CN109848524B - Seam tracking method for gas shielded vertical welding with narrow gap - Google Patents

Abstract

The invention relates to a seam tracking method for gas shielded vertical welding with a narrow gap, belonging to the technical field of intelligent welding. The invention solves the problem that the existing mechanical stylus sensor is easily deformed by heat and cannot avoid the interference caused by the adhesion of metal particles to the sidewall of the groove. Due to the limited geometric size and depth of field, the sensor cannot extend into the groove to detect the root gap of large and thick plates or wall members. The invention obtains the initial current average value of the left, right and center welding torch rest positions of the groove as the benchmark data of the welding seam tracking, starts the welding seam tracking in a new welding cycle, and the PLC obtains the welding torch position after the welding is stable. When the welding torch stops on the left side of the groove, the real-time welding current is obtained, and the average value of the current is obtained according to the judged welding mode. After removing the singular point, it is compared with the reference data, and the welding torch height and the welding torch level are respectively tracked until the welding seam. Welding is complete. The present invention is used to track the weld seam.

Description

Seam tracking method for gas shielded vertical welding with narrow gap

technical field

The invention relates to a welding seam tracking method, which belongs to the technical field of intelligent welding.

Background technique

With the rapid popularization of high-capacity and high-parameter modern industrial equipment and major national projects, the large-scale, heavy-duty, high-strength, and thick-plate industrial equipment and steel structures have become the most important features of today's manufacturing industry. The amount of welding engineering has increased geometrically, and the contradiction between welding production efficiency, manufacturing cycle and manufacturing cost has become increasingly prominent. High-efficiency, high-quality and low-cost welding of large and heavy plates and extra-thick plates has become the forefront of today's manufacturing technology development.

Gas Metal Arc Welding (GMAW) with narrow gap has comprehensive technical advantages such as small groove filling area, high deposition efficiency, low welding heat input, and all-position welding. The best technical approach to the conflict between costs. Due to the narrow groove gap (usually within 20mm), it is difficult to repair. How to ensure low spatter during the welding process and stable fusion of the sidewalls of both sides of the groove is the key to narrow gap GMAW. At present, the development of digital power supply and waveform control technology can basically meet the welding requirements of narrow gap GMAW and low spatter. However, good and stable fusion of the groove side walls requires reliable and precise seam tracking technology.

In order to solve the problem of welding quality monitoring or welding seam tracking on the sidewall of narrow gap GMAW groove, the existing technologies mainly include the following five types: (1) Using a mechanical probe, the rotary potentiometer is used as an angular displacement sensor, and the position of the welding torch is adjusted. The offset is amplified and transformed into electricity through mechanical detection (probe or guide wheel), so as to judge whether the welding torch is strictly centered; (2) Capacitive sensors are used, and the capacitor voltage conversion, filtering, amplification, A/D conversion, etc. are used in turn, Extracting the longitudinal and lateral offset signals of the welding torch; (3) Using a laser vision sensor to collect bevel and arc images, and through image processing such as noise reduction, feature extraction, and pattern matching, the welding torch is guided through key point data. (4) Acoustic signal sensors are used to collect arc acoustic signals under different arc-side wall distances, and through signal noise reduction and processing, the characteristic quantities characterizing the arc-side wall distance are extracted to indirectly judge the alignment of the welding torch. (5) Using the arc sensor, based on the change law of the electric signal of the arc itself, the height and level deviation of the welding torch are judged by current sampling and comparison. The mechanical probe or guide wheel used in technology (1) is easily deformed by molten pool and arc radiation, and cannot avoid the interference caused by the adhesion of metal particles to the sidewall of the groove. It is mainly used for seam tracking of narrow-gap submerged arc welding. ; Technology (2) and technology (3) involve the installation of sensors and accessories, which are interfered by arc light, electromagnetic, spatter, smoke and dust during the arc welding process, and the accessibility and detection range of the welding torch are limited; technology (4) is easy to Due to environmental noise pollution at the production site, data management is difficult, and it is basically ineffective when used alone, and it cannot achieve accurate quantitative description; technology (5) is well applied in general thin plate butt joints or fillet joints, but the groove angle is basically required to be above 45° and It is mainly used in horizontal position welding arc tracking applications, which limits its application in narrow-gap GMAW. In recent years, domestic scientific research institutions have carried out research on narrow-gap GMAW arc tracking strategy, accuracy, stability, and real-time performance, and have achieved certain results, but they have basically stayed in the laboratory stage. Especially for the narrow gap GMA vertical welding seam tracking, there is no report, and technical breakthroughs and industrial applications are urgently needed.

