Auto/Steel
Partnership
Preliminary Vehicle Mass Estimation
Using Empirical Subsystem
Influence Coefficients
Donald E. Malen
University of Michigan
A project supported by the
Auto/Steel Partnership
www.autosteel.org
Mass Estimation in
Vehicle Design
Auto/Steel
Partnership
Fuel Economy
Handling
Qualities
Vehicle
Mass
Acceleration
Performance
Subsystem
Selection
and sizing
www.autosteel.org
Vehicle
Development Stage
Auto/Steel
Partnership
PreConfiguration
Configuration
Product
Planning
Detail
Advance Vehicle
Development
Decide if vehicle
concept is consistent
with mission
What is mass if
designed as a
typical vehicle for
this size and class?
Decide which
configuration is best in
meeting vehicle goals
Engineering
Factory
Control mass
growth to targets
What is mass if
configuration is changed
from typical vehicle?
www.autosteel.org
Mass Estimation In The
PreConfiguration Stage
Auto/Steel
Partnership
•Type of Vehicle
•Number of Passengers
•Cargo Mass
Plan View Area
Mass of Nominal
Vehicle for Size and
Vehicle Category
www.autosteel.org
Vehicle
Sample
Auto/Steel
Partnership
2004 VW Touareg
2004 Nissan Murado
2004 Toyota Sienna
2004 Toyota Prius
2003 Toyota Camry (US)
2003 BMW 330i
2003 Infiniti G35
2003 Honda Accord
2003 Toyota Corolla Sedan
2002 Audi A4
2007
Cadillac SRX
Chevrolet HHR
Saturn Outlook
GMC Sierra Crew Cab
Chevrolet Colorado
Chevrolet Impala
Pontiac G6 SE1
Cadillac STS
GMC Yukon
Saturn Vue
Sedans:
14
SUV:
12
Pick Up:
5
Van:
2
2002 Honda Civic LX
2003 Honda Accord EX
2003 PT Cruiser
2003 Toyota Matrix XRS
2003 Toyota Tacoma 4x2
2004 Dodge Ram 4x4
2004 Nissan Titan LE
2004 Toyota Highlander Premium
2004 Toyota Sienna
2005 Honda Odyssey Touring
2005 Jeep Liberty
2005 Jeep Wrangler
33
www.autosteel.org
Data for
Each Vehicle
Auto/Steel
Partnership
Functional Subsystem
Body Non-Structure
Body Structure
Front Suspension
Rear Suspension
Steering
Brakes
Powertrain
Fuel and Exhaust
•Vehicle Category
•Vehicle overall dimensions
•Curb Mass
•Number of Passengers
•Cargo Mass
•Gross Vehicle Mass
•Subsystem Mass
Wheels and tires
Air Conditioning
Electrical
Bumpers
Closures
www.autosteel.org
Subsystem Mass as a
Fraction of Curb Mass
Auto/Steel
Partnership
Body Non-structural 0.204
Body Structure
0.227
Front Suspension
0.049
Rear Suspension
0.044
Braking
0.032
Sedan
0.118
Transmission
0.067
Power Train
0.185
0
Fuel and Exhaust
0.040
Steering
0.014
Tires & Wheels
0.065
Electrical
0.046
Cooling
0.027
Bumpers
0.022
Closures
0.046
No
Bo nst
Fr dy ruc
on S tu
r
t
Re t Sus ruct al
ar
pe ure
Su ns
sp ion
en
Br sion
ak
in
Tr
an Eng g
i
s
Po mis ne
Fu w e s i o
el
rT n
&E ra
x h in
T ir
a
es Steeust
&
W r in g
Ele heel
c tr s
C o ic a
o l
Bu ling
mp
Cl ers
os
ure
s
Engine
0.3
0.2
0.1
www.autosteel.org
Curb Mass vs.
Plan View Area
Auto/Steel
Partnership
curb mass = 147.75(PVA) + 229.59
Curb Mass (kg)
curb mass = 206.11(PVA) 0.9212
2000 Sedans
1600
1200
800
400
0
2
4
6
8
10
Plan View Area (m2)
www.autosteel.org
12
An
Example
Auto/Steel
Partnership
A new vehicle is in the planning stage (pre-configuration).
Target Specifications
5
passengers
120 kg
cargo capacity.
