JPH0587356B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in a method for controlling welding current and welding voltage in a control device for a welding robot.

(Conventional technology and its problems) When welding workpieces using a welding robot, it is necessary to appropriately select the welding current and welding voltage depending on the type, posture, groove shape, etc. of the workpiece. . For this reason, the welding robot control device is
Usually, it is configured such that these welding currents and welding voltages can be selected.

The general configuration of such a control device is shown in FIG. In the figure, this control device 1 has a microcomputer 3 for controlling a welding machine (welding power supply device) 5 and a servo system (not shown) of a welding robot. This microcomputer 3 outputs a welding voltage command signal S _V and a welding current command signal S _I according to the welding conditions input from the remote control panel 2 in a manner described later.
These are given to the welding machine 5 after being D/A converted by D/A converters 4a and 4b, respectively.

The welding machine 5 is configured to supply electric power to the torch 6 and the workpiece W according to these command values to provide a welding voltage V and a welding current I.

In the configuration shown in FIG. 7, there are two methods for specifying welding current and welding voltage from the keyboard of the remote control panel 2. One method is to prepare in advance several to dozens of appropriate combinations of desired welding current I and welding voltage V, and then set the welding current command value S _I and welding voltage command value according to each.
This method specifies the pair with _SV using a menu number.

When creating this menu, the correspondence between the welding current command value S _I and the welding current I and the welding voltage command value as shown in FIG.
It is necessary to obtain characteristic data (characteristic curves) that express the correspondence between S _V and welding voltage V in advance.

However, in this method, the command values S _I and S _V are selected, so it is not possible to directly specify the actual welding current I and welding voltage V.
In addition to not being able to be used in numerically controlled robots that apply CAM, there is a problem in that it is not always possible to specify the optimal welding conditions because the number of menus is limited.

On the other hand, in the second method, the characteristic data of the second and fourth quadrants of FIG. 8 are stored in the microcomputer 3 of FIG. It is specified directly from the keyboard of operation panel 2. Then, a welding current command value S I and a welding voltage command value S _V corresponding to the designated welding current I and welding voltage _V are determined from the characteristic data in the ROM and output to the welding machine 5.
Therefore, in this case, control is performed by combining the theoretical conversion of "actual value → command value" by the ROM and the conversion of "command value → actual value" in the actual welding machine 5. It turns out.

However, as is well known, the actual welding current I and welding voltage V are not determined solely by the command values from the control device, but are also determined by the characteristics of the welding machine itself, as well as the workpiece and torch during welding. changes depending on the position of the wire, wire extension, and other factors. For this reason, actual welding characteristics will vary depending on the work object and work environment.
In the second method above, each time the characteristics change, the ROM
The problem is that it has to be replaced.

(Objective of the Invention) This invention is intended to overcome the above-mentioned problems, and allows the welding current and welding voltage to be directly specified to improve operational control and to respond accurately and quickly to changes in welding characteristics. It is an object of the present invention to provide a method for controlling welding current and welding voltage in a control device for a welding robot.

(Means for Achieving the Object) In order to achieve the above-mentioned object, a welding current and welding voltage control method in a welding robot control device according to the present invention includes a welding current and a welding voltage;
Pre-created standard characteristic curve data representing the correspondence between the welding current command value and the welding voltage command value given to the welding machine from the control device is stored in the storage device, and welding is performed under conditions corresponding to the welding operation. Characteristic data expressing the correspondence between the welding current command value and welding voltage command value and the actual welding current and welding voltage by causing the welding robot to perform welding while detecting the current and welding voltage. is created by correction based on the stored reference characteristic curve data, and the created characteristic data is stored in a storage device to correspond to the specified welding current and welding voltage when performing welding work. The welding current command value and the welding voltage command value are determined from the stored characteristic data and output to the welding machine.

(Example) Overall configuration of the welding robot according to the example 1st
The figure is a block diagram of a control device for a welding robot according to an embodiment of the present invention. In the figure, this control device 10 includes a microcomputer 11 including a CPU 12 and a memory 13 as a storage device.
The memory 13 includes a RAM 14 that stores characteristic data, which will be described later, in a readable and writable manner.

