Sensors for vehicle alignment system and apparatus using same

• US 5,488,471 A
• Filed: 12/02/1993
• Issued: 01/30/1996
• Est. Priority Date: 12/02/1993
• Status: Expired due to Term

• Current Assignee: Hunter Engineering Company
• Original Assignee: Hunter Engineering Company
• Inventors: Stieff, Michael T., McClenahan, James W., Burns, Leigh R. Jr., January, Daniel B.
• Primary Examiner(s): Buczinski, Stephen C.
• Application Number:
  US08/162,452
• Time in Patent Office: 789 Days
• Field of Search: 356/139.09, 356/141.3, 356/155, 356/141.1, 356/1, 356/152.1, 356/4, 356/3.10, 356/3.11, 356/3.12, 356/4.03, 33/288, 33/203.15, 33/203.18
• US Class Current: 356/139.09
• CPC Class Codes: G01B 11/2755 using photoelectric detection means
• CPC Class Codes: G01B 2210/16 Active or passive device attached to the chassis of a vehicle
• CPC Class Codes: G01B 2210/283 Beam projectors and related sensors

Abstract

A system for measuring angular relationships of wheels of a vehicle includes a radiation source mounted with respect to a first wheel for providing a radiation signal, an image detector having an active array of pixels mounted with respect to a second wheel for receiving an image from the radiation source and for producing an output in response to the radiation signal, and a radiation detector disposed in the path of the radiation from the radiation source for detecting the presence of the radiation signal. A controller is responsive to the presence of the radiation signal to activate the image detector to receive the image from the radiation source and determine an alignment angle of a wheel of the vehicle from the output of the image detector. A mask is mounted between the radiation source and the detector for defining an image of the radiation source upon the detector, the mask preferably having at least three slits therein the system also uses radiation signals and the active pixel array detector to electronically determine wheel base and/or track width and corrects alignment characteristic values for errors which are affected by wheelbase. The system also uses such radiation signals and detectors to electronically determine ride height and/or wheel offset distances.

Claims

1. An improved vehicle wheel alignment system comprising:

a first sensor unit adapted to be removably mounted to a front wheel of a vehicle whose alignment is to be tested;

a second sensor unit adapted to be removably mounted to a rear wheel of the vehicle under test such that the front wheel and the rear wheel are disposed on the same side of the vehicle;

said first and second sensor units obtaining wheel alignment data for their respective wheels;

determining means for determining wheel alignment characteristics of said front and rear wheels from the wheel alignment data from the first and second sensor units;

at least one of the first and second sensor units having an active pixel array detector, said active pixel array detector providing the wheel alignment data for said sensor unit;

said first and second sensor units including means, including at least one radiation source, for projecting at least two spatially separated images upon the active pixel array detector, the spatial separation of said two images being a function of the wheelbase of the vehicle under test;

said determining means being responsive to the active pixel array detector to determine the wheelbase of the vehicle under test from the spatial separation of the images on the active pixel array detector.

2. The vehicle wheel alignment system as set forth in claim 1 wherein the active pixel array detector is a CCD detector.

3. The vehicle wheel alignment system as set Forth in claim 1 wherein the projecting means includes a mask disposed between the radiation source and the active pixel array detector, said mask having a pair of slits formed therein.

4. The vehicle wheel alignment system as set forth in claim 3 wherein the pair of slits in the mask are disposed a predetermined distance from each other.

5. The vehicle wheel alignment system as set forth in claim 3 wherein the mask is disposed a predetermined distance From the active pixel array detector.

6. The vehicle wheel alignment system as set forth in claim 1 wherein the projecting means includes a pair of radiation sources and a mask disposed between said pair of radiation sources and the active pixel array detector, said mask having at least one slit therein.

7. The vehicle wheel alignment system as set forth in claim 1 further including third and fourth sensor units adapted to be removably mounted to front and rear wheels on the opposite side of the vehicle under test from said first and second sensor units, at least one of the third and fourth sensor units having an active pixel array detector for providing wheel alignment data and wheelbase data, said determining means being responsive to the third and fourth sensor units to determine the wheelbase of the vehicle on said opposite side of the vehicle and to compare the determined wheelbases for the two sides of the vehicle.

8. A wheelbase determining method comprising:

removably securing at least a first radiation source to a first wheel of a vehicle;

removably securing an active pixel array detector to a second wheel of the vehicle, the distance between the first radiation source and the detector defining a wheelbase of the vehicle;

projecting a pair of images upon the active pixel array detector, said images being spatially separated a distance which is a function of said wheelbase, at least one of said images originating at said first radiation source;

electronically determining the spatial separation of the images on said detector and calculating therefrom said wheelbase.

9. The wheelbase determining method as set forth in claim 8 including the step of interposing an image defining means between the radiation source and the detector, said image defining means in combination with the radiation source generating the pair of images.

10. The wheelbase determining method as set forth in claim 8 wherein the steps of the method are performed for each side of the vehicle and the wheelbases determined for each side of the vehicle are compared.