SUMMARY OF THE INVENTION

The purpose of the present invention is to solve the problem that the existing mechanical stylus sensor is susceptible to thermal deformation and cannot avoid the interference caused by the adhesion of metal particles to the sidewall of the groove, and the laser vision sensor cannot extend into the groove to detect large thickness due to the limitation of geometric size and depth of field. The problem of the root gap of the plate or wall member provides a method for tracking the seam of the gas shielded vertical welding with narrow gap.

The method for tracking the welding seam of the narrow gap gas shielded vertical welding of the narrow gap of the present invention, the specific process of the welding seam tracking method is as follows:

S1. Input welding parameters and tracking parameters on the man-machine interface, and adjust the welding parameters and tracking parameters to meet the welding seam forming requirements by observing the arc stability and the fusion quality of the side walls on both sides of the groove;

S2. Turn on the welding torch, obtain the initial current mean value at the position where the welding torch stays on the left side of the groove, the initial current average value at the position where the welding torch stays on the right side of the groove, and the initial current average value at the position where the welding torch stays at the center of the groove, and put the three The average initial current is used as the benchmark data for welding seam tracking;

S3. Start welding seam tracking in a new welding cycle;

S4. The PLC obtains the position of the welding torch. When the welding torch stops on the left side of the groove, the signal acquisition module senses the welding current value through the current sensor, and sends the welding current value to the ARM processor;

S5. The ARM processor converts the current signal into a digital signal, and judges the welding mode according to the current variation law;

S6. According to the welding mode judged in S5, obtain the current mean value _IL at the left position of the groove at the stop position of the welding torch, the current mean value IR at the stop position of the welding _torch at the right side of the groove, and the current at the stop position of the welding torch at the center of the groove mean _IC ;

S7, convert the three current average values _IL , IR and _IC obtained in S6 into actual current values, and calculate the standard deviation of the three current average _{values IL} , _IR and _IC within the sampling period;

S8, remove the singular point of the current mean from the standard deviation obtained in S7, and recalculate the three current mean values _IL ', _IR ' and I _C ' after removing the singular point;

S9, the signal acquisition module sends the three current mean values _IL ', _IR ' and I _C ' that remove the singular point to the PLC through the serial port;

S10. Compare the mean value of the current obtained in S9 after removing the singular point with the reference data obtained in S2, respectively, and track the height of the welding torch and the level of the welding torch;

S11. Repeat S3-S10 until the seam welding is completed.

Preferably, the welding parameters in S1 include welding current, arc voltage, welding speed and swing parameters.

Preferably, the tracking parameters in S1 include the allowable fluctuation range of the current comparison amount and the offset correction displacement;

The allowable fluctuation range of the current comparison amount includes: the allowable fluctuation range σ of the current comparison amount of the welding torch height tracking process and the allowable fluctuation range of the current comparison amount of the welding torch level tracking process σ';

The rectification displacement includes: the rectification displacement δ in the process of tracking the height of the welding torch and the rectification displacement δ' in the horizontal tracking process of the welding torch.

Preferably, the specific process of S2 is:

S2-1. The PLC obtains the welding torch position after the welding is stable. When the welding torch stops on the left side of the groove, the signal acquisition module senses the welding current value through the current sensor, and sends the welding current value to the ARM processor;

S2-2. The ARM processor converts the current signal into a digital signal, and judges whether the welding starts according to the current variation law, and if so, judges the welding mode;

S2-3. According to the welding mode judged by S2-2, obtain the initial current mean value I _L0 at the stop position of the welding torch on the left side of the groove, the initial current mean value I _R0 at the stop position of the welding torch on the right side of the groove, and the center welding value of the groove The initial current mean value I _C0 at the torch stop position;

S2-4. Convert the three initial current mean values I _L0 , I _R0 and I _C0 obtained in S2-3 into actual current values, and calculate the standard deviation of the three initial current mean values I _L0 , I _R0 and I _C0 in the sampling period ;

S2-5, remove the singular point of the initial current mean value from the standard deviation obtained by S2-4, and recalculate the three initial current mean values I _L0 ', I _R0 ' and I _C0 ' after removing the singular point;

S2-6, the signal acquisition module sends the three initial current mean values I _L0 ', I _R0 ' and I _C0 ' with the singular point removed to the PLC through the serial port;

S2-7, the PLC backs up I _L0 ', I _R0 ' and I _C0 ' for the first time, and uses the I _L0 ', I _R0 ' and I _C0 ' backed up for the first time as the benchmark data for welding seam tracking.

