초록 ▼

The invention relates to a method for non-contact measurement of the alignment of the wheels of a motor vehicle. In practice, the method provides for the steps of: applying a plurality of markers to the wheels of the motor vehicle along a line approximately substantially coaxial with the wheel; posi

The invention relates to a method for non-contact measurement of the alignment of the wheels of a motor vehicle. In practice, the method provides for the steps of: applying a plurality of markers to the wheels of the motor vehicle along a line approximately substantially coaxial with the wheel; positioning, at each wheel for which the characteristic angles must be acquired, two image acquisition devices, with different inclinations with respect to said wheel; acquiring for each of said wheels, through each of said two image acquisition devices, at least one image of said wheel with the relative markers; determining, through epipolar and triangulation geometrical calculations, the equation of an approximate plane in which said markers lie in space, with respect to a reference system; determining the camber and toe angles of said wheel on the basis of the equation of said plane and of the equation of the reference planes with respect to which the motor vehicle takes a known position.

대표청구항 ▼

What we claim is: 1. A method for measuring the angles of inclination of the wheels of a motor vehicle, comprising the steps of: applying a plurality of markers to the wheels of the motor vehicle; providing, at each wheel whose characteristic angles must be acquired, a first image acquisition devic

What we claim is: 1. A method for measuring the angles of inclination of the wheels of a motor vehicle, comprising the steps of: applying a plurality of markers to the wheels of the motor vehicle; providing, at each wheel whose characteristic angles must be acquired, a first image acquisition device and a second image acquisition device, said pair of image acquisition devices having different inclinations and positions with respect to said wheel; for each of said wheels, acquiring at least a first image and a second image of said wheel with the relative markers by means of said first and second image acquisition device respectively; determining the two-dimensional coordinates of the barycentric points of said markers in said first and second image, respectively; by means of an operation using epipolar geometry, determining the correspondence between the barycentric points on said first image and the barycentric points on the second image; on the basis of the coordinates of said barycentric points in the first and second image, determining by triangulation the coordinates of said barycentric points in a three-dimensional reference system; determining, in said three-dimensional reference system, the equation of an approximate plane in which said markers lie in space, said plane being approximately parallel to the plane in which the wheel lies; determining the camber and toe angles of said wheel on the basis of the equation of said plane in which the markers lie and of the equation of reference planes with respect to which the motor vehicle takes a known position. 2. Method as claimed in claim 1, further comprising the step of determining the position of said motor vehicle with respect to the reference planes on the basis of the position of the acquisition devices with respect to a single reference system. 3. Method as claimed in claim 2, wherein said single reference system is centered on one of said acquisition devices. 4. Method as claimed in claim 3, wherein said reference planes are planes of a Cartesian reference system, having a specific position with respect to a supporting structure of the motor vehicle. 5. Method as claimed in claim 2, wherein said reference planes are planes of a Cartesian reference system, having a specific position with respect to a supporting structure of the motor vehicle. 6. Method as claimed in claim 1, wherein said reference planes are planes of a Cartesian reference system, having a specific position with respect to a supporting structure of the motor vehicle. 7. Method as claimed in claim 6, wherein said supporting structure is a lift on which said motor vehicle is disposed. 8. Method as claimed in claim 7, wherein a first of said reference planes coincides approximately with a supporting surface of the motor vehicle and a second of said reference planes is substantially orthogonal to said first reference plane and approximately parallel to the center line of the motor vehicle. 9. Method as claimed in claim 6, wherein a first of said reference planes coincides approximately with a supporting surface of the motor vehicle and a second of said reference planes is substantially orthogonal to said first reference plane and approximately parallel to the center line of the motor vehicle. 10. Method as claimed in claim 9, wherein said first reference plane is approximately horizontal. 11. Method as claimed in claim 8, further comprising the step of determining the position in space of the centers of the wheels of the motor vehicle; on the basis of this position, calculating the angle of inclination between the center line of the motor vehicle and said second reference plane; and on the basis of said angle of inclination, correcting the toe angle calculated on the basis of the images acquired by said acquisition devices. 