Welding equipment

Abstract

To provide a welding apparatus that can flexibly handle the occurrence of overshoot and undershoot. [Solution] The welding apparatus 1 includes a command output unit that outputs a current command based on a target waveform of the welding current output as a pulse signal, a current output unit that outputs a welding current based on the current command output by the command output unit, and a difference calculation unit that compares the output waveform of the welding current output by the current output unit with the target waveform and calculates a first difference between the output waveform and the target waveform at the rising portion of the output waveform and a second difference between the output waveform and the target waveform at the falling portion of the output waveform. The command output unit adjusts the command waveform of the previous current command so that the first difference and the second difference decrease based on the target waveform, the first difference and the second difference, and outputs a current command with the adjusted command waveform as the next current command.

Description

Technical Field

[0001] The present invention relates to a welding apparatus.

Background Art

[0002] Patent Document 1 below discloses an arc welding machine that improves the ripple at the rise of a pulsed current. In this welding machine, when the output of an attenuation circuit that attenuates the output signal of a current command circuit is larger than the welding current, the arc bias of the pulsed current is reduced, enabling the output of a pulsed current without overshoot and without ripple at the rise.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, overshoot at the rise of a pulsed current is a factor causing welding defects such as undercut due to excessive current output and large-sized spatter. On the other hand, undershoot at the fall is a factor causing arc interruption. Therefore, circuit design is carried out so that overshoot and undershoot do not occur. However, since the occurrence of overshoot and undershoot is also affected by the length of the cable in the use environment and reactance due to the routing of the cable, it is difficult to predict the occurrence situation, and it is also difficult to take countermeasures according to the occurrence situation.

[0005] Therefore, an object of the present invention is to provide a welding apparatus capable of flexibly coping with the occurrence of overshoot and undershoot.

Means for Solving the Problems

[0006] A welding apparatus according to one aspect of the present invention includes a command output unit that outputs a current command based on a target waveform of a welding current output as a pulse signal, a current output unit that outputs a welding current based on the current command output by the command output unit, and a difference calculation unit that compares the output waveform of the welding current output by the current output unit with the target waveform and calculates a first difference between the output waveform and the target waveform at the rising portion of the output waveform and a second difference between the output waveform and the target waveform at the falling portion of the output waveform, respectively. The command output unit adjusts the command waveform of the previous current command so that the first difference and the second difference decrease based on the target waveform, the first difference and the second difference, and outputs a current command with the adjusted command waveform as the next current command.

[0007] According to this embodiment, the output waveform of the welding current output by a current command based on the target waveform of the welding current is compared with the target waveform to calculate a first difference in the rising portion of the output waveform and a second difference in the falling portion of the output waveform. The command waveform of the previous current command is adjusted so that the calculated first and second differences decrease, and the next current command is output using the adjusted command waveform.

[0008] In the above embodiment, the command output unit may adjust the previous command waveform by subtracting a current equal to a predetermined percentage of the absolute value of the difference between the peak welding current output by the current output unit and the current that overshot in the rising portion of the previous output waveform from the current in the rising portion of the previous command waveform.

[0009] According to this embodiment, it becomes possible to output a current command obtained by subtracting a predetermined percentage of the current that overshot in the previous rising portion from the command waveform of the next rising portion.

[0010] In the above embodiment, the command output unit may adjust the previous command waveform so that the time it takes for the ripple generated in the rising edge of the previous output waveform to converge to the peak current of the welding current is shortened.

[0011] According to this configuration, it is possible to shorten the convergence time to the peak current compared to the ripple that occurred in the previous rising portion.

[0012] In the above embodiment, the command output unit may adjust the previous command waveform by adding a current equal to a predetermined percentage of the absolute value of the difference between the base current of the welding current output by the current output unit and the current that undershot during the falling edge of the previous output waveform, to the current during the falling edge of the previous current command.

[0013] According to this embodiment, it becomes possible to output a current command in which a predetermined proportion of the current that undershot in the previous falling edge is added to the command waveform of the next falling edge.

[0014] In the above embodiment, the command output unit may adjust the previous command waveform so that the time it takes for the ripple generated in the falling edge of the previous output waveform to converge to the base current of the welding current is shortened.

[0015] According to this configuration, it is possible to shorten the convergence time to the base current compared to the ripple that occurred in the previous falling edge.

[0016] In the above embodiment, the difference calculation unit may calculate the first difference and the second difference using a predetermined number of output waveforms.

[0017] This embodiment makes it possible to improve processing efficiency.

[0018] In the above embodiment, the command output unit may store the adjusted command waveform in the storage unit and, when performing other welding with the same or similar welding conditions, output a current command based on the adjusted command waveform stored in the storage unit.