Preferably, according to the welding mode described in S6, the basis for obtaining the three current mean _{values IL} , IR and _IC is:

When the welding mode is pulse mode, the current average value _IL at the stop position of the welding torch on the left side of the groove, the current average value IR at the stop position of the welding torch on the right side of the groove, and the stop position of the welding torch at the center of the groove are calculated according to the pulse cycle _. current mean value _IC at the location;

When the welding mode is non-pulse mode, the current mean value _IL at the left position of the welding torch on the groove, the current mean value IR at the position where the welding torch stops on the right side of the groove, and the groove center are calculated in a cycle of 10ms _. The current mean value _IC at the rest position of the torch.

Preferably, the specific process of tracking the height of the welding torch described in S10 is:

The PLC receives the current mean value I _C ' at the stop position of the groove center welding torch for removing the singular point, and makes a difference I _C '-I _C0 ' with the initial current mean value I _C0 ' at the stop position of the groove center welding torch for removing the singular point ;

Compare the difference I _C '-I _C0 ' with the allowable fluctuation range σ of the current comparator:

If I _C '-I _C0 '>σ, it means that the current welding torch height is low, and the PLC controls the welding torch to raise according to the rectification displacement δ;

If I _C '-I _C0 '<-σ, it indicates that the current welding torch height is too high, and the PLC controls the welding torch to decrease according to the rectification displacement δ.

Preferably, only one torch height tracking comparison is performed for each arc movement cycle.

Preferably, the specific process of tracking the level of the welding torch described in S10 is:

The PLC receives the current mean value _IL ' at the stop position of the welding torch on the left side of the groove and the current mean value IR ' at the stop position of the welding torch on the right side of the groove, and makes the difference _IL ' _-IR '= _A ;

The difference _IL0 '-I _R0 '=B between the initial current mean value I _L0 ' at the stop position of the welding torch on the left side of the groove and the initial current mean value I _R0 ' at the stop position of the welding torch on the right side of the groove after removing the singular point;

The difference between A and B is compared, and the difference obtained is compared with the allowable fluctuation range σ' of the current comparison quantity:

(I _L '-I _R ')-(I _L0 '-I _R0 ')>σ', it means that the current welding torch level is left to the left, and the PLC controls the welding torch to move to the right according to the correction displacement δ';

( _IL '-I _R ')-(I _L0 '-I _R0 ')<-σ', it means that the current welding torch is horizontally deviated to the right, and the PLC controls the welding torch to move to the left according to the correction displacement δ'.

Preferably, in each arc movement cycle, only one torch level tracking comparison is performed.

Advantages of the present invention: The present invention relates to a method for a welding torch to adaptively track grooves in a narrow gap MIG/MAG welding process for thick plate/thick-walled structural parts. The automatic tracking and correction of the torch height and horizontal direction is realized by collecting and calculating the current average value at the left and right sides of the left and right sides of each arc movement cycle and the center position of the groove under the welding steady state, which has the following advantages:

1. The welding torch does not need to install sensors and additional modules, and the accessibility is not affected;

2. This welding seam tracking method is suitable for swinging arc, rotating arc, swinging arc and other arc movement modes, and also suitable for different welding positions such as flat welding and vertical welding;

3. The standard deviation is used to remove the singular point of the current mean value, which effectively avoids the fluctuation of the welding process caused by the adhesion of metal particles on the side wall, and has high tracking reliability;

4. This tracking method is suitable for the welding torch with a height deviation of 0 to 2.5° and a horizontal deviation of 0 to 3.0°. Under the condition of reasonable parameter setting, the horizontal tracking accuracy can reach ±0.2mm, and the height tracking accuracy can reach ±0.5mm;

5. This tracking method is easy to integrate with automated special machines and robots, and meets the needs of high-efficiency, high-quality, and low-cost welding production of thick plate/thick-walled structural parts with narrow gap MGM vertical welding.

Description of drawings

Fig. 1 is the principle block diagram of the narrow gap gas shielded gas shielded vertical welding seam tracking method of the present invention;

Fig. 2 is the flow chart of the narrow gap gas shielded vertical welding seam tracking method of the present invention;

Fig. 3 is the welding seam tracking accuracy comparison curve diagram according to the third embodiment;

4 is a schematic diagram of the form of the double-sided narrow-gap gas shielded vertical welding groove of the high-strength steel extra-thick plate according to the fourth embodiment.

