18_Tires

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2 copyright LMS International - 2005

Tire Force Element

Models a vehicle tire interacting with a road profile.

No bodies or constraints added by this element

Forces calculated in the tire/ground plane

Transformed to the global coordinate system when applied to the tire body

Three components of force are calculated:

normal

longitudinal

lateral


Tire Components

Steer Angle

Camber Angle

Aligning Coefficient

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Ride & Handling Definitions

Ride analysis

Vehicle analysis wherein the forces generated on vehicle components, and in

particular on the passenger, are of primary importance.

Handling analysis

Vehicle analysis wherein the overall performance of the vehicle (directional

response, lateral acceleration, etc.) is of primary importance.


Tire Models

4 different models available with the Standard Tire license

Simple Tire

Complex Tire

STI Tire

Magic Tire

6 Different versions of the TNO Tire, separately licensed

TNO MF-Tyre Express, Standard, Supreme

TNO MF-Swift Express, Standard, Supreme CD Tire, separately licensed

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Simple Tire

Road is fixed to global origin (no Road.Body)

Minimal number of parameters needed

Longitudinal forces calculated from simple curve only

Lateral forces calculated from cornering stiffness only

Longitudinal forces calculated by friction coef.

Constant vertical damping only


Complex Tire

Curve Damping

Entry should include the name of the curve that defines the tire normal damping

rate as a function of the chassis fore/aft speed.

Trans.Damp.Defl

When non-zero this value is used to attenuate the normal damping force for

small tire deflections. If a value of zero is entered the nominal damping rate is

used

Rolling.Radius

This value is found by dividing the distance traveled during one rotation by 2. Ifa value of zero is entered, the deflected radius found in the tire normal force

calculation will be used.

Carcass effects

2nd order effects due to the tire carcass can be included in the vertical, lateral,

and longitudinal directions

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STI Tire

Standard Tire Interface to bring in users tire code in standard format

Values to be defined within the STI formfill:

File .STI : File containing input information describing the STI tire

IDROAD : Road type identification number

File.ROAD: File containing information describing the STI road

ISWTCH : Set to 0 for static analysis, 1 for dynamic analysis

NOTE: Setting ISWTCH = -1 in the STI menu will cause DADS to automatically

set the ISWTCH flag to 0 or 1 depending on the type of analysis encountered

by DADS3D

WRKARR 1-10: These are real work array values


Magic Tire

Based on The Magic Formula Tyre Model by Hans Pacejka & Egbert Bakker, 1991

This version of the Pacejka formulation is very good for motorcycle tires

File.Magic

Curve-fitted test results consistent with the Magic Formula formulation

Describe the lateral force, aligning moment, and/or longitudinal force.

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Three Tire Types Simple & Complex

BASIC

Ignores the rotational inertia of the wheel

Tire body must be constrained to the chassis so no rotation occurs

Steer angle is defined directly as a user input

Camber is assumed to be zero

INTERMEDIATE

Ignores the rotational inertia of the wheel

Tire body must be constrained to the knuckle so no rotation occurs

Steer and camber angles calculated from the model

FULL - Recommended

Steer and camber angles calculated from the model

Accounts for the rotational inertia of the wheel


Tire Connection Information

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Tire Connection Information

Tire Body and Chassis Body must be defined

These can be the same for BASIC and INTERMEDIATE.

Axi s on Chass is Body

X-axis defines the vehicle direction of travel

Z-axis defines up for the vehicle

Axi s on Tir e Body

origin at the center of the tire circle

Z-axis along axis of rotation

Z-axis should point in same quadrant as Chassis Y-axis

Axi s on Road Body

Used to assign road to moving body

Vehicle on shaker platform

Vehicle on trailer

Used as option to position/orient road profile

Surface is defined as height (z) versus x (spline curve) or x

and y (spline surface)

If no Road.Body, the road profile is assumed to be defined

with respect to the global origin.


