Closed-loop pulse GTAW large-gap weld joint welding system based on vision-arc perception

Abstract

The invention relates to the field of large-gap GTAW welding, in particular to a closed-loop pulse GTAW large-gap welding system and method based on vision-electric arc perception. The invention relates to the field of large-gap GTAW welding and discloses a closed-loop pulse GTAW large-gap welding system and method based on vision-electric arc perception. The invention provides a closed-loop pulse GTAW large-gap welding seam welding system and a closed-loop pulse GTAW large-gap welding seam welding method, aiming at the bad influence of welding wire, welding gun and electric arc deviation on welding seam forming in large-gap GTAW welding seam welding. A closed-loop pulse GTAW pulse frequency control method based on visual sense and electric arc cooperative perception is used for controlling the pulse frequency; the arc length is controlled through a pulse GTAW arc length control method based on electric arc and visual cooperative perception; the number of welding spots is calculated through a closed-loop pulse GTAW large-gap welding seam one-way welding spot number calculation method based on structured light vision sensing; wire feeding is controlled through a closed-loop pulse GTAW large-gap welding seam welding wire feeding method based on welding wire sensing; and the moving distance in the welding direction is calculated through a welding direction moving distance calculation method based on structured light visual sensing.

Description

Technical Field

[0001] The present invention relates to the field of GTAW welding of large-gap welds, and is a closed-loop pulsed GTAW large-gap weld welding system and method based on vision-arc sensing. Background Art

[0002] GTAW (Gas Tungsten Arc Welding) is widely used in fields such as aerospace, marine engineering equipment, and nuclear power construction. Especially in recent years, with the rapid development of arc additive manufacturing technology, higher requirements have been put forward for the automation and intelligence of wire-fed GTAW. In GTAW welding of large gaps, the wire, welding torch, and arc posture have a crucial impact on the weld formation. The present invention discloses a closed-loop pulsed GTAW large-gap weld welding system based on vision-arc sensing, which controls the wire, welding torch, and arc during the welding process to improve the stability of the welding process and the weld quality. Summary of the Invention

[0003] A closed-loop pulsed GTAW large-gap weld welding system based on vision-arc sensing, used for GTAW large-gap weld welding, is characterized in that: the closed-loop pulsed GTAW large-gap weld welding system based on vision-arc sensing is composed of a GTAW robot, a vision system, a welding torch system, a wire feeding system and a central control system; the GTAW robot is composed of an X-direction guide rail, a Y-direction guide rail and a V-shaped mounting plate; the V-shaped mounting plate can move forward and backward along the X-direction guide rail and move left and right along the Y-direction guide rail; the V-shaped mounting plate includes a welding torch moving guide rail mounting position, a wire moving guide rail mounting position and a vision system mounting position; the vision system is composed of a structured light vision sensor and a passive vision sensor, and is fixed at the vision system mounting position; the structured light vision sensor is composed of a CCD camera and a line laser; the welding torch system is composed of a welding torch rotary joint, a welding torch slide and a welding torch; the welding torch rotary joint can rotate 360° and is fixedly connected to the welding torch; the welding torch slide is fixedly connected to the welding torch rotary joint and can move along the welding torch moving guide rail; the central control system controls the welding torch attitude by controlling the rotation of the welding torch rotary joint and the displacement of the welding torch slide; the wire feeding system is composed of a wire feeding rotary joint, a wire feeding slide and a wire feeding tube; the wire feeding rotary joint can rotate 360° and is fixedly connected to the wire feeding tube; the wire feeding slide is fixedly connected to the wire feeding rotary joint and can move along the wire moving guide rail; the central control system controls the wire feeding tube attitude by controlling the rotation of the wire feeding rotary joint and the displacement of the wire feeding slide; the central control system is composed of an industrial computer, a signal acquisition system, a communication bus and a control bus; the central control system can collect arc signals, and the arc signals include the arc voltage signal at the wire end and the arc voltage signal at the tungsten electrode end, and can control the GTAW robot, the vision system, the welding torch system and the wire feeding system; the arc voltage signal at the wire end is the arc voltage from the wire tip to the workpiece surface; the arc voltage signal at the tungsten electrode end is the arc voltage from the tungsten electrode tip to the workpiece surface. The closed-loop pulsed GTAW large-gap weld welding system based on vision-arc sensing is as Figure 1 shown.

