Sensor for vehicle alignment system and apparatus using same

• US 5,489,983 A
• Filed: 04/27/1995
• Issued: 02/06/1996
• Est. Priority Date: 12/02/1993
• Status: Expired due to Fees

• Current Assignee: Hunter Engineering Company
• Original Assignee: Hunter Engineering Company
• Inventors: McClenahan, James W., Stieff, Michael T., Burns, Leigh R. Jr., January, Daniel B.
• Primary Examiner(s): Buczinski, Stephen C.
• Application Number:
  US08/429,680
• Time in Patent Office: 285 Days
• Field of Search: 33/203.15, 33/203.18, 33/288, 356/139.09, 356/141.3, 356/155, 356/152.1, 250/214 B
• 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. A system for measuring angular relationships of wheels of a vehicle, comprising:

a first unit for attachment to a first wheel of a vehicle;

a second unit for attachment to a second wheel of a vehicle;

a radiation source mounted on the first unit for providing a radiation signal;

an image detector mounted on the second unit for receiving an image from the radiation source and for producing an output in response to the radiation signal;

a radiation detector disposed in the path of the radiation from the radiation source for detecting the presence of the radiation signal;

a controller operatively connected to the radiation detector for determining therefrom the presence of the radiation signal, said controller being responsive to the presence of the radiation signal to activate the image detector to receive the image from the radiation source, said controller being operatively connected to the image detector for controlling the image detector, for receiving the image detector output, and for determining an alignment angle of a wheel of the vehicle therefrom.

2. The system for measuring angular relationships of wheels of a vehicle as set forth in claim 1 wherein the radiation source includes a driver for driving the source to provide a fixed cycle of radiation output.

3. The system for measuring angular relationships of wheels of a vehicle as set forth in claim 2 wherein the driver includes means for driving the source such that the fixed cycle includes a modulated start pulse of radiation, the controller being responsive to the detection of said start pulse by the radiation detector to activate the image detector.

4. The system for measuring angular relationships of wheels of a vehicle as set forth in claim 3 wherein the controller is under programmed control to activate the image detector for a trial exposure period upon receipt of a start pulse from a first cycle of the radiation source output, said controller being responsive to the image detector output during the trial exposure period to determine an optimum exposure time for the image detector based upon the image detector output during the trial exposure period.

5. The system for measuring angular relationships of wheels of a vehicle as set forth in claim 4 wherein the controller is responsive to receipt of a start pulse from a second cycle of the radiation source output after the first cycle to activate the image detector for the optimum exposure time calculated by the controller from the output during the trial exposure period.

6. The system for measuring angular relationships of wheels of a vehicle as set forth in claim 2 wherein the driver includes means for driving the radiation source such that the fixed cycle of radiation output includes an exposure pulse of radiation.

7. The system for measuring angular relationships of wheels of a vehicle as set forth in claim 6 wherein the exposure pulse of radiation is rectangular.

8. The system for measuring angular relationships of wheels of a vehicle as set forth in claim 6 wherein the controller is under programmed control to calculate an optimum exposure time for the image detector, said exposure pulse being at least as long as the optimum exposure time.

9. The system for measuring angular relationships of wheels of a vehicle as set forth in claim 6 wherein the driver includes means for driving the radiation source such that the fixed cycle of radiation output includes a dark period at least as long as the exposure pulse.

10. The system for measuring angular relationships of wheels of a vehicle as set forth in claim 9 wherein the controller is responsive to the output of the image detector during the exposure pulse and during the dark period to cancel background noise from the output of the image detector.

11. The system for measuring angular relationships of wheels of a vehicle as set forth in claim 10 wherein the controller cancels background noise by subtracting a portion of the dark period output of the image detector from a portion of the exposure pulse output.

12. The system for measuring angular relationships of wheels of a vehicle as set forth in claim 2 wherein the driver includes means for driving the radiation source such that the fixed cycle of radiation output includes a modulated stop pulse of radiation.

13. The system for measuring angular relationships of wheels of a vehicle as set forth in claim 12 wherein the driver further includes means for driving the source such that the fixed cycle includes a modulated start pulse of radiation, the modulated stop pulse differing from the modulated start pulse.

