Architecture of an expert system for ergonomics analysis and design

*Corresponding author.

International Journal of Industrial Ergonomics 23 (1999) 205—221

Architecture of an expert system for ergonomics analysisand design

Issachar Gilad*, Reuven KarniFaculty of Industrial Engineering and Management, Technion Israel Institute of Technology, Technion city, Haifa 32000, Israel

Received 5 March 1996; accepted 16 April 1997

Abstract

The architecture of a computerized ergonomics expert system (ERGOEX) for ameliorating the conditions of workersat a workplace is described. The purpose of this computer-assisted tool is to transform sets of worker data and workingrequirements into a specification or description of an artifact, which is capable of producing ergonomic functions. Theergonomic advisor has been developed so as to reach out to both expert and non-expert users, who can thereby takeadvantage of this novel approach to workplace design without requiring sophisticated computing equipment. Turbo-Pascal has been chosen as language, rather than an expert system shell, or a logic-based language. In realizing the aims of“guidance” and “user friendliness” we have adopted the principle that the expert system must be able to interface withboth novice and expert users. The analysis function is represented as hierarchy, workplace structure, environment, andevaluation and failure analysis at the highest level, and further breakdowns at lower levels. The design process is dividedinto data input, generation of recommendations, critiquing, and referral to sources for basic supplementary information.

Relevance to industry

The article describes an expert advisory system to be used by Industrial Engineers, Ergonomists, factory personnel andmedical staff for analysis, evaluation and design of a workplace. The methodology has been developed for both expertand non-expert practitioners, who can operate the system using an interactive man—computer dialogue. ( 1999 ElsevierScience B.V. All rights reserved.

Keywords: Ergonomics design; Expert system; Workplace analysis; Working environment

1. Introduction

The implementation of ergonomic solutions inan industrial setting is based on effective analysisand a practical design to be applied in a givenworkplace and its immediate environment. In such

a process the know-how of ergonomics is to beapplied to enhance the workplace design and toimprove the conditions in which the worker per-forms his set of tasks. Solving ergonomical prob-lems requires the transformation of scientific data,which in many cases derives from different disci-plines, guided by a systematic way for a successfulsolution. Chen et al. (1991) state that communica-tion is a major obstacle in imparting ergonomics

0169-8141/99/$ — see front matter ( 1999 Elsevier Science B.V. All rights reserved.PII: S 0 1 6 9 - 8 1 4 1 ( 9 7 ) 0 0 0 5 6 - 5

knowledge to the working population. This lack ofability to impart ergonomics knowledge, for suc-cessfully solving industrial problems, has beenobserved by many ergonomists. To deal with thisgap, a methodology based on an interactive man—computer dialogue, has been developed by theauthors (Gilad et al., 1990a; Karni and Gilad, 1991).In this method, the knowledge of ergonomics andhuman factors subjects has been organized into anexpert advisory system, which can be used bya wide variety of users to provide guidelines anddesign suggestions regarding workstations andtheir surroundings.

In this form it has been found that ergonomicsknowledge can be made accessible with automatedguidance, for better analytical results. The systemwould prompt the user for information about theworkplace and the working environment andwould provide him with insight regarding thoseconditions best favored for the given situation.

The potential for using expert systems in ergo-nomics has been recognized by researchers in thefield during the last 10 years, with the developmentof AI-based techniques and algorithms. Lehto(1985) developed guidelines for analyzing the safetyof certain work tools, using a “generic safety analy-sis” approach to formalize the analysis of worksafety problems. The resulting expert system wasbased on the EMYCIN shell, developed previouslyfor medical applications (Shortliffe, 1976). The in-teraction was based on question-and-answer; thesystem asked a series of questions, and suggestedseveral alternative answers for each one. In ad-dition, the system inserted certain remarks or ob-servations at relevant intervals. The architectureclosely resembled a computerized operating systemrather than an interactive advisor.

Taylor and Corlett (1987) described an expertsystem for guiding engineers in accounting forergonomic aspects in their design of work tasks.Their approach was oriented towards physical as-pects such as lighting. Their system, ALFIE, oper-ated in the same way as the previous system; and itsoutput included statements reminiscent of logictheory which were highly unfamiliar to engineers.Mainframe PASCAL was used in this case.DeGreve and Ayoub (1987) presented a system fordeciding on the dimensions of a work station. It

was implemented using the Personal ConsultantShell on the Texas Instruments Explorer. It useda full screen approach, and was better oriented tointeract with professional ergonomists or trainedengineers.

