Profiling control method, control device, welding power source and recording medium storing a profiling control program for pulse arc welding

Abstract

Provided is a method for controlling a profile of a pulsed arc welding, a control device, a recording medium storing a welding program, and a welding power source, which can extract protrusion change information with high precision even in a case where a pulsed arc welding method is used, without being affected by welding current and arc voltage as pulse shapes, and further, a protrusion length change. A method for controlling a profile of a pulsed arc welding, which uses, 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, which are detected at the time of oscillation, uses a predetermined period Tf as one section, calculates an average value Yn of the electric change amount X for each of the one section, and extracts protrusion change information within a bevel and traces a welding line based on the average value Yn.

Description

Technical Field

[0001] This invention relates to a contour control method, control device, welding power source, and recording medium storing a contour control program for pulsed arc welding. More specifically, it relates to a contour control method, control device, welding power source, and recording medium storing a contour control program for pulsed arc welding, which enables high-precision contour control of the welding line even in pulsed arc welding, in the contour control of the welding line. Background Technology

[0002] Previously, as a method for contour control of welding lines, arc sensors, which are non-contact sensors, were used. Arc sensors utilize the following characteristic: if the distance between the energized point of the welding wire (the contact point between the welding wire and the contact nozzle) and the base material (hereinafter also referred to as "nozzle / base material distance" or "protrusion (extension distance)") changes, the welding current and arc voltage will also change accordingly.

[0003] As a specific application example of an arc sensor, the following method can be used: the welding torch is oscillated within the groove, and the changes in the distance between the welding nozzle and the base material in the groove width direction are read based on the detected changes in welding current and arc voltage. If these changes become symmetrical in the left and right oscillations, it is determined that the welding torch is aiming at the groove center, i.e., the welding line. If these changes become asymmetrical in the left and right oscillations, it is determined that the welding torch has deviated from the welding line, and the oscillation center is controlled to move so that it becomes symmetrical afterward.

[0004] This method uses an arc sensor to monitor the welding current and arc voltage, and determines the torch position based on the electrical changes. However, when the welding current and arc voltage are pulsed waveforms, i.e., when contour control is applied in pulsed arc welding, in addition to the changes in welding current and arc voltage based on the distance between the nozzle and the base material, the periodic changes caused by the pulse are also combined. Therefore, it is impossible to extract electrical change information that is equivalent to the prominent changes with high precision. Compared with the case of not using pulsed arc welding, there is a concern that the contour accuracy of the weld line will be lower.

[0005] As a contour control method for applying this pulsed arc welding method, Patent Document 1 describes a contour control method that tracks the welding line by oscillating the welding torch within the bevel and tracking the electrical change X detected during the oscillation. In this method, the electrical change X includes at least one of the welding current detection signal Io and the arc voltage detection signal Vo as parameters. A predetermined period Tf is used as an interval, and the average value Yn of the electrical change X in each interval is calculated. Based on the average value Yn, the protruding change information within the bevel is extracted to track the welding line.

[0006] Prior art literature

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2020-116595

[0009] However, in the contour control method described in Patent Document 1, even if the protrusion length changes, it may not be possible to extract the part that does not appear in the current change with high precision. There is room for improvement in order to achieve high-precision contour control. Summary of the Invention

[0010] The present invention was made in view of the above-mentioned problems, and its purpose is to provide a contour control method, control device, welding power source, and recording medium for storing the contour control program of pulsed arc welding. Even when pulsed arc welding is used, it will not be affected by the pulsed welding current and arc voltage. Moreover, even if the protrusion length changes, it can extract protrusion change information with high precision for parts that do not actually appear in the current change.

[0011] The above-mentioned objective of the present invention is achieved by the following structure (1) involved in the contour control method for pulsed arc welding.

[0012] (1) A contour control method for pulsed arc welding, wherein in pulsed arc welding where welding current and arc voltage are periodically varied, the welding torch is oscillated within the groove, and the welding line is tracked based on the electrical change X detected during the oscillation.

[0013] The characteristic of the contour control method is that...

[0014] The electrical change X includes at least the welding current detection signal Io, the arc voltage detection signal Vo, the predetermined set voltage Vset, and the predetermined current conversion characteristic value Char, as parameters.

[0015] Using a predetermined period Tf as one interval, calculate the average value Yn of the electrical change X in each of the one intervals.

[0016] Based on the average value Yn, the prominent change information within the bevel is extracted and the welding line is tracked.

[0017] The preferred embodiments of the present invention relating to the contour control method for pulsed arc welding relate to the following (2) to (6). (2) The contour control method for pulsed arc welding according to (1) above, wherein the electrical change quantity X includes a value obtained by multiplying the value of the welding current detection signal Io and the difference between the arc voltage detection signal Vo and the set voltage Vset by the current conversion characteristic value Char. (3) The contour control method for pulsed arc welding according to (1) above, wherein the current conversion characteristic value is predetermined based on a set value of the average welding current. (4) The contour control method for pulsed arc welding according to any one of (1) to (3) above, wherein the period Tf is one pulse cycle or multiple pulse cycles of the electrical change quantity X. (5) The contour control method for pulsed arc welding according to any one of (1) to (3) above, wherein the average value Yn is calculated using the electrical change quantity X filtered by a frequency filter. (6) The pulse arc welding contour control method according to any one of (1) to (3) above, wherein the average value Yn of the electrical change X before one interval during the measurement period is taken as the center value, and a predetermined upper limit range value is added to calculate the upper limit limit value, and a predetermined lower limit range value is subtracted to calculate the lower limit limit value, and a predetermined processing is performed when the average value Yn during the measurement period exceeds the upper limit limit value or is lower than the lower limit limit value.

