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Proceedings of IDETC/CIE 2009 ASME 2009 International Design Engineering Technical Conference
& Computers and Information in Engineering Conference August 30-September 2, San Diego, California, USA
DETC2009-87507
REPRESENTING USER ACTIVITY AND PRODUCT FUNCTION FOR UNIVERSAL DESIGN
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ABSTRACT This paper presents a product analysis framework to
improve universal design research and practice. Seventeen
percent of the US population has some form of a disability.
Nevertheless, many companies are unfamiliar with approaches
to achieving universal design. A key element of the framework
is the combination of activity diagrams and functional models.
The framework is applied in the analysis of 20 pairs of products
that satisfy a common high level need but differ with one
product intended for fully able users and the other intended for
persons with some disability or reduced functioning. Discoveries
based on the analysis include the observation that differences in
typical and universal products can be categorized functionally,
morphologically, or parametrically different than typical
products. Additionally, simple products appear to be made more
accessible through parametric changes whereas more complex
products require functional additions and changes. 1
1. INTRODUCTION Seventeen percent of the US population has some form of a
disability. Additionally, a high percentage of people with
disabilities have a negative impact on their education and
working environment as a result of their disability. Roughly
two in five people with disabilities do not even finish high
school. Even if they obtain a post secondary degree, disabled
people often face some form of discrimination at work [1]. As
persons age, the probability of them developing a disability
increases. As life expectancy rises, a greater percentage of the
population will have some form of disability [2].
Universal designs are needed across the entire product
spectrum. Two examples of successful companies that have
implemented universal design concepts are O.X.O and Toyota.
Initially, O.X.O designed their Good Grip product-line as a line
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of kitchen tools with comfortable grips easily accessible to
arthritic customers [3]. In subsequent years, the market segment
shifted to younger users interested in cooking with
ergonomically friendly peelers, bottle openers and other
cooking utensils. As a result, the O.X.O Good Grips products
are an oft-cited example of a universal product success. An
example of a vegetable peeler from the Good Grips line is
shown in Figure 1.
Figure 1.O.X.O Good Grip Serrated Vegetable Peeler.
The Universal Design showcase in Japan highlights
universal design concepts [4]. Figure 2 shows an example from
an exercise in which universal design was implemented from
the ground up while developing minivans and sedans. For
instance, the chairs, knob placement, and trunk configurations
are all designed to be universal as stock items rather than after
market add-ons. For example, the Toyota Crown Comfort has a
mechanical handle that will pull out and swivel a rear seat
towards the entering passenger as shown in Figure 2.
It is worth noting that aside from this pull out handle, the
configuration of the seat is very similar to any other sedan.
Though there is additional design effort needed to design this
universal seat, that material and manufacturing costs would
Vincent Kostovich, Daniel A. McAdams1, and Seung Ki Moon
Department of Mechanical Engineering Texas A&M University
College Station, TX 77843, USA
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likely only be marginally higher than a typical seat. An
advantage of including these features early in the design
process and integrating them in a universal product is the
avoidance of the high costs of retrofitting the vehicle later for
disabled users. Though seemingly simple to execute, these
examples of successful universal design serve as exceptions,
not the rule.
Figure 2.Toyota Crown Comfort Swivel Chair
Sequence [5].
As the population of persons with a disability grows, so
does the ethical and economic pressure to provide that
population with products that provide services and value.
Nevertheless, many companies are unfamiliar with approaches
to applying universal design. One of the authors of this article
had a recent conversation with a research engineer from a large
consumer electronics manufacturing firm in which he asked:
“What is your biggest design challenge?” The response was
simple: “Universal design, how do you do it?”
Before continuing, it is worth briefly touching on
terminology. Within the community that serves persons with
disabilities, multiple terms are used, including universal design,
accessible design, inclusive design, design for all,
transgenerational design, rehabilitation design, and barrier free
design, to indicate goods and services for persons with
disabilities. Below, we do present some clarification on the
relationship between these different types of design for persons
with a disability. Nevertheless, there is ongoing discussion
about the precise meanings, overlap, and best use of the terms.
