Method for controlling the tracing of pulsed arc welding, control device, welding power supply, and tracing control program for pulsed arc welding.

Abstract

The present invention provides a pulsed arc welding tracing control method, control device, welding system, welding program, and welding power supply that, even when using the pulsed arc welding method, are not affected by the pulse shape of the welding current and arc voltage, and furthermore, enable the extraction of highly accurate information on the change in protrusion length, even for portions that do not actually appear as changes in current. [Solution] A pulsed arc welding tracking control method in which the amount of electrical change X detected during weaving includes at least a welding current detection signal Io, an arc voltage detection signal Vo, a predetermined set voltage Vset, and a predetermined current conversion characteristic value Char as parameters, a predetermined period Tf is defined as one interval, the average value Yn of the amount of electrical change X in each interval is calculated, and based on the average value Yn, information on the protrusion change in the groove is extracted to track the weld line.

Description

Technical Field

[0001] The present invention relates to a method for controlling the tracking of pulsed arc welding, a control device, a welding power source, and a program for controlling the tracking of pulsed arc welding. More specifically, the present invention relates to a method for controlling the tracking of pulsed arc welding, a control device, a welding power source, and a program for controlling the tracking of pulsed arc welding, which enables highly accurate tracking control of the weld line even in pulsed arc welding.

Background Art

[0002] Conventionally, an arc sensor, which is a non-contact sensor, has been used as a method for controlling the tracking of a weld line. When the distance between the energized point of the welding wire (the contact point between the welding wire and the contact tip) and the base material (hereinafter also referred to as "distance between the tip and the base material" or "protrusion") changes, the arc sensor utilizes the characteristic that the welding current and the arc voltage change accordingly. As a specific application example of the arc sensor, the welding torch is weaved within the groove, and the change in the distance between the tip and the base material in the groove width direction is read from the detected changes in the welding current and the arc voltage. If these changes are symmetric in the behavior on the left and right sides of the weaving, it is determined that the torch is aimed at the center of the groove, that is, the weld line. If these changes are asymmetric in the behavior on the left and right sides of the weaving, it is determined that the torch is off the weld line, and then the control is performed to move the weaving center so as to be symmetric.

[0003] As described above, the arc sensor is a method of monitoring the welding current and the arc voltage and determining the torch position from the amount of electrical change. However, when the welding current and the arc voltage have a pulsed waveform, that is, when the tracking control is applied to the pulsed arc welding method, in addition to the changes in the welding current and the arc voltage due to the distance between the tip and the base material, the periodic changes due to the pulses are also combined. Therefore, it is impossible to accurately extract the electrical change information corresponding to the protrusion change, and there is a risk that the tracking accuracy of the weld line may be lower than when the pulsed arc welding method is not used. <00000​ Patent Document 1 describes a tracking control method when this pulsed arc welding method is applied, in which the welding torch is weaved within the groove and the welding line is tracked based on the amount of electrical change X detected during weaving. The amount of electrical change X includes at least one of the welding current detection signal Io and the arc voltage detection signal Vo as parameters, and a predetermined period Tf is defined as one section, and the average value Yn of the amount of electrical change X in each section is calculated, and based on the average value Yn, information on the change in protrusion within the groove is extracted and the welding line is tracked. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-116595 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, the tracing control method described in Patent Document 1 may not be able to accurately extract the portion of the current change that does not actually appear in the current change, even if the protrusion length changes, and there was room for improvement in order to achieve high-precision tracing control.

[0007] The present invention has been made in view of the aforementioned problems, and its purpose is to provide a pulsed arc welding tracing control method, control device, welding power supply, and pulsed arc welding tracing control program that, even when using the pulsed arc welding method, are not affected by the pulsed shape of the welding current and arc voltage, and furthermore, enable highly accurate extraction of protrusion change information even for portions where the protrusion length changes and does not actually appear in the current change. [Means for solving the problem]

[0008] The above objective of the present invention is achieved by the configuration described in (1) below, relating to a method for controlling the tracing of pulsed arc welding. (1) In pulse arc welding, in which welding is performed by periodically changing the welding current and arc voltage, a tracing control method is used in which the welding torch is weaved within the groove and the welding line is followed by the amount of electrical change X detected during the weaving, The aforementioned electrical change amount X includes, as parameters, at least, a welding current detection signal Io, an arc voltage detection signal Vo, a predetermined set voltage Vset, and a predetermined current conversion characteristic value Char. A predetermined period Tf is defined as one interval, and the average value Yn of the electrical change X in each interval is calculated. A method for controlling the tracking of pulsed arc welding, characterized by extracting information on the change in protrusion within the groove based on the average value Yn and tracking the weld line.

