J. D. Power survey reports seats in car are next to last in satisfaction despite historical high in quality. Add-on content to basic seat design does not change satisfaction rank. Since seats are for sitting, drivers must not be able to sit as they prefer. Car seat design guidelines must improve accommodation for variation in sitting postures.

1. Seat Design
for Driver Satisfaction
Mac Reynolds, Ph.D.
Professor Emeritus, Michigan State University
CEO, ERL LLC

2. Today, cars designed and
built for quality,
appearance and
performance.

3. J. D. Power (2012) reports,
Seat Quality at Historical
High; Seat Satisfaction
Low.

4. Heater
Lumbar
J. D. Power also found
CONTENT makes seats
better, not satisfactory.
Leather
Bolsters

5. What’s the problem?

6. Seats, Sitting & Satisfaction
• Seat position satisfies body size.
• Drivers dissatisfied with sitting postures.
• Seat satisfaction meets driver preferences.

7. Evolution
of driver
1893 seat
design
2012

8. 19th Century Seats
Passenger
Comfort
Driver controls
horses!

9. Source most useful for seat design and
development? (LinkedIn Survey)
Experience 15 (48%)
Consumer surveys 6 (19%)
Driver ride tests 2 ( 6%)
DHM software 5 (16%)
Other 3 (10%)
Seats designed 73% from
experience with iterative
prototypes.

10. Drivers evaluate car seats!

11. Who are the drivers?
• Engineers in prototype seats
• Press in production vehicles
• Owners in production vehicles

12. Small Female Expert in
Production Vehicle says,
“…cushion - a little long
…head rest - a little hard to move, orientation bad
…too close to steering wheel
…back rest lateral too low and are pushing my arms”
Comfort Score: 3.5/5.0

13. Digital Human Model (DHM)
in Production Vehicle says,
Virtual output:
Cushion too long;
Head restraint too close;
SW too close;
Seatback wings wide;
Cushion wide;
Pedal too far
Comfort Score 3.65/5.0
US Patents: #6,840,125, #7,047,831, #7,347,114, #7,797,138

14. Can Seat Design in CAD
with DHMs improve
Basic Seat Design?
US Patents: #6,840,125, #7,047,831, #7,347,114, #7,797,138

15. Seat Design
for Driver Satisfaction
Seat must accommodate
variation in drivers’ body size
and preferred sitting postures.

16. Seat Design in CAD
Size Stiffness
Sitting Surface on seat frame for all occupants.
Shape
US Patents: #6,840,125, #7,047,831, #7,347,114, #7,797,138

17. Designer creates
surface for style
and comfort.
US Patents: #6,840,125, #7,047,831, #7,347,114, #7,797,138

18. Engineer designs Head Restraint
for safety and comfort.
Small Head
Female Restraint
FMVSS 202a
US Patents: #6,840,125,
#7,047,831, #7,347,114, #7,797,138

19. Design Seat for
Driver Satisfaction
Comfort Score = 9.4/10.0
US Patents: #6,840,125, #7,047,831, #7,347,114, #7,797,138

20. Models for Seat Satisfaction
• Virtual Driver (DHM)
• Virtual Sitting Surface
• Virtual Car Interior
• Drivers’ Comfort
• Optimization

21. Body Size & Back Posture
Small Medium Large
Vision Personal “Oscar”
Sitting
Preference Space
US Patents: #6,840,125, #7,047,831, #7,347,114, #7,797,138

22. Driver’s Sitting Structures
Anatomical
4th Chest vertebra
Landmarks
8th Chest vertebra
4th Lumbar
4th Lumbar
Hip
Thigh Pelvic
CG Ischium
Deflected
Tissue
Shape
US Patents: #6,840,125, #7,047,831, #7,347,114, #7,797,138