[0004] Closed-loop pulsed GTAW large-gap weld welding system based on vision-arc sensing, characterized in that: in the closed-loop pulsed GTAW large-gap weld welding system based on vision-arc sensing, the pulse frequency is controlled by a closed-loop pulsed GTAW pulse frequency control method based on collaborative sensing of vision and arc; the closed-loop pulsed GTAW pulse frequency control method based on collaborative sensing of vision and arc controls the pulse frequency by controlling the time T of the pulse period through a central control system; the pulse period time T consists of an arc length adjustment time T1, a droplet transfer time T2, and a moving torch time T3; T = T1 + T2 + T3; an operation of one pulse period is: the central control system controls the GTAW robot to perform an arc starting operation and simultaneously starts collecting arc signals, performs closed-loop adjustment of the arc length through the arc signals and vision signals collected in real time, when the central control system monitors through the vision system that the base metal reaches the molten state, controls the wire feeding system to deliver filler metal to the molten pool area with preset parameters, after the droplet transfer is completed, extinguishes the arc, and the central control system controls the torch to move to the next arc starting point. The flow chart of one pulse period is as Figure 2 shown.

[0005] Closed-loop pulsed GTAW large-gap weld welding system based on vision-arc sensing, characterized in that: in the closed-loop pulsed GTAW large-gap weld welding system based on vision-arc sensing, the arc length is controlled by a pulsed GTAW arc length control method based on collaborative sensing of arc and vision; the pulsed GTAW arc length control method based on collaborative sensing of arc and vision controls the arc length by controlling the position of the torch system to change the position of the torch through a central control system; after welding starts, in one pulse period, the central control system first controls the torch to perform an arc starting operation, after the arc starting is successful, the central control system raises the torch height to H according to the tungsten electrode end arc voltage signal collected in real time, for each droplet transfer completed, the central control system controls the torch to move to the right by a weld bead thickness D, after all droplet transfers are completed, the central control system controls the torch to extinguish the arc, and then according to the data collected by the structured light vision sensor, moves the torch downward by a distance H and at the same time makes the torch reach the starting point of the next pulse period; there is a relationship of L = F(U) between the tungsten electrode end arc voltage and the arc length, where L is the arc length and U is the tungsten electrode end arc voltage; the central control system realizes the lifting of the torch by controlling the torch slide in the torch system to move on the torch moving guide rail, and realizes the left and right displacement of the torch by controlling the V-shaped mounting plate in the GTAW robot to move on the Y-direction guide rail; after extinguishing the arc, the line laser projects a laser parallel to the welding direction through the center of the weld bead, and the CCD camera takes an image and transmits it to the central control system, and the central control system obtains the weld bead thickness D after processing.

[0006] Closed-loop pulsed GTAW large-gap weld welding system based on vision-arc sensing, characterized in that: in the closed-loop pulsed GTAW large-gap weld welding system based on vision-arc sensing, the number of one-way weld spots is calculated by the calculation method of the number of one-way weld spots of closed-loop pulsed GTAW large-gap welds based on structured light vision sensing; the calculation method of the number of one-way weld spots of closed-loop pulsed GTAW large-gap welds based on structured light vision sensing processes the vision signals through the central control system to calculate the number of one-way weld spots of the large-gap weld; after welding starts, the line laser projects a laser parallel to the welding direction and passing through the starting weld spot; the CCD camera receives the distorted light strip and transmits the image information to the central control system; the central control system corrects the distortion and then extracts the center line of the laser line, and obtains the workpiece gap length M through image processing; after completing the first weld spot, the central control system obtains the thickness D of the weld spot after processing and calculates the number of weld spots n; the number of weld spots is obtained through obtained; during the subsequent welding process, n is decreased by 1 every time a droplet transfer is completed; when n is 0, it is determined that one weld seam is completed. The schematic diagram of the weld spot thickness D is as shown in Figure 3 shown.

