utomotive enter case study i heavy duty truck...

AUTOMOTIVE RESEARCH CENTER

M916 - CASE STUDYarc

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Case Study ICase Study IHeavy Duty Truck M916A1/M870A2Heavy Duty Truck M916A1/M870A2

Jeff Stein

Dennis Assanis

ARC ConferenceJune 3 & 4, 1997

Ann Arbor, Michigan



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ObjectivesObjectives

• To develop 1st generation models and simulation tools for a complete vehicle:

- Powertrain and Vehicle Dynamics for vehicle mobility simulation

• To demonstrate for the M916 truck:- Proper handling models- Steering/braking for rollover

- Truck acceleration on flat road - Traction while hill climbing



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Why Select the M916 Tractor Semitrailer Why Select the M916 Tractor Semitrailer as an Exemplar?as an Exemplar?

• Represents an important class of “real-world” vehicle modeling issues

• The DDC Series 60 engine has been extensively simulated and tested at the University of Michigan

• Trailer parameters have been previously measured at UMTRI and other vehicle parameters were available



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ChallengesChallenges

• Test new methodologies with large, “real-world” models

• Integrate multiple ARC research projects

• Integrate Matlab-based Powertrain models with large nonlinear Vehicle Dynamics models

• Produce source code for equations of motion



5

Software EnvironmentsSoftware Environments• ArcSim: Vehicle Dynamics

• PowerSim: Powertrain & Vehicle Dynamics



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ArcSim: FeaturesArcSim: Features

• A user friendly and flexible Vehicle Dynamics simulation and animation environment

• Software architecture based on commercial TruckSim software

• Source code for models generated with commercial AutoSim software

• Available on the WEB:- http://arc.engin.umich.edu/arc/research/T1.html

http://arc.engin.umich.edu/arc/research/T1.html



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ArcSim User Interface: Top-LevelArcSim User Interface: Top-Level

Start Screen

Runs Screen:Simulation Setup

Animator

Inputs Vehicle Data Sets Simulation Codes(models)

X-Y Plotter

Post-Processing Programs



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ArcSim User Interface: Vehicle Data SetsArcSim User Interface: Vehicle Data SetsVehicle Data Sets

Tractor

Steering SystemSuspension Tire Data Sets

Trailer



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ArcSim User Interface: Tire Data SetsArcSim User Interface: Tire Data Sets

Tire Data Sets

Longitudinal Force (Fx) Data

Lateral Force(Fy) Data

Aligning Moment (Mz) Data



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Proper Tire ModelsProper Tire ModelsTire data sets generated from numerical experiments

using proper tire model



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PowerSim: FeaturesPowerSim: Features

• A flexible Powertrain and Vehicle Dynamics simulation

• Matlab-Simulink based simulation environment developed by the University of Wisconsin team:

- Hierarchical- Interactive- Choice of sub-models

- Easily reconfigurable

• High fidelity, transient diesel engine model developed and validated by the University of Michigan team

• Diesel engine simulation available on the WEB:- http://arc.engin.umich.edu/esim-docs/esim.html

http://arc.engin.umich.edu/esim-docs/esim.html



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ArcSim - PowerSim IntegrationArcSim - PowerSim IntegrationPowerSim

Vehicle Dynamics &DriveTrain Block

AnimatorX-Y Plotter

Post-Processing ProgramsC-Mex code for vehicle

dynamics models

ArcSim



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M916 Vehicle SpecificationsM916 Vehicle Specifications• 21 rigid body DOF / 91 state variables

• 126,000 lbf GVW

-M916A1 3-Axle Tractor (6x6)-M870A2 3-Axle Semitrailer

• Thermodynamic simulation with physically based sub-models

• DDC Series 60 engine

-475 HP@2100 rpm-Turbocharged, intercooled



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M916 Model CharacteristicsM916 Model Characteristics• 21 rigid body DOF / 91 state variables

- Tractor: 6 DOF- Trailer: 3 DOF (Rotational)

- Axles: 2 DOF (Roll and Jounce)- Wheels: 1 DOF (Spin)- 25 auxiliary states

• Computational load- 6600 multiplies/divides, 6000 add/subtracts per evaluation

of state derivatives

- Runs at about 3.5 sec computation time per sec of simulated motion on a 120 MHz Pentium

• Parameters obtained by measurement or estimation

• Modeling assumptions verified



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M916 Example ApplicationsM916 Example Applications

I. Proper handling models

II. Steering/braking for rollover

III. Truck acceleration on flat road

IV. Traction while hill climbing



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Example Application IExample Application IProper Handling Models

Runs Screen

Programs Based on Different Equaton Formulations

Programs Based on Different Complexity Models



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Element ImportanceElement Importance

HighHigh

LowLow

Idea: Use power-based metric to rank the importance of components and eliminate low-importance components



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Handling Performance PredictionsHandling Performance PredictionsFull Model vs. Reduced ModelFull Model vs. Reduced Model

0 1 2 3 4 5 6 7 8 9 10-0.2

-0.1

0

0.1

0.2

Time [sec]

