Portable coordinate measurement machine

• US 20040040166A1
• Filed: 02/13/2003
• Published: 03/04/2004
• Est. Priority Date: 02/14/2002
• Status: Active Grant

• Current Assignee: Faro Technologies Incorporated
• Original Assignee: Faro Technologies Incorporated
• Inventors: Hasloecher, Kenneth J., Raab, Simon, Barber, Marc, Sajedi, Seyed Ali
• Granted Patent: US 6,935,036 B2
• Time in Patent Office: Days
• US Class Current: 33/503
• CPC Class Codes: B23Q 35/04 using a feeler or the like travelling along the outline of the pattern, model or drawing; Feelers, patterns, or models therefor
• CPC Class Codes: B25J 17/025 mounted in series
• CPC Class Codes: B25J 19/0016 using springs
• CPC Class Codes: B25J 19/0091 Shock absorbers in general F16F
• CPC Class Codes: B25J 9/0012 making use of synthetic construction materials, e.g. plastics, composites
• CPC Class Codes: B25J 9/023 Cartesian coordinate type
• CPC Class Codes: B25J 9/06 characterised by multi-articulated arms
• CPC Class Codes: B25J 9/1602 characterised by the control system, structure, architecture
• CPC Class Codes: G01B 11/005 coordinate measuring machines
• CPC Class Codes: G01B 11/03 by measuring coordinates of points
• CPC Class Codes: G01B 11/25 by projecting a pattern, e.g. one or more lines, moiré fringes on the object G01B11/255 takes precedence ; image analysis for depth or shape recovery G06T7/50
• CPC Class Codes: G01B 21/045 Correction of measurements G01B9/02055 takes precedence
• CPC Class Codes: G01B 5/004 for measuring coordinates of points
• CPC Class Codes: G01B 5/008 using coordinate measuring machines
• CPC Class Codes: G06T 7/521 from laser ranging, e.g. using interferometry; from the projection of structured light
• CPC Class Codes: Y10S 33/01 Magnetic

Abstract

A portable coordinate measurement machine comprises an articulated arm having jointed arm segments. The arm includes modular bearing/encoder cartridges which are attached to each other at predetermined angles using dual socket joints. Each cartridge contains at least one, and preferably two preloaded bearing assemblies and an encoder, preferably optical encoder, all assembled in a cylindrical housing.

Claims

1. A portable coordinate measurement machine (CMM) for measuring the position of an object in a selected volume, comprising:

a manually positionable articulated arm having opposed first and second ends, said arm including a plurality of joints, at least one of said joints including at least one bearing/transducer cartridge;

a measurement probe attached to a first end of said articulated arm;

an electronic circuit which receives the position signals from transducers in said arm and provides a digital coordinate corresponding to the position of the probe in a selected volume; and

wherein said cartridge further comprises;

a rotatable shaft;

at least one bearing on said shaft;

a periodic pattern of a measurable characteristic;

at least one read head spaced from and in communication with said pattern;

a housing surrounding said at least one bearing, pattern, read head and at least a portion of said shaft so as to define a discrete component, said housing having a pair of ends with an outer surface therebetween, said outer surface defining a structural element of said at least one joint; and

said pattern and said read head being associated with said shaft and housing such that said pattern and read head are rotatable with respect to each other.

2. The CMM of claim 1 wherein:

said housing is a cylindrical housing.

3. The CMM of claim 1 wherein:

said at least one bearing comprises at least one preloaded bearing.

4. The CMM of claim 3 wherein said at least one preloaded bearing comprises:

a first bearing;

a second bearing;

an inner spacer sleeve between said first and second bearings;

an outer spacer sleeve between said first and second bearings;

said inner and outer spacer sleeves having different predetermined lengths; and

said inner and outer spacer sleeves being compressed against said first and second bearings to define a predetermined preload.

5. The CMM of claim 1 wherein:

said at least one bearing is sealed.

6. The CMM of claim 1 including at least two read heads.

7. The CMM of claim 6 wherein said two read heads are positioned 180 degrees apart.

8. The CMM of claim 1 including at least three read heads.

9. The CMM of claim 8 wherein said three read heads are 120 degrees apart.

10. The CMM of claim 1 including at least four read heads.

11. The CMM of claim 10 wherein said four read heads are 90 degrees apart.

12. The CMM of claim 1 wherein:

said pattern comprises an optical fringe pattern; and

said at least one read head comprises an optical read head.

13. The CMM of claim 12 wherein:

said optical fringe pattern is disposed on an optical encoder disk.

14. The CMM of claim 12 wherein said optical communication comprises:

said read head detecting the interference between diffraction orders to produce sinusoidal signals from said read head inserted in said fringe pattern, said sinusoidal signals being electronically interpolated to detect displacement.