[0007] Closed-loop pulsed GTAW large-gap weld welding system based on vision-arc sensing, characterized in that: in the closed-loop pulsed GTAW large-gap weld welding system based on vision-arc sensing, the wire feeding length is controlled by the wire feeding method of closed-loop pulsed GTAW large-gap welds based on wire sensing; the wire feeding method of closed-loop pulsed GTAW large-gap welds based on wire sensing controls the wire feeding system through the central control system to change the wire feeding speed to achieve continuous liquid-bridge transfer; the droplet transfer state is judged by the arc voltage signal at the wire end; during the droplet transfer process, when the wire arc voltage is close to 0V, it is judged that the droplet is transferring in the liquid-bridge transfer mode, and the wire feeding speed remains unchanged; when the wire arc voltage during the droplet transfer process is higher than 0V, it is judged that the droplet is transferring in the free flight state, and the wire feeding speed is increased until the droplet transfers in the liquid-bridge transfer mode; before starting wire feeding, the industrial camera takes a real-time image of the molten pool and transmits it to the central control system, and the central control system obtains the real-time molten pool area S 实 , when S 实 is greater than the preset molten pool area S 预 , wire feeding starts; before welding starts, the wire feeding length I for one pulse period is preset according to the material and diameter of the wire, and the central control system monitors the wire feeding length in real time. When the wire feeding length reaches I, the wire feeding stops.

[0008] Closed-loop pulsed GTAW large-gap weld welding system based on vision-arc sensing, characterized in that: in the closed-loop pulsed GTAW large-gap weld welding system based on vision-arc sensing, the moving distance in the welding direction is calculated by the moving distance calculation method in the welding direction based on structured light vision sensing; the moving amount is the longitudinal moving amount in the positive direction of the X-axis and the transverse moving amount in the negative direction of the Y-axis; the longitudinal moving amount is the width of the previous weld; the weld width is obtained after the central control system processes the image information transmitted by the structured light vision sensor; the line laser projects laser perpendicular to the welding direction, and the structured light vision sensor receives the distorted light strip and transmits the image information to the central control system; after the central control system corrects the distortion, it extracts the center line of the laser line, and obtains the weld width N through image processing; the transverse moving amount is the workpiece gap length M; before welding starts, the workpiece gap M is detected, and the workpiece gap M is obtained after the central control system processes the image information transmitted by the structured light vision sensor; the line laser projects laser parallel to the welding direction, and the structured light vision sensor receives the distorted light strip and transmits the image information to the central control system; after the central control system corrects the distortion, it extracts the center line of the laser line, and obtains the workpiece gap M by establishing a conversion model from the image coordinate system to the camera coordinate system; after the central control system calculates the moving distance, it moves the welding torch to the starting point of the next weld. The schematic diagrams of the weld width N and the workpiece gap M are as shown in Figure 4 shown.

[0009] Advantages of the invention

[0010] The present invention relates to the field of large-gap GTAW weld welding, and is a closed-loop pulsed GTAW large-gap weld welding system and method based on vision-arc sensing. Aiming at the adverse effects caused by the deviation of the welding wire, welding torch and arc on the weld formation in large-gap GTAW weld welding, a closed-loop pulsed GTAW large-gap weld welding system and method are proposed. The pulse frequency is controlled by the closed-loop pulsed GTAW pulse frequency control method based on the collaborative sensing of vision and arc; the arc length is controlled by the pulsed GTAW arc length control method based on the collaborative sensing of arc and vision; the number of weld spots is calculated by the closed-loop pulsed GTAW large-gap weld single-direction weld spot number calculation method based on structured light vision sensing; the wire feeding is controlled by the closed-loop pulsed GTAW large-gap weld welding wire feeding method based on wire sensing; the moving distance in the welding direction is calculated by the moving distance calculation method in the welding direction based on structured light vision sensing. Description of the drawings

[0011] Figure 1 It is a schematic diagram of a closed-loop pulsed GTAW large-gap weld welding system based on vision-arc sensing.

[0012] In the figure, 1 is the central control system, 2 is the X-direction guide rail, 3 is the welding wire, 4 is the wire feeding tube, 5 is the welding wire rotary joint, 6 is the welding wire moving guide rail, 7 is the welding wire sliding seat, 8 is the V-shaped mounting plate, 9 is the vision system, 10 is the welding torch moving guide rail, 11 is the welding torch sliding seat, 12 is the Y-direction guide rail, 13 is the welding torch rotary joint, 14 is the welding torch, 15 is the workpiece, 16 is the working platform, 17 is the communication bus, and 18 is the control bus.

