Virtual Caster and Kingpin Angles
Request Number: 50000330
The kingpin axis or steer axis on an SLA or Macpherson strut suspension is defined by two points (the upper ball joint and the lower ball joint in the SLA suspension, the upper strut mount location and the lower ball joint in the case of the Macpherson strut suspension). When the kingpin axis is not defined by two distinct points, it must be calculated virtually, using the motion of the spindle to calculate the instant axis of rotation of the knuckle. The virtual requests (numbers 50000310-50000350) use this method to calculate the kingpin axis location, and the parameters that rely on it. These requests should be used on suspensions that do not have a clearly defined kingpin axis, such as a 4 link or 5 link front independent suspension.
For the computation of the kingpin axis, the steering needs to be free (no motion) and the suspension travel needs to be locked. The lock needs to be defined in the model and will be invoked, when computing the kingpin axis automatically. Defining the lock in the model involves the definition of an array, containing the position, direction and body to lock and calling a user subroutine to pass this information to the solver. See Locking Steering and Spring Travel for details.
| .plt File | .abf, .mrf File | Component | Unit | Comment |
|---|---|---|---|---|
| F2 | RESULT(2) | Left Virtual Caster Angle | deg | The angle measured from the global Z axis to the left steer axis in the side view (Z-X PLANE). Virtual caster angle is positive when the top of the steer axis inclines toward the rear of the vehicle. |
| F3 | RESULT(3) | Right Virtual Caster Angle | deg | The angle measured from the global Z axis to the right steer axis in the side view (Z-X PLANE). Virtual caster angle is positive when the top of the steer axis inclines toward the rear of the vehicle. |
| F4 | RESULT(4) | Average Virtual Caster Angle | deg | The mean of the left and right virtual caster angles. |
| F6 | RESULT(6) | Left Virtual Kingpin Angle | deg | The angle measured from the global Z axis to the left steer axis in the side view (Z-Y PLANE). Virtual kingpin angle is positive when the top of the steer axis inclines toward the center of the vehicle. |
| F7 | RESULT(7) | Right Virtual Kingpin Angle | deg | The angle measured from the global Z axis to the right steer axis in the side view (Z-Y PLANE). Virtual kingpin angle is positive when the top of the steer axis inclines toward the center of the vehicle. |
| F8 | RESULT(8) | Average Virtual Kingpin Angle | deg | The mean of the left and right virtual kingpin angle. |