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Elementary Ergonomics Short Introduction to Biomechanics

Richard Goossens

EE, 25 Nov 2013

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Biomechanics Forces in and on body

Question 1: What forces act on us?

Question 2: How to design for it?

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Forces

Atmosphere

10 N/cm2

Gravity

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Zero gravity

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Zero gravity

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Problems

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Free body diagram

Cut loose

F, M

Equilibrium?

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Pressure

Gravity on surface

Stand up

Body 75 kg, feet 150 cm2 ≈ 2.5 N/cm2

Sit down

60% body, seat surface 1000 cm2 ≈ 0.5 N/cm2

Not uniformly distributed: 1- 2 N/cm2

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Aspects of comfortcapillarvessels

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What is maximum allowable pressure on skin?

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Time?

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Shear

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Deformation

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Human Pressure and Shear sensors

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Innovations

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Rule of thumb angles/forces/pressure

Comfort about 30% max

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Backrest needed?

B C

Back rest

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Muscle-length

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1500 N

Static

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Dynamic

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Force

Stay below 15% max

10% max (static)

How to determine max?

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Max?

Use existing data and rules of thumb

Woman = 30% less force than man

Elderly and child: 30% van 20-40 man/woman

P5 about 30% P50

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Exercise

Free body diagram

Estimate weight that can be hold all day

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End of this presentation

Thank you for your attention