An Adams model of a vehicle is usually built at design height with the front and rear wheels oriented using the wheel center MARKERs and the spindle orientation MARKERs. This procedure, though correct, does not ensure proper vehicle alignment at the curb position. This is due to suspension compliances, geometry, and unsymmetric loading of the vehicle. To ensure proper toe, caster, and camber for simulations, the Adams model should be aligned at the curb position once model build is complete.

The routine described in this section performs an automated alignment on an Adams model using user defined alignment specifications. The program adjusts standard MOTION statements until the vehicle alignment specifications agree within 0.01 of the user desired values (or after 25 iterations have been run). The output MOTION statement values are then written to a file for easy inclusion into an Adams model.

To use the program, the Adams model must first be setup to the correct loading condition (curb or curb plus driver) and contain the following MOTION statements and ARRAYS:

For a front suspension -

MOTION/81 - translational or revolute joint in left tie rod
MOTION/82 - translational or revolute joint in right tie rod
MOTION/83 - translational or revolute joint for left wheel caster change
MOTION/84 - translational or revolute joint for right wheel caster change
MOTION/85 - translational or revolute joint for left wheel camber change
MOTION/86 - translational or revolute joint for right wheel camber change
ARRAY/aryid1, NUM = 10,0,lkam,lwcm,0.0,rkam,rwcm,brm

where:

aryid1 = front suspension aligner array id
lkam = left front kingpin axis MARKER id
lwcm = left front wheel center MARKER id
rkam = right front kingpin axis MARKER id
rwcm = right front wheel center MARKER id

For a rear suspension -

MOTION/181 - translational or revolute joint for left toe change
MOTION/182 - translational or revolute joint for right toe change
MOTION/183 - translational or revolute joint for left wheel caster change
MOTION/184 - translational or revolute joint for right wheel caster change
MOTION/185 - translational or revolute joint for left wheel camber change
MOTION/186 - translational or revolute joint for right wheel camber change
ARRAY/aryid2, NUM = 10,0,lkam,lwcm,0.0,rkam,rwcm,brm

aryid2 = rear suspension aligner array id
lkam = left rear kingpin axis MARKER id
lwcm = left rear wheel center MARKER id
rkam = right rear kingpin axis MARKER id
rwcm = right rear wheel center MARKER id

Note that the ARRAY statements should contain the same MARKERs as the toe/caster/camber user written REQUEST. Also, the alignment angles are all assumed to be in the standard sign convention of:

Positive toe is toe in

Positive caster is kingpin axis slanted rearward at the top

Positive camber is top of tire leaned outboard of the vehicle

To align an Adams model, the user invokes the autoaligner CONSUB from the ENTER COMMAND prompt. The syntax for the CONSUB call is:

CONTROL/FUNC=USER( altype,jpr_ary ,pid,aryid3,aryid4,aryid5,halt,error,maxit )

where:

It is important to note that if the user enters a value greater than +20 degrees or less than -20 degrees for any of the alignment specifications, the CONSUB will not align that particular angle. For example, a user may want to align only the toe of a given front suspension to 0.01 degrees but not caster or camber. To do this, the CONSUB call would be:

If the user selects "No Auto-Alignment" from the Adams Car GUI, the code will use the saved alignment settings from the appropriate front or rear datafile. A message will be echoed to the screen during build to remind the user that these settings are being used.