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Vehicle Dynamics CAE within a Development Programme N.W.Fussey, P.A. Chappell, J.A. Nicholson, N. McGowan

Development Programme Vehicle Dynamics CAE … Dynamics CAE within a Development Programme ... CAE fit in? CAE Analysis Objective Testing ... Vehicle Dynamics Tests e.g. Constant Radius,

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Page 1: Development Programme Vehicle Dynamics CAE … Dynamics CAE within a Development Programme ... CAE fit in? CAE Analysis Objective Testing ... Vehicle Dynamics Tests e.g. Constant Radius,

Vehicle Dynamics CAE within aDevelopment Programme

N.W.Fussey, P.A. Chappell, J.A. Nicholson, N. McGowan

Page 2: Development Programme Vehicle Dynamics CAE … Dynamics CAE within a Development Programme ... CAE fit in? CAE Analysis Objective Testing ... Vehicle Dynamics Tests e.g. Constant Radius,

Agenda• Introduction• Where does CAE fit in?• Applications of Vehicle Dynamics CAE• CAE Tools• Data requirements• Converting Subjective to Objective data• Simulations• Correlation• Conclusions

Page 3: Development Programme Vehicle Dynamics CAE … Dynamics CAE within a Development Programme ... CAE fit in? CAE Analysis Objective Testing ... Vehicle Dynamics Tests e.g. Constant Radius,

Where does CAE fit in?

CAE Analysis

ObjectiveTesting

SubjectiveTest/Tuning

Assists target setting& cascade

System and subsystemselection

Match vehicle to targets

Provide initial setup before final tuning

Vehicle Dynamics Testse.g. Constant Radius,Lanechange etc.

Kinematics & Compliance Test

Initial identification of competitors and targetsfinal component level tuninge.g. Spring/Damper rates, anti-roll bar sizes, bush rates.

Page 4: Development Programme Vehicle Dynamics CAE … Dynamics CAE within a Development Programme ... CAE fit in? CAE Analysis Objective Testing ... Vehicle Dynamics Tests e.g. Constant Radius,

Main Applications of CAE duringDevelopment

• Target assessment with programmeassumptions.

• Cascade targets to system/componentlevel.

• Provide system design direction.• Resolve conflicts & balance targets.• Assist tuning phase.

Page 5: Development Programme Vehicle Dynamics CAE … Dynamics CAE within a Development Programme ... CAE fit in? CAE Analysis Objective Testing ... Vehicle Dynamics Tests e.g. Constant Radius,

Vehicle Dynamics CAE

• Steering

• Handling

• Low Frequency Ride

Page 6: Development Programme Vehicle Dynamics CAE … Dynamics CAE within a Development Programme ... CAE fit in? CAE Analysis Objective Testing ... Vehicle Dynamics Tests e.g. Constant Radius,

Workload distributionduring development

CAEObj. Testing

Subj. Develop.0

20

40

60

80

100

Perc

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f max

. ap

plic

atio

n [%

]

Time

Page 7: Development Programme Vehicle Dynamics CAE … Dynamics CAE within a Development Programme ... CAE fit in? CAE Analysis Objective Testing ... Vehicle Dynamics Tests e.g. Constant Radius,

CAE Tools in Vehicle Dynamics

• Excel• Matlab/Simulink models

• ADAMS Full vehicle models & DoE.

Sanity & high levelparameter checks,ADAMS model set up,target cascade.

Note: Excel and Matlab models may be used before a Suspension and steering system has been selected.

Page 8: Development Programme Vehicle Dynamics CAE … Dynamics CAE within a Development Programme ... CAE fit in? CAE Analysis Objective Testing ... Vehicle Dynamics Tests e.g. Constant Radius,

ADAMS Model Detail & DataRequirements

Suspension Links

Bushings(linear/non-linear)

Beam ElementAnti-Roll Bars Aerodynamic Forces

Power Steering System(Hydraulic Forces)

Tyres - Pacejka/fitted data

Joint Friction

Springs,Dampers andSpring Aids(non-linear)

Page 9: Development Programme Vehicle Dynamics CAE … Dynamics CAE within a Development Programme ... CAE fit in? CAE Analysis Objective Testing ... Vehicle Dynamics Tests e.g. Constant Radius,

Converting subjective assessments toobjective data

Objective targets are essential if CAE is to be usedeffectively for vehicle dynamics development.

