JPH02127979A - Weld line profiling device - Google Patents

Abstract

PURPOSE:To accurately control a welding torch to profile a weld line without being influenced by disturbance by superimposing an AC signal of prescribed frequency on a welding current at the time of allowing the welding torch to profile the weld line by utilizing welding arc sound. CONSTITUTION:When an arc 5 is generated between material 3 to be welded and a wire 4 of the welding torch 2 to arc-weld the material 3 to be welded, AC of the prescribed frequency is supplied from an oscillator 6 to a welding power source 1 and superimposed on the arc 5. The arc sound is detected as an electrical signal by a microphone 7 fitted integrally with the welding torch 2 and amplified by an amplifier 8 and then, AC of the specific frequency by the oscillator 6 is extracted by a band-pass filter 9 and outputted to an arc sound amplitude extractor 11 via a rectifier 10. The output is inputted to a torch dislocation detector 13 and a correction signal from a torch position correction part 18 is outputted to a robot 20 via a robot controller 19 and the welding torch 2 is correctly subjected to profile control on the weld line.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a weld line copying device, and particularly to an arc sound utilizing device.

[Conventional technology]

Conventionally, when tracing a welding line, a limit switch was used near the welding torch, and a contact-type detector such as a roller for the welded material was used, but there were problems with durability and reliability, and it was difficult to trace the welding line. It was difficult to accurately trace the welding torch. To deal with this, for example, as described in JP-A-56-39170, the position of the welding torch is corrected according to the deviation of the arc sound at the left and right ends by weaving the welding torch, so that the arc sounds at the left and right ends match. A device has been proposed that causes the welding torch to follow the welding line in this manner.

[Problem to be solved by the invention]

Since the above-mentioned conventional technology uses arc sound to trace a weld line, it is superior in mechanical durability to a contact type detector.

However, since arc noise is closely related to the arc phenomenon, it is affected by disturbances such as wire feed fluctuations, arc voltage or welding current fluctuations, and background sounds around the device. Therefore, it has been difficult to accurately extract a signal that can be replaced with a position signal from the arc sound that contains many electrical or mechanical disturbances. In addition, in order to prevent the effects of vibration noise caused by the weaving operation of the torch on the microphone, there are restrictions on microphone installation, such as increasing the rigidity of the microphone mounting part and ensuring accurate positioning of the left and right end microphones. There was a problem.

The present invention has been made in view of the above points, and its purpose is to provide a welding line tracing control that is not affected by background noise and electrical disturbances, and that is practical and easy to use. Our goal is to provide a good welding line copying device.

[Means for Solving Problem 11111] In order to achieve the above object, the present invention is configured to superimpose an alternating current signal of a predetermined frequency on the welding current. Furthermore, the welding line is traced by detecting the welding arc sound at this frequency using a microphone and detecting the amplitude of the arc sound.

[Operation] The shape of the arc varies depending on the feeding fluctuation of the welding wire or the welding conditions. Therefore, it has been experimentally known that the arc sound generated along with this also includes a large number of pulsations. Therefore, the method of detecting a weld line using the arc sound itself has a low signal-to-noise ratio (signal/noise) and is inferior in reliability. In the present invention, the S/N ratio can be increased by applying a superimposed signal to the arc from the outside, and experiments have shown that the amplitude of the arc sound pressure corresponding to the frequency of this superimposed signal is an effective signal for detecting weld lines. Depends on what you confirm. Furthermore, the amplitude corresponding to the frequency of this superimposed signal is not affected by background sounds around the device, and results have been obtained that are extremely resistant to external disturbances. Furthermore, in the present invention, for example, the fillet temperature tangent is used as an example, but the amplitude of the arc sound pressure detected by the microphone is determined by the sum of the direct sound from the arc and the reflected sound, and this is the sum of the direct sound from the arc and the reflected sound. This is based on experimental results that correlate with torch misalignment (especially changes in reflected sound).

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a weld line copying device according to the present invention. In FIG. 1, a welding power source 1 supplies power to a welding torch 2 and a workpiece 3 to generate an arc 5 between a wire 4 and the workpiece 3. An oscillator 6 is connected to, for example, the welding power source 1, and oscillates an alternating current signal of a constant frequency to be superimposed on the arc 5.

A microphone 7 is provided integrally with the welding torch 2 as shown in the figure.The electrical signal of the arc sound detected by the microphone 7 is amplified by an amplifier 8 and then input to a bandpass filter 9.

