The Need Specification

References  Adapted from:  Design for Electrical and Computer Engineers, first edition, by Ralph M. Ford and Chris S. Coulston  Excerpts from the book “Engineering Design, a Project Based Introduction”, second edition by Clive I. Dym and Patrick Little. John Wiley and Sons, Inc. ISBN

What are Specifications?

 Specification A detailed and exact statement of particulars, a statement fully describing something to be built. American Heritage Dictionary  Specifications A detailed, exact statement of particulars, especially a statement prescribing materials, dimensions, and quality of work for something to be built, installed, or manufactured. answers.com  Specifications may indicate as well acceptance criteria (very important). Definitions

What to Specify?

6  Marketing Requirements (Statements of the Client and User Needs)  In your case The Marketing Requirements are The Objectives and The Problem Statement resulting from the attributes in the Need Analysis  Short statements that describe the need in the language of the client (or the user)  “The amplifier should have good sound quality”  Interview, survey, brainstorming Definitions

7  Engineering Requirements  Short statements that describe the technical needs of the design  The Marketing Requirements should be translated into Engineering Requirements  “The amplifier should have low harmonic distortion”  In your case The Specifications will be derived from the Engineering Requirements, In other words, you need to find specifications for the objectives. Definitions

Who defines the specifications?

 The Client and the Team.  After the Need Analysis  One or more meetings

Marketing and Engineering Requirements, where do they fit in the Proposal? 10

Marketing and Engineering Requirements  Marketing Requirements: In the Problem Statement and Need Analysis sections the results from the interview, survey and brainstorming will show the Marketing Requirements  Engineering Requirements: In the End Product Description and Specifications section of your proposal you translate the Marketing Requirements into Engineering Requirements.

Engineering Requirements Properties 1) Abstract  What the system will do, not how it will be implemented 2) Verifiable  There should be a way to measure or demonstrate that the requirement is met in the final realization 12

Engineering Requirements Properties 3. Unambiguous  Each requirement should have a single unambiguous meaning and be stated with short complete sentences. 4. Traceable  Each Engineering requirement should be traceable to a Marketing Requirement IEEE Std

Example Does the following requirement meet the four desirable properties? (abstract, verifiable, unambiguous, traceable) “The robot must have an average forward speed of 0.5 feet/sec, a top speed of at least one foot/sec, and the ability to accelerate from standstill to the average speed in under one second.” 14

Example Does the following requirement meet the four desirable properties? (abstract, unambiguous, verifiable, traceable) “The robot must employ IR sensors to sense its external environment and navigate autonomously with a battery life of one hour.” 15

Identifying Engineering Requirements  In addition to Interviews, surveys and brainstorming Observation of processes and devices in use Benchmarking and market analysis Prototyping and simulation  Research survey 16

The Requirements Specification 17

Requirements Specification  Collection of both Marketing and Engineering requirements that the design must satisfy in order for it to be successful.  The Requirements Specification organizes and communicates requirements to: The client and the technical community (two different languages).  Your Requirements Specification is: The whole Proposal

Requirements Specification

 Normalized/Orthogonal No redundancy between engineering requirements  Complete Set Addresses all of the needs  Client  User  Designer 20 Properties of the Requirements Specification

 Consistent No contradictions among the requirements  Bounded Minimum bound for acceptable target (Technical specifications, numbers)  IEEE Std Properties of the System Requirements Specification

Validation VS. Verification

Validation = Are we building the right product? (Marketing Requirements) Verification = Are we building the product correctly? (Technical Specifications) 23 Validation

Technical specification  A complete list of the technical details for a given system, e.g., accuracy, speed, dimensions, etc Attaching numbers to the Engineering Requirements  List as a table at the end of section

The Process 25

Translating the Need into Engineering Requirements and Technical Specifications  Express your objectives in Engineering Language (Engineering Requirements)  Find the Engineering Requirements Technical Specifications (Specs) There are different ways to do it

Translating the Need into Engineering Requirements and Technical Specifications Performance  Performance specifications identify performance levels that signify the achieved desired functional behavior.  The system should detect 90% of all human faces in an image.  The amplifier will have a total harmonic distortion less than 1%. 27

 Procedural specifications identify specific procedures for calculating attributes or behavior. For example: The design is safe if its maximum current at the input, when the output is shorted is less than 5A. Translating the Need into Engineering Requirements and Technical Specifications

