A task based ‘design for all’ support tool

Robotics and Computer Integrated Manufacturing 18 (2002) 297–303

A task based ‘design for all’ support tool

R. Marshalla,*, K. Caseb, R. Olivera, D.E. Gyia, J.M. Portera

aDepartment of Design and Technology, Loughborough University, Loughborough, Leicestershire, LE11 3TU, UKbWolfson School of Mechanical and Manufacturing Engineering, Loughborough University, Loughborough, Leicestershire, LE11 3TU, UK

Abstract

The ‘design for all’ philosophy promotes the development of products that meet the requirements of a broader section of the

population, including those who are older or disabled, to minimise the need for bespoke designs and individual customisations. Such

an approach begins to meet the needs of a population containing an ever increasing proportion of these excluded groups, whilst

providing opportunities to manufacturers to maximise the available market for any given product.

Most design activity embodies some form of task analysis that involves identifying users and the tasks they perform. Computer

based human modelling systems are becoming increasingly important in this task analysis role combined with the established

ergonomics technique of fitting trials, in which a product or environment is evaluated through trials using a carefully selected user

group.

This research addresses the lack of existing data necessary for the accurate representation of human form and capability in the

older and disabled populations for use in these modelling systems. A small-scale survey is being undertaken to collect this important

information. In addition, existing modelling systems in this area rely on expert ergonomics knowledge in performing task based

analysis, which in addition can be a time consuming and repetitive task. Methods are being developed to streamline this process and

to place the emphasis on good design and ergonomics principles as opposed to ‘driving’ the system. These methods involve the

development of a simplified process for computer based task analysis and a means of determining the percentage accommodated by

any given design.

Further research will eventually focus on extending the data collection, refining the task model and look at a means of suggesting

design solutions in response to the analysis results. r 2002 Elsevier Science Ltd. All rights reserved.

Keywords: Design; Ergonomics; CAD

1. Introduction

It is reported that by the year 2005, there will be 10million older and disabled people in Europe alone, some25% of the total European Population, [1]. With such achange in demographics, it is becoming essential thatdesigners address the requirements of this increasingproportion of the population and have access toinformation on the anthropometry and capabilities ofthe whole population of people who may wish tointeract with the design in question. However, it is wellknown that products are not always designed to includethe growing needs of the growing numbers of thesegroups [2].The ‘design for all’ (DFAll) philosophy aims to

educate designers in the importance, both socially and

economically, of accommodating this increasing popu-lation. DFAll promotes a holistic approach focussed onproduct accessibility and usability aimed at providingproducts that meet the requirements of a largerproportion of the population. Such products wouldincorporate features that accommodate and appeal toable bodied users and those who are older or disabled,significantly reducing the need for bespoke designs andindividual customisations. It is recognised that thisobjective is ideal rather than totally achievable andinevitably there will be those relatively small groups thatwill require products that are not attractive to main-stream markets. However, increasing the accommoda-tion of diverse populations and gaining a greaterunderstanding of the reasons why some are excludedremains a major aim and forms the basis of the researchreported here.Understandably many of the requirements in this area

relate to activities of daily living (ADL). These include*Corresponding author.

E-mail address: [email protected] (R. Marshall).

0736-5845/02/$ - see front matter r 2002 Elsevier Science Ltd. All rights reserved.

PII: S 0 7 3 6 - 5 8 4 5 ( 0 2 ) 0 0 0 2 1 - 2

all the activities that define an individual’s ability tomaintain independence and thus are extremely impor-tant in a DFAll context. Despite this, studies such asAshworth et al [3], give an indication of the extent towhich people who are older or disabled experience being‘designed-out’. They report that 21% of US 65–74 yearolds and 55% of those over the age of 85 years had atleast some difficulty with ADL. It has also beensuggested that consumers are slow to complain aboutpoorly designed goods and services and tend to blametheir own loss of ability when they encounter difficulties.