[0018] The above-mentioned objective of the present invention is achieved by the structure of the control device described below (7). (7) A control device that, in pulsed arc welding where welding current and arc voltage are periodically varied, oscillates the welding torch within the groove and tracks the welding line based on the electrical change X detected during the oscillation.

[0019] The control device is characterized in that...

[0020] The electrical change X includes at least the welding current detection signal Io, the arc voltage detection signal Vo, the predetermined set voltage Vset, and the predetermined current conversion characteristic value Char, as parameters.

[0021] Using a predetermined period Tf as one interval, calculate the average value Yn of the electrical change X in each of the one intervals.

[0022] Control is implemented to extract protruding variation information within the bevel and track the weld line based on the average value Yn.

[0023] The above-mentioned objective of the present invention is achieved by the structure of the welding power source described below (8). (8) A welding power source having the function of oscillating the welding torch within the groove and tracking the welding line based on the electrical change X detected during the oscillation in pulsed arc welding where the welding current and arc voltage are periodically varied and welding is performed.

[0024] The welding power source is characterized by having:

[0025] The power supply department supplies electricity for welding to generate an electric arc;

[0026] The current control unit receives signals such as feed speed command, welding current command, and arc voltage command, and calculates the control quantity of the power supply unit.

[0027] The current detection unit detects the welding current Iw during welding and outputs a welding current detection signal Io; and

[0028] The voltage detection unit detects the arc voltage Vw during welding and outputs an arc voltage detection signal Vo.

[0029] The electrical change X includes at least the welding current detection signal Io, the arc voltage detection signal Vo, the predetermined set voltage Vset, and the predetermined current conversion characteristic value Char, as parameters.

[0030] It also includes: a control unit that takes a predetermined period Tf as an interval, calculates the average value Yn of the electrical change X in each interval, and performs control to extract protruding change information within the bevel and track the welding line based on the average value Yn.

[0031] The above-mentioned object of the present invention is achieved by the following structure (9) relating to a recording medium storing a contour control program for pulsed arc welding. (9) A recording medium storing a contour control program for pulsed arc welding, wherein in pulsed arc welding, welding current and arc voltage are periodically varied, the welding torch is oscillated within the groove, and the welding line is tracked based on the electrical change X detected during the oscillation.

[0032] The recording medium is characterized in that...

[0033] The electrical change X includes at least the welding current detection signal Io, the arc voltage detection signal Vo, the predetermined set voltage Vset, and the predetermined current conversion characteristic value Char, as parameters.

[0034] The following steps are required:

[0035] The steps include: using a predetermined period Tf as one interval, and calculating the average value Yn of the electrical change X for each interval; and

[0036] The steps of extracting prominent change information within the bevel and tracking the welding line based on the average value Yn.

[0037] According to the present invention, the contour control method, control device, welding power source, and recording medium for storing the contour control program of pulsed arc welding can achieve high-precision extraction and high-precision contour control of portions that do not actually appear in the current change even when there is a change in protruding length. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of a welding system capable of implementing one embodiment of the contour-controlled welding involved in the present invention.

[0039] Figure 2 yes Figure 1 The diagram shows the structure of the arc contour control system of the welding system.

[0040] Figure 3A It is a graph that shows the welding current waveform and arc voltage waveform of pulsed arc welding, and the prominent change information extracted from the welding current waveform and arc voltage waveform by conventional control methods.

[0041] Figure 3B It is a graph representing the welding current waveform and arc voltage waveform of pulsed arc welding, and the prominent change information extracted from the welding current waveform and arc voltage waveform by the control method involved in the present invention.

[0042] Figure 4 It is an enlarged view of the detection signals of the input welding current and arc voltage.

[0043] Figure 5A It is a graph showing the welding current waveform and arc voltage waveform under abnormal voltage conditions, and the prominent change information extracted from the welding current waveform and arc voltage waveform by conventional control methods.

[0044] Figure 5B It is a graph representing the welding current waveform and arc voltage waveform under abnormal voltage conditions, and the prominent change information extracted from the welding current waveform and arc voltage waveform by the control method involved in the present invention.

[0045] Figure 5CIt is a graph showing the welding current waveform and arc voltage waveform under abnormal voltage conditions, and the prominent change information extracted from the welding current waveform and arc voltage waveform by a control method of a modified embodiment of the present invention that applies filtering processing using a frequency filter.