[0013] Figure 2 It is a flowchart of a pulse period.

[0014] Figure 3 It is a schematic diagram of the weld spot thickness D.

[0015] Figure 4 It is a schematic diagram of the weld width N and the workpiece gap M. Specific implementation mode

[0016] In order to better express the technical solution and beneficial effects of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and implementation cases. The implementation method of the present invention is not limited thereto.

[0017] Step 1: Pulse frequency control.

[0018] In the closed-loop pulsed large-gap weld GTAW welding process based on vision-arc sensing, it is necessary to control the pulse frequency. If the pulse frequency is unreasonable, it will lead to unstable welding process and reduced welding quality. To solve this problem, the present invention discloses a closed-loop pulsed GTAW pulse frequency control method based on the collaborative sensing of vision and arc. Before the start of a pulse period, by setting the arc length adjustment time T1, the droplet transfer time T2, and the moving welding torch time T3, the pulse period time T is made to be within a reasonable range.

[0019] Step 2: Arc length control.

[0020] In the closed-loop pulsed large-gap weld GTAW welding process based on vision-arc sensing, it is necessary to control the arc length. If the arc length is too high, the workpiece cannot be fully melted. If the arc length is too low, the penetration will be too large. To solve this problem, the present invention discloses a pulsed GTAW arc length control method based on the collaborative sensing of arc and vision. Since there is a corresponding relationship between the arc voltage at the tip of the tungsten electrode and the arc length, while monitoring the tungsten electrode arc voltage, the arc length is adjusted by adjusting the distance from the tip of the tungsten electrode to the workpiece.

[0021] Step 3: Weld spot number calculation.

[0022] In the GTAW welding process of closed-loop pulsed large-gap welds based on vision-arc sensing, the present invention discloses a method for calculating the number of single-direction weld spots of closed-loop pulsed GTAW large-gap welds based on structured light vision sensing. After welding starts, the central control system obtains the workpiece gap length M and the weld spot thickness D through image processing, and calculates the number of weld spots through the formula During the subsequent welding process, every time a droplet transfer is completed, n is decreased by 1. When n is 0, it is determined that one weld seam has been completed.

[0023] Step Four: Wire feeding control.

[0024] In the GTAW welding process of closed-loop pulsed large-gap welds based on vision-arc sensing, if the wire feeding speed is too fast, it will cause false welding. If the wire feeding speed is too slow, it will cause the weld seam to be insufficient. To solve this problem, the present invention discloses a wire feeding method for closed-loop pulsed GTAW large-gap welds based on wire sensing. During the droplet transfer process, when the wire arc voltage is close to 0V, it is judged that the droplet is transferring in the form of a liquid bridge, and the wire feeding speed remains unchanged. When the wire arc voltage is higher than 0V during the droplet transfer process, it is judged that the droplet is transferring in a free flight state, and the wire feeding speed is increased until the droplet transfers in the form of a liquid bridge. Before droplet transfer, the central control system obtains the molten pool area S through image processing 实 , when the monitored molten pool area S 实 >S 预 At this time, wire feeding starts.

[0025] Step Five: Calculation of the moving distance in the welding direction.

[0026] In the GTAW welding process of closed-loop pulsed large-gap welds based on vision-arc sensing, the present invention discloses a method for calculating the moving distance in the welding direction based on structured light vision sensing. Before welding starts, the central control system receives the image data transmitted by the structured light vision sensor and obtains the workpiece gap length M through image processing. After one weld seam is completed, the central control system obtains the weld seam width N through image processing. At this time, the central control system controls the V-shaped mounting plate to move a distance N in the positive X direction and a distance M in the negative Y axis direction so that the V-shaped mounting plate moves to the starting point of the next weld seam.