1.1. Equal

The extending quality life (EQUAL) initiative wasinitiated by the UK Government’s Office of Science andTechnology in 1995 to draw together research activitiesthat bear on the extension of the active period ofpeople’s lives, thereby helping individuals to achieve abetter lifestyle and avoid or alleviate the effects ofdisability. The potential benefits are twofold: improvedhealth, a more active and better quality of life, and agreater continuing participation in society; coupled witha lighter burden on society, and the generation ofconsiderable business opportunities for UK firms toexploit in global markets. Although benefits will accrueto all, the main drivers for the initiative are the needs ofan ageing population, and the needs of people withdisabilities [4].The EQUAL programme has focussed on three areas:

built environment, design for all and very recently,rehabilitation. The built environment addresses thedesign of the home, public buildings, spaces, andtransport systems. Rehabilitation covers both rehabili-tation informatics and assistive technologies. Design forall, aims ‘to generate the knowledge base to extend therange of application of equipment, services and systemsdesigned for the general population to people withdisabilities through the development of the ‘design forall’ approaches. The programme aims to identify theneeds of designers and commissioners of product andservice design for data sets and information relating tocapabilities, including in particular those of older anddisabled people, to define generic design methodologiesand developing suitable design aids and design guidancefor the many designers for whom design for all willrepresent a radical shift in design practice, and theprovision of guidance on the need for and process ofuser involvement in design in the context of a wider usergroup’.Clearly the research documented here aims to support

the DFAll approach. Primarily through the develop-ment of computer based system comprising an inte-grated database of 3D characteristics, capabilities andbehaviour of people together with a tool to support theuse of this data within the design context. The focus is

on the physical aspects of a particular design so thatbroader range of the population can be considered whenevaluating multivariate issues including access, fit,reach, strength and posture [5]. The work will addressthe need to focus on the principles of good design andergonomics as opposed to ‘driving’ the system and willprovide tools to aid in the prediction of the percentageof the population that will be catered for by a design.Ultimately there is a need to determine who has been‘designed out’, why, and what changes can be made toimprove the design in this regard.

1.2. Multivariate issues and data requirements

In addition to promoting the DFAll concept todesigners it is important to also provide appropriatesupport through the availability of the necessaryinformation about the user and their needs. However,databases concerned with appropriate data in this areasuch as anthropometry and human capability [6–11],typically provide only very limited information concern-ing people who are older and disabled. Data collectedthat is relevant to those older or disabled tend to be oflimited sample size and relate to very specific conditions[12–14].Another aspect of this issue is the way in which

anthropometric data is presented in percentiles. Thepercentile is a univariate statistic which refers to onlyone characteristic in isolation telling us little or nothingabout other body dimensions [15]. For a given design,analysis of access, reach, vision, strength and mobilitymay all be paramount in determining the accommoda-tion of an individual. As such, analysis of a design for atypical range of the population might consider 5thpercentile female stature to 95th percentile male stature.It would seem that our chosen range covers 90% of thepopulation and it is therefore reasonable to assume thatthe accommodation of a significant proportion of thepopulation has been addressed. In reality an xthpercentile has poor correlation between body dimen-sions and therefore does not cater for situations thatoccur all to frequently such as tall people with relativelyshort arms or short people with relatively long legs anda short trunk.It is the intention of the research to create a database

that addresses these issues through the collection andstorage of multivariate data on individuals. The initialsample will be a modest 100 people, the majority ofwhom are older and disabled. Data will be collected inorder for the individuals to be modelled and to be usedwithin task based analysis of product, service andsystem designs. This will provide a preliminary dataset for development and validation of a predictive toolfor estimating the percentage accommodated by adesign. It is also recognised that there will be a needfor a much larger survey in the future.

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2. Survey of current practice

To establish the current situation regarding design inrelation to the philosophy of DFAll, a survey ofdesigners and other professionals involved in the designprocess was carried out. The purpose was to investigateexisting products, procedures and systems. It was alsoimportant for the success of the design tool, to identifythe needs of designers whilst attempting to ‘design forall’. Thus far 35 interviews have been carried out withindividuals involved in the design process from students,through engineers, clinicians and design directors acrossa broad range of industries. Information was gained onissues such as the degree of awareness of DFAll orrelated approaches, current information sources, meth-odologies used, tools and systems used, knowledge ofthe user, and their needs with respect to meetingcustomer requirements. Initial findings include:

* Users are mainly involved in the design processduring final testing, when the product form andfunctionality is largely set.

* Design teams rarely evaluate early prototypes orexisting designs themselves with awareness of thedifferent types of user and in the environment inwhich the product would be used.

