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The transfer case component models a transfer case in
one of four modes: RWD - Rear Wheel Drive
FWD - Front Wheel Drive
AWD - All Wheel Drive
4WD - Four Wheel Drive
In RWD all the transmission torque is applied to the
rear wheels:
Torque4=Torque1
Vel1=Vel4
Torque3=0
In FWD all the transmission torque is applied to the
front wheels:
Torque3=Torque1
Vel1=Vel3
Torque4=0
In AWD the input torque Torque1 is split equally
between Torque3 and Torque4.
Torque3 = Torque4 = Torque1/2
If the speed difference between Vel3 and Vel4 is
greater than MinSpeedDiff an additional torque is
applied:
Torque3 = Torque1/2 + TorqueTransfer *
(Vel4-Vel3-MinSpeedDiff)
Torque4 = Torque1/2 - TorqueTransfer *
(Vel4-Vel3-MinSpeedDiff)
The upstream velocity Vel1 is calculated by averaging
the input velocities:
Vel1=(Vel3+Vel4)/2
In 4WD a spring and damper are placed between the
front and rear shafts to keep their velocities close to
equal.
The input torque is applied to the front wheels:
Torque3=Torque1+K*PosDiff+D*(Vel4-Vel3)
Torque4=-K*PosDiff-D*(Vel4-Vel3)
Vel1=Vel3
Where PosDiff is the integral of the speed difference
Vel4-Vel3.
The positive direction of velocity and torque is
arbitrary.
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