AutoMFTire

Introduction

The (Magic Formula) MF-Tire models the longitudinal dynamics of a vehicle, keeping the axle, wheel and tire in contact with a road represented by the Magic Formula and optional deformation compliance. Tire models apply forces and moments on wheel body so as to simulate a real tire forces and moments that tires apply on the vehicle.

The tire models MF-Tire and MF-Swift (Short Wavelength Intermediate Frequency Tire) can be used in vehicle dynamics simulations in all popular simulation packages to efficiently, and accurately, represent tire behavior for applications ranging from steady-state to complex high frequency dynamics.

Altair MotionView and MotionSolve support multiple tire models through the TNO defined interface.

With MF-Tire, you can simulate steady-state and transient behavior, making it a suitable tire model for:

•	Vehicle handling

•	Control prototyping

•	Rollover analysis

With MF-Swift, you can simulate tire dynamic behavior up to about 100 Hz, which is particularly useful for:

•	Vehicle comfort

•	Durability

•	Vehicle control prototyping, or

•	Vibration analysis

For this tire interface, the tire parameters and properties are set by a Tire Property File with the extension (.tir) while the road interface is described by a Road Property File with the extension (.rdf). Both of these property files are in the TeimOrbit file format. Example property files are provided in the MotionView installation at:

$(ALTAIR_HOME) \hw\mdl\autoentities\properties\Tires < tire property file with .tir extension>

$(ALTAIR_HOME) \hw\mdl\autoentities\properties\Tires < road property file with .rdf extension>

In addition to this, physical properties of the tire such as the unloaded radius, aspect ratio, width, mass, and moment of inertia’s need to be explicitly specified.

Connectivity

Select the Body to which the tire is to be attached, select the point that represents the wheel center, and select the two markers that set the orientation of the tire.

Connection	Significance
Body 1	The wheel body on which the tire forces act.
Point 1	The point corresponding to the wheel center.
Marker 1	The wheel reference marker which determines the direction in which the tire forces act.
Marker 2	The road reference marker, is the marker with respect to which the road is positioned and oriented for the simulation

mf_tire_panel_mv

mf_tire_example_mv

mf_tire_example2_mv

Symmetry

The Auto MF-Tire Auto Entity can be added to a full vehicle model as a Single entity or as a Pair. The Pair entity, like other MotionView Pair entities, establishes two symmetric (left and right) Tire models about the X axis.

mf_tire_panel_symmetry_mv

An additional option determines if the symmetry should be mapped from left to right or right to left. Symmetry can be disabled for Auto MF-Tire Pairs.

Tire Geometry and Physical Parameters

Information about the tire physical tire properties such as unloaded radius, aspect ratio, width, mass, and moment of inertia need to be provided correctly. These are specified in the panel in the section highlighted below:

mf_tire_panel_properties_mv

Parameter	Description	Units [Model Units]
Unloaded radius	Distance between the WC and the contact point of tire in unloaded conditions.	Length
Aspect ratio	Tire Sidewall profile aspect ratio. Describes the sidewall height as a percentage of the tire section width.	%
Width	Section width of the tire.	Length
Tire mass	Mass of the tire.	Mass
Ixx,Iyy,Izz	Moment of Inertia of the tire (y-axis out of plane of tire).	Mass * Length2

Tire Models

The TNO interface implements two tire models:

•	SWIFT TIRE – TNO

•	MF TIRE – TNO

The parameter PROPERTY_FILE_FORMAT in the MODEL section of the tire property file determines tire model used. The User is expected to choose a compatible road model with the tire model chosen via the property file.