* Design teams follow the specification placed by theclient and, unless specifically requested, they do notattempt to include the needs of older and disabledpeople. For in-house designers these needs are alsorarely considered unless the product is specificallytargeted at that group.

* Available data tends to be difficult to find, inap-propriate and often presented in a form difficult toadapt to the designer’s needs.

* CAD is a widespread tool and due to its familiarity tothose involved in the design process and usagethroughout the product development process newforms of data and evaluative techniques should beintegrated, or work in conjunction, with existingsystems.

A qualitative analysis of the findings supports thepremise of DFAll and also a broader need for improvingthe awareness and availability of appropriate informa-tion and tools in the ergonomics field especially relatedto those sectors of the population that do not fit into astereotype of a ‘normal’ able-bodied user.

3. Data collection

3.1. Multivariate database

In contrast to traditional population data, the dataelement of the tool will consist of a multivariate

database of individuals, including those who are olderand disabled. A range of data will be included for eachindividual including: anthropometric data on variousbody dimensions, joint constraints, reach/grip relatedhand length, handedness and a range of descriptive datarelated to the individual’s name, age, sex, etc. Inaddition, data will be collected on task-based capabilitysuch as reach envelopes and a set of genericallyapplicable task analyses such as pick and placeoperations around the home or supermarket. Finallydata will be collected on behaviour, and in particular,coping strategies that individuals will employ in order tocomplete a task, examples of which include sitting on astool for kitchen tasks or kneeling down whilst placingor retrieving items from an oven.An initial sample of 100 individuals will be taken and

used to create 3D human representations of theindividuals; these human models will then be used toobtain feedback on the efficacy of a design through theuse of virtual fitting trials providing predictions on fit,reach, vision and strength on an individual by individualbasis. The tool then aids the designer by allowing theresults of the virtual fitting trials to be interrogatedproviding data and a visual representation of thefeatures or task elements that cause the greatestdifficulty. This analysis will ensure that the designerfocuses on the areas that are key for maximising thepercentage of the intended population physicallyaccommodated by the design.Validation of the tool will be sought by comparison of

its predictions with results obtained from a sample ofindividuals using test rigs. A prototype tool will then bedemonstrated to designers at all levels and used in anumber of case studies. DFAll workshops will be held topresent and distribute results, obtain the views of awider audience and elicit any concerns.

3.2. Pilot study

Prior to the full study, it was decided to conduct asmall pilot to refine the process for data collection, tofully understand all the issues regarding data collectionespecially when dealing with older and disabled subjects,and to test a number of differing data collectionmethods. The pilot study was held over the course of aweek with eight subjects each scheduled for a 2 h timeslot. The eight subjects consisted of two younger able-bodied people, two older people (63 years +), twoambulant disabled people and two wheelchair users. Foreach pairing there was an even split of one female andone male subject. The data collected consisted of fivemain sections:

* General information on name, age, sex, weight,occupation, history of disability (if any) etc.

R. Marshall et al. / Robotics and Computer Integrated Manufacturing 18 (2002) 297–303 299

* Anthropometry and flesh depth measures. Twoapproaches were taken, one consisted of measuringbody dimensions using easily identified bony promi-nences and landmarks, the other was based onanatomical definitions of determining joint centresfor each major joint.

* Joint constraints. Comfort angles taken orthogonallyfor each joint of the upper limb.

* Reach envelopes. A definition of the volume de-scribed by the motion capability for the upper limb.

* Task based capability and behaviour for simplekitchen pick-and-place tasks at three standardkitchen heights (lowest oven shelf, worktop, lowestwall unit shelf).

The five sections were then split between traditionaldata collection methods including the use of a stadi-ometer, sitting height table, anthropometer, goniometer,tape measure, 30 cm rule, a reach envelope board, videoand digital still camera, and a more technologicallyadvanced approach using CODA, a real-time motioncapture system. The CODA system involves the use ofsmall markers and control boxes that are located on thebody in the desired location. These markers are thenidentified and tracked by a number of CODA machines.A single CODA machine is capable of tracking a markerin 3D space but in order to increase the field of view ofthe system, two CODAs were linked together for thepilot. Fig. 1 shows a subject performing the reachenvelope analysis using the traditional reach envelopeboard. Arcs are drawn with the body at various anglesto the board, providing the volume described by the

reach capability for that particular arm. Fig. 2 shows thesame subject complete with CODA markers performingthe task study.The pilot data is still under analysis so no definitive

data can be released on the comparison betweenthe data collection methods but it is clear that collectingdata in this manner is appropriate and that the protocoldefined for the pilot is sound. Participants were veryunderstanding and supportive of the work in generaland were keen to be involved. Issues with mobility,stamina and capability of the older and disabled subjectswas handled by taking a pace from the subjectthemselves, allowing sufficient breaks and being ableto take the majority of the data whilst the subject wasseated. In addition the data was all captured usingcomfort limits, as maximum limits, whilst interesting,would rarely be used in common everyday tasks.

