Control method and apparatus for an arc welding system

• US 6,335,511 B1
• Filed: 04/12/2000
• Issued: 01/01/2002
• Est. Priority Date: 04/12/1999
• Status: Expired due to Term

• Current Assignee: Tri Tool Inc.
• Original Assignee: Tri Tool Inc.
• Inventors: Rothermel, Ronald R.
• Primary Examiner(s): Shaw, Clifford C.
• Application Number:
  US09/547,996
• Time in Patent Office: 629 Days
• Field of Search: 219/130.31, 219/130.51, 219/124.02, 219/124.03, 219/125.12, 219/130.21, 219/137.PS, 219/130.33
• US Class Current: 219/130.51
• CPC Class Codes: B23K 9/091 characterised by the circuits
• CPC Class Codes: B23K 9/092 characterised by the shape of the pulses produced
• CPC Class Codes: B23K 9/093 the frequency of the pulses produced being modulatable
• CPC Class Codes: B23K 9/095 Monitoring or automatic control of welding parameters
• CPC Class Codes: B23K 9/1056 by using digital means B23K9/1068 takes precedence
• CPC Class Codes: B23K 9/1062 with computing means
• CPC Class Codes: B23K 9/126 Controlling the spatial relationship between the work and the gas torch between wire tip and piece B23K9/073
• CPC Class Codes: B23K 9/127 Means for tracking lines during arc welding or cutting copying in general B23Q35/00

Abstract

An arc welding control method and apparatus includes a voltage control loop in which a pulsation parameter such as pulse width, pulse amplitude, background amplitude between pulses, or frequency, is adjusted to compensate for deviations in the arc voltage, and a second, slower feedback loop which adjusts a second parameter of the system in order to cause the pulsation parameter to return to a desired value as a result of the effect of the adjusted second parameter on the arc voltage.

Claims

1. control apparatus for an arc welding system, comprising:

a first feedback loop, including;

a power source electrically arranged to supply electrical power in order to cause an arc to be generated between an electrode and a workpiece, the power source being electrically connected to the electrode by an electrical connection element;

a sensor arranged to measure a parameter representative of a distance between the electrode or connection element and the workpiece;

command signal generating circuitry arranged to generate a command signal in response to a difference between a desired parameter and an output of the sensor;

pulse waveform generating circuitry arranged to cause said power source to generate pulses having at least one pulsation parameter controlled by said command signal such that an output of the sensor is brought into correspondence with said desired parameter; and

a second feedback loop, including;

a second parameter controlling device arranged to control a second parameter;

a secondary feedback loop controller arranged to control said second parameter controlling device in response to a deviation between a second loop feedback signal representative of said at least one pulsation parameter and a reference signal representative of a desired value for said at least one pulsation parameter.

2. Apparatus as claimed in claim 1, wherein said second parameter is a parameter related to a position of the electrode or connection element relative to the workpiece.

3. Apparatus as claimed in claim 2, wherein said at least one pulsation parameter is selected from the group consisting of pulse width, pulse amplitude, background amplitude between pulses, and frequency.

4. Apparatus as claimed in claim 3, wherein said pulsation parameter is frequency.

5. Apparatus as claimed in claim 1, wherein said at least one pulsation parameter is selected from the group consisting of pulse width, pulse amplitude, background amplitude between pulses, and frequency.

6. Apparatus as claimed in claim 5, wherein said pulsation parameter is frequency.

7. Apparatus as claimed in claim 1, wherein said sensor is a voltage sensor for measuring a voltage between the electrode or connection element and the workpiece.

8. Apparatus as claimed in claim 7, wherein said second parameter controlling device is a proximity motor controller arranged to control a distance of the electrode or connection element from the workpiece.

9. Apparatus as claimed in claim 7, wherein said command signal generating circuitry includes an element arranged to compare the output of the voltage sensor with a desired voltage.

10. Apparatus as claimed in claim 7, wherein said voltage sensor is arranged to sense either peak voltage during a pulse, background voltage between pulses, or an average voltage averaged during at least one pulsation period.

11. Apparatus as claimed in claim 7, wherein said voltage sensor includes an analog-to-digital converter, and said command signal and waveform generating circuitry are included in a digital processor.

12. Apparatus as claimed in claim 1, wherein said second feedback loop feedback signal is said command signal.

13. Apparatus as claimed in claim 1, wherein the device arranged to control the second parameter is a proximity motor controller arranged to control a distance of the electrode or connection element from the workpiece.

14. Apparatus as claimed in claim 1, further comprising a consumable electrode and a drive arrangement for feeding the consumable electrode into the arc to cause material to be transported from the consumable electrode to the workpiece, said connection element being a contact tip in sliding engagement with the consumable electrode.

