Elec3017: Electrical Engineering Design Chapter 2: A Framework for Design A/Prof D. S. Taubman September 18, 20061 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 mostcommon 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; 1
c°Taubman, 2006 ELEC3017: Framework for Design Page 2 Customer needs solution to a problem Needs assessment What features/performance are required? Requirements analysis What is the design problem? Problem statement What approaches could we take? Concept generation Block diagram System design Technical specifications 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 PhasesWe 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
c°Taubman, 2006 ELEC3017: Framework for Design Page 3 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 lessclear 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. Themain 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
c°Taubman, 2006 ELEC3017: Framework for Design Page 4world 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 ofblock 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 phaseof 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 speciﬁcationsshould 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 by Electrical Engineers tend to be highly complex, with internal interactions which are hard to fully comprehend or adequately simulate. • Low cost and the availability of highly advanced prototyping tools make it possible to prototype your ideas much more quickly and realistically than in many other branches of Engineering. 1 Actually, nothing is very “ﬁnal” about most design activities.
c°Taubman, 2006 ELEC3017: Framework for Design Page 5Accordingly, 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 agrowing 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 ToolsWe 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 an important role in other phases of the design process. Marketing tools are used to understand the relationship between features, price and sales vol- ume, which in turn informs the detailed design phase. Marketing tools are used to assess prototypes, compare various industrial designs (i.e., the look 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 even in small group design projects such as that undertaken in this course. At the end of the course, students are frequently able to point to project management failures as their chief downfall. Project management is the subject of Chapter 5.
c°Taubman, 2006 ELEC3017: Framework for Design Page 6 3. Economic analysis tools We look at manufacturing costs in Chapter 11. In the same chapter, we also introduce tools for economic decision making. These tools help you to make design decisions on a proﬁt and loss basis. 4. Process tools We look at quality assurance processes for design in Chapter 14. These are processes which are used to monitor and continuously improve the overall design methodology followed within an engineering ﬁrm. These processes are particularly important to the Computing and Electrical Engineering professions. This is because these professions design systems of such com- plexity that quality cannot be reliably assessed through testing of the ﬁnal product. 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 to provide you with an introduction to this ﬁeld. 6. Simulation tools Examples include Spice, Simulink, Matlab, EM ﬁnite element analysis tools, etc. 7. Prototyping tools and methods Electronic prototyping tools include circuit assembly systems such as breadboards, veroboard and wire-wrap systems. During this course, you should learn good wiring and component placement techniques, if you are not already familiar with them. Field Programmable Gate Arrays (FPGA’s) provide excellent platforms for rapidly and convincingly prototyping complex digital designs. Prior to the development of a custom ASIC, design engineers usually develop an FPGA implementation. Of course, FPGA’s are also widely deployed in ﬁnal 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 schematic capture and printed circuit board (PCB) design tools. We look at PCB design in Chapter 13. 9. Mechanical drawing Material in this area is taught separately by the School of Mechanical and Manufacturing Engineering.
c°Taubman, 2006 ELEC3017: Framework for Design Page 72.3 Technical KnowledgeIn 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 ratings of 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 of common sub-problems. The more you know, the more likely you are to be able to come up with good designs. Circuit knowledge and practice will help make you proﬁcient in reading and exploiting the wealth of information provided in manufacturers’ data sheets. Electronic circuit knowledge is principally acquired through other courses in your degree program, but Chapter 7 of your lecture notes for this course provides some useful ideas. 3. Electromagnetic Compatibility (EMC) This is an area of knowledge to which some eﬀort will be devoted in this course (Chapter 8). Most people have experienced the eﬀects of electronic interference 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 which interfering signals may be coupled. Designers also need to be equipped with at least some techniques to minimize the eﬀects of interference. In some cases, designers may need to be familiar with relevant regulatory standards governing acceptable levels of generated electromagnetic inter- ference. 4. Feedback and Control This is one of the fundamental disciplines of Electrical Engineering, and one which is guaranteed to have enduring value and applicability to a wide range of problems in design and elsewhere. The vast majority of analog circuits rely heavily on feedback to provide predictable behaviour. Feedback is also found in numerous complex sys- tems, involving analog and digital electronics, software components, and
c°Taubman, 2006 ELEC3017: Framework for Design Page 8 so forth. Fundamental questions relating to stability, settling time and sensitivity to noise can be answered using analytical methods. Moreover, designers are able to recognize the factors which aﬀect these issues and so optimize design performance. Control theory and practice cannot be taught in ELEC3017, for obvious reasons. Whole subjects in your degree program are devoted to this body of knowledge. 