Normal Force Calculation Methods

Point contact

Valid if radius of curvature of road profile feature is much larger that tire radius

Normal ForceX

Z

Road Reference

Frame

1) Road height and tangent line to roadsurface based on x, y coordinates oftire center in road reference frame.

2) Perpendicular distance from wheelcenter to road tangent line definesdirection, point of application andtire deflection12

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Distributed contact

Tire divided into a user-defined number of vertical slices

Each area of intersection is found

Equivalent normal deflection, d, is found by equating the intersected area with

that for the tire on a flat surface

The point of application of the tire force, Cp, is found through a weighted

average of the centroids of the partial intersected areas



Distributed contact continued

The direction of the force is found through a weighted average of the terrain gradient

vectors, gi, associated with the partial intersected areas

Includes adjustments to account for sharp features

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Road Profile

4 Different Options

Define in ROAD element

Can be 2-D or 3-D

If the same profile or surface is sufficient for all tires

Define in the TIRE element

If different profiles or exist for some or all tires

Will override curve in ROAD element if both defined

In ROAD.F user-defined subroutine

User-defined analytic or tabular surfaces

Otherwise, the road is assumed flat in the global X-Y plane and located at Z=0


Longitudinal and lateral forces are computed and act in this plane

Normal Force act perpendicular to this plane

Z-axis of the terrain tangent plane coordinate system is normal to thetangent plane, directed upwards

X-axis is the intersection of the terrain tangent plane and the plane of

the tire disk

The Y-axis is in the terrain tangentplane, perpendicular to the X-axis

Terrain Tangent Plane

Plane tangent to the terrain profile at the point of contactPlane tangent to the terrain profile at the point of contact

between tire and terrainbetween tire and terrain

Resulting coordinate system of Terrain Tangent PlaneResulting coordinate system of Terrain Tangent Plane

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Normal Force Effects

Vertical.stiff

When tire normal force is a linear function of displacement.

Overridden when Curve.vertical is used.

Curve.vertical

When tire normal force is a non-linear function of displacement.

Damping.coeff

When normal force damping constant is independent of forward speed.

Overridden when Curve.damping is used.

Curve.damping

When normal force damping coefficient is a function of chassis forward speed, NOT

VERTICAL VELOCITY.


Normal Force Effects

Num.Divisions

Used with distributed contact normal force model

Number of vertical slices into which the tire is divided.

Zero for simple point-contact normal force model

Use distributed contact model when road profile contains abrupt changes.

Set high enough so that each slice is smaller than the smallest road profile feature.

Trans.Damp.Defl

When normal damping force is to be attenuated for small tire deflections. Avoids slap of damping force after lift-off

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Longitudinal Calculation Methods

Rolling resistance

For any type (Basic, Intermediate, or Full)

Parasitic longitudinal force due to carcass deformation losses, bearing friction, etc.

Approximated as constant fraction of the normal force

Crr = Coefficient of Rolling Resistance

Fn = normal force

Vclong = wheel center forward velocity

Applied directly at wheel center, not tire patch

)sign(VF-CFlongcnrrrr=


For Type BASIC or INTERM, the longitudinal force is computed from an explicit torque. If

a torque is specified (Curve.torque), the longitudinal force is simply:

T = Time based torque curve (Curve.torque)

Rd = Deflected radius


dlong

R

TF =

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For type FULL, the ratio of the longitudinal force to the normal force (the longitudinal force

coefficient) is normally a function of rotational slip, S:

Equation for Longitudinal Force

Choice of 5 approaches for long


)sign(VVV-S pc

p

long

=

sign(S)FF nlonglong =

Vp = Tire patch forward velocity

Vclong = Wheel center forwardvelocity



The 5 approaches for long to choose from are:

Set Soil type to SIMPLE, the following curve of long vs. S applies

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The 5 approaches for long continued Set Soil type to HARD, the following equation applies