15. Apparatus as claimed in claim 1, wherein said pulse waveform generator has as one input said command signal and as a second input a pulse profile data input.

16. Apparatus as claimed in claim 15, wherein said pulse profile data is supplied by a look-up table.

17. Apparatus as claimed in claim 1, further comprising a device arranged to scan or oscillate the connection element or electrode across a surface of the workpiece in order to gather position-related, pulsation-parameter information, said information being correlated with a scan or oscillation pattern in order to adjust said second parameter.

18. Apparatus as claimed in claim 17, wherein said device is is further arranged to use said gathered information to control a position of the connection element or electrode across and along a surface of the workpiece in accord with a desired positional relationship.

19. Apparatus as claimed in claim 17, wherein said second parameter is a proximity of the connection element or electrode relative to the workpiece and wherein said proximity is controlled on the basis of information gathered when said connection element or electrode is within a predefined portion of said scan or oscillation pattern.

20. Apparatus as claimed in claim 19, wherein said device is further arranged to use differences between said information gathered at ends of said scan or oscillation pattern to adjust a scan or oscillation centerline in a direction which minimizes the differences.

21. Apparatus as claimed in claim 17, wherein said second parameter is a distance of the workpiece to the connection element or electrode, and said device is further arranged to gather and use differences in said distance correlated to a scan or oscillation pattern to control the position of the connection element or electrode across and along a surface of the workpiece in accord with a desired positional relationship.

22. Apparatus as claimed in claim 17, wherein said second parameter is a distance of the workpiece to the connection element or electrode, and said device is further arranged to use differences in said distance to determine and correct for changes in weld groove width and centerline.

23. Apparatus as claimed in claim 1, wherein said control apparatus includes at least one digital signal processor incorporating digital filtering and control algorithms arranged to enhance signal-to-noise ratios, stability, and control capabilities.

24. Control apparatus for an arc welding system, comprising:

a first feedback loop, including;

a power source electrically arranged to supply electrical power in order to cause an arc to be generated between an electrode and a workpiece, the power source being electrically connected to the electrode by an electrical connection element;

a voltage sensor arranged to measure a voltage difference between the electrode or connection element and the workpiece;

command signal generating circuitry arranged to generate a command signal in response to a difference between a desired voltage and an output of the voltage sensor;

current pulse waveform generating circuitry arranged to cause said power source to generate current pulses having at least one pulsation parameter controlled by said command signal such that an output of the voltage sensor is brought into correspondence with said desired voltage; and

a second feedback loop, including;

a second parameter controlling device arranged to control a second parameter;

a secondary feedback loop controller arranged to control said second parameter controlling device in response to a deviation between a second loop feedback signal representative of said at least one pulsation parameter and a reference signal representative of a desired value for said at least one pulsation parameter.

25. Apparatus as claimed in claim 24, wherein said second parameter is a parameter related to a position of the electrode or connection element relative to the workpiece.

26. Apparatus as claimed in claim 24, wherein said second loop feedback signal is developed directly from said command signal.

27. Apparatus as claimed in claim 24, wherein said at least one pulsation parameter is selected from the group consisting of pulse width, pulse amplitude, background amplitude between peaks, and frequency.

28. Apparatus as claimed in claim 27, wherein said pulsation parameter is frequency.

29. Apparatus as claimed in claim 24, wherein said second parameter controlling device is a proximity motor controller arranged to control a distance of the electrode or connection element from the workpiece.

30. Apparatus as claimed in claim 24, wherein said voltage sensor is arranged to sense either peak voltage during a pulse, background voltage between pulses, or an average voltage averaged during at least one pulsation period.

31. Apparatus as claimed in claim 24, wherein said voltage sensor includes an analog-to-digital converter, and said command signal and waveform generating circuitry are included in a digital processor.

32. Apparatus as claimed in claim 24, further comprising a consumable electrode and a drive arrangement for feeding the consumable electrode into the arc to cause material to be transported from the consumable electrode to the workpiece, said connection element being a contact tip in sliding engagement with the consumable electrode.

33. Apparatus as claimed in claim 24, wherein said current pulse waveform generating circuitry has as one input said command signal and as a second input pulse profile data.

34. Apparatus as claimed in claim 33, wherein said pulse profile data is supplied by a look-up table.

35. Apparatus as claimed in claim 24, further comprising a device arranged to scan or oscillate the connection element or electrode across a surface of the workpiece in order to gather position-related, pulsation-parameter information, said information being correlated with a scan or oscillation pattern in order to adjust said second parameter.

36. Apparatus as claimed in claim 35, wherein said device is further arranged to use said gathered information to control a position of the connection element or electrode across and along a surface of the workpiece in accord with a desired positional relationship.