Budnick et al. (1992) described a prototype sys-tem, CDEEP, which provided ergonomic advice todesign engineers. Its database included details onphysical, functional and procedural features ofcomponents, assemblies, processes, workspace, en-vironment and worker population. Its rule basesdealt with ergonomic design criteria and problem-solving strategies. No details of the user interfacewere given. The system is based upon specializedLISP and Hypertext software.

As the use of AI-based approaches expanded,systems were developed on the basis of a procedureto be used by ergonomists in investigating a specificproblem. Laurig and Rombach (1989) set out re-quirements for an ergonomic expert system, andthe procedure to be followed in solving manualmaterial handling activities (also proposed byKarwowski et al., 1986, 1987). The requirementsincluded the use of hardware and software compat-ible with the user’s computing environment, butflexible and powerful, user friendliness as expressedin the interface structure and terminology, theability to provide explanations, and emphasis onacceptable and unacceptable factor constraints,also discussed by Taylor and Corlett (1987). Thesteps of their procedure were input — task andpersonal characteristics; process — analysis and as-sessment of degree of compliance, practicabilityand tolerability; and output — a list of commentsand explanations regarding task features requiringredesign.

Karwowski et al. (1990) provided a collectionof articles regarding the use of computers in ergon-omics, many of which incorporated AI-based tech-niques and procedures. In particular, Brennan et al.(1990) described a prototype expert system forworkstation design, with a multi-step procedure asfollows: input — operator characteristics, task char-acteristics, percentiles, positions, rest periods,man/machine communication, time; output — workstation and display dimensions, hand and foot con-trol characteristics, and environmental require-ments (noise, lighting, displays).

206 I. Gilad et al. / International Journal of Industrial Ergonomics 23 (1999) 205—221

Chen et al. (1991) described the development ofan interactive computer assisted ergonomics analy-sis system (EASY). The system consists of threecomponents: EIAS — for evaluation of tasks by theworker; PWSI — to be used by supervisor for fur-ther investigation of problem situations, and DJAS— for manual material handling. The proposed tech-nique was claimed to have a fairly high rate ofacceptance by ergonomic experts.

It has been noticed, when carrying out ergon-omic projects, that incorrect or inadequate work-place design and operation have decidedly negativeeffects on working capability — resulting in lowproductivity — and direct negative impacts onworker health. It is believed that comprehensiveknowledge about ergonomics factors, and easy ac-cessibility to such knowledge, can significantly con-tribute to the successful planning of mannedworking cells and workspaces. This is likely toresult in improvements in working conditions, oc-cupational health, and production outputs.

An architecture of an expert system, intended toameliorate the conditions of workers at the work-place, is outlined in this paper. A methodology ofhow to incorporate ergonomics factors into a speci-fic architecture of an expert advisor, based upon aninteractive man/computer dialogue, has been de-veloped at the Technion Israel Institute of Techno-logy over the last few years (Gilad et al., 1990b;Gilad et al., 1992; Gilad and Karni, 1992; Zellner etal., 1992). The project aims to enhance the design ofworkplaces and improve poor working conditionsresulting from incorrect arrangement of a givenworkplace, or limited knowledge regarding the cre-ation of a safe working layout.

An extensive range of knowledge on ergonomicsand human factors subjects has been gathered andorganized into a computer program — the expertadvisory system. It is intended to be used as anevaluation and design tool by a wide variety ofusers, and has thus been made easy to operate,whilst providing guidelines and design suggestionsregarding workstations and their surroundings.Such knowledge can also enable those dealing withsafety and the ill effects of poor working conditions,such as medical personnel, to see more clearly theconnection between ill health and incorrect posturebrought about by these conditions. Similar senti-

ments regarding knowledge accessibility have beenexpressed by Clegg (1988) and Swierenga et al.(1990). The need for guidance is thus indispensable;and so is the need for easily accessible and auto-mated guidance, which are vital to all those con-cerned with the quality of working life. Such a guidewould prompt the user for information about theworker and the environment, and would providehim with insight regarding those conditions bestfavoring the given situation. The technology existstoday for creating and utilizing such advisors —expert system technology.