Example: Straight ahead controllability – how does the vehicle respond to small steering inputs at different speeds?

Page 10: Development Programme Vehicle Dynamics CAE … Dynamics CAE within a Development Programme ... CAE fit in? CAE Analysis Objective Testing ... Vehicle Dynamics Tests e.g. Constant Radius,

Converting subjective assessments toobjective data

Drive EventOwn products +

competitors

Subjectiverating (1-10VER scale)

Subjective rating –too fast/slow, just

right.

Steering Sensitivity g/100degSWA (Swept Steer)

11.21.41.61.8

22.22.42.62.8

80 90 100 110 120 130 140 150

mph

g/10

0deg

SWA

Target CharacteristicObjective test –On-centre,

swept steer vs.speed

Page 11: Development Programme Vehicle Dynamics CAE … Dynamics CAE within a Development Programme ... CAE fit in? CAE Analysis Objective Testing ... Vehicle Dynamics Tests e.g. Constant Radius,

Converting subjectiveassessments to objective data

Steering Sensitivity= f(speed, wheelbase, understeer,steering ratio)

Understeer = f(suspension/steering characteristics,weight distribution, tyres, aero etc……)

Usually programme assumptions

Page 12: Development Programme Vehicle Dynamics CAE … Dynamics CAE within a Development Programme ... CAE fit in? CAE Analysis Objective Testing ... Vehicle Dynamics Tests e.g. Constant Radius,

Target Cascade ExampleVe

hicl

eLe

vel

Syst

emLe

vel

Subs

ys.

Leve

lC

omp.

Leve

l

Understeer Gradient

Suspension Characteristics

e.g.. Bump/Roll Steer, Lateral Compliance Steer,Cornering Compliance etc.(Front/Rear Balance)

Geometry Hardpoints

Component Specifications

e.g. Tyre Cornering Stiffness, Bush Rates

Exce

l/Mat

lab

Mod

els

AD

AM

S Fu

ll Ve

hicl

eM

odel

s

Page 13: Development Programme Vehicle Dynamics CAE … Dynamics CAE within a Development Programme ... CAE fit in? CAE Analysis Objective Testing ... Vehicle Dynamics Tests e.g. Constant Radius,

Up Front Concept SelectionVehicle level

targets

Excel & MatlabModels

ADAMS PreSuspension

Concept Models eg. SLA,McPherson etc.

DoE Studies(ADAMS/Insight)

Page 14: Development Programme Vehicle Dynamics CAE … Dynamics CAE within a Development Programme ... CAE fit in? CAE Analysis Objective Testing ... Vehicle Dynamics Tests e.g. Constant Radius,

Balancing TargetsBuild ADAMS full

vehicle model basedon programmeassumptions

Run full set of simulations to verify targets can be achieved

Use multiple DoE using the samefactors and ‘linked’ responsesurfaces.

Page 15: Development Programme Vehicle Dynamics CAE … Dynamics CAE within a Development Programme ... CAE fit in? CAE Analysis Objective Testing ... Vehicle Dynamics Tests e.g. Constant Radius,

Full Vehicle Events (1)(steering & handling)

• Acc.controlled stop• ADAMS/Driver• Brake Drift• Brake in turn• Constant radius• Cross wind• Double lane change

• Dynamic constantrad.

• Fishhook• Frequency response• Hands free (flick test)• J-Turn• Lane change• Moderate braking

Page 16: Development Programme Vehicle Dynamics CAE … Dynamics CAE within a Development Programme ... CAE fit in? CAE Analysis Objective Testing ... Vehicle Dynamics Tests e.g. Constant Radius,

• On-centre• Open loop braking• Parking Effort• Sine steer• SDI• Steady state drift• Step steer• Straight line

acc/decel

• Straight line drive• Swept Steer• SVC• Throttle on/off in a

turn• Tyre wear• K&C (MTS Rig)• K&C (ABD Rig)

Full Vehicle Events (2)(steering & handling)

Page 17: Development Programme Vehicle Dynamics CAE … Dynamics CAE within a Development Programme ... CAE fit in? CAE Analysis Objective Testing ... Vehicle Dynamics Tests e.g. Constant Radius,

Low Frequency Ride (<20Hz)

<5 Hz Time domain 3D road modelling.

5 to 20 Hz – ADAMS/Linear (eigenvectorand state space matrix extraction).Converting to ADAMS/Vibration

>15 Hz – NVH Packages.