Detailed ways

Embodiment 1: The present embodiment will be described below with reference to FIG. 1 and FIG. 2 . The method for tracking the seam of gas shielded vertical welding with narrow gaps described in this embodiment, the specific process of the seam tracking method is as follows:

S1. Input welding parameters and tracking parameters on the man-machine interface, and adjust the welding parameters and tracking parameters to meet the welding seam forming requirements by observing the arc stability and the fusion quality of the side walls on both sides of the groove;

The welding parameters include welding current, arc voltage, welding speed and pendulum parameters.

The tracking parameters include the allowable fluctuation range of the current comparison amount and the correction displacement amount;

The allowable fluctuation range of the current comparison amount includes: the allowable fluctuation range σ of the current comparison amount of the welding torch height tracking process and the allowable fluctuation range of the current comparison amount of the welding torch level tracking process σ';

The rectification displacement includes: the rectification displacement δ in the process of tracking the height of the welding torch and the rectification displacement δ' in the horizontal tracking process of the welding torch.

S2. Turn on the welding torch, obtain the initial current mean value at the position where the welding torch stays on the left side of the groove, the initial current average value at the position where the welding torch stays on the right side of the groove, and the initial current average value at the position where the welding torch stays at the center of the groove, and put the three The average initial current is used as the benchmark data for welding seam tracking;

The specific process is:

S2-1. The PLC obtains the welding torch position after the welding is stable. When the welding torch stops on the left side of the groove, the signal acquisition module senses the welding current value through the current sensor, and sends the welding current value to the ARM processor;

S2-2. The ARM processor converts the current signal into a digital signal, and judges whether the welding starts according to the current variation law, and if so, judges the welding mode;

S2-3. According to the welding mode judged by S2-2, obtain the initial current mean value I _L0 at the stop position of the welding torch on the left side of the groove, the initial current mean value I _R0 at the stop position of the welding torch on the right side of the groove, and the center welding value of the groove The initial current mean value I _C0 at the torch stop position;

S2-4. Convert the three initial current mean values I _L0 , I _R0 and I _C0 obtained in S2-3 into actual current values, and calculate the standard deviation of the three initial current mean values I _L0 , I _R0 and I _C0 in the sampling period ;

S2-5, remove the singular point of the initial current mean value from the standard deviation obtained by S2-4, and recalculate the three initial current mean values I _L0 ', I _R0 ' and I _C0 ' after removing the singular point;

S2-6, the signal acquisition module sends the three initial current mean values I _L0 ', I _R0 ' and I _C0 ' with the singular point removed to the PLC through the serial port;

S2-7, the PLC backs up I _L0 ', I _R0 ' and I _C0 ' for the first time, and uses the I _L0 ', I _R0 ' and I _C0 ' backed up for the first time as the benchmark data for welding seam tracking.

According to S2-3, according to the welding mode, the initial current mean value I _L0 at the left position of the groove, the initial current mean value I _R0 at the position of the welding torch at the right side of the groove, and the initial current mean value I R0 at the position of the welding torch at the center of the groove are obtained. The basis of the initial current mean value I _C0 is:

When the welding mode is pulse mode, according to the pulse period, the initial current average value I _L0 at the left position of the groove welding torch, the initial current average value I _R0 at the welding torch position on the right side of the groove and the groove center welding position are obtained respectively. The initial current mean value I _C0 at the torch stop position;

When the welding mode is non-pulse mode, the initial current mean value I _L0 at the left position of the welding torch at the groove, the initial current mean value I _R0 at the position where the welding torch rests on the right side of the groove, and the slope The initial mean current I _C0 at the stop position of the torch in the center of the mouth.

