Chapter 1 - INTRODUCTION TO ENGINEERING DESIGN PROCESS - PART 2 Ergonomics.pdf

Ergonomic

1. Human Factors
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Outline
➢Human Factors in Engineering Design
➢Man-Machine Interface (1)
➢Anthropometric Factors (2)
➢Ergonomic Factors (3)
➢Physiological Factors (4)
➢Psychological Factors (5)
__________________________________________________________
(1) Border
(2) The study of human body measurements
(3) Maximizing productivity by minimizing operator fatigue and discomfort
(4) Body characteristics
(5) Mental

2. Human Factors
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➢EngineeringDesignisconcerned
withthesatisfactionofhuman
needs.
➢Inmanyapplications,human
factorsmustbetakenintoaccount
inthedesignprocess.
➢Man-MachineInterface(MMI)is
veryimportanttobeconsideredin
thedesignprocess
Human Factors in Engineering Design

3. Humanfactorsinman-machinerelationshiphavethe
followingforms:
•Anthropometric
(Humaninteractioninstaticsense:dimensionsofbody)
•Ergonomic
(Humaninteractionindynamicsense:repeatedtasks)
•Physiological
(Humaninteractionwithbodycharacteristics)
•Psychological
(Humaninteractionwithmentalactivities)
Human Factors
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Man-Machine Interface

4. Human Factors
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Man-Machine Interface
TheDesignEngineercandeterminetherelative
importanceofhumanfactorsinhisdesign

5. Human Factors
ANTHROPOMETRIC FACTORS
Anthropometrichumanfactorsarerelatedtothephysical
sizeofhumans;itisman-machineinteractioninstatic
sense.

6. ➢Oneofthemostcommonproblemsisthatofdriver
accommodationinautomobiles.
➢Somemayhaveexperienceddifficultiesineither
gettinginorout,reachingthecontrolsoradequate
visibility.
➢Thesemayhavebeenduetoinadequateattention
tothenatureofthephysicaldimensionsof
humans.
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Anthropometric Factors

7. Statisticaldistribution(relativefrequency)diagramfor
selectedpopulation-personsover18year'soldlivingin
Malaysia.
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Anthropometric Factors

8. Cumulativedistributiondiagramisanalternative
methodtopresentthesameinformation.
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Anthropometric Factors

9. Human Factors
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Anthropometric Factors
➢Thepeakintherelativefrequencydiagramis
oftenclosetotheaveragevalue.
➢Bydesigningfortheaveragepersonweoften
preclude(exclude)50%ofthepopulation.
➢Anexamplewhichillustratesthisconceptisthat
oftheforwardvisibilityofacardriver.

10. Human Factors
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Anthropometric Factors
Foracardrivertobeabletoseeanobstacleofheighth
uptoaminimumdistanceLfromthefrontofthecar.

11. Human Factors
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Ergonomic Factors
The concept of Ergonomics:
The three main optimizational goals of ergonomics:
1.Safety
2.Comfort
3.Efficiency

12. ➢Importancewhenthehumanoperatorisinvolvedwith
themachineinadynamicsense.
➢Ahumanisrequiredtoexertaforceorperhapssupply
worktothemachine.
➢Itshouldbeobviousthattheeffectiveoperationofa
machineoverlongperiodsoftimewilldependuponthe
matchingofrequirementstohumancapability.
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Ergonomic Factors

13. Human Factors
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Ergonomic Factors
Onesimpleexampleisthatwhen
thebrakeoperatingforceishigher
thancanbenormallytolerated.The
driverwillcopewiththesituationat
first,butifthebrakeoperationis
frequent,musclefatiguewill
eventuallyoccurandadangerous
situationwilldevelop.

14. Thecapabilityforperformingmechanicaltasksofthis
typedependsupon:
▪Thephysicalabilityoftheoperator
▪Therangeofmovementrequired
▪Thespeedofmovement
▪Thedurationoftheactivity
▪Thepositionoftheoperator
▪Theenvironmentalcondition.
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Ergonomic Factors

15. ➢Thespeedofmovementconsiderationisimportantfor
assemblyoperationsandalsoincontrolsolutions.
➢Itmaybenecessarytoexecuterapidmovementstooperatea
controldevicesuchasastopbutton.
➢Ergonomicprinciplesarealsoknownasmotionandtime
study.
➢Therearetwofeaturesofmovementwhichareindependent:
1.Theaccelerationanddecelerationstage.
2.Theconstantvelocitystage.
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Ergonomic Factors

16. ➢Thedesignerofthesystemfromanergonomicpointof
viewmustcommence(start)withtheestablishmentofthe
systemrepresentationshowingtheinterrelationships
andtheirrelativevalue.
➢Ausefulmeasureoftherelativevalueofarelationshipis
theproductoftheimportanceoftheparticulareventbythe
frequencyofoccurrence.
➢Ifthesecanbeestablishedthedesignerhasalogic
availabletoassistintheplanningofthelayout.
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Ergonomic Factors