4. A task based design support tool

The use of computer aided ergonomics systems duringproduct development is a well-established methodologyof which there are numerous examples [16]. System foraiding man–machine interaction evaluation (SAMMIE)Fig. 1. Subject performing reach envelope test.

Fig. 2. Subject performing task simulation with CODA data

collection.


is a long-established and typical example that has beenused in a wide variety of applications [17] and forms thebasis of the work described here (Fig. 3). Humanmodelling systems provide the ability to construct 3Dmodels from anthropometric data which can bearticulated between the body segments to simulate awide variety of postures. These human models can thenbe used in conjunction with a CAD model of theproduct being designed, to conduct computer basedtrials. Predictive results provide a much strongeremphasis on the need for sound ergonomic solutionsduring the design process and enable the designer to bemore proactive in achieving user-oriented designs.The approach taken in development of the tool’s

capabilities focuses on an integrated approach tosupporting the designer in three key areas: data inputand manipulation, task description and analysis, resultreporting and analysis feedback. This approach thenaids the designer in the evaluation of a specific design,establishing semi-automated virtual fitting trials throughmacro programming for the SAMMIE computer aidedergonomics system. This has evolved from some simpletasks using the tool and macro language into a basis fora generic design analysis macro with supporting datainput and storage. This is being carried out in parallelwith the survey and data collection aspects identifiedabove and thus synthesised data is being used to developthe methodology.

4.1. Task definition model

The next stage of development involves the definitionand implementation of a fully capable task definitionmodel. This model consists of a number of elements toallow a more task based approach to be used in drivingthe analysis tool, and to provide the system with the

capability of approximating reality by examining taskstrategies and examining the process of adaptation whenvarious task elements break down due to failure. Themain aims of the task model include:

* Develop a means of describing a task using under-standable terminology, rules and data.

* Provide tools to aid in the construction of the taskdescription.

* Develop an analysis strategy that implements the taskdescription within SAMMIE.

* Synthesise an analysis macro from the analysisstrategy and a set of modular SAMMIE commandmacros.

4.1.1. Approach

Whilst a task is essentially a dynamic process theapproach taken is to determine key-frames, or essen-tially static snapshots, of the task on which to base theanalysis. SAMMIE provides the functionality to modelthe elements of these static snapshots, namely: a posturefor the human model, a target object, and an environ-ment. Therefore, the main requirement in the develop-ment of the task analysis tool is the way in which thecollected data is used to determine a suitable andrealistic posture for the key-frame. SAMMIE alreadycontains some tools to aid in the process of determiningposture for task related elements such as reach inaddition to a number of standard postures. Thoughthese tools are not a complete solution they provide ameans of achieving the desired outcome with someadditional manipulation based mainly on behaviouraldata and its codification in SAMMIE macros. A furtherconsideration in providing a realistic static simulation ofa dynamic environment is to provide a task framework.This task framework will be used to provide the system

Fig. 3. The SAMMIE CAE System.


with information on how task elements interactsuch that any particular key-frame posture isoptimised related to the previous and future key-framepostures.

4.1.2. Task elements

Tasks are essentially combinations of task elementsrelating to posture, the environment, and a set of taskparameters such as duration, repetition, and the overallstructure of these components. In order to understandand manipulate these elements the posture of the humanmodel must be analysed and broken down intomechanisms for achieving this posture. These mechan-isms can be defined as follows:

* Vision: position of head, neck and eyes in order tosuccessfully view the target.

* Reach: position of hand, forearm and upper arm (orfoot, calf and thigh) in order to reach the target.

* Attitude: position and orientation of other bodyelements to aid in vision and reach mechanisms.