1815 mm
Vehicle width
4732 mm
length
2250 Lb
test weight class for fuel economy
(~885kg curb mass)
www.autosteel.org
Step 1: Pre Configuration
Mass Estimation
Auto/Steel
Partnership
For Sedans
Vehicle Curb Mass
curb mass (kg) = 147 . 75 A ( m 2 ) + 229 . 59
A = (1 . 815 m )( 4 . 732 m ) = 8.59m2
curb mass = ~1500kg
Target: 885kg
Subsystem Mass
(Body Non-structure mass) = 0.204 (Curb Mass)
(Body Non-structure mass) = ~306 kg
www.autosteel.org
Auto/Steel
Partnership
Software Tool: Pre Configuration
Mass Estimation
Mass of Nominal
Vehicle for Size and
Vehicle Category
www.autosteel.org
Mass Estimation In The
Configuration Stage
Auto/Steel
Partnership
What is mass if configuration is changed from typical vehicle
(mass saving materials or technology)?
Mass of Nominal Vehicle
Subsystem Mass reductions
from nominal vehicle
enabled by technologies
www.autosteel.org
Mass of Vehicle
resized for alternative
subsystems
Auto/Steel
Partnership
Step 2: Mass Reduction Technologies
Step 3: Sort Technologies by Cost
subsystem
For a vehicle
with curb
mass=1500kg,
what are mass
reduction
technologies?
mass reduction technology
mass
savings
cost
cost/unit
mass (mc)
kg
$
$/kg
Tire& wheel
Min. cap. wheels and tires
20.00
-20
-1.000
non structure
sound treatment opt
19.45
-5
-0.257
Braking
optimized pedal bracket
3.00
0
0.000
rear susp
shape optimization
6.59
0
0.000
body struct
joint improvements
15.00
0
0.000
closures
hardware: bar stock
10.00
0.1
0.010
front susp
shape optimization
7.34
0.2
0.027
body struct
AHSS optimization
70.00
3
0.043
non structure
reduce glass thickness
5.00
0.3
0.060
non structure
IP substrate optimization
21.43
2
0.093
Braking
tubular pedals
4.00
0.4
0.100
non structure
seat frame shape
optimization
40.00
5
0.125
closures
AHSS optimization
Fuel&Exhaust
lower gage of exhaust
Include all
12.46
2
0.161
technologies
with
5.99
1cost ≤0.1
0.167
marginal
www.autosteel.org
Primary Mass
Reduction
Auto/Steel
Partnership
Subsystem
Non Structure
Body Structure
Front Suspension
Rear Suspension
Braking
Powertrain
Fuel and exhaust
Steering
Tire & Wheels
Bumper
Closures
Mass
reduction
100.88kg
85.00
7.34
6.59
7.00
27.72
5.99
2.00
20.00
4.95
22.46
289.93kg
This configuration of technologies provides a
primary mass reduction total of ~290kg.
Curb Mass from Pre-Configuration=
Primary Mass Savings from
alternative configurations
www.autosteel.org
1500
-290
1210
Target: 885
Mass
Compounding
Auto/Steel
Partnership
An unplanned mass increase in a component during
vehicle design has a ripple effect throughout the vehicle;
other components need to be resized
increasing vehicle mass even more.
mass begets mass
www.autosteel.org
Subsystem Mass
Influence Coefficient
Auto/Steel
Partnership
Subsystem Weight
wi
influence coefficient
γi =
∂ wi
∂W S
Ws
γi
Gross Vehicle Weight
Ws
www.autosteel.org
Example of Mass
Compounding
Auto/Steel
Partnership
•1000 kg GVM
•10 kg of initial mass change
•vehicle mass influence coefficient = 0.4
1000
Gross
Vehicle
Mass
kg
Primary mass
change
990
Secondary mass
change, due to
resizing subsystems
983.3
980
0
1
0.4*10
0.4*(0.4*10)
2
3
4
5
6
7
8
9
Resizing Iteration
0.4*(0.4*(0.4*10))
www.autosteel.org
Mass Compounding
Formula
Auto/Steel
Partnership
Initial Vehicle Mass
Mass Change (primary)
Mass Change from resizing (secondary)
Compounded
Vehicle Mass
WV∞ = W0 + Δ + ΔΓV
⎡ γV ⎤
ΓV = ⎢
⎥
(
1
−
)
γ
V ⎦
⎣
n
γ V = ∑ γ i Vehicle influence coefficient is sum
i =1
of subsystem influence coefficients
www.autosteel.org
Modeling Subsystem
Mass Dependency
Auto/Steel
Partnership
Body
Structure
mass
Vehicle Mass
strong dependence
Spatial
moderate dependence
Configuration
•BFI, BOF
Performance
•refinement level
subsystem mass = f (gross vehicle mass,
vehicle area, configuration, performance)
Reduced linear model
subsystem mass = C0+C1(gross vehicle mass)+ ε
www.autosteel.org
Subsystem Mass
Dependency
Auto/Steel
Partnership
Functional Subsystem
Vehicle
Spatial
Mass (veh.vol, area)
Config.