[0046] -Symbol Explanation-

[0047] 1. Arc welding system

[0048] 11 Welding Section

[0049] 20 Track Planning Department

[0050] 21 Teaching Data Storage Department

[0051] 22 Teaching Data Analysis Department

[0052] 23. Calibration Calculation Department

[0053] 24 Left and right offset detection unit

[0054] 25 Arc Voltage Command

[0055] 26 Feed rate command

[0056] 30. Department of Electricity Supply

[0057] 31 Current Detection Section

[0058] 32 Voltage Detection Section

[0059] 33 Current Control Unit

[0060] 34 Pulse State Generation Unit

[0061] 35-pulse cycle counter

[0062] 36 Current setting section

[0063] 40 Electrical Change Calculation Unit (Control Device)

[0064] 50 Robot Drive Department

[0065] 100 welding wire (consumable electrode)

[0066] 110 Welding Torch

[0067] 120 welding robots

[0068] 130 feed device

[0069] 140 Protective gas supply device

[0070] 150 welding power supply

[0071] 160 Robot controller (control device)

[0072] 170. Copying device (control device)

[0073] 200 Base material (workpiece to be welded)

[0074] Iw welding current

[0075] Io welding current detection signal

[0076] Ir current setting control signal

[0077] Iset sets the current.

[0078] LL lower limit range value

[0079] Tf is a predetermined period (one pulse interval).

[0080] UL upper limit range value

[0081] Vset sets the voltage

[0082] Vw Arc voltage

[0083] Vo arc voltage detection signal

[0084] Vr Arc Voltage Command Signal

[0085] Fr feed rate command signal

[0086] Pcnt count value

[0087] X Electrical change

[0088] Yn is the average value of the change in electrical quantity X.

[0089] Yn(n-1) is the average value of the electrical change X over one interval.

[0090] Yn(n-1) + UL upper limit value

[0091] Yn(n-1)-LL is the lower limit value. Detailed Implementation

[0092] Hereinafter, an embodiment of the welding system according to the present invention will be described with reference to the accompanying drawings. Furthermore, this embodiment is an example using a welding robot, and the contour control of the present invention is not limited to the structure of this embodiment. For example, the contour control of the present invention can also be incorporated into an automated device using a trolley. In addition, a pulsed arc welding method is used in this embodiment.

[0093] <System Architecture>

[0094] Figure 1 This is a schematic diagram showing a structural example of the 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 source 150, a robot controller 160, and a contouring device 170. In the figure, the contouring device 170 is arranged between the welding power source 150 and the robot controller 160, but the welding power source 150 and the robot controller 160 may also have the function of the contouring device 170.

[0095] The welding power source 150 is connected to the welding electrode via a positive power cable and to the workpiece (hereinafter also referred to as the "base material" or "workpiece") 200 via a negative power cable. This connection is used when welding is performed with opposite polarities; when welding with positive polarity, the welding power source 150 is connected to the base material 200 via a positive power cable and to the welding electrode via a negative power cable. Furthermore, the welding power source 150 and the feed device 130 of the consumable electrode (hereinafter also referred to as the "welding wire") 100 are both connected via signal lines, enabling control of the wire feed speed.

[0096] The welding robot 120 has a welding torch 110 as an end effector. The welding torch 110 has an energizing mechanism (contact nozzle) for energizing the welding wire 100. The welding wire 100 generates an electric arc from its tip by energizing the contact nozzle, and uses this heat to weld the base material 200, which is the object to be welded.

[0097] Furthermore, the welding torch 110 is equipped with a shielding gas nozzle (a mechanism for ejecting shielding gas). The shielding gas can be any of carbon dioxide, argon, or a mixture such as argon and carbon dioxide. Carbon dioxide is more preferably used as the shielding gas, and in the case of a mixed gas, a gas obtained by mixing 10-30% carbon dioxide with argon is more preferably used. The shielding gas is supplied from the shielding gas supply device 140.

[0098] The welding wire 100 used in this embodiment can be either a solid wire welding wire without flux or a flux-cored wire welding wire containing flux. Furthermore, the material of the welding wire 100 is not particularly limited; for example, low-carbon steel, stainless steel, aluminum, or titanium can be used. Moreover, the diameter of the welding wire 100 is not particularly limited. In this embodiment, it is preferable to set the upper limit of the diameter to 1.6 mm and the lower limit to 0.8 mm.

[0099] The robot controller 160 controls the movements of the welding robot 120. The robot controller 160 pre-stores teaching data that determines the welding robot 120's movement mode, welding start position, welding end position, welding conditions, oscillation movements, etc., and instructs the welding robot 120 to control its movements based on this data. Furthermore, according to the teaching data, the robot controller 160 provides welding conditions such as welding current, arc voltage, and feed rate to the welding power source 150 during the welding operation.

[0100] The welding power source 150 supplies power to the welding wire 100 and the workpiece 200 according to instructions from the robot controller 160, thereby generating an electric arc between the welding wire 100 and the workpiece 200. In addition, the welding power source 150 outputs a signal to the feed device 130 to control the speed of feeding the welding wire 100 according to instructions from the robot controller 160.

[0101] <Functional Structure Involved in the Arc Contouring Control System>

[0102] Figure 2 This is a structural diagram of the arc contour control system according to this embodiment. In this embodiment, the workpiece 200 has a bevel. Furthermore, Figure 2 The V-groove shown is one example; the invention can also be applied to other groove shapes or fillet welds. Viewed from the welding travel direction, the welding section 11 is guided by the welding robot 120 to move the welding torch 110 towards... Figure 2 It swings left and right while welding workpiece 200.