[0009] Preferred embodiments of the present invention relating to a tracing control method for pulsed arc welding are described below (2) to (6). (2) The amount of electrical change X is the value of the welding current detection signal Io, The difference between the arc voltage detection signal Vo and the set voltage Vset is multiplied by the current conversion characteristic value Char, The method for controlling the tracing of pulsed arc welding according to (1) above, characterized in that it includes a value obtained by adding at least the above. (3) The method for controlling the tracing of pulsed arc welding according to (1) above, characterized in that the current conversion characteristic value is predetermined based on the set value of the average welding current. (4) The pulse arc welding tracing control method according to any one of (1) to (3) above, wherein the period Tf is one pulse period or multiple pulse periods of the electrical change amount X. (5) A method for controlling the tracing of pulsed arc welding according to any one of (1) to (3) above, wherein the average value Yn is calculated using the amount of electrical change X filtered by a frequency filter. (6) Using the average value Yn of the electrical change amount X in the preceding interval of the measurement period as the central value, the upper limit value is calculated by adding a predetermined upper limit range value and the lower limit value is calculated by subtracting a predetermined lower limit range value. A pulse arc welding tracing control method according to any one of (1) to (3) above, wherein if the average value Yn for the measurement period exceeds the upper limit value or falls below the lower limit value, a predetermined process is performed.

[0010] The above objective of the present invention is achieved by the configuration of the control device described in (7) below. (7) In pulse arc welding, in which welding is performed by periodically changing the welding current and arc voltage, a control device is used to weave the welding torch within the groove and to track the welding line based on the amount of electrical change X detected during the weaving, The aforementioned electrical change amount X includes, as parameters, at least, a welding current detection signal Io, an arc voltage detection signal Vo, a predetermined set voltage Vset, and a predetermined current conversion characteristic value Char. A predetermined period Tf is defined as one interval, and the average value Yn of the electrical change X in each interval is calculated. A control device characterized by extracting information on the change in protrusion within the groove based on the average value Yn and controlling it to follow the weld line.

[0011] The above objective of the present invention is achieved by the following configuration (8) relating to the welding power source. (8) A welding power supply that, in pulse arc welding in which welding is performed by periodically changing the welding current and arc voltage, has a function to weave the welding torch in the groove and track the welding line based on the amount of electrical change X detected during the weaving, A power supply unit that supplies power to generate an arc and perform welding, A current control unit receives signals such as feed rate commands, welding current commands, and arc voltage commands, and calculates the control amount for the power supply unit. A current detection unit that detects the welding current Iw during welding and outputs a welding current detection signal Io, A voltage detection unit that detects the arc voltage Vw during welding and outputs an arc voltage detection signal Vo, The electrical change amount X includes at least the welding current detection signal Io, the arc voltage detection signal Vo, a predetermined set voltage Vset, and a predetermined current conversion characteristic value Char as parameters. Taking a predetermined period Tf as one section, an average value Yn of the electrical change amount X for each such section is calculated. A control unit that extracts protrusion change information in the weld pool based on the average value Yn and controls to follow the weld line. A welding power source characterized by comprising the above.

[0012] The above object of the present invention is achieved by the configuration of the following (9) related to the imitation control program of pulsed arc welding. (9) In pulsed arc welding where the welding current and arc voltage are periodically changed for welding, the welding torch is wobbled in the weld pool, and an imitation control program for following the weld line from the electrical change amount X detected during the wobbling, wherein The electrical change amount X includes at least the welding current detection signal Io, the arc voltage detection signal Vo, a predetermined set voltage Vset, and a predetermined current conversion characteristic value Char as parameters. Taking a predetermined period Tf as one section, a step of calculating an average value Yn of the electrical change amount X for each such section. A step of extracting protrusion change information in the weld pool based on the average value Yn and following the weld line. An imitation control program for pulsed arc welding, characterized by comprising the above.

Effects of the Invention

[0013] According to the imitation control method, control device, welding power source, and imitation control program for pulsed arc welding of the present invention, high-precision imitation control that can accurately extract the portion that did not appear in the actual current change even when the protrusion length changes can be realized.

Brief Description of the Drawings

[0014] [Figure 1]Figure 1 is a schematic diagram of a welding system according to one embodiment that can perform contour control welding according to the present invention. [Figure 2] Figure 2 is a diagram illustrating the configuration of the arc tracing control system for the welding system shown in Figure 1. [Figure 3A] Figure 3A is a graph showing the welding current waveform and arc voltage waveform of pulsed arc welding, and the protrusion change information extracted from the welding current waveform and arc voltage waveform using a conventional control method. [Figure 3B] Figure 3B is a graph showing the welding current waveform and arc voltage waveform of pulsed arc welding, and the protrusion change information extracted from the welding current waveform and arc voltage waveform by the control method according to the present invention. [Figure 4] Figure 4 is a magnified view of the detection signals for the input welding current and arc voltage. [Figure 5A] Figure 5A is a graph showing the welding current waveform and arc voltage waveform when an abnormal voltage occurs, and the protrusion change information extracted from the welding current waveform and arc voltage waveform using a conventional control method. [Figure 5B] Figure 5B is a graph showing the welding current waveform and arc voltage waveform when an abnormal voltage occurs, and the protrusion change information extracted from the welding current waveform and arc voltage waveform by the control method according to the present invention. [Figure 5C] Figure 5C is a graph showing the welding current waveform and arc voltage waveform when an abnormal voltage occurs, and the protrusion change information extracted from the welding current waveform and arc voltage waveform by a modified control method of the present invention that applies filtering processing by a frequency filter. [Modes for carrying out the invention]

[0015] Hereinafter, an embodiment of the welding system according to the present invention will be described with reference to the drawings. Note that this embodiment is an example using a welding robot, and the tracing control of the present invention is not limited to the configuration of this embodiment. For example, the tracing control of the present invention may be incorporated into an automated device using a trolley. Furthermore, this embodiment uses a pulsed arc welding method.

