Vehicle wheel alignment methods and systems

Abstract

A wheel alignment system includes a side-to-side reference including an active reference pod and a passive reference pod disposed on opposite sides of the vehicle. The active reference pod includes a reference image sensor fixedly attached to a reference target, for mounting on a first side of the vehicle such that the reference image sensor produces image data including a perspective representation of the passive reference pod disposed on a second/opposite side of the vehicle. In operation, alignment cameras on the opposite sides of the vehicle capture perspective representations of targets mounted to vehicle wheels and of targets of the active and passive reference pods. A computer processes the image data to compute an alignment measurement of the vehicle based on a spatial relationship between the active reference pod and the passive reference pod determined according to the image data produced by the reference image sensor.

What is claimed is: 
     
         1 . A wheel alignment system comprising:
 a pair of first and second passive heads, each comprising a target, for mounting in association with a first pair of wheels disposed on first and second sides, respectively, of a vehicle that is to be measured by operation of the wheel alignment system;   an active reference pod comprising a reference image sensor fixedly attached to a reference target, for mounting on the first side of the vehicle such that the reference image sensor produces image data including a perspective representation of a passive reference pod comprising at least one target disposed on the second side of the vehicle;   a pair of first and second active heads, each comprising an image sensor, for mounting in association with the first and second sides of the vehicle, respectively, the image sensor of the first active head producing image data including a perspective representation of the targets of the first passive head and of the active reference pod, and the image sensor of the second active head producing image data including a perspective representation of the targets of the second passive head and of the passive reference pod; and   a computer for processing image data from the image sensors relating to the observations of the targets to compute at least one alignment measurement of the vehicle based on a spatial relationship between the active reference pod and the passive reference pod determined according to the image data produced by the reference image sensor.   
     
     
         2 . The wheel alignment system of  claim 1 , wherein the computer computes the spatial relationship between the active reference pod and the passive reference pod based on the image data produced by the reference image sensor and including the perspective representation of the passive reference pod, and based on a known spatial relationship between the reference image sensor and the reference target of the active reference pod. 
     
     
         3 . The wheel alignment system of  claim 1 , wherein the passive reference pod comprises first and second targets, the reference image sensor produces image data including a perspective representation of the first target of the passive reference pod, and the image sensor of the second active head produces image data including a perspective representation of the second target of the passive reference pod. 
     
     
         4 . The wheel alignment system of  claim 3 , wherein the first and second targets of the passive reference pod have a known spatial relationship to each other, and the computer computes the spatial relationship between the active reference pod and the passive reference pod according to the image data produced by the image sensors and the known spatial relationship between the first and second targets of the passive reference pod. 
     
     
         5 . The wheel alignment system of  claim 1 , wherein the active and passive reference pods are for mounting to a stationary reference. 
     
     
         6 . The wheel alignment system of  claim 1 , wherein the first and second active heads are for mounting to a stationary reference. 
     
     
         7 . The wheel alignment system of  claim 1 , wherein the first and second active heads are for mounting to the vehicle that is to be measured by operation of the wheel alignment system. 
     
     
         8 . The wheel alignment system of  claim 7 , wherein the first and second active heads are for mounting in association with a second pair of wheels disposed on the first and second sides of the vehicle. 
     
     
         9 . A method for measuring an alignment of a vehicle comprising:
 attaching a pair of first and second passive heads, each comprising a target, in association with a first pair of wheels disposed on first and second sides, respectively, of the vehicle that is to be measured;   providing an active reference pod, comprising a reference image sensor fixedly attached to a reference target, on the first side of the vehicle;   capturing, using the reference image sensor of the active reference pod provided on the first side of the vehicle, image data including a perspective representation of a passive reference pod comprising at least one target disposed on the second side of the vehicle;   capturing, using an image sensor of a first active head mounted in association with the first side of the vehicle, image data including a perspective representation of the targets of the first passive head and of the active reference pod;   capturing, using an image sensor of a second active head mounted in association with the second side of the vehicle, image data including a perspective representation of the targets of the second passive head and of the passive reference pod; and   processing the image data from the image sensors relating to the observations of the targets to compute at least one alignment measurement of the vehicle based on a spatial relationship between the active reference pod and the passive reference pod determined according to the image data produced by the reference image sensor.   
     
     
         10 . The method of  claim 9 , wherein the processing comprises computing the spatial relationship between the active reference pod and the passive reference pod based on the image data produced by the reference image sensor and including the perspective representation of the passive reference pod, and based on a known spatial relationship between the reference image sensor and the reference target of the active reference pod. 
     
     
         11 . The method of  claim 9 , wherein the passive reference pod comprises first and second targets,
 the capturing, using the reference image sensor, image data comprises capturing image data including a perspective representation of the first target of the passive reference pod, and   the capturing, using the image sensor of the second active head, image data comprises capturing image data including a perspective representation of the second target of the passive reference pod.   
     
     
         12 . The method of  claim 11 , wherein the first and second targets of the passive reference pod have a known spatial relationship to each other, and the processing the image data comprises computing the spatial relationship between the active reference pod and the passive reference pod according to the image data produced by the image sensors and the known spatial relationship between the first and second targets of the passive reference pod. 
     
     
         13 . The method of  claim 9 , further comprising mounting the active and passive reference pods to a stationary reference prior to capturing image data using the reference image sensor and the image sensors of the first and second active heads. 
     
     
         14 . The method of  claim 9 , further comprising mounting the first and second active heads to a stationary reference prior to capturing image data using the image sensors of the first and second active heads. 
     
     
         15 . The method of  claim 9 , further comprising mounting the first and second active heads in association with the vehicle that is to be measured by operation of the wheel alignment system prior to capturing image data using the images sensors of the first and second active heads. 
     
     
         16 . The method of  claim 15 , wherein the mounting comprises mounting the first and second active heads in association with a second pair of wheels disposed on the first and second sides of the vehicle.