Using infrared imaging to monitor and control welding

• US 4,877,940 A
• Filed: 06/30/1987
• Issued: 10/31/1989
• Est. Priority Date: 06/30/1987
• Status: Expired due to Fees

• Current Assignee: Edmund R. Bangs
• Original Assignee: IIT Research Institute (Alion Science & Technology Corp.)
• Inventors: Blaha, James R., Bangs, Edmund R., Longinow, Nicholas E.
• Primary Examiner(s): Shaw, Clifford C.
• Application Number:
  US07/068,620
• Time in Patent Office: 854 Days
• Field of Search: 219/124.34, 219/130.01, 219/130.21, 219/137 PS, 219/125.1, 219/110, 364/200, 364/275.3
• US Class Current: 219/124.34
• CPC Class Codes: B23Q 35/127 using non-mechanical sensing
• CPC Class Codes: Y10S 706/904 Manufacturing or machine, e.g. agricultural machinery, machine tool

Abstract

The technique and arrangement of distributed, real time, intelligent control of welding including IR detection and measurement of process conditions, and controlling process parameters in view of a knowledge base including a predetermined rule set for interpreting the results of IR detection. The arrangement includes a multilevel communication scheme internally and between hardware nodes of the arrangement, and the data-driven scheduling of inference processes under direction of a semantic network.

Claims

1. A real time welding process for welding adjacent materials with a weld puddle formed between the materials, said method comprising the steps of bringing a welding apparatus and consumable and the materials together to form a weld puddle at the interface of the adjacent materials, producing relative motion between the welding apparatus and the materials thereby defining a front edge of the weld puddle, thermographically scanning the weld puddle and its adjacent heat affected zone from the front and producing image signals representative of a thermographic image of the weld, analyzing said puddle image signals to extract therefrom data indicative of irregularities in the welding procedure, and adjusting the welding procedure to reduce said irregularities.

2. A welding process in accordance with claim 1 wherein the step of adjusting the welding procedure includes the steps of adjusting the electrical power provided and adjusting the position of the welding apparatus torch.

3. A welding process in accordance with claim 1 in which the data extracted defines the size of the weld puddle, and in which the step of adjusting the welding procedure includes the steps of determining whether adjustment of the electrical power provided to the torch will modify the puddle shape to within a predetermined range, and adjusting the travel speed of the torch when adjustment of the current is not sufficient.

4. A welding process in accordance with claim 3 including the step of determining whether a predetermined amperage change will adjust the width of the puddle to within a predetermined puddle range and, if not, then determining the speed adjustment necessary for the torch to change the width of the puddle sufficiently to cause it to fall within said predetermined range, and then changing the speed of torch travel accordingly.

5. A welding process in accordance with claim 1 including the step of storing procedure variables in real time for later analysis.

6. A welding process in accordance with claim 1 including the step of inspecting the weld puddle for defects in real time during the welding of the materials.

7. A welding process in accordance with claim 1 in which the adjusting step includes adjustment of the following:

(a) voltage or amperage,

(b) lateral and/or angular setting of the welding torch,

(c) speed of torch travel, and

(d) angular adjustment to a track angle.

8. A welding process in accordance with claim 1 including the steps of taking isotherm line scans of the weld puddle and relating the isotherms in real time to weld size measurements.

9. A welding process in accordance with claim 1 including the analysis in real time of the isotherm scans of weld size as a function of weld current.

10. A welding process in accordance with claim 1 in which the width and depth of the weld puddle is determined in real time.

11. A welding process in accordance with claim 1 wherein the welding apparatus employs gas shielding to form and protect the weld puddle, and including the steps of determining the dew point of the shield gas employed during welding, and aborting the welding operation when selected irregularities appear and the dew point of the gas indicates the shielding gas is too humid.

12. A welding process in accordance with claim 1 in which the forward tip of the image of the weld puddle is analyzed for projections indicating deviation of the weld path from the seam direction, and in which the welding procedure is adjusted to more closely track the weld seam.