Though these discussions have philosophical and practical
importance, they are not crucial to the discussion here. With
awareness that at times one of the other terms would be more
accurate, we will use the term universal design here to indicate
design for persons with disabilities.
In a United Kingdom study of 87 design, manufacturing,
and retail sector companies, existing barriers to universal
design were explored [6]. Initially, these barriers were
evaluated based on the companies’ general awareness of
universal design. When asked why the designer, or company,
didn’t perform universal design, ‘not aware’ was the most
frequent response. Furthermore, for those ‘not aware’ the most
popular answer was lack of knowledge and tools creating a
barrier to implementing universal design. For those
participants who were ‘extremely aware’ of the concept of
universal design, their most common answer was thinking that
universal design is too hard to implement.
Clearly, a key barrier to universal design is lack of
knowledge about its practice and what tools can be used to
develop a universal product. While these barriers do exist,
there are companies and products that have achieved success
while implementing strategies to achieve universal products. In
addition, there are principles and rules developed by
researchers and companies explaining what a universal product
does. However, there remain significant knowledge gaps that
would allow universal design to be implemented broadly in
product design.
In this paper, we present a framework for performing
research that enables an understanding of product differences in
the context of universal design. Additionally, the framework
allows for the recognition of these differences early in the
design process. The focus is on the early recognition of
differences and commonalities in typical and universal products
to recognize opportunities for product families that contain both
typical and universal products.
The remainder of this paper is organized as follows.
Section 2 reviews related literature and background. Section 3
describes the research approach and method for supporting
universal design. Section 4 discusses a case study comparison
of twenty product pairs of typical and universal products. In
Section 5, conclusions and future work are presented.
2. LITERATURE REVIEW AND BACKGROUND Universal design has many closely related types of design.
For example, transgenerational design focuses on design for
older people and rehabilitation design focuses on design for
those with a new or temporary disability. Transgenerational and
rehabilitation design are closely related as they focus on a
specific segment of the population that requires the easiest
means of using a product. This ease of use idea is similar to
principles of universal design [7-9]. There are also existing
typical and universal design methods that have been
documented and explained [10, 11].
2.1 Motivation for Universal Design A universal design is a design that can be used equally as
well by people of any ability: it does not discriminate against
users based on their ability. Accessible design is another term
used for describing design for persons with a disability.
Accessible design is frequently used to describe specific
modifications of typical designs for someone with a disability
such as the addition of a ramp entry to a building. Adaptable
design can also be universal in the sense that it changes an
existing product by merely modifying a part or component to
make it easier to use [12]. As a result, the stigma of using an
accessible or adaptable product may still be prevalent despite
its ease of use. Figure 3 below shows how accessible,
universal, and adaptable designs vary across the design space
[12].
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Figure 3.Design Venn Diagram-Overlap shows
designs that are in more than one category [12].
As shown in Figure 3, there is an opportunity to create a
universal design from more commonplace adaptable or general
designs. However, as a designer, there is a tendency to focus on
adaptable or merely general designs because of cost, market or
time constraints. These constraints are associated with product
assessment techniques and are believed to be the most common
problem with universal design because of extra design steps
[13]. In addition, it is often the lack of education and tooling
that prevents a company from reaching the overlapping areas of
universal design. Companies desire a quick, visual, and an easy
to understand tool with associated product examples and case
studies in order to feel more comfortable implementing
universal design techniques. Designers want to know how to
use the plethora of information about universal design in a
more systematic way [14].
Designers are frequently unaware of differing customer
preferences of those with different physical and mental
disabilities. The designer is uncertain how to incorporate
universal design into the design process [15]. Moreover,
designers tend to work reactively rather than proactively. For
instance, a designer may react to a definite set of customer
needs and focus on satisfying them. In the case of universal
design, a designer should proactively focus on the product’s
capabilities and ability to work with a variety of consumers
[16]. Reactive design focuses more on redesigning a specific
part of an existing device to satisfy a customer. However, if the
user is redefined at the front end of the design process, the
designer will produce a more universal product.