[0019] According to this embodiment, welding can be performed by using command waveforms generated under other welding conditions. [Effects of the Invention]

[0020] According to the present invention, it is possible to provide a welding apparatus capable of flexibly coping with the occurrence of overshoot and undershoot.

Brief Description of the Drawings

[0021] [Figure 1] It is a figure which illustrates the structure of the robot system containing the welding apparatus which concerns on embodiment. [Figure 2] It is a figure which illustrates a part of functional structure of a welding apparatus. [Figure 3] It is a figure which illustrates a target waveform, an output waveform, and a command waveform. [Figure 4] It is a flowchart for demonstrating an example of operation | movement of the welding apparatus which concerns on embodiment.

Embodiments for Carrying Out the Invention

[0022] Preferred embodiments of the present invention will be described with reference to the accompanying drawings. Note that since the drawings are schematic, dimensions and ratios of each component are different from actual ones.

[0023] FIG. 1 is a diagram illustrating the configuration of a robot system 100 including a welding apparatus 1 according to an embodiment. The robot system 100 includes a welding apparatus 1, a robot control device 2, and a manipulator 3.

[0024] The robot control device 2 is a control unit that controls the operation of the manipulator 3 according to preset welding work conditions.

[0025] The welding work conditions include, for example, data items such as welding conditions, welding start position, welding end position, welding distance, welding torch posture, and the like. The welding conditions include, for example, data items such as welding current, welding voltage, welding speed, wire feeding speed, and workpiece thickness.

[0026] Manipulator 3 is a welding robot that operates a multi-jointed robot arm according to the welding conditions set in the robot control device 2, and performs arc welding on the workpiece to be welded.

[0027] The manipulator 3 includes, for example, a multi-joint robotic arm mounted on a base member fixed to the floor of a factory, and a welding torch connected to the tip of the multi-joint robotic arm as one of the work tools. The manipulator 3 also includes, for example, a motor, encoder, reducer, and torque sensor. The motor, encoder, reducer, and torque sensor are provided for each axis that constitutes one of the multiple joints in the robotic arm.

[0028] The welding apparatus 1 is a power supply device that supplies welding current, welding voltage, etc., to the manipulator 3 according to the welding conditions set in the robot control device 2 in order to generate an arc between the tip of the welding wire and the workpiece.

[0029] The welding apparatus 1 includes, for example, a control unit 11, a storage unit 12, and a communication unit 13. The control unit 11 is a processor and controls the welding apparatus 1 by executing a program stored in the storage unit 12.

[0030] The memory unit 12 is a computer-readable recording medium that stores programs for realizing various functions of the welding apparatus 1 and various data used in those programs. The communication unit 13 is a communication interface that controls communication with the robot control device 2 and manipulator 3 connected via a network.

[0031] Figure 2 illustrates a part of the functional configuration of the welding apparatus 1. The welding apparatus 1 has, for example, a command output unit 111, a current output unit 112, and a difference calculation unit 113 as its functional configuration.

[0032] The command output unit 111 generates a command waveform based on the target waveform of the welding current output as a pulse signal. The command output unit 111 then outputs a current command based on the generated command waveform to the current output unit 112. Preferably, the target waveform is stored in the storage unit 12. It is also preferable that the generated command waveform is stored in the storage unit 12.

[0033] The current output unit 112 outputs the welding current required for welding to the welding torch of the manipulator 3 based on the current command output by the command output unit 111. It is preferable to store the waveform of the output welding current (hereinafter also referred to as the "output waveform") in the storage unit 12.

[0034] The difference calculation unit 113 compares the output waveform output by the current output unit 112 with the target waveform. The difference calculation unit 113 then calculates the difference between the waveform at the rising edge of the output waveform and the waveform of the target waveform corresponding to that portion (hereinafter also referred to as the "first difference"), and the difference between the waveform at the falling edge of the output waveform and the waveform of the target waveform corresponding to that portion (hereinafter also referred to as the "second difference"). It is preferable to store the calculated first difference and second difference in the storage unit 12.

[0035] The first difference corresponds to the difference from the peak current due to the occurrence of overshoot, and the second difference corresponds to the difference from the base current due to the occurrence of undershoot. The difference calculation unit 113 feeds back the calculated first and second differences to the command output unit 111. Overshoot is a phenomenon in which the waveform of the current pulse waveform exceeds the baseline of the steady value (peak current) once upward in the rising part before approaching the steady value. Undershoot is a phenomenon in which the waveform of the current pulse waveform exceeds the baseline of the steady value (base current) once downward in the falling part before approaching the steady value.

[0036] Here, when the difference calculation unit 113 calculates the first difference and the second difference, it may use not only one output waveform but also multiple output waveforms. In other words, it may use a predetermined number of output waveforms to calculate the first difference and the second difference. For example, the first difference and the second difference may be calculated for each of the predetermined number of output waveforms, and their averages may be used as the first difference and the second difference.