[0016] <System Configuration> Figure 1 is a schematic diagram showing an example configuration of an arc welding system 1 according to this embodiment. The arc welding system 1 includes a welding robot 120, a feed device 130, a shielding gas supply device 140, a welding power supply 150, a robot controller 160, and a tracing device 170. In the figure, the tracing device 170 is placed between the welding power supply 150 and the robot controller 160, but the functions of the tracing device 170 may be assigned to the welding power supply 150 or the robot controller 160.

[0017] The welding power supply 150 is connected to the welding electrode via a positive power cable and to the workpiece (hereinafter also referred to as "base material" or "work") 200 via a negative power cable. This connection is for when welding is performed with reverse polarity. When welding is performed with positive polarity, the welding power supply 150 is connected to the base material 200 via a positive power cable and to the welding electrode via a negative power cable. The welding power supply 150 is also connected to the feeder 130 of the consumable electrode (hereinafter also referred to as "welding wire") 100 via a signal line, and the feeding speed of the welding wire 100 can be controlled.

[0018] The welding robot 120 is equipped with a welding torch 110 as an end effector. The welding torch 110 has an energizing mechanism (contact tip) that energizes the welding wire 100. The welding wire 100 generates an arc from its tip when energized from the contact tip, and the heat from this arc welds the base material 200 that is to be welded.

[0019] Furthermore, the welding torch 110 is equipped with a shielding gas nozzle (a mechanism for ejecting shielding gas). The shielding gas may be carbon dioxide, argon gas, or a mixed gas such as argon gas + carbon dioxide. It is more preferable to use carbon dioxide as the shielding gas, and in the case of a mixed gas, it is more preferable to use a gas which is argon gas mixed with 10-30% carbon dioxide. The shielding gas is supplied from the shielding gas supply device 140.

[0020] The welding wire 100 used in this embodiment may be either a solid wire without flux or a flux-cored wire containing flux. Furthermore, the material of the welding wire 100 is not particularly limited; for example, mild steel, stainless steel, aluminum, and titanium can be used. The diameter of the welding wire 100 is also not particularly limited. In this embodiment, preferably, the upper limit of the diameter is 1.6 mm and the lower limit is 0.8 mm.

[0021] The robot controller 160 controls the operation of the welding robot 120. The robot controller 160 holds predefined teaching data for the welding robot 120, including its operation pattern, welding start position, welding end position, welding conditions, weaving motion, etc., and controls the operation of the welding robot 120 by instructing it to use this data. The robot controller 160 also provides the welding power supply 150 with welding conditions such as welding current, arc voltage, and feed rate during the welding operation, according to the teaching data.

[0022] The welding power supply 150, in response to a command from the robot controller 160, supplies power to the welding wire 100 and the workpiece 200, thereby generating an arc between the welding wire 100 and the workpiece 200. The welding power supply 150 also outputs a signal to the wire feeder 130, in response to a command from the robot controller 160, to control the speed at which the welding wire 100 is fed.

[0023] <Functional configuration related to the arc tracing control system> Figure 2 is a configuration diagram relating to the arc tracing control system of this embodiment. In this embodiment, the workpiece 200 has a groove. Note that the V-groove shown in Figure 2 is just one example, and the present invention can be applied to other groove shapes and fillet welds. The welded area 11 is viewed from the direction of welding, and the welding robot 120 weaves the welding torch 110 in the left-right direction in Figure 2 relative to the workpiece 200.

[0024] <Robot Controller Functional Configuration> The robot controller 160 includes a teaching data storage unit 21 that stores pre-created teaching data, a teaching data analysis unit 22 that analyzes the teaching data, and a trajectory planning unit 20 that generates servo command information for issuing commands to the robot drive unit 50 (servo driver) that controls each axis of the welding robot 120.

[0025] The teaching data storage unit 21 stores teaching data that defines the operation patterns of the welding robot 120. The teaching data is created in advance by the operator using a teaching device (not shown). Note that the method of creation does not have to be a teaching pendant. For example, the teaching data may be created on a personal computer and stored in the teaching data storage unit 21 via wireless or wired communication.

[0026] The teaching data analysis unit 22 retrieves teaching data from the teaching data storage unit 21 and analyzes it, for example, when the welding start operation is performed. This analysis of teaching data generates teaching trajectory information and welding condition command information. The teaching trajectory information is information that defines the trajectory of the welding robot 120 during the welding operation, including welding speed, weaving conditions, etc. The welding condition command information is information for issuing commands regarding welding current, arc voltage, feed speed, etc. during the welding operation, and includes control commands for each welding condition, including arc ON / OFF commands. The teaching data analysis unit 22 then outputs the generated teaching trajectory information to the trajectory planning unit 20. The teaching data analysis unit 22 may also output the generated welding condition command information to the welding power supply 150. For example, the arc voltage command signal Vr or the feed speed command signal Fr are output to the welding power supply 150 in response to the arc voltage command 25 or the feed speed command 26, respectively.

