If the problem statement was developed to reflect wants instead of needs We needs more feature than our competitor's product and must be cheaper to produce Which features needed? How much cheaper? - Unneeded features would be provided resulting in extra cost - Some needs would not be met, resulting in design deficiencies Engineer’s job is to translate the customer’s wants into a problem statement that reflects true needs

14. Design for Electrical and Computer Engineers 3.3.3 Explore Project Boundaries  External factor limit alternative solutions that engineer can consider when doing a design  There are legal boundaries to contend with  Project boundary are imposed by the need to fit within existing operations, standard, method, or procedure. ex) the customer need a common operating system and hardware platform so as to minimize staff training needs and simply maintenance

15. Design for Electrical and Computer Engineers 3.3.4 Input/output Analysis Input/output diagrams useful for finding unforeseen needs and indentifying for functions hidden input hidden output

16. Design for Electrical and Computer Engineers 3.3.5 Preview the User Interface  Most electronic products or systems exchange information with a human user. This exchange takes place through an interface that can take many forms – A keyboard, a switch, an audible tone, a visual indicator, a computer screen  The requirement statement must include the definition of user interface

17. Design for Electrical and Computer Engineers 3.3.6 Survey Design Attributes Nonfunctional Attributes User Interface Packaging Battery Production Reliability Functional Attributes Standard Functions Advanced Functions There are a number of attributes that are common to most design. Surveying them and assessing their relevance to the design problem will help expose needs

18. Design for Electrical and Computer Engineers 3.3.7 Conflicting Needs Don’t resolve the solution, which force customer to be realistic and to recognize need that may not be necessary Conflicting design needs Correlation Matrix clarify possible design conflicts

19. Design for Electrical and Computer Engineers 3.3.8 Draft of Operational Manual A. Product Overview B. Installation 1.Flow sensors 2.Velocity sensors 3.Cabling 4.Cutoff 5.Control unit C. Initial Setup 1.Alignment of sensors 2.Calibration 3.Testing D. Operation 1.Metric and imperial units of measure 2.Monitoring application rate and implement velocity 3.Cumulative measure – spray, area, distance 4.Alarms 5.Calibration check E. Maintenance 1.Routine servicing 2.Trouble shooting

20. Design for Electrical and Computer Engineers The amount of background noise heard on the telephone should not annoy the users Idle channel noise must be less than or equal to the 23 dBrnc Translate the needs to specification quantitatively in technical terms 3.4 Preparing the requirement specification

21. Design for Electrical and Computer Engineers  Translation method 1. Search out expert source 2. Analyze similar designs 3. Conduct test or experiments 3.4.1 Translating Needs to Specification Requirement specification 1:1 translation Design needs complete, consistency *Completeness : all design needs are covered *Consistency : there are no contradictions among the different design needs

22. Design for Electrical and Computer Engineers  User interface must be thoroughly specified in the requirement specification 3.4.2 Specification of Interface Points

23. Design for Electrical and Computer Engineers 3.4.3 Excessive Requirements Relationship between cost of design and product feature Cost-Reliability trade-off

24. Design for Electrical and Computer Engineers 3.4.4 Verification  If a design cannot be verified it should not specified  Unverifiable parameter must be removed or restated in a form that can be verified  It will be necessary to verify whether or not a design fulfills the needs of the customer as stated in the requirements specification. Final test Test plan refined

25. Design for Electrical and Computer Engineers 3.4.5 Document of requirement specification 1.Overviews 2. Statement of the problem 3. Operation description (draft user’s manual) 4. Requirement specification 5. Design deliverables 6. Preliminary system test plan 7. Implementation considerations - service and maintenance - manufacture Attachments - A. Study (lab reports or marketing studies, for example) - B. Relevant codes and standards

26. Design for Electrical and Computer Engineers SUMMARY  It should be the engineer’s contribution to manufacturers, operators, maintainers, and future designers – a reference document to help them in their work Requirement Specification  It should be an agreement between the engineer and the end user of the design  It should be the engineer’s guide as he or she moves through the design process  It should be the yardstick by which the completed design will be judged for its conformance to the initial objectives  It should provides a historical record of how the idea for the design came to be