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Appendix B: Fortran tyre model subroutines 483
C
Critical Slip Angle (Max Lateral Force) - degrees in
User Array
ALPHA_C PAR(1)
C
Curvature Factor (exponential function to peak slip
angle)
Ay PAR(2)
C
Scale Factor for Lateral Force at Rated Load
By PAR(3)
C
Rated Load (N)
R_LOAD PAR(4)
C
Diminution of Scale Factor with load
dB_dFz PAR(5)
C
Max Slip angle
ALPHA_M PAR(6)
C Critical Slip Ratio (Max Longitudinal Force) %
SLIP_C PAR(7)
C
Curvature Factor (exponential function to peak slip ratio)
Ax PAR(8)
C
Max Slip Ratio
SLIP_M PAR(9)
C -- Debug only - check we’re getting what we think --
C IF ( IFLAG .eq. .TRUE. ) THEN
C WRITE(*,*) ‘ALPHA_C ’, ALPHA_C, ‘, Ay ’, Ay, ‘, By ’, By
C WRITE(*,*) ‘R_LOAD’, R_LOAD, ‘, dB_dFz ’, dB_dFz
C WRITE(*,*) ‘ALPHA_M ’, ALPHA_M, ‘, SLIP_C ’, SLIP_C,
‘, Ax ’, Ax
C WRITE(*,*) ‘SLIP_M ’, SLIP_M
C ENDIF
C Tyre Modelling Proper Begins
C Initialize force values
C
FX0.D0
FY0.D0
FZ0.D0
TX0.D0
TY0.D0
TZ0.D0
C -- Wheel off the ground? Easy – everything zero --
IF(DEFL .LE. 0.D0) THEN
GOTO 1000
ENDIF
C Normal Loads; simple calculations as with sample tirsub.f;
C Penetrations to hub are not accounted for.
C -- Calculate normal loads due to stiffness (always .LE. zero) --
FZDEFL-DEFL*CZ
C -- Calculate normal loads due to damping --
FZDAMP-2.D0*SQRT(AMASS*CZ)*DZ*(DEFLD)
C -- Ease up on the damping force scale factor at small deflections --
DELMAX0.01*R2
IF (DEFL .LE. DELMAX) THEN
CALL STEP(DEFL, ZERO, ZERO, DELMAX, ONE, IORD,
SCFACT, ERFLG)