S3. Start welding seam tracking in a new welding cycle;

S4. The PLC obtains the position of the welding torch. When the welding torch stops on the left side of the groove, the signal acquisition module senses the welding current value through the current sensor, and sends the welding current value to the ARM processor;

S5. The ARM processor converts the current signal into a digital signal, and judges the welding mode according to the current variation law;

S6. According to the welding mode judged in S5, obtain the current mean value _IL at the left position of the groove at the stop position of the welding torch, the current mean value IR at the stop position of the welding _torch at the right side of the groove, and the current at the stop position of the welding torch at the center of the groove mean _IC ;

S7, convert the three current average values _IL , IR and _IC obtained in S6 into actual current values, and calculate the standard deviation of the three current average _{values IL} , _IR and _IC within the sampling period;

S8, remove the singular point of the current mean from the standard deviation obtained in S7, and recalculate the three current mean values _IL ', _IR ' and I _C ' after removing the singular point;

S9, the signal acquisition module sends the three current mean values _IL ', IR ' and I _C ' that remove the _singularity to the PLC through the serial port;

S10, compare the current mean value obtained in S9 after removing the singular point with the benchmark data obtained in S2, respectively, and track the height of the welding torch and the level of the welding torch;

The specific process of tracking the height of the welding torch is as follows:

The PLC receives the current mean value I _C ' at the stop position of the groove center welding torch for removing the singular point, and makes a difference I _C '-I _C0 ' with the initial current mean value I _C0 ' at the stop position of the groove center welding torch for removing the singular point ;

Compare the difference I _C '-I _C0 ' with the allowable fluctuation range σ of the current comparator:

If I _C '-I _C0 '>σ, it means that the current welding torch height is low, and the PLC controls the welding torch to raise according to the rectification displacement δ;

If I _C '-I _C0 '<-σ, it indicates that the current welding torch height is too high, and the PLC controls the welding torch to decrease according to the rectification displacement δ.

The specific process of tracking the torch level is as follows:

The PLC receives the current mean value _IL ' at the stop position of the welding torch on the left side of the groove and the current mean value IR ' at the stop position of the welding torch on the right side of the groove, and makes the difference _IL ' _-IR '= _A ;

The difference _IL0 '-I _R0 '=B between the initial current mean value I _L0 ' at the stop position of the welding torch on the left side of the groove and the initial current mean value I _R0 ' at the stop position of the welding torch on the right side of the groove after removing the singular point;

The difference between A and B is compared, and the difference obtained is compared with the allowable fluctuation range σ' of the current comparison quantity:

(I _L '-I _R ')-(I _L0 '-I _R0 ')>σ', it means that the current welding torch level is left to the left, and the PLC controls the welding torch to move to the right according to the correction displacement δ';

( _IL '-I _R ')-(I _L0 '-I _R0 ')<-σ', it means that the current welding torch is horizontally deviated to the right, and the PLC controls the welding torch to move to the left according to the correction displacement δ'.

S11. Repeat S3-S10 until the seam welding is completed.

Embodiment 2: This embodiment further describes Embodiment 1. In each arc movement cycle, only one torch height tracking comparison is performed; in each arc movement cycle, only one welding torch level tracking comparison is performed.

Embodiment 3: This embodiment will be described below with reference to FIG. 3 . This embodiment will further describe Embodiment 1. A709-50-2 with a thickness of 50mm is placed on a milling machine to process a simulated slope with a width x depth of 20 x 8.5mm. The bottom of the test plate is inclined by 5mm in the horizontal direction (1.6° inclination) and 6mm in the height direction of the welding torch (1.6° inclination) by means of spacers. Use MG-S88A welding wire with a diameter of 1.2mm, Panasonic YD-500GS4 as welding power source, shielding gas 85%Ar+15%CO ₂ , shielding gas flow 15~20L/min(gun)+30~40L/min(hood) . During welding, the robot carries the narrow-gap GMA welding torch for translational motion along the groove length direction and groove depth direction, and the movement in the groove width direction is realized by the rotation and swing mechanism of the narrow-gap welding torch. The implementation process of seam tracking effect of narrow gap swing arc GMA vertical welding is as follows:

On the man-machine interface of the welding seam tracking system, manually adjust the welding parameters (including welding current, arc voltage, welding speed and swing parameters) and tracking parameters (including the allowable fluctuation range σ/σ' and correction displacement of the current comparison value quantity δ/δ'), as shown in Table 1 and Table 2:

Table 1

Table 2

Observe the arc stability of the gas shielded vertical welding with narrow gap and the fusion quality of the sidewalls on both sides of the groove until the welding seam forming requirements are met.

The arc tracking of the gas shielded vertical welding with narrow gap has good results in the actual measurement. At the same time, during the welding tracking process, draw a straight line (theoretical) of the welding seam deviation according to the position measurement. After the tracking is turned on, the tracking center position is read and the actual centerline position deviation is calculated. The value is taken once for each arc movement cycle. By comparing the theoretical weld deviation straight line with the actual centerline position, the welding seam tracking accuracy is calculated, as shown in Figure 3. It can be seen that the horizontal tracking accuracy of the system can reach ±0.2mm, and the height tracking accuracy can reach ±0.5mm, which meets the requirements of the narrow-gap MIG-MAG vertical welding process.