[0027] The trajectory planning unit 20 calculates the target position of the welding robot 120 based on the teaching trajectory information input from the teaching data analysis unit 22, and generates servo command information for controlling each axis of the welding robot 120. The trajectory planning unit 20 then outputs the generated servo command information to the robot drive unit 50 of the welding robot 120. The welding robot 120 performs operations based on servo command information. The servo command information also includes weaving position command information for commanding the position where the welding torch 110 will weave. Based on the teaching trajectory information output from the teaching data analysis unit 22 and the protrusion change information output from the electrical change amount calculation unit 40 (described later), the left-right deviation detection unit 24 (described later) detects the amount of left-right deviation from the welding line. The correction amount calculation unit 23 (described later) calculates a correction amount for the weaving center from the left-right deviation amounts. The trajectory planning unit 20 resets the weaving position command information based on the correction amount and outputs the servo command information to the robot drive unit 50 of the welding robot 120.

[0028] <Functional Configuration of Welding Power Supply> The welding power supply 150 includes a power supply unit 30 that supplies power to generate an arc and perform welding, a current control unit 33 that receives signals such as a feed rate command, a welding current command, or an arc voltage command and calculates the control amount of the power supply unit 30, a current detection unit 31 that detects the welding current Iw during welding and outputs a welding current detection signal Io, and a voltage detection unit 32 that detects the arc voltage Vw during welding and outputs an arc voltage detection signal Vo.

[0029] The power supply unit 30 of the welding power supply 150 takes a commercial power supply such as 3-phase 200V as input, and controls the output of the input AC voltage using an inverter control, inverter transformer, rectifier, etc., according to the error amplification signal output from the current control unit 33 (described later), and outputs the arc voltage Vw and welding current Iw. A reactor may also be configured to smooth the output voltage.

[0030] The current control unit 33 of the welding power supply 150 has the function of setting various parameters related to the welding current flowing through the welding wire 100. In this embodiment, the current is a pulsed current, and the current control unit 33 determines the pulse welding parameters such as peak current and base current based on the welding condition command information (arc voltage command 25, feed speed command 26) input from the robot controller 160. The pulse waveform is not particularly limited and may be a sine wave, trapezoidal wave, or triangular wave.

[0031] Furthermore, the voltage setting signal Vr is compared with the voltage detection signal Vo detected by the voltage detection unit 32. The difference between the voltage setting signal Vr and the voltage detection signal Vo is amplified, and the current control unit 33 controls the pulse frequency based on the amplified voltage error signal so that the length of the arc generated between the tip of the welding wire 100 and the workpiece 200 (arc length) remains constant. The current setting control signal Ir is output to the power supply unit 30 as a command to increase or decrease the welding current, thereby controlling the welding current Iw.

[0032] In other words, the current control unit 33 fine-tunes the wire melting speed and performs constant voltage control to keep the tip-base metal distance constant by controlling the welding current Iw. Furthermore, the current control unit 33 includes a pulse state generation unit 34 and a pulse period counter 35 to determine the duration of one pulse. The pulse period counter 35 receives a pulse signal from the pulse state generation unit 34 and, based on the pulse start or end status signal, starts counting from the pulse start point and resets the counter when it moves to the start point of the next pulse. After the reset, it starts counting again and outputs this count value Pcnt to the electrical change amount calculation unit 40. The electrical change amount calculation unit 40 determines the duration of one pulse and the start or end of the pulse based on the received count value Pcnt.

[0033] The current detection unit 31 detects the welding current Iw during welding and outputs a welding current detection signal Io. The welding current detection signal Io is digitally converted by the A / D conversion unit and input to the current control unit 33 and the electrical change amount calculation unit 40.

[0034] The voltage detection unit 32 detects the arc voltage Vw during welding and outputs an arc voltage detection signal Vo. The arc voltage detection signal Vo is digitally converted by the A / D conversion unit and input to the current control unit 33 and the electrical change amount calculation unit 40.

[0035] <Functional configuration of the copying device> The tracing device 170 is an example of a control device that has a function to control tracing, and includes an electrical change amount calculation unit 40 that extracts protrusion change information. In this embodiment, at least one electrical change amount X from the welding current detection signal Io detected from the current detection unit 31 or the arc voltage detection signal Vo detected from the voltage detection unit 32 is input to the electrical change amount calculation unit 40.

[0036] In this embodiment, as described above, a pulsed arc welding method is used, so the detection signals Io and Vo (electrical change amount X) for the input welding current Iw and arc voltage Vw take on a pulse shape as shown in Figure 4. Figure 4 is an enlarged portion of the graphs showing the changes in the welding current detection signal Io and the arc voltage detection signal Vo with respect to time t, as shown in Figures 3A and 3B. The electrical change amount calculation unit 40 calculates based on the following formula (1) a predetermined period Tf, for example, one pulse period of the electrical change amount X is one interval (in Figure 4, Tf = T n -T n-1 The average value Yn of the electrical change X is calculated. This average value Yn for one interval is transmitted to the robot controller 160 at a predetermined transmission period. In this embodiment, the period Tf is set to one pulse cycle, which is the most preferable as it is easier to obtain accurate information on the protrusion change, and is defined as one section. However, for example, one transmission cycle defined in the robot controller 160 may be used as the period Tf. Alternatively, multiple pulse cycles or multiple transmission cycles defined in the robot controller 160 may be used as one section for the period Tf. For example, two pulse cycles may be used as the period Tf, and the average value Yn may be calculated using this period Tf as one section. The information about the period Tf is provided to the electrical change amount calculation unit 40 by the count value Pcnt mentioned above, for example, when one pulse period is considered as one interval.