Further, a remote control panel 15 for input/output is connected to the bus line BL of this microcomputer 11. The remote control panel 15 includes a mode changeover switch SM for switching modes such as manual mode, auto mode, and characteristic data creation mode, and a group of manual operation snap switches for manually moving the torch 6.
In addition to SW, etc., there is a start switch STA for instructing to import data and start operations, and a digital key 1 for inputting various numerical values.
6. It is also equipped with an LED display 17.

Furthermore, a robot servo system 18 including a mechanical power M of the welding robot and an encoder E is connected to the bus line BL, and the microcomputer 11 gives a drive command output S _M to this, and It is designed to take in the encoded signal S _E. Furthermore, this servo system 18
Since the mechanical structure of the welding robot can be the same as that of a conventional welding robot, a detailed explanation will be omitted.

On the other hand, the welding voltage command signal S _V and welding current command signal S _I from the microcomputer 11 are respectively converted into analog signals by D/A converters 4 a and 4 b and then provided to the welding machine 5 .
Welding power PW supplied from the welding machine 5 in response to these input signals is applied to the consumable electrode 20 via the current sensor 19. This consumable electrode 20 is wound around a spool 21, and one end thereof extends to the torch 6, and can be fed out by a feed roller (not shown).

Furthermore, the welding voltage V and welding current I during actual welding are the voltage sensor 22 inserted between the consumable electrode 20 side and the workpiece W side and the current sensor 1
9 and are displayed on the voltmeter 23 and ammeter 24, and A/D converted by the A/D converters 25a and 25b, and then taken into the microcomputer 11. ing.

Operation A of Embodiment Creation and Storage of Characteristic Data Next, among the operations of this control device, creation and storage of characteristic data will be explained with reference to FIG.
This operation is performed at any desired time, for example, before the start of a day's welding work, or whenever the work object or work environment changes.

First, operate the mode changeover switch SM shown in Figure 1 to set the characteristic data creation mode, and then proceed to the step
In S1, one value for each of the welding current I and the welding voltage V is input as a target value from the numeric keypad 16. Criteria for selecting these target values will be described later.

In the next step S2, the CPU 12 searches the reference characteristic curve data stored in advance in the memory 13, and obtains the welding current command value S _I and welding voltage corresponding to the input welding current I and welding voltage V, respectively. Welding is performed by determining command values S _V and outputting them to the welding machine 5. This "standard characteristic curve" data is a welding current I created in advance using a test piece, etc.
and characteristic data expressing the correspondence between welding voltage V, welding current command value S _I and welding voltage command value S _V , an example of which is shown by C _O in FIG.

That is, in step S2 above, when the input welding current value is I _A , the welding current command value S _A is determined based on this standard characteristic curve C _O , and this command value S _A is output to the welding machine 5. That's why. In addition,
This FIG. 3 only shows the welding current I, and does not show the welding voltage V.
The welding voltage V is also treated in the same manner. In addition, although the description below will focus on current, it should be understood that the same process is performed for voltage as well.

In step S3, the CPU 12 takes in the detected values from the current sensor 19 and voltage sensor ₂₂ in FIG _. let

In other words, the reference characteristic curve C _O in Figure 3 is fixed data prepared in advance, and if the welding conditions change, the command values S _I and S _V determined based on this may not be output. , actually the welding current
Since the target value of welding current cannot be obtained as is, the command value is corrected in order to actually obtain the target value. For example, the target value in Figure 3
Command value S _A was output for I _A , but the actual characteristic curve is C ₁ , and when current I _B is detected as welding current I, the command value is corrected from S _A to S _B. By doing so, the target value I _A is achieved.

When the state corresponding to the target value is achieved in this way, in the next step S4, the CPU 12 takes in the command values S _I , S _V, etc. at this time, and the RAM 14
Store it in the corresponding area within. Note that selection of a storage area when obtaining a plurality of types of characteristic data under different conditions will be described later.