Set Soil type to SOFT, the following equations apply

rr

SFbdk-

long Ce-1 n +

=

k = rubber hardness = 60psi

b = tire section width

d = tire section diameter

= Friction coefficient

( ) rr-7.5S-0.1Blong Ce-1e-1 n += = friction coefficientCI = Cone Index

b = tire section width

d = tire section diameterh = tire section carcass height

+

+

=

d

b31h

51

F

dbCIB

n

n



The 5 approaches for long continued

(S) User defined non-linear curve as function of longitudinal slip

(Vp) User defined non-linear curve as function of tire patch forward velocity

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Soil Types

Determines long Surface.type - SIMPLE

When operating on hard surfaces, where longitudinal friction coefficient is to be

based upon a simple function of rotational slip. Surface.type - HARD

When operating on hard surfaces, where longitudinal friction coefficient is based

upon rotational slip, rubber hardness, tire undeflected radius, and section width.

The equations governing hard surface tire forces are detailed in ASAE publication

No. 79-1046

Surface.type - SOIL

When operating on soft soils. The equations governing soil surface tire forces are

detailed in ASAE publication No. 87-1622.


Soil Parameters

Cone.index

Required when Surface.type HARD or SOIL is used. Otherwise unused. With

Surface.type SOIL, this variable represents the cone index; with Surface.type

HARD, it represents rubber hardness.

Section.height

Required when Surface.type SOIL is used. Otherwise unused.

Section.width Required when Surface.type HARD or SOIL is used. Otherwise unused.

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Alternatively, the longitudinal force may be generated by a longitudinal spring-

damper force

Rr is the rolling radius of the tire

plong is the longitudinal position of the tire center

plong0 represents the equilibrium position of the spring

plong0 is kept constant until such time as the longitudinal force generated by the

spring-damper is greater than that available through friction, at which time plong0slides until such time as the spring-damper force is less than the friction force

Note & Warnings

This method is only recommended for types of analysis where the vehicle is

stationary

If carcass effects are activated, this method is over ridden


plonglong0longrlonglong VC)pp(RKF ++=


Longitudinal Force Effects

Rolling.Radius

Defines constant radius for the tire force application point.

If zero, the rolling radius is calculated dynamically based upon the undeflected radius and

the tire deflection.

Insures that x = Rrolling *

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Longitudinal Force Effects

Long.Stiff

If carcass effects are not activated, used by longitudinal spring damper model in

previous slide

If carcass force model activated, used by the carcass force calculation

Long.Damp

Used when the Long.Stiff variable is used.


Function of the normal force and slip angle

Analogous to the longitudinal force with rotational slip

Slip angle is the angle between the tire center heading vector and the tire velocity vector

projection in the terrain tangent plane.

Lateral Force Calculation Methods

( )latccc1

VsignV

V

tanlong

lat

=

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Lateral force typically varies with both the normal force and slip angle.

Data can be entered through:

Table.Lateral variable (Used primarily in handling analysis.)

Where no carpet plot data exists, the relationship is approximated by a cubic

polynomial determined from the following boundary conditions:

C= cornering stiffness

Flat = maximum lateral side force coefficient

n = saturated steer angle generally approximated by:

( ) 00Flat = ( )

C0d

Flat = ( ) maxlat FF =n ( ) 0d

Flat =n

C

F2.5 nn=


A third type of lateral force: lateral spring-damper

Function of lateral translational displacement

Define horizontal line which intersects the center of the tire patch, and is

parallel to the forward velocity vector or Terrain Tangent plane X-axis.

Displacement & Velocity is the perpendicular distance from the tire patch to this

line

Reference line remains in the same place until the lateral force is greater thanthat available through friction, line slides until force is less than the friction

force. Used if Lateral.Stiff is not zero and carcass effects not activated

Note: This method is only recommended for types of analysis where the vehicle is

stationary


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Lateral Force Effects

Cornering.stiff

Used to approximate the lateral force carpet plot when Table.lateral is set to

NONE.

Expressed as (lateral force) divided by (sideslip angle).

Used primarily in handling analysis.

Roll.moment

If the roll moment generated by the tire normal force combined with the lateral

displacement of the tire patch is important, this flag should be set to TRUE.