Sample Property Files:

[HEADER]

FILE_TYPE ='tir'

FILE_VERSION =3.0

FILE_FORMAT ='ASCII'

! FILE_NAME : TNO_car205_60R15.tir

! TIRE_VERSION : MF-Tyre/MF-Swift 6.1

! MF-TOOL TEMPLATE : TNO_mfswift61 $Revision: 1.11 $

! Copyright TNO 2010

$----------------------------------------------------------------units

[UNITS]

LENGTH ='meter'

FORCE ='newton'

ANGLE ='radians'

MASS ='kg'

TIME ='second'

$----------------------------------------------------------------model

[MODEL]

FITTYP = 61 $Magic Formula Version number

TYRESIDE ='Left'

LONGVL = 16.7 $Nominal speed

VXLOW = 1 $Lower boundary of slip calculation

ROAD_INCREMENT = 0.01 $Increment in road sampling

ROAD_DIRECTION = 1 $Direction of travelled distance

PROPERTY_FILE_FORMAT = 'SWIFT-TYRE'

FUNCTION_NAME = 'tnodelft::DTYRE'

ROAD_SOURCE = 'TNO'

USER_SUB_ID = 815

N_TIRE_STATES = 4

USE_MODE = 114 $Tyre use mode switch (ADAMS only)

HMAX_LOCAL = 2.5E-4 $Local integration time step (ADAMS only)

TIME_SWITCH_INTEG = 0.1 $Time when local integrator is activated (ADAMS only)

$-----------------------------------------------------------dimensions

[DIMENSION]

UNLOADED_RADIUS = 0.3135 $Free tyre radius

WIDTH = 0.205 $Nominal section width of the tyre

RIM_RADIUS = 0.1905 $Nominal rim radius

RIM_WIDTH = 0.152 $Rim width

ASPECT_RATIO = 0.6 $Nominal aspect ratio

$-------------------------------------------------operating conditions

[OPERATING_CONDITIONS]

INFLPRES = 220000 $Tyre inflation pressure

NOMPRES = 220000 $Nominal tyre inflation pressure

(Truncated)

$---------------------------------------------------------------------HEADER

[HEADER]

FILE_TYPE = 'rdf'

FILE_VERSION = 5.00

FILE_FORMAT = 'ASCII'

! road data file for TNO_flat_road

$--------------------------------------------------------------------------units

[UNITS]

LENGTH = 'meter'

FORCE = 'newton'

ANGLE = 'radians'

MASS = 'kg'

TIME = 'sec'

$---------------------------------------------------------------------definition

[MODEL]

PROPERTY_FILE_FORMAT = 'USER'

FUNCTION_NAME = 'mssticsub::ROAD'

METHOD = '2D'

ROAD_TYPE = 'flat'

$---------------------------------------------------------------------parameters

[PARAMETERS]

MU = 1.0 $ peak friction scaling coefficient

OFFSET = 0 $ vertical offset of the ground wrt inertial frame

Output Requests

The Auto MF-Tire entity generates some standard output requests into the solver deck. These requests track the tire kinematics and the tire forces generated by the tire model.

Label	Description	Units
Radius OmegaActual OmegaFree	X – Deformed radius of the Tire. Y – Actual Rotational speed of the tire. Z – Rational Speed considering Unloaded radius.	Length rad/time rad/time
LonSlip LatSlip IncAngle	X – Longitudinal Slip of the tire. Y – Lateral Slip of the tire. Z – Inclination angle of the tire. In the ISO axis system.	% rad rad
Tire CP Forces (W-Axis system)	Tire force and moments with reference to the ISO- Axis system at the tire contact patch.	Force & Force*Length
Tire CP Forces (SAE-Axis System)	Tire force and moments with reference to the SAE- Axis system at the tire contact patch.	Force & Force*Length
LonSlip LatSlip IncAngle	X – Longitudinal Slip of the tire. Y – Lateral Slip of the tire. Z – Inclination angle of the tire. In the SAE axis system.	[No Units] Deg Deg
Tire Hub Forces (C-Axis System)	Tire force and moments with reference to the ISO axis system at the wheel center.	Force & Force*Length
Contact Patch Location	X,Y,Z of the Contact Patch Location.	Length
Hub Velocity	The translation and rotational velocities of the hub.	Length / time