ROBOT CONTROL UNIT FOR CONTROLLING TANDEM ARC WELDING SYSTEM, AND ARC-SENSOR CONTROL METHOD USING THE UNIT

• US 20080083716A1
• Filed: 09/10/2007
• Published: 04/10/2008
• Est. Priority Date: 10/06/2006
• Status: Active Grant

• Current Assignee: Klaus Schmidt
• Original Assignee: Klaus Schmidt
• Inventors: Shigeyoshi, Masayuki
• Granted Patent: US 7,999,208 B2
• Time in Patent Office: Days
• US Class Current: 219/125.12
• CPC Class Codes: B23K 9/0216 Seam profiling, e.g. weaving, multilayer
• CPC Class Codes: B23K 9/121 Devices for the automatic supply of at least two electrodes one after the other
• CPC Class Codes: B23K 9/1272 Geometry oriented, e.g. beam optical trading

Abstract

A robot control unit for controlling a tandem arc welding system, which has a welding torch, a robot for weaving the welding torch, a leading electrode power supply, and a trailing electrode power supply, includes a leading electrode detection section and a trailing electrode detection section for detecting quantity of welding state during weaving; a leading electrode processing section for calculating amounts of electrical change; a leading electrode correction section for calculating correction amounts for correcting displacement in horizontal and vertical directions from a weld line of a weaving center trajectory based on the amounts of electrical change; a trailing electrode processing section for calculating an amount of electrical change; and a trailing electrode correction section for calculating a correction amount for correcting displacement in a rotational direction from the weld line of the weaving center trajectory based on the amount of electrical change. According to the robot control unit, arc welding can be performed, which is excellent in accuracy of arc-sensor control, and hardly produces welding defects.

Claims

1. A robot control unit for controlling a position of a welding torch in a tandem arc welding system that has the welding torch having a leading electrode and a trailing electrode at a tip, a robot that is attached with the welding torch, and weaves that welding torch right and left with respect to a travelling direction of welding, and a leading electrode power supply and a trailing electrode power supply for supplying power to the leading electrode and the trailing electrode;

and performs arc welding along a weld line, the robot control unit comprising;

a leading electrode detection section for detecting quantity of welding state during weaving the leading electrode;

a trailing electrode detection section for detecting quantity of welding state during weaving the trailing electrode;

a leading electrode processing section for calculating amounts of electrical change from the quantity of welding state detected by the leading electrode detection section;

a leading electrode correction section for calculating correction amounts for correcting displacement in horizontal and vertical directions from the weld line of a weaving center trajectory based on the amounts of electrical change calculated by the leading electrode processing section;

a trailing electrode processing section for calculating an amount of electrical change from the quantity of welding state detected by the trailing electrode detection section; and

a trailing electrode correction section for calculating a correction amount for correcting displacement in a rotational direction from the weld line of the weaving center trajectory based on the amount of electrical change calculated by the trailing electrode processing section.

2. An arc-sensor control method using the robot control unit according to claim 1, comprising:

a leading electrode control step that, during one cycle of weaving,

in the leading electrode processing section, amounts of electrical change are calculated from the quantity of welding state detected by the leading electrode detection section, and assumed to be a first change amount of leading electrode and a second change amount of leading electrode respectively, and

in the leading electrode correction section, a horizontal correction amount of leading electrode for correcting horizontal displacement from the weld line of a weaving center trajectory is calculated based on the first change amount of leading electrode, and a vertical correction amount of leading electrode for correcting vertical displacement from the weld line of the weaving center trajectory is calculated based on the second change amount of leading electrode, and the welding torch is controlled in horizontal and vertical directions with respect to the travelling direction with the horizontal correction amount of leading electrode and the vertical correction amount of leading electrode; and

a trailing electrode control step, which is performed concurrently with or following the leading electrode control step, that, during the one cycle of weaving,

in the trailing electrode processing section, an amount of electrical change is calculated from the quantity of welding state detected by the trailing electrode detection section and assumed to be a change amount of trailing electrode, and

in the trailing electrode correction section, a correction amount of trailing electrode for correcting rotational displacement from the weld line of the weaving center trajectory is calculated based on the change amount of trailing electrode, and the welding torch is controlled in a rotational direction with respect to the travelling direction with the correction amount of trailing electrode.