Reliability & Availability  The system will have a reliability of 95% in five years.  The system will be operational from 4AM to 10PM, 365 days a year. Translating the Need into Engineering Requirements and Technical Specifications

Energy  The system will operate for a minimum of three hours without needing to recharge Operating Environment  The system should be able to operate in the temperature range of 0°C to 75°C.  The system must be waterproof and operate while submersed in water. 30

One Example

Marketing Requirements 1.The system should have excellent sound quality. 2.The system should have high output power. 3.The system should be easy to install. 4.The system should have low cost. Car Audio Amp

THD Output Power Marketing Requirements 1.The system should have excellent sound quality. 2.The system should have high output power. 3.The system should be easy to install. 4.The system should have low cost. Car Audio Amp Translate Marketing language into Engineering Language and find the technical specs and justifications

1, 2, 4The total harmonic distortion should be <0.1%. Based upon competitive benchmarking and existing amplifier technology. Class A, B, and AB amplifiers are able to obtain this level of THD. 1–4Should be able to sustain an output power that averages  35 watts with a peak value of  70 watts. This power range provides more than adequate sound throughout the automobile compartment. It is a sustainable output power for projected amplifier complexity. Marketing Requirements 1.The system should have excellent sound quality. 2.The system should have high output power. 3.The system should be easy to install. 4.The system should have low cost. Car Audio Amp

Probably most of user will not distinguish between.1% and.01% THD Or Probably 200 W will represent a hazard for users in a car Probably nobody will buy a 10% THD Or one that delivers a max of 5W

How to determine the values: Trade-Off THDPowerUsually the better the spec the more expensive to produce

How to determine the values: Trade-Off THD Power THD Power Usually the better the spec the more expensive to produce Probably improving the THD spec may require to impair a little the power spec to keep price reasonable

How to determine the values:  Competitive Benchmarks  Cost  Perception

Apex AudioMonster AmpsOur Design THD0.05%0.15%0.1% Power30W50W35W Efficiency70%30%40% Cost$250$120$ Competitive Benchmarks

Marketing Requirement s Engineering RequirementsJustification 1, 2, 41.The total harmonic distortion should be <0.1%. Based upon competitive benchmarking and existing amplifier technology. Class A, B, and AB amplifiers are able to obtain this level of THD. 1–41.Should be able to sustain an output power that averages  35 watts with a peak value of  70 watts. This power range provides more than adequate sound throughout the automobile compartment. It is a sustainable output power for projected amplifier complexity. 2, 41.Should have an efficiency (  ) >40 %. Achievable with several different classes of power amplifiers. 31.Average installation time for the power and audio connections should not exceed 5 minutes. Past trials using standard audio and power jacks demonstrate that this is a reasonable installation time. 41 Car Audio Amp. Your Specs should look like this

1–41.The dimensions should not exceed 6” x 8”x 3”. Fits under a typical car seat. Prior models and estimates show that all components should fit within this package size. 1–41.Production cost should not exceed $100. This is based upon competitive market analysis and previous system designs. Marketing Requirements 1.The system should have excellent sound quality. 2.The system should have high output power. 3.The system should be easy to install. 4.The system should have low cost. 42

Advanced Requirements Analysis 43

THD Output Power , Efficiency Install Time Dimensions Cost ) Sound Quality+ 2) High Power+ 3) Install Ease+ 4) Cost- 44 Engineering Marketing Matrix Used to determine the impact of Marketing requirements over Engineering Requirements

THD Output Power , Efficiency Install Time Dimensions Cost THD- Output Power+ , Efficiency+ Install Time- Dimensions- Cost- 46 Engineering Tradeoff Matrix Used to determine the impact of Engineering requirements over other Engineering Requirements

Engineering Tradeoff Matrix

Apex AudioMonster AmpsOur Design THD0.05%0.15%0.1% Power30W50W35W Efficiency70%30%40% Cost$250$120$ Competitive Benchmarks

The House of Quality

When looking at Peak Closing Force, we see that improving this will impair the Door Seal Resistance

The House of Quality

 Properties of engineering requirements  Examples of engineering requirements  Properties of the System Requirements Specification  Advanced Requirements Analysis Tradeoff matrices Benchmarks 53 Review

& & Q uestions A nswers