11. The wheelbase determining method as set forth in claim 8 further including the step of providing a second radiation source in fixed geometrical relationship to the first radiation source, and projecting radiation from said second radiation source toward the detector, one of the images on the detector originating from the first radiation source and the other image on the detector originating from the second radiation source.

12. An improved vehicle wheel alignment system comprising:

a first sensor unit adapted to be removably mounted to a first wheel of a vehicle whose alignment is to be tested;

a second sensor unit adapted to be removably mounted to a second wheel of the vehicle under test;

said first and second sensor units obtaining wheel alignment data for their respective wheels;

determining means for determining wheel alignment characteristics of said first and second wheels from the wheel alignment data from the first and second sensor units;

at least one of the first and second sensor units having an active pixel array detector, said active pixel array detector providing the wheel alignment data for said sensor unit;

said first and second sensor units including means, including at least one radiation source, for projecting at least two spatially separated images upon the active pixel array detector, the spatial separation of said two images being a function of the distance between the first and second wheels;

said determining means being responsive to the active pixel array detector to determine the distance between the first and second wheels from the spatial separation of the images on the active pixel array detector.

13. The vehicle wheel alignment system as set forth in claim 12 wherein the projecting means includes a mask disposed between the radiation source and the active pixel array detector, said mask having a pair of slits formed therein.

14. The vehicle wheel alignment system as set forth in claim 13 wherein the pair of slits in the mask are disposed a predetermined distance from each other.

15. The vehicle wheel alignment system as set forth in claim 13 wherein the mask is disposed a predetermined distance from the active pixel array detector.

16. The vehicle wheel alignment system as set forth in claim 12 wherein the projecting means includes a pair of radiation sources and a mask disposed between said pair of radiation sources and the active pixel array detector, said mask having at least one slit therein.

17. A method of electronically determining distance between a pair of wheels on a vehicle comprising:

removably securing at least a first radiation source to a first wheel of a vehicle;

removably securing an active pixel array detector to a second wheel of the vehicle;

projecting a pair of images upon the active pixel array detector, said images being spatially separated a distance which is a function of the distance between the first and second wheels, at least one of said images originating at said first radiation source;

electronically determining the spatial separation of the images on said detector and calculating therefrom said distance between the first and second wheels.

18. The method of electronically determining distance between a pair of wheels on a vehicle as set forth in claim 17 further including the step of interposing a mask between the radiation source and the detector, said mask having a pair of slits which in combination with the radiation source generate the pair of images.

19. The method of electronically determining distance between a pair of wheels on a vehicle as set forth in claim 17 further including the step of providing a second radiation source in fixed geometrical relationship to the first radiation source, and projecting radiation from said second radiation source toward the detector, one of the images on the detector originating from the first radiation source and the other image on the detector originating from the second radiation source.

20. A method of correcting vehicle wheel alignment angles comprising:

removably securing at least a first radiation source to a first wheel of a vehicle;

removably securing an active pixel array detector to a second wheel of the vehicle, the detector having an output representative of the radiation from the radiation source falling thereon, the distance between the first radiation source and the detector defining a wheelbase of the vehicle;

projecting a pair of images upon the active pixel array detector, said images being spatially separated a distance which is a function of said wheelbase, at least one of said images originating at said first radiation source;

electronically determining the spatial separation of the images on said detector and calculating therefrom said wheelbase;

electronically determining from the output of the detector at least one alignment characteristic, the value of said alignment characteristic potentially including an error which depends at least in part on the wheelbase of the vehicle;

electronically correcting said value of the alignment characteristic by using the electronically determined wheelbase.

21. The method of correcting vehicle wheel alignment angles as set forth in claim 20 wherein the wheelbase dependent alignment characteristic is toe, the error being a function of both wheelbase and camber of one of the wheels of the vehicle.

22. A method of correcting vehicle wheel alignment angles comprising:

removably securing at least a first radiation source to a first wheel of a vehicle in a first predetermined position with respect to said first wheel;

removably securing an active pixel array detector to a second wheel of the vehicle in a second predetermined position with respect to the second wheel, the detector having an output representative of the radiation from the radiation source falling thereon, the distance between the first radiation source and the detector defining a wheelbase of the vehicle;

at least one of the first and second predetermined positions being offset from the axis of rotation of its respective wheel;

projecting a pair of images upon the active pixel array detector, said images being spatially separated a distance which is a function of said wheelbase, at least one of said images originating at said first radiation source;

electronically determining the spatial separation of the images on said detector and calculating therefrom said wheelbase;

electronically determining from the output of the detector at least one alignment characteristic;

determining any angular variation of the detector from a plane normal to the axis of the second wheel, said normal plane containing the radiation source;

electronically correcting said determined alignment characteristic taking into account the electronically determined wheelbase and the angular variation of the detector from said normal plane.

23. The method of correcting vehicle wheel alignment angles as set forth in claim 22 wherein the detector is mounted to the second wheel in such a way that camber of the second wheel affects the measured toe angle of the first wheel.

24. The method of correcting vehicle wheel alignment angles as set forth in claim 23 wherein the determined value of toe is corrected by an amount equal to the vertical offset of the detector from the axis of the second wheel times the sine of the camber of the second wheel, divided by the electronically determined wheelbase of the vehicle.