Robot system

Abstract

This system provides a robotic system that allows for simple and objective verification of welding quality. [Solution] The robot system includes a deviation amount calculation unit 111 that calculates the amount of deviation from the welding position determined for each welding condition based on the detected value of an arc sensor used for tracing the welding line, a correction unit 112 that corrects the movement of the welding torch based on the calculated deviation amount, a standard deviation calculation unit 113 that calculates the standard deviation of the deviation amount, a score calculation unit 114 that calculates an evaluation score related to the quality of the welding based on the difference between the calculated standard deviation and the allowable standard value of the deviation amount, and an output unit 115 that outputs the calculated evaluation score.

Description

Technical Field

[0001] The present invention relates to a robot system.

Background Art

[0002] In Patent Documents 1 and 2 below, an arc sensor is disclosed that performs tracking control of a welding line while correcting the position of a welding torch when a workpiece deviates from a pre-taught welding line by using changes in welding current and voltage due to a weaving operation during welding. The weaving operation is an operation that vibrates left and right with respect to the welding progress direction.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in the tracking control by an arc sensor, due to a plurality of external factors (such as the type of workpiece, the type of groove, the routing of the welding power cable, etc.), the current and voltage during welding may fluctuate unexpectedly. In such a case, it may not be possible to capture the correct welding line, and the operation by the tracking control may become unstable. To appropriately deal with the instability of the operation, skilled welding skills are required. However, in recent years, the number of skilled workers with welding skills has been decreasing. From such a situation, there is a demand for a technology that can simply and objectively confirm the welding quality without requiring welding skills.

[0005] Therefore, an object of the present invention is to provide a robot system that can simply and objectively confirm the quality of welding.

Means for Solving the Problems

[0006] A robot system according to one aspect of the present invention includes: a deviation amount calculation unit that calculates a deviation amount from the welding position determined for each welding condition based on the detected value of an arc sensor used for tracing the welding line; a correction unit that corrects the movement of the welding torch based on the calculated deviation amount; a standard deviation calculation unit that calculates the standard deviation of the deviation amount; a score calculation unit that calculates an evaluation score related to the quality of the welding based on the difference between the calculated standard deviation and the allowable standard value of the deviation amount; and an output unit that outputs the calculated evaluation score.

[0007] According to this embodiment, based on the detected value of the arc sensor used for tracing the weld line, the amount of deviation from the welding position determined for each welding condition is calculated, the movement of the welding torch is corrected based on the calculated amount of deviation, and an evaluation score regarding the welding quality is output, calculated based on the difference between the standard deviation of the amount of deviation and the allowable standard value of the amount of deviation.

[0008] In the above embodiment, the standard deviation calculation unit may calculate the standard deviation based on the amount of deviation for each predetermined number of weaving cycles.

[0009] According to this embodiment, it is possible to output an evaluation score regarding the quality of the weld for each predetermined number of weaving cycles.

[0010] In the above embodiment, the standard deviation calculation unit may calculate the standard deviation based on the amount of deviation over the entire welding section that has been set in advance.

[0011] According to this embodiment, it is possible to output an evaluation score regarding the welding quality of the entire welding section.

[0012] In the above embodiment, the score calculation unit may further calculate an acceptable standard value by weighting each parameter value of the welding conditions.

[0013] According to this aspect, it is possible to output an evaluation score regarding the quality of welding by using an allowable reference value considering the contribution degree of each parameter of the welding conditions.

[0014] In the above aspect, a determination unit that compares the calculated evaluation score with a predetermined threshold value to determine the quality of welding may be further provided.

[0015] According to this aspect, it is possible to determine the quality of welding based on a threshold value determined for judging whether the welding quality is good or bad.

[0016] In the above aspect, a notification unit that notifies that there is an abnormality when the calculated evaluation score is less than or equal to a specified value in each section divided by a predetermined number of weavings may be further provided.

[0017] According to this aspect, an operator can confirm the presence or absence of an abnormality every predetermined number of weavings.

Advantages of the Invention

[0018] According to the present invention, it is possible to provide a robot system capable of simply and objectively confirming the quality of welding.

Brief Description of the Drawings

[0019] [Figure 1] It is a diagram illustrating the configuration of a robot system according to an embodiment. [Figure 2] It is a diagram illustrating a functional configuration of a control unit of a robot control device. [Figure 3] It is an example of a table defining the relationship between the difference between the standard deviation and the allowable reference value and the evaluation score. [Figure 4] It is a flowchart for explaining an example of the operation of a robot system according to an embodiment.

Modes for Carrying Out the Invention

[0020] Referring to the accompanying drawings, preferred embodiments of the present invention will be described. In each figure, those denoted by the same reference numerals have the same or similar configurations. Also, since the drawings are schematic, the dimensions and ratios of each component are different from the actual ones.

[0021] FIG. 1 is a diagram illustrating the configuration of a robot system 100 according to an embodiment. The robot system 100 includes, for example, a robot control device 1, a manipulator 2, a welding power source 3, and a teach pendant 4.

