Patent ID: 7415770

Claim:
A wheel alignment angle measuring apparatus comprising: a sensor signal receiving unit configured to receive output signals from a sensor which measures a value of a lateral force generated in a reference wheel in a predetermined period including a deformation maximum time point when deformation of the reference wheel becomes substantially maximum due to an event that the reference wheel runs on a predetermined protrusion, the reference wheel being any one of wheels provided with pneumatic tires and mounted on a vehicle; a variation energy sum computing unit configured to compute a first-half-period variation energy sum which is a sum of variation rate of the lateral force in a first half period until the deformation maximum time point, and a last-half-period variation energy sum which is a sum of variation rate of the lateral force in a last half period from the deformation maximum time point using the output signals respectively; a reference-wheel referencing alignment angle computing unit configured to compute a reference wheel referencing alignment angle which is an alignment angle at an intersection of a first-half-period straight line determined based on a value of the first-half-period variation energy sum when an alignment angle of the reference wheel vary, and a last-half-period straight line determined based on a value of the last-half-period variation energy sum when the alignment angle of the reference wheel vary; and a non-reference wheel setting alignment angle computing unit configured to compute, based on the reference wheel referencing alignment angle, a non-reference wheel setting alignment angle to be specified for a non-reference wheel mounted on the vehicle in a position different in an anteroposterior direction from a position in which the reference wheel is mounted.