[0037]

number

[0038] In equation (1), X is the electrical change, and T n -T n-1 is a predetermined period (Tf), and Yn is the average value of the electrical change X.

[0039] At least one of the welding current detection signal Io or the arc voltage detection signal Vo is input to the electrical change amount calculation unit 40 as the electrical change amount X. Preferably, both the welding current detection signal Io and the arc voltage detection signal Vo are input. Furthermore, it is more preferable to calculate the average value of a predetermined pulse interval Tf by using the ratio of the welding current detection signal Io to the arc voltage detection signal Vo, which is Io / Vo (reciprocal of resistance), or the ratio of the arc voltage detection signal Vo to the welding current detection signal Io, which is Vo / Io (resistance). The reason for inputting both the welding current detection signal Io and the arc voltage detection signal Vo will be explained in detail in the <External Characteristics> section below.

[0040] Furthermore, in addition to the welding current detection signal Io and the arc voltage detection signal Vo, at least one signal from the set voltage Vset or set current Iset may be input to the electrical change amount calculation unit 40. That is, the set voltage Vset or set current Iset is included as an input value. Preferably, the set voltage Vset is input. That is, as shown in equation (2) below, when the value obtained by multiplying the difference between the arc voltage detection signal Vo and the set voltage Vset by the current conversion characteristic value Char and the value of the welding current detection signal Io is taken as the electrical change amount X, the average value of the electrical change amount X over a predetermined period Tf is output as the average value Yn.

[0041]

number

[0042] In equation (2), Io is the welding current detection signal, Vo is the arc voltage detection signal, and T n -T n-1Tf is a predetermined period, Vset is a predetermined set voltage, and Yn is the average value of the electrical change X. Char is the current conversion characteristic value, and its unit is [A / V]. The value of the current conversion characteristic value Char is not particularly specified; an appropriate value should be set according to the welding conditions. For example, when the average output current is 300A, the recommended value for the current conversion characteristic value Char is 40±10 [0.1A / V]. In this way, it is preferable to determine the current conversion characteristic value Char in advance based on the set value of the average welding current among the welding conditions.

[0043] Here, Figure 3A shows the welding current detection signal Io ((a) in the figure) and the arc voltage detection signal Vo ((b) in the figure), and the protrusion change information ((c) in the figure) obtained by a conventional control method that samples the welding current detection signal Io at a predetermined sampling period (e.g., 5 μs). Figure 3B also shows the welding current detection signal Io ((a) in the figure) and the arc voltage detection signal Vo ((b) in the figure), and the protrusion change information ((c)) calculated by equation (1) using the control method according to this embodiment. As shown in Figure 3A, with conventional control methods, signal fluctuations occur in the signal that represents the peak change information (waveform information of the electrical change amount X), whereas as shown in Figure 3B, with the control method of this embodiment, signal fluctuations hardly occur in the signal that represents the peak change information (waveform information of the average value Yn of the electrical change amount X), and the signal can be obtained with high accuracy.

[0044] The left-right displacement detection unit 24 of the robot controller 160 detects the difference between the left and right sides according to the protrusion change information input from the electrical change amount calculation unit 40 and outputs it to the correction amount calculation unit 23. The correction amount calculation unit 23 calculates a correction amount relative to the weaving center and outputs the correction amount to the trajectory planning unit 20 of the robot controller 160. The method for calculating the left-right displacement and correction amount is not particularly limited, and any method may be used, for example, a method for detecting the power spectrum, a method for calculating the distance between the contact tip and the base material 200 (protrusion length calculation method), a pattern matching method, etc.

[0045] The method for detecting the power spectrum in this embodiment is to detect the power spectrum of the average value Yn synchronized with the weaving frequency. This method is based on the fact that when the welding torch 110 is oscillated around the weld line, the waveform of the time-series data (protrusion change information) of the average value Yn changes at a frequency twice that of the weaving frequency. That is, when the welding torch 110 is oscillating in accordance with the weld line (normal case), the waveform of the protrusion change information has a maximum component at a frequency twice that of the weaving frequency. On the other hand, when the welding torch 110 deviates significantly to the right or left from the weld line, the component at the weaving frequency becomes maximum, and the component at a frequency twice that of the weaving frequency becomes almost invisible. This characteristic is used to determine the amount of lateral deviation of the torch position from the ratio of the weaving frequency component and the component at a frequency twice that of the weaving frequency in the power spectrum.

[0046] In this embodiment, the projection length calculation method calculates the distance between the contact tip and the base material 200 when the welding torch 110 is oscillated within the groove, and determines the position of the weld line from the torch position. The distance between the contact tip and the base material 200 is calculated by a tracing control unit (not shown) based on the detected wire feeding speed, welding current Iw, and arc voltage Vw. By drawing a Lissajous figure using the calculated distance between the contact tip and the base material 200, the position of the welding torch 110 can be extracted, and by comparing it with the normal case, the amount of lateral deviation from the weld line can be calculated.

[0047] The pattern matching method in this embodiment extracts parameters that represent the pattern shape (protrusion change information) of the average value Yn, and uses these parameters, along with parameters estimated from various conditions such as weaving frequency, circuit inductance, groove conditions, and welding conditions, to perform pattern recognition and calculate the amount of left-right displacement.