[0022] The robot control device 1, the manipulator 2, the welding power source 3, and the teach pendant 4 are connected to each other via cables or a network. The network may be wired or wireless.

[0023] The manipulator 2 is a welding robot (industrial robot) that performs arc welding on a workpiece (base material) to be welded according to the welding construction conditions set in the robot control device 1. The manipulator 2 includes, for example, an articulated arm provided on a base member fixed to the floor surface of a factory or the like, and a welding torch connected to the tip of the articulated arm as one of the working tools.

[0024] The welding construction conditions include, for example, data items such as welding conditions, welding start position, welding end position, welding distance, position and posture of the welding torch, etc. The welding conditions include data items such as welding current, welding voltage, welding speed, weaving frequency, weaving amplitude, wire feeding speed, material and thickness of the workpiece.

[0025] The welding power source 3 supplies, for example, welding current and welding voltage to the manipulator 2 according to predetermined welding construction conditions in order to generate an arc between the tip of the welding wire and the workpiece.

[0026] The teach pendant 4 is an operation terminal used when an operator teaches the operation of the manipulator 2. The teach pendant 4 may be a tablet-type teach pendant.

[0027] The robot control device 1 is a control unit that controls the operation of the manipulator 2. The robot control device 1 includes, for example, a control unit 11, a memory unit 12, a communication unit 13, and an arc sensor 14. The arc sensor 14 may be provided separately from the robot control device 1.

[0028] The control unit 11 is a processor that controls the robot control device 1, manipulator 2, etc., by executing programs such as work programs stored in the memory unit 12. The various functions of the control unit 11 that are realized by executing programs will be described later.

[0029] The memory unit 12 is a computer-readable recording medium that stores programs for realizing various functions in the robot control device 1, as well as various data used in those programs.

[0030] The communication unit 13 is a communication interface that controls communication with the manipulator 2, welding power supply 3, teach pendant 4, and other components.

[0031] The arc sensor 14 is a sensor used for tracking the weld line and has the function of detecting the welding current and welding voltage during welding. Tracking the weld line is a control method that detects the position of the weld line from fluctuations in the welding current and welding voltage that occur when the welding torch is swung (weaving) from side to side relative to the direction of travel of the joint, and makes the welding torch follow along the weld line.

[0032] Figure 2 illustrates the functional configuration of the control unit 11 of the robot control device 1. The control unit 11 of the robot control device 1 includes, for example, a displacement calculation unit 111, a correction unit 112, a standard deviation calculation unit 113, a score calculation unit 114, an output unit 115, a determination unit 116, and a notification unit 117.

[0033] The displacement calculation unit 111 calculates the displacement from the taught welding position based on the values ​​detected by the arc sensor 14. The values ​​detected by the arc sensor 14 include, for example, the welding current, welding voltage, and weaving position. The welding position is a position on the weld line that is determined for each welding condition, such as the welding current, welding voltage, welding speed, weaving frequency, and weaving amplitude.

[0034] The correction unit 112 corrects the movement of the welding torch based on the displacement amount calculated by the displacement amount calculation unit 111. Specifically, it corrects the position (endpoint) of the maximum amplitude of the weaving, which is calculated based on the detected value, so that it matches the taught position.

[0035] The standard deviation calculation unit 113 calculates the standard deviation of the displacement amount calculated by the displacement amount calculation unit 111. The standard deviation of the displacement amount becomes a judgment value used when determining the degree of wobble of the welding torch.

[0036] Here, the amount of deviation used when calculating the standard deviation may be, for example, the amount of deviation for each predetermined number of weaving cycles, or the amount of deviation over the entire welding section from the taught welding start position to the welding end position. The predetermined number of cycles and the range of the welding section when collecting the deviation amount can be set as appropriate by the operator.

[0037] The score calculation unit 114 calculates an evaluation score for welding quality based on the difference between the standard deviation of the deviation amount calculated by the standard deviation calculation unit 113 and the allowable standard value of the deviation amount. The allowable standard value of the deviation amount may be a predetermined standard value, or it may be calculated for each welding condition. An example of calculation for each welding condition is described below.

[0038] The permissible threshold for the amount of displacement may be calculated, for example, by assigning weights to each parameter value of the welding conditions and adding up the weighted values ​​of each parameter. Preferably, the parameters of the welding conditions are the welding current or welding voltage, welding speed, weaving frequency, and weaving amplitude. In this case, if the weights assigned to each parameter are Wa, Wb, Wc, and Wd, respectively, the permissible threshold for the amount of displacement can be calculated by the following equation (1).

[0039] Allowable deviation value = Welding current or welding voltage × Wa + Welding speed × Wb + Weaving frequency × Wc + Weaving amplitude × Wd … (1)

[0040] The score calculation unit 114 may calculate the evaluation score by referring to a table that defines the relationship between the difference between the standard deviation and the acceptable threshold value and the evaluation score. The table to be referenced is described below.