One aspect that delays the development of methods for
universal design is discussion of the interpretation of the
meaning as well as the general challenge of designing for those
with a disability. For example, designs that either focus too
much on specific market segments such as transgenerational
design are sometimes criticized for their shortcoming rather
than being celebrated for what they can do. Transgenerational
design theory describes how older adults are the focus for
design often misinterpreted as universal [7]. People may also
get this type of design confused with rehabilitation design
dealing with impairments. Even cultural interpretations of how
to tackle universal design make it a less ubiquitous method.
For instance, Europe has a method called the User Pyramid
Approach [17] whereas the US, Japan and Australia focus on
universal design as expressed by the terminology used in the
introduction of this paper [18].
2.2 Universal Design Methods More comprehensive summaries of universal design can be
found in The Universal Design Handbook [19], Fisk and
Rogers [20], and Salvendy [21]. The research approach
proposed here builds on recent developments from the
universal design, engineering design, and health communities.
The review of related work is focused as such.
The landscape of universal design literature is vast and
contains significant coverage of historical and social context.
As an example, of the sixty-two chapters in The Universal
Design Handbook, fifty-two chapters have significant coverage
focused on the history of universal design, the rationale behind
it, legal issues, documentation of workshops, or similar.
Notably, about twenty-four chapters provide descriptive
guidelines and quantitative requirements for universal
architectural design. Only about seven chapters contain
guidelines, case studies, or other content that provides some
insight into universal product design. The volume and emphasis
of universal design research publication mirrors the coverage in
The Universal Design Handbook.
Though universal design of architecture is not a solved
problem, there is a large and high quality set of resources
available for architectural design [22-27]. The materials
available include qualitative guidelines as well as quantitative
parametric guidelines such as room layouts, counter heights,
dimensional requirements for appropriate sight lines in large
classrooms, and etc. The available guidance for universal
architectural design far surpasses what is available for universal
product design.
A team of researchers organized through The Center for
Universal Design at North Carolina State University has
compiled seven principles of universal design [9]. The seven
principles are: 1. equitable use, 2. flexibility in use, 3. simple
and intuitive use, 4. perceptible information, 5. tolerance for
error, 6. low physical effort, and 7. size and space for approach
and use. For each principle, several guidelines have been
created. For example, principle 6 has a guideline of “minimize
repetitive actions.” These principles have been well received by
designers in a range of disciplines.
Though the seven principles of universal design provide
high-level guidance, they provide more of an evaluation aid
than a design or synthesis aid for product design. Continuing
with principle 6 as the example, products need to be designed
for low physical effort. Minimizing repetitive actions helps
with reducing effort, but how does one design a product to
minimize repetitive actions and require low physical effort?
Also, as stated by the compilers of the seven principles: “…the
practice of design involves more than consideration for
usability. Designers must also incorporate other considerations
such as economic, engineering, cultural, gender, and
environmental concerns in their design processes [9].”
Another set of design principles and guidelines for product
design focuses more on functions of a product and how to
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fulfill these guidelines in order to cover as many disabilities a
possible. The five function areas are: output/displays,
input/controls, manipulations, documentation, and safety. For
each function area, five disabilities are addressed by stating
problems and example solutions [28]. To take this approach
one step further, another means for evaluating the universality
of a product is by associating exclusion scores for various
human attributes. If the score is low, a user with a disability
similar to one of the five function areas addressed in the
previous approach will have difficulty using the device. This
product assessment method includes: product description,
context of use, sequence of use, capability, score and
justification [29].
Keates proposed a seven-step approach for universal
design by modifying the traditional three-step [11]. As shown in
Figure 4, the first two levels of the seven-step approach parallel
the first two into a traditional design method to make it
universal. Level 3 describes user’s perception of the product or
how the physical layout of the product affects the user
interaction. Often anthropometric, ergonomic and empirical
data from trials are needed to complete design at this level.
Level 4 focuses on the user’s mental or cognitive interaction.