Embodiment 4: The present embodiment will be described below in conjunction with FIG. 4 . This embodiment will further describe the first embodiment, and the application object is the 177.8mm thick high-quality advanced quenched and tempered high-strength steel extension process evaluation test for the legs of the self-elevating platform. , using double-sided single-filament narrow-gap gas shielded gas shielded vertical welding process. The high-quality marine engineering extra-thick plate is a 177.8mm thick rack steel DILLIMAX690E produced by German Dillinger Steel Company. The groove design is shown in Figure 4. The groove angle on one side is α=1.0°, the pairing gap δ=18mm, and the root is inverted. Angle R = 3.0mm, root blunt edge b = 3mm. Following the principle of "equal strength matching", MG-S88A welding wire with a diameter of 1.2mm is selected, the shielding gas is 85%Ar+15%CO2, and the shielding gas flow rate is 15~20L/min (gun)+30~40L/min (hood). During welding, the robot carries the narrow-gap MGM vertical welding torch for translational motion along the groove length and groove depth directions, and the groove width direction is realized by the rotation and swing mechanism of the narrow-gap welding torch. . The welding sequence is as follows: preheating before welding (preheating temperature is 160±10°C) → 3-4 layers of welding on the front side (the cumulative thickness of the welding layer is about 15mm, and the temperature between layers is 180±10°C) → root cleaning on the back side (root cleaning Depth to the front to play the bottom layer) → Weld on the back until the thickness of the welding layer on both sides of the groove is basically the same → Weld symmetrically on both sides until the end → Dehydrogenation treatment (heating temperature is 250 ± 50 ℃, heat preservation for 2h). The implementation process of the welding seam tracking effect of the narrow gap gas shielded vertical welding of high-strength steel extra-thick plates is as follows:

On the man-machine interface of the welding seam tracking system, manually adjust the welding parameters (including welding current, arc voltage, welding speed and swing parameters) and tracking parameters (including the allowable fluctuation range σ/σ' and correction displacement of the current comparison value quantity δ/δ'), as shown in Table 3 and Table 4:

table 3

Table 4

Observe the arc stability of the narrow gap GMA vertical welding and the fusion quality of the sidewalls on both sides of the groove until the weld forming requirements are met.

A total of 50 layers were welded, with 24 layers on the front and 26 layers on the back. Ultrasonic and magnetic particle inspections were carried out 72 hours after welding, and the inspection results showed that the welded joints had no internal welding defects and surface welding cracks. At the same time, the macroscopic inspection of multiple sets of joint macro-samples was planed, polished and eroded, and no defects were found in all sections. The welding layer is clear, the width and thickness of the welding layer are uniform, and the sidewall is well fused.

The invention collects and calculates the current average value at the left and right sides of each arc moving cycle and the center position of the groove under the welding stable state, and compares the difference to realize the automatic tracking and correction of the height of the welding torch and the horizontal direction. Under the condition of reasonable parameter setting, the horizontal tracking accuracy of the system can reach ±0.2mm, and the height tracking accuracy can reach ±0.5mm, which can meet the requirements of high-efficiency, high-quality and low-cost welding of thick plate/thick-walled structural parts with narrow gap MGM vertical welding. production needs.

In the present invention, the torch height (arc length) tracking principle is: when the dry wire elongation increases, the welding current decreases; when the wire dry elongation decreases, the welding current increases. Under ideal conditions, when the height of the welding torch is constant, the real-time current mean value I _C ' at the center of the welding seam and the reference value I _C0 ' are within the allowable fluctuation range, that is, I _C '-I _C0 '≤σ; When the torch is raised or lowered, the difference between the real-time current mean value I _C ' at the center of the welding seam and the reference value I _C0 ' will exceed the allowable range, that is, I _C '-I _C0 '>σ, and the arc length tracking mechanism will be activated. If I _C '-I _C0 '>σ, it means that the height of the welding torch is low, and the control torch is raised; on the contrary, if I _C '-I _C0 '<-σ, it means that the height of the welding torch is high, and the control torch is lowered.