13. A welding process in accordance with claim 1 in which the data indicative of irregularities extracted from the image signals include the width of the weld puddle.

14. A welding process in accordance with claim 1 in which the data indicative of irregularities extracted from the image signals include the width of the weld puddle measured perpendicular to the path of travel.

15. A welding process in accordance with claim 1 in which the data indicative of irregularities extracted from the image signals include the rate of heat flow out of the puddle.

16. A welding process in accordance with claim 1 in which the data indicative of irregularities extracted from the image signals include a determination of the difference in puddle brightness at points on the puddle perimeter.

17. A welding process in accordance with claim 1 in which the data indicative of irregularities extracted from the image signals include the rate of heat flow out of the puddle determined by taking the reciprocal of the distance between two points at predetermined respective higher and lower brightness levels located on either side of the puddle perimeter.

18. A welding process in accordance with claim 1 in which the data indicative of irregularities extracted from the image signals include the change in puddle geometry at its perimeter at a point defined by the perimeter and a line perpendicular to the direction of travel passing through the puddle center.

19. A welding process in accordance with claim 1 in which the data indicative of irregularities extracted from the image signals include the number of times the actual puddle perimeter crosses over a theoretical smooth puddle perimeter within a given zone.

20. A welding process in accordance with claim 1 wherein the zone encloses the leading edge of the puddle.

21. A welding process in accordance with claim 1 wherein the zone encloses a portion of the puddle perimeter to the left or right of the puddle center.

22. A welding process in accordance with claim 1 in which the data indicative of irregularities extracted from the image signals include measurements of the area of the puddle within a zone that overlaps its perimeter.

23. A welding process in accordance with claim 1 in which the data indicative of irregularities extracted from the image signals include a measurement of the length of the puddle perimeter.

24. A welding process in accordance with claim 1 in which the data indicative of irregularities extracted from the image signals include measuring the length of the puddle perimeter within a zone that overlaps its perimeter.

25. A welding process in accordance with claim 1 in which the data indicative of irregularities extracted from the image signals includes measuring the area of the puddle within a zone that overlaps the perimeter.

48. The welding method according to claim 1 or 36 wherein the welding is halted when said weld puddle reaches a predetermined size.

49. The invention according to claims 1 or 36, wherein the track of welding is adjusted in response to establishment of an angle of deviation from the weld seam.

50. The invention according to claim 49, wherein said angle of deviation is established in response to misalignment of said welding apparatus.

51. The invention according to claim 50, wherein said misalignment is indicated by the direction of a protrusion along the leading edge of said weld puddle.

52. The invention according to claims 1 or 36, wherein the angle of said welder from a perpendicular to said welded surfaces is adjusted in response to the appearance of a mismatch condition.

53. The invention according to claim 52, wherein said mismatch is indicated by the shape of a protrusion in the leading edge of said weld puddle.

26. A welding arrangement for controlling the welding of selected adjacent materials, said welding arrangement comprising infra-red detection means for observing radiation from the vicinity of the weld, said detection means effective for producing weld signals indicative of conditions detected with regard to welding operations, analysis means for receiving weld signals produced by said detection means, said analysis means effective for analyzing said weld signals to establish an analytical representation thereof, controller means for receiving the results of analysis from said analysis means, said controller means comprising memory means for holding a plurality of knowledge bases including a semantic network effective for defining the interrelationship of predetermined goals and subgoals descriptive of the accomplishment of welding operations, said memory means further including a rule base including predetermined rules enabling the development of inferences with respect to said analysis of said weld signals, knowledge mechanism means distributed over a plurality of nodes for implementing directions provided by said respective knowledge bases, and scheduling means for determining the performance of inferencing operations according to the rules in said rule base.

27. A welding arrangement according to claim 26 wherein said knowledge means is distributed over a plurality of hardware nodes.

28. A welding arrangement according to claim 26, said controller means further comprising knowledge layer means for ascertaining the node location of particular knowledge bases.

