chapter2 framework-for-design

Elec3017:Electrical Engineering Design

Chapter 2: A Framework for Design

A/Prof D. S. Taubman

September 18, 2006

1 Purpose of this ChapterIt is easy for design texts (and design courses) to begin to read like anthologies ofgood ideas. One reason for this is that there are many good ideas and practices.Another reason is that unless you are actually practicing design, it is hard tosee the relevance of all the suggestions. A third reason lies in the way manydesign texts are created, which usually involves numerous industrial field tripsto collect design case studies and sample current best practice.What is needed is a good framework for understanding design. The most

common framework found in textbooks revolves around the design phases intro-duced in Chapter 1. Variations on these design phases may be found in differentdisciplines of engineering, but there is also a great deal of commonality. Thedesign phases represent a useful framework, but they are not sufficient. If allyou needed for effective product design was to know the design phases, most ofyour university studies would be irrelevant. The purpose of this chapter is toprovide a broader framework for you to understand design. The phases formone aspect of this broader framework. Hopefully, this framework will also helpyou to put your past and future university studies into perspective.

2 Elements of the FrameworkThe key observation which lies behind the design framework provided here isthat many important design tools and skills are not specific to individual de-sign phases. It is helpful, therefore, to categorize the various aspects of designlearning into the following five areas:

• design phases;• design tools;• technical knowledge;

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c°Taubman, 2006 ELEC3017: Framework for Design

Customer needs solution to a problem

What features/performance are required?

What approaches could we take?

Block diagram

Technical specifications

What is the design problem?

Needs assessment

Requirements analysis

Problem statement

Concept generation

System design

Specifications analysis

Components, circuits, code, etc. Detailed design

Does the design meet the requirements? Prototyping and testing

Figure 1: Typical phases in the design process..

• design business strategy; and• technical communications.

2.1 Design Phases

We consider only the following phases, although others can potentially be iden-tified. These phases are also depicted in Figure 1.

1. Needs assessment

2. Requirements analysis

3. Problem statement

4. Concept generation

5. Concept selection and system design

6. Specifications analysis

7. Detailed design

8. Prototyping

9. Testing


The first two phases are most strongly focused on the customer. The pur-pose of a needs assessment is to identify customer needs which are not met byexisting products, while the purpose of requirements analysis is to determine thefeatures which target consumers require from products which they need. To helpclarify the distinction between needs assessment and requirements analysis, itis simplest to take the perspective of a consumer products manufacturing firm.In this case, needs assessment is an ongoing activity, which seeks to identifyproducts for which there may be a market. Requirements analysis, however, isnot a general ongoing activity; it is concerned with a specific product concept.The distinction between needs assessment and requirements analysis is less

clear for consulting engineering firms. In this case, the design process is normallyinitialized by a client who already has an identified need. In this setting, theterm needs assessment is sometimes used to describe a preliminary attempt todocument what the client actually wants to achieve. Since both of these phasesare strongly focused on customer perceptions, it is not surprising to find thatmarketing is the most important tool which supports them. As noted in thenext sub-section, however, marketing is also important to other phases in thedesign process.The third and fourth phases embody the most conceptual aspects of design.

Problem statement is the process of concisely stating the design problem, with aview to capturing its most fundamental objectives, challenges and constraints.Problem statement is more difficult than you might imagine. A good problemstatement should stay clear of two opposing evils. The first evil is that of impos-ing pre-conceived solution strategies on the problem. Consider, for example, theproblem of designing a new building product for driving nails. It is tempting todescribe the problem as that of designing a “more effective hammer.” However,this subtly imposes the form of an existing nail-driving solution (the hammer)on the design process. The second evil is that of providing a problem statementwhich is so vague that it is of no assistance in the subsequent concept generationphase. A good problem statement should be sufficiently specific that it exposesfundamental challenges and constraints of the design problem. We shall discussmethods for developing useful yet open problem statements in Chapter 4.The other primarily conceptual design phase is concept generation. The