0 1 2 3 4 5 6 7 8 9 10-5

0

5

Time [sec]

FullReduced: 30% of elements removed

Tractor Lateral Acceleration [g’s]

Tractor Yaw Rate [deg/s]



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Example Application IIExample Application IISteering/Braking for Rollover

Start Screen

Runs Screen:Simulation Setup

Animator

Inputs Vehicle Data Sets Simulation Codes(models)

X-Y Plotter

Post-Processing Programs



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UMTRI “Drastic” ManeuverUMTRI “Drastic” ManeuverBrake pressure is switched on and off when roll rate is zero

0 1 2 3 4 50

50

100

Time [sec]

0 1 2 3 4 5

0

10

20

Time [sec]

0 1 2 3 4 5-1012

Time [sec]

Steering wheel angle [deg]

Brake pressure [psi]

Trailer roll angle [deg]



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Worst-Case Steering/Braking Worst-Case Steering/Braking Conditions for Inducement RolloverConditions for Inducement Rollover

Idea: To use optimal control/zero sum game theory, to systematically identify worst case input conditions and compare to conventionally chosen “drastic” inputs

0 5

-100

-50

0

50

100

Time [sec]0 5

-5

0

5

10

15

20

25

Time [sec]0 5

0

10

20

30

40

50

60

70

80

90

Time [sec]

Steering wheel angle [deg] Brake pressure [psi] Trailer roll angle [deg]

worst-case

drastic



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Mobility StudiesMobility Studies

PowerSim

MULTI-CYLINDERDIESEL ENGINE

EXHAUSTMANIFOLD

INTAKEMANIFOLD

INTER-COOLER

COMPRESSOR TURBINE

WA

ST

EG

AT

E

FUELSYSTEM

Air

FuelExhaustgas

W.

Diesel EngineSystem

Driveline

Vehicle Dynamics

AA

AAAAAAAAAAAAAAAA

AAAA

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AAAAAAAA

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AAAAAA

AAAAAAAAA

T C

Trns

D-FR

D-R

IA-D Tr-C

D-F

Point Mass

126,000 lbf GVW



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Flexible Powertrain Simulation developed in SIMULINK by the University of Wisconsin team:

- Hierarchical- Interactive- Choice of Sub-models- Easily Reconfigurable

TC Diesel Engine System SimulationTC Diesel Engine System Simulation

IC

TC

Engine Inmnfld

Exmnfld

Cylinders

The in-cylinder model: UM - UW - WSU



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Advanced Propulsion System SimulationAdvanced Propulsion System Simulation

ENGINEVIBRATION

TURBOCHARGED DIESEL ENGINE SYSTEM

FUEL &COMBUSTION

ENGINEFRICTION

HEATTRANSFER

TRANSIENTCOLD START

IN-CYLINDERDIESELENGINEMODEL

EXTERNAL SUB-

SYSTEMS

INT

EG

RA

TIO

N W

ITH

TH

E V

EH

ICLE

SIM

ULA

TIO

N

DRIVE-TRAIN



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Experimental Set-Up for Model ValidationExperimental Set-Up for Model Validation

The Engine: DDC-60 Six-Cylinder, Turbocharged, Intercooled, Direct Injection Diesel Engine Geometry: B = 13 cm; S= 16 cm; L = 26.93 cm; CR = 15

Rated Power = 350 kW @ 2100 rpm

DYNA-MOMETER

6 cylinder turbochargeddiesel ENGINE

LOW SPEEDDATA ACQUISITION& CONTROL SYSTEM

HIGH SPEEDDATA ACQUISITION SYSTEM

PRESSURESTEMPERAT.VIBRATIONS

SPEEDTORQUEFLOWS

CYCLE &TIME RESOLVED EXHAUSTGASANALYSIS

• VXIbus Technology• MXI PC interface• VXIplug&play Instruments

• 120 channels, 16 bit A/D • 12 channels D/A • 48 channels D/D • 20 relay outputs

• VXIbus Technology• Embedded VXIpc - 486• VXIplug&play Instruments

• 32 channels, 16 bit simultaneous A/D

• 4 Mb mass storage device • 1 GB SCSI HD

DYNO CONTROL UNIT

Three-Component Force Transducer for Engine Vibrations Studies

Pressure Transducers / Heat Flux Probes in all Cylinders



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Calibration and Validation of Sub-ModelsCalibration and Validation of Sub-Models

Same set of calibrated constants used for all other

operating points

0

20

40

60

80

100

120

320 340 360 380 400 420

experimentsimulation

CYLIN

DER

PRESSURE

(bar)

CRANK ANGLE (deg)

1200 rpm50% load

0

50

100

150

320 340 360 380 400 420

experimentsimulation

CYLIN

DER

PRESSURE

(bar)

CRANK ANGLE (deg)

2100 rpm100% load

Model constants calibrated to produce best agreement

between measured and predicted pressure traces

CALIBRATEDPOINT

RATED SPEED,FULL LOAD



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Transient Engine Model ValidationTransient Engine Model Validation

A sequence of elementary transients defined in order to validate predictions of the multi-cylinder engine response against experimental

measurements under carefully-controlled test-cell conditions.