The research project described in this articlehas been carried out to demonstrate that an accept-able expert system tool can be developed for ergon-omic applications, both in content and manner ofoperation. The system developed — ERGOEX(ERGOnomics EXpert system), has also indicatedthat a systematic workplace design and evaluationprocedure can be formulated. At first sight it mayseem pretentious to try to incorporate the wholesubject of ergonomics into a single computer-basedtool. No system can be comprehensive enough toanswer all questions addressed to it; nor has a givenproblem a single or totally definable solution.Specialists in areas such as architecture, acousticsand climate will usually be required in order toobtain the best answer. Nevertheless, it is our opin-ion and experience that knowledge incorporated inan expert system can cover the main design para-meters, and also make the designer aware of themultiplicity of factors entering into a good work-place design.

2. Method

2.1. Objectives

In order to achieve the power and flexibilityrequired of an ergonomic expert system, the follow-ing objectives were set:

(1) Determination of the extent of knowledgeand analysis required in order to obtain a compre-hensive and adequate description of a working en-vironment.

(2) Formulation of a “user-friendly” bases forpotential users — to utilize the stored knowledge.

I. Gilad et al. / International Journal of Industrial Ergonomics 23 (1999) 205—221 207

(3) Design of a computer-based expert systemfor implementing the above objectives.

(4) Development of a set of expert routineswhich could be operated on conventional equip-ment without the need for special supporting hard-ware or software.

These in turn led to six research goals for defin-ing a methodology to support the design, planningand operation of a workplace:

Knowledge content: This requires delineatingthose (main) factors which influence the structure ofa working environment, and requires the setting upof a suitable taxonomic framework to be realizedwithin the expert system.

Knowledge representation: This requires deter-mination of how to present knowledge to the user,and how to store it. Most planners and designers areaccustomed to representations such as texts, tablesand graphs. Knowledge must be presented in suchformats, and not in “computerese”. The knowledgeitself is stored in a knowledge base — either as a sep-arate entity or compiled within the expert system.

Knowledge level: This requires attuning the ex-tent and depth of knowledge and its manipulationto the capabilities of the user. Shallow knowledge,on the one hand, and “knowledge overload”, on theother, are likely to deter the use of an expert system.

Knowledge flexibility: It should be emphasizedthat expert systems do not create knowledge, butconcentrate it and make it available on an activebasis. They must also enable this knowledge to beextended as required, and updated when betterinformation is made available.

System operation: The user must be accordedmaximum flexibility in utilizing the stored know-ledge, and operating the system using familiar com-puter tools.

Interaction: Not only must knowledge be active,it must also be interactive. The user enters the datahe knows, and explores topics of interest to him; thesystem must “understand” the user’s intentions,find the relevant knowledge, and display suitableresponses.

2.2. Levels of knowledge and knowledge display

We envisage two levels of interaction and con-sultation with the expert system when solving a

workplace design problem: the ergonomic profes-sional or his deputy; and the novice user. Theergonomic professional (expert) wishes to obtainin-depth advice about technical or professional fac-tors which influence his decision-making process.The semi-professional (novice) is required to solveengineering-oriented problems such as workstationdesign or redesign in a real-life framework. Suchactivities include industrial engineers, personnelmanagers and work foremen — especially in a smallorganization — dealing with the design or installa-tion of a work station; doctors dealing with work-related traumas; and safety officers checking outthe acceptability of a work-related situation.

The ERGOEX advisor incorporates a flexibleapproach to evaluate parameters such as equip-ment configuration, thus allowing the designer free-dom of choice in developing a suitable design.Moreover, medical personnel, who are well awareof the relationships between incorrect posture andill health, can also contribute to the elimination ofsuch problems as a result of the guidelines andcritiques provided by the system. The ergonomicadvisor has been developed so as to reach out toboth expert and non-expert users, who can therebytake advantage of this novel approach to work-place design without requiring sophisticated com-puting equipment. In realizing the aims of“guidance” and “user friendliness” we have ad-opted the principle that the expert system must beable to interface with both novice and expert users.