Relax.length

When lateral force and aligning moment change abruptly, this parameter allows

a more realistic (attenuated) tracking of the actual lateral force and aligning

moment, due to carcass deformation


Lateral Force Effects

Lateral.stiff

If carcass effects are not activated, used by lateral spring damper model in previous

slide

If carcass force model activated, used by the carcass force calculation

Units are lateral force divided by distance.

Lateral.damp

Used When the Lateral.stiff is used to generate lateral force.

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Carcass Effects

State equations added to improve tire response compared to test data from a customer

VD=&

carcass

patch

m

CVKDF )(V

+=&

D is the displacement of the tire patch in the direction of interest

V is the velocity of the tire patch in the direction of interest

Fpatch is the force applied to the tire patch by the road surface in the

direction of interest

K is the tire carcass stiffness in the direction of interestC is the tire carcass damping constant in the direction of interest

Mcarcass is the mass fo the deflected portion of the tire carcass


Carcass Effect Starting values

Carcass mass of about 5% of the total tire+wheel mass.

For the vertical carcass effect, it just use the vertical stiffness value

For the longitudinal & lateral stiffness, start with a value equal to the vertical stiffness.

Transient data from a pulse steer or something like that, can give a starting point for trying

to tune the lateral stiffness.

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Other Tire Parameters

Steer.angle

Used with BASIC tires when steer angle of tire is constant.

Curve.Steer Used with BASIC tires when the steer angle of the tire is known as a function of

time.

Align.Coeff

Represents the fore-aft displacement of the tire patch

Use if the yaw moment from the tire lateral force combined with the fore-aft

displacement of the tire patch is important

Curve.Utility

Used to access curve data inside user-modified tire routine.


Modeling tips for tires

If there is unusual behavior at start of analysis, check:

Vertical stiffness

Set gravity to 0.0 (scale.gravity.coeff in System.data element) if tires are above

ground initially. Vehicle should stay at rest above ground

Only use the longitudinal & lateral spring damper models for stationary analysis

Use of basic and intermediate types not recommended

Table.Lateral most accurate for lateral force if data exists

Typical Values on next slide is minimum amount of data to generate vertical, longitudinal& lateral forces

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Typical Values

Dry Pavement: 0.8-1.0

Wet Pavement: 0.5-0.8

Friction Coefficient

0.005-0.04Rolling Resistance

Car: 80-200 lb/deg

Truck: 200-800 lb/deg

Car: 350-900 N/deg

Truck: 900-3500 N/deg

Cornering Stiffness

Car: 6-20 lb*s/in

Truck: 10-85 lb*s/in

(10% critical damping)

Car: 1000-3500 N*s/m

Truck: 1700-15000 N*s/m

(10% critical damping)

Vertical Damping

Car: 850-1700 lb/in

Truck: 850-6000 lb/in

Car: 150K-300K N/m

Truck: 150K-1000K N/m

Vertical Stiffness

Typical Values (English)Typical Values (SI)Variable

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Lab Session: Complex Tire and RoadPage 1

Virtual.Lab Motion Advanced Training

Lab Session: Complex Tire and Road

IntroductionThis tutorial illustrates the overall procedures in defining the Complex Tire andRoad elements. It also reviews the procedures of creating a spline curve andbushing element. This tutorial is intended to increase you familiarity with addingtires and road elements to models.

Getting StartedTo open the model,

1. Open Complex_Tire.CATAnalysis.

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Create the User Parameters

Environment Settings

There are specific settings that must be activated within the environment window

to allow for the visualization of the defined parameters within the SpecificationTree.

From the Main Menu, select ToolsOptions.

1. Since all of our parameters will be defined within the Analysis document,Select the Motionbranch of the Options Tree and activate the selectionsShow parametersand Show relations.

2. Click OKto close the Options dialog box.

Defining Parameters

1. Click the Formula button from the bottom toolbar.

2. Within the Formulas dialog, Click on the Importbutton.

3. From the File Selection dialog, select the file parameters.xls from thecomplex_tire directory. Click Open to close the dialog.

