Even prescriptive descriptions of design processes can fail us because they don’t tell us how to generate or create designs, or even how to do some of the tasks specified. In this section we describe some ways of thinking about design, after which we list some of the formal design methods that we explore in greater detail in later chapters. We then list some of the kinds and sources of design knowledge that informs what we do as designers, including: how we acquire information; how we analyze information and test outcomes against desired results; and how we get feedback from clients, users, and other interested parties.
2.3.1 Informing a Design Process by Thinking Strategically
Strategies are ways of thinking about a problem or situation. Effective designers have habits of thought they bring to their work that help them realize better decisions. Least commitment is one general strategy for thinking about design: Don’t make decisions before you have to. This is a good habit of thought that guards against making decisions before there is a reason to make them. Premature commitments can be dangerous because we might become attached to a bad concept or we might limit ourselves to a suboptimal range of design choices. Least commitment is of particular importance in conceptual design because the consequences of any early design decision are likely to be propagated far down the line. It is generally unwise to commit to a particular concept or configuration until we are forced to because we’ve exhausted our information or range of choices or time available.
Decomposition, also known as divide and conquer, is another important habit of good design thinking: Break down, subdivide, or decompose larger problems into smaller subproblems. These smaller subproblems are usually easier to solve or otherwise handle. We do have to keep in mind that subproblems can interact, so we must ensure that the solutions to particular subproblems do not violate the assumptions or constraints of complementary subproblems.
2.3.2 Informing a Design Process with Formal Design Methods
Usually, when we think systematically about doing things, we can develop tools and techniques we can use. We now present a brief introduction to the formal design methods identified in the charts by introducing some of the formal tools we will use in following the design process.
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Objectives trees are hierarchical lists of the client’s objectives or goals for the design that branch out into tree-like structures. We build objectives trees in order to clarify and better understand a client’s project statement. The objectives that designs must attain are clustered by sub-objectives and then ordered by degrees of further detail. For example, we might take an objective like “portable,” and break that down into subobjectives: “lightweight” and “small when collapsed for storage.” The highest level of abstraction of an objectives tree is the top-level design goal, derived from the client’s project statement. In Chapter 4 we explain how to construct objectives trees and explore the kinds of information we learn from them.
Pairwise comparison charts (PCCs) are used to rank order our design objectives. It is helpful, for example, to know whether it is more important to the client that our ladder is “portable” or “inexpensive” in case trade-offs need to be made. A PCC is a relatively simple device in which we list the objectives as both rows and columns in a matrix or chart and then compare them on a pair-by-pair basis, proceeding in a row-by-row fashion. We use PCCs early in the design process, and they are described in Section 4.4.
Metrics are created to measure how well we achieve a design’s objectives, thus allowing us to evaluate design alternatives in terms of attributes the client desires. We explain how we create metrics in Section 4.5.
Functional analysis is used to identify what a design must do. Identifying and performing functions are central to engineering design, and we will develop several approaches (e.g., black and transparent boxes, dissection, enumeration, and function– means trees) to functional analysis in Chapter 6.
The performance specification method provides support for the elaboration of the specifications that reflect, in engineering terms, how a design will function. The aim is to list solution-independent attributes and performance specifications (i.e., “hard numbers”) that specify the requirements of a design concept. We describe performance specifications (requirements) and their role in Section 6.2.
Morphological charts are used to identify the ways or means that can be used to make function(s) happen. Such “morph charts” express functions as verb–noun action pairs; the means are specific ways to use or convert energy, or to process information and/or materials. For example, if one of our ladder functions is to stabilize the user over uneven terrain, we could realize that by having adjustable feet, or by having a wide base. The morph chart provides a framework of the design space, an imaginary “space” that we can use to generate potential design alternatives for a design problem. We describe morph charts in Chapter 6.
2.3.3 Acquiring Design Knowledge to Inform a Design Process
The literature review is the classic way to find examples of prior work and determine the state of the art. We need literature reviews early on, in the framing and conceptual stages, to better understand the client, potential users, and the design problem itself. We should consider existing solutions, because there’s little point or profit in reinventing the proverbial wheel. In detailed design, we may want to review available off-the-shelf parts and materials to help standardize our design and reduce fabrication costs. So at various stages we should look at the technical literature, patent listings, vendor literature, hand- books, material properties tables, and design and legal codes.
Benchmarking competitive products means evaluating the functionality and behavior of similar products already on the market. Benchmarking is often done to set a bar for a better product.
