JP5428136B2 - Robot system - Google Patents

Description

  The present invention relates to a robot system that performs a welding operation, and in particular, detects the position of a welding line of a workpiece, corrects the position of a welding torch so as to follow the welding line, and performs welding conditions according to the gap length of the workpiece welding line. The present invention relates to a robot system that performs welding work while changing the temperature.

In the welding work by the robot, the control for performing the welding work by correcting the position of the welding torch attached to the robot to follow the welding line while detecting the position of the welding line of the workpiece using a sensor is as tracking control. Widely known. In tracking control, there is a case where gap control is performed in which welding conditions are changed according to the gap length of the weld line.
FIG. 8 is a schematic diagram showing a configuration of a robot system that performs tracking control. In the figure, reference numeral 801 denotes a robot having a plurality of drive shafts, and a welding torch 802 and a sensor 803 are attached to the tip of the robot.
The welding torch 802 is connected to a welding power source 805, and a welding current is generated by the welding power source 805. A sensor control device 806 is connected to the sensor 803, and the sensor control device 806 performs control of the sensor 803, data processing, and data input / output.
On the other hand, the robot 801 is connected to the robot controller 804, and the robot controller 804 controls the drive axis of the robot 801. The robot controller 804 is further connected to a welding power source 805, transmits a welding command to the welding power source 805, and receives a response from the welding power source 805. A sensor control device 806 is also connected to the robot control device 804, and the robot control device 804 transmits a measurement command to the sensor control device 806 and receives sensor data such as measurement data and status from the sensor control device 806.

When the butt joint of the workpiece 807 shown in FIG. 8 is welded by the welding torch 802, the laser slit light 808 emitted from the sensor 803 is irradiated to the preceding position of the welding point, and the position of the step portion of the laser slit light 808 is determined. Detect as position. At the same time, the gap length 809 of the butt joint is also detected. The detected data is sent from the sensor control device 806 to the robot control device 804, and the robot control device 804 corrects the position of the robot 801 so that the welding torch 802 passes through the butt joint based on the detection position of the sensor 803. . In addition, the robot control device 804 changes the welding conditions according to the size of the gap length 809.
The sensor 803 is widely known as a tracking sensor and is also commercially available.

As an example of changing the welding conditions according to the gap length 809 using the robot system as described above, there is an example in which weaving welding is performed (for example, Patent Document 1).
FIG. 9 shows a conventional welding condition table. FIG. 9B is a table in which weaving condition numbers are associated with gap lengths, and FIG. 9A is a table in which weaving condition numbers are associated with welding conditions (weaving pattern, frequency, amplitude, etc.). .
By creating such a welding condition table in the robot controller 804, the welding conditions can be changed according to the gap length 809 obtained from the sensor 803.

Japanese Patent Laid-Open No. 10-244367 (page 6-7, FIG. 12)

Here, the change of the welding conditions according to the change of the gap length 809 will be considered.
The table shown in FIG. 5 is used as the welding condition table. In the welding condition table in FIG. 5, the welding condition number is a number that the robot control device 804 outputs to the welding power source 805. The welding power source 805 receives this welding condition number, and generates a welding current according to the corresponding welding condition set in the welding power source 805.
FIG. 6 is a graph showing the relationship between the gap length and the welding condition number in the welding condition table of FIG. The horizontal axis represents the gap length, and the vertical axis represents the welding condition number. The welding condition number changes stepwise according to the gap length.
However, when the gap length 809 detected from the sensor 803 changes at a short cycle (for example, 0.29 [0.2] [for example, near the gap length of 0.30 [mm] in FIG. 6) at the change point of the welding condition number. mm) to 0.31 [mm] when changing in a short cycle), the welding condition number also changes in a short cycle (for example, changing between welding condition numbers 2 and 3 in a short cycle). This causes a problem that stable welding cannot be performed because the welding conditions change in a short cycle.
On the other hand, FIG. 7 is a graph showing the relationship between the gap length and the welding speed in the welding condition table of FIG. The horizontal axis represents the gap length, and the vertical axis represents the welding speed. As in FIG. 6, the welding speed changes stepwise according to the gap length.
Therefore, when the gap length 809 detected from the sensor 803 changes at a short cycle at a welding speed change point (for example, near the gap length of 0.30 [mm] in FIG. 7), the short cycle is the same as the welding condition number. Since the welding speed changes (for example, the welding speed changes between 95 [%] and 90 [%] in a short cycle), there arises a problem that stable welding cannot be performed.
The gap length detected by the sensor 803 is equal to the gap length specified in the welding condition table because (1) the gap length 809 of the workpiece 807 is actually the distance or (2) the sensor There are cases such as when a detection error or a sensor is erroneously detected, which is normally possible.

