Data Requirements for Simulating
Vehicle Dynamics
Thomas D. Gillespie, Ph.D.
Director of Product Planning
Mechanical Simulation Corporation, Ann Arbor, Michigan
Overview
• Simulation is an important tool in automotive products development
– For tuning basic chassis dynamics
– Test platform for developing active safety systems and controllers
– Sand box for working out advanced driver assistance system technologies
• Intuitive user interfaces make simulation easier to use with less training
• Users still face the difficulty of “getting started”
– Becoming familiar with the program structure and user interface
– Finding data to characterize the vehicle (100s of numbers are required)
– Setting up test procedures (controlled maneuvers and test sites)
• This presentation will examine some of the methods we use in CarSim to
help the user overcome these barriers
CarSim Data Resources
• Inexperienced new customers face three challenges;
– How to set up a vehicle data set
– What tests should be performed
– Where to perform the tests
• CarSim fills these needs by means of:
– Data sets for all classes of vehicle
– Multiple example runs covering the most common tests
– Multiple roads and proving grounds test sites
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The CarSim Vehicle Family
Start simulating immediately – choose from data sets for generic vehicles
A-class
Hatchback
F3
B-class
Hatchback,
Sports car
C-class
Hatchback
GT
3-Wheeler
Trailers
D-class
Minivan,
Sedan, SUV
Euro Van
E-class
Sedan, SUV
F-class
Sedan
Pickup
Mini Truck
Tractors
CarSim Database
• Assemble simulation
datasets from sub-system
data sets
– Vehicle data sets
– Test procedures
– Test sites
• 160+ libraries
(screens) are available
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“Rules of Thumb” for Vehicle Properties
Passenger Car
Light Truck
Rule Of
Avg. Measured
Avg. Measured
PARAMETER
Thumb
+/- 95% Confidence Limit
+/- 95% Confidence Limit
C.G. Height
21.0 in.
21.29 in. +/-1.5 in
26.71 in. +/-4.0 in.
C.G. Height
40% of Hr
39% +/- 2.6%
38.7% +/-3.5%
Pitch Inertia
M*a*b
(1.07 +/-0.17)*Mab
(1.04 +/-0.22)*Mab
Roll Inertia
.25*M*T*Hr
(0.73 +/-0.13)*.25MTHr
(0.67 +/-0.16)*.25MTHr
Yaw Inertia
=Roll Inertia
(1.03 +/-0.08)Pitch Inertia
(1.00 +/-0.10)*Pitch Inertia
Hr= roof height(in)
M= vehicle mass
a= longitudinal distance from C.G. to front axle (in)
b= longitudinal distance from C.G. to rear axle (in)
T= Average of front & rear track width (in)
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NHTSA Estimates of Properties (cont’d)
INERTIA ESTIMATIONS AS A FUNCTION OF WEIGHT
PASSENGER CARS
Regression Coefficient
Pitch Inertia
=.99W -1149.0
R^2=0.89
Roll Intertia
=.18W -150.0
R^2=0.80
Yaw Inertia
=1.03W -1206.0
R^2=0.88
Pitch Inertia
=1.12W -1657.0
R^2=0.70
Roll Inertia
=0.22W -235.0
R^2=0.70
Yaw Inertia
=1.03W -1343.0
R^2=0.73
LIGHT TRUCKS
Inertia units: (ft*lb*sec^2)
Weight units: (lb)
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Data Sources for Vehicle Properties
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NHTSA Measurements (Garrott, Monk & Chrstos, SAE 881767 )
UMTRI Factbook of the Mechanical Properties of Heavy-duty Trucks
UMTRI Mechanics of Heavy-duty Trucks Course Notes
Car & Driver data on vehicle properties and performance
Bosch Automotive Handbook
Metz, et al., SAE Paper 900760 with tire and wheel properties
Tire and Rim Association Yearbook
Manufacturers technical specifications (internet, etc.)
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Example: Mass and Wheelbase by Class
3000
2500
Mass (kg)
F
D
2000
B-class
B
1000
0
2000
C-class
E
1500
500
A-class
2400
E-class
C
A
2200
D-class
2600
2800
Wheelbase (mm)
F-class
3000
3200
3400
Example Test Procedures
• Users also need test
procedures to evaluate
performance
• Multiple tests provided
on the Run Screen
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Acceleration
Braking
Ride
Handling
Rollover
Classical Vehicle Dynamics Tests
• Acceleration/powertrain performance
– On-road power limited acceleration
– Off-road traction limited performance
Classical Vehicle Dynamics Tests
• Fuel Consumption • Optimization
– EPA Urban cycle
– EPA Highway cycle
– Aerodynamics and rolling resistance
– Powertrain gear ratios
2.54 kg/12.096 km
(27 liters/100 km)
+
=
2.47 kg/12.096 km
(26.3 liters/100 km)
Classical Vehicle Dynamics Tests
• Brake performance evaluation
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–
–
–
ABS performance on split mu
Stopping distance
Friction utilization
FMVSS and ECE 13H
compliance
Tractor tandem
Lock up
0.34
0.4
Ideally all would
be at the same
friction
utilization level
Classical Vehicle Dynamics Tests
• Handling
–
–
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–
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Lane changes
ISO constant radius understeer
Fishhook
Sine with dwell
Transient response
Classical Vehicle Dynamics Tests
• Ride
–
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Bounce, pitch and roll
Road roughness
Chassis flex
Suspended cabs (TruckSim)
Engine shake/vibrations
Classical Vehicle Dynamics Tests
• Steering system evaluation
– Static steer
– O-center
– Sine sweep
Static Steer
On-center
Sine sweep
Advanced Procedures
• Sensors
– Tools for developing advanced driver assistance systems
Advanced Procedures
• Vehicle-to-vehicle communication
– SAE Standard safety message (10 times/sec)
– Dedicated Short-range Communication System
– Data exchange with neighboring vehicles
Advanced Procedures
• Events
– Monitor simulation progress and change parameters
– Simulate tire blowouts, crosswinds
– Construct complex maneuvers
Tire blowout
Reverse turn
Advanced Procedures
• Integration with other software and hardware systems
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Simulink
AVL Cruise
Pacejka 5.2 tire model
MF Tyre, MF Swift
COSIN Ftire
dSPACE
ETAS
LabVIEW
Etc.
Thank You
Contact Information:
Tom Gillespie, [email protected]
www.carsim.com
Stand #1167