ERGOEX is based on a taxonomy of ergonomicsand provides a wide range of categories (Table 1).The expert has experience in workplace design, andis thus provided with a comprehensive set of ques-tions to be answered in each category, and a largeamount of ergonomic detail based on these an-swers. The novice, who is feeling his way aroundthe idea of workplace design, is not required tointeract as extensively with the advisor. Each usercan decide within which category he wishes tooperate; and during the same session he can switchfrom one mode to an other.

2.3. Methodological basis

The architecture for an ergonomic expert system,in view of all the considerations detailed in the


Table 1Ergonomic analysis taxonomy and categories

Category Content

Data category Basic design parametersworker’s Anthropometry (sex, weight, body)actual posture involved (sit, stand, kneel)equipment, power tools, mechanical aids

Surroundings category Actual / required conditionslightnoisevibrationclimate

Supporting category Support for system recommendationsbiomechanical models, formulaekinesiological and postural limitationstime and motion Methods and measurementscumulative trauma disorders casesknowledge sources and scientific references

previous sections, is based on knowledge repres-entation and structure, interactive processes, anddata processing processes.

2.3.1. Knowledge representation and structureConsultation (case) data, stored knowledge and

response displays are represented in several stan-dard formats, as follows:

¹ables: These are used for displaying quantitat-ive or logical (yes/no) input data describing userrequirements or actual situations, and symbolic orquantitative output data. The user moves down thetable, entering data as available. In many instances,the system fills in default or recommended data.Auxiliary data tables are also provided to aid theuser in selecting appropriate design or operatingconditions.

¸ists: These cover qualitative and textual re-sponses of the system and provide lists of remarks,recommendations and critiques regarding an actualor desired situation.

Graphs: These provide multi-colored data on con-tinua such as noise and temperature, and enable theuser to select satisfactory or ideal operating pointsin accordance with appropriate input parameters.

¸ayouts: These are computerized drawings orsketches providing an iconic representation ofworkplace layouts and equipment.

2.3.2. Knowledge and response formatsUsing these formats, knowledge “packaged”

and presented to the user is organized intoseveral standard response categories, which aidin operating the system and understanding itsoutputs:

Quantitative tables: Anthropometric measure-ments, equipment dimensions, lighting, temper-ature or vibration ranges, and so on.

General recommendations: These provide over-all “good advice” regarding work stations of thetype being studied, their environment and opera-tion.

Specific recommendations: These focus on “goodadvice” and remarks regarding the specific workstation suggested, and possible alternatives fora given situation.

Specific critiques: These focus on remarks andsuggested improvements for a given situation.

Auxiliary information: These are data tables andgraphs providing typical or recommended valuesfor lighting, vibration, noise, etc.

Recommended work layouts: These encompassequipment details and workspace layouts.

References: At the bottom of many tables andgraphs scientific information sources are displayed.A full bibliographical reference is available throughthe main menu.


Fig. 1. Knowledge level selection.

2.4. Using the ERGOEX advisor

2.4.1. The general conceptThe decision process incorporated into the sys-

tem is based upon the concept of a data bankconsisting of actual measurements and require-ments, and system-generated responses. Not alldata need be furnished; the system uses defaultvalues where necessary, or computes values basedupon stored rules. The resultant data bank can beviewed as a consistent set of values which have beeninput and/or derived.

In order for the design process to be both logicaland effective, the order in which each aspect isexplored and determined has to be sequenced cor-rectly. We suggest moving “top down”, from gen-eral to detailed aspects, using a hierarchical seriesof displays. Most topics presented in each displayare linked to one or more detailed displays ata lower level. For example, when developing a sta-tion configuration, the user is first asked for theworking position — sitting, standing, kneeling, etc.When a posture is selected, a subsequent displayrequests equipment details — table, chair, computer,telephone, etc. A further screen then presents rec-ommended dimensions for the item, such as seatheight and breadth. Parallel displays providea schematic layout of the workstation element andmeasurements, with textual recommendations andcritiques regarding the element, such as suggested

materials of construction or colors, or the observa-tion that dimensions are too tight or too free.