main objective of this phase is to generate a large range of potential approachesto the design problem, at a high level. This requires lateral thinking, as well asan awareness of relevant technologies. The central distinction between conceptgeneration and subsequent design phases is breadth. During concept generation,you aim to find a large set of potential concepts without exploring them in anysignificant detail. During this process, it is possible (even desirable) that agood portion of the proposed concepts have no chance of actually working. Adeliberate lack of depth and willingness to suggest wacky concepts both facilitatecreative exploration of the possibilities. We shall discuss methods to stimulatethe creative process of concept generation in Chapter 4.System design, specifications analysis and detailed design are the most tech-

nical design phases. These are the central competencies required for a successfuldesign. All the creative concept generation and problem understanding in the


world are worthless if you cannot actually generate a design which will work.By contrast, if you have mastered the technical aspects of design, you may wellbe able to find a solution of sorts, even if you have only a narrow view of theproblem with an incomplete understanding of the requirements. This point isfrequently understated by design texts, which tend to focus on the conceptualaspects of design.At its simplest, system design is a disciplined approach to the creation of

block diagrams, so as to expose major sub-systems and the relationship betweenthem. One goal of system design is to provide early identification of critical sub-systems, whose design might prove challenging or even impossible. This mayforce a return to the concept generation phase or even the requirements. Systemdesign cannot proceed until one of the concepts generated in the previous phasehas been selected. It is convenient to lump concept selection and system designtogether, since they are tightly connected. For example, rough system designsfor several different concepts may need to be created before a “final” conceptselection can take place1. We shall have more to say on system design, andblock diagrams in particular, in Chapter 4.The distinction between requirements analysis and the more technical phase

of specifications analysis has already been elaborated in Chapter 1. Exactlywhere the specifications analysis phase belongs in the design process can varywith the nature of the design problem. Some specifications can be derived fromrequirements alone. In other cases, specifications are inherently dependent onthe selected design concept. This often happens in very complex designs. Evenin the simple case of a household electric heater, specification of the heatingelement’s power rating may be strongly dependent on selected concepts such asradiative vs. convective heat transfer.The one thing we can say is that an attempt to derive technical specifications

should be made prior to the detailed design phase. Detailed design is concernedwith such matters as circuit design, component selection, digital logic design,operating frequency selection, software coding, algorithm parameter selection,PCB layout, and much more. There is not much to be said about the detaileddesign phase itself, but there is a lot to be said about detail design tools, relevanttechnical knowledge and so forth. As such, chapters 6 to 9 are all highly relevantto the detailed design phase.The final two design phases, prototyping and testing, are closely connected.

Prototyping plays a particularly important role in Electrical Engineering for tworeasons:

• Massive advances in miniaturization mean that the systems designed byElectrical Engineers tend to be highly complex, with internal interactionswhich are hard to fully comprehend or adequately simulate.

• Low cost and the availability of highly advanced prototyping tools make itpossible to prototype your ideas much more quickly and realistically thanin many other branches of Engineering.

1Actually, nothing is very “final” about most design activities.


Accordingly, you should not be surprised to learn that electronic product designoften involves a large number of prototyping phases. In this course, you willconstruct a functional prototype of your product. Prior to that point, you mayprototype a variety of critical sub-systems and sub-circuits to better understandtheir behavior and interaction. The functional prototype itself, however, existsonly to verify a subset of the final product’s features. Near the end of a productdesign process, one or more manufacturing prototypes are typically created totest as many aspects of the final product as possible prior to manufacture. Youshould be prepared to spend more than half of the overall effort ofyour design project in the detailed design and prototyping phases.Testing is, of course, closely connected to prototyping. There is currently a

growing need for capable test engineers in the workforce. One aspect of testingis the development of test plans, based on the specifications. Testing also goeshand in hand with debugging. Debugging is the domain of the engineering“super-sleuth,” tracking problems to their source through a trail of obscureclues. The need for debugging is unavoidable in complex products. In somecases, testing and debugging may take as long or even longer than the detaileddesign phase.

2.2 Design Tools

We identify the following design tools here, noting that this list is far fromexhaustive.

1. Marketing tools

These include focus groups, surveys, lead user interviews, market research,monitoring of competitors and other methods to assess consumer needs,consumer requirements and valuable features for products.

Marketing tools are central to the first two design phases: needs assess-ment and requirements analysis. However, marketing tools can play animportant role in other phases of the design process. Marketing tools areused to understand the relationship between features, price and sales vol-ume, which in turn informs the detailed design phase. Marketing toolsare used to assess prototypes, compare various industrial designs (i.e., thelook and feel of the product), and so forth.