[0103] <Functional Structure of Robot Controller>

[0104] The robot controller 160 includes: a teaching data storage unit 21 for storing and saving pre-made teaching data; a teaching data parsing unit 22 for parsing the teaching data; and a trajectory planning unit 20 for generating servo command information for issuing commands to the robot drive unit 50 (servo driver) controlling each axis of the welding robot 120.

[0105] The teaching data storage unit 21 stores teaching data that determines the motion patterns of the welding robot 120. The teaching data is pre-created by the operator using a teaching device (not shown). Alternatively, the creation method can be other than a teaching pendant. For example, the teaching data can be created on a personal computer and stored in the teaching data storage unit 21 via wireless or wired communication.

[0106] The teaching data parsing unit 22, for example, takes the start of welding as an opportunity to retrieve teaching data from the teaching data storage unit 21 and parses the teaching data. Through the parsing of this teaching data, teaching trajectory information and welding condition command information are generated. The teaching trajectory information determines the trajectory of the welding robot 120 during the welding operation, including welding speed, oscillation conditions, etc. Furthermore, the welding condition command information is used to issue commands related to welding current, arc voltage, feed speed, etc., during the welding operation, including arc ON / OFF commands and control commands for various welding conditions. Then, the teaching data parsing unit 22 outputs the generated teaching trajectory information to the trajectory planning unit 20. Additionally, the teaching data parsing unit 22 can also output the generated welding condition command information to the welding power source 150. For example, an arc voltage command signal Vr or a feed speed command signal Fr is output to the welding power source 150 via an arc voltage command 25 or a feed speed command 26, respectively.

[0107] Based on the teaching trajectory information input from the teaching data parsing unit 22, the trajectory planning unit 20 calculates the target position of the welding robot 120 and generates servo command information for controlling each axis of the welding robot 120. Then, the trajectory planning unit 20 outputs the generated servo command information to the robot drive unit 50 of the welding robot 120.

[0108] The welding robot 120 performs actions based on servo command information. Furthermore, the servo command information includes swing position command information to instruct the welding torch 110 to swing. Based on the teaching trajectory information output from the teaching data analysis unit 22 and the protrusion change information output from the electrical change calculation unit 40 (described later), the left-right offset detection unit 24 (described later) detects the left-right offset from the welding line. The correction amount calculation unit 23 (described later) calculates a correction amount for the swing center based on the left-right offset. The trajectory planning unit 20 resets the swing 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.

[0109] <Functional Structure of Welding Power Supply>

[0110] The welding power source 150 includes: a power supply unit 30 that supplies power for generating an electric arc for welding; a current control unit 33 that receives signals such as feed speed commands, welding current commands, or arc voltage commands, and calculates the control quantity 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.

[0111] The power supply unit 30 of the welding power source 150 takes a commercial power supply such as 3-phase 200V as input. According to the error amplification signal output from the current control unit 33 (described later), it performs inverter control on the input AC voltage and outputs arc voltage Vw and welding current Iw through inverter transformer, rectifier, etc. Alternatively, a reactor can be configured to smooth the output voltage.

[0112] The current control unit 33 of the welding power source 150 has the function of setting various parameters related to the welding current flowing through the welding wire 100. In this embodiment, the current control unit 33 determines the pulse welding parameters, such as the pulse current, 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. In addition, the pulse waveform is not particularly limited and can be any of the following: sine wave, trapezoidal shape, or triangular wave.

[0113] Furthermore, the voltage setting signal Vr is compared with the voltage detection signal Vo detected by the voltage detection unit 32, and the difference between the voltage setting signal Vr and the voltage detection signal Vo is amplified. Based on the voltage error amplification signal, the current control unit 33 controls the pulse frequency to keep the length of the arc generated between the tip of the welding wire 100 and the workpiece 200 constant. The command to increase or decrease the welding current is output to the power supply unit 30 as the current setting control signal Ir to control the welding current Iw.

[0114] In other words, the current control unit 33 finely adjusts the welding wire melting speed by controlling the welding current Iw, and performs constant voltage control to keep the distance between the welding nozzle and the base material constant. Furthermore, the current control unit 33 includes a pulse state generation unit 34 and a pulse period counter 35 to determine the duration of a pulse. The pulse period counter 35 receives a pulse signal from the pulse state generation unit 34, starts counting from the start point of the pulse based on the start or end state signal of the pulse, and resets the counter when it moves to the start point of the next pulse. After resetting, it starts counting again and outputs the count value Pcnt to the electrical change calculation unit 40. The electrical change calculation unit 40 determines the duration of a pulse and the start or end of the pulse based on the received count value Pcnt.

[0115] 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 calculation unit 40.

[0116] 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 calculation unit 40.

[0117] <Functional Structure of the Copying Device>

[0118] The contouring device 170 is an example of a control device with the function of controlling contouring, and includes an electrical change calculation unit 40 for extracting information on prominent changes. In this embodiment, at least one electrical change X from the welding current detection signal Io detected by the current detection unit 31 or the arc voltage detection signal Vo detected by the voltage detection unit 32 is input to the electrical change calculation unit 40.