2.4.2. A walk through of the ERGOEX systemWe now detail a walk-through of a consultation

with the system. An existing work station is com-prises of a table and simple chair, 37 cm high. Theworker is a 40 year old male, height 173 cm, weight72 kg. He works continuously for six hours per day.Correct lighting conditions are required; at presentthey stand at 70 candlepower. The task requiresaverage precision.

(1) Activating the system and setting a level ofexpertise (Fig. 1). The user sits down at a PC(IBM-compatible) and enters “ERGOEX”. Afterseveral introductory menus he is requested to indi-cate the level of expertise required — Novice orExpert — in our case EXPERT.

(2) Selecting the topic (Fig. 2). A top-level menuprovides a list of topics, organized within threecategories, included in the ERGOEX knowledgebase. In order to enter data regarding the worker hefirst turns to “Anthropometry”.

(3) Entering worker data (Fig. 3). A set of inputtables is provided for defining worker character-istics. The user can enter a complete set, if it isavailable; otherwise he can enter a minimal set: sex,age, height and weight; default values for otherbody parameters are provided by the system usingstandard anthropometric tables.


Fig. 2. Basic system taxonomy.

Fig. 3. Anthropometry data entry table.

(4) Characterizing the task (Fig. 4). The user re-turns to the main menu and indicates “EQUIP-MENT”. This leads to a task definition menu. Theuser then indicates “SITTING” (regular precision).

(5) Defining the work environment (Fig. 5). Theuser is provided with a list of regular equipment tobe found in a seated workplace, and indicates (ex-cept for the necessary chair and desk) what types

are to be found, as well as several task character-istics — continuity and duration. He can thenindicate each type of equipment, to obtain recom-mended dimensions or to enter dimensions of anactual work station.

(6) Recommended and actual dimensions(Fig. 6). The user indicates “CHAIR” and is pre-sented with a list of recommended dimensions or


Fig. 4. Task defenition table.

Fig. 5. Defining the work environment.

ranges for the relevant equipment type. He can alsoenter details of an actual workstation for compari-son, and, by moving down to the bottom rows ofthe screen, request a drawing of the recommendedchair, turn to source references for the data dis-played, and obtain an idea of how the chair andworker characteristics are related.

(7) The equipment drawing (Fig. 7). Moving thebar down to the relevant row (“Front and side viewof the recommended chair”) calls up a dimensioneddrawing of the chair (not shown here) on the screen.

(8) Display of recommendations, critique andrecommended workplace layout (Fig. 8). Return-ing to stage (5) above (using the PgUp key) and


Fig. 6. Recommended and actual equipment dimensions.

Fig. 7. The equipment drawing.

Fig. 8. Intermediate menu for selecting equipment advisory responces.

targeting the row “Recommendations regardingyour workplace”, the user obtains advice regardinghis actual workstation. Three types of advice aregiven: critique of a current design, general recom-

mendations regarding workplaces of this type, anda suggested workplace layout.

(9) Evaluating a current workstation design(Fig. 9). The evaluations obtained include


Fig. 9. Workstation evaluation checklist.

Fig. 10. Workplace layout drawing.

unacceptable dimensions, problems associated withunsuitable equipment, and suggested improve-ments.

(10) Recommended layout (Fig. 10). In a similarfashion to the equipment drawing, a workplacelayout (not shown here) is presented.

(11) Investigation of lighting conditions(Fig. 11). The user returns to the main menu (stage2 above) and indicates the “LIGHTING” option.He is required to enter the current lighting level,environmental conditions, and work conditions.

(12) Determining the correct level of illumina-tion required (Figs. 12 and 13). In order to set anappropriate level of illumination (200 lx), the userrequests a recommendation from the system via therow “Recommendations regarding light”. Via anintermediate menu he passes down to the row“Suitable lighting levels in work rooms” to obtaina list of suggested lighting levels.

(13) Recommended lighting conditions (Fig. 14).Returning to the intermediate menu, the userindicates the row “The workstation we recommendfor you (regarding lighting)” and obtains therecommended lighting values for background, tar-get and general conditions. The investigation maybe further pursued in order to determine suitablecolors for walls, floor and ceiling, and the use ofdaylight.

(14) Evaluation of current lighting conditions(Fig. 15). Returning to the intermediate menu, theuser can request a critique of the conditions he hasdetermined for lighting from the row “Your work-station evaluation (regarding lighting)”.