Cognitive walkthroughs are used to correlate user system
behavior to user expectations. Thirdly, level 5 focuses on user
input or interaction with the product and relies on similar
techniques as those used at level 3 to address design at this
level [30].
Vanderheiden has developed a set of guidelines for the
design of consumer products [28]. Some of these guidelines are
useful only for evaluation. Others include suggestions that
augment product synthesis. For example, guideline I-2 is
maximize the number of people who can find the individual
controls or keys if they can’t see them. To help synthesize a
solution that achieves such a goal, this guideline includes
suggestions for shapes of computer keyboard keys (or similar)
that will allow someone with a sight limitation to locate the
correct key. The guidelines and suggestions tend to be focused
on products surrounding electronic communication or
information technology but should be extendable to product
design in general.
Housed in the Center for Inclusive Design and
Environmental Access at the University of Buffalo is an active
group of researchers with focus on universal design [31-34].
Though this group is focused on architectural design and comes
from an architectural background, they have performed
research on appliances and other applications that extend to
product design.
A team of researchers at the University of Cambridge has
produced implementable results for universal design [35-40].
The focus of this research group has been in modeling user
groups, creating product assessment methods, and extending
the needs of universal design to modern product design
processes. The results of the Cambridge team are the most
directly applicable to product design. Their effort has been
primarily focused on the user and the design challenges of
accommodating that user.
Figure 4. The 7-level design approach [11]
Universal design is an active research area. Nevertheless,
fundamental work applicable to product design is still a
sparsely populated space. Universal design is more of an
objective than a systematic design approach. There is little in
the way of a prescriptive approach to universal design with
more detail than simply broad design objectives [41].
Additionally, though creating modular products that minimize
modification to become universal is a recognized approach to
universal design, specific knowledge and methods to do it do
not exist [40].
3. PRODUCT ANALYSIS FRAMEWORK AND RESEARCH APROACH
Our interest is early in the design effort where product
function is being established and solution concepts are being
generated to provide that function. Our goal is to understand the
differences and similarities in typical and universal products
and being able to do so early in the design effort. Though
beyond the scope of the work presented here, this interest is
related to a future goal of creating product families that include
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typical and universal products built on some common product
platform. Thus, understanding the relationship between user
activity, disability, and common and differing product
characteristics is important.
Here we develop an analysis framework that allows the
comparison of two products that fulfill the same overall need.
The comparison is focused on the result of decisions that are
made early in the design process, i.e. what functions must the
product have and what is the form and characteristic of the
solution that will best provide that functionality. The
framework and analysis method are illustrated with an example.
3.1 Product Analysis Framework
We will use the term product pair to refer to two products
that satisfy the same high level need or provide the same
overall black box functionality but differ in ease of use for
someone with a disability [42]. Figure 5 illustrates a product
pair of utility cutters. The Fiskars Rotary Cutter and the typical
box cutter provide similar paper and cardboard cutting but the
Fiskars Rotary cutter has features that make it preferable for
users with reduced hand functioning.
Figure 5. A product pair of a Fiskars Rotary Cutter
(above) and standard box cutter (below) As product pairs are analyzed, we want to compare them in
terms of attributes crucial to making the product accessible and
relevant to decisions that are made early in the design. Thus, we
will compare product pairs based on differences in
functionality, morphology, and parametric realization.
A Functional Difference reflects the situation in
which the typical and universal product have differing
functionality particularly as it pertains to the making the
universal product more accessible. As an example, some
signage adds the function of “export tactile signal” embodied as
Braille lettering to become accessible to an unsighted user. A
Morphological Difference refers to a product pair that has the
same detailed functionality but the typical and universal
product solve said functionality via a different solution
principal or form. For example, an “allow a degree of freedom”
function could be solved by either a mechanical linkage or
springs. Both the linkage and the spring provide a similar
motion but their component makeup is different. A parametric
difference indicates the case in which the universal and typical
product have the same functionality, solve the required
functionality through essentially the same solution principle
and form, but have a different parametric embodiment. For
example, the handgrip of an object could be bigger or more
ergonomically designed as exemplified by the O.X.O Good
Grip vegetable peeler shown in Figure 1.
