Adams Car Package > Adams Tire > User-Written Tire/Road Models > Utilities for Calculating Tire Forces and Moments

Utilities for Calculating Tire Forces and Moments

Adams Tire provides a set of utility subroutines you can use in your user tire model to calculate tire kinematics and vertical forces and to transfer tire forces and moments from the contact path to the wheel center. Learn about the utilities:

■ACTCLC

■ACTFZ

■XCP2HB

ACTCLC

Calling Sequence

SUBROUTINE ACTCLC(TRAMAT, VEL, OMEGA, OMEGAR, RADIUS, RNORM,
VLON, VCPLON, VCPLAT, VCPVRT,
ALPHA, GAMMA, KAPPA,
URAD, CPMTX)

Description

Given the wheel/tire's orientation (TRAMAT) and velocity (VEL, OMEGA, OMEGAR) relative to the road and the local road normal (RNORM), ACTCLC computes tire kinematics in the SAE axis system. The tire kinematics are:

■Contact-patch velocities

■Slip angle (ALPHA)

■Inclination angle (GAMMA)

■Longitudinal slip (KAPPA)

■SAE contact-patch axis system (CPMTX)

■Unit vector directed from the wheel center to the contact patch (URAD)

Arguments

Argument:	Type:*	Storage:	Use* and Description:
TRAMAT	DA	3,3	R	Transformation from ISO wheel carrier (TYDEX ISO-C system) axis system to road (earth) axis system.
VEL	DA	3	R	Translational velocity of wheel carrier in ISO wheel carrier axis system.
OMEGA	DA	3	R	Rotational velocity of wheel carrier in ISO wheel carrier axis system.
OMEGAR	DS	1	R	Rotational speed of the rim (wheel) with respect to the wheel carrier about the +y axis of the ISO wheel carrier axis system.
RADIUS	DS	1	R	The loaded tire radius (for example, distance from the wheel center to the road surface in the plane of the wheel).
RNORM	DA	3	R	Unit vector giving the local road normal in the road (earth) axis system. The road normal must be directed upward from the road surface.
VLON	DS	1	E	The longitudinal velocity of the tire in TYDEX ISO-C axis system.
VCPLON	DS	1	E	The SAE contact-patch longitudinal velocity.
VCPLAT	DS	1	E	The SAE contact-patch lateral velocity.
VCPRVT	DS	1	E	The SAE contact-patch vertical velocity.
ALPHA	DS	1	E	Slip angle in SAE axis system.
GAMMA	DS	1	E	Inclination (camber) angle.
KAPPA	DS	1	E	Longitudinal slip ratio.
URAD	DA	3	E	Unit vector directed from wheel center to contact patch expressed in road (earth) reference marker axis system.
CPMTX	DA	3,3	E	Transformation matrix from the SAE contact-patch axis system to the road (earth) reference marker axis system.
*Key: Type: A = array; C = character; D = double precision; I = integer (for example, DA indicates double-precision array). Use: R = referenced, but not set; E = evaluated (the subroutine sets the value of this argument).

ACTFZ

Calling Sequence

SUBROUTINE ACTFZ (VCPVRT, RADIUS, TIREK, TIREC, UNLRAD,
FRCRAD, ERRMSG, IERR)

Description

ACTFZ uses the contact-patch vertical velocity in the SAE coordinate system to compute the radial damping. It replaces PNTFRC for calculating tire vertical force.

Arguments

Argument:	Type:*	Storage:	Use* and Description:
VCPVRT	DS	-	R	Vertical contact-patch velocity in SAE coordinates (+z is downward)
RADIUS	DS	-	R	Loaded tire radius
TIREK	DS	-	R	Tire stiffness <n/m>
TIREC	DS	-	R	Tire damping <n*s/m>
UNLRAD	DS	-	R	Unloaded tire radius <m>
FRCRAD	DS	-	E	Radial (vertical) force <n>
ERRMSG	CA	80	E	Error message
IERR	IS	-	E	Error code: IERR = 0, normal execution IERR = 3, problem calling IMPACT function
*Key: Type: A = array; C = character; D = double precision; I = integer (for example, DA indicates double-precision array). Use: R = referenced, but not set; E = evaluated (the subroutine sets the value of this argument).

XCP2HB

Calling Sequence

SUBROUTINE XCP2HB(FCP, TCP, RAD, CPMTX, FORCES, TORQUE)

Description

XCP2HB transforms the contact-patch forces and torques to hub forces and torques expressed in the road reference marker axis system:

forces = [cpmtx]fcp
torque = rad X ([cpmtx]fcp) + [cpmtx]tcp

Arguments

Argument:	Type:*	Storage:	Use* and description:
FCP	DA	3	R	Contact patch forces expressed in SAE axis system (+z is downward).
TCP	DA	3	R	Contact patch torques expressed in SAE axis system (+z is downward).
RAD	DA	3	R	Radius vector from wheel center to contact patch expressed in the road reference marker axis system.
CPMTX	DA	3,3	R	Transformation matrix from SAE contact-patch axis system to the road reference marker axis system.
FORCE	DA	3	E	Hub forces expressed in the road reference marker axis system.
TORQUE	DA	3	E	Hub torques expressed in the road reference marker axis system.
*Key: Type: A = array; C = character; D = double precision; I = integer (for example, DA indicates double-precision array). Use: R = referenced, but not set; E = evaluated (the subroutine sets the value of this argument).