23. All Driver Landmarks
define 9 Sitting Surfaces
Head
1
Shoulders (T4)
2
Chest (T8)
3
Lumbar (L4)
4
Front of Buttocks (Hip)
Thigh 5
Thigh
CG Pelvis 6
(IT)
7
8
Load-Bearing Landmarks (L) 9
Contact and Space Landmarks(C)
US Patents: #6,840,125, #7,047,831, #7,347,114, #7,797,138

24. Size, Weight & Posture of
all 9 DHMs define Seat Surface
Seat Surface
Body
Weight
Deflection
9 IT
Cross
Sections
US Patents: #6,840,125, #7,047,831, #7,347,114, #7,797,138

25. Seat Designed for
Variation in
Driving Postures
Reach
Seat
US Patents: #6,840,125, #7,047,831, #7,347,114, #7,797,138

26. Seat Designed for Ergonomics,
Safety & Driver Satisfaction
Reach Head Restraint
(FMVSS 202a)
US Patents: #6,840,125, #7,047,831, #7,347,114, #7,797,138

27. Engineers evaluate Seat
Design for Manufacturing
Body Frame
Foam
Manufacturability
Penetration Meat-to-Metal
US Patents: #6,840,125, #7,047,831, #7,347,114, #7,797,138

28. Seat Design TOTAL Score: 7.70
Seat Cushion: 4.78
Measured
Cushion contact length is short.
Cushion provides not enough thigh support.
Cushion insert stiffness is just right.
Seat Back: 8.77
for Drivers’ The upper seat back is just right.
Overall Wing shape provides good support.
Seat back Insert shape provides good support.
Comfort
Seat back insert stiffness is just right.
Head Restraint patch contact is far.
Lumbar patch contact is just right.
Package: 9.82
Travel window requires no additional travel.
Package provides comfortable head room.
Seat can support driver vision requirements.
USA TOTAL Cushion Back Package Steering Wheel to chest is just right.
Steering Wheel to thigh is just right.
TOTAL (1-10) 7.70 4.78 8.77 9.82
Driver can comfortably reach pedal.
Small Female 6.65 5.50 8.37 8.27 Joint Angle Penalties:
Medium Male 7.91 4.89 8.83 10.00 Seat: 0.8 % Package: 1.6 %
Large Male 7.26 3.20 8.72 9.93

29. Validation: Model evaluates
Comfort same as Driver
4.8
Lux Sedan
4.6
DHMs Comfort Score (1-5)
Mid Sedan
Mid Xover
4.4 FST Mid SUV
Sm Xover
4.2
4
Sm Sedan
r = 0.8
3.8
3.6
3.4
3.4 3.6 3.8 4 4.2 4.4 4.6
Drivers' Scores in 7 Vehicles (1-5)

30. All Global Drivers
have Universal Needs
• Vision
• Operate Controls
• Sitting in preferred posture

31. Body Size of Global Drivers

32. Alert Neutral
Driving Conditions
affect Preferred Posture
Relaxed Alert

33. Back posture preference
changes eye height of driver.
Alert Neutral Relaxed
44.4 mm
US Patents: #6,840,125, #7,047,831, #7,347,114, #7,797,138

34. Seat Design for posture variation
changes seat position in car
Production seat
modification
(+)
20 mm Neutral
Posture
(-)
Slumped
Posture
Seat position:
19 mm forward

35. Does design beat competition?
(Small Female)
Saab 9-5 VW Passat
Cushion length is
too long too short
Cushion thigh region provides
too much pressure no support
Cushion thigh insert width is
too narrow too wide
Cushion ischial insert width is
too narrow too wide
Head restraint surface is
too close too far
US Patents: #6,840,125, #7,047,831, #7,347,114, #7,797,138

36. Design for Driver Satisfaction
can START at Vehicle Concept
US Patents: #6,840,125, #7,047,831, #7,347,114, #7,797,138

37. Conclusion
Improved seat satisfaction comes
from design for all sitting preferences.

38. Acknowledgements
• ERL LLC (Ray Brodeur, D.C., Ph.D., et al.)
• Michigan State University (George Stockman, Ph.D., et al.)
• General Motors Corporation (Don Maertens, et al.)