* Posture: default postures as an initial component ofthe overall posture.

* Location: position and orientation of the human as awhole.

* Sequence: a manipulation of the vision, reach,attitude, and location posture elements takinginto account the previous and future postural key-frames. Sequence may also take account of loading/strength factors and their influence on the overallposture.

Having outlined a set of posture mechanisms, andassuming the environment to be known (modelled), thetask definition is completed through the specification oftask parameters. The following task parameters havebeen identified:

* Duration: how long (time) the task is to be performedfor.

* Repetition: the number of times the task is to beperformed.

* Tolerance: a percentage of the task element successvalue that can still be considered a success e.g. with aview distance set to 800mm, a tolerance of 10%allows up to 880mm.

An additional concern is the requirement for twolevels of task definition. A user will describe a taskthrough a statement of ‘what’ is to be achieved.However, the system requires details on ‘how’ the taskis to be performed, or be able to synthesise ‘how’ fromexisting data. The outcome of these definitions providesa set of user level commands and appropriate para-meters and a set of system level interpretations. The fullset of these is beyond the scope of the paper but anexample is shown below.

Command: TRACK.

The TRACK statement ensures the human modelkeeps the specified target in view for the duration ofthe task or for a user-specified period.

Syntax:

TRACK target [parameters]

Example:

track ball (GTE=(3),VAL=4000,IMP=10)

States that a system view check must be made of anobject named ball, that the ball will be tracked for thewhole of the task, that the maximum view distance is4000mm, that task element 3 cannot be completeduntil the ball is successfully viewed, and that this taskelement has the maximum overall importance.

4.1.3. Task framework

Whilst the approach to the task definition consists ofa series of static elements the dynamics of the task areconsidered through the task framework. The taskframework is an attempt to replicate the effects of onetask element on consequent and subsequent taskelements. Thus the framework adjusts how a taskelement is performed with the knowledge of therequirements for the next task element. Adjustmentsthat are likely to be made include the orientation andlocation of the human model, its posture, and anystrategies used by the system to try to complete a taskelement.The framework is based on information given during

the process of task definition. From the task descriptionthe framework specifies the number of task elements,which of those elements are dependent on each otherand in what way. The framework also identifies allof the objects that are targets of the task elements andcreates a map of the main areas of activity. The systemprocess to develop the framework consists of thefollowing steps:

1. From task definition determine number of taskelements.

2. Scan the task definition for those task elements thatare linked through the gate parameter and build aframework map.

3. Scan the task definition for the duration parameterand add this to the framework map.

4. Identify all target objects and collect their locationsfrom the model. Analyse their layout and determinethe location and orientation for the human model:* Overlay a 2� 2m grid on the environment.* Identify the ‘working’ grid areas (i.e. those that

contain an interaction).* Weight the working areas according to the number

of task elements per grid and duration.* Determine human model locations and orienta-

tions for task elements:


– Check weighting and adjacency of each grid.For adjacent and equally weighted gridsadopt a mean location and orientation. Foradjacent and non-equally weighted grids biasthe location and orientation towards thegreater weighting. For non-adjacent gridsstart a new location and orientation.

5. Collect target interaction specifics (e.g. hand to use)from the task element targets. Refine the frameworkmap accordingly.

5. Conclusions

The initial survey of design professionals confirms theneed for programmes such as design for all, promotingthe needs of those who or older or disabled in themainstream of product development. It is also clear thatany successful approach to supporting those who workin product development must also provide the appro-priate tools and data to back-up design for all efforts.The pilot data collection has provided an early indica-tion of the issues of data collection especially whendealing with older and disabled subject and analysis isongoing of the data on which to make a decision as tothe most appropriate collection methods. The integra-tion of the data and a task-based approach hasbegun through the development of a task definitionmodel aimed at providing the designer with control ofany analysis yet automating the process beyond thesetup. The initial software development of the designsupport tool has shown how this integrativeapproach might support designers and promote theethos of design for all and ergonomics issues as awhole. It is expected that the tool will provide benefitdirectly to the design community but also to theeducation and research communities as a tool forpromoting these issues in a broader context. Finallyit is hoped that this work will ultimately foster theconcept that products can be developed that meetthe needs of the user regardless of place within the

population without sacrificing image, quality and costeffectiveness.

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A task based ‘design for all’ support tool

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