[0119] In this embodiment, as described above, since a pulsed arc welding method is used, the individual detection signals Io and Vo (electrical change X) in the input welding current Iw and arc voltage Vw become Figure 4 The pulse shape shown. Additionally, Figure 4 It is Figure 3A , Figure 3B The image shown is an enlarged portion of a graph representing the changes in the welding current detection signal Io and the arc voltage detection signal Vo relative to time t.

[0120] The electrical change calculation unit 40, based on the following formula (1), sets one period of a predetermined period Tf, for example, one cycle of the pulse of electrical change X, as one interval (in... Figure 4 In the middle, Tf = T n -T n-1 The average value Yn of the electrical change X is calculated. The average value Yn of this interval is transmitted at a transmission cycle determined by the robot controller 160.

[0121] In this embodiment, since it is easy to obtain highly accurate information on prominent changes, the optimal pulse period Tf is set to one cycle, which is defined as one interval. However, for example, one cycle of the transmission period determined by the robot controller 160 can also be set as the period Tf. Furthermore, multiple pulse cycles or multiple cycles of the transmission period determined by the robot controller 160 can also be set as one interval, with the period Tf defined as one interval. For example, two pulse cycles can be set as the period Tf, and this period Tf can be defined as one interval, and the average value Yn can be calculated.

[0122] In addition, the information of Tf during the period is provided to the electrical change calculation unit 40 through the aforementioned count value Pcnt, for example, when one pulse cycle is set as one interval.

[0123] [Number 1]

[0124]

[0125] In addition, in equation (1), X is the change in electricity, and T n -T n-1 It is a predetermined period (Tf), and Yn is the average value of the electrical change X.

[0126] As the signal input to the electrical change calculation unit 40, namely the electrical change X, at least one of the welding current detection signal Io or the arc voltage detection signal Vo is input. Preferably, both the welding current detection signal Io and the arc voltage detection signal Vo are input. Furthermore, as the ratio of the welding current detection signal Io to the arc voltage detection signal Vo, i.e., Io / Vo (the reciprocal of resistance), or as the ratio of the arc voltage detection signal Vo to the welding current detection signal Io, Vo / Io (resistance), it is more preferable to calculate the average value of one pulse interval Tf of a predetermined period. The reason for inputting the welding current detection signal Io and the arc voltage detection signal Vo together will be explained in detail in the <External Characteristics> section below.

[0127] In addition to the welding current detection signal Io and the arc voltage detection signal Vo, at least one of the set voltage Vset or the set current Iset can be input to the electrical change calculation unit 40. That is, the set voltage Vset or the set current Iset is included as an input value. It is preferable to input the set voltage Vset. That is, as shown in the following equation (2), the average value Yn is output as 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.

[0128] [Number 2]

[0129]

[0130] In addition, 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, measured in A / V. The value of Char is not particularly limited; an appropriate value can be set according to the welding conditions. For example, when the average output current is 300A, the recommended value for Char is 40 ± 10 [0.1A / V]. Thus, the current conversion characteristic value Char can be predetermined based on the set value of the average welding current in the welding conditions.

[0131] Here, Figure 3A The diagram shows key changes in conventional control methods that sample the welding current detection signal Io (Figure (a)) and the arc voltage detection signal Vo (Figure (b)) at a given sampling period (e.g., 5 μs) compared to those in Figure (Figure (c)). Furthermore, Figure 3B The welding current detection signal Io (Figure (a)) and the arc voltage detection signal Vo (Figure (b)) are represented by the prominent change information calculated by Equation (1) using the control method of this embodiment (Figure (c)).

[0132] like Figure 3A As shown, according to previous control methods, signal jitter is generated in the signal (waveform information of electrical change X) that becomes the prominent information of change. Conversely, as... Figure 3B As shown, according to the control method of this embodiment, almost no signal jitter is generated in the signal (waveform information of the average value Yn of the electrical change X) which becomes the prominent change information, and the signal can be obtained with high precision.

[0133] The left-right offset detection unit 24 of the robot controller 160 detects the difference between the left and right sides based on the protrusion change information input from the electrical change calculation unit 40, and outputs it to the correction amount calculation unit 23. The correction amount calculation unit 23 calculates the correction amount for the swing center and outputs the correction amount to the trajectory planning unit 20 of the robot controller 160. The calculation method for the left-right offset and the correction amount is not particularly limited. For example, any method can be used, such as detecting the power spectrum, calculating the distance between the contact nozzle and the base material 200 (protrusion length calculation method), or pattern matching method.

[0134] In this embodiment, the power spectrum is detected by detecting the power spectrum of the average value Yn synchronized with the oscillation frequency. This method is based on the fact that the waveform of the time series data (highlighting the change information) of the average value Yn changes at twice the oscillation frequency when the welding torch 110 is oscillated around the welding line. That is, when the welding torch 110 oscillates along the welding line (under normal circumstances), the component of the waveform highlighting the change information at twice the oscillation frequency is the largest. On the other hand, when the welding torch 110 deviates significantly to the right or left from the welding line, the component of the oscillation frequency becomes the largest, and it is difficult to roughly determine the component of the frequency twice the oscillation frequency. Using this characteristic, the left and right displacement of the welding torch position is determined based on the ratio of the oscillation frequency of the power spectrum to the component of the frequency twice the oscillation frequency.

