JPH091337A - Method for controlling weld seam copying in arc of automatic pipe circumference welding equipment - Google Patents

Abstract

PURPOSE: To provide a method for controlling the weld seam copying in the arc to control the welding current/voltage, prevention of the pulse irregularity, and the arc voltage output suitable for the position of a welding torch in the high speed weaving control of an automatic pipe circumference welding equipment by the high frequency pulse AMG welding method. CONSTITUTION: A latch register 1 (22) of the current/voltage to convert the feedback signal by an A/D converter 20 and to latch the data is provided on a welding arc current/arc voltage control circuit, a position data latch register 2 (23) to latch the position counter value of the position feedback pulse signal of a servo circuit is provided to control the torch position, and a circuit is provided to latch the data at the same timing to the respective registers with the sampling clock as a trigger. The weld seam copying control in the arc, the pulse irregularity prevention control, and the arc voltage output control are realized by using the measured values obtained by the respective registers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to welding line tracing control in an arc, and more particularly to automatic arc welding for controlling high speed weaving circumferential welding in real time.

[0002]

2. Description of the Related Art Conventional weaving for arc welding of the circumference of a pipe is generally performed by a pulse motor for relatively low speed and by a servo motor for high speed. The arc welding line tracing is a method of positionally tracing a torch with respect to a work by monitoring current and voltage during welding. About this, as shown in Fig. 10, the current and voltage are measured by an A / D converter (hereinafter A / D),
It is generally performed by software processing.

Japanese Patent Application Laid-Open No. 63-183 discloses a method for performing circumferential welding.
776, Japanese Examined Patent Publication No. 7-12542, there is an all-position welding device made by Nippon Kokan.This is to perform high-speed rotation of the torch to follow the welding line in the arc, and the groove shape is a narrow groove. High precision machining is required and it is difficult to apply it to a work with wide groove width. As an automatic arc welding method by real-time control of the welding of the groove, there is JP-A-4-284973,
The gap between the actual mechanical position and the timing due to the sampling process has not been solved.

Therefore, for the mechanical error between the "high-speed weaving" for optimum welding and the groove shape, the welding current and arc voltage are measured to perform "copy control" and arc output voltage control and It is necessary to perform pulse accent (pulse width and pulse current waveform collapse) prevention control.

[0005]

In the conventional pulse motor, high speed and high accuracy are impossible, and the number is at most 10 to 100.
With kpps, and in the control by the servo motor, there is a deviation (droop) between the command position to the servo and the actual mechanical position as shown in Fig. 11. Therefore, the welding current / voltage is measured (A) based on the timing of the weaving command. Even if (/ D sampling) is performed, the actual mechanical position and the timing of A / D sampling are deviated. Furthermore, the current and voltage at the left and right ends of the weaving could not be measured accurately.

The arc welding line copying in the pipe groove is composed of two elements, "vertical copying control" (hereinafter vertical copying) and "horizontal copying control" (hereinafter left and right copying). In the former case, the current may be monitored on average, and an appropriate averaging process is sufficient for A / D sampling. For the latter, the current must be measured at each of the left and right positions to correct the left-right position due to the difference in current at the left and right ends of the weaving.

In high-speed weaving, the difference (droop) between the command to the servo and the actual torch position becomes large, so the left and right are judged only by the command timing.
Even with / D sampling, the true left and right currents cannot be obtained.

For the above reasons, it is necessary to have a welding line tracing control method in the arc for accurately tracing the right and left in high speed weaving by a servo motor, and a method for controlling the output of the arc voltage and the pulse accent prevention control. is there.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a pipe circumference automatic welding apparatus for welding with a pulse welding current while weaving a welding torch in a direction orthogonal to the welding advancing direction. The control circuit is provided with a current / voltage data latch register 1 for A / D converting the current / voltage feedback signal and latching the data, and for the torch position control, the servo circuit is provided with position feedback from the encoder. A position data latch register 2 for latching the position counter value of the pulse signal is provided, and the sampling clock signal is used as a trigger to cause the registers 1 and 2 to latch the respective signals at the same timing and read the latched signal This is to enable optimal control of the arc corresponding to the position.

According to the present invention, the welding line tracing control in the arc is performed by the synchronous sampling of the weaving position and the arc current / voltage in the high speed weaving. That is, in high-speed weaving, the welding current / voltage at the left end and the right end is accurately measured in real time to perform high-speed and high-accuracy welding line copying control, as well as arc output voltage control and pulse accent prevention control.

[0011]

[Function] In the automatic pipe circumference welding device for high-speed weaving control, position counter data and welding current
By providing a circuit that completely synchronizes the voltage A / D conversion data in real time with the sampling clock and latches it, the welding line tracing control, arc output voltage control and pulse accent prevention control for the torch position are performed at high speed and high speed. The automatic circumference welding of precision pipes is possible.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a configuration diagram of an automatic pipe circumference welding apparatus. The outline of the welding apparatus according to the present invention will be described with reference to FIG.