[0037] The command output unit 111 adjusts the previous command waveform using the first difference and second difference fed back from the difference calculation unit 113, as well as the target waveform, and uses the adjusted waveform as the next command waveform.

[0038] Specifically, the command output unit 111 generates the next command waveform by adjusting the previous command waveform based on the target waveform, the first difference, and the second difference, so that the first difference and the second difference decrease and the next output waveform approaches the target waveform. The command output unit 111 outputs a current command based on the generated next command waveform to the current output unit 112. Preferably, the next command waveform is stored in the storage unit 12.

[0039] Referring to Figure 3, the target waveform, output waveform, and command waveform will be explained in detail. Figure 3(a) shows an example of the target waveform Wa, Figure 3(b) shows an example of the output waveform Wb, and Figure 3(c) shows an example of the command waveform Wc.

[0040] The target waveform Wa is a pulse signal output by alternating between peak current and base current.

[0041] The command waveform Wc is a pulse signal output based on the target waveform Wa. The first command waveform Wc is output as the first target waveform Wa.

[0042] The output waveform Wb is a pulse signal output based on the command waveform Wc. The first output waveform Wb overshoots at the rising edge b1 and undershoots at the falling edge b2. The overshoot and undershoot gradually decrease with each subsequent run.

[0043] The second command waveform Wc is output after the rising edge c1 and falling edge c2 of the waveform have been adjusted based on the overshoot and undershoot of the first output waveform Wb. The amount of adjustment accumulates each time. Therefore, the magnitude of the adjustment in the rising and falling edges of the command waveform Wc gradually increases with each subsequent cycle.

[0044] Here, as a method for adjusting the command waveform Wc so that the first difference in the rising edge decreases, for example, the following (1) and (2) can be used.

[0045] (1) First, the absolute value of the difference between the peak welding current output by the current output unit 112 and the current that overshot in the rising portion of the previous output waveform Wb is calculated. Next, a current that is a predetermined ratio of the calculated absolute value is calculated. Then, the next command waveform Wc is generated by adjusting the previous command waveform Wc by subtracting the calculated current from the current in the rising portion of the previous command waveform Wc.

[0046] This makes it possible to output a current command in which a predetermined percentage of the current that overshot in the previous rising edge is subtracted from the command waveform of the next rising edge.

[0047] The predetermined percentage mentioned above can be set arbitrarily between 0% and 100%. For example, the predetermined percentage may be set to 50%. Increasing the predetermined percentage can shorten the time it takes to converge to the peak current, but it may also increase the amplitude of the fluctuations, potentially reducing stability. Decreasing the predetermined percentage will lengthen the time it takes to converge to the peak current, but it will be possible to suppress the amplitude of the fluctuations.

[0048] (2) The next command waveform Wc is generated by adjusting the previous command waveform Wc so that the time it takes for the ripple generated in the rising edge of the previous output waveform Wb to converge to the peak current is shortened.

[0049] This makes it possible to shorten the convergence time to the peak current compared to the ripple that occurred in the previous rising phase.

[0050] Furthermore, as a method for adjusting the command waveform Wc so that the second difference in the falling edge decreases, for example, the following (3) and (4) can be used.

[0051] (3) First, the absolute value of the difference between the base current of the output current output by the current output unit 112 and the current that undershot during the falling edge of the previous output waveform Wb is calculated. Next, a current that is a predetermined ratio of the calculated absolute value is calculated. Then, the next command waveform Wc is generated by adding the calculated current to the current during the falling edge of the previous command waveform Wc and adjusting the previous command waveform. The predetermined ratio is the same as in (1) above.

[0052] This makes it possible to output a current command in which a predetermined percentage of the current that undershot during the previous falling edge is added to the command waveform of the next falling edge.

[0053] (4) The next command waveform Wc is generated by adjusting the previous command waveform Wc so that the time it takes for the ripple generated in the falling edge of the previous output waveform Wb to converge to the base current is shortened.

[0054] This makes it possible to shorten the convergence time to the base current compared to the ripple that occurred in the previous falling edge.

[0055] Here, the command output unit 111 may read the current command based on the adjusted command waveform stored in the memory unit 12 when performing other welding with the same or similar welding conditions, and output it to the current output unit 112. When outputting the current command based on the read command waveform, the predetermined ratio described above may be adjustable. By adjusting the predetermined ratio, it becomes possible to adjust the time it takes for the current to converge to the peak current or base current.

[0056] Referring to Figure 4, an example of the operation of the welding apparatus 1 will be described. This operation is performed repeatedly as long as the target waveform of the output current continues.

[0057] First, the command output unit 111 of the welding apparatus 1 outputs a current command to the current output unit 112 based on a command waveform generated based on the target waveform of the welding current (step S101).

