초록 ▼

An improved method and system are provided for performing rolling runout compensation for vehicle wheel alignment. A plurality of sets of camber and toe measurements are acquired for a pair of vehicle wheels, each at a different, relatively small rollback angle between measurements; e.g., rolling th

An improved method and system are provided for performing rolling runout compensation for vehicle wheel alignment. A plurality of sets of camber and toe measurements are acquired for a pair of vehicle wheels, each at a different, relatively small rollback angle between measurements; e.g., rolling the vehicle more than 0° and less than 180° from the last wheel position. Best fit sine waves are computed for each of the camber and toe measurements using the acquired data, and the best fit parameters are applied to compute runout at the current wheel angle. The computed runouts are subtracted from the measured camber and toe values to get true camber and toe values of the pair of wheels.

대표청구항 ▼

1. A method comprising: acquiring a plurality of sets of camber and toe measurement values for a pair of vehicle wheels, each set being acquired at a different measured wheel angle obtained by rolling the wheels from an initial wheel angle, wherein one of the wheel angles is a current wheel angle;ca

1. A method comprising: acquiring a plurality of sets of camber and toe measurement values for a pair of vehicle wheels, each set being acquired at a different measured wheel angle obtained by rolling the wheels from an initial wheel angle, wherein one of the wheel angles is a current wheel angle;calculating best fit sine waves for camber and toe using a least squares analysis and the sets of camber measurement values, toe measurement values, and measured wheel angles obtained by rolling the wheels;computing camber runout and toe runout at the current wheel angle using the calculated sine waves;subtracting the respective computed runouts from the measured camber and toe measurement values at the current wheel angle to obtain true camber and toe values for the pair of wheels; anddisplaying the true camber and toe values. 2. The method of claim 1, comprising acquiring the sets of camber and toe measurement values by: acquiring a set of camber and toe measurement values at the initial wheel angle;rolling the wheels from the initial angle to a first rollback wheel angle;acquiring a set of camber and toe measurement values at the first rollback wheel angle;rolling the wheels from the first rollback wheel angle to a second rollback wheel angle; andacquiring a set of camber and toe measurement values at the second rollback wheel angle;wherein the second rollback wheel angle is the current wheel angle. 3. The method of claim 2, comprising rolling the wheels about 20° to about 40° from the initial angle to the first rollback wheel angle, and rolling the wheels about 20° to about 40° from the first rollback wheel angle to the second rollback wheel angle. 4. The method of claim 2, comprising rolling the wheels about 20° to about 40° from the initial angle to the first rollback wheel angle, and rolling the wheels more than 0° and less than 180° from the first rollback wheel angle to the second rollback wheel angle. 5. The method of claim 1, comprising acquiring one of the sets of camber and toe measurement values by rolling the wheels about 20° to about 40° from the initial wheel angle. 6. The method of claim 1, comprising calculating best fit sine waves for camber and toe using a matrix least squares analysis. 7. The method of claim 1, wherein acquiring the sets of camber and toe measurement values comprises: obtaining an image of a target associated with a first wheel of the vehicle, from an image sensor in a first head mounted in association with a second wheel of the vehicle to produce first image data;determining a tilt angle of the first head;obtaining an image of a target associated with a third wheel of the vehicle, from an image sensor in a second head mounted in association with a fourth wheel of the vehicle to produce second image data;determining a tilt angle of the second head;measuring a spatial relationship between the first and second heads; andprocessing the first and second image data, the tilt angles and the spatial relationship measurement, to compute the camber and toe measurement values for the second and fourth wheels of the vehicle;wherein the pair of vehicle wheels comprises the second and fourth wheels of the vehicle. 8. The method of claim 1, wherein acquiring the sets of camber and toe measurement values comprises: obtaining an image of a target associated with a first wheel of the vehicle, from an image sensor in a first head disposed stationary relative to the vehicle to produce first image data;obtaining an image of a target associated with a second wheel of the vehicle, from an image sensor in a second head disposed stationary relative to the vehicle to produce second image data;measuring a spatial relationship between the first and second heads; andprocessing the first and second image data and the spatial relationship measurement, to compute the camber and toe measurement values for the first and second wheels of the vehicle;wherein the pair of vehicle wheels comprises the first and second wheels of the vehicle. 9. The method of claim 1, comprising acquiring one of the sets of camber and toe measurement values by rolling the wheels more than 0° and less than 180° from the initial wheel angle. 