JP5154381B2 - Control method for pulse TIG welding robot and control system for pulse TIG welding robot - Google Patents

Description

  The present invention relates to a control method for a pulse TIG welding robot and a control system for a pulse TIG welding robot.

  Conventionally, when pulse TIG welding is automated, the base material is distorted by welding heat generated in the welding process, and the distance between the welding torch and the workpiece may change, and stable welding may not be possible. As a countermeasure, a reference value of arc voltage is set in advance, and the distance between the welding torch and the workpiece is controlled so that the actual arc voltage becomes equal to the reference value.

  However, if the reference value setting input is incorrect, not only stable welding is possible, but also the welding torch and the workpiece may interfere with each other. Therefore, as a countermeasure, a device that automatically sets a reference value of the arc voltage immediately after the start of welding (Patent Document 1) and a device that uses the arc voltage value after a certain time from the rising edge of the arc voltage as a reference value are proposed. (Patent Document 2).

By the way, even if the reference value is set, if the actual arc voltage (including the peak region and the base region) is monitored, the welding torch vibrates (vertical movement). For this reason, the peak area and the base area of the actual arc voltage are determined, one of the areas is selected according to the time ratio of the pulse base area for a certain period, and the difference between the actual arc voltage and the reference value in that area is obtained. And a control method for correcting the distance between the workpieces has been proposed (Patent Document 3).
JP-A-3-23067 Japanese Patent Application Laid-Open No. 61-78570 JP-A-9-76069

  However, in Patent Document 3, since the actual arc voltage in the base region is smaller than the measurement range of the voltage converter, the variation in measured values is large. In order to solve this problem, a high-performance AD converter is required to perform accurate measurement. In addition, it is necessary to collect in advance highly reliable information on which area to adopt depending on the pulse-based time ratio for each workpiece and welding condition.

  The object of the present invention is to use only the peak area of the actual arc voltage during pulse TIG welding, perform PI control in the peak area, and perform I control in the non-peak area, that is, the base area. An object of the present invention is to provide a control method for a pulse TIG welding robot and a control system for a pulse TIG welding robot that can keep a constant distance between a torch and a workpiece (base material).

  In order to solve the above problems, the invention according to claim 1 is a control method of a pulse TIG welding robot that performs pulse TIG welding on a base material by a welding torch provided in a welding robot. The actual arc voltage in the peak side voltage region that is equal to or higher than the predetermined peak base determination voltage is extracted from the actual arc voltage applied to the current arc voltage in the peak side voltage region. An average voltage of the peak voltage is calculated, and for each control cycle, a torch operation direction is determined based on a voltage difference between the average voltage and a predetermined arc reference voltage, and the peak voltage is calculated for each control cycle. It is determined whether or not the actual arc voltage in the side voltage region is in the peak region, and when it is determined that the actual arc voltage is in the peak region, the difference voltage and the When the operation amount of the welding torch is calculated by PI control based on the torch operation direction and it is determined that the welding torch is not in the peak region, the operation amount of the welding torch is calculated by I control based on the differential voltage and the torch operation direction. A control method for a pulse TIG welding robot, characterized in that the distance between the welding torch and the base material is controlled by calculating and controlling the welding robot based on the operation amount and the torch operation direction of the welding torch. It is a summary.

  According to a second aspect of the present invention, in a control system for a pulse TIG welding robot that performs pulse TIG welding on a base material by a welding torch provided in the welding robot, a predetermined arc voltage is applied in advance to the welding torch. An average voltage calculation that extracts the actual arc voltage in the peak side voltage region that is equal to or higher than the determined peak base determination voltage for each control period and calculates the average voltage of the peak voltage in the actual arc voltage in the peak side voltage region. Means for determining a torch operation direction based on a difference voltage between the average voltage and a predetermined arc reference voltage for each control cycle, and the peak-side voltage region for each control cycle. Determining means for determining whether or not the actual arc voltage is in the peak region, and when determining that the actual arc voltage is in the peak region, When the operation amount of the welding torch is calculated by PI control based on the voltage and the torch operation direction and it is determined that the welding torch is not in the peak region, the operation of the welding torch is performed by I control based on the difference voltage and the torch operation direction. A torch operation amount calculating means for calculating the amount, and a robot control means for controlling the distance between the welding torch and the base material by controlling the welding robot based on the operation amount and the torch operation direction of the welding torch. The gist of the control system of the pulse TIG welding robot is characterized in that it is included.