29. A welding arrangement according to claim 26, said controller means comprising means for communicating knowledge between nodes in response to an inference process.

30. A welding arrangement according to claim 26 wherein said scheduling means controls the transfer of inference processes between running, ready and suspended queues.

31. A welding arrangement according to claim 26 comprising running, ready and suspended queues to enable inference processing.

32. A welding arrangement according to claim 26 wherein said detection means is effective for infrared detection of said weld puddle.

33. A welding arrangement according to claim 26 wherein said analysis means provides an indication of weld puddle width.

34. A welding arrangement according to claim 26 wherein said analysis means provides an indication of weld puddle position.

35. A welding arrangement according to claim 26 wherein said rule base halts the operation of welding if said welding arrangement detects irregularities and if the shield gas dew point indicates the shield gas is drier than a predetermined limit.

36. A method for welding selected adjacent materials with a weld puddle along the edges at which the materials abut and including a consumable, by producing relative motion between the materials and welding apparatus and observing radiation of heat from the leading edge of said weld puddle, by analyzing the pattern of said radiation, and by adjusting weld speed and current in view of the results of said analysis.

37. The method according to claim 36, wherein said analysis determines the width of said weld puddle.

38. The method according to claim 36, wherein said analysis determines whether the dimensions of the weld puddle fall within a predetermined range of values.

39. The method according to claim 36, wherein weld speed is decreased, if said weld puddle is too small.

40. The method according to claim 36, wherein the weld current is increased, if said weld puddle is too small.

41. The method according to claim 36, wherein said weld current is modified in response to the cooling rate of said weld puddle.

42. The method according to claim 36, wherein said weld speed is modified in response to the cooling rate of said weld puddle.

43. The method of claim 36, wherein analysis of the pattern of said radiation includes observation of protrusions in the leading edge of said weld puddle.

44. The method according to claim 43, including making a determination of whether said protrusions are indicative of mismatch, misalignment and root opening defects.

45. The method of claim 36, wherein the analysis determines the cooling rate of said weld puddle by by a predetermined average of pixel values across the edge of the weld puddle.

46. The method according to claim 45, wherein determining said cooling rate includes subtracting pixel values separated by a predetermined length across the edge of the weld.

47. The method according to claim 45, wherein the average is established by subtracting selected separated pixel values straddling the edge of the weld puddle and dividing by the amount of separation.

54. A welding apparatus for controlling the welding of selected materials and including an automated welding apparatus, said welding apparatus comprising:

image capturing means for capturing a heat image of at least a single selected zone of the weld region and producing a digital representation of said image;

first high-speed information processing means connecting to said image capturing means to receive said digital representation for extracting from said representation at high speed a much smaller amount of data indicative of irregularities in the welding process, or the lack thereof;

second artificial intelligence information processing means connecting to said first high-speed information processing means to receive said data indicative of irregularities in the welding process, or the lack thereof, for analyzing said data using the principles of artificial intelligence programming and for generating process control data; and

third high-speed information processing means connecting to said second artificial intelligence information processing means to receive said process control data and connecting to said welding apparatus for operating said welding apparatus under the control of said process control data;

whereby real time control of welding under artificial intelligence programming control is achieved.

55. A welding apparatus in accordance with claim 54 wherein the means for operating said welding apparatus includes means for adjusting the electrical power provided and adjusting the position of the welding apparatus torch.

56. A welding apparatus in accordance with claim 54 in which the data extracted define the size of the weld puddle, and in which the means for analyzing said data includes means for determining whether adjustment of the electrical power provided to the torch will modify the puddle shape to within a predetermined range, and means for adjusting the travel speed of the torch when adjustment of the current is not sufficient.

57. A welding apparatus in accordance with claim 54 including means for determining whether a predetermined amperage change will adjust the width of the puddle to within a predetermined puddle range, and means for determining the speed adjustment necessary for the torch to change the width of the puddle sufficiently to cause it to fall within said predetermined range, and means for changing the speed of torch travel accordingly.