4. An Import Result dialog box will open showing all the parameters that werepreviously defined in the Excel worksheet, Click the OKbutton.

5. Click OKto close the Formulas dialog box. A new Parameters branch shouldnow appear in the Specification Tree below the Analysis Model branch of theSpecification Tree.

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Insert a Road Element (Flat Road)

1. Click the black down arrow next to the Vehicle button on the MechanismDesign Workbench. This will display the Vehicle Suspension toolbar.

2. Click the Road button from the Vehicle Suspension toolbar. This willbring up the Road dialog.

3. Change the Namefield entry to read Fl at Road.

4. Left and then Right-click in the Curve Namefield entry and select Newfromthe resulting menu. This will bring up a second Function dialog.

5. Change the Namefield entry to Fl at Road Funct i on.

6. Select SPLI NE. CURVEfrom the Function Typedrop-down menu.

7. Left and then Right-click in the Curvefield entry and select Newfrom thecontextual menu. This will bring up a third Spline Curve dialog.

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8. Change the NameField Entry to Fl at Road Cur ve.

9. In the Curve Datasection of the dialog, click theAddbutton to add a defaultvalue of (0,0) to the X Length and Z Length lists.

10. In the field below the X Length list, enter 1.

11. Click theAddbutton again to add a value of (1,0).

12. Set the InterpolationField Entry to LI NEAR.

13. Click OKto close the Spline Curve dialog.

14. Click OKto close the LengthLength Function dialog.

15. Click OKto close the Road dialog box.

Insert a Bushing ElementA bushing element is inserted to the interface between the carrier and the shock

bodies to reduce swing and vibration.

1. Click the Bushingbutton from the Forces toolbar.

2. The Bushing Force element requires that two axes be selected. In theSpecification Tree under Product1_Rootshock (shock.1)shockAxisSystems, select the Bushing Carrier_Shock Axis branch, this will populatethe Body 1Field Entry.

3. In the Specification Tree under Product1_Root carrier (carrier.1)carrierAxis Systems, select theAbsolute Axis Systembranch as the Body 2Field Entry.

4. Right-click the Spring Conical X field and choose Edit formula from thecontextual menu.

5. In the blank field, enter the value (RSTI FF * 5. 7295779513082e+001) *1Nxm_rad. (You may click RSTIFF from the Parameter branch of theSpecification Tree instead of typing RSTIFF.)

6. Click OKto close the Formula Editor dialog.

7. Repeat steps 5-7 for Spring Conical Y and Spring Torsional.

8. Right-click in the Damping Conical Xfield and select Edit formulafrom thecontextual menu.

9. Enter the value ( RDAMP *5. 7295779513082e+001) * 1m2kg_s_r ad

10. Repeat step 9-11 for Damping Conical Y and Damping Torsional fields

11. Click OKin the Standard Bushing dialog box.

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Insert a Tire Element

1. Click the black down arrow next to the Bushingbutton to display theForces toolbar.

2. Click the Complex Tirebutton .

3. Under the Product1_ROOT tire (tire.1)tireAxis System branch of theSpecification Tree, select theAbsolute Axis Systemas the Tire BodyFieldEntry.

4. Under the Product1_ROOT carrier (carrier.1)carrierAxis Systembranch of the Specification Tree, select theAbsolute Axis Systemas theChassis Bodyfield entry.

5. Right-click in the Radius field and choose Edit formula from the contextualmenu.

6. Under the Analysis Model branch of the Specification Tree, selectParametersRADIUSfrom the Specification Tree. Click OK to close theFormula dialog.

7. Follow the same basic steps (6 & 7) for the Vertical Stiffnessand Dampingfields using the VSTIFF and VDAMP parameters respectively.

8. At the bottom of the Parameters section of the Complex Tire dialog, togglethe Typeradio button to Full.

The dialog should look similar to the following picture.

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9. Click the OKbutton to save the values and close the dialog.