  According to the first aspect of the present invention, only the peak area of the actual arc voltage is used during pulse TIG welding, PI control is performed in the peak area, and I control is performed in the non-peak area, that is, the base area. In addition, it is possible to provide a control method for a pulse TIG welding robot that can keep a constant distance between a welding torch and a workpiece (base material). Also, according to the control method of the present invention, unlike the conventional case, there is no need to use the actual arc voltage in the base region where the variation in measured values is large, and the measured value of the actual arc voltage in the base region is converted with high accuracy. This eliminates the need for a high-performance AD converter.

  According to the invention of claim 2, during pulse TIG welding, only the peak area of the actual arc voltage is used, PI control is performed in the peak area, and I control is performed in the non-peak area, that is, the base area. Thus, it is possible to provide a control system for a pulse TIG welding robot that can keep a constant distance between the welding torch and the workpiece (base material). According to the system of the present invention, unlike the conventional case, there is no need to use the actual arc voltage in the base region where the variation in measured values is large, and the measured value of the actual arc voltage in the base region can be converted with high accuracy. A high-performance AD converter is not necessary.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a specific embodiment of a control method for a pulse TIG welding robot and a control system for a pulse TIG welding robot according to the present invention will be described with reference to FIGS. FIG. 1 shows an outline of a control system (hereinafter simply referred to as a system) of a pulse TIG welding robot.

  The system includes a welding robot manipulator (hereinafter simply referred to as a welding robot) 10 having a 6-axis joint provided with a welding torch 11, a robot controller 20 for controlling the welding robot 10, a TIG welding power source 30 for supplying power to the welding torch 11, A TIG arc sensor 50 and the like are provided. The TIG welding power source 30 supplies power to the welding torch 11 attached to the tip of the welding robot 10. The workpiece W as a base material is electrically connected via a TIG welding power source 30.

  The robot control device 20 is connected to the TIG arc sensor 50 and can communicate various control information. The robot controller 20 can communicate various control information with the welding robot 10, performs pulse TIG welding according to the teaching program stored in the robot controller 20, and controls signals from the TIG arc sensor 50. Thus, the welding line copying is performed while correcting the position of the welding torch 11, that is, the distance to the workpiece W.

  As shown in FIG. 1, the TIG arc sensor 50 includes a voltage measuring device 51, a peak voltage region determination setting device 52, a peak voltage region extracting device 53, a peak voltage average processing device 54, an arc reference voltage setting device 55, and a differential voltage calculator. 56, a torch operation direction determination unit 57, a peak base voltage determination unit 58, a control method switching unit 59, and a torch operation amount calculation unit 60. In the configuration of the TIG arc sensor 50, the peak voltage region determination setter 52, the peak voltage region extractor 53, the peak voltage average processor 54, the arc reference voltage setter 55, and the differential voltage calculator 56 excluding the voltage measuring device 51. The torch operation direction determination unit 57, the peak base voltage determination unit 58, the control method switching unit 59, and the torch operation amount calculation unit 60 may be configured by a computer or may be configured as individual devices.

  The peak voltage region extractor 53 and the peak voltage average processor 54 correspond to average voltage calculation means. The difference voltage calculator 56 corresponds to a difference voltage acquisition unit. The torch operation direction determiner 57 corresponds to a torch operation direction determination unit. The peak base voltage determination unit 58 corresponds to a determination unit for determining whether or not the actual arc voltage is in the peak region. The operation amount calculator 60 corresponds to torch operation amount calculation means. The robot control device 20 corresponds to robot control means.

(Operation of the embodiment)
The operation of the system configured as described above will be described.
When the welding torch 11 is performing pulse TIG welding on the workpiece W by copying the welding line, the voltage measuring device 51 of the TIG arc sensor 50 is the actual arc voltage A applied to the welding torch 11 from the TIG welding power source 30. Measure. This measurement cycle is a cycle much shorter than the pulse cycle of the power applied by the TIG welding power source 30 to the welding torch 11 and a control cycle described later (see FIG. 6). The voltage measuring device 51 corresponds to voltage measuring means.