(15) Further use of ERGOEX. By use of thePgUp key and the various menus, the user canexplore new subjects, revise current design condi-tions, move from “EXPERT” to “NOVICE”, orterminate the consultation.


Fig. 11. Workplace lighting conditions.

Fig. 12. Intermediate menu for selecting light advisory responces.

2.5. Interactive processes

The ERGOEX advisor is interactive and is com-posed of dialogue windows linked together ina top-down manner. The initial window leads tomore detailed ones and so on. It is possible to movefrom one window to another up and down thehierarchy. Each window forms a “crossroad” from

which it branches out to secondary windows, andto which they return. To change course it is neces-sary to reach a crossroad from which a new pathmay be easily selected and followed. The programinteracts through input and output screens. Inputscreens enable entry of data in tabular form, withsome freedom to choose the order in which data isinput, via cursor movement. The output screens


Fig. 13. Recommended suitable lighting levels in work rooms.

Fig. 14. Recommended lighting for the case study.

Fig. 15. Evaluation of current lighting conditions.

display tabular or graphic information. Maximumuser-system flexibility is based on an interactiveprocess which is based on the following principles:

Directionality: The manner in which a user ap-proaches an ergonomic analysis is neither uni-directional or sequential. He tends to “browse”through the system, entering data and interpretingresponses. Only a few topics may interest him — and

not necessarily in the order presented. He may skipover a topics and return to it later in the session. Hemay even return to a topic already dealt with. Thus,although ERGOEX has a “recommended route”,the user is neither compelled to use it nor preventedfrom deviating from it.

Completeness and truth maintenance: The usermay not have all relevant data at hand, or wish to


deal with any or all topics at the maximum possiblelevel of detail. The system is “data tolerant”, andcan, if necessary, incorporate default (standardized)values. Moreover, the user can change data alreadyentered, as when reconsidering equipment dimen-sions or environmental conditions. At all stages thesystem dynamically adjusts to the current data set,maintaining the “truth” of all responses — outputdata, recommendations and critiques. Of course,the extent and depth of these responses is contin-gent upon the extent and depth of actual or de-faulted data made available to the system.

¸evel of detail: Data, information and know-ledge are organized in hierarchical fashion, so thatthe user may “plumb the depths” of a given topic,or receive a response at a more generalized level.

Control: In order that the user can, with ease,choose what topics to activate, in what order, andto what level of detail, specific functionalities havebeen allocated to various keys:

“Arrows” — these move the cursor or bar up anddown in order to tag an option for subsequentprocess or to enter a specific data value.

“PgDwn” — this transfers the user to the nextpanel (display), at the same or lower level.

“PgUp” — this transfers the user to the previouspanel (display), at the same or higher level.

2.6. Data processing

Turbo Pascal programming has been chosenrather than an expert system shell, or a logic-basedlanguage such as PROLOG, for the following rea-sons:f A fast system response is required, especially

in view of the highly interactive nature ofERGOEX.

f The language is well known, so that the system iseasy to maintain and expand.

f The language enables the system to be built inmodular fashion.

f The system can be implemented on any PC-compatible computer. The size of the program isnot a limitation as overlay processes are invoked.

f The language has facilities for graphics, colorand animation.ERGOEX can run on any PC with a color

screen, although a monochromatic screen can be

used. It requires about 900 KB of memory, and onehard disk or two diskettes.

3. Levels of workplace design

The program envisages three levels of compre-hensiveness at which workplace design and evalu-ation can be carried out: (1) the data category,which supports basic workplace design; (2) theworking category, which provides considerationsregarding the environment; and (3) the support cat-egory, which deals with failure analysis, biomech-anics and knowledge sources — bibliographicalreferences (Table 1). These three levels are organ-ized within the inference framework as “envelopes”which can be successively peeled away as required,starting from the basic data category.