Reverse engineering or dissection is also about “seeing what’s out there”: it consists of dissecting or taking apart competitive or similar products. It is often done to assess functional behavior with the aim of developing better means to accomplish the same or similar functions.
Informal interviews of potential users should be undertaken very early in a design project to assist in problem definition. While informal interviews are relatively easy to conduct, it is important to be sensitive to the time and other constraints of the interviewees by preparing for the interviews, for example, provide the interviewees with advance lists of the topics and questions, and complete a significant part of the literature research before conducting those interviews.
User surveys and questionnaires are used in market research to identify users’ views of the problem space and their response to possible solutions. Market research can help clarify a design problem in its early stages, especially with open-ended questions. Later surveys can be used together with PCCs and morph charts to help select a final design. A structured interview melds the consistency of surveys with the flexibility of informal interviews by using a previously defined set of questions that may or may not be made available to the interviewees. An interviewer can follow up a particular response and open up new areas. A structured set of questions also assures the interviewee that the interview has both purpose and focus, and it provides an agenda that ensures that key matters will be covered.
Focus groups are an expensive way to elicit the response of appropriately selected users and others to potential designs. They are not often used by student design teams because they demand considerable sophistication in psychological matters and are expensive.
Structured brainstorming by a design team can also generate ideas and insights, and in opening up new avenues for research and analysis. However, productive brainstorming is a complex activity that requires thought, preparation, and appropriate professional behavior.
2.3.4 Informing a Design Process with Analysis and Testing
We can’t know whether or not a design concept might work unless we can measure outcomes, and we can’t measure outcomes without having a metric or a standard against which to measure those outcomes. While metric is a general term meaning a frame or ruler for measurement, we will specifically use the term metrics to measure how well a design’s objectives are achieved. We will describe how we develop metrics in Section 4.4. We will also develop another set of measurements, design specifications, to state in engineering terms the functional performance of a design. This is an extremely important topic that we will discuss in depth in Sections 6.2 and 7.3.
Experiments and testing are often used to get data, in the field or in a lab, about how well potential design actually works. Testing can run the gamut from component testing to proof-of-concept testing, to prototype development, and testing. We will say a good bit more about such testing in Chapter 11.
In many cases we don’t develop or test a prototype, perhaps due to cost, size, or hazards. In such cases, we may resort to simulation in which we exercise an analytical or
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computer model of a proposed design to simulate its performance under a stated set of conditions. However, we can only do that if we really understand the device we’re modeling and its true operating conditions. With such deep understanding, we can get useful data from simulation that will enable us to evaluate against constraints, specifica- tions, and any applicable standards. One outstanding example of such simulation is the use of wind tunnels and related computer analyses to assess the effects of wind loading on tall buildings, on long, slender suspension bridges and, of course, airplanes.
Computer analysis is closely related to simulation and uses computer-based models, typically discipline-specific, to analyze design components in preliminary and detailed design. Such computer analyses include finite element analysis, integrated circuit model- ing, failure mode analysis, and criticality analysis.
2.3.5 Getting Feedback to Inform a Design Process
We noted earlier that feedback was an intimate part of design: We use internal feedback to verify that we’re solving our design problem correctly, and external feedback to validate that our design has solved the right problem.
Regularly scheduled meetings, at which the progress of the design project is tracked and discussed, may be the most important means for obtaining feedback from clients and other members of the design team.
Formal design reviews, held at specified intervals, are a standard “best practice.” We use them to update the client (and sometimes others) on the design status, typically including sufficient technical detail that the implications of the design can be explored and assessed. Design reviews involve a lot of “give and take” between the design team and its audience, and thus may seem harsh to young designers. A design team usually benefits by having to justify various technical details to clients and outside experts because its members become more aware of implicit unwarranted assumptions and errors or oversights.
In some design environments, public hearings are required by relevant civil laws or public policies in order to subject a design to public review and comment. Public hearings and meetings are increasingly the norm for major design projects (e.g., transportation or power projects), even when the client is a private entity.
We have already noted that focus groups are important sources of user input for problem definition. Such groups are also widely used to assess user reaction to designs as they near adoption and marketing.
Similarly, in industries like software design, an almost-but-not-quite-finished version of a product is released to a small number of users for beta testing. Beta tests allow designers to expose design or implementation errors and to get feedback about their product before it reaches a larger market.