Solve the Model1. Double-Click the Solution Setbranch from the Specification Tree, and

change the solution EndingTimeto 5s. Select OKto close the dialog.

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2. Click the Compute Solution button .

3. Once the Solution has completed successfully, click the Close Windowbutton in the Computing dialog box.

Animate the Model1. Select Solution Set from the Specification Tree.

2. Click theAnimatebutton from the Mechanism Design Workbench. This willbring up the Animation Toolbar.

3. Click the Play Forwardbutton from this toolbar to display the animation.

Selecting a new Road Profile

1. Within the model Specification Tree under Product1_Root, Right-Click on theroad (road.1) branch and Select Hide/Show from the resulting menu.

2. Within the model Specification Tree under Product1_Root, Right-Click on theroad.1 (road.2) branch and Select Hide/Show from the resulting menu. Asurface profile with two bumps should now appear.

3. Double-Click the Analysis Model branch of the Specification Tree to activatethe Mechanism Design workbench. Double-Click the PostProcessingSuspension Road.1 branch to open the Road definition dialog. Left andthen Right-Click in the Elements/CurveField Entry. Select Newfrom theresulting Menu. Change the name of the new function to Bumpy Road

Function.

4. Left and then Right-Click in the CurveField Entry. Select Newfrom the

resulting menu. Change the NameField Entry to Bumpy Road Cur ve.Toggle the Reference External Data option, and select the file road.txt fromthe project folder. Click OKto close the Spline Curve dialog. Click OKtoclose the Function dialog. Click OKto close the Road definition dialog.

Solve the Model

1. Select the Solution Setbranch from the Specification Tree.

2. Click the Compute Solution button .

Once the Solution has completed successfully, click the Close Windowbutton inthe Computing dialog box.

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Animate the Model1. Select Solution Set from the Specification Tree.

2. Click theAnimatebutton from the Mechanism Design Workbench. This willbring up the Animation Toolbar.

Click the Play Forwardbutton from this toolbar to display the animation.

ConclusionCongratulations, this completes the Virtual.Lab Motion Complex Tire and RoadLab.

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Lab Session: Post-Processing TrainingPage 1


Tire with Spline Surface & Post-Processing

Objective

The objective of this Lab is to create tire force elements that reference a splinesurface element (carpet plot) and learning about the post-processing capabilitiesin Virtual.Lab.

Lab Agenda

1. Create the fourth tire element and spline surface element.

2. Associate the pre-existing three tire force elements with the spline surface

element.3. Solving and post-processing the model.

4. Using post-processing tools in Virtual.Lab on the results obtained duringstep 3.

Create fourth tire element and splinesurface element

SelectFile

Open

car.CATAnalysisfile from the Virtual.Lab Main Menubar. This file should be found in the Postprocessing_Lab folder. Under theAnalysis ModelForces branch of the model Specification tree, three tireelements called tireone, tiretwo and tirethree have already been defined. Thegoal in this part of the lab is to create a spline surface element that is referencedby all the tires and create a fourth tire element.

Creating fourth tire element

1. Click the black arrow to the right of the Bushing Button , this will displaythe Forces Toolbar. To create the fourth tire element click on the Complex

Tirebutton in the Forces toolbar. This will bring up the following window.

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2. For the Tire BodyField Entry, Select the Product1_ROOT tire4 (tire4.1)tire4 Axis System tiret4 branch of the model Specification Tree. For theChassis BodySelect the Product1_ROOT chassis (chassis.1) chassis

Axis Systems chasscenter branch of the model Specification Tree. Forthe Road BodyField Product1_ROOT ground (ground.1) ground AxisSystems ground_default_ref branch of the model Specification Tree.

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3. For the RoadField Entry under the Elements section of the dialog, Left andthen Right-Click in the Field Entry and select New. This will bring up thefollowing window.

Change the Function Typeto SPLI NE. SURFACEand under the Elementssection right click in the Surface Field Entry and select new to create Spl i neSur f ace. 1element

1. For the X, Y and Z MagnitudeField Entries pick Di mensi onl essfrom thedrop-down list.

2. Toggle the Reference external data file radio button. Now click the Browse

button and pick the pi t _cr v3. t xt file.