In the next step S5, it is determined whether all target values have been input, and if they have not been input, the step
Return to S1 and repeat the same operation. That is,
In order to obtain a characteristic curve, it is necessary to input several sets of target values in sequence and obtain (corrected) command values for them. In this example, the number of sets is 10, and for example, As shown in FIG. 5, which will be explained later, target values I ₁ , I ₂ , . . . , I ₁₀ are input in sequence. Then, the command values S ₁ , S ₂ ,
…, S ₁₀ is found and stored.

There is no particular limitation on how to determine this target value, but as shown in Figure 3 or Figure 8 above, the characteristic curve is almost a straight line at the center and has a large curvature at the ends. Therefore, it is desirable to set them sparsely in the center and densely at the edges.

Returning to FIG. 2, when data acquisition for all target values is completed, the process moves to step S6.
Based on the captured data, new characteristic curve data is created based on the correspondence between welding current I and welding voltage V and their respective correction command values, and is stored in the corresponding area in RAM 14. Then, characteristic data creation and storage processing is completed.

However, when measuring characteristic data, it is not limited to this method; for example, as shown in Figure 4, the command value based on the standard characteristic curve is S _A for the target value I _A , and it is not possible to When this command value S _A is given and I _B is detected as the welding current, I _A is
I _B may be corrected and the value of I _B may be stored as a corrected current value.

B. Interpolation Process By the way, in this example, only 10 sets of values are used as target values, so characteristic data for all welding current values I and welding voltage values V can be directly obtained using only the raw data. isn't it. For example, if welding current value I and welding voltage value V can each be input in 8 bits (=256 levels), data regarding values other than the target values will be required during actual welding work.

Therefore, in this embodiment, by interpolating the data obtained for the target values, it is possible to input all welding currents I and welding voltages V in 8-bit representation. This interpolation may be performed in step S6 in FIG. 2 above, and data including this interpolated value may be stored in the RAM 14. Also, only the 10 sets of measured values may be used as the characteristic data. It is also possible to store the data and perform interpolation calculations based on the data read out from the RAM 14 during actual welding work, but this interpolation method will be explained here.

As shown in Fig. 5, S ₁ , I ₂ , S ₂ , I ₂ ,...,
When 10 sets of data S ₁₀ and I ₁₀ are obtained, in this embodiment, linear interpolation is performed between two adjacent sets of data, and the maximum value S _nax ( ₌
255) and S ₁₀ , and the minimum value S _nio (=
0) and S ₁ , respectively, S ₉ ,
Data is obtained by performing linear extrapolation using the data of S ₁₀ and S ₁ , S ₂ . This is not only because linear interpolation is the simplest and requires less calculation time, but also because most parts of the characteristic curve are originally linear, so linear interpolation provides a more accurate approximation. Based. However, since the curvature may be relatively large near the end of the characteristic curve, it is also effective to employ circular interpolation or the like.

The broken line obtained in this way is shown as a broken line in FIG. 5, and it can be seen that the characteristic curve is reproduced fairly faithfully by this interpolation.

C Operation during welding work Once new characteristic data is obtained as described above,
Actual welding work can be performed. Therefore,
Next, this operation will be explained with reference to FIG.

First, in step S10, the welding current I and welding voltage V in each welding section are stored in the teaching data in the playback method, and in the data prepared in advance in the numerical control method.
Specify the value of , and then set the welding robot to regeneration mode. In the next step S11, CPU1
2 searches the characteristic data in the RAM 14, reads out and sets command values S _I and S _V for the welding current I and welding voltage V in the first welding section.
In addition, when performing the above-mentioned interpolation at the time of reading,
Interpolation processing is performed in this step to obtain the command value.

In the next step S12, these command values S _I , S _V
is output to the welding machine 5 to perform welding in that section. At this time, of course, the servo system 18 is also being controlled. Then, in step S13, it is determined whether or not all sections have been welded, and if welding sections remain, the process returns to step S11 and the same process is repeated.
When all of the welding sections have been welded, the process is completed.

Other Examples By the way, if one welding robot performs welding in a single posture or in a single groove shape, it is sufficient to create only one type of characteristic data. , when conditions such as posture are different for each section, or when different types of workpieces must be welded alternately, it is desirable to use different characteristic curves for each section and type of workpiece. become.