3.1. The data category

At the first level, three traditional ergonomicfactors are incorporated. Anthropometry of theworker for whom the station is being designed,worker posture during activity at the workstation,and equipment needed to furnish the work station.All design starts with anthropometric information— gender, age, body measurements, and classifica-tion of these measurements into accepted percentileintervals. Two levels of detail can be input or gener-ated: (1) basic factors and values based on percen-tiles (semi-professional users), related to normaland maximum working areas and clearances; (2)extensive data covering all body components andregions such as finger, foot and waist dimensions,and clothing allowances (professional users). Wethen deal with aspects of working posture, such aspostural efforts, postural discomfort, and reasonsfor possible posture-related problems. At the semi-professional level we display unsuitable posturesand the likely pains to be caused (Table 2). At theprofessional level we investigate further factors andprovide a more detailed evaluation (Table 3).

This is followed by the equipment (furniture andtools) to be provided to the worker. Matchingequipment to workers and their capabilities is a dif-ficult design problem, and is based on a wide var-iety of considerations as exemplified in Table 4.


Table 2Posture screening at the semi-professional level

Posture Likely site of pain

Standing Feet, lumbar regionSitting with lumbar support Lumbar regionSitting w/o back support Erector spine musclesSitting w/o foot support Knees legs, lumbar regionArms reaching upwards Shoulders, upper armsLifting heavy weights Erector muscles, lumbar

region

Table 3Posture screening at the professional level

Posture Likely risk of pain

Standing in one place Feet, legs, varicose veinsSitting erect w/o back support Extensor muscles of the

backSeat too high Knees and neckSeat too low Shoulders and upper armsHead inclined forward Neck, deterioration of discs

Table 4Equipment screening at two professional levels

Aspect Novice level Expert level

Anthropometry Basic attributes Detailed attributesOffice equipment Chair and table Screen, KeyboardWork tools Simple tools, handles Motorized or electric toolsLift able objects Weight Form and sizeTasks Frequency Safety aspectsExtensions None Stairs, ladders, passages

Handling and transfer

The match is analyzed and confirmed (or rejected)by a graphic picture of the work station.

3.2. The surroundings category

The designer may now proceed to consider envir-onmental factors in the surrounding space. Theseencompass vision and light; sound, noise and vibra-tion; and climate and heat. Again, several depths ofknowledge are possible.

3.3. The support category

Evaluation and failure analysis recognizes thatone of the most significant changes in ergonomics

practice that has taken place during the past twodecades is the expansion of the areas of applicationof this practice. In particular, it has been realizedthat the “system” component of a man/machinesystem embraces more than interface displays andcontrols on the one hand, and the workplace withits environment on the other. In our opinion, ergo-nomic advice should relate to organizational wellbeing as much as to individual well being. This canbe done most effectively by supporting and em-powering the professional with the deeper know-ledge required for a component evaluation andfailure analysis of a man/machine situation. Wesupport decisions in the areas of biomechanics(back and lower/upper extremities), methods andmeasurements, and cumulative trauma disorders.Knowledge sources as scientific references are aswell provided.

3.4. Summary of the workplace design process

The expert-system-based design process may besummarized as follows: The user keys in ERGOEX,moves through a series of introductory menus. Theuser sets the consultation level — expert or novice.He then enters anthropometric data for the workerto be accommodated; data for an existing (or pre-designed) work station (if applicable); data for anexisting (or pre-designed) work environment (if ap-plicable). If data is not available, but values arerequired to obtain a meaningful analysis or re-sponse, the user consults auxiliary tables pro-vided by ERGOEX. In other cases, ERGOEXprovides default data. The knowledge explora-tion, data entry and information obtained aredirected in accordance with the results required.The system provides quantitative or qualitative


recommendations; textual remarks and recommen-dations; textual critiques; and explanations on re-marks, recommendations and critiques. The userextends or refines the design as required until satis-factory results are obtained.

4. Discussion

“There is an urgent need to disseminate ergo-nomics know-how, over and above research find-ings and case studies, in order to promote health,safety and efficiency in the workplace” — IJIE, 10(1992) Editorial. Thus the International Journal ofIndustrial Ergonomics undertook the publicationof ergonomic guidelines in successive issues, as wellas sponsoring the First Invited International Sym-posium on Ergonomic Guidelines and ProblemSolving. Each of these guidelines has been dividedinto two sections — a guide for the practitioner, anda scientific basis for the guide. They are targeted atthe practitioner — manager, production system de-signer, shop supervisor, occupational safety andhealth professional, union representative, labor in-spector or production engineer. The informationprovided is pragmatic — even if it is based on limitedscientific data; and the guidelines are intended toact as a springboard for creating “more useful andusable guide[s] on the topic in the future”.