17. Human Factors
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➢Anaircraftinstrumentpanelcanbeconsideredasan
exampleofthisanalysis.
➢Thepilotdevotedvaryinglengthsoftimetolookingata
varietyofinstrumentsandatdifferentfrequenciesof
observation.Thisdataisasindicatedinthefollowingtable.
Ergonomic Factors

18. Human Factors
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Instrument Duration of
observation
(sec)
No. of
observation
per min.
Relative value
Cross pointer 0 0 0
Air speed 0.67 22 14.7
Directional Gyro 0.51 24 12.2
Gyro Horizon 0.59 26 15.3
Engine
Instruments
1. 13 5 5.6
Altimeter 0.47 10 4.7
Turn and Bank
Indicator
0.39 5 2.0
Vertical Speed 0.47 12 5.6
Ergonomic Factors

19. ➢weassumethatallinstrumentsareequallywelldesigned
sothatthedifficultyofreadingisthesameforeach,then
thedurationofobservationmayberegardedasameasure
ofitsimportance.
➢Therelativevalueisthentheproductofdurationand
frequencyandislistedinthethirdcolumn.
➢Thisindicatesthattheinstrumentsofgreatestimportance
areairspeed,directionalgyro,gyrohorizon.
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Ergonomic Factors

20. Human Factors
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Ergonomic Factors
➢Thesemustbeplacedintheprimepositionofthe
instrumentpanelforeaseofviewing.
➢Thenextarealtimeter,verticalspeedandturnandbank
indicator.
➢Ergonomicconsiderationsareimportantinthedesignof
controlbuttons,handles,levers,etc.
➢Thereisaninfinitevarietyofcombinationsofsize,
shape,surfacetexture,materialandcolorwhichcanbe
chosenforcontrolknobsasanexample.

21. Human Factors
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Physiological Factors
Next Lecture

22. Human Factors
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Physiological Factors
➢Physiologicalfactorsareofconcernwhenthephysicochemical
characteristicsofthebodyaresignificant.
➢Asfarasbodyfunctionsareconcernedtheseinvolvethe
neurological,muscular,respiratory,vascularandsensorysystems.
➢Theexteriorappearancecanbegroupedaccordingtotheresponse
tovariousinputssuchas:
▪Visual
▪Auditory
▪Tactile,kinestheticandtastesenses
▪Environment.
_____________________________________
Tactile:Thesenseoftouch
Kinesthetic:Thesensethatdetectbodyposition

23. ➢Humanoperatorsreceiveagreatdealofinformationvisually.
➢Thevisualprocessesenableustoperceive(understand)
form,color,brightnessandmotionandsoreadprinted
instructionsandinstruments,observemovingobjectsandreact
emotionallytocombinationsofshapeandcolor.
➢Inordertoachievethediscriminationnecessaryforcorrect
interpretationitisnecessarytoachievesatisfactoryintensityand
colordiscriminationandresolution.
__________________________
discrimination:recognition
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Physiological Factors

24. ➢Colordiscriminationisreducedwhenillumination
(lighting)levelsarelow,andthiscanleadtounexpected
difficultiesincomprehension.
➢Anassociatedproblemofilluminationwhichhasacritical
effectoncontrastisthatofglareandshadowformation.
Thesecanbecontrolledbycarefuldesignoflighting
systemsandselectionofmaterialsandcolors.
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Physiological Factors

25. Human Factors
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Physiological Factors
➢Anothersourceofinformationisthatwhichistransmitted
audibly(capableofbeingheard).Thiswillrangefromspoken
informationtothenoisewhichmachinerymakeswhen
operating.
➢Spokencommunicationis,ofcourse,veryobvious,but
theunusualsoundthatismadebymalfunctioning
equipmentareoftenrecognizedassuchandleadtothe
takingofremedialaction.

26. ➢Anexcessivelevelofnoisepollutionis,infact,
undesirableforanumberofreasons:
▪Leadstodegradationofspeechintelligibility(clearness)
▪Willleadtophysicaldamagetothehumanauditorysystem.
▪Hinders(prevent)mentalactivityduetodistracting
influences.
▪Canleadtopsychologicalandmentaldisordersif
sustained.
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Physiological Factors

27. ➢Thespeechinterferencelevel(SIL)isameasureofthe
destructivenessofnoise.
➢Itisdeterminedbythelevelofnoiseincertainfrequency
bands.
➢Highlevelsofsoundintensitycausepainandeven
physicaldamage.
➢Theusuallyacceptedthresholdofpainisatabout0.5
W/m
2
(soundintensitywatt/m
2
)
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Physiological Factors

28. Human Factors
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Physiological Factors
Thefollowingstepsareavailablefortheacoustic(sound)
treatmentofworkingenvironments:
▪Controlthenoiseatitssourcebychangingthe
dynamicbehaviorsofthemachine,modifyingfluid
jetflow,…etc.
▪Createbarriersbetweenthesourceandthe
listener.
▪Providepersonalprotectivedevices.
▪Modifyoperatingproceduressothattheexposure
ofpersonneltonoiseisreduced.