Claims

1. A closed-loop pulsed GTAW large-gap weld welding system based on vision-arc sensing, which is used for GTAW large-gap weld welding, is characterized in that: The closed-loop pulsed GTAW large-gap weld welding system based on visual-arc perception is composed of a GTAW robot, a vision system, a welding torch system, a wire feeder system, and a central control system; the GTAW robot is composed of an X-direction guide rail, a Y-direction guide rail, and a V-shaped mounting plate; the V-shaped mounting plate can move forward and backward along the X-direction guide rail and move left and right along the Y-direction guide rail; the V-shaped mounting plate includes a welding torch moving guide rail mounting position, a wire moving guide rail mounting position, and a vision system mounting position; the vision system is composed of a structured light vision sensor and a passive vision sensor, and is fixed at the vision system mounting position; the structured light vision sensor is composed of a CCD camera and a line laser; the welding torch system is composed of a welding torch rotary joint, a welding torch slide, and a welding torch; the welding torch rotary joint can rotate 360° and is fixedly connected to the welding torch; the welding torch slide is fixedly connected to the welding torch rotary joint and can move along the welding torch moving guide rail; the central control system controls the attitude of the welding torch by controlling the rotation of the welding torch rotary joint and the displacement of the welding torch slide; the wire feeder system is composed of a wire rotary joint, a wire slide, and a wire feeding tube; the wire rotary joint can rotate 360° and is fixedly connected to the wire feeding tube; the wire slide is fixedly connected to the wire rotary joint and can move along the wire moving guide rail; the central control system controls the attitude of the wire feeding tube by controlling the rotation of the wire rotary joint and the displacement of the wire slide; the central control system is composed of an industrial computer, a signal acquisition system, a communication bus, and a control bus; the central control system can collect arc signals, and the arc signals include the arc voltage signal at the wire end and the arc voltage signal at the tungsten electrode end, and can control the GTAW robot, the vision system, the welding torch system, and the wire feeder system; the arc voltage signal at the wire end is the arc voltage from the tip of the wire to the surface of the workpiece; the arc voltage signal at the tungsten electrode end is the arc voltage from the tip of the tungsten electrode to the surface of the workpiece.

2. The closed-loop pulsed GTAW large-gap weld welding system based on vision-arc perception according to claim 1, wherein: In the closed-loop pulsed GTAW large-gap weld welding system based on visual-arc perception, the pulse frequency is controlled by the closed-loop pulsed GTAW pulse frequency control method based on the collaborative perception of vision and arc; the closed-loop pulsed GTAW pulse frequency control method controls the pulse frequency by controlling the time T of the pulse period through the central control system; the pulse period time T is composed of the arc length adjustment time T1, the droplet transfer time T2, and the moving welding torch time T3; T = T1 + T2 + T3; the operation of one pulse period is: the central control system controls the GTAW robot to perform arc ignition operation and simultaneously starts to collect arc signals, performs closed-loop adjustment on the arc length through the arc signals and vision signals collected in real time, when the central control system monitors through the vision system that the base metal reaches the molten state, controls the wire feeder system to convey filler metal to the molten pool area with preset parameters, after the droplet transfer is completed, breaks the arc, and the central control system controls the welding torch to move to the next arc ignition point.

3. The closed-loop pulsed GTAW large-gap weld welding system based on vision-arc sensing according to claim 1, characterized in that: In the closed-loop pulsed GTAW large-gap weld welding system based on vision-arc sensing, the arc length is controlled by the pulsed GTAW arc length control method based on the collaborative sensing of arc and vision. The pulsed GTAW arc length control method based on the collaborative sensing of arc and vision controls the torch system through the central control system to change the position of the torch to achieve arc length control. After welding starts, in a pulse cycle, the central control system first controls the torch to perform the arc-starting operation. After successful arc starting, the central control system raises the torch height to H according to the tungsten electrode arc voltage signal collected in real time. After each droplet transfer is completed, the central control system controls the torch to move to the right by a weld bead thickness D. After all droplet transfers are completed, the central control system controls the torch to extinguish the arc. Subsequently, according to the data collected by the structured light vision sensor, the torch is moved downward by a distance H and at the same time the torch reaches the starting point of the next pulse cycle. There is a relationship of L = F(U) between the tungsten electrode arc voltage and the arc length, where L is the arc length and U is the tungsten electrode arc voltage. The central control system realizes the lifting of the torch by controlling the torch slide in the torch system to move on the torch movement guide rail, and realizes the left and right displacement of the torch by controlling the V-shaped mounting plate in the GTAW robot to move on the Y-direction guide rail. After arc extinguishing, the line laser projects a laser parallel to the welding direction and passing through the center of the weld bead, and the CCD camera captures the image and transmits it to the central control system. The central control system obtains the weld bead thickness D after processing.