As described above, in the conventional robot system, when the detected gap length changes in a short cycle in the vicinity of the gap length set in the welding condition table, the welding quality is deteriorated because the welding condition changes in a short cycle. There was a problem.
The present invention has been made in view of such problems, and provides a robot system capable of performing stable welding even when the detected gap length changes in a short period near the gap length set in the welding condition table. The purpose is to do.

In order to solve the above problem, the present invention is configured as follows.
The invention according to claim 1 includes a robot having a plurality of drive shafts and mounting a welding torch at a tip thereof, a welding power source connected to the welding torch and outputting a welding current to the welding torch, and the vicinity of the welding torch A sensor that detects the position of the weld line of the workpiece and the gap length of the weld line that precedes the welding torch, controls the drive shaft of the robot connected to the robot, and the welding power source and the sensor A robot controller connected to the controller for inputting / outputting information, correcting the position of the welding torch based on the position of the welding line detected by the sensor, and changing the welding condition according to the gap length In the robot system that performs the welding operation while the welding operation is performed, the robot control device has the gap length range and the gap length range. Refer to a welding condition table in which the corresponding welding conditions are recorded, an area for storing condition relaxation parameters stored in advance as length information, and a gap length detected by the sensor at this time and the welding condition table normally. The gap length detected this time by the sensor is smaller than the lower limit of the gap length range corresponding to the current welding condition in the welding condition table, and the gap length range is changed. If the lower limit is greater than the value obtained by subtracting a length defined by the restructured parameter Rutotomoni to maintain the current welding condition, detected gap length this time by the sensor, in the welding condition table Larger than the upper limit of the gap length range corresponding to the current welding conditions, and the gap The condition when relaxed is smaller than the value obtained by adding a length defined by the parameter for the upper limit of the range, characterized in that it comprises a condition relaxing calculator Ru to maintain the current welding condition, the.
In the invention according to claim 2, the robot control device includes means for selecting whether or not condition relaxation is performed, and the condition relaxation calculation unit is configured to select the condition relaxation calculation unit when no condition relaxation is selected. Is characterized in that the welding condition is always changed by referring to the gap length detected this time by the sensor and the welding condition table.

The invention according to claim 3, wherein the welding condition is characterized in that it comprises a welding speed.

The invention according to claim 4, wherein the welding condition is characterized in that it comprises a weaving frequency.

The invention of claim 5, wherein the welding condition is characterized in that it comprises a weaving amplitude.

The invention according to claim 6 is characterized in that the gap length is a size of a deviation generated in a parallel direction or a vertical direction with respect to the workpiece surface.

According to the first aspect of the present invention, the condition relaxation calculation unit uses the condition relaxation parameter to delay the change of the welding condition corresponding to the change in the gap length of the weld line. Even when the gap length changes in the vicinity of the gap length set in (1), the welding condition does not change in a short cycle, and there is an effect that stable welding can be performed.
The amount corresponding to condition relaxation parameter to the gap of the weld line, or can be the ratio of the gap length of the welding line, can select those who easily set depending on the situation, that usability is improved effective.
Further, according to the invention of claim 2 Symbol placement, during the reduction of the gap length to slow changes in the welding conditions can be selected whether to perform in either case increase, there is an effect that usability is improved .
In addition, according to the inventions of claims 3 to 5 , the invention of claim 1 can be applied to various welding conditions, and an effect that more stable welding can be performed under various situations. is there.
According to the sixth aspect of the invention, in addition to the case where the gap length of the weld line is a deviation in the workpiece surface direction, it is possible to deal with a case where the welding line is a deviation in the vertical direction with respect to the workpiece surface. There is an effect that can be done.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a robot controller 804 of the robot system according to the first embodiment of the present invention. This block diagram describes only the portion related to the tracking control in the robot controller 804 in the robot system that performs the tracking control of FIG. 7 already described.
In the figure, reference numeral 103 denotes a sensor processing unit which receives sensor data (position, gap length, time stamp, etc.) detected by the sensor 803 as an input and performs filtering of the data or position data detected by the sensor based on the world coordinate system. Perform processing such as converting to. And the data which the adjacent condition relaxation calculating part 101 requires are output. In the case of the present embodiment, the detected gap length is output.