[0135] In this embodiment, the protruding length calculation method calculates the distance between the contact nozzle and the base material 200 when the welding torch 110 is oscillating within the bevel. The position of the welding line is determined based on the position of the welding torch. The distance between the contact nozzle and the base material 200 is calculated by a contour control unit (not shown) based on the detected wire feed speed, welding current Iw, and arc voltage Vw. By drawing a Lissajous figure with the calculated distance between the contact nozzle and the base material 200, the position of the welding torch 110 can be extracted. By comparing it with the normal situation, the left and right deviations from the welding line can be calculated.

[0136] In this embodiment, the pattern matching method extracts the parameters representing the pattern shape (highlighting change information) of the average value Yn, performs pattern recognition on the parameters estimated based on various conditions such as oscillation frequency, circuit inductance, bevel conditions, and welding conditions, and calculates the left and right offsets.

[0137] (Modified example)

[0138] Furthermore, as a variation of this embodiment, it is preferable to input the average value Yn output from the electrical change calculation unit 40 into the prominent change information extraction unit (left / right offset detection unit 24, correction amount calculation unit 23) after filtering it using a frequency filter (not shown). By using the frequency filter, a signal with better accuracy can be obtained. Furthermore, this frequency filter is preferably a low-pass filter, and more preferably a cutoff frequency selected in the range of 10 to 120 Hz.

[0139] Furthermore, in the event of an abnormal voltage, it is preferable that the measurement period (e.g., set as the interval to be measured in the calculation) be included in the electrical change calculation unit 40. Figure 4 T in n -T n-1The average value (Yn(n-1)) before one interval of the period is used as the center value. According to the predetermined upper limit value UL and lower limit value LL (for example, relative to the center value ±20A), the upper limit value (Yn(n-1)+UL) and lower limit value (Yn(n-1)-LL) of the average value Yn are set. If the average value Yn of the calculated period of the test object exceeds the upper limit value (Yn(n-1)+UL) or is lower than the lower limit value (Yn(n-1)-LL), the predetermined control is performed.

[0140] As a specific handling method for situations where the upper or lower limit value is exceeded, for example, regarding the average value Yn during the measurement period, examples include substituting the average value one interval ago (Yn(n-1)), substituting the upper limit value (Yn(n-1)+UL) or the lower limit value (Yn(n-1)-LL), etc., with the average value one interval ago (Yn(n-1)) being the preferred substitute.

[0141] With this control, even when significant abnormal signals are generated in the arc voltage detection signal Vo, it is possible to obtain accurate and prominent change information.

[0142] in addition, Figures 5A-5C This illustrates an example where an abnormal signal was generated in the arc voltage detection signal Vo. More specifically, Figure 5A This section shows the welding current detection signal Io (Figure (a)) and the arc voltage detection signal Vo (Figure (b)), along with key variation information based on conventional control methods for sampling the welding current detection signal Io at a given sampling period (e.g., 5 μs) (Figure (c)). Furthermore, Figure 5B The diagram shows the welding current detection signal Io (Figure (a)) and the arc voltage detection signal Vo (Figure (b)), as well as prominent variation information extracted by the control method of this embodiment, which samples the welding current detection signal Io at a given sampling period (e.g., 5 μs) (Figure (c)). Furthermore, Figure 5C The welding current detection signal Io (Figure (a)) and the arc voltage detection signal Vo (Figure (b)) are represented, along with prominent variation information extracted by the control method of this variant, which samples the welding current detection signal Io at a given sampling period (e.g., 5 μs).

[0143] like Figure 5A As shown, signal jitter is generated by the signal (waveform information of electrical change X) that becomes the prominent change information extracted through conventional control methods. Furthermore, as... Figure 5BAs shown, the signal (waveform information of the average value Yn of the electrical change X) that becomes the prominent change information extracted by the control method of this embodiment corresponds to the abnormal generation part in the arc voltage detection signal Vo, and a pulse-like waveform is observed.

[0144] On the other hand, such as Figure 5C As shown, when the average value Yn of the measured object exceeds the upper or lower limit, the signal (waveform information of the average value Yn of the electrical change X) that becomes the prominent change information extracted by the control method of the modified example of control through predetermined processing does not show signal jitter or pulse waveform, and can obtain prominent change information with high accuracy.

[0145] <External characteristics>

[0146] In pulsed arc welding, a method exists where, as an external characteristic, a drooping characteristic is selected, resulting in an output characteristic where the current remains almost unchanged even with voltage variations. The stability of the pulse period and the arc is achieved by optimizing the slope of this drooping characteristic. However, when the external characteristic is set to a drooping characteristic, the change in welding current with variations in the protrusion length is smaller than in the case of a constant voltage characteristic (an output characteristic where the voltage remains almost unchanged even with current variations). Therefore, in conventional methods of arc contour control based on the behavior of the welding current, even with advantages in welding operability, accurate arc contour control cannot be obtained.