4. The closed-loop pulsed GTAW large-gap weld welding system based on vision-arc perception according to claim 1, wherein: In the closed-loop pulsed GTAW large-gap weld welding system based on vision-arc sensing, the number of unidirectional weld beads in the weld is calculated by the calculation method of the number of unidirectional weld beads in the closed-loop pulsed GTAW large-gap weld based on structured light vision sensing. The calculation method of the number of unidirectional weld beads in the closed-loop pulsed GTAW large-gap weld based on structured light vision sensing processes the vision signal through the central control system to calculate the number of unidirectional weld beads in the large-gap weld. After welding starts, the line laser projects a laser parallel to the welding direction and passing through the starting point of the weld. The CCD camera receives the distorted light stripe and transmits the image information to the central control system. After the central control system corrects the distortion, it extracts the center line of the laser line and obtains the workpiece gap length M through image processing. After completing the first solder joint, the central control system processes the obtained thickness D of the solder joint and calculates the number of solder joints n; the number of solder joints is obtained by obtained; during the subsequent welding process, n is decreased by 1 for each droplet transfer completed; when n is 0, it is determined that a weld seam is completed.

5. The closed-loop pulsed GTAW large-gap weld welding system based on vision-arc perception according to claim 1, characterized in that: In the closed-loop pulsed GTAW large-gap weld welding system based on vision-arc sensing, the wire feeding length is controlled by the wire feeding method for closed-loop pulsed GTAW large-gap weld welding based on wire sensing; the wire feeding method for closed-loop pulsed GTAW large-gap weld welding based on wire sensing controls the wire feeding system through the central control system to change the wire feeding speed to achieve continuous liquid bridge transition; the droplet transfer state is judged by the arc voltage signal at the wire end; during the droplet transfer process, when the arc voltage of the wire is close to 0V, it is judged that the droplet is transferring in the liquid bridge transition mode, and the wire feeding speed remains unchanged; when the arc voltage of the wire is higher than 0V during the droplet transfer process, it is judged that the droplet is transferring in the free flight state, and the wire feeding speed is increased until the droplet transfers in the liquid bridge transition mode; before starting wire feeding, the industrial camera takes a real-time molten pool image and transmits it to the central control system, and the central control system obtains the real-time molten pool area S after processing 实 , when S 实 is greater than the preset molten pool area S 预 , wire feeding starts; before welding starts, the wire feeding length I for one pulse period is preset according to the material and diameter of the wire, and the central control system monitors the wire feeding length in real time. When the wire feeding length reaches I, the wire feeding stops.

6. The closed-loop pulsed GTAW large-gap weld welding system based on vision-arc sensing according to claim 1, wherein: In the closed-loop pulsed GTAW large-gap weld welding system based on vision-arc sensing, the moving distance in the welding direction is calculated by the moving distance calculation method in the welding direction based on structured light vision sensing; the moving amount is the longitudinal moving amount in the positive X-axis direction and the transverse moving amount in the negative Y-axis direction; the longitudinal moving amount is the width of the previous weld; the weld width is obtained after the central control system processes the image information transmitted by the structured light vision sensor; the line laser projects a laser perpendicular to the welding direction, and the structured light vision sensor receives the distorted light strip and transmits the image information to the central control system; after the central control system corrects the distortion, it extracts the center line of the laser line, and obtains the weld width N through image processing; the transverse moving amount is the workpiece gap length M; before welding starts, the workpiece gap M is detected, and the workpiece gap M is obtained after the central control system processes the image information transmitted by the structured light vision sensor; The line laser projects a laser parallel to the welding direction, and the structured light vision sensor receives the distorted light strip and transmits the image information to the central control system; after the central control system corrects the distortion, it extracts the center line of the laser line, and obtains the workpiece gap M by establishing a conversion model from the image coordinate system to the camera coordinate system; after the central control system calculates the moving distance, it moves the welding torch to the starting point of the next weld.

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