58. A welding apparatus in accordance with claim 54 including means for storing data indicative of irregularities in the welding process, or the lack thereof, in real time during the welding of the materials for later analysis.

59. A welding apparatus in accordance with claim 54 including means for inspecting the weld puddle for defects in real time during the welding of the materials.

60. A welding apparatus in accordance with claim 54 in which the means for operating said welding apparatus includes means for adjusting voltage or amperage;

means for adjusting lateral and/or angular adjustments of the welding torch position;

means for adjusting the speed of torch travel; and

means for adjusting angular adjustment to a track angle.

61. A welding apparatus in accordance with claim 54 including means for taking isotherm line scans of the weld puddle and means for relating the isotherms in real time to weld size measurements.

62. A welding apparatus in accordance with claim 61 including means for analysis in real time of the isotherm scans of weld size as a function of weld current.

63. A welding apparatus in accordance with claim 54 in which the width and depth of the weld puddle is determined in real time.

64. A welding apparatus in accordance with claim 54 including means for monitoring shield gas dew point during welding, and which further includes means for aborting welding operations when the dew point indicates the shielding gas is too humid.

65. A welding apparatus in accordance with claim 54 in which the forward tip of the image of the weld puddle is analyzed for projections indicating deviation of weld path from seam direction and adjusted to more closely track the weld seam.

66. A welding apparatus in accordance with claim 54 in which the data indicative of irregularities extracted from the image signals include the width of the weld puddle.

67. A welding apparatus in accordance with claim 54 in which the data indicative of irregularities extracted from the image signals include the width of the weld puddle measured perpendicular to the path of travel through the center of brightness of the puddle to points on the puddle perimeter of lower brightness than the brightness at the center of brightness.

68. A welding apparatus in accordance with claim 54 in which the data indicative of irregularities extracted from the image signals include the rate of heat flow out of the puddle.

69. A welding apparatus in accordance with claim 54 in which the data indicative of irregularities extracted from the image signals include a measurement of the change in puddle brightness at points adjacent to the puddle perimeter.

70. A welding apparatus in accordance with claim 54 in which the data indicative of irregularities extracted from the image signals include the rate of heat flow out of the puddle determined by taking the reciprocal of the distance between two points at predetermined respective higher and lower brightness levels located on either side of the puddle perimeter.

71. A welding apparatus in accordance with claim 54 in which the data indicative of irregularities extracted from the image signals include the rate of change in puddle brightness at its perimeter at a point defined by the perimeter and a line perpendicular to the direction of travel passing through the puddle center of brightness.

72. A welding apparatus in accordance with claim 54 in which the data indicative of irregularities extracted from the image signals include the number of times the actual puddle perimeter crosses over a theoretical smooth puddle perimeter within a given zone.

73. A welding apparatus in accordance with claim 54 wherein at least one of said zones contains the leading edge of the puddle.

74. A welding apparatus in accordance with claim 54 wherein at least one of said zones encloses a portion of the puddle perimeter to the left or right of the puddle center.

75. A welding apparatus in accordance with claim 54 in which the data indicative of irregularities extracted from the image signals include measurements of the area of the puddle within a zone that overlaps its perimeter.

76. A welding apparatus in accordance with claim 54 in which the data indicative of irregularities extracted from the image signals include measuring the length of the puddle perimeter.

77. A welding apparatus in accordance with claim 54 in which the data indicative of irregularities extracted from the image signals include measuring the length of the puddle perimeter within a zone that overlaps its perimeter.

78. A welding apparatus in accordance with claim 54 in which the data indicative of irregularities extracted from the image signals include measuring the area of the puddle within a zone that overlaps the perimeter.