Based on the notions of product pairs, functional
differences, morphological differences, and parametric
differences, we want to compare product pairs in the context of
user activity and product function. To do this, we combine
activity diagrams and functional models into a single
representation that we will term an actionfunction diagram.
Before introducing the actionfunction diagram, activity
diagrams and functional models are briefly reviewed.
An activity diagram is a sequence of user interactions from
purchase to recycling or disposal [10]. This sequence may
include parallel or series actions. A series of actions implies
that one action must occur before another. Whereas, a parallel
action implies that two actions occur simultaneously. Activity
diagrams model the entire range of user product interaction to
better design the product for each user activity. An example
activity diagram for a typical box cutter is shown in Figure
68.The activity diagram shows the user interaction process
from purchasing and unpacking the cutters to cutting cardboard
with them.
Figure 6. An example of an activity diagram for box or
paper cutter
A functional model is a graphical depiction of detailed
product functionality. Functional models include functions,
generally represented as verbs, which describe the desired
transformations of flows, which are generally described using
nouns. The process for creating a functional model depends on
the modeling methodology chosen but in general involves the
following basic steps:
1. Create a black-box model that includes the overall
functionality of the product along with external flows,
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2. For each input flow in the black-box model identify
the sequence of functional transformations that are
required to produce one or more of the output flows,
3. Aggregate these function sequences into a complete
functional model for the product,
4. Assess the model’s coverage of customer needs and
system requirements, add functions/flows or
decompose as required.
A range of reasons for creating a functional model during
product design are detailed by Otto and Wood [10]. In general,
the primary reason is to create a solution-neutral method of
representing what a product needs to do without assuming how
it is going to do it. This mapping of what to how represents the
remainder of the conceptual design process.
Frequently, functional models use function and flow
terminology from the Functional Basis in order to maintain
consistency from one product to another [42]. A functional
model for a standard box cutter intended for a typical user is
shown in Figure 7.
Figure 7. A Functional model for standard box cutter
An actionfunction diagram is the combination of an
activity diagram and a functional model together into a single
representation. Figure 8 shows a template for the actionfunction
diagram. In an actionfunction diagram user activities are
represented by dashed rectangles with related functions
clustered within each activity.
Figure 8. Generic template for an actionfunction diagram
Specifically with the goal of understanding the design
differences between universal and typical products,
actionfunction diagrams include an indication of the differences
between the typical and universal products being compared as
well as the user activities and product functions. Different
product functionality is indicated by a bold-lined function box.
Common product function but different morphology is
indicated with a double lined function. Common product
function and morphology with different parametric
implementation is indicated with a shaded function box. Where
the typical and accessible or universal products are the same is
indicated with a standard function box.
3.2 Research Approach Figure 9 illustrates the steps used to explore differences
between typical and universal products. For each product pair, a
common activity diagram is constructed, then a functional
model is made for the both the typical and universal products,
then the functional models and specific products are compared.
The activities are performed using tabular comparisons of the
actionfunction diagrams to highlight the differences and
similarities between the product pair. A template table is shown
in Table 3.
Figure 9.Outline for Visual Analysis
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Table 3. Product Pair Actionfunction Diagram Template
Typical Product Universal Product
The products are carefully analyzed in terms of differences
as it pertains to improved usage for a user with a disability or
reduced functioning. Specific focus is placed on how the
products do or don’t implement the principles of universal
design. If impact of a design difference on usage is not clear,
both products are acquired and used to perform a physical
testing comparison.
We illustrate the design and analysis framework and
approach through an example of a paper and cardboard cutter
product pair, in this case the Fiskars rotary cutter and standard
box cutter as shown in Figure 7. Both products provide the
same overall usage of cutting but are different in their
embodiment.
To start, the rotary cutter has a more ergonomic handle. In
this example, the handle which provides the secure hand
function is based on the same basic principle, but was shaped
differently, specifically more ergonomically, for the universal
cutter. Thus, this difference is shown as a parametric change in
the actionfunction comparison shown in Table 4.
