Introduction To Modeling Dynamics: Automotive Applications · Introduction To Modeling Dynamics:...

Introduction To Modeling Dynamics: Automotive Applications

Joe DeRosePowertrain NVH R&DFord Motor Company

G. DeRose Jr. / GDEROSE4/7/2009

Not job 1 representative.Hardcopies are uncontrolled.



Overview

• Introduction To Rigid Body Dynamics Modeling

• Applications

• Advanced Applications

• CAE Challenges

• Summary



Introduction

• Education– Michigan State University

• B.S. Mechanical Engineering, 1993• B.S. Computer Science, 1993• M.S. Mechanical Engineering, 1996• Ph.D. Mechanical Engineering, 1998

– Large scale topology optimization



Introduction

• Work Experience– Ford Motor Company, 1999 to present

• Powertrain NVH Research and Development– Cross functional optimization

• Vehicle Dynamics– Development– CAE

• Durability and NVH CAE Development– Cross functional optimization– CAE method development

– Engineering consultant

– Adjunct faculty in ME at LTU



Rigid Body Dynamics Modeling

• Goal– Represent a physical system with an

analytical model– Analytical model consists of a collection of

rigid bodies and building blocks




• General concepts– Rigid bodies

• Mass, CG and inertia

– Constraints• Revolute, spherical, etc…

– Connectors• Springs and dampers




• Solution strategy– Step 1: Use Newton’s 2nd Law to develop a

system of 2nd order differential equations

wrurusuuu

busu

FzzkzzkzzbzmFzzkzzbzM

=−+−−−−=−+−+

)()()()()(

&&&&

&&&&

∑ = zMFz &&




• Solution strategy– Step 2: Convert the system of 2nd order

differential equations to a system of 1st order differential equations

BUAXX +=&

MatrixInput :Matrices Space State:,

Vector) State d/dt(:Vector State:

UBA

XX&




• Solution strategy– Step 3: Determine a numerical solution to the

system of 1st order differential equations

– Available tools• Matlab / Simulink / Maple / MathCAD• Classical Numerical Methods• ADAMS• veDYNA• LMS Virtual Lab / DADS




• Quarter-car model– Sinusoidal road input (0.1m @ 1.0 Hz)– Time response




• Quarter-car model– Frequency response




• Use analytical model to– Predict dynamic response– Investigate parameter sensitivity– Optimize

• Benefits– $$$: CAE modeling not prototypes– Design evaluations– Six sigma, robustness and reliability



Applications

• Chassis Design / Vehicle Dynamics



Applications – Vehicle Dynamics

• Goal– For a given vehicle modify the

rear suspension design to improve vehicle turn-in cornering response without degrading limit handling

• Decrease rear compliance understeer

• Increase roll understeer

• Constraints– Base design already

determined– Allowed to modify only a few

hard points and suspension bushing rates




• Design variables– Hardpoints

• LCA at body vertical• LCA at axle lateral

– Bushing Rates• LCA at body• LCA at axle




• Solution method– Design of Experiments (DOEs)

• Systematic/mathematical methods for the investigation of processes and systems

– Planning and conducing experiments– Analyzing results

– DOEs Goals• Design space exploration• Identify parameter sensitivities• Optimize design

– Often associated with Response Surface Methodology (RSM)

• Develop a surrogate model




• Design of experiments phases– Phase 0: Screening experiment

• Determine which parameters are important and unimportant• Often investigate large range of variables

– Phase 1: Initial response surface• Determine if the ranges of the design variables are

appropriate

– Phase 2: Optimization (with RSM)• Focus on tighter ranges of the design variables (operability

region) and optimize




• Example response surfaces




• ResultsRear Wheel Lateral Compliance Steer Angle (deg/kN)

Compliance Understeer




• ResultsRoll Motion Rear Wheel Steer Angle (deg/deg roll)

Roll Understeer




• Summary– Lower control arm to rear axle hardpoint most

significant factor in achieving the desired response

– Design of Experiments• Successfully implemented to identify relevant

parameters• Design variable sensitivities found requiring

minimal design time




• Vehicle dynamic response



Applications – Driveline/Axle Design

Dynamic response

andmodal

separation



Applications – Valve Train Design

• Engine valve train design– Inputs

• Cam lobe profile• Valve spring design

– Preload, surge frequency

– Outputs• Intake/exhaust behavior• Valve open and close

accelerations/forces– Goals

• Minimize weight• Maximize durability• Robust to manufacturing variation

and operating conditions



Advanced Applications

• Differential gear contact stresses and noise (flexible bodies)



Advanced Applications

• Vehicle dynamics with control systems



CAE Challenges

• Simulations versus real life…



Summary

• Go State!

• Rigid body dynamics and system response– Time domain and frequency important

• Rigid body dynamics applications– Vast, companies need help…

• Advanced applications– Growth area

• CAE challenges– Solutions needed, applicants apply

Introduction To Modeling Dynamics: Automotive Applications · Introduction To Modeling Dynamics:...

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