79. A welding apparatus for controlling the welding of selected adjacent materials with a weld puddle along their interface formed from adjacent materials and a consumable comprising:

infrared detection means sensitive to thermal radiation in the vicinity of 10 to 11 microns where the puddle leading edge defects are visible attached to said automatic welder for observing infrared radiation from the leading edge of said weld puddle and generating data representing an image of said puddle; and

information processing means connected to said infrared detection means for analyzing said data, and effective for establishing control strategies therefrom, and for operating said automatic welder in accordance with said control strategies.

80. A welding apparatus for welding with a weld puddle using a controllable welder device, said apparatus comprising:

image detection means for observing radiation emitted from said weld puddle and for generating data representing an image of said puddle;

image data reduction means connected to said image detection means to receive said data representing an image, for analyzing said data to derive therefrom a reduced amount of data characterizing said image;

image analysis means connecting to said image data reduction means to receive said reduced amount of data for analyzing said reduced amount of data to derive therefrom data characterizing the welding process and any irregularities therein;

control strategy determination means connecting to said image analysis means to receive said data characterizing the welding process and any irregularities therein, for analyzing said data characterizing the welding process to derive therefrom data characterizing control strategies to govern the welding process;

control implementation means connecting to said control strategy determination means to receive said data characterizing control strategies and also connecting to said controllable welder device for operating said welder, in accordance with said control strategies; and

wherein said image data reduction means, image analysis means, control strategy determination means, and control implementation means are implemented as separate nodes, at least some of which nodes reside on independent data processors.

81. An apparatus in accordance with claim 80 wherein said image analysis means and control strategy determination means are implemented using artificial intelligence programming techniques so that a knowledge engineer working with experts in welding may design the process control strategies that control the welding process.

82. A welding method for welding materials along a seam established therebetween by the progress of a weld puddle including a consumable, said method comprising the steps of beginning welding operation, inspecting the geometry of said weld puddle in terms of protrusions along its leading edge, determining whether said inspection discloses any of a number of predetermined weld defects, and modifying weld process parameters in response to said determination.

83. The method according to claim 82, wherein the angle of the track of said weld puddle is adjusted if a misalignment angle defect is determined.

84. The method according to claim 82, wherein the angle of said welder is modified if a mismatch defect is determined.

85. The method according to claim 82, wherein the weld speed is reduced if an excessive root opening is determined between the materials being welded.

86. The method according to claim 82, wherein said weld puddle geometry is interpreted in terms of isotherms indicative of weld puddle protrusions at selected temperature levels.

87. The method according to claim 82, wherein welding is terminated if the temperature of said weld puddle gets too hot.

88. The method according to claim 87, wherein weld puddle temperature is determined by evaluating the levels of predetermined isotherms in said weld puddle.

89. The method according to claim 82, wherein welding is terminated if the weld puddle gets too wide.

90. The method according to claim 82, wherein welding is terminated if the dew point level of the shield gas employed in welding indicates that the shield gas exceeds a predetermined maximum humidity value.

91. A welder arrangement for welding a seam in materials and a consumable to be joined with a weld puddle traveling along said seam, said arrangement effective for establishing an arc of current between the arrangement and said weld puddle, said arc and said weld puddle substantially enclosed in a shield gas during welding operation to protect said weld from degradation during its establishment, said welder arrangement including detection means for detecting the infra-red geometry of the leading edge of said weld puddle, said geometry comprising the shape and separation of isotherms characterizing the heat in said weld puddle at the time of detection, said welder arrangement including analysis means for analyzing the features detected by said detection means, and including modifying means for modifying weld process parameters in response to said analysis.

92. The arrangement of claim 91, wherein said detection means is effective for detecting protrusions in the leading edge of said weld puddle.

93. The arrangement of claim 92, wherein said analysis is effective for classifying the kind of defect which has caused said protrusion.

94. The arrangement of claim 91, wherein said modifying means includes means for modifying the weld speed in response to analysis by said analysis means.

95. The arrangement of claim 91, wherein said modifying means includes means for modifying the weld current in response to analysis by said analysis means.

