Abstract: A fault detecting and automatic calibrating apparatus is provided for monitoring the position of a monitored apparatus. The calibrating apparatus detects errors and corrects the errors during its monitoring operation. In one embodiment, the monitored apparatus is a wheel alignment testing apparatus which checks a front wheel suspension system for proper alignment. The wheel aligner is simultaneously moveable about both a vertical axis and a horizontal axis. The movements of the wheel aligner are detected by transducers which provide angle signals corresponding to a toe angle and a camber angle of a wheel being tested. The calibrating apparatus checks the magnitude of the angle signals whenever a control circuit outputs a target pulse indicating that the toe angle or camber angle of the wheel is at predetermined angles. The predetermined angles are conveniently selected at zero degrees and a positive one degree.

Abstract: An automatic calibrator is provided in combination with a wheel aligner used in determining the toe angle and camber angle of a wheel. A target is connected to the wheel aligner to move therewith. When the wheel aligner is at a predetermined angle, the target is used to provide a signal indicating that the wheel aligner is at the predetermined angle. A transducer output signal is then checked to determine if the transducer output signal accurately corresponds to the predetermined angle.

Abstract: A wheel alignment apparatus and method are provided for use in aligning the front wheels of a vehicle. The wheel alignment apparatus includes a dynamic wheel aligner which determines the dynamic toe angle and dynamic camber angle of a wheel using the axial displacement of rolls upon which each front wheel is rotatable. The wheel alignment apparatus stores these dynamically determined values and stops the rotation of the rolls. After predetermined time delays, an alignment operator makes adjustments to the toe and camber angles of the wheel so that these angles are within a desired range. The changes in the toe angle and camber angle during alignment are determined by the apparatus and combined with the dynamically determined toe and camber angles. As a result, the alignment operator continuously has a visual indication of the toe and camber angles during alignment.