The rotary cutter has a circular blade with a guard whereas
the standard box cutter has a retractable angled blade. The
difference in blade shape and motion impacted the effort
needed to cut. The rotation of the circular blade naturally added
a little sawing motion to the material-blade interface reducing
the total pushing force needed to cut paper and cardboard as the
user pulled the cutter across paper or cardboard. Also, the
rotary cutter can cut with a pushing away motion by the user
whereas the traditional utility knife only works well with a
pulling toward the user motion. This is a morphological
difference as rotating is a different principle for cutting than
just pulling the blade through the material to be cut. The
actionfunction diagram shown in Figure 4 represents this
morphological difference in the solution of the convert human
to mechanical energy function.
The blade extension and retraction design of the cutters is
significantly different. There are two switches to lock and
unlock the blade for the rotary cutter whereas only one switch
is for both extending and retracting the blade for the standard
box cutter. In the case of the rotary cutter, the blade extensions
and retraction switches are both activated with a simple pushing
in, or pushing down, motions on a single axis of travel. The
blade on the rotary cutter is spring loaded to snap back into
place when the retraction switch is pushed. For the traditional
utility knife, the user pushes the switch into the knife to release
a lock, then forward along the length of the knife to extract the
blade. The simple pushing in is easier then the push in then
push forward motion. Additionally, the actual force to push the
switches on the rotary cutter was less then the force needed to
either push in or forward on the utility knife.
Both the typical utility knife and the rotary cutter provide
the function of transferring human energy into the device to
move the blade. The difference is categorized as morphological
as there is not clear parametric representation that encompasses
both concepts.
The differences between the product pair are shown in the
actionfunction comparison in Table 4.
Table 4. Actionfunction product pair comparison for the standard utility cutter and the Fiskars rotary style cutter. Shown here in a single column for readability.
An actionfunction diagram of a typical utility cutter.
An actionfunction diagram of the Fiskars rotary cutter.
4. CASE STUDY AND RESULTS Twenty product pairs ranging from automobile interiors to
scissors are compared in this study. Products marketed or
generally accepted as universal or accessible are chosen along
with similar typical products to form the product pair. Most of
the products are handheld kitchen utensils. However, products
such as a typical recliner and universal chair lift and
automobiles are included. The vehicle product pairs have
modification to improve user egress and ingress accessibility.
Appendix A shows a table of the twenty products studied. As
with the paper and cardboard cutter product pair analyzed
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above, a comparison using the actionfunction diagram and
experimentation is performed on each product pair. Results are
summarized and discussed here.
In the study of products, the user activities associated with
some parametric, morphological, or functional difference in the
product pair are adjust, apply force, drive, exit, grab, position,
press, remove, speak, squeeze, touch, translate, transport, and
use human force. These differences occurred primarily where
direct contact with the product took place and are primarily
relevant to reduced hand strength and motor functioning.
The user activities for which there is no associated
difference in the product pairs studied are approach, attach,
connect, demolish, dispose, drive, exit, insert, install, look,
program, purchase, read instructions, recycle, release, replace,
retract, return, sell, stand, start, store, stop, twist (turn),
unpackage, wait, and walk. These activities generally occur
early or late in the product life cycle.
These results appear to be based on what has been done in
universal design practice as opposed to a fundamental result of
what needs to be done in a broad and general context. Such a
result is consistent with the sample size of the study and the
challenge and complexities of universal design. Also, during
the study the author team noticed that though some activities
did not relate to design differences, they should have been. For
example, the product pair solutions for the activities of read
instructions and unpackage were effectively equivalent for
product pairs. Nevertheless, the instructions were not always
particularly accessible to someone with reduced vision
functioning. Similarly, the heavy plastic blister packs that many
of the products came packaged in are difficult to open for a user
with reduced hand strength and motor function.
Table 5 shows the specific type of design change correlated
with each specific activity. Complex activities of drive and
speak result in a more comprehensive change (function).