In the present invention, the welding torch horizontal (centering) tracking principle is similar to arc length tracking. Under ideal conditions, when the welding torch is centered on the center of the welding seam, the difference _IL ′ between the real-time current mean values of the remaining positions on both sides of the groove horizontal -I _R ' and the reference value I _L0 '-I _R0 ' are within the allowable fluctuation range, ie (I _L '-I _R ')-(I _L0 '-I _R0 ')≤σ'; When deviating or deviating to the right, the difference between the real-time current mean value I _L '-I _R ' and the reference difference I _L0 '-I _R0 ' will exceed the allowable range, that is, (I _L '- I R0 ' IR ')-(I _L0 '-I _R0 ')>σ', start the _centering tracking mechanism. If (I _L '-I _R ')-(I _L0 '-I _R0 ')>σ', it indicates that the welding torch is horizontally deviated to the left, and the welding torch is controlled to move to the right; otherwise, (I _L '-I _R ')-( I _L0 '-I _R0 ')<-σ', indicating that the welding torch is horizontally deviated to the right, and the welding torch is controlled to move to the left.

Before controlling the torch rectification execution motor, first adjust the parameters through the human-computer interface until the welding requirements are met, and then the tracking system senses the current signal of the narrow gap MIG-GAP vertical welding process through the current sensor, and uses the ARM processor to collect and obtain each The current average value at the left and right sides of the arc moving cycle and the center position of the groove, and then send the current average value to the PLC through the serial port; after the PLC receives the data, the current average value of the three positions is backed up as the tracking reference, and Perform a series of operations with the real-time average value of welding current obtained later, and according to the comparison results, control the height of the welding torch and the servo drive unit in the horizontal direction to carry out correction adjustment.

Claims (9)

1. The method for tracking the welding seam of the narrow-gap gas metal arc vertical welding is characterized by comprising the following specific processes:

s1, inputting welding parameters and tracking parameters on a human-computer interaction interface, and adjusting the welding parameters and the tracking parameters to meet the welding seam forming requirements by observing the stability of the electric arc and the fusion quality of the side walls of the two sides of the groove;

s2, starting the welding torch, obtaining an initial current mean value at the left side of the groove at the position where the welding torch stays, an initial current mean value at the right side of the groove at the position where the welding torch stays and an initial current mean value at the center of the groove at the position where the welding torch stays, and taking the three initial current mean values as datum data for welding seam tracking;

s3, starting weld joint tracking in a new welding period;

s4, the PLC acquires the position of the welding torch, and when the welding torch stops at the left side of the groove, the signal acquisition module senses the welding current value through the current sensor and sends the welding current value to the ARM processor;

s5, the ARM processor converts the current signal into a digital signal and judges the welding mode according to the current change rule;

s6, obtaining the current mean value I of the left welding torch of the groove at the stop position according to the welding mode judged by S5_LMean value of current I at the position where welding torch stays on the right side of groove_RAnd the mean value I of the current at the stay position of the welding torch at the center of the groove_C；

S7, obtaining three current mean values I obtained in S6_L、I_RAnd I_CConverting into actual current value, and calculating three current average values I in sampling period_L、I_RAnd I_CStandard deviation of (d);

s8, removing the specific points of the current mean value from the standard deviation obtained in S7, and recalculating the three current mean values I after the specific points are removed_L'、I_R' and I_C'；

S9, the signal acquisition module removes three current mean values I of the special points through the serial port_L'、I_R' and I_C' send to PLC;

s10, comparing the current mean value obtained in the S9 after the special points are removed with the reference data obtained in the S2, and tracking the height and the level of the welding torch respectively;

and S11, repeatedly executing S3-S10 until the welding of the welding seam is finished.

2. The narrow gap gas metal arc vertical welding seam tracking method according to claim 1, wherein the welding parameters of S1 include welding current, arc voltage, welding speed and swing parameters.

3. The narrow-gap gas metal arc vertical welding seam tracking method according to claim 1 or 2, wherein the tracking parameters of S1 comprise allowable fluctuation range of current comparison quantity and deviation correction displacement quantity;

wherein the allowable fluctuation range of the current comparison quantity comprises: tracking the allowable fluctuation range sigma of the process current comparison quantity for the height of the welding torch and tracking the allowable fluctuation range sigma' of the process current comparison quantity for the level of the welding torch;

the deviation correcting displacement comprises the following steps: and (3) tracking the deviation correcting displacement of the welding torch in the height tracking process and tracking the deviation correcting displacement of the welding torch in the horizontal tracking process.