[0058] Next, the current output unit 112 of the welding apparatus 1 outputs a welding current based on the current command output in step S101 or step S105 described later (step S102).

[0059] Next, the difference calculation unit 113 of the welding apparatus 1 compares the output waveform of the welding current output in step S102 with the target waveform and calculates the first difference and the second difference (step S103).

[0060] Next, the difference calculation unit 113 of the welding apparatus 1 feeds back the first difference and the second difference calculated in step S103 to the command output unit 111 (step S104).

[0061] Next, the command output unit 111 of the welding apparatus 1 outputs a current command to the current output unit 112 based on the first difference and second difference fed back in step S104, the target waveform, and the previous command waveform, which is used to generate the next command waveform (step S105). Then, the process proceeds to step S102.

[0062] As described above, according to the welding apparatus 1 of the embodiment, the output waveform of the welding current output by a current command based on the target waveform of the welding current is compared with the target waveform to calculate a first difference in the rising portion of the output waveform and a second difference in the falling portion of the output waveform. The command waveform of the previous current command is adjusted so that the calculated first and second differences decrease, and the next current command is output using the adjusted command waveform.

[0063] This makes it possible to adjust and output the current command in such cases that an overshoot occurs in the rising part of the welding current, or an undershoot occurs in the falling part of the welding current, so as to reduce the effects of the overshoot or undershoot.

[0064] Therefore, according to the welding apparatus 1 of this embodiment, it is possible to flexibly deal with the occurrence of overshoot and undershoot.

[0065] By flexibly addressing overshoot, it becomes possible to stabilize droplet transfer, suppress welding defects such as undercuts, and reduce spatter generation. By flexibly addressing undershoot, it becomes possible to prevent arc interruption.

[0066] [Differentiation] It should be noted that the present invention is not limited to the embodiments described above, and can be implemented in various other forms without departing from the spirit of the invention. For this reason, the above embodiments are merely illustrative in all respects and should not be interpreted restrictively. For example, the above processes can be arbitrarily rearranged or executed in parallel, as long as there is no inconsistency in the processing content.

[0067] Furthermore, in the above-described embodiment, the command waveform is adjusted by comparing the output waveform with the target waveform so that the first difference and the second difference decrease. However, the command waveform adjustment function may be made switchable by selecting ON or OFF for the adjustment function.

[0068] Furthermore, in the embodiments described above, the output waveform is brought closer to the target waveform by comparing the output waveform with the target waveform and adjusting the command waveform, but the invention is not limited to this. For example, the output waveform may be brought closer to the target waveform by adjusting the current values ​​in the rising and falling portions, and the peak time and base time. [Explanation of symbols]

[0069] 1...Welding equipment, 2...Robot control device, 3...Manipulator, 11...Control unit, 12...Storage unit, 13...Communication unit, 100...Robot system, 111...Command output unit, 112...Current output unit, 113...Difference calculation unit

Claims

1. A command output unit that outputs a current command based on the target waveform of the welding current output as a pulse signal, A current output unit outputs the welding current based on the current command output by the command output unit, The system includes a difference calculation unit that compares the output waveform of the welding current output by the current output unit with the target waveform and calculates a first difference between the output waveform and the target waveform in the rising portion of the output waveform, and a second difference between the output waveform and the target waveform in the falling portion of the output waveform. The command output unit adjusts the command waveform of the previous current command based on the target waveform, the first difference, and the second difference, so that the first difference and the second difference decrease, and outputs the current command with the adjusted command waveform as the next current command. Welding equipment.

2. The command output unit adjusts the previous command waveform by subtracting a current equal to a predetermined percentage of the absolute value of the difference between the peak current of the welding current output by the current output unit and the current that overshot in the rising portion of the previous output waveform from the current in the rising portion of the previous command waveform. The welding apparatus according to claim 1.

3. The command output unit adjusts the previous command waveform so that the time it takes for the ripple generated in the rising edge of the previous output waveform to converge to the peak current of the welding current is shortened. The welding apparatus according to claim 1.

4. The command output unit adjusts the previous command waveform by adding a current equal to a predetermined percentage of the absolute value of the difference between the base current of the welding current output by the current output unit and the current that undershot during the falling edge of the previous output waveform, to the current during the falling edge of the previous current command. The welding apparatus according to claim 1.

5. The command output unit adjusts the previous command waveform so that the time it takes for the ripple generated in the falling edge of the previous output waveform to converge to the base current of the welding current is shortened. The welding apparatus according to claim 1.

6. The difference calculation unit calculates the first difference and the second difference using a predetermined number of output waveforms. The welding apparatus according to claim 1.

7. The command output unit stores the adjusted command waveform in the storage unit, and when performing other welding with the same or similar welding conditions, outputs the current command based on the adjusted command waveform stored in the storage unit. The welding apparatus according to claim 1.

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