5. Signal Processing Many of the project topics or design concepts students ﬁrst think of in ELEC3017 require signal processing techniques. Examples include tone decoding, signal extraction from noise, echo location, voice recognition and many others. Some of these projects require too much knowledge or too much development eﬀort to be undertaken in the present course, but the message is clear: signal processing is a core electrical engineering which is central to many design problems. Signal processing theory and practice cannot be taught in ELEC3017, for obvious reasons. Whole courses in your degree program are concerned with this body of knowledge. The advanced signal processing techniques used in many practical designs cannot be taught until the 4th year, in ELEC4042, 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 of products which communicate. Communication is not just what happens when you use your mobile phone. Internal communications within many complex systems employ sophisticated techniques. In the future, this is likely to apply even to the communication between sub-systems on a single chip. Like control and signal processing, communication theory is one of the fundamental disciplines of Electrical Engineering which is guaranteed to have enduring value and applicability. Physical communication theory and practice cannot be taught in ELEC3017, for obvious reasons. Whole courses in your degree program are concerned with this body of knowledge. 7. Software Programming Languages It is important not to draw too big a distinction between software and hardware. Most electronic products with any level of sophistication in- volve a combination of both hardware and software components. Electrical engineering design almost inevitably involves software, and most electrical engineers spend at least some of their time programming. Control, signal processing or communication algorithms designed by electrical engineers are implemented ﬁrst in software, both for veriﬁcation and often also for
c°Taubman, 2006 ELEC3017: Framework for Design Page 9 consumer deployment. Over time, increasing portions of the design might be ported to dedicated hardware, ﬁrst to FPGA’s and then maybe to an ASIC, so as to drive down manufacturing costs, increase speed and/or decrease power consumption. One rule of thumb is that moving a com- putationally expensive process from a general purpose CPU or DSP to an FPGA 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 to ASIC may bring a further 50-fold gain. The corresponding development eﬀort, however, may be enormous. Complex designs realized through FPGA’s, ASIC’s, or a combination of both, normally include embedded CPU’s which must be programmed. At the other end of the scale, microcontrollers are stand-alone processors which are designed to realize complete systems with as few components as possible, by including common I/O hardware on the same chip. Whether the processor is embedded in a piece of hardware, a microcontroller, or the general purpose CPU in a desktop PC, programming is an essential skill 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 only two formal programming courses, but you should endeavour to augment these skills by taking programming assignments and laboratory exercises in other courses very seriously. You should also approach programming aspects of any 4th year thesis project that you undertake as an opportunity to 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 hardware description languages such as Verilog or VHDL. Hardware description languages cannot be taught in ELEC3017, but you should consider acquiring this valuable skill to round out your capabilities as a design engineer. 9. Manufacturing Processes Successful design cannot be carried out in isolation, without an awareness of the manufacturing processes that will be used to manufacture the de- signed product. The sequential approach of ﬁrst designing a product and then handing it on to manufacturing engineers to “tweak things” for ease of manufacturing has been abandoned long ago. The sequential approach takes too long, costs to much, and may produce designs which simply can- not be manufactured. Concurrent engineering is the term used to describe the integration of manufacturing considerations during product design. In this course, you will be introduced to some of the relevant manufacturing
c°Taubman, 2006 ELEC3017: Framework for Design Page 10 considerations (see Chapter 12). You will also be required to incorporate manufacturing 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 in electrical engineering are the subject of an entire course in the 4th year of your program and a condition of accreditation by the Australian Institute of Engineers.2.4 Design Business Strategy 1. Regulatory and industry standards Some standards are the subject of government regulation so that being aware of their existence and following their stipulation becomes a matter of law. The majority of standards are created by industry representatives, usually in open fora, but sometimes in closed consortia. These standards govern the way in which products should be designed so as to success- fully interoperate with each other. Customers should be unwilling to buy products 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 held by others can prevent you from designing and marketing products which incorporate the protected ideas, regardless of whether or not you come up with the ideas independently. By the same token, maintaining a patent portfolio of your own can be an important business strategy. You cannot aﬀord to be ignorant of patents and how they work. Chapter 16 is devoted to 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 there is a lot more to good technical writing. Technical writing also plays an important 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 not something you were born with. This is a slightly less important skill than
c°Taubman, 2006 ELEC3017: Framework for Design Page 11 Table 1: Topics taught in ELEC3017 Topic Week Most relevant design phases Marketing (tools) 2 needs + requirements analysis Concept generation (phase) 2 concept generation System design (phase) 3 system design Project management (tools) 3 all Electronic components (knowledge) 3-4 detailed design Circuit ideas (knowledge) 4 detailed design EM compatibility (EMC) 4-5 detailed design + testing Prototyping methods (tools) 5 prototyping Speciﬁcations and testing (phases) 5 speciﬁcations analysis + testing Safe design (knowledge) 6 detailed design Technical writing (communication) 6 all Costing and economics (tools) 6 detailed design Quality assurance (tools) 7 all Standards (strategy) 7 detailed design + testing Intellectual property (strategy) 7 concept generation + system design Manufacturing (knowledge) 8 system design + detailed design Systems engineering (tools) 8 detailed design PCB design (tools) 9 detailed design Mechanical drawing (tools) 10-11 detailed design Oral presentations (communication) 12-13 all technical writing, but still deserves some signiﬁcant attention. Conﬁdence in your own understanding of the design problem and your design solution are 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 taughtin ELEC3017 and the design phases to which they are most relevant. As foryour formal written lecture notes, the topics covered should be as follows2 . 2 We say “should be” because these lecture notes are still being written.