0

500

1000

1500

2000

2500

50

100

150

200

250

300

350

400

450

0 5 10 15 20 25 30

Engine

Speed

(rpm

);

External

Load

(N

m)

Intake

Manifold

Pressure

(KPa)

Time (s)

ENGINE SPEED - PREDICTED

ENGINE SPEED - MEASURED

EXTERNAL

LOAD

BOOST

PRESSURE



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Study the Effect of Turbocharger Inertia on Engine Response and Vehicle Acceleration

Example Application IIIExample Application IIITruck Acceleration on Flat Road

•Start at 10 mph•100% driver demand

126,000 lbf GVW



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Connection PointsConnection Pointsfor Model Integration Methodologyfor Model Integration Methodology

Engine Driveline VehicleDynamics

Wheel Angular Speeds

Engine Load Torque

Engine Angular Speed

Wheel Drive

Torques

RigidCrankshaft

FlexibleAxle Shafts

Torque Converter & Transmission

Wheel Hub Inertias & Tire Model

ωτ

Point Mass

PowerSim

126,000 lbf GVW



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Performance ComparisonPerformance Comparison

ITC LI = 0.5 ITC HI

1200

1300

1400

1500

1600

1700

1800

1900

0 2 4 6 8 10

ENGINE

SPEED

(rpm)

M916A1 SEMIGross Curb Weight 126,000 lbFirst Gear Low Inertia TC

High

Inertia TC

10

12

14

16

18

20

22

24

26

28

0 2 4 6 8 10

TRUCK

SPEED

(mph)

M916A1 SEMIGross Curb Weight 126,000 lbFirst Gear

Low Inertia TC

High Inertia TC

TIME (s)

TURBOLAG

TURBOLAG



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Idea: Show how thrust and terrain inclination dynamically affect wheel loads and thus traction

Example Application IVExample Application IVTraction While Hill Climbing

•10 mph•100% driver demand

126,000 lbf GVW

Wet Surfaceµ = 0.4

5 %Grade

FzAxle 4

FzAxle 5

FzAxle 6

FzAxle 3

FzAxle 2

FzAxle 1



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Connection Points for Model Connection Points for Model Integration MethodologyIntegration Methodology

Engine Driveline VehicleDynamics

Wheel Angular Speeds

Engine Load Torque

Engine Angular Speed

Wheel Drive

Torques

RigidCrankshaft

FlexibleAxle Shafts

Torque Converter & Transmission

Wheel Hub Inertias & Tire Model

ωτ

Point Mass

PowerSim

126,000 lbf GVW



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Vehicle Dynamic ModelsVehicle Dynamic Models

• 1-D point mass

• Constant vertical tire loads

• Tire Fx independent of Fz

• Constant road slope

• Simple rolling resistance model

• Simple aero drag model

• 21 Rigid Body DOF

• Full nonlinear kinematics

• Comprehensive tire model

• Hysteretic suspension springs

• Comprehensive steering model

• Simple braking model

• Constant road slope

• Simple rolling resistance model

• Simple aero drag model

• Bottom Line: The interaction of pitch and handling dynamics with the engine and Powertrain can be studied.

Point-mass model Multi-body model



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Hill Climbing: ResultsHill Climbing: Results

VEHICLE SPEED [mph]

VEHICLEACCELERATION [g's]

TIME [sec]

8

10

12

14

16

18

20

22

-0.1

-0.05

0

0.05

0.1

0.15

0 2 4 6 8 10

M916A1 SEMI, Gross Curb Weight 126,000 lb

ax

vx



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Hill Climbing: Results - cont.Hill Climbing: Results - cont.

WHEEL VERTICAL LOAD [lb*1000]

TIME [sec]

5

10

15

0 2 4 6 8 10

M916A1 SEMIGross Curb Weight 126,000 lb

FRONT

FRONT REAR

REAR



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Hill Climbing: Results - cont. Hill Climbing: Results - cont.

FRONT WHEELS SLIPPING

-1000

0

1000

2000

3000

4000

5000

0 2 4 6 8 10


FRONT

REAR

WHEEL LONGITUDINAL FORCE [lb]

1.2

1.4

1.6

1.8

2

2.2

2.4

2.6

2.8

0 2 4 6 8 10


FRONTREAR

TIME [sec]

WHEEL SPEED [rev/s]



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SummarySummary

• Demonstration 1st generation models and simulation tools of a complete vehicle:

- Powertrain- Vehicle Dynamics

• ArcSim and PowerSim:- User friendly and flexible Vehicle Dynamics and Powertrain

simulation and animation environments

• Demonstrated with the M916 truck:- Handling (multiple models)

- Rollover (limit maneuvers)- Mobility studies



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Future DirectionsFuture Directions

• Vehicle- Survivability: Battle field performance- Drivability: Handling and acceleration

- Mobility: Dynamic and wheel traction- Efficiency: Terrain roughness and fuel economy- Safety: Limiting maneuvers

• Model refinement and validation

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