12. Method as claimed in claim 1, further comprising the step of determining the reciprocal position between said acquisition devices and a supporting structure of the motor vehicle through calibration of said acquisition devices using targets integral with said structure and in a known position with respect to said reference planes. 13. Method as claimed in claim 12, further comprising the step of arranging at least one of said targets on each side of said supporting structure. 14. Method as claimed in claim 12, wherein the positions of each of said acquisition devices with respect to an absolute reference system centered on one of said acquisition devices are determined through said targets and the known position of said targets with respect to the supporting structure. 15. Method as claimed in claim 1, further comprising the step of arranging at least one pair of said first and second acquisition devices in known and fixed reciprocal positions on a common support. 16. Method as claimed in claim 15, wherein the acquisition devices for each wheel are placed on said common support. 17. Method as claimed in claim 15, wherein on each side of the motor vehicle there are arranged four of said first and second acquisition devices, constrained to one another in fixed positions through said common support. 18. Method as claimed in claim 1, wherein said acquisition devices acquire images in a range of invisible radiations, said markers reflecting a radiation in said range of invisible radiations. 19. Method as claimed in claim 18, wherein said range of radiations is a UV or IR range. 20. Method as claimed in claim 1, wherein said acquisition devices are video cameras. 21. Method as claimed in claim 1, further comprising a single and stereo calibration operation of said two acquisition devices associated with each wheel, to determine the characteristics of the acquisition devices and their reciprocal position. 22. Method as claimed in claim 21, wherein said single and stereo calibration is performed by acquiring and processing a plurality of images of a target movable with respect to the acquisition devices. 23. Method as claimed in claim 1, further comprising the step of providing a supporting structure of the motor vehicle; and wherein, once the acquisition devices have been positioned with respect to said structure, a calibration operation is performed to determine the position of the acquisition devices with respect to the supporting structure and the position of the acquisition devices with respect to an absolute reference system, integral with one of said acquisition devices. 24. Method as claimed in claim 23, wherein, having defined the reciprocal position of the acquisition devices of said first and second acquisition devices associated with each wheel of the motor vehicle, the relative position of said first and second acquisition devices in relation to the supporting structure is performed by said calibration operation using one or more targets integral with the supporting structure. 25. Method as claimed in claim 1, further comprising the steps of: identifying the coordinates of said barycentric points corresponding to the markers on the wheel on said first image; determining on said second image the epipolar lines corresponding to the barycentric points on the first image; determining the coordinates of said barycentric points on the second image identifying, for each epipolar line the barycentric point closest thereto and assuming said closest barycentric point as the barycentric point corresponding to the barycentric point on the first image with which the relative epipolar line is associated. 26. Method as claimed in claim 25, further comprising the steps of: identifying the coordinates of said barycentric points corresponding to the markers on the wheel on the second of said two images; determining on said first image the epipolar lines corresponding to the barycentric points on the second image; determining the coordinates of said barycentric points on the first image identifying, for each epipolar line the barycentric point closest thereto and assuming said closest barycentric point as the barycentric point corresponding to the barycentric point on the second image with which the relative epipolar line is associated; discarding the barycentric points for which a biunique correspondence of coordinates has not been identified. 27. Method according to claim 1, wherein said markers are applied along a line approximately circumferential and approximately coaxial with the wheel. 28. A device for measuring the angles of inclination of the wheels of a motor vehicle, comprising: a motor vehicle supporting structure; for each wheel of the motor vehicle, a pair of image acquisition devices; a control and processing unit programmed to perform a measurement method as claimed in claim 1. 29. Device as claimed in claim 28, wherein on said supporting structure of the motor vehicle there are disposed at least two targets, one on each side. 30. Device as claimed in claim 29, wherein said targets and said acquisition devices are arranged such that each pair of said acquisition devices can simultaneously see a wheel of the vehicle and a target. 31. Device as claimed in claim 28, wherein the pair of acquisition devices associated with each wheel of the motor vehicle are mounted on a common support. 32. Device as claimed in claim 31, wherein said common supports are fixed. 33. Device as claimed in claim 31, wherein at least some of said common supports are movable. 34. Device as claimed in claim 33, further comprising two of said common supports, one for each side of the motor vehicle, said supports both being movable and each one comprising two said pairs of said acquisition devices. 