37. Apparatus as claimed in claim 35, wherein said second parameter is a proximity of the connection element or electrode relative to the workpiece and wherein said proximity is controlled on the basis of information gathered when said connection element or electrode is within a predefined portion of said scan or oscillation pattern.

38. Apparatus as claimed in claim 37, wherein said device is further arranged to use differences between said information gathered at ends of said scan or oscillation pattern to adjust a scan or oscillation centerline in a direction which minimizes the differences.

39. Apparatus as claimed in claim 35, wherein said second parameter is a distance of the workpiece to the connection element or electrode, and said device is further arranged to gather and use differences in said distance correlated to the scan or oscillation pattern to control a position of the connection element or electrode across and along a surface of the workpiece in accord with a desired positional relationship.

40. Apparatus as claimed in claim 35, wherein said second parameter is a distance of the workpiece to the connection element or electrode, and said device is further arranged to use differences in said distance to determine and correct for changes in weld groove width and centerline.

41. Apparatus as claimed in claim 24, wherein said control apparatus includes at least one digital signal processor incorporating digital filtering and control algorithms arranged to enhance signal-to-noise ratios, stability, and control capabilities.

42. An arc welding method, comprising the steps of:

supplying an electrical pulse train having pulsation parameters to the electrode or connection element in order to establish an arc between the electrode and the workpiece;

measuring an electrical parameter of the arc representative of a distance between the electrode or connection element and the workpiece;

varying at least one of the pulsation parameters in response to changes in the electrical parameter such that the electrical parameter is brought into correspondence with a desired parameter; and

adjusting an additional parameter in order to cause the at least one of the pulsation parameters to return to a desired value.

43. A method as claimed in claim 42, wherein the additional parameter is a parameter related to a position of the electrode or connection element relative to the workpiece.

44. A method as claimed in claim 43, wherein the at least one of the pulsation parameters is selected from the group consisting of pulse width, pulse amplitude, background amplitude between pulses, and frequency.

45. A method as claimed in claim 44, wherein the at least one of the pulsation parameters is frequency.

46. A method as claimed in claim 42, wherein the at least one of the pulsation parameters is selected from the group consisting of pulse width, pulse amplitude, background amplitude between pulses, and frequency.

47. A method as claimed in claim 46, wherein the at least one of the pulsation parameters is frequency.

48. A method as claimed in claim 42, wherein the step of measuring the electrical parameter comprises the step of measuring the voltage between the electrode or connection element and the workpiece.

49. A method as claimed in claim 42, wherein the step of adjusting the additional parameter comprises the step of electro-mechanically adjusting a distance of the electrode or connection element from the workpiece.

50. A method as claimed in claim 49, wherein the step of adjusting the parameter related to electrode or connection element distance comprises the step of comparing a commanded pulsation parameter with a reference representative of said desired value of said at least one pulsation parameter.

51. A method as claimed in claim 50, further comprising the step of automatically acquiring a reference representative of the desired value of said at least one pulsation parameter by momentarily locking the position of the electrode or connection element relative to the workpiece, followed by the steps of supplying an electrical pulse train having desired pulsation parameters to the electrode or connection element in a consumable electrode arc welding apparatus in order to establish an arc between the electrode and the workpiece;

measuring an electrical parameter of the arc; and

varying one of the pulsation parameters in response to changes in the electrical parameter until the one of the pulsation parameters settles;

subsequently storing the varied pulsation parameters for use as the reference pulsation parameter, and unlocking the position of the electrode or connection element relative to the workpiece.

52. A method as claimed in claim 42, further comprising the steps of scanning or oscillating the connection element or electrode across a surface of the workpiece in order to gather position-related, pulsation-parameter information;

and correlating said information with a scan or oscillation pattern in order to adjust said additional parameter.

53. A method as claimed in claim 52, wherein said additional parameter is a proximity of the connection element or electrode relative to the workpiece and wherein said proximity is adjusted on the basis of said information gathered when said connection element or electrode is within a predefined portion of said scan or oscillation pattern.

54. A method as claimed in claim 53, further comprising the step of using differences between said information gathered at ends of said scan or oscillation pattern to adjust a scan or oscillation centerline in a direction which minimizes the differences.

55. A method as claimed in claim 52, wherein said additional parameter is a distance of the workpiece to the connection element or electrode, and further comprising the step of using differences in said distance to determine and correct for changes in weld groove width and centerline.

56. A method as claimed in claim 52, further comprising the step of using said gathered information to control a position of the connection element or electrode across and along a surface of the workpiece in accord with a desired positional relationship.

57. A method as claimed in claim 52, wherein said additional parameter is a distance of the workpiece to the connection element or electrode, and further comprising the steps of gathering and using differences in said distance correlated to said scan or oscillation pattern to control the position of the connection element or electrode across and along a surface of the workpiece in accord with a desired positional relationship.