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Seat Design for Driver
SatisfactionMac Reynolds, Ph.D.
Professor Emeritus, Michigan State University
CEO, ERL LLC
Today, cars designed and built for quality,
appearance and performance.
J. D. Power (2012) reports,
Seat Quality at Historical High; Seat
Satisfaction Low.
J. D. Power also found
CONTENT makes
seats better, not
satisfactory.
LumbarHeater
Leather
Bolsters
What’s the problem?
Seats, Sitting & Satisfaction
• Seat position satisfies body size.
• Drivers dissatisfied with sitting
postures.
•Seat satisfaction meets driver
preferences.
Evolution of
driverseat
designPositio
n
1967Safety
Ergonomi
cs
1893
2012
19th Century Seats
Passenger
ComfortDriver
controls horses!
Seats designed 73% from experience with iterative prototypes.
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%)
Drivers evaluate car seats!
Who are the drivers?
•Engineers in prototype
seats
•Press in production
vehicles
•Owners in production
vehicles
“…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
Small Female Expert in Production Vehicle
says,
Digital Human Model (DHM)
in Production Vehicle says,
US Patents: #6,840,125, #7,047,831, #7,347,114, #7,797,138
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
Can Seat Design in CAD with DHMs
improve Basic Seat Design?
Seat must accommodate variation in drivers’ body size and preferred sitting
postures.
Seat Design for Driver
Satisfaction
Seat Design in CAD
Sitting Surface on seat frame for all occupants.
Size
Shape
Stiffness
US Patents: #6,840,125, #7,047,831, #7,347,114, #7,797,138
Designer creates surface
for style and comfort.
US Patents: #6,840,125, #7,047,831, #7,347,114, #7,797,138
Engineer designs Head Restraint for safety and
comfort.
FMVSS 202a
Head Restraint
Small Femal
e
US Patents: #6,840,125, #7,047,831, #7,347,114,
#7,797,138
Design Seat for Driver
SatisfactionComfort Score = 9.4/10.0
US Patents: #6,840,125, #7,047,831, #7,347,114, #7,797,138
Models for Seat Satisfaction
• Virtual Driver (DHM)
• Virtual Sitting Surface
• Virtual Car Interior
• Drivers’ Comfort
• Optimization
Body Size & Back Posture
US Patents: #6,840,125, #7,047,831, #7,347,114, #7,797,138
Vision
Space
Personal Sitting
Preference
Small
Large
Medium
“Oscar”
Driver’s Sitting Structures
Anatomical
Landmarks
Deflected
Tissue Shape
4th Lumbar
US Patents: #6,840,125, #7,047,831, #7,347,114, #7,797,138
4th Chest vertebra8th Chest vertebra
Hip
Pelvic Ischiu
m
Thigh
CG
4th Lumbar
All Driver Landmarks define 9 Sitting
Surfaces
Load-Bearing Landmarks (L) Contact and Space Landmarks(C)
Shoulders (T4)
Chest (T8)
Lumbar (L4)
Buttocks (Hip)
Pelvis
(IT)
Thigh CG
Head
Front of
Thigh
US Patents: #6,840,125, #7,047,831, #7,347,114, #7,797,138
1
2
3
45
67
8
9
Size, Weight & Posture of all 9 DHMs define Seat Surface
9 IT Cross Sectio
ns
Seat Surface
Wing
Body Weight Deflecti
on
US Patents: #6,840,125, #7,047,831, #7,347,114, #7,797,138
Seat Designed for Variation in
Driving Postures
Line of Sight
Reach
US Patents: #6,840,125, #7,047,831, #7,347,114, #7,797,138
Seat
Seat Designed for Ergonomics, Safety & Driver Satisfaction
US Patents: #6,840,125, #7,047,831, #7,347,114, #7,797,138
Head Restraint (FMVSS 202a)
Reach
Engineers evaluate Seat Design for Manufacturing
US Patents: #6,840,125, #7,047,831, #7,347,114, #7,797,138
Foam Manufacturabilit
y
Body
Frame
Penetration
Meat-to-Metal
Seat Design Measured for Drivers’
Comfort
USA TOTAL Cushion
Back Package
TOTAL (1-10)
7.70 4.78 8.77 9.82
Small Female
6.65 5.50 8.37 8.27
Medium Male
7.91 4.89 8.83 10.00
Large Male 7.26 3.20 8.72 9.93
TOTAL Score: 7.70Seat Cushion: 4.78 Cushion contact length is short. Cushion provides not enough thigh
support. Cushion insert stiffness is just right. Seat Back: 8.77 The upper seat back is just right.
Overall Wing shape provides good support.
Seat back Insert shape provides good support.
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. Steering Wheel to chest is just right. Steering Wheel to thigh is just right. Driver can comfortably reach pedal.
Joint Angle Penalties: Seat: 0.8 % Package: 1.6 %
Validation: Model evaluates Comfort same
as Driver
3.4 3.6 3.8 4 4.2 4.4 4.63.4
3.6
3.8
4
4.2
4.4
4.6
4.8
f(x) = 0.618506493506493 x + 1.83693181818182R² = 0.618622470722602
Drivers' Scores in 7 Vehicles (1-5)DH
Ms C
om
fort
S
co
re (
1-
5) Sm Sedan
Mid Xover
Lux SedanMid
Sedan
Sm Xover
FST Mid SUV
• Vision• Operate Controls• Sitting in preferred posture
All Global Drivers have Universal
Needs
Body Size of Global Drivers
Driving Conditions affect Preferred
Posture
Alert
AlertRelaxed
Neutral
Back posture preferencechanges eye height of
driver.Alert Neutral Relaxe
d44.4 mm
US Patents: #6,840,125, #7,047,831, #7,347,114, #7,797,138
Slumped Posture
Neutral Posture
Seat Design for posture variation changes seat
position in car
20 mm
Seat position:19 mm forward
(-)
(+)
Production seat
modification
Cushion length is
Cushion thigh region provides
Cushion thigh insert width is
Cushion ischial insert width is
Head restraint surface is
Saab 9-5 VW Passat
too shorttoo long
too much pressure
no support
too widetoo narrow
too fartoo close
too narrow too wide
US Patents: #6,840,125, #7,047,831, #7,347,114, #7,797,138
Does design beat competition?(Small Female)
Design for Driver Satisfaction can START at Vehicle Concept
US Patents: #6,840,125, #7,047,831, #7,347,114, #7,797,138
Conclusion
Improved seat satisfaction
comes from design for all
sitting preferences.
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.)