A guide rail 3 is attached to the outer periphery of the pipe for performing pulse MAG automatic welding at the groove 2 portion of the welded material pipe 1, and a welding head 5 for maintaining a welding torch 4 is mounted on the guide rail 3. With NC control, the groove 2 of the pipe 1 is run over the entire circumference of the pipe 1 while weaving the welding torch 4, the welding position is corrected using the welding wire 6 as a touch sensor, and the welding arc is controlled during arc welding. Welding is performed while making corrections using line scanning. This welding work is applied to on-site work such as gas pipelines and nuclear piping, etc.Since automatic welding is carried out while traveling around the entire circumference of the pipe, the welding position changes all the time because it is welding in all positions. It is necessary to control with optimum welding conditions to obtain a uniform bead that corresponds to the posture and has no welding defects.

FIG. 2 shows a control program for creating the optimum automatic welding condition control program and the operation control flow chart therefor. By inputting design values such as pipe outer diameter, plate thickness, material, groove shape, etc., the logic table (welding conditions,
The parameters, algorithms, and program organization functions are stored in the controller 7 as a multi-layer automatic welding control program.

The welding head 5 is driven by a servo mechanism in the circumferential direction (X axis), the lateral direction (Y axis), and the vertical direction (Z axis). The control device 7 receives the welding power source and the monitor signal of the arc voltage from the welding power source 9 and measures them by A / D conversion to perform the welding line tracing control during the arc. In FIG. 1, 8 is a remote operation box, 10 is a power transmission cable, and 11 is a welding wire supply device.

First, the control of the torch position by following the welding line in the arc will be described. FIG. 3 shows the welding in the groove. Weaving the torch 4 left and right. When the torch 4 is located at the center of the groove 2, the detected currents on the left and right become equal, but if they are offset to either side, the current in the near side is large and the current in the far side is small. The "left-right copying" is to obtain the difference and control the position of the torch at the center of the groove. The torch control circuit diagram is shown in FIG.

The present invention will be described with reference to FIG. The current signal and the voltage signal are converted by the A / D converter 20 and latched in the register 1 (22) at the timing of the sampling clock 24. The Y-axis position feedback pulse is counted by the position counter 21 and latched in the register 2 (23) at the same timing (sampling clock 24). Although not shown, the voltage has a similar circuit configuration. Current (voltage) data 26 and position data 27
Are in perfect sync.

FIG. 6 shows the left and right positions during weaving and the course of the detected current (voltage) as a time flow. Control device 7
The internal left / right command position 30 and the actual mechanical position (torch position) 31 cause a time shift due to the droop of the servo system. The command 30 reaches the left end, and after a while, the actual mechanical position (torch position) 31 comes to the left end (same for the right). The black circles 31 and 32 show the state of synchronous sampling. In this way, the "actual mechanical position" 31 and the current (voltage) are synchronously sampled, the left end, the right end, the left side region, and the right side region are judged from the value of the mechanical position 31, and the current (voltage) value at that timing is determined. By using, it becomes possible to accurately measure the welding line in the arc and trace the welding line in the arc even at high speed weaving.

The details of the embodiment of the present invention will be described with reference to FIGS. 8 and 9. The circuit configuration is shown in FIG. 5, and the soft processing of sampling will be described with reference to FIG. The data (FIGS. 5-26, 27) latched by the sampling clock (FIGS. 5-24) is processed by software to be stored in the position data (POS _I ) on the ring buffer (FIGS. 8-40).
And current (voltage) de - storing a set of data (AD _I). I indicates a serial number for each sampling. The ring buffer stores the latest N sets of data and discards old data. When the operation for one cycle of weaving is completed, the value of POS _I is discriminated from the data for the previous one cycle, and the set of position data of “left side” and “right side” is selected.

In FIG. 8, 4 to 8 sets of data on the left side and 4 to 8 sets of data on the right side are selected, and A from them is selected.
The values of D _I are averaged to obtain “left current I _L ” and “right current I _R ”.
Has been created. The number of sets for averaging is determined appropriately from the ratio (n) of the "weaving period" and the period of the sampling clock. "Left side data" and "Right side data"
The remaining data except for is averaged to obtain the “average current Iav”.

In FIG. 9, from the values of “left current I _L ”, “right current I _R ”, and “average current I _aV ” obtained by the soft processing of FIG. Here is an example of an algorithm for performing ". In this example, a general P-I control method is used. "Left and right" I
Based on the difference between _L and I _R , its “proportional gain KY _P ”
And the integral of the difference and the “integral gain KY _I ” are multiplied to obtain a Y-axis correction amount (Y correction).