3. Change the InterpolationField Entry to LI NEARby picking it from the drop-down list. Now click the OKbutton to create the spline surface element calledSpl i ne Sur f ace. 1.

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4. For all the other required parameters please fill the Field Entries from thefollowing image of a completed Complex Tire dialog window.

4. Notice that a formula has been applied to the Cornering Stiffness Field Entry.To apply this formula, Left and then Right-Click in the Field Entry box. SelectEdit Formula from the resulting menu. This will bring up the Formula Editorwindow.

5. Within the Formula Editor, the following formula will be entered:

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( cor ner * 5. 7296e001) *1mxkg_s2_r ad

Mathematical operators, such as parentheses and multiplication symbols can beentered by select the symbol from the Operators list. To activate this list, selectOperatorsfrom the first column of the dialog labeled Dictionary.

To find the parameter cor ner , Select Parametersfrom the Dictionarycolumn,Realfrom the Member of Parameterscolumn, and scroll to the bottom of theMembers of Allcolumn to find the listing of parameters. Double-Click the

cor ner parameter to enter it into the formula.

Click OKin the Formula Editor once the formula is complete, this will return theresulting value back to the tire dialog.

6. Click OK in the tire dialog once complete.

Associate the pre-existing three tireforce elements with the spline surfaceelements1. To associate the pre-existing tireone tire-force element to the spline surface

element, Double-Click on the Forces tireonebranch of the SpecificationTree.

2. Left-click in the RoadField Entry in each dialog and select LengthLengthFunction.1 from the modeling tree.

3. Repeat steps 1-4 for elements tiretwo and tirethree.

Solving model to get results for post-processing

Select and highlight the Solution Set under the car_AnalysisCase branch of theSpecification Tree.

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Now click the Compute Solution button to solve the model.

Using post-processing tools in

Virtual.LabPost-processing tools in Virtual.Lab can be divided into two groups Plotting and

Animation tools.

Plotting tools

Plotting sample results from the LMSMotionResults file

1. From the Mechanism Design Workbench, Click the Open Motion Graph

Window button . This will bring up the plot creation window.

2. The simulation time is automatically plotted on the X-axis. Under the Y-axisselection at the top of the Define Plots section of the Motion Graph Windowselect Revolute under Type next to Element.

3. Under the Y-axis select the rev:fz1, rev:fx1,and rev:fy1.

4. To finish the definition of a plot, make sure both the X and Y-axis selections

are highlighted and then click the CreatePlotsbutton . A new branchshould appear on the right side of the screen below the car_AnalysisCase

branch of the tree.

Creating a Motion Display to display the plot

1. To open the graphing window, Click the New Display button . This willbring up the New Function Display wizard. Accept the setting of MotionDisplay by clicking the Next button. Accept the XY Plot setting by clicking theFinish button in the wizard window.

2. To place the previously defined plot in the Motion Display window, Right-Clickand then pick the Select Dataoption. Within the Default Data Selection

window highlight the ***car_AnalysisCase*** SYSTEM:Time_rev1:fz1option and then click the Display button in the Default Data Selection dialog.

3. Now you can change the title of the plot and the axes titles as required.Double-click on the title of the X-axis, this will bring up the following window.

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Click the Title tab as shown above and select the Custom radio button. Now acustom title can be defined, for example, Si mul at i on Ti me ( sec) . In asimilar manner, the title of the Y-axis can be changed to Z- di rect i onReact i on For ce f or Rev1 .

4. To change the title of the graph, double-click on the graph title, Graph1 () inthis case, in the top-left corner of the white plotting space. This will bring upthe Edit Graph window as shown below.

5. Click on the Titletab and modify the title as desired, in this case input Post -process i ng Trai ni ng Pl ot . Picking one of the options in the Positiondrop-down list can modify the position of the title, for instanceTop- Cent er .

