Brazil Seat Ergonomics & Vibration Talk

8/20/2019 Brazil Seat Ergonomics & Vibration Talk

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Driver Ergonomics and

Whole Body Vibration

Eckardt Johanning M.D. M.Sc.

http://www.iso.org/iso/en/ISOOnline.frontpage



The problem – The Aching Back

• Risk analysis:

• Repetitive mechanical stress:

vibration and shock• Posture: Seat

• Exposure duration & break time: Schedule

• Health complaints/disorders and injuries



Where do you find Vibration?

Hand-ArmWhole Body

In Buildings



Tested yard switcher GP40-2 - January 27, 2004







DEFINITION OF WHOLE BODY

VIBRATION

• Mechanical

v ibrat ion that, when

transm it ted to the

who le body , entai ls

r isks to the heal th

and safety o f

workers, inpart icular low er

back morb id i ty and

traum a of the sp ine.


http://www.europa.eu.int/index_en.htm



VIBRATION

• Began with the

Industrial Revolution.

• Humans exposed to

oscillatory motions

(vibration) for the firsttime when working

with powered

equipment.Eckardt Johanning M.D. M.Sc.



WHAT IS SHOCK & VIBRATION?


Simples vibration

Two dominant frequencies

Complex vibrations:

multiple dominant frequencies



WHAT IS SHOCK & VIBRATION?




What is Whole Body

Vibration (WBV)?• Energy transmitted to the body as a whole,

through a supporting surface

• Important Factors:

– magnitude

– direction

– frequency



Measuring Vibration

• Acceleration: measure of vibration

• Vibration: magnitude and direction

• Measurements: three directions:

– x, y, z

• Units: meters per second squared

(m/s2)




The concept of Resonance effects: Magnification

Resonance is the tendency of a system to oscillate with larger amplitude at

some frequencies than at others.



CRITICAL

RESONANCE

RANGES OF

THE HUMAN

BODY.Eckardt Johanning M.D. M.Sc.



Vibration and Resonance Effects of Internal Organs of Humans







AGINGCROSS

ANATOMY &

MRI IMAGE




Spine aging and vibration related

degenerationMore and earlier damage






RISK FACTORS

Posture.

ExposureDuration.

RestPeriods.




MTA test bus – March 8, 2004



TWU test driver – WBV seat

test pad

Orion CNG Bus – built 5/03 9938 miles –

Seat: Recaro air suspension (ergo-metro)



Seat air suspension

adjustments

Problem: in extreme position – suspension impaired



MTA – controls….

Seat back support

adjustment problem

–restricted & hits

wall

MTA vibration

sensor



The Seat of old New York City Buses



Vertical Axis – Seat levelTime Sample

t

hh:m

m:ss aweq MTVV VDV

VDV/aw*T1/

4

MTVV/awe

q CF14:11:45 300 0:05:00 0.364 1.77 2.87 1.89 4.85 10.75

14:16:45 300 0:05:00 0.514 1.79 3.54 1.65 3.48 6.57

14:21:45 300 0:05:00 0.533 2.25 3.78 1.70 4.22 10.08

14:26:45 210 0:03:30 0.508 1.45 3.04 1.57 2.86 5.71

14:33:30 300 0:05:00 0.437 1.57 3.03 1.67 3.59 7.50

14:38:30 300 0:05:00 0.605 2.64 3.95 1.57 4.36 7.58

14:43:30 300 0:05:00 0.350 1.49 2.84 1.95 4.25 13.11

14:48:30 300 0:05:00 0.244 1.38 2.03 2.01 5.66 14.36

14:53:30 300 0:05:00 0.245 0.81 1.70 1.67 3.29 7.46

15:05:15 300 0:05:00 0.243 1.06 1.77 1.75 4.34 8.48

15:10:15 45 0:00:45 0.454 1.05 1.79 1.52 2.32 6.07

15:11:15 120 0:02:00 0.378 1.45 2.15 1.72 3.84 7.86

3075 0:51:15 0.42 2.64 5.59 1.79 6.28 12.79

Tri axial vibration bus (vs train) compared



Tri-axial vibration bus (vs. train) compared(seat and floor) (ISO 2631, 1997)

Vibration (aw rms) (mean) :

Fore-aft (x) 0.21 (0.18) m/s2,

Lateral (y) 0.19 (0.28) m/s2Vertical (z) 0.42 (0.32) m/s2.

Frequent and high shock levels:

The Crest factors (CF): 9-16 (>9)

Maximum Transient Vibration Value (MTVV/aw):5.13 (5. 26) (x),

4.34 (5.12) (y)

6.28 (4.81) (z)

Vibration Dose Value (VDV/aw T 1/4)

1.63 (1.32 to 2.3) (x-axis)1.7 (1.33 to 1.7) (y-axis)

1.79 (1.38 to 1.86) (z-axis)

Seat transmission factors (SEAT):

x:1.44 y:1.01 z:0.71 (1.44,1.2, 1)



STANDARDS


http://www.europa.eu.int/index_en.htm

http://www.ansi.org/

http://www.iso.org/iso/en/ISOOnline.frontpage



Summary and RxVibration and shock are recognized risk factors

for ergonomic stress and back disordersPreliminary and comparison testing of bus

operator seat shows that WBV are in asimilar range

New study of Railroad engineers reveals highlevel of back complaints and disorders

Transit workers study recommended based onpreliminary analysis of test data of “modelbus”



Summary and Rx

• Transit workers study

recommended based on preliminary

analysis of test data of “model bus” • Collaborative and participatory

principle

• Intervention study



How Do We Control Exposure

to Whole Body Vibration ?u Redesign or

engineering controls

u Maintain seatingsystems

u Administrative controls

u Anti-vibration seatcushions



Key Check Points –

Healthy Driving1. Seat adjustment (length)

2. Seat angle adjustment

3. Back support adjustment

4. Pedal angle adjustment

5. Seat height and pedal reach6. Knee angle (110-120 degree)

7. Leg/Thigh support easy

8. Steering wheel and

instruments (slightly angled

elbow)

9. Good back support without

pressure?

10. Head support (top above eye

level?)Eckardt Johanning M.D. M.Sc.



New Generation Bus Seats• Suspension seat adjustment

1. Height

2. Lumbar support

3. Lateral support

4. Backrest

5. Heater/ventilation6. Armrest

7. Armrest adjustment

8. Seat pan angle

9. Seat depth adjust.10. Fore/aft adjust.

11. Swivel

12. Vertical shock

absorber adjust.


Source: Grammer, Germany



•Change seatingposture frequently:

– Dynamic sitting –

move and change

posture• Inform yourself about

the bus seat and

driver adjustments

• Sit slightly backwardswith good contact to

back support

Eckardt Johanning M D M Sc

Think of

yourback

Take a break and move around!

Good sitting posture!

Brazil Seat Ergonomics & Vibration Talk

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