Marketing tools are the subject of Chapter 3.

2. Project management tools

Project management is the discipline you need to carry any complex de-sign process to successful completion, within budget and time constraints.Surprisingly, the tools of project management play an important role evenin small group design projects such as that undertaken in this course. Atthe end of the course, students are frequently able to point to projectmanagement failures as their chief downfall. Project management is thesubject of Chapter 5.


3. Economic analysis tools

We look at manufacturing costs in Chapter 11. In the same chapter, wealso introduce tools for economic decision making. These tools help youto make design decisions on a profit and loss basis.

4. Process tools

We look at quality assurance processes for design in Chapter 14. These areprocesses which are used to monitor and continuously improve the overalldesign methodology followed within an engineering firm. These processesare particularly important to the Computing and Electrical Engineeringprofessions. This is because these professions design systems of such com-plexity that quality cannot be reliably assessed through testing of the finalproduct.

5. System engineering tools

Systems engineering is a large topic and an area of high demand for pro-fessional engineers. A practicing systems engineer has been invited toprovide you with an introduction to this field.

6. Simulation tools

Examples include Spice, Simulink, Matlab, EM finite element analysistools, etc.

7. Prototyping tools and methods

Electronic prototyping tools include circuit assembly systems such asbreadboards, veroboard and wire-wrap systems. During this course, youshould learn good wiring and component placement techniques, if you arenot already familiar with them.

Field Programmable Gate Arrays (FPGA’s) provide excellent platformsfor rapidly and convincingly prototyping complex digital designs. Prior tothe development of a custom ASIC, design engineers usually develop anFPGA implementation. Of course, FPGA’s are also widely deployed infinal products sold to consumers.

Modern micro-controllers come with excellent tool support for rapid pro-totyping and testing.

8. Computer Automated Design (CAD) tools

In this course, you will use the Atrium (formerly Protel) suite of schematiccapture and printed circuit board (PCB) design tools. We look at PCBdesign in Chapter 13.

9. Mechanical drawing

Material in this area is taught separately by the School of Mechanical andManufacturing Engineering.


2.3 Technical Knowledge

In addition to tools, the design engineer needs to be equipped with a wide rangeof technical knowledge. This is one of the main reasons you go to University.Here are some significant areas of technical knowledge, important for design.

1. Electronic components

You need to be aware of the electrical properties, tolerances and ratingsof common electronic components (see Chapter 6).

2. Circuits

You need to be familiar with analog and digital circuit analysis and syn-thesis techniques.

You need to be able to recognize common circuit configurations.

You need to be aware of the existence of circuit solutions to a variety ofcommon sub-problems. The more you know, the more likely you are tobe able to come up with good designs.

Circuit knowledge and practice will help make you proficient in readingand exploiting the wealth of information provided in manufacturers’ datasheets.

Electronic circuit knowledge is principally acquired through other coursesin your degree program, but Chapter 7 of your lecture notes for this courseprovides some useful ideas.

3. Electromagnetic Compatibility (EMC)

This is an area of knowledge to which some effort will be devoted in thiscourse (Chapter 8). Most people have experienced the effects of electronicinterference through their televisions, radios, mobile phones and the like.Common sources of such interference include electric appliances (particu-larly those with commutated motors) and computers.

Designers generally need to be aware of the various modes through whichinterfering signals may be coupled. Designers also need to be equippedwith at least some techniques to minimize the effects of interference. Insome cases, designers may need to be familiar with relevant regulatorystandards governing acceptable levels of generated electromagnetic inter-ference.

4. Feedback and Control

This is one of the fundamental disciplines of Electrical Engineering, andone which is guaranteed to have enduring value and applicability to a widerange of problems in design and elsewhere.

The vast majority of analog circuits rely heavily on feedback to providepredictable behaviour. Feedback is also found in numerous complex sys-tems, involving analog and digital electronics, software components, and


so forth. Fundamental questions relating to stability, settling time andsensitivity to noise can be answered using analytical methods. Moreover,designers are able to recognize the factors which affect these issues and sooptimize design performance.

Control theory and practice cannot be taught in ELEC3017, for obviousreasons. Whole subjects in your degree program are devoted to this bodyof knowledge.