In such a case, create the above-mentioned characteristic data separately for each condition, store the multiple characteristic data in different areas of the RAM 14, and then create the characteristic data for each condition during welding work. Then, the corresponding area can be accessed and the necessary characteristic data can be retrieved.

Therefore, in this case, the conditions are entered as parameters from the numeric keypad 16 when creating the characteristic data, and the storage in steps S4 and S6 in FIG. 2 and the readout in step S11 in FIG. 6 are performed based on each condition. It is configured so that it is carried out in areas prepared for this purpose. By doing so, characteristic data corresponding to each condition can be prepared and used, thereby further utilizing the advantages of the present invention.

Modifications By the way, the present invention is not limited to the above-mentioned embodiment, and for example, the following modifications are also possible.

Setting target values for creating characteristic data does not necessarily have to be done manually; for example, it is also possible to automatically set target values in fixed value increments from a predetermined current/voltage value. It is.

In the above embodiment, interpolation processing is performed to shorten the data acquisition processing time for creating characteristic data, but when particularly high precision is required, all targets depending on the resolution can be It is also possible to take in data on values or command values to further refine the characteristic data.

When creating characteristic data, the standard characteristic curve data prepared in advance is corrected to obtain new characteristic data, but the previously created characteristic data stored in the RAM is used as the standard characteristic curve data. Good too.

If you want to create and save characteristic data for each of a variety of conditions, you can save it not only in the RAM in the microcomputer but also in an external storage device such as a cassette tape or bubble memory. . In particular, as mentioned above, when correcting the previously created characteristic data to obtain new characteristic data, make sure that the characteristic data at that point does not disappear when the power is turned off after completing the work. This modification is effective.

(Effects of the Invention) As explained above, according to the present invention, a correction is made based on pre-created standard characteristic curve data stored in a storage device to create characteristic data. Data creation time can be shortened. Furthermore, based on the created characteristic data, the welding current and welding voltage can be directly specified to improve operability, and since the characteristic data can be rewritten with new ones as necessary, it is possible to avoid changes in welding characteristics. Therefore, it is possible to obtain a method for controlling welding current and welding voltage in a control device for a welding robot, which can respond accurately and quickly to the welding robot.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a control device according to an embodiment of the present invention, FIGS. 2 and 6 are flowcharts showing the operation of the embodiment, and FIGS. 3 and 4 are characteristic data creation principles and their modifications. FIG. 5 is a diagram showing an example of interpolation, FIG. 7 is a block diagram showing the general configuration of a conventional device, and FIG. 8 is a diagram illustrating welding characteristics. 1, 10... Control device, 3, 11... Microcomputer, 2, 15... Remote control panel, 5...
Welding machine, 6...Torch, 13...Memory, 14...
...RAM, W...work.

Claims (1)

[Claims] 1. A method for controlling welding current and welding voltage in a control device of a welding robot during welding work, comprising: welding current and welding voltage, and a welding current command value and welding voltage command given from the control device to the welding machine. Pre-created reference characteristic curve data expressing the correspondence with each value is stored in the storage device, and the welding robot is made to perform welding while detecting the welding current and welding voltage under conditions corresponding to the welding work. Particularly, characteristic data expressing the respective correspondence relationships between the welding current command value and welding voltage command value and the actual welding current and welding voltage are corrected based on the stored reference characteristic curve data. At the same time, the created characteristic data is stored in a storage device, and when performing welding work, the welding current command value and welding voltage command value corresponding to the specified welding current and welding voltage are memorized. A method for controlling welding current and welding voltage in a control device for a welding robot, characterized in that the welding current and welding voltage are determined from the characteristic data and output to the welding machine. 2. The characteristic data consists of the correspondence relationship determined for the specified number of welding current values and welding voltage values, and when performing welding work, the welding current command value and the welding current command value determined by interpolation of the characteristic data are used. A method for controlling welding current and welding voltage in a welding robot control device according to claim 1, characterized in that a welding voltage command value is output to a welding machine.