[0147] In the contour control method described in this embodiment, the output characteristics of the external characteristic are not particularly limited. For example, even using any characteristic among constant voltage, constant current, and droop characteristics, high-precision arc contour control can be achieved. Furthermore, to achieve the aforementioned pulse period and arc stability, a characteristic close to the droop characteristic is preferred. Specifically, it is more preferable to set the slope of the external characteristic within the range of -1V / 100A to -15V / 100A, and even more preferably within the range of -3V / 100A to -12V / 100A.

[0148] Furthermore, the present invention is not limited to the aforementioned embodiments and can be appropriately modified or improved. For example, in this embodiment, such as Figure 2 As shown, in the arc welding system 1, the contouring device 170, which has the function of controlling contouring, is set separately from the welding power source 150 and the robot controller 160. However, even if the control unit with such function is set inside the welding power source 150 and the robot controller 160, the same effect can be obtained.

[0149] As stated above, the following matters are disclosed in this specification.

[0150] (1) A contour control method for pulsed arc welding, wherein in pulsed arc welding where welding current and arc voltage are periodically varied, the welding torch is oscillated within the groove, and the welding line is tracked based on the electrical change X detected during the oscillation.

[0151] The characteristic of the contour control method is that...

[0152] The electrical change X includes at least the welding current detection signal Io, the arc voltage detection signal Vo, the predetermined set voltage Vset, and the predetermined current conversion characteristic value Char, as parameters.

[0153] Using a predetermined period Tf as one interval, calculate the average value Yn of the electrical change X in each of the one intervals.

[0154] Based on the average value Yn, the prominent change information within the bevel is extracted and the welding line is tracked.

[0155] According to this structure, even when using pulsed arc welding, it will not be affected by the pulsed welding current and arc voltage, thus highlighting the length change. It can also extract the highlight change information with high precision for parts that do not actually show current change.

[0156] (2) According to the contour control method for pulsed arc welding described in (1) above, wherein,

[0157] The electrical change X includes at least the sum of the value obtained by multiplying the value of the welding current detection signal Io and the difference between the arc voltage detection signal Vo and the set voltage Vset by the current conversion characteristic value Char.

[0158] Based on this structure, the average value Yn of the electrical change X, which takes into account the difference between the detected voltage and the set voltage, can be calculated.

[0159] (3) According to the contour control method for pulsed arc welding described in (1) above, wherein,

[0160] The current conversion characteristic value is predetermined based on the set value of the average welding current.

[0161] Based on this structure, 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.

[0162] (4) The contour control method for pulsed arc welding according to any one of (1) to (3) above, wherein,

[0163] The period Tf is one pulse cycle or multiple pulse cycles of the electrical change X.

[0164] Based on this structure, highly accurate information on prominent changes can be obtained.

[0165] (5) The contour control method according to any one of (1) to (3) above, wherein the average value Yn is calculated using the electrical change X after being filtered by the frequency filter.

[0166] Based on this structure, highly accurate information on prominent changes can be obtained.

[0167] (6) The contour control method according to any one of (1) to (3) above, wherein,

[0168] The upper limit value is calculated by adding the average value Yn of the electrical change X before one interval during the measurement period to the center value, and the lower limit value is calculated by subtracting the predetermined lower limit value.

[0169] If the average value Yn during the measurement period exceeds the upper limit or falls below the lower limit, a predetermined process is performed.

[0170] Based on this structure, even when abnormal voltages are generated by the arc voltage, it is possible to obtain highly accurate information on significant changes.

[0171] (7) A control device, in pulsed arc welding where welding current and arc voltage are periodically varied, oscillates the welding torch within the groove and tracks the welding line based on the electrical change X detected during the oscillation.

[0172] The control device is characterized in that...

[0173] The electrical change X includes at least the welding current detection signal Io, the arc voltage detection signal Vo, the predetermined set voltage Vset, and the predetermined current conversion characteristic value Char, as parameters.

[0174] Using a predetermined period Tf as one interval, calculate the average value Yn of the electrical change X in each of the one intervals.

[0175] Control is performed based on the average value Yn to extract prominent change information within the bevel and track the weld line.

[0176] According to this structure, it is not affected by pulsed welding current and arc voltage, thus highlighting length changes. It can also extract highlight change information with high precision for parts where there is no actual current change.

[0177] (8) A welding power source, comprising, in pulsed arc welding where welding current and arc voltage are periodically varied, oscillating the welding torch within the groove and tracking the welding line based on the electrical change X detected during the oscillation,

[0178] The welding power source is characterized by having:

[0179] The power supply department supplies electricity for welding to generate an electric arc;

[0180] The current control unit receives signals such as feed speed command, welding current command, and arc voltage command, and calculates the control quantity of the power supply unit.

[0181] The current detection unit detects the welding current Iw during welding and outputs a welding current detection signal Io; and

[0182] The voltage detection unit detects the arc voltage Vw during welding and outputs an arc voltage detection signal Vo.

[0183] The electrical change X includes at least the welding current detection signal Io, the arc voltage detection signal Vo, the predetermined set voltage Vset, and the predetermined current conversion characteristic value Char, as parameters.

[0184] It also includes a control unit that takes a predetermined period Tf as an interval, calculates the average value Yn of the electrical change X in each interval, and performs control based on the average value Yn to extract the protruding change information within the bevel and track the welding line.