5. Signal Processing

Many of the project topics or design concepts students first think of inELEC3017 require signal processing techniques. Examples include tonedecoding, signal extraction from noise, echo location, voice recognitionand many others. Some of these projects require too much knowledgeor too much development effort to be undertaken in the present course,but the message is clear: signal processing is a core electrical engineeringwhich is central to many design problems.

Signal processing theory and practice cannot be taught in ELEC3017, forobvious reasons. Whole courses in your degree program are concernedwith this body of knowledge. The advanced signal processing techniquesused in many practical designs cannot be taught until the 4th year, inELEC4042, due to the intellectual maturity required to appreciate them.

6. Physical Communications

Analog and digital communication techniques, signal recovery in the pres-ence of noise and interference, error correction techniques, channel equal-ization strategies and so forth, are all highly relevant to the design ofproducts which communicate. Communication is not just what happenswhen you use your mobile phone. Internal communications within manycomplex systems employ sophisticated techniques. In the future, this islikely to apply even to the communication between sub-systems on a singlechip. Like control and signal processing, communication theory is one ofthe fundamental disciplines of Electrical Engineering which is guaranteedto have enduring value and applicability.

Physical communication theory and practice cannot be taught inELEC3017, for obvious reasons. Whole courses in your degree programare concerned with this body of knowledge.

7. Software Programming Languages

It is important not to draw too big a distinction between software andhardware. Most electronic products with any level of sophistication in-volve a combination of both hardware and software components. Electricalengineering design almost inevitably involves software, and most electricalengineers spend at least some of their time programming. Control, signalprocessing or communication algorithms designed by electrical engineersare implemented first in software, both for verification and often also for


consumer deployment. Over time, increasing portions of the design mightbe ported to dedicated hardware, first to FPGA’s and then maybe to anASIC, so as to drive down manufacturing costs, increase speed and/ordecrease power consumption. One rule of thumb is that moving a com-putationally expensive process from a general purpose CPU or DSP to anFPGA will bring a 50-fold increase in speed for a given cost (equivalently,a 50-fold reduction in cost for a given speed). Moving from FPGA toASIC may bring a further 50-fold gain. The corresponding developmenteffort, however, may be enormous.

Complex designs realized through FPGA’s, ASIC’s, or a combination ofboth, normally include embedded CPU’s which must be programmed. Atthe other end of the scale, microcontrollers are stand-alone processorswhich are designed to realize complete systems with as few components aspossible, by including common I/O hardware on the same chip. Whetherthe processor is embedded in a piece of hardware, a microcontroller, orthe general purpose CPU in a desktop PC, programming is an essentialskill for the designer of electronic products.

Programming cannot be taught in ELEC3017, but you should endeav-our to acquire as much confidence as possible in computer programming.The Electrical and Telecommunications Engineering syllabi include onlytwo formal programming courses, but you should endeavour to augmentthese skills by taking programming assignments and laboratory exercisesin other courses very seriously. You should also approach programmingaspects of any 4th year thesis project that you undertake as an opportunityto broaden your skills and increase your confidence/

8. Hardware Description Languages

Digital hardware design itself is too complex to be done entirely man-ually. Instead, hardware designers must learn to program in hardwaredescription languages such as Verilog or VHDL.

Hardware description languages cannot be taught in ELEC3017, but youshould consider acquiring this valuable skill to round out your capabilitiesas a design engineer.

9. Manufacturing Processes

Successful design cannot be carried out in isolation, without an awarenessof the manufacturing processes that will be used to manufacture the de-signed product. The sequential approach of first designing a product andthen handing it on to manufacturing engineers to “tweak things” for easeof manufacturing has been abandoned long ago. The sequential approachtakes too long, costs to much, and may produce designs which simply can-not be manufactured. Concurrent engineering is the term used to describethe integration of manufacturing considerations during product design. Inthis course, you will be introduced to some of the relevant manufacturing


considerations (see Chapter 12). You will also be required to incorporatemanufacturing considerations into your design project’s final report.

10. Safe and Ethical Design Practices

Safety is a strong focus of modern product design, and rightly so. De-signing for safety is the subject of Chapter 9. Broader ethical issues inelectrical engineering are the subject of an entire course in the 4th year ofyour program and a condition of accreditation by the Australian Instituteof Engineers.