Page 18: Development Programme Vehicle Dynamics CAE … Dynamics CAE within a Development Programme ... CAE fit in? CAE Analysis Objective Testing ... Vehicle Dynamics Tests e.g. Constant Radius,

Low Frequency Ride (5-20Hz)ADAMS/Linear

Eigenvector/value

analysis

ABCDMatrices Matlab Routines

ADAMS Prevehicle dynamics

model + plantinput/outputs

0 5 10 15 20 25

Freq (Hz)

FRFs

Page 19: Development Programme Vehicle Dynamics CAE … Dynamics CAE within a Development Programme ... CAE fit in? CAE Analysis Objective Testing ... Vehicle Dynamics Tests e.g. Constant Radius,

Chassis Control SystemsADAMS Pre vehicle

dynamics model + plantinput/outputs

ADAMS/Control

Simulink Controller for ABS,

Yaw control,Switchable

dampers etc.

Must have a controller algorithm from the system supplier.Co-simulation

Page 20: Development Programme Vehicle Dynamics CAE … Dynamics CAE within a Development Programme ... CAE fit in? CAE Analysis Objective Testing ... Vehicle Dynamics Tests e.g. Constant Radius,

Correlation Methods

Kinematics & Compliance Rig Objective Vehicle Dynamics Testing

Plus Mass/Inertia, Tyre & Component Tests

Page 21: Development Programme Vehicle Dynamics CAE … Dynamics CAE within a Development Programme ... CAE fit in? CAE Analysis Objective Testing ... Vehicle Dynamics Tests e.g. Constant Radius,

Correlation StepsRate Springs,

dampers, ARB, bushes,

tyres etc.

Build vehicle to known spec.

Measure vehiclemass & inertia.

K&CTest

Dynamic tests on same vehicle as K&C.

Compare to ADAMS K&C sim.

Adjust compliances if necessary

Compare to ADAMS model

with driver inputs(SDI)

Page 22: Development Programme Vehicle Dynamics CAE … Dynamics CAE within a Development Programme ... CAE fit in? CAE Analysis Objective Testing ... Vehicle Dynamics Tests e.g. Constant Radius,

Correlation30m Constant Radius

Page 23: Development Programme Vehicle Dynamics CAE … Dynamics CAE within a Development Programme ... CAE fit in? CAE Analysis Objective Testing ... Vehicle Dynamics Tests e.g. Constant Radius,

Correlation75 mph[121km/h] low g swept steer

Page 24: Development Programme Vehicle Dynamics CAE … Dynamics CAE within a Development Programme ... CAE fit in? CAE Analysis Objective Testing ... Vehicle Dynamics Tests e.g. Constant Radius,

Correlation0.5g 62mph [100km/h] lane change

Page 25: Development Programme Vehicle Dynamics CAE … Dynamics CAE within a Development Programme ... CAE fit in? CAE Analysis Objective Testing ... Vehicle Dynamics Tests e.g. Constant Radius,

Correlation Issues

1. Steering wheel torque.Lack of hysteresis – Hydraulic, frictionand distribution though PAS system.Tyres.

• Frequency Response (higherfrequency)Roll and yaw gains underdamped –tyres mainly.

Page 26: Development Programme Vehicle Dynamics CAE … Dynamics CAE within a Development Programme ... CAE fit in? CAE Analysis Objective Testing ... Vehicle Dynamics Tests e.g. Constant Radius,

Correlation Issues

• Low frequency time domain analysis –suspension friction (balljoints, dampers etc.)and frequency dependant bushings.

• The models are only as good as the datasupplied.

Page 27: Development Programme Vehicle Dynamics CAE … Dynamics CAE within a Development Programme ... CAE fit in? CAE Analysis Objective Testing ... Vehicle Dynamics Tests e.g. Constant Radius,

Conclusions

• Vehicle dynamics CAE is applied inmany areas of the programme.Target setting & verification.Target cascade.System & component choice includingcontrol systems.System design.

Page 28: Development Programme Vehicle Dynamics CAE … Dynamics CAE within a Development Programme ... CAE fit in? CAE Analysis Objective Testing ... Vehicle Dynamics Tests e.g. Constant Radius,

Conclusions (Continued)• Close links to objective and rig testing

are vital for accuracy.• Close working relationship with

subjective development areas tomaximise CAE use.

• It is necessary to understand themodels’ limitations.