Surprisingly, the editors do not visualize expertsystems as an appropriate vehicle for assemblingand concentrating guidelines on a given topic, or asthe medium whereby the practitioner can gain ac-cess to such guidelines and use them in an organ-ized manner. Although a previous special issue(IJIE, Vol. 1, No. 2, 1987) was dedicated to the topicof expert systems in ergonomics, little seems to havebeen done to characterize such expert systems andshow how they may be constructed and utilized.

We wish to make a comment regarding the placeof a system, such as ERGOEX, in view of the rapidadvances in computer and hypermedia technology.Materials, which were once found exclusively ina static, linear format are now presented in a newdynamic format, known as hypertext, a com-puterized, non-linear, non-sequential presentationof information. It allows to learn through explora-tion and association, with minimal input all the

elements and links that make up a particular hyper-text unit can be referred to as “hyper space”. Thepotential hazard in this approach is the danger ofgetting lost in hyper space because it is sometimesdifficult to retrace the path to the point of origindue to the number of paths, the lack of beginning orend, and the “nebulous specifications” of directionand pedagogical approach, as addressed byThibeault and Adams (1994).

The hypertext approach leads to terms such as“personal book” (Subbotin and Subbotim, 1996),when applied to complex and multi-layered docu-ments, as stated by (Phelps and Wilensky, 1996);and “portable document” as stated by (Brailsford,1994), when used with laptop computers (Shiels,1995). Lehto et al. (1995) have shown that thisformat is superior to standard reference texts for“reading to do” tasks similar to those a designermay perform when consulting a reference book. Wesee that ERGOEX provides many of these catego-ries: a portable software-based reference system,with a search and navigation engine provided bythe expert system; and a multiple representation ofergonomic information in the form of text, tablesand graphs. It thus helps illustrate the way in whichdesigner aids should be created and used.

Thus, a methodology of an expert system as anadvisory tool for workplace evaluation was de-veloped in the framework of an ongoing project atthe Technion’s Center for Safety and Human Fac-tors. We have demonstrated that it is possible todevelop a systematic method for the design and/orcritiquing of a workplace environment; that themethod is user-friendly; that a wide range of factorscan be included; and that these factors can berepresented and presented in a modular fashion.The system, which is already more than a proto-type, can therefore serve as the basis for furtherextensions.

The user can delve into the design hierarchy asdeeply as required; and can explore as many as-pects as necessary. The outcomes — advice andcriticism — are best known in the sense that theyreflect the extent of the information provided andthe success of the rules and formulae incorporatedin the knowledge base. When input data conflictwith those generated by the system, it comments onthe “inadvisability” of the existing situation and, if


possible, suggests how the situation may be reme-died.

A unique feature of the advisor is the incorpora-tion of an extensive battery of recommend-ations and comments. These include physiologicalfactors such as worker capabilities and endurance;environmental factors such as colors and noiselevels; and psychological factors such as posturesand effects on attention spans and productivity.Some are geared to the specific work station beinganalyzed; others give general advice on gooddesign.

Particular attention is paid to correct posture.The system points out back, leg and arm problemsthat are likely to occur if the correct conditions donot exist. Moreover, should the worker have a spe-cific problem — pregnancy, obesity, physiologicaldisabilities, age-related disabilities — the system re-commends support devices such as adjustable seats,footrests and working surfaces. We intend to aug-ment these comments by allowing specific workercomplaints to be entered and possible causes to bedisplayed.

The user may be unable or unwilling to deter-mine actual environmental conditions — noise,light, climate. The system provides reference in-formation displays which can be consulted to pro-vide order-of-magnitude or typical data, such asnoise conditions in offices or those generated bytools; or temperatures during typical seasons. Theuser can select relevant data from these sources tobe included in the data bank.

Acknowledgements

The authors wish to thank the Committee forResearch and Prevention in Occupational Safetyand Health, Ministry of Labor and SocialAffairs, Jerusalem, Israel, for the funding of thisresearch.

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Documents

Architecture of an expert system for ergonomics analysis and design