10. A wheel alignment system, comprising: a pair of passive heads, each comprising a target, for mounting in association with a first pair of wheels of a vehicle that is to be measured by operation of the wheel alignment system;a pair of active sensing heads for mounting in association with a second pair of wheels of the vehicle, each respective one of the active sensing heads comprising an image sensor for producing image data including a representation of an image of one of the targets, at least one of the active sensing heads comprising at least one tilt sensor for sensing a tilt angle of the one active sensing head when the one active sensing head is mounted on a wheel of the vehicle;means for determining a spatial relationship between the active sensing heads, when the active sensing heads are mounted on wheels of the vehicle;a display; anda computer for: processing image data relating to observation of the targets, the sensed tilt angle, and relationship data from the means for determining the spatial relationship, to compute a plurality of sets of camber and toe measurement values for the second pair of vehicle wheels when the active sensing heads are mounted on the second pair of vehicle wheels, each set being computed at a different measured wheel angle obtained by a user rolling the wheels from an initial wheel angle, wherein one of the wheel angles is a current wheel angle;calculating best fit sine waves for camber and toe using a least squares analysis and the sets of camber measurement values, toe measurement values, and measured wheel angles obtained by rolling the wheels;computing camber runout and toe runout at the current wheel angle using the calculated sine waves;subtracting the respective computed runouts from the measured camber and toe measurement values at the current wheel angle to obtain true camber and toe values for the second pair of wheels; andcausing the true camber and toe values for the second pair of wheels to be displayed on the display. 11. The wheel alignment system of claim 10, wherein the means for determining the spatial relationship comprises two relative angle sensing modules, one module being associated with each of the active sensing heads. 12. The wheel alignment system of claim 11, wherein each of the sensing modules comprises: an emitter for emitting a beam of light; an aperture; and an image sensor for sensing an angle of an incoming beam of light through the aperture. 13. The wheel alignment system of claim 10, wherein the means for determining the spatial relationship comprises an illuminator and a camera mounted on a first one of the active sensing heads. 14. The wheel alignment system of claim 10, wherein the computer is for computing the sets of camber and toe measurement values by: computing a set of camber and toe measurement values at the initial wheel angle;computing a set of camber and toe measurement values at a first rollback wheel angle after the user rolls the wheels from the initial angle to the first rollback wheel angle; andcomputing a set of camber and toe measurement values at a second rollback wheel angle after the user rolls the wheels from the first rollback wheel angle to the second rollback wheel angle;wherein the second rollback wheel angle is the current wheel angle. 15. The wheel alignment system of claim 14, wherein the user rolls the wheels about 20° to about 40° from the initial angle to the first rollback wheel angle, and rolls the wheels about 20° to about 40° from the first rollback wheel angle to the second rollback wheel angle. 16. The wheel alignment system of claim 14, wherein the user rolls the wheels more than 0° and less than 180° from the initial angle to the first rollback wheel angle, and rolls the wheels more than 0° and less than 180° from the first rollback wheel angle to the second rollback wheel angle. 17. The wheel alignment system of claim 10, comprising computing one of the sets of camber and toe measurement values after the user rolls the wheels about 20° to about 40° from the initial wheel angle. 18. The wheel alignment system of claim 10, wherein the computer is for calculating best fit sine waves for camber and toe using a matrix least squares analysis. 19. The wheel alignment system of claim 10, wherein when the pair of active sensing heads are disposed stationary relative to the vehicle such that the means for determining a spatial relationship between the active sensing heads is functional, the computer is for: processing image data relating to observation of the targets and relationship data from the means for determining the spatial relationship, to compute a plurality of sets of camber and toe measurement values for the first pair of vehicle wheels, each set being computed at a different wheel angle obtained by a user rolling the wheels from an initial wheel angle, wherein one of the wheel angles is a current wheel angle;calculating best fit sine waves for camber and toe using a least squares analysis and the sets of camber and toe measurement values;computing camber runout and toe runout at the current wheel angle using the calculated sine waves;subtracting the respective computed runouts from the measured camber and toe measurement values at the current wheel angle to obtain true camber and toe values for the first pair of wheels; andcausing the true camber and toe values for the first pair of wheels to be displayed on the display. 20. The wheel alignment system of claim 10, comprising computing one of the sets of camber and toe measurement values after the user rolls the wheels more than 0° and less than 180° from the initial wheel angle.