15. The CMM of claim 14 wherein each said read head comprises a laser, a collimator, and an aperture, whereby said laser emits a beam which is collimated by said collimator, and then sized by the aperture, said fringe pattern includes a grating that diffracts light into discrete orders.

16. The CMM of claim 15 wherein each said read head further comprises a photodetector array, said photodetector array producing four channels of nearly pure sinusoidal output when there is relative motion between said fringe pattern and said read head.

17. The CMM of claim 1 including a plurality of read heads, said read heads causing cancellation effects that can be averaged.

18. The CMM of claim 1 wherein:

said pattern of a measurable characteristic is at least one of the characteristics selected from the group consisting of reflectivity, opacity, magnetic field, capacitance, inductance and surface roughness.

19. The CMM of claim 1 including:

a slip ring assembly in said cartridge.

20. The CMM of claim 19 wherein said shaft includes an axial opening.

21. The CMM of claim 1 wherein said shaft includes a flange extending outwardly from one end thereof, said flange defining an annulus and wherein:

one of said ends of said housing is received in said annulus.

22. The CMM of claim 21 wherein the other of said ends of said housing has an open end, and including:

at least one cap covering said open end.

23. The CMM of claim 1 wherein said at least one of said joints has infinite rotation.

24. The CMM of claim 1 wherein:

at least two of said joints each include at least one cartridge, said cartridges being attached to each other at predetermined angles.

25. The CMM of claim 24 wherein said cartridges are attached to each other using socket joints.

26. The CMM of claim 25 wherein said socket joint includes:

a first extension having a socket therein;

at least one second extension having a socket therein, said first and second extensions being attached to each other at an angle and said sockets each being sized and configured to each receive a cartridge.

27. The CMM of claim 26 wherein:

at least one of said cartridges is captured between a pair of sockets from a pair of spaced socket joints.

28. The CMM of claim 27 wherein:

said captured cartridge is adhesively attached to each of said pair of sockets.

29. The CMM of claim 26 including:

threading in at least one of said sockets.

30. The CMM of claim 29 including:

a threaded component extending outwardly from at least one of said cartridges, said threaded component threadably mating with threading in said socket.

31. The CMM of claim 1 including:

an extension tube over said housing.

32. The CMM of claim 31 wherein:

said extension tube comprises a fiber reinforced composite.

33. The CMM of claim 25 wherein:

said cartridges are adhesively attached to said socket joints.

34. The CMM of claim 1 wherein:

at least two of said joints are threadibly interconnected to each other.

35. The CMM of claim 1 wherein:

at least two of said joints are fastened to each other using threadable fasteners.

36. The CMM of claim 1 wherein:

said at least two of said joints include complimentary tapered portions which are fastened together with said fasteners.

37. The CMM of claim 1 wherein said joints comprise long joints for swiveling motion and short joints for hinged motion.

38. The CMM of claim 32 including three joint pairs, each joint pair comprising a long joint and a short joint.

39. The CMM of claim 38 wherein said long joint is about 90 degrees to said short joint in each joint pair.

40. The CMM of claim 39 including a seventh joint in said measurement probe.

41. The CMM of claim 1 wherein said joints are arranged in the joint configurations selected from the group consisting of 2-2-2, 2-1-2, 2-2-3, and 2-1-3.

42. The CMM of claim 1 including:

an electronic identification chip associated with said cartridge for uniquely identifying said cartridge.

43. The CMM of claim 1 wherein:

said pattern is rotatable with said shaft; and

said read head is stationary with respect to said shaft.

44. The CMM of claim 43 wherein:

said pattern is attached directly to said shaft.

45. The CMM of claim 1 wherein:

said read head is rotatable with said shaft; and

said pattern is stationary with respect to said shaft.

46. A bearing/transducer cartridge, comprising:

a rotatable shaft;

at least one bearing on said shaft;

a periodic pattern of a measurable characteristic;

at least one read head spaced from and in communication with said pattern;

a housing surrounding said at least one bearing, pattern, read head and at least a portion of said shaft so as to define a discrete component, said housing having a pair of ends with an outer surface therebetween, said outer surface defining a structural element of said at least one joint; and

said pattern and said read head being associated with said shaft and housing such that said pattern and read head are rotatable with respect to each other.

47. The cartridge of claim 46 wherein:

said housing is a cylindrical housing.

48. The cartridge of claim 46 wherein:

said at least one bearing comprises at least one preloaded bearing.

49. The cartridge of claim 48 wherein said at least one preloaded bearing comprises:

a first bearing;

a second bearing;

an inner spacer sleeve between said first and second bearings;

an outer spacer sleeve between said first and second bearings;

said inner and outer spacer sleeves having different predetermined lengths; and

said inner and outer spacer sleeves being compressed against said first and second bearings to define a predetermined preload.

50. The cartridge of claim 46 wherein:

said at least one bearing is sealed.