Body Non-Structure
Performance
Level
•refinement level
Body Structure
•BFI, BOF
•safety star rating
Front Suspension
•Strut, SLA
•handling / isolation level
Rear Suspension
•Ind, etc.
•handling / isolation level
Steering
•Mech, Rack
Brakes
•FW, RW, AW
•Long, Trans.
Powertrain
Fuel and Exhaust
•acceleration level
•fuel economy level
•range
•noise level
Wheels and
tires
•styling level
Air Conditioning
•time-to-cool
Electrical
•option loading level
Bumpers
•low speed impact level
Closures
www.autosteel.org
Subsystem Mass
vs. GVM
Auto/Steel
Partnership
Tires & Wheels
Tires & Wheels Mass
180
160
140
Sedan
120
SUV
100
Pick Up
80
Minivan
60
γ =0.049
40
20
0
0
1000
2000
3000
GVM
www.autosteel.org
4000
Auto/Steel
Partnership
Influence Coefficient
Summary
0.3
γ
0.2
0.1
Bo
dy
St
ru
Fr
ctu
on
re
tS
us
pe
Re
ns
ar
ion
Su
sp
en
sio
n
Br
ak
ing
Po
we
rT
Fu
ra
in
el
&
Ex
ha
us
t
St
ee
r in
Tir
g
es
&
W
he
e ls
Bu
mp
er
s
0.0
All Vehicles category
1975 Study
1981 Study
www.autosteel.org
Secondary Mass
Savings
Auto/Steel
Partnership
Secondary
Mass
Savings
per
unit
primary
change
⎛
γV
⎜⎜ ΓV =
1− γV
⎝
2.5
2.0
1.5
1.0
⎞ 0.5
⎟⎟
⎠ 0.0
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Vehicle Mass Influence Coefficient γ V
All subsystems free to resize
All subsystems less powertrain
www.autosteel.org
0.8
Auto/Steel
Partnership
Step 4: Estimate Vehicle
Mass Using Mass Compounding
Primary mass savings
Δ= 290kg
⎡ γV ⎤
Secondary mass savings = Δ ⎢
⎥
γ
(
1
−
)
V ⎦
⎣
Taking a nominal value for the vehicle influence coefficient; γV = 0.53
⎡ γV ⎤
⎢
⎥ =1.128
⎣ (1 − γ V ) ⎦
for a secondary mass savings = (1.128) 290kg = 327kg
Curb Mass from Pre-Configuration
=
Primary Mass Savings from alternative configurations
Secondary Mass Savings from resizing to new GVM
1500
-290
-327
883
Target: 885kg
www.autosteel.org
Auto/Steel
Partnership
Software Tool:
Mass Compounding
Resize all subsystems with GVM dependency
Mass of resized
vehicle for mass
saving
technologies
www.autosteel.org
Auto/Steel
Partnership
Software Tool:
Mass Compounding
What is effect if Powertrain cannot be resized?
www.autosteel.org
Auto/Steel
Partnership
Mass Estimation In
Preliminary Vehicle Design
•Rational approach to preliminary mass allocation
•Effects of mass reduction technologies taken into account
•Based on contemporary vehicles
•Estimation requires only sparse data available
•Adequate precision for decision making
•Fast
CD available from AISI with Spreadsheet and technical report
www.autosteel.org
Acknowledgments
Auto/Steel
Partnership
•Work sponsored by
Auto/Steel Partnership
Future Generation Passenger Compartment Group
Jody Shaw Chair
•Contributions
Kundan Reddy, UM Masters Candidate
•Contact
Jody Shaw, US Steel
Donald E. Malen, UM
[email protected]
[email protected]
www.autosteel.org