  The peak voltage region extractor 53 includes a peak side voltage region R that is equal to or higher than the peak base determination voltage H set in advance by the peak voltage region determination setter 52 for each control cycle in the measured actual arc voltage A (see FIG. 3), the actual arc voltage A is extracted. That is, the actual arc voltage A in the peak side voltage region R (see FIG. 3) equal to or higher than the peak base determination voltage H within the control cycle is extracted. The peak base determination voltage H is set to a value that is higher than the base voltage of the arc voltage of the power supplied by the TIG welding power source 30 and lower than the arc reference voltage K.

  The peak voltage average processor 54 is a peak voltage (that is, extracted during the period of the control cycle) in the actual arc voltage A measured and detected in the control cycle in the peak side voltage region R by the peak voltage region extractor 53. ) To obtain an average voltage M. Although this averaging process can mention a moving average, for example, it is not limited to a moving average, The other well-known average process may be sufficient.

  The difference voltage calculator 56 calculates the difference voltage based on the arc reference voltage K preset by the arc reference voltage setter 55 and the average voltage M obtained by the peak voltage average processor 54. Here, if the average voltage M> the arc reference voltage K, the difference voltage is a positive value, and if the average voltage M <the arc reference voltage K, the difference voltage is −. Further, when the average voltage M = the arc reference voltage K, the differential voltage is zero. Based on the +,-, and 0, the torch operation direction determination unit 57 determines the operation direction of the welding torch 11 for each control cycle.

  That is, in the case of +, since the average voltage M is higher than the arc reference voltage K, the direction approaching the workpiece W is the operation direction, and in the case of-, the average voltage M is lower than the arc reference voltage K. The direction approaching W is the operation direction. In the case of 0, the torch operation direction is not changed.

  The peak base voltage determiner 58 determines whether or not the actual arc voltage A in the peak voltage side region is in the peak region P for each control cycle. The control cycle is shorter than the pulse cycle. FIG. 4 shows an example in order to show the magnitude relationship between the control period and the pulse period. Specifically, in this determination, it is determined that the period during which the peak voltage higher than the peak base determination voltage is measured and detected in the actual arc voltage A is the peak region P (that is, the peak voltage region), and the peak A period in which no peak voltage higher than the base determination voltage is measured and detected is determined as the base region B (that is, the base voltage region) (see FIG. 3).

  When the determination result of the peak base voltage determiner 58 indicates that the actual arc voltage A is in the peak region P, and the actual arc voltage A is not in the peak region P (ie, the actual arc voltage A) In the case of determination that the voltage A is in the base region B), the control method is switched to the PI control and the I control, respectively.

  The operation amount calculator 60 calculates a torch operation amount as a position correction amount of the welding torch 11 by the switched control method. FIG. 2 is a conceptual diagram of the motion amount calculator 60. As shown in the figure, the operation amount calculator 60 includes a proportional control unit 61 (that is, a P control unit) that proportionally controls the differential voltage, and an integration control unit 62 (that is, an I control unit) that performs integral control of the differential voltage. And an adder 63 that adds the outputs of the proportional control unit 61 and the integral control unit 62.

  Then, the adder 63 switches the control method switch 59 to change only the output of the integral control unit 62 as the torch operation amount or the result of adding the output of the proportional control unit 61 and the output of the integral control unit 62. The torch movement amount is output to the robot controller 20. By outputting the torch motion amount and the torch motion direction by the adder 63 to the robot control device 20, the robot control device 20 controls driving of the welding robot 10 based on the torch motion amount and the torch motion direction. Then, the welding torch 11 is moved to control the distance between the welding torch 11 and the workpiece W (base material).

  Here, FIG. 5 shows a case where PI control is performed in the peak region P and I control is not performed in the base region B. In FIG. 5A, the vertical axis represents the actual arc voltage A and the horizontal axis represents the time, and the pulse shape of the actual arc voltage A is shown. In FIG. 5B, the vertical axis represents the scanning height (the distance between the welding torch 11 and the workpiece) of the scanning straight line (that is, the welding line is a straight line), and the horizontal axis represents time. As shown in FIG. 5B, when there is no control in the base region B, the scanning trajectory of the welding torch 11 deviates from the scanning straight line (that is, the scanning position) because I control is not performed in the base region B.