[0048] (modified version) Furthermore, as a variation of this embodiment, it is preferable to filter the average value Yn output from the electrical change amount calculation unit 40 with a frequency filter (not shown) before inputting it to the protruding change information extraction unit (left-right shift detection unit 24, correction amount calculation unit 23). By passing the signal through the frequency filter, a more accurate signal can be obtained. Moreover, it is even more preferable that this frequency filter be a low-pass filter with a cutoff frequency selected from the range of 10 to 120 Hz.

[0049] Furthermore, if an abnormal voltage occurs, the electrical change calculation unit 40 calculates the measurement target period, which is the interval being calculated (for example, T in Figure 4). n -T n-1 It is preferable to use the mean value (Yn(n-1)) from the previous interval of the period (defined as the period) as the central value, and to set upper limit values ​​(Yn(n-1)+UL) and lower limit values ​​(Yn(n-1)-LL) for the mean value Yn according to predetermined upper limit value UL and lower limit value LL (for example, ±20A relative to the central value), and to control the predetermined processing when the calculated mean value Yn for the measurement period exceeds the upper limit control value (Yn(n-1)+UL) or falls below the lower limit control value (Yn(n-1)-LL).

[0050] Specific actions to be taken when the upper or lower control limit is exceeded include, for example, substituting the average value Yn for the measurement period with the average value from the previous interval (Yn(n-1)), the upper limit (Yn(n-1)+UL), or the lower limit (Yn(n-1)-LL). Preferably, it is best to substitute with the average value from the previous interval (Yn(n-1)).

[0051] By controlling it in this way, even when a significant abnormal signal occurs in the arc voltage detection signal Vo, accurate information on the protruding change can be obtained.

[0052] Figures 5A to 5C show examples of cases where an abnormal signal occurs in the arc voltage detection signal Vo. More specifically, Figure 5A shows the welding current detection signal Io ((a) in the figure) and the arc voltage detection signal Vo ((b) in the figure), and the protrusion change information ((c) in the figure) obtained by a conventional control method in which the welding current detection signal Io is sampled at a predetermined sampling period (e.g., 5 μs). Figure 5B shows the welding current detection signal Io ((a) in the figure) and the arc voltage detection signal Vo ((b) in the figure), and the protrusion change information ((c) in the figure) extracted by the control method of this embodiment in which the welding current detection signal Io is sampled at a predetermined sampling period (e.g., 5 μs). Furthermore, Figure 5C shows the welding current detection signal Io ((a) in the figure) and the arc voltage detection signal Vo ((b) in the figure), as well as the protrusion change information extracted by the control method of this modified example, which samples the welding current detection signal Io at a predetermined sampling period (e.g., 5 μs).

[0053] As shown in Figure 5A, the signal representing the protruding change information (waveform information of the electrical change amount X) extracted by the conventional control method exhibits signal fluctuations. Furthermore, as shown in Figure 5B, the signal representing the protruding change information (waveform information of the average value Yn of the electrical change amount X) extracted by the control method of this embodiment shows a pulsed waveform corresponding to the abnormal portion in the arc voltage detection signal Vo. On the other hand, as shown in Figure 5C, the signal (waveform information of the average value Yn of the electrical change amount X) extracted by the modified control method, which controls a predetermined process when the average value Yn over the measurement period exceeds an upper or lower control limit, does not show signal fluctuations or pulse-like waveforms, indicating that highly accurate peak change information can be obtained.

[0054] <External Characteristics> In pulsed arc welding, one method involves selecting a drooping characteristic as the external characteristic, where the current hardly changes even when the voltage changes, and then optimizing the slope of this drooping characteristic to achieve pulse period and arc stability. However, when the external characteristic is set to a drooping characteristic, the change in welding current due to fluctuations in the overhang length is smaller than in the case of a constant voltage characteristic (an output characteristic where the voltage hardly changes even when the current changes). For this reason, conventional methods that control arc tracking based on the behavior of the welding current, while having advantages in welding workability, have not been able to achieve accurate arc tracking control.

[0055] In the tracing control method according to this embodiment, the output characteristics of the external characteristics are not particularly limited, and accurate arc tracing control can be achieved regardless of whether the output characteristics are, for example, constant voltage characteristics, constant current characteristics, or drooping characteristics. In order to achieve the pulse period and arc stability described above, it is preferable to use characteristics close to drooping characteristics. Specifically, it is more preferable to set the slope of the external characteristics in the range of -1V / 100A to -15V / 100A, and even more preferable to set the slope of the external characteristics in the range of -3V / 100A to -12V / 100A.

[0056] It should be noted that the present invention is not limited to the embodiments described above, and can be modified and improved as appropriate. For example, in this embodiment, as shown in Figure 2, a tracing device 170 is provided separately from the welding power supply 150 and the robot controller 160 in the arc welding system 1 to have a function of controlling tracing. However, similar effects can be obtained by providing a control unit with such a function within the welding power supply 150 or the robot controller 160.