96. The arrangement of claim 91, wherein said modifying means includes means for modifying the track of said welder in response to analysis by said analysis means.

97. The arrangement of claim 91, wherein said modifying means includes means for modifying the angle of said welder from the perpendicular in response to analysis by said analysis means.

98. The arrangement of claim 92, wherein the detected protrusions are indicative of misalignment.

99. The arrangement of claim 92, wherein the detected protrusions are indicative of mismatch.

100. The arrangement of claim 92, wherein the detected protrusions are indicative of excessive root opening.

101. A real time welding process for welding adjacent materials with a weld puddle formed between the materials, said method comprising the steps of bringing a welding apparatus that employs a gas shield to form and protect the puddle and the materials together into position to form the weld puddle at the interface of the adjacent materials, thermographically scanning the weld puddle and its adjacent heat affected zone and producing image signals representative of a thermographic image of the weld, analyzing said puddle image signals to extract therefrom data indicative of irregularities in the welding process, adjusting the welding procedure to reduce said irregularities, determining the dew point of the shield gas employed during welding, and aborting the welding operation when selected irregularities appear and the dew point of the gas indicates the shield gas is too humid.

102. A welding arrangement for controlling the welding of selected adjacent materials with a weld puddle along their interface, said welding arrangement comprising detection means for observing radiation from said weld puddle, said detection means effective for producing weld signals indicative of conditions detected with regard to welding operations, analysis means for receiving weld signals produced by said detection means, said analysis means effective for analyzing said weld signals to establish an analytical representation thereof, controller means for receiving the results of analysis from said analysis means, said controller means comprising memory means for holding a plurality of knowledge bases including a semantic network effective for defining the interrelationship of predetermined goals and subgoals descriptive of the accomplishment of the welding operation, said memory means further including a rule base including predetermined rules enabling the development of inferences with respect to said analysis of said weld signals, and knowledge mechanism means for implementing directions provided to said respective knowledge bases;

and scheduling means for determining the performance of inferencing operations according to the rules in said rule base;

wherein said rule base halts the operation of welding, if the shield gas dew point indicates the shield gas is more humid than a predetermined limit.

103. A welding apparatus for controlling the welding of selected adjacent materials with a weld puddle forming at the point of welding and including an automated welding apparatus, said welding apparatus comprising:

image capturing means for capturing an image of at least a single selected zone of the weld puddle and producing a digital representation of said image;

first high-speed information processing means connecting to said image capturing means to receive said digital representation for extracting form said representation at high speed a much smaller amount of data indicative of irregularities in the welding process, or the lack thereof;

second artificial intelligence information processing means connecting to said first high-speed information processing means to receive said data indicative of irregularities in the welding process, or the lack thereof, for analyzing said data using the principles of artificial intelligence programming and for generating process control data;

third high-speed information processing means connecting to said second artificial intelligence information processing means to receive said process control data and connecting to said welding apparatus for operating said welding apparatus under the control of said process control data;

means for monitoring shield gas dew point during welding;

means for aborting the welding operation when the dew point indicates the shielding gas is too humid;

whereby real time control of welding under artificial intelligence programming control is achieved.

104. A welding method for welding materials along a seam established therebetween by the progress of a weld puddle, said method comprising the steps of beginning the welding operation, inspecting the geometry of said weld puddle in terms of protrusions along its leading edge, determining whether said inspection discloses any of a number of predetermined weld defects, modifying weld process parameters in response to said determination, and terminating welding if the dew point level of the shield gas employed in welding indicates that the shield gas humidity exceeds a predetermined maximum value.

105. A real time welding process for welding adjacent materials, said method comprising the steps of bringing a welding apparatus and the materials together into position for welding, thermographically scanning the heat affected zone, producing image signals representative of the thermographic image of the weld, analyzing said puddle image signals to extract therefrom data indicative of irregularities in the welding procedure, adjusting the welding procedure to reduce said irregularities, and storing the procedure variables in real time for later analysis as a record of the quality of the weld.