Simple activities such as grab, position, press, result in less
comprehensive change. Based on the product pairs studied, no
specific conclusions on trends of what activities are related to
what specific types of changes can be drawn.
Table 6 indicates which functions did not feature a
parametric or morphological difference nor were they a
functional difference in a product pair. Many of the functions
were import or convert functions. In general, these functions
are internal to the functional model. Though, this is not always
so as exemplified by the position hand and guide hand
functions.
Table 7 summarizes the parametric, morphological, and
functional differences between universal and typical products
analyzed. The percentage difference reflects the changes in the
product at a functional level. For example, a parametric change
in 1 function out of a total of 10 functions in a product would
result in a 10% parametric change. The measure uses the
typical product functionality as a base for comparison thus
enabling for greater than 100% change. For example, the
typical recliner only had four functions. The universal recliner
added 9 additional functions thus resulting in a 225% functional
difference.
75% of the products had a parametric difference, 50% of
the products had a morphological difference, and 65% of the
products featured a functional difference. For all 20 products,
the average parametric difference is 8%, the average
morphological difference is 6%, and the average functional
difference is almost 50%.
Table 5. Activity and Design Changes Activity Parametric Morphological Function
Adjust X
Apply force X
Drive X
Exit X
Grab X
Position X
Press X
Remove X
Speak X
Squeeze X
Touch X
Translate X
Transport X
Use Human Force X
Table 6. Functions not related to any product pair design difference.
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! ! "#$%&'()*!+!,--.!/%!0123!.!
Table 7. A summary of difference between the typical and universal products analyzed.
The fact that the average functional differences is about six
times greater than parametric or morphological differences
indicates that universal design needs to be considered early in
the design process. Product function drives many early design
decisions including product architecture. Parametric redesigns
are often cost effective. Changing product function is a more
complex and expensive task.
Of the products studied, simple products feature less
functional change than complex products. For example, the
cheese grater, bottle opener, potato masher, food container, and
jar opener use parametric changes to be more accessible. By
contrast, the sink, can opener, and recliner contain significant
functional changes. The universal products adding
functionality are often adding functionality that the user
provides for the typical product. For example, the can opener
adds a motor to prove the cutting motion and torque that the
user provides with a typical can opener. Similarly, the recliner
adds functionality that essentially stands the user up.
5. CONCLUSIONS AND FUTURE WORK In this paper we explored the relationship between user
activity, product function, and product form as it pertains to
differences in typical and universal products. Specifically, we
explored a research framework that uses the formal design
methods of activity diagrams and functional models. We
combined these methods into a single graphical representation
called an actionfunction diagram that allows the user to see
functional, morphological, and parametric differences between
a typical and universal product that provide the same overall
use. Using this approach, 20 products were studied to
understand the trends in function, morphological, and
parametric differences in typical and universal products that
provide the same overall usage.
The actionfunction diagram provided a clear, repeatable
framework for analyzing products for differences as it pertains
to typical and universal products. Though used in this study as a
research framework, the actionfunction diagram framework is
applicable to design activities. The actionfunction diagram
clusters product functions as they relate to user activity, thus the
designer can identify activities, and user limitations, for which
a product needs specific function, morphological, or parametric
embodiment.
Within the products studied, the majority of differences
between universal and typical products are related to user hand
manipulation of the product. Functions that are internal to the
product (those that do not have an exciting or entering flow that
crosses the product boundary) generally remain the same for
the product pairs studied. Additionally, boundary functions not
related to human flows generally remained unchanged.
Universal design remains a challenge. Toward the goal of
creating a fundamental framework for universal product family
design, many questions remain. A deeper understanding of
classes of products, classes of functions, classes of user
limitation, and the interaction between them needs to be
discovered so that designers can reason about integrating
product functions and features into a universal product family.
Using the framework developed here, further study can reveal
what functions are common across a range of typical and
universal products. With this knowledge, designers can extend
current product family design methods to create universal
product families that share these common elements as the
product platform and extend to a product family with the
unique elements.
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41
AppendixA. Twenty Universal Products