3. The arc-sensor control method according to claim 2:

wherein, in the leading electrode control step, a welding current value is used as the quantity of welding state, and the second change amount of leading electrode corresponds to difference between an average welding current value of the leading electrode detected during one cycle of weaving, and a previously set, reference welding current value.

4. The arc-sensor control method according to claim 2:

wherein, in the leading electrode control step, the first change amount of leading electrode corresponds to difference between quantity of left end welding state of the leading electrode detected at a left end of weaving, and quantity of right end welding state of the leading electrode detected at a right end of weaving.

5. The arc-sensor control method according to claim 2:

wherein, in the leading electrode control step, the first change amount of leading electrode corresponds to difference between first difference in quantity of welding state and second difference in quantity of welding state, and

the first difference in quantity of welding state is defined as difference between rightward maximum quantity of welding state and rightward minimum quantity of welding state of the leading electrode, which are detected during a rightward weaving period from a left end to a right end of weaving, and

the second difference in quantity of welding state is defined as difference between leftward maximum quantity of welding state and leftward minimum quantity of welding state of the leading electrode, which are detected during a leftward weaving period from the right end to the left end of weaving.

6. The arc-sensor control method according to claim 2:

wherein, in the trailing electrode control step, the change amount of trailing electrode corresponds to difference between quantity of left end welding state of the trailing electrode detected at a left end of weaving, and quantity of right end welding state of the trailing electrode detected at a right end of weaving.

7. The arc-sensor control method according to claim 2:

wherein, in the trailing electrode control step, the change amount of trailing electrode corresponds to difference between third difference in quantity of welding state and fourth difference in quantity of welding state, and

the third difference in quantity of welding state is defined as difference between rightward maximum quantity of welding state and rightward minimum quantity of welding state of the trailing electrode, which are detected during a rightward weaving period from a left end to a right end of weaving, and

the fourth difference in quantity of welding state is defined as difference between leftward maximum quantity of welding state and leftward minimum quantity of welding state of the trailing electrode, which are detected during a leftward weaving period from the right end to the left end of weaving.

8. The arc-sensor control method according to claim 2:

wherein, in the leading electrode control step, the vertical correction amount of leading electrode is in proportion to magnitude of the second change amount of leading electrode.

9. The arc-sensor control method according to claim 2:

wherein, in the leading electrode control step, the horizontal correction amount of leading electrode is in proportion to magnitude of the first change amount of leading electrode.

10. The arc-sensor control method according to claim 2:

wherein, in the trailing electrode control step, the correction amount of trailing electrode is in proportion to magnitude of the change amount of trailing electrode.

11. The arc-sensor control method according to claim 2:

wherein, in the leading electrode control step, the vertical correction amount of leading electrode is set to be zero before the second change amount of leading electrode exceeds a predetermined threshold value, and the vertical correction amount is set to be a predetermined, certain amount when the second change amount of leading electrode exceeds the threshold value.

12. The arc-sensor control method according to claim 2:

wherein, in the leading electrode control step, the horizontal correction amount of leading electrode is set to be zero before the first change amount of leading electrode exceeds a predetermined threshold value, and the horizontal correction amount is set to be a predetermined, certain amount when the first change amount of leading electrode exceeds the threshold value.

13. The arc-sensor control method according to claim 2:

wherein, in the trailing electrode control step, the correction amount of trailing electrode is set to be zero before the change amount of trailing electrode exceeds a predetermined threshold value, and the correction amount is set to be a predetermined, certain amount when the change amount of trailing electrode exceeds the threshold value.