Equation 50; In the case of “up / down tracing”, similarly, based on the difference between the current command value (ICOM) and the detected average value (I _aV ), P
-I control is performed.

Equation 51; It is necessary to set an appropriate value for each gain (KY _P , KI _I , KZ _P , KZ _I ) in consideration of the current value and the unit of the position command of each axis. In this control device (Fig. 1-7), these gains and various constants in the control algorithm are
It has a means of freely setting and storing it.

Next, the pulse accent prevention control will be described.
As mentioned above, the pulse welding current is used for tracing the welding line in the arc, and during the vertical tracing of the torch position based on the data obtained by the latch, the arc voltage drops when the protruding length of the welding wire becomes long, and the pulse width becomes long. The pulse current becomes low and pulse accents as shown in FIG. 7 occur. When the welding line copying in the arc is started in this state, the logic is reversed (the command to raise the torch is issued), so the pulse accent cannot be stopped. Therefore, the welding line copying in the arc is terminated, the torch is lowered when the command voltage <output voltage + pulse correction, the command current <output current + pulse correction, to prevent pulse accentuation, and then the welding line copying in the arc is started. The width to lower the torch is 0.
It is 5 mm / time.

Next, the arc voltage output control will be described. The output of the arc voltage is controlled based on the data obtained by the latch. Arc voltage sampling cycle is 4m
sec, the average value of 64 samplings (256 msec) is compared with the arc output voltage set value, and the arc voltage is controlled with a voltage width of 0.2V. For example, when the average value of the sampling voltage is lower than the arc output set voltage,
The output voltage is increased by 0.2 V / cycle, and this is repeated to approach the voltage output set value. As described above, it is possible to control the welding line copying in the arc during high-speed weaving.

[0026]

According to the present invention, the following effects can be obtained. (1) High speed operation of several 100K _PPS by servo motor (1 _P = 1 μm, 400 K _PPS = 400 mm / sec) (2) Since sampling is performed in perfect synchronization with the clock,
The “position”, “current”, and “voltage” at each sampling are completely synchronized. (3) Real-time (several msec) due to interrupt processing (4) Based on the actual mechanical position, the left and right can be judged and the "current" and "voltage" values at that time can be used. Even in high-speed weaving, accurate and real-time control can be performed based on the difference between the left and right “current” and “voltage”. (5) Pulse accent prevention control and arc voltage output control can be performed based on the values of the "current" and "voltage."

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a pipe circumference automatic welding apparatus of the present invention.

FIG. 2 is a fully automatic welding flowchart of the present invention.

FIG. 3 is a groove portion simulation diagram of the torch of the present invention.

FIG. 4 is a torch control circuit diagram of the present invention.

FIG. 5 is a block diagram of a completely synchronous sampling circuit of the present invention.

FIG. 6 is a flow chart of the operation of fully synchronous sampling of the present invention.

FIG. 7 is a pulse waveform accent.

FIG. 8 is a current measurement by sampling during weaving according to the present invention.

FIG. 9 is a torch position control according to the welding line tracing (current measurement) in the arc of the present invention.

FIG. 10 is a conventional measurement readout of welding current / voltage value.

FIG. 11 shows conventional servo command positions and actual mechanical movements.

[Explanation of symbols]

1 ... Pipe 2 ... Groove 3 ... Guide rail 4 ... Welding torch 5 ... Welding head 6 ... Welding wire 7 ... Control device 8 ... Remote operation box 9 ... Welding power supply 10 ... Power transmission cable 11 ... Wire supply device 20 ... A / D Converter 21 ... Position counter 22 ... Register 1 23 ... Register 2 24 ... Sampling clock 25 ... Interrupt clock 26 ... Current (voltage) data 27 ... Position data 30 ... Command position 31 ... Actual mechanical position (torch position) 32 ... Current (Voltage) data

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location B23K 9/173 8315-4E B23K 9/173 C (72) Inventor Kenichi Maeda Tenjinbayashi, Hitachiota City, Ibaraki Prefecture Town 1225-47

Claims (2)

[Claims] 1. A pipe circumference automatic welding apparatus for welding a welding torch with a pulse welding current while weaving the welding torch in a direction orthogonal to the welding advancing direction, a feedback signal is supplied to a control circuit for the welding current and the arc voltage.
A current / voltage latch register 1 for D / D converting and latching the data is provided, a position data latch register 2 for latching the position counter value of the position feedback pulse signal of the servo circuit is provided for torch position control, and a sampling clock A welding line copying control method during arc in which a signal is used as a trigger to latch each data in both registers at the same timing, and the welding current and arc voltage are controlled in response to the position data latched at the same timing. 2. A process control method for performing pulse accent prevention control and arc voltage output control using the means of claim 1 during automatic operation by an automatic welding control program.