My Class

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IE 553 Engineering of Human Work Dr. Andris
Freivalds Class 28
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IE 553 Engineering of Human Work Dr. Andris
Freivalds Class 28
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Cycling Work

• Lifting 8.25 lbs, 20 in., 6/min
• Eave 1.5 kcal/min, Er 1.3 kcal/min
• Ew Eave(TwTr) - ErTr/Tw

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Metabolic Energy Prediction/Modeling

• Need actual measurements on job
• Difficult, interferes with task
• Costly, cant measure new task
• Basis
• Table values (Passmore Durnin, 1955)
• Crude, inaccurate
• Many new jobs not found
• Predictive models ?berg (1968), Garg (1978)

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Garg Model

• Main assumptions (similar to MTM)
• Ejob function of physical characteristics of
  job
• Job broken down into simpler tasks
• Ejob ? Etasks
• Two components
• Maintenance of body posture sitting (Eq. 6.1),
  standing (Eq. 6.2), standing bent (Eq. 6.3)
• Net increase due to tasks
• Ejob ?Eposture time ??Etasks / time
•                        

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Tasks - 1

• Vertical lift
• Stoop lift (Vlt32", Eq. 6.4)
• Squat lift (Vlt32", Eq. 6.5)
• Arm lift (Vgt32", Eq. 6.7)
• Vertical lower
• Stoop lower (Vlt32", Eq. 6.8)
• Squat lower (Vlt32", Eq. 6.9)
• Arm lower (Vgt32", Eq. 6.10)

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Tasks - 2

• Walk/carry/hold
• Walk (Eq. 6.11)
• Carry arms length (Eq. 6.12)
• Carry at waist (Eq. 6.13)
• Hold arms length (Eq. 6.14)
• Hold at waist (Eq. 6.15)
• Hold out in one hand (Eq. 6.16)
• Push/pull
• 32" bench height (Eq. 6.17)
• 60" height (Eq. 6.18)

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Tasks - 3

• Lateral arm work
• Both hands 180 (Eq. 6.19)
• One hand 180 (Eq. 6.20)
• Stand 90 (Eq. 6.21)
• Sit both hands 90 (Eq. 6.22)
• Sit one hand 90 (Eq. 6.23)
• Horizontal arm work
• Stand (Eq. 6.24)
• Sit (Eq. 6.25)

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Major Variables/Modifiers

• Individual characteristics
• Gender
• Weight
• Working style posture, speed
• Task characteristics
• Frequency
• Load
• Vertical range
• Grade of surface

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Comments - 1

• Two regions for lift/lower
• 0-32 (lift body weight)
• gt32 (lift arms only)
• Freestyle lift average stoop squat lifts
• Lift and lowers could have horizontal component
  (in addition to vertical)

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Comments - 2

• Estimate speed
• 2 mph 88 steps/min
• 3 mph 108 steps/min
• Climbing stairs
• ?E(per step) 0.1 0.0014 (BWL)
• ACU lbs, in, mph,

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Ex. 1 Box Lifting

• 160 lb male, lifting 20 lb boxes, 10/min, from
  30" bench to 40" conveyor
• Required tasks?

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Gargs Model
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Ex. 1 Box Lifting

• 160 lb male, lifting 20 lb boxes, 10/min, from
  30" bench to 40" conveyor
• Stoop lift 30"? 32"
• ?E 10-40.375BW(32-h1) (1.63L 0.875
  SL)(h2-h1)
• ?E 10-40.375(160)(32-30) (1.63(20)
  0.875(20))(32-30)
• 0.0235 kcal/lift
• 2) Arm lift 32"? 40"
• ?E 10-40.06BW(h2-32) (3.22L - 0.53
  SL)(h2-h1)
• ?E 10-40.06(160)(40-32) (3.22(20) - 0.53
  (20))(40-32)
• 0.0507 kcal/lift

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Ex. 1 Box Lifting cont

• 3) Arm lower 40"? 32" (no load)
• ?E 10-40.09BW(h2-32) (1.03L 0.37
  SL)(h2-h1)
• ?E 10-40.09(160)(40-32) 0.0115 kcal/lower
• 4) Stoop lower 32" ? 30" (no load)
• ?E 10-40.31BW(32-h1) 0.78L(h2-h1) 13.25
  S(32-h1)
• ?E 10-40.31(160)(32-30) 13.25(2) 0.0125
  kcal/lower
• Standing posture E 0.0109BW 0.0109(160)
  1.744 kcal/min

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Ex. 1 Box Lifting Total E

• Ejob  ?Eposture time ??Etasks
•                         time 
• ??Etasks 100.0235 0.0507 0.0115 0.0125
  
• 0.982 kcal
• Ejob  1.744(1) 0.982 2.73 kcal/min
•                                   

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Validation

• Stepwise multiple regression, with 3 males and 3
  females, r2 0.98
• Literature 20 tasks, difference of 2.9 to 38,
  average 13.8
• Field work 16 tasks, average difference 5.6
• Garg found overprediction
• Beginners typically underpredict
• Best feature relative comparison for redesign
  (careful with absolute values)

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Gargs Model
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