When the gap length is input from the sensor processing unit 103, the condition relaxation calculation unit 101 saves the gap length input from the previous sensor processing unit 103 in a temporary storage area and refers to the welding condition table 104. Then, the welding conditions corresponding to the gap length input this time are extracted. The welding condition table 104 is the same as that in FIG. 5 described above, and is a table that describes the welding conditions corresponding to the gap length of the weld line. Hereinafter, the welding condition number is taken as an example of the welding condition.
The condition relaxation calculation unit 101 compares the previous and current gap lengths to check the increase / decrease in the gap length and refers to the condition relaxation parameter 102. The condition relaxation parameter 102 is set in advance in the robot control device 804 for the purpose of delaying the change of the welding conditions specified in the welding condition table 104. Then, the condition relaxation calculation unit 101 determines whether or not to change the welding condition number by comparing the change in the gap length, the welding conditions acquired from the welding condition table 104, and the condition relaxation parameter 102.
FIG. 2 is a graph showing the relationship between the gap length and the welding condition number when the condition relaxation parameter 102 is applied. Compared to the graph of FIG. 6, it can be seen that a delay characteristic appears in the change of the welding condition number accompanying the decrease in the gap length.

A specific example of a change in welding conditions when the condition relaxation parameter 102 is applied will be shown below. In the graph of FIG. 2, when the gap length input from the sensor processing unit 103 increases from the previous time to 0.29 [mm], the welding condition number is “2”. When the gap length further increases to 0.30 [mm], the welding condition number changes to “3”.
Conversely, when the gap length decreases from 0.31 [mm] (the welding condition number at this time is “3”) to 0.30 [mm], the welding condition number remains “3”. Even if the gap length continues to decrease to 0.29 [mm] and 0.28 [mm], the welding condition number remains “3”.
When the gap length decreases by the width set by the condition relaxation parameter 102 (in this case, the gap length becomes 0.25 [mm]), the welding condition number changes to “2” and the welding power source 805 is sent. Is output.
The condition relaxation parameter 102 may be specified by an absolute amount of gap length change (in this case, 0.05 [mm]) or may be specified by a ratio as shown in FIG.
When the ratio is specified by the ratio, the gap length interval set in the welding condition table is 0.10 [mm], whereas the setting value of the condition relaxation parameter is 0.05 [mm]. %].

In addition, the control for delaying the change of the welding condition number by the condition relaxation parameter is not always performed, and it can be used together with the control for changing the welding condition immediately according to the change of the gap length as in the prior art. Good.
Specifically, as shown in the welding condition table of FIG. 5, in the “processing method” item regarding “welding condition number”, “with / without condition relaxation” can be selected. May apply a condition relaxation parameter to change the welding conditions as shown in FIG. 2, and in the case of “None”, the welding conditions may be changed as shown in FIG.
In addition to the welding condition number, it is needless to say that the same applies to the weaving frequency set in the welding condition table of FIG.
As described above, since the condition relaxation calculation unit 101 can delay the change of the welding condition accompanying the change of the gap length of the weld line according to the condition relaxation parameter 102, the detected value of the gap length is set in the welding condition table 104. Even when the gap length changes near the gap length, the welding condition does not change at a short cycle. Therefore, stable welding can be performed. This is particularly effective for welding conditions such as welding condition numbers that can only be discretely changed with respect to the gap length.
In the present embodiment, the condition relaxation parameter 102 is applied when the gap length decreases. However, the present invention is not limited to this, and the same effect can be obtained even when the gap length increases. Is clear.

FIG. 3 is a block diagram of the robot controller 804 according to the second embodiment of the present invention. This block diagram describes only the portion related to the tracking control in the robot controller 804 in the robot system that performs the tracking control of FIG. 7 already described. In addition, about the component already demonstrated, the same code | symbol is attached | subjected and description is omitted.
In the figure, 301 is a condition interpolation calculation unit, which interpolates changes in welding conditions corresponding to the gap length of the weld line. Details of the conditional interpolation calculation unit 301 will be described with reference to FIG. In the following, the welding speed is taken as an example as a welding condition.
FIG. 4 is a graph showing the relationship between the gap length interpolated by the condition interpolation calculation unit 301 and the welding speed based on the welding condition table of FIG. Compared with the graph of FIG. 7, it can be seen that the change in the welding speed accompanying the decrease in the gap length is from a stepped shape to a linear shape.
When the gap length is input from the sensor processing unit 103, the condition interpolation calculation unit 301 refers to the “welding speed” column of the welding condition table 104, and is interpolated according to the gap length as shown in the graph of FIG. Output welding speed.