[0185] According to this structure, even when using pulsed arc welding, it will not be affected by the pulsed welding current and arc voltage, thus highlighting the length change. It can also extract the highlight change information with high precision for parts that do not actually show current change.

[0186] (9) A recording medium storing a contour control program for pulsed arc welding, the contour control program having the function of oscillating the welding torch within the groove during pulsed arc welding, in which welding current and arc voltage are periodically varied, and tracking the welding line based on the electrical change X detected during said oscillation.

[0187] The recording medium is characterized in that...

[0188] The electrical change X includes at least the welding current detection signal Io, the arc voltage detection signal Vo, the predetermined set voltage Vset, and the predetermined current conversion characteristic value Char, as parameters.

[0189] have:

[0190] The steps include: using a predetermined period Tf as one interval, and calculating the average value Yn of the electrical change X for each interval; and

[0191] Control is performed based on the average value Yn to enable the extraction of prominent variation information within the bevel and the tracking of the weld line.

[0192] According to this structure, even when using pulsed arc welding, it will not be affected by the welding current and arc voltage as pulse shapes, thus highlighting the length change. It can also extract the highlight change information with high precision for parts where there is no actual current change.

Claims

1. A contour control method for pulsed arc welding, wherein in pulsed arc welding where welding current and arc voltage are periodically varied, the welding torch is oscillated within the groove, and the welding line is tracked based on the electrical change X detected during the oscillation. The characteristic of the contour control method is that... The electrical change X includes at least the welding current detection signal Io, the arc voltage detection signal Vo, the predetermined set voltage Vset, and the predetermined current conversion characteristic value Char, as parameters. Using a predetermined period Tf as one interval, calculate the average value Yn of the electrical change X in each of the one intervals. Based on the average value Yn, the prominent change information within the bevel is extracted and the welding line is tracked.

2. The contour control method for pulsed arc welding according to claim 1, wherein, The electrical change X includes at least the value obtained by multiplying the value of the welding current detection signal Io and the difference between the arc voltage detection signal Vo and the set voltage Vset by the current conversion characteristic value Char.

3. The contour control method for pulsed arc welding according to claim 1, wherein, The current conversion characteristic value is predetermined based on the set value of the average welding current.

4. The contour control method for pulsed arc welding according to any one of claims 1 to 3, wherein, The period Tf is one pulse cycle or multiple pulse cycles of the electrical change X.

5. The contour control method for pulsed arc welding according to any one of claims 1 to 3, wherein, The average value Yn is calculated using the electrical change X after being filtered by a frequency filter.

6. The contour control method for pulsed arc welding according to any one of claims 1 to 3, wherein, The upper limit value is calculated by adding the average value Yn of the electrical change X before one interval during the measurement period to the center value, and the lower limit value is calculated by subtracting the predetermined lower limit value. If the average value Yn during the measurement period exceeds the upper limit or falls below the lower limit, a predetermined process is performed.

7. A control device for pulsed arc welding, wherein welding current and arc voltage are periodically varied, wherein a welding torch is oscillated within the groove, and the welding line is tracked based on an electrical change X detected during the oscillation. The control device is characterized in that... The electrical change X includes at least the welding current detection signal Io, the arc voltage detection signal Vo, the predetermined set voltage Vset, and the predetermined current conversion characteristic value Char, as parameters. Using a predetermined period Tf as one interval, calculate the average value Yn of the electrical change X in each of the one intervals. Control is implemented to extract protruding variation information within the bevel based on the average value Yn and to track the weld line.

8. A welding power source comprising, in pulsed arc welding where welding current and arc voltage are periodically varied, oscillating a welding torch within a groove, and tracking the welding line based on an electrical change X detected during the oscillation. The welding power source is characterized by having: The power supply department supplies electricity for welding to generate an electric arc; The current control unit receives signals such as feed speed command, welding current command, and arc voltage command, and calculates the control quantity of the power supply unit. The current detection unit detects the welding current Iw during welding and outputs a welding current detection signal Io. as well as The voltage detection unit detects the arc voltage Vw during welding and outputs an arc voltage detection signal Vo. The electrical change X includes at least the welding current detection signal Io, the arc voltage detection signal Vo, the predetermined set voltage Vset, and the predetermined current conversion characteristic value Char, as parameters. It also has a control unit that takes a predetermined period Tf as an interval, calculates the average value Yn of the electrical change X in each interval, and performs control so that the protruding change information in the bevel is extracted based on the average value Yn and the welding line is tracked.

9. A recording medium storing a contour control program for pulsed arc welding, wherein in pulsed arc welding, welding current and arc voltage are periodically varied, the welding torch is oscillated within the groove, and the welding line is tracked based on the electrical change X detected during the oscillation. The recording medium is characterized in that... The electrical change X includes at least the welding current detection signal Io, the arc voltage detection signal Vo, the predetermined set voltage Vset, and the predetermined current conversion characteristic value Char, as parameters. The following steps are required: The steps include: taking a predetermined period Tf as one interval, and calculating the average value Yn of the electrical change X for each interval; and... The steps involve extracting prominent variation information within the bevel and tracking the weld line based on the average value Yn.

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