Non-contact method and apparatus for determining camber and caster of a

Abstract

A method and apparatus for determining camber and caster of a vehicle wheel in which the camber angle is determined in a manner that accounts for the influence of any existing toe angle. This is accomplished by detecting the displacement of one or more points located fore or aft of the wheel's vertical measurement plane and then making a correction to these displacements to account for influence of the toe angle. The apparatus includes a laser that projects shaped light onto the sidewall of the tire at a location offset from the normal upper measurement position. The shaped light illuminates an offset measurement point on the tire sidewall and an optical sensor detects the reflected image. A computer then determines the location of the measurement point within the two-dimensional image space of the optical sensor. Trigonometric equations utilizing the toe angle are then used to determine the horizontal displacement within the vertical measurement plane of this offset measurement point from the tire center or other reference point. Once this horizontal displacement is known, the camber can be determined mathematically using a known trigonometric relationship. By determining the camber angle at left and right steered toe angle, the caster angle of the wheel can the be determined.