[0057] As described above, the following matters are disclosed in this specification:

[0058] (1) In pulse arc welding, in which welding is performed by periodically changing the welding current and arc voltage, a tracing control method is used in which the welding torch is weaved within the groove and the welding line is followed by the amount of electrical change X detected during the weaving, The aforementioned electrical change amount X includes, as parameters, at least, a welding current detection signal Io, an arc voltage detection signal Vo, a predetermined set voltage Vset, and a predetermined current conversion characteristic value Char. A predetermined period Tf is defined as one interval, and the average value Yn of the electrical change X in each interval is calculated. A method for controlling the tracking of pulsed arc welding, characterized by extracting information on the change in protrusion within the groove based on the average value Yn and tracking the weld line. With this configuration, even when using pulsed arc welding, the welding current and arc voltage, which are pulsed in shape, are not affected, and it becomes possible to extract highly accurate information on the change in protrusion length, even for the portion that does not actually appear as a change in current.

[0059] (2) The amount of electrical change X is the value of the welding current detection signal Io, The difference between the arc voltage detection signal Vo and the set voltage Vset is multiplied by the current conversion characteristic value Char, The method for controlling the tracing of pulsed arc welding according to (1) above, characterized in that it includes a value obtained by adding at least the above. This configuration allows for the calculation of the average value Yn of the electrical change amount X, taking into account the difference between the detected voltage and the set voltage.

[0060] (3) The method for controlling the tracing of pulsed arc welding according to (1) above, characterized in that the current conversion characteristic value is predetermined based on the set value of the average welding current. With this configuration, the average value Yn of the electrical change X can be calculated using an appropriate current conversion characteristic value corresponding to the average welding current.

[0061] (4) The pulse arc welding tracing control method according to any one of (1) to (3) above, wherein the period Tf is one pulse period or multiple pulse periods of the electrical change amount X. This configuration allows for obtaining highly accurate information on protrusion changes.

[0062] (5) A tracing control method according to any one of (1) to (3) above, wherein the average value Yn is calculated using the amount of electrical change X filtered by a frequency filter. This configuration allows for obtaining highly accurate information on protrusion changes.

[0063] (6) Using the average value Yn of the electrical change amount X in the preceding interval of the measurement period as the central value, the upper limit value is calculated by adding a predetermined upper limit range value and the lower limit value is calculated by subtracting a predetermined lower limit range value. A tracing control method according to any one of (1) to (3) above, which performs a predetermined process when the average value Yn for the measurement period exceeds the upper limit value or falls below the lower limit value. With this configuration, even when abnormal voltages occur in the arc voltage, accurate information on the spike change can be obtained.

[0064] (7) In pulse arc welding, in which welding is performed by periodically changing the welding current and arc voltage, a control device is used to weave the welding torch within the groove and to track the welding line based on the amount of electrical change X detected during the weaving, The aforementioned electrical change amount X includes, as parameters, at least, a welding current detection signal Io, an arc voltage detection signal Vo, a predetermined set voltage Vset, and a predetermined current conversion characteristic value Char. A predetermined period Tf is defined as one interval, and the average value Yn of the electrical change X in each interval is calculated. A control device characterized by extracting information on the change in protrusion within the groove based on the average value Yn and controlling it to follow the weld line. This configuration allows for the extraction of highly accurate information on changes in the protrusion length, even for changes in the protrusion length that did not actually appear in the current change, without being affected by pulsed welding current or arc voltage.

[0065] (8) A welding power supply that, in pulse arc welding in which welding is performed by periodically changing the welding current and arc voltage, has a function to weave the welding torch in the groove and track the welding line based on the amount of electrical change X detected during the weaving, A power supply unit that supplies power to generate an arc and perform welding, A current control unit receives signals such as feed rate commands, welding current commands, and arc voltage commands, and calculates the control amount for the power supply unit. A current detection unit that detects the welding current Iw during welding and outputs a welding current detection signal Io, A voltage detection unit that detects the arc voltage Vw during welding and outputs an arc voltage detection signal Vo, The electrical change amount X includes, at least, the welding current detection signal Io, the arc voltage detection signal Vo, a predetermined set voltage Vset, and a predetermined current conversion characteristic value Char as parameters. A predetermined period Tf is defined as one interval, and the average value Yn of the electrical change X in each interval is calculated. A control unit that extracts information on the change in protrusion within the groove based on the average value Yn and controls it to follow the weld line, A welding power supply characterized by having the following features. With this configuration, even when using pulsed arc welding, the welding current and arc voltage, which are pulsed in shape, are not affected, and it becomes possible to extract highly accurate information on the change in protrusion length, even for the portion that does not actually appear as a change in current.

[0066] (9) In pulsed arc welding, in which welding is performed by periodically changing the welding current and arc voltage, a tracing control program that weaves the welding torch within the groove and tracks the welding line based on the amount of electrical change X detected during the weaving, The aforementioned electrical change amount X includes, as parameters, at least, a welding current detection signal Io, an arc voltage detection signal Vo, a predetermined set voltage Vset, and a predetermined current conversion characteristic value Char. The steps include: calculating the average value Yn of the electrical change amount X for each predetermined period Tf, and Based on the average value Yn, the step of extracting information on the change in protrusion within the groove and following the weld line, A pulsed arc welding tracing control program characterized by comprising the following features. With this configuration, even when using pulsed arc welding, the welding current and arc voltage, which are pulsed in shape, are not affected, and it becomes possible to extract highly accurate information on the change in protrusion length, even for the portion that does not actually appear as a change in current. [Explanation of Symbols]