2.4 Design Business Strategy

1. Regulatory and industry standards

Some standards are the subject of government regulation so that beingaware of their existence and following their stipulation becomes a matterof law. The majority of standards are created by industry representatives,usually in open fora, but sometimes in closed consortia. These standardsgovern the way in which products should be designed so as to success-fully interoperate with each other. Customers should be unwilling to buyproducts which cannot interoperate with related products from other man-ufacturers. Since these standards are created by industry representatives,there are strong business incentives to participate in standardization ac-tivities. We shall have more to say about this in Chapter 15.

2. Intellectual property

Intellectual property is the term used to refer to patents, copyright, trade-marks and some less well-known forms of legal protection such as regis-tered designs. Patents are a strong form of legal protection. Patents heldby others can prevent you from designing and marketing products whichincorporate the protected ideas, regardless of whether or not you come upwith the ideas independently. By the same token, maintaining a patentportfolio of your own can be an important business strategy. You cannotafford to be ignorant of patents and how they work. Chapter 16 is devotedto this topic.

2.5 Technical Communication

1. Written communication

Technical writing is a vital skill for design and for your career in general.General writing ability and language proficiency certainly help, but thereis a lot more to good technical writing. Technical writing also plays animportant role in this course, being the subject of Chapter 10.

2. Oral presentation skills

The ability to prepare and deliver an effective oral presentation is notsomething you were born with. This is a slightly less important skill than


Table 1: Topics taught in ELEC3017

Topic Week Most relevant design phasesMarketing (tools) 2 needs + requirements analysisConcept generation (phase) 2 concept generationSystem design (phase) 3 system designProject management (tools) 3 allElectronic components (knowledge) 3-4 detailed designCircuit ideas (knowledge) 4 detailed designEM compatibility (EMC) 4-5 detailed design + testingPrototyping methods (tools) 5 prototypingSpecifications and testing (phases) 5 specifications analysis + testingSafe design (knowledge) 6 detailed designTechnical writing (communication) 6 allCosting and economics (tools) 6 detailed designQuality assurance (tools) 7 allStandards (strategy) 7 detailed design + testingIntellectual property (strategy) 7 concept generation + system designManufacturing (knowledge) 8 system design + detailed designSystems engineering (tools) 8 detailed designPCB design (tools) 9 detailed designMechanical drawing (tools) 10-11 detailed designOral presentations (communication) 12-13 all

technical writing, but still deserves some significant attention. Confidencein your own understanding of the design problem and your design solutionare key ingredients to success in the ELEC3017 project seminar.

3 The Framework Related to ELEC3017For a variety of reasons, teaching in ELEC3017 will not be organized solelyon the basis of the categories presented in the previous section. One of thesereasons is that you need to receive information in an order which best facilitatesyour ongoing design project. In the end, the categories are most useful inhelping you to see how the things which you learn fit together. Quite a bit ofthis course focuses on design tools and knowledge, rather than specific designphases, but the framework allows you to see how these tools relate to one or moreof the design phases. Other aspects of the course exist to extend your technicalknowledge. In this respect, though, the course serves only to supplement yourlearning in other courses, all of which are ultimately intended to help you design.Table 1 provides a convenient summary of relationship between topics taught

in ELEC3017 and the design phases to which they are most relevant. As foryour formal written lecture notes, the topics covered should be as follows2.

2We say “should be” because these lecture notes are still being written.


Chapter 1: Introduction to Design

Chapter 2: A Framework for Design

Chapter 3: Tools — Marketing

Chapter 4: Phases — Problem Statement, Concept Generation and SystemDesign

Chapter 5: Tools — Project Management

Chapter 6: Knowledge — Electronic Components

Chapter 7: Knowledge — Electronic Circuits

Chapter 8: Knowledge — Electromagnetic Compatibility

Chapter 9: Knowledge — Safe Design Practices

Chapter 10: Technical Writing

Chapter 11: Tools — Economics and Costing Design

Chapter 12: Knowledge — Manufacturing Processes

Chapter 13: Tools — PCB Design

Chapter 14: Tools — Quality Assurance

Chapter 15: Strategy — Standards

Chapter 16: Strategy — Intellectual Property