[0041] Figure 3 shows an example of a table T that defines the relationship between the difference between the standard deviation and the acceptable threshold value, and the evaluation score. In table T of Figure 3, it is defined that if the difference between the standard deviation and the acceptable threshold value exceeds 3.5 [mm], the evaluation score is 0; if the difference is greater than 3.0 [mm] but 3.5 [mm] or less, the evaluation score is 1; if the difference is greater than 2.5 [mm] but 3.0 [mm] or less, the evaluation score is 2; ... (omitted) ..., if the difference is greater than 0.5 [mm] but 0.7 [mm] or less, the evaluation score is 9; and if the difference is 0.5 [mm] or less, the evaluation score is 10. It is preferable to store this table T in the memory unit 12 of the robot control device 1.

[0042] Returning to the explanation of Figure 2, the output unit 115 outputs the evaluation score calculated by the score calculation unit 114. The evaluation score may be displayed on a display, output externally as data, or output as sound from a speaker. In this embodiment, the arc monitor function of the teach pendant 4 is used to display the evaluation score on the display of the teach pendant 4.

[0043] The determination unit 116 determines the quality of the weld by comparing the evaluation score calculated by the score calculation unit 114 with a predetermined threshold. The predetermined threshold can be set by the operator as an appropriate value for determining whether the weld quality is good or bad.

[0044] For example, if a predetermined threshold is set to 7, the welding quality is determined to be good when the evaluation score is 7 or higher, and poor when the evaluation score is less than 7. Preferably, the determined welding quality is displayed on the display of the teach pendant 4 using the arc monitor function of the teach pendant 4.

[0045] The notification unit 117 notifies that there is an abnormality if the evaluation score calculated by the score calculation unit 114 is below a specified value in each of the predetermined sections of the weaving process. The specified value can be set by the operator as an appropriate value for judging the quality of the weld.

[0046] Notification may be provided by displaying an abnormal message on the display, outputting an alarm sound from the speaker, or illuminating an alarm lamp. In this embodiment, the arc monitor function of the teach pendant 4 is used to display the abnormal message on the display of the teach pendant 4.

[0047] Referring to Figure 4, an example of the operation of the robot system 100 according to this embodiment will be described.

[0048] First, the displacement calculation unit 111 calculates the displacement from the taught welding position based on the value detected by the arc sensor 14 (step S101).

[0049] Next, the correction unit 112 corrects the movement of the welding torch based on the amount of deviation calculated in step S101 (step S102).

[0050] Next, the standard deviation calculation unit 113 calculates the standard deviation of the amount of deviation calculated in step S101 (step S103).

[0051] Next, the score calculation unit 114 calculates an evaluation score for welding quality based on the difference between the standard deviation of the deviation amount calculated in step S103 and the allowable standard value of the deviation amount (step S104).

[0052] Next, the output unit 115 outputs the evaluation score calculated in step S104 (step S105). Then, this operation ends.

[0053] As described above, according to the robot system 100 of the embodiment, based on the detected value of the arc sensor 14 used for tracing the weld line, it is possible to calculate the amount of deviation from the welding position determined for each welding condition, correct the movement of the welding torch based on the calculated amount of deviation, and output an evaluation score regarding the quality of the welding calculated based on the difference between the standard deviation of the amount of deviation and the allowable standard value of the amount of deviation.

[0054] Therefore, according to the robot system 100 of this embodiment, it is possible to easily and objectively check the quality of welding without requiring welding skills.

[0055] 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 order of each processing step described above can be arbitrarily changed or executed in parallel, as long as there is no inconsistency in the processing content. [Explanation of symbols]

[0056] 1...Robot control device, 2...Manipulator, 3...Welding power supply, 4...Teach pendant, 11...Control unit, 12...Storage unit, 13...Communication unit, 14...Arc sensor, 100...Robot system, 111...Slip amount calculation unit, 112...Correction unit, 113...Standard deviation calculation unit, 114...Score calculation unit, 115...Output unit, 116...Determination unit, 117...Notification unit

Claims

1. A deviation amount calculation unit calculates the amount of deviation from the welding position determined for each welding condition based on the detected value of the arc sensor used for controlling the tracing of the welding line, A correction unit that corrects the movement of the welding torch based on the calculated displacement amount, A standard deviation calculation unit that calculates the standard deviation of the aforementioned deviation amount, A score calculation unit calculates an evaluation score for welding quality based on the difference between the calculated standard deviation and the allowable standard value for the amount of deviation. An output unit that outputs the calculated evaluation score, A robotic system equipped with the following features.

2. The standard deviation calculation unit calculates the standard deviation based on the amount of deviation for each predetermined number of weaving cycles. The robot system according to claim 1.

3. The standard deviation calculation unit calculates the standard deviation based on the amount of deviation over the entire pre-set welding section. The robot system according to claim 1.

4. The score calculation unit further calculates the allowable standard value by weighting each parameter value of the welding conditions. The robot system according to claim 1.

5. The system further includes a determination unit that compares the calculated evaluation score with a predetermined threshold to determine the quality of the welding, The robot system according to claim 1.

6. The system further includes a notification unit that notifies of an abnormality if the calculated evaluation score in each section, which is divided into a predetermined number of weaving steps, is below a specified value. The robot system according to claim 1.

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