14. The system for measuring angular relationships of wheels of a vehicle as set forth in claim 1 wherein the radiation source output is totally independent of the controller of the image detector.

15. The system for measuring angular relationships of wheels of a vehicle as set forth in claim 14 wherein the radiation source is free-wheeling.

16. The system for measuring angular relationships of wheels of a vehicle as set forth in claim 1 wherein the controller is responsive to the radiation detector output to detect an over-exposure condition.

17. The system for measuring angular relationships of wheels of a vehicle as set forth in claim 1 wherein the controller is responsive to the radiation detector output to detect an under-exposure condition.

18. The system for measuring angular relationships of wheels of a vehicle as set forth in claim 1 wherein the controller is responsive to the radiation detector output to detect a high background signal condition.

19. A method of measuring angular relationships of wheels of a vehicle, comprising:

providing a radiation signal from a radiation source, said signal traveling generally from a first wheel to a second wheel of a vehicle;

receiving an image from the radiation source in an image detector and producing an output in response to the radiation signal;

detecting the presence of the radiation signal by means of a radiation detector independently of receiving the radiation source image;

activating the image detector to receive the image from the radiation source in response to the detection of the radiation signal by the radiation detector; and

determining an alignment angle of a wheel of the vehicle from the output of the image detector.

20. The method of measuring angular relationships of wheels of a vehicle as set forth in claim 19 wherein the radiation signal has a fixed cycle of radiation output.

21. The method of measuring angular relationships of wheels of a vehicle as set forth in claim 20 wherein the fixed cycle includes a modulated start pulse of radiation, the image detector being activated in response to the detection of said start pulse by the radiation detector.

22. The method of measuring angular relationships of wheels of a vehicle as set forth in claim 21 including the step of activating the image detector for a trial exposure period upon receipt of a start pulse from a first cycle of the radiation source output, and determining an optimum exposure time for the image detector based upon the image detector output during the trial exposure period.

23. The method of measuring angular relationships of wheels of a vehicle as set forth in claim 22 including the step of activating the image detector for said determined optimum exposure time during at least one subsequent cycle of the radiation output.

24. The method of measuring angular relationships of wheels of a vehicle as set forth in claim 20 wherein the fixed cycle of radiation output includes an exposure pulse of radiation.

25. The method of measuring angular relationships of wheels of a vehicle as set forth in claim 24 wherein the exposure pulse of radiation is rectangular.

26. The method of measuring angular relationships of wheels of a vehicle as set forth in claim 24 further including determining an optimum exposure time for the image detector, said exposure pulse being at least as long as the optimum exposure time.

27. The method of measuring angular relationships of wheels of a vehicle as set forth in claim 24 wherein the fixed cycle of radiation output includes a dark period at least as long as the exposure pulse.

28. The method of measuring angular relationships of wheels of a vehicle as set forth in claim 27 further including using the output of the image detector during the exposure pulse and during the dark period to cancel background noise from the output of the image detector.

29. The method of measuring angular relationships of wheels of a vehicle as set forth in claim 28 wherein the background noise is canceled by subtracting a portion of the dark period output of the image detector from a portion of the exposure pulse output.

30. The method of measuring angular relationships of wheels of a vehicle as set forth in claim 20 wherein the fixed cycle of radiation output includes a modulated stop pulse of radiation.

31. The method of measuring angular relationships of wheels of a vehicle as set forth in claim 30 wherein the fixed cycle includes a modulated start pulse of radiation, the modulated stop pulse differing from the modulated start pulse.

32. The method of measuring angular relationships of wheels of a vehicle as set forth in claim 19 wherein the radiation source output is totally independent of the image detector.

33. The method of measuring angular relationships of wheels of a vehicle as set forth in claim 32 wherein the radiation source is free-wheeling.

34. The method of measuring angular relationships of wheels of a vehicle as set forth in claim 19 including the step of detecting an over-exposure condition independently of the image detector.

35. The method of measuring angular relationships of wheels of a vehicle as set forth in claim 19 including the step of detecting an under-exposure condition independently of the image detector.

36. The method of measuring angular relationships of wheels of a vehicle as set forth in claim 19 including the step of detecting a high background signal condition independently of the image detector.