4. The narrow-gap gas metal arc vertical welding seam tracking method according to claim 3, characterized in that the specific process of S2 is as follows:

s2-1, acquiring the position of the welding torch after the welding is stable by the PLC, sensing the welding current value by the signal acquisition module through the current sensor when the welding torch stops at the left side of the groove, and sending the welding current value to the ARM processor;

s2-2, the ARM processor converts the current signal into a digital signal, judges whether welding starts or not according to a current change rule, and judges a welding mode if the welding starts;

s2-3, obtaining the initial current mean value I at the position where the welding torch at the left side of the groove stays according to the welding mode judged by S2-2_L0Initial current mean value I at the position where welding torch stays on the right side of groove_R0And the mean value I of the initial current at the stay position of the welding torch at the center of the groove_C0；

S2-4, obtaining three initial current mean values I from S2-3_L0、I_R0And I_C0Converting into actual current value, and calculating three initial current average values I in sampling period_L0、I_R0And I_C0Standard deviation of (d);

s2-5, removing the specific points of the initial current mean value from the standard deviation obtained in the step S2-4, and recalculating the three initial current mean values I after the specific points are removed_L0'、I_R0' and I_C0'；

S2-6, the signal acquisition module removes the three initial current mean values I of the special points through the serial port_L0'、I_R0' and I_C0' send to PLC;

s2-7, PLC will I_L0'、I_R0' and I_C0' make first backup, with first backup I_L0'、I_R0' and I_C0' as reference data for seam tracking.

5. The narrow gap gas metal arc vertical welding seam tracking method according to claim 1, wherein the welding mode determined according to the step S5 of S6 is used for obtaining three current mean values I_L、I_RAnd I_CThe basis of (A) is as follows:

when the welding mode is a pulse mode, respectively obtaining the current average value I at the staying position of the welding torch on the left side of the groove according to the pulse period_LMean value of current I at the position where welding torch stays on the right side of groove_RAnd the mean value I of the current at the stay position of the welding torch at the center of the groove_C；

When the welding mode is a non-pulse mode, respectively obtaining the current average value I at the stay position of the welding torch on the left side of the groove according to a period of 10ms_LMean value of current I at the position where welding torch stays on the right side of groove_RAnd the mean value I of the current at the stay position of the welding torch at the center of the groove_C。

6. The narrow gap gas metal arc vertical welding seam tracking method according to claim 4, wherein the specific process of tracking the welding torch height in S10 is as follows:

the PLC receives the current mean value I at the staying position of the welding torch at the center of the groove with the specific point removed_C', mean value of initial current I at position where the central torch of the groove stops with the specific point removed_C0' making a difference I_C'-I_C0'；

Will be different from the difference value I_C'-I_C0' comparison with the allowable fluctuation range σ of the current comparison amount:

I_C'-I_C0' > σ indicates that the current torch is low in height, PThe LC controls the welding torch to rise according to the deviation correcting displacement;

I_C'-I_C0' less than-sigma, it indicates that the current welding torch is higher in height, and the PLC controls the welding torch to be lowered according to the deviation correcting displacement.

7. The narrow gap gas metal arc vertical weld tracking method of claim 6, wherein only one torch height tracking comparison is performed per arc travel cycle.

8. The narrow gap gas metal arc vertical welding seam tracking method according to claim 4, wherein the specific process of tracking the welding torch level in S10 is as follows:

the PLC receives the current mean value I at the stay position of the welding torch at the left side of the groove with the special point removed_L' and mean value of current I at the position where welding torch stays on the right side of groove_R', do not make a difference I_L'-I_R'＝A；

The mean value I of the initial current at the stay position of the welding torch at the left side of the groove with the special point removed_L0' and initial current mean value I at the torch stopping position on the right side of groove_R0' making a difference I_L0'-I_R0'＝B；

And (3) comparing the difference between A and B with the allowable fluctuation range sigma' of the current comparison quantity:

(I_L'-I_R')-(I_L0'-I_R0') is greater than sigma', indicating that the current welding torch is horizontally deviated to the left, and the PLC controls the welding torch to move to the right according to the deviation-rectifying displacement;

(I_L'-I_R')-(I_L0'-I_R0') < -sigma', indicating that the current welding torch is horizontally deviated to the right, and the PLC controls the welding torch to move to the left according to the deviation correcting displacement.

9. The narrow gap gas metal arc vertical weld tracking method of claim 8, wherein only one torch level tracking comparison is performed per arc movement cycle.

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