51. The cartridge of claim 46 including at least two read heads.

52. The cartridge of claim 51 wherein said two read heads are positioned 180 degrees apart.

53. The cartridge of claim 46 including at least three read heads.

54. The cartridge of claim 53 wherein said three read heads are 120 degrees apart.

55. The cartridge of claim 46 including at least four read heads.

56. The cartridge of claim 55 wherein said four read heads are 90 degrees apart.

57. The cartridge of claim 46 wherein:

said pattern comprises an optical fringe pattern; and

said at least one read head comprises an optical read head.

58. The cartridge of claim 57 wherein:

said optical fringe pattern is disposed on an optical encoder disk.

59. The cartridge of claim 57 wherein said optical communication comprises:

said read head detecting the interference between diffraction orders to produce sinusoidal signals from said read head inserted in said fringe pattern, said sinusoidal signals being electronically interpolated to detect displacement.

60. The cartridge of claim 59 wherein each said read head comprises a laser, a collimator, and an aperture, whereby said laser emits a beam which is collimated by said collimator, and then sized by the aperture, said fringe pattern includes a grating that diffracts light into discrete orders.

61. The cartridge of claim 60 wherein each said read head further comprises a photodetector array, said photodetector array producing four channels of nearly pure sinusoidal output when there is relative motion between said fringe pattern and said read head.

62. The cartridge of claim 46 including a plurality of read heads, said read heads causing cancellation effects that can be averaged.

63. The cartridge of claim 46 wherein:

said pattern of a measurable characteristic is at least one of the characteristics selected from the group consisting of reflectivity, opacity, magnetic field, capacitance, inductance and surface roughness.

64. The cartridge of claim 46 including:

a slip ring assembly in said cartridge.

65. The cartridge of claim 64 wherein said shaft includes an axial opening therethrough and wherein said slip ring assembly is positioned in said axial opening.

66. The cartridge of claim 46 wherein said shaft includes a flange extending outwardly from one end thereof, said flange defining an annulus and wherein:

one of said ends of said housing is received in said annulus.

67. The cartridge of claim 66 wherein the other of said ends of said housing has an open end, and including:

at least one cap covering said open end.

68. The cartridge of claim 46 including:

an electronic identification chip associated with said cartridge for uniquely identifying said cartridge.

69. The cartridge of claim 46 wherein:

said pattern is rotatable with said shaft; and

said read head is stationary with respect to said shaft.

70. The cartridge of claim 69 wherein:

said pattern is attached directly to said shaft.

71. The cartridge of claim 46 wherein:

said read head is rotatable with said shaft; and

said pattern is stationary with respect to said shaft.

72. A portable coordinate measurement machine (CMM) for measuring the position of an object in a selected volume, comprising:

a manually positionable articulated arm having opposed first and second ends, said arm including a plurality of jointed arm segments, each arm segment including at least one position transducer for producing a position signal;

a measurement probe attached to a first end of said articulated arm;

a base attached to a second end of said articulated arm;

said arm being progressively tapered from said base to said probe with said arm having the largest diameter at said base and the smallest diameter at said probe; and

an electronic circuit which receives the position signals from the transducers and provides a digital coordinate corresponding to the position of the probe in a selected volume.

73. The cartridge of claim 72 wherein:

said jointed arm segments include threaded ends and wherein said jointed arm segments are threadably interconnected to each other.

74. The cartridge of claim 73 wherein:

said threaded ends are tapered.

75. The cartridge of claim 72 wherein:

said progressive taper comprises a step-wise taper.

76. A portable coordinate measurement machine (CMM) for measuring the position of an object in a selected volume, comprising:

a manually positionable articulated arm having opposed first and second ends, said arm including a plurality of jointed arm segments, each arm segment including at least one position transducer for producing a position signal;

a measurement probe attached to a first end of said articulated arm;

said jointed arm segments including threaded ends and wherein said jointed arm segments are threadably interconnected to each other; and

an electronic circuit which receives the position signals from the transducers and provides a digital coordinate corresponding to the position of the probe in a selected volume.

77. The cartridge of claim 76 wherein:

said threaded ends are tapered.

78. A portable coordinate measurement machine (CMM) for measuring the position of an object in a selected volume, comprising:

a manually positionable articulated arm having opposed first and second ends, said arm including a plurality of jointed arm segments, each arm segment including at least one position transducer for producing a position signal;

a measurement probe attached to a first end of said articulated arm;

said jointed arm segments including complimentary male and female tapered ends and wherein said jointed arm segments are interconnected to each other using said tapered ends; and

an electronic circuit which receives the position signals from the transducers and provides a digital coordinate corresponding to the position of the probe in a selected volume.

79. The CARTRIDGE of claim 78 wherein:

said tapered ends are fastened together using threadable fasteners.