Only an electric signal having a frequency corresponding to the oscillation frequency set by the oscillator 6 passes through the band pass filter 9, and is outputted to the arc sound amplitude extractor 11 via the rectifier 10.

12 is a detector for average arc voltage or average welding current. The amplitude S extracted by the arc sound amplitude detector 11 and the signal E detected by the average arc voltage or average welding current detector 12 are taken into the torch position deviation detector 13. In this embodiment, the signal E is It was taken as the average arc voltage.

The torch position deviation detector 13 includes a reference average arc voltage generator 14 and a comparator 15. Reference arc sound amplitude generator 16
The torch position correction signals ΔX and ΔZ outputted from the torch position correction unit 18 are outputted to the robot body via the robot control device 19, and are used to trace the welding line. It is for controlling.

FIG. 2 shows a case where the aiming position of the welding torch 7 deviates from the welding line (indicated by 0) (ΔXz, ΔX2.ΔXδ).

FIG. 3 is a diagram illustrating the waveforms of the arc sound pressure level P and the average arc voltage E of the case (indicated as ΔZ8).

Figure 2 (a) shows a case where the welding torch 2 is correctly aiming at the welding line, but the arc sound detected by the microphone is generated by the direct sound from the arc 5 and the reflection from the lower plate 21 and upper plate 22. It becomes the sum of 23 reflected sounds. In FIG. 2, the sound reflected from the upper plate will be explained. This reflected sound is usually
The sound is input to the microphone 7 with a predetermined time delay compared to the direct sound of the arc. This is because the sound transmission path becomes longer for direct sound. Therefore (c) → (b) →
As shown in (a), as the welding torch 2 approaches the upper plate 22 side, the transmission path of the reflected sound becomes shorter and the amplitude S of the arc sound increases. On the other hand, FIG. 2(d) shows a case where a positional shift of Δ2 also occurs in the height direction. In this case, the arc length Q increases and the average arc voltage increases accordingly. In addition, as the arc length increases, the arc expands, the direct sound from the arc increases, and the amplitude S of the arc sound increases6.
Therefore, the position in the height direction can be determined by detecting the average arc voltage.

FIG. 3 is a diagram illustrating the relationship between the arc sound amplitude S and the target position X in the lateral direction. The welding line tracing control is a method of correcting the torch position in the X-axis or Y-axis direction so that the extracted arc sound amplitude matches Sa. The arrow indicates the case where the position of the torch has shifted in the height direction.

FIG. 4 is a flowchart of control operations when weld line copying is performed using the weld line copying device of the present invention.

First, the comparator 15 determines whether the predetermined arc voltage E is equal to the reference average arc voltage Ea.

If they are not equal, the torch position correction unit 18 outputs a position correction signal in the height direction Z to the robot control device 19. If the arc voltage E is equal to the reference average arc voltage formula Ea, then the comparator 17 determines whether the arc sound amplitude S is equal to the reference arc sound amplitude Sa. If they are not equal, the torch position correction section 18 outputs a position correction signal in the lateral direction X to the robot control device 19 as described above, and this operation is repeated until the welding is completed.

〔Effect of the invention〕

As explained above, the present invention superimposes an alternating current signal of a predetermined frequency on the welding current, and controls the welding torch so that the amplitude of the arc sound of that frequency matches the reference arc sound amplitude. It is possible to perform high-precision tracing control without the influence of background noise and disturbances caused by the welding arc itself. Furthermore, the configuration of the copying device is simpler than that of conventional systems, and a weld line copying device with excellent reliability can be provided.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a welding line copying device according to the present invention, and FIG. 2 is a diagram showing the welding torch position and arc sound pressure characteristics in order to explain the welding line copying operation shown in FIG. The correspondence diagram, FIG. 3 is a characteristic diagram for explaining the operation, and FIG. 4 is a flow diagram for explaining the operation. 6... Oscillator, 7... Microphone, 8... Amplifier, 9゛... Bandpass filter, 10... Rectifier, 11... Arc sound amplitude detector, 12... Arc voltage or Welding current detector, 13...Torch position deviation detector.

Claims (1)

[Claims] 1. In a welding line copying device, an oscillating means for superimposing an alternating current signal of a predetermined frequency on a welding current, a means for detecting a welding arc sound generated by the oscillating means, and based on the welding arc sound by the detecting means, means for extracting only the amplitude corresponding to the frequency, and means for detecting an average arc voltage or an average welding current, wherein both the amplitude of the arc sound and the average arc voltage or the average welding current each have a constant reference value. A welding line copying device characterized by comprising means for moving a welding torch left and right and up and down so that