  On the other hand, in this embodiment, when PI control is performed in the peak region P and I control is performed in the base region B, the result is as shown in FIG. In FIG. 4A, the vertical axis represents the actual arc voltage A and the horizontal axis represents the time, and the pulse shape of the actual arc voltage A is shown. In FIG. 4B, the vertical axis represents the scanning height (the distance between the welding torch 11 and the workpiece) of the scanning straight line (that is, the welding line is a straight line), and the horizontal axis represents time. As shown in FIG. 4B, in this embodiment, since I control is performed in the base region B, stable copying can be realized regardless of the peak region P and the base region B. As described above, in this embodiment, since PI control is performed in the peak region P, accurate copying can be performed. In the base region B, switching from PI control to I control is performed, and a past moving average is used. By the control, stable copying can be realized regardless of the current voltage value.

Moreover, the approach and separation movement of the welding torch 11 with respect to the workpiece is reduced by the method as described above, so that copying can be stabilized and stable welding can be performed.
The method and system configured as described above have the following characteristics.

  (1) The control method of the pulse TIG welding robot of the present embodiment is such that the actual arc in the peak side voltage region R equal to or higher than the predetermined peak base determination voltage H from the actual arc voltage A applied to the welding torch 11. The voltage A is extracted for each control period, and the average voltage M of the peak voltage in the actual arc voltage A in the peak side voltage region R is calculated. Then, the torch operation direction is determined on the basis of the difference voltage between the average voltage M and a predetermined arc reference voltage K for each control cycle. Further, in the present embodiment, it is determined whether or not the actual arc voltage A in the peak side voltage region R is in the peak region P for each control period. When it is determined that the actual arc voltage A is in the peak region P and when it is determined that the actual arc voltage A is not in the peak region P, PI control is performed based on the difference voltage and the torch operation direction, respectively. And the operation amount of the welding torch 11 is calculated by I control. Then, the distance between the welding torch 11 and the workpiece W is controlled by controlling the welding robot 10 based on the operation amount of the welding torch 11 and the torch operation direction.

  As a result, according to the control method of the present embodiment, during pulse TIG welding, only the peak area of the actual arc voltage is used, PI control is performed in the peak area, and I control is performed in the non-peak area, that is, the base area. By performing this, it is possible to keep a constant distance between the welding torch and the workpiece (base material). Also, according to the control method of the present invention, unlike the conventional case, there is no need to use the actual arc voltage in the base region where the variation in measured values is large, and the measured value of the actual arc voltage in the base region is converted with high accuracy. This eliminates the need for a high-performance AD converter.

  (2) The system according to the present embodiment uses the actual arc voltage A in the peak side voltage region R equal to or higher than the predetermined peak base determination voltage H from the actual arc voltage A applied to the welding torch 11 as a control cycle. A peak voltage region extractor 53 and a peak voltage average processor 54 (average voltage calculation means) that calculate the average voltage M of the peak voltage in the actual arc voltage A in the peak side voltage region R are extracted.

  The system also includes a torch operation direction determiner 57 (determination unit) that determines a torch operation direction based on a difference voltage between the average voltage M and a predetermined arc reference voltage K for each control period. A peak base voltage determination unit 58 (determination means) is provided for determining whether or not the actual arc voltage A in the peak side voltage region R is in the peak region for each control period.

  The system determines that the actual arc voltage A is in the peak region P and the determination that the actual arc voltage A is not in the peak region P. An operation amount calculator 60 (torch operation amount calculation means) that calculates the operation amount of the welding torch 11 by PI control and I control is provided. The system also includes a robot control device 20 (robot control means) that controls the welding robot 10 to control the distance between the welding torch 11 and the workpiece W based on the operation amount and the torch operation direction of the welding torch 11. .