[0067] 1. Arc welding system 11 Welded section 20. Track Planning Department 21. Teaching data storage unit 22. Instructional Data Analysis Department 23 Correction amount calculation section 24 Left-right misalignment detection unit 25 Arc Voltage Command 26 Feed speed command 30 Power supply section 31 Current detection unit 32 Voltage detection unit 33 Current control unit 34. Pulse state generation unit 35. Pulse Period Counter 36 Current setting section 40 Electrical change amount calculation unit (control device) 50 Robot drive unit 100 Welding Wire (Consumable Electrode) 110 Welding Torch 120 Welding Robots 130 Feeding device 140 Shielding gas supply device 150 Welding Power Supply 160 Robot Controller (Control Device) 170 Copying device (control device) 200 Base material (workpiece to be welded) Iw welding current Io Welding current detection signal Ir current setting control signal Iset set current LL Lower Limit Range Tf: A predetermined period (one pulse interval) UL Upper Limit Range Value Vset set voltage Vw Arc Voltage Vo arc voltage detection signal Vr Arc voltage command signal Fr Feed speed command signal Pcnt count value X Electrical change Yn: Average value of the electrical change X Yn(n-1) The average value of the electrical change X from the previous interval. Yn(n-1)+UL Upper Limit Yn(n-1)-LL Lower limit value

Claims

1. In pulsed arc welding, in which welding is performed by periodically changing the welding current and arc voltage, a tracing control method is provided in which the welding torch is weaved within the groove, and the welding line is tracked based on the amount of electrical change X detected during the weaving, The aforementioned electrical change amount X includes, at least, a welding current detection signal Io, an arc voltage detection signal Vo, a predetermined set voltage Vset, and a predetermined current conversion characteristic value Char as parameters. A predetermined period Tf is defined as one interval, and the average value Yn of the electrical change X in each interval is calculated. A method for controlling the tracking of pulsed arc welding, characterized by extracting information on the change in protrusion within the groove based on the average value Yn and tracking the weld line.

2. The aforementioned electrical change amount X is the value of the welding current detection signal Io, The difference between the arc voltage detection signal Vo and the set voltage Vset is multiplied by the current conversion characteristic value Char, The method for controlling the tracing of pulsed arc welding according to claim 1, characterized in that it includes a value obtained by adding at least [a certain value].

3. The method for controlling the tracing of pulsed arc welding according to claim 1, characterized in that the current conversion characteristic value is predetermined based on a set value of the average welding current.

4. The pulse arc welding tracing control method according to any one of claims 1 to 3, wherein the period Tf is one pulse period or multiple pulse periods of the electrical change amount X.

5. A method for controlling the tracing of pulsed arc welding according to any one of claims 1 to 3, wherein the average value Yn is calculated using the amount of electrical change X filtered by a frequency filter.

6. The average value Yn of the electrical change amount X in the preceding interval of the measurement period is used as the central value, and an upper limit value is calculated by adding a predetermined upper limit range value, while a lower limit value is calculated by subtracting a predetermined lower limit range value. A pulse arc welding tracing control method according to any one of claims 1 to 3, wherein if the average value Yn for the measurement period exceeds the upper limit value or falls below the lower limit value, a predetermined process is performed.

7. In pulsed arc welding, in which welding is performed by periodically changing the welding current and arc voltage, a control device is used to track the welding line by weaving the welding torch within the groove and detecting an electrical change X during the weaving process. The aforementioned electrical change amount X includes, at least, a welding current detection signal Io, an arc voltage detection signal Vo, a predetermined set voltage Vset, and a predetermined current conversion characteristic value Char as parameters. A predetermined period Tf is defined as one interval, and the average value Yn of the electrical change X in each interval is calculated. A control device characterized by extracting information on the change in protrusion within the groove based on the average value Yn and controlling it to follow the weld line.

8. In pulse arc welding, in which welding is performed by periodically changing the welding current and arc voltage, a welding power supply has a function to weave the welding torch within the groove and track the welding line based on the amount of electrical change X detected during the weaving, A power supply unit that supplies power to generate an arc and perform welding, A current control unit receives signals such as feed rate commands, welding current commands, and arc voltage commands, and calculates the control amount for the power supply unit. A current detection unit that detects the welding current Iw during welding and outputs a welding current detection signal Io, A voltage detection unit that detects the arc voltage Vw during welding and outputs an arc voltage detection signal Vo, The electrical change amount X includes, as parameters, at least, the welding current detection signal Io, the arc voltage detection signal Vo, a predetermined set voltage Vset, and a predetermined current conversion characteristic value Char. A predetermined period Tf is defined as one interval, and the average value Yn of the electrical change X in each interval is calculated. A control unit that extracts information on the change in protrusion within the groove based on the average value Yn and controls it to follow the weld line, A welding power supply characterized by having the following features.

9. In pulsed arc welding, in which welding is performed by periodically changing the welding current and arc voltage, a tracing control program is provided that weaves the welding torch within the groove and tracks the welding line based on the amount of electrical change X detected during the weaving, The aforementioned electrical change amount X includes, at least, a welding current detection signal Io, an arc voltage detection signal Vo, a predetermined set voltage Vset, and a predetermined current conversion characteristic value Char as parameters. The steps include: calculating the average value Yn of the electrical change amount X for each predetermined period Tf, and Based on the average value Yn, the step of extracting information on the change in protrusion within the groove and following the weld line, A pulsed arc welding tracing control program characterized by comprising the following features.

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