29. ➢Acousticdesigncanalsotakeonapositiveaspectwhen
weareconcernedwiththequalityofsound.Thisis
importantinthedesignofconcerthalls,recordingstudios,
amplificationequipment.
➢Inthesecasesitisnecessarytoconsiderthefrequency
analysisofthesoundsandthereflectionandabsorptive
characteristicsofsurfacesovertheappropriatefrequency
range.
➢Thegeometricdesignisalsoofconsiderableimportance
sincethisdeterminesthereflectionofsoundwavesandthe
possibleinterferences.
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Physiological Factors

30. ➢Therearemanysensoryinputstowhich
thebodyrespondsandwhichmustbe
takenintoaccount,ormadeuseofinthe
man-machinerelationship.
➢Thesenseoftouchisonewhichisof
greatvalueinvariousrecognition
situations.
➢Brailleprintingofcodedimpressionsis
anexampleoftherecognitionprocessby
thesenseoftouch.
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Physiological Factors

31. ➢Theatmosphericenvironmentinwhichthehuman
performshistasksmayconsiderablyaffecthisworking
officiallyandaccuracy.
➢Whenthetemperatureisbelow10
o
C,physicalstiffness
oftheextremitiesbegins.
➢Above25°Cphysicalfatiguebeginsandabove30°Cthe
mentalprocessesbegintoslowdown.
➢Atemperatureof50°Cistolerable(acceptable)fora
shorttimebutmentalorphysicaleffortisalmost
impossible.
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Physiological Factors

32. Human Factors
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Physiological Factors
➢Humidityhaslittleeffectonheatexchangefornormal
temperatures.
➢Athightemperatures,however,humidityhasan
importanteffectonheattransfer,comfortand
physiologicaltolerance.
➢Thereisarelationshipbetweentemperaturesand
humiditywhichleadstosimilardegreesofcomfort.

33. Human Factors
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Psychological Factors
Psychologicalconsiderationsinhumanfactorsanalysisare
concernedwiththementalactivityrelationshipbetween
manandthemachine.Thisinvolves:
•Interpretationofinformation
•Motivationandfatigue
•Decisionmaking
•Aesthetics(philosophyofart)

34. Human Factors
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Psychological Factors
➢Thedesignofvisualdisplayssuchascontrolpanels,
instrumentpanelsandotherinformativedisplaysisa
typicalexampleofpsychologicalfactorsatwork.
➢Thereareanumberofprincipleswhichhavebeen
developed.Someoftheseinclude:
1.Retaintheusualmethodofoperation(e.g.,apower
switchisONwhentheoperatingleverisDOWN

35. 2.Usedigitalindicatorsforprecise
numericalvalueswithnoneedfor
interpretation.Thatissatisfactory
onlywhenvaluesareconstantor
notchangingrapidly.
3.Fortimevariablereadingsnot
requiringhighaccuracyuse
movingpointersoverafixedlinear
orcircularscale.
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Psychological Factors

36. Human Factors
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Psychological Factors
4.Arrangecontrolmovement
tocoincidewithrequired
directionofinstrumentpointer
movement.
5.Colorcodingondialsare
usefulinhelpingtorecognize
conditionsquicklye.g.,green-
normal,yellow-caution,red-
danger.

37. ➢Iftheoperatorfeelshecaneasilyassertcontrol,andthat
thesystemwillrespond,thenhehaslessfearofthe
operationresultinginreducedfatigueandimproves
motivation.
➢Thismeansthatthemechanismofthecontroldevice
shouldbedesignedsothat:
(i)Movementsareeasy.
(ii)Slacknessiseliminated.
(iii)Theoperatorisawareofafeedbackresponse.
(iv)Thesystemresponseisrapid.
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Psychological Factors

38. ➢Ifthiscannotbeachievedthecontrollershould
incorporatesomerestrictionsothatoverreactionand
instabilitydoesnotdevelop.
➢Decisionmakingissometimesadifficulttaskforpeople
tocarryout.
➢Itisimportantthattheincominginformationbepresented
inareadilyassimilated(realize)manner.
➢However,itisalsonecessarythatthisinformationbe
suppliedinampletimefortheoperatortobeabletodecide
onhiscourseofcontrolaction.
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Psychological Factors