  As a result, according to the system of the present embodiment, during the pulse TIG welding, only the peak area P of the actual arc voltage is used, and in the peak area P, PI control is performed and the area that is not the peak area P, that is, the base area In B, by performing I control, it is possible to provide a control system for a pulse TIG welding robot that can keep a constant distance between the welding torch 11 and the workpiece (base material). According to the system of the present embodiment, unlike the conventional case, there is no need to use the actual arc voltage in the base region B where the variation in measured values is large, and the measured value of the actual arc voltage in the base region is accurately converted. Therefore, a high-performance AD converter is not necessary.

In addition, you may change embodiment of this invention as follows.
In the above-described embodiment, the welding robot 10 is a welding robot having six axes of joints, but is not limited to six axes. For example, the welding robot may have 5 axes, or 7 axes or more.

  The TIG arc sensor 50 is separate from the robot controller 20, but may be built in the robot controller 20.

The schematic of the control system of a pulse TIG welding robot. The conceptual diagram of the operation amount calculator 60. FIG. Explanatory drawing of the peak side voltage area | region R, the arc reference voltage K, the peak base determination voltage H, the actual arc voltage A, the peak area P, and the base area B. (A) shows the pattern of the actual arc voltage A, (b) is an explanatory view showing the scanning straight line and the scanning locus according to the present embodiment. (A) shows the pattern of the actual arc voltage A, (b) is explanatory drawing which shows the scanning straight line and scanning locus by a comparative example. Explanatory drawing which shows the relationship between a control period and a measurement period.

Explanation of symbols

10 ... welding robot, 11 ... welding torch,
20 ... Robot control device (robot control means),
50 ... TIG arc sensor, 51 ... Voltage measuring instrument,
52 ... Peak voltage region determination setting device,
53. Peak voltage region extractor (peak voltage region extraction means),
54 ... Peak voltage averaging processor (mean voltage calculating means)
56... Difference voltage calculator, 57... Torch operation direction determiner (decision means)
58 ... Peak base voltage determiner (determination means),
60... Operation amount calculator (torch operation amount calculation means).

Claims (2)

In a control method of a pulse TIG welding robot that performs pulse TIG welding on a base material by a welding torch provided in the welding robot,
From the actual arc voltage applied to the welding torch, an actual arc voltage in a peak side voltage region that is equal to or higher than a predetermined peak base determination voltage is extracted for each control period, and the actual arc voltage in the peak side voltage region is extracted. Calculate the average voltage of the peak voltage in the arc voltage,
For each control period, torch operation direction is determined based on the difference voltage between the average voltage and a predetermined arc reference voltage,
For each control cycle, determine whether the actual arc voltage in the peak side voltage region is in the peak region,
When it is determined that the actual arc voltage is in the peak region, the operation amount of the welding torch is calculated by PI control based on the differential voltage and the torch operation direction, and when it is determined that the actual arc voltage is not in the peak region, Calculate the operation amount of the welding torch by I control based on the differential voltage and the torch operation direction,
A control method for a pulse TIG welding robot, wherein the distance between the welding torch and the base material is controlled by controlling the welding robot based on an operation amount of the welding torch and the torch operation direction. In a control system for a pulse TIG welding robot that performs pulse TIG welding on a base material with a welding torch provided in the welding robot,
From the actual arc voltage applied to the welding torch, an actual arc voltage in a peak side voltage region that is equal to or higher than a predetermined peak base determination voltage is extracted for each control period, and the actual arc voltage in the peak side voltage region is extracted. An average voltage calculating means for calculating an average voltage of the peak voltage in the arc voltage;
Determining means for determining a torch operation direction based on a difference voltage between the average voltage and a predetermined arc reference voltage for each control period;
Determining means for determining whether or not the actual arc voltage in the peak side voltage region is in the peak region for each control period;
When it is determined that the actual arc voltage is in the peak region, the operation amount of the welding torch is calculated by PI control based on the differential voltage and the torch operation direction, and when it is determined that the actual arc voltage is not in the peak region, A torch operation amount calculating means for calculating an operation amount of the welding torch by I control based on the differential voltage and the torch operation direction;
A pulse TIG welding robot comprising: robot control means for controlling the distance between the welding torch and the base material by controlling the welding robot based on an operation amount of the welding torch and the torch operation direction. Control system.

Images