35. Device as claimed in claim 33, further comprising four of said common supports, each said common support being provided with a pair of said acquisition devices. 36. Device as claimed in claim 35, wherein said four common supports are movable. 37. Device as claimed in claim 35, wherein two of said common supports are fixed and two of said common supports are movable. 38. Device as claimed in claim 31, wherein at least one of said common supports is movable on a guide. 39. Device as claimed in claim 38, further comprising at least one transducer to determine the position of said at least one movable common support. 40. Device as claimed in claim 28, wherein two said pairs of said acquisition devices associated with two wheels on a same side of the motor vehicle are mounted on a single common support. 41. Device as claimed in claim 28, wherein said acquisition device acquires images in a range of invisible frequencies. 42. Device as claimed in claim 41, wherein said acquisition devices acquire UV or IR images. 43. Device as claimed in claim 28, wherein said acquisition devices are video cameras. 44. Device as claimed in claim 28, further comprising UV or IR light means. 45. A method for measuring the angles of inclination of the wheels of a motor vehicle, comprising the steps of: applying a plurality of markers to the wheels of the motor vehicle; providing, at each wheel whose characteristic angles must be acquired, a first image acquisition device and a second image acquisition device, said two image acquisition devices having different inclinations and positions with respect to said wheel; for each of said wheels, acquiring at least a first image and a second image of said wheel with the relative markers by means of said first and second image acquisition device respectively; identifying the coordinates of said barycentric points corresponding to the markers on the wheel on said first image; determining on said second image the epipolar lines corresponding to the barycentric points on the first image; determining the coordinates of said barycentric points on the second image identifying, for each epipolar line, the barycentric point closest thereto and assuming said closest barycentric point as the barycentric point corresponding to the barycentric point on the first image with which the relative epipolar line is associated; on the basis of the coordinates of said barycentric points in the first and second image, determining by triangulation the coordinates of said barycentric points in a three-dimensional reference system; determining, in said three-dimensional reference system, the equation of an approximate plane in which said markers lie in space, said plane being approximately parallel to the plane in which the wheel lies; determining the camber and toe angles of said wheel on the basis of the equation of said plane in which the markers lie and of the equation of reference planes with respect to which the motor vehicle takes a known position. 46. A method for measuring the angles of inclination of the wheels of a motor vehicle, comprising the steps of: applying a plurality of markers to the wheels of the motor vehicle; providing, at each wheel whose characteristic angles must be acquired, a first image acquisition device and a second image acquisition device, said two image acquisition devices having different inclinations and positions with respect to said wheel; for each of said wheels, acquiring at least a first image and a second image of said wheel with the relative markers by means of said first and second image acquisition device respectively; identifying the coordinates of said barycentric points corresponding to the markers on the wheel on said first image; determining on said second image the epipolar lines corresponding to the barycentric points on the first image; determining the coordinates of said barycentric points on the second image identifying, for each epipolar line, the barycentric point closest thereto and assuming said closest barycentric point as the barycentric point corresponding to the barycentric point on the first image with which the relative epipolar line is associated; identifying the coordinates of said barycentric points corresponding to the markers on the wheel on the second of said two images; determining on said first image the epipolar lines corresponding to the barycentric points on the second image; determining the coordinates of said barycentric points on the first image identifying, for each epipolar line the barycentric point closest thereto and assuming said closest barycentric point as the barycentric point corresponding to the barycentric point on the second image with which the relative epipolar line is associated; discarding the barycentric points for which a biunique correspondence of coordinates has not been identified; on the basis of the coordinates of said barycentric points in the first and second image, determining by triangulation the coordinates of said barycentric points in a three-dimensional reference system; determining, in said three-dimensional reference system, the equation of an approximate plane in which said markers lie in space, said plane being approximately parallel to the plane in which the wheel lies; determining the camber and toe angles of said wheel on the basis of the equation of said plane in which the markers lie and of the equation of reference planes with respect to which the motor vehicle takes a known position.