A specific example of processing in the conditional interpolation calculation unit 301 is shown below. When the gap length input from the sensor processing unit 103 is 0.28 [mm], the condition interpolation calculation unit 301 refers to the “gap length” column of the welding condition table 104 and sandwiches 0.28 [mm]. Two gap lengths (0.30 [mm] and 0.20 [mm]) are obtained. Then, the welding speeds corresponding to the two gap lengths, that is, the welding speeds 90 [%] and 95 [%] are read.
Then, using the ratio of the difference between the actual gap length and the two gap lengths (0.30 [mm] and 0.20 [mm]) set in advance in the welding condition table 104 with the value interposed therebetween, 2 is used. An operation for interpolating two welding speeds (90 [%] and 95 [%]) is performed to obtain a welding speed corresponding to the actual gap length. As a result, when the gap length is 0.28 [mm], the welding speed is 91 [%].

As shown in the welding condition table in FIG. 5, in the processing method item relating to “welding speed”, “with / without interpolation” can be selected. 4 may be changed, and in the case of “None”, it may be changed stepwise as shown in FIG.
In the above description, the interpolation of the welding speed is taken as an example, but it goes without saying that the interpolation can be similarly performed for the weaving amplitude set in the welding condition table of FIG. The same can be set for the presence / absence of interpolation.
Thus, since the condition interpolation calculation unit 301 can interpolate the change of the welding condition corresponding to the gap length of the weld line, the detected value of the gap length is near the gap length set in the welding condition table 104. Even in the case where the welding conditions change in a short cycle, the welding conditions change slowly without changing in a short cycle, so that stable welding can be performed. This is particularly effective for welding conditions such as the welding speed that continuously change with respect to the gap length.
The interpolation calculated by the conditional interpolation calculation unit 301 is not limited to a straight line, and curve interpolation may be used.

  Further, in Example 1 or Example 2, the gap length of the weld line has been described as a lateral displacement of the workpiece surface, but also when this is a vertical displacement with respect to the workpiece surface (generally referred to as a mismatch), By applying the present invention, the same effects as those of the first or second embodiment can be obtained.

The block diagram of the robot control apparatus of the robot system of 1st Example of this invention. The figure which graphed the relationship between the gap length and welding condition number of 1st Example of this invention. The block diagram of the robot control apparatus of the robot system of 2nd Example of this invention. The figure which graphed the relationship between the gap length and welding speed of 2nd Example of this invention. Welding condition table screen. The figure which graphed the change of the welding condition number of the welding condition table. The figure which graphed the change of the welding speed of the welding condition table. The block diagram of the robot system which performs tracking control. Conventional welding condition table screen.

Explanation of symbols

101 Condition Relaxation Operation Unit 102 Condition Relaxation Parameter 103 Sensor Processing Unit 104 Welding Condition Table 301 Condition Interpolation Operation Unit 801 Robot 802 Welding Torch 803 Sensor 804 Robot Controller 805 Welding Power Supply 806 Sensor Controller 807 Work 808 Laser Slit Light 809 Gap Length

Claims (6)

A robot having a plurality of drive shafts and mounting a welding torch at the tip;
A welding power source connected to the welding torch and outputting a welding current to the welding torch;
A sensor that is mounted in the vicinity of the welding torch and detects a position of a welding line of a workpiece and a gap length of the welding line in advance of the welding torch;
A robot controller connected to the robot to control the drive axis of the robot and connected to the welding power source and the sensor controller to input / output information;
In the robot system that corrects the position of the welding torch based on the position of the welding line detected by the sensor and performs the welding operation while changing the welding conditions according to the gap length,
The robot controller is
A welding condition table recording the gap length range and the welding conditions corresponding to the gap length range;
An area for storing condition relaxation parameters stored in advance as length information;
Normally, the welding condition is changed with reference to the gap length detected by the sensor and the welding condition table, and the gap length detected by the sensor corresponds to the current welding condition in the welding condition table. If the gap length is smaller than the lower limit of the gap length range and larger than the value defined by subtracting the length defined by the condition relaxation parameter from the lower limit of the gap length range, the current welding conditions are maintained. In addition, the gap length detected this time by the sensor is larger than the upper limit of the gap length range corresponding to the current welding condition in the welding condition table, and the condition is relaxed to the upper limit of the gap length range. It is smaller than a value obtained by adding a length defined by the parameter, to maintain the current welding conditions Robot system comprising: the matter relaxation calculating unit. The robot controller is
Has a means to select the presence or absence of condition relaxation,
The condition relaxation calculation unit, when no condition relaxation is selected, the condition relaxation calculation unit always changes the welding condition with reference to the gap length detected this time by the sensor and the welding condition table. The robot system according to claim 1.   The robot system according to claim 1, wherein the welding condition includes a welding speed.   The robot system according to claim 1, wherein the welding condition includes a weaving frequency.   The robot system according to claim 1, wherein the welding condition includes a weaving amplitude.   The robot system according to any one of claims 1 to 5, wherein the gap length is a size of a deviation generated in a parallel direction or a vertical direction with respect to the workpiece surface.

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