6. The plots for fx1 and fy1 vs. Simulation Time (sec) can be modified in asimilar manner.

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Using the Graphing Tools to create Computed Plots

The Graphing Tools toolbar is shown at the top of the Motion Graph Window.This toolbar contains read and write operations, arithmetic operations, calculus

operations, scaling, smoothing and create FFT operations. This section will dealwith performing some of these operations on the plots.

1. To add two plots, clicking on the Add Curves button will bring up thefollowing window

2. Clicking on a plot under the car_AnalysisCase branch of tree shown on theright of the screen selects a curve to be added. In this case pick the

SYSTEM: Ti me__r ev1: f x1and SYSTEM: Ti me__r ev1: f y1plots.

3. Once the plots are selected, Click the OKbutton. This will create a branchlabeled AddCurves. 1 under the GraphComputed Plots branch.

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4. To open the Motion Display, Double-click the Function DisplaysMotionDisplay - XY-Plot branch.

5. Right-click in the white plotting space and the following menu will be

displayed.

Click on the Select Databutton and the Default Data Selection window will belaunched.

6. From the Default Data Selection window select the computed plotAddCurves. 1and then Click the Display button from the Default DataSelection dialog.

7. Close the Motion Display window when all plotting procedures have beencompleted.

Animation Tools

Selecting the car_AnalysisCaseSolution Set branch of the Specification Treefollowed by the Animate button from the Mechanism Design workbench, providesa basic animation of the mechanism model. The Animation Tools toolbar has

more advanced tools like camera follow, interference, animation trace, scaledmotion, point trace and animation vectors.

Camera Follow Animation

This animation tool allows the user to attach a camera to a body in the model andthen view the animation from the point of view of that body.

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1. Right-click the Analysis Model Animation Scenes branch of theSpecification Tree. Select New Animation Scene from the resulting menu, thiswill create an animation scene in the Specification Tree labeled Scene.1 asshown below.

2. Click and highlight the Scene. 1branch in the specification tree and click the

Camera Follow button of the Animation Tools toolbar, this will bring upthe following window.

3. For the Look FromField Entry select the axis system called Axi s . Syst em. 1under the Links Manager Link.1chassis_csys(chassis_csys.1) chassispart document branch of the Specification Tree.

4. For the Look ToField Entry select the axis system called chassi s_cgunderthe chassis part branch. Change the View AngleField Entry to 25and Clickthe OKbutton in the Camera dialog.

5. To activate the Camera Follow animation scene, using the Control key, selectthe car_AnalysisCaseSolution Set branch and the Animation Scenes Scene.1 Camera.1 branch of the Specification Tree.

6. Click theAnimate button in the Motion Animation toolbar. This willanimate the model with the Cameras point of view.

Multi-case Animation

Multi-case animation allows for two different results to be animatedsimultaneously for a given model. This means the same model may be solved

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two different times with different parameters and the resulting motion can beanimated together.

1. Select Insert from the Virtual.Lab Motion Main Menu Bar and Select the NewAnalysis Case option. This will create an analysis case with the nameAnalysisCase.1 in the Specification Tree.

2. Now click the One Body Initial Condition button in the Initial Conditionstoolbar. This will bring up the following window.

3. For the Attachments point selection pick the origin of the chassi s_cgAxissystem under the chassis part. Enter 20m_sin the Time DerivativeFieldEntry and Click the OKbutton.

4. Now double-click on each of the LengthLengthFunction elements associatedwith the tire force elements. This will bring up a window similar to thefollowing window.

In each case change the Function Type to SPLI NE. CURVE. Now click in theCurve Field Entry and pick the hi l l s_cr vspline curve element from thespecification tree.

5. Select the AnalysisCase that you just insertedSolution Set branch of the

Specification Tree and Click the Compute Solution button.

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6. For multi-case animation, press and hold down the Control key and select thecar_AnalysisCase Solution Set and AnalysisCase.1Solution Set

branches. Now Click theAnimate button and watch the animation ofboth cases simulataneously.

Documents

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