Computes the ideal steer radius, average steer angle, outside turn diameter, either linkage ratio or rack-and-pinion ratio, Ackerman angle, and percent Ackerman
Input:
REQ/id, FUNCTION = USER(1106,type,wb,width,lwcm,lkm,rwcm,rkm,pm,prm,rm,rrm,brm,iack)
where:
| | Description |
|---|
type | = | steering type
0 = steering gear with pitman arm
1 = rack-and-pinion steering |
wb | = | wheel base (mm) |
width | = | wheel width (mm) |
lwcm | = | left wheel center MARKER id |
lkm | = | left kingpin MARKER id |
rwcm | = | right wheel center MARKER id |
rkm | = | right kingpin MARKER id |
pm | = | pitman or pinion MARKER id |
prm | = | pitman or pinion reference MARKER id |
rm | = | rack MARKER id (only for rack-and-pinion steering) |
rrm | = | rack reference MARKER id (only for rack-and-pinion) |
brm | = | body reference MARKER id (usually body center of mass) |
iack | = | Ackerman formula selection flag (1 for Truck method)
if iack = 0 % Ackerman = ( ai - ao ) / ( aic - aoc )
if iack = 1 % Ackerman = ( ai - ao ) / ( ai - aob )
where: ai=inside wheel steer angle
ao=outside wheel steer angle
aic=inside wheel steer angle required to have the wheel plane perpendicular line intersect a line passing through the rear axle at the center point between where the inside tire perpendicular intersects the axle line and where the outside tire perpendicular intersects the line.
aoc=outside wheel steer angle required to have the wheel plane perpendicular line intersect a line passing through the rear axle at the center point between where the inside tire perpendicular intersects the axle line and where the outside tire perpendicular intersects the line.
aob=outside wheel turn angle required to have the wheel plane perpendicular line intersect a line passing through the rear axle at the same point that the inside tire perpendicular intersects the axle line. |
Request File Output
Column Number Output:
1. Ideal steer radius (mm)
2. Average ideal steer angle (deg)
3. Outside ideal turn diameter (mm)
4. Linkage ratio (pitman arm steering) or Pinion-to-rack ratio (rack-and-pinion)
5. Ackerman angle (deg)
6. Percent Ackerman (%)
Notes on Input and Output
The wheel center MARKERs are at the wheel centers and have their Z axis perpendicular to the plane of the tire and pointing out of the vehicle. The kingpin MARKERs have a QP at the kingpin intersection and a ZP at the kingpin axis point (which is above the kingpin intersection and on the kingpin axis).
If the vehicle has a steering gear with a pitman arm, the pitman MARKER is on the pitman at the body-to-pitman joint with its ZP at the pitman axis point. The pitman reference MARKER has the same location and orientation as the pitman MARKER, but the pitman reference MARKER is on the body rather than pitman.
If the vehicle has rack-and-pinion steering, the pinion MARKER is on the pinion at the body-to-pinion joint with its ZP at the pinion axis point. The pinion reference MARKER has the same location and orientation as the pinion MARKER, but the pinion reference MARKER is located on the body rather than on the pinion. For rack-and-pinion steering, the rack MARKER is on the rack at the rack-to-body joint with its Z axis pointing in the global negative Y direction. The rack reference MARKER has the same location and orientation as the rack MARKER, but the rack reference MARKER is on the body rather than on the rack. The body reference MARKER is on the body and has the same initial orientation as the global reference frame.