System for feeding back STT root welding penetration degree in real time

Abstract

The invention discloses a system for feeding back STT root welding penetration degree in real time. The system for feeding back the STT root welding penetration degree in real time is composed of a welding power source, a movement mechanism, a welding gun, a current sensor, a voltage sensor, a data acquisition card and an industrial personal computer. The welding gun is located at the clamping end of the movement mechanism, and the current sensor is installed on a welding loop to measure welding current according to the Hall effect principle and communicates with the industrial personal computer through the data acquisition card. The voltage sensors are installed at the two ends of a welding arc to measure loop voltage and communicate with the industrial personal computer through the data acquisition card, and welding electrical parameters of the welding power source are controlled by output signals of the industrial personal computer. The industrial personal computer collects current and voltage of a welding loop and controls electrical parameters of a welding power source through the predictive control software system and the data collection card. According to the system for feeding back the penetration degree of STT root welding in real time, the penetration degree is controlled by adjusting welding parameters in real time.

Description

Technical Field

[0001] This invention belongs to the field of welding, and in particular relates to a system for real-time feedback of the STT root weld penetration degree. Background Technology

[0002] Pipe root welding is the area in pipe welding that bears the greatest pressure and corrosion, and its penetration directly determines the service life of the welded joint. Therefore, controlling the penetration of pipe root welds is a research hotspot in the welding field. STT (Solving Technique Tolerance) technology is widely used in pipe root welding due to its low heat input and low spatter, but it is mostly used in manual operations and requires welder adjustments. Currently, there is no STT welding penetration control method for automated welding mechanisms.

[0003] Extensive research has been conducted on the penetration process in welding, employing methods primarily including visual sensing, acoustic signal sensing, and arc sensing. Due to its short-circuit transfer nature, STT welding exhibits poorer weld pool stability compared to conventional tungsten inert gas (TIG) welding, often rendering visual and acoustic signals ineffective in extracting valuable features. Sensing welding electrical parameters (welding current and arc voltage) during the welding process is crucial because they not only do not affect accessibility but also directly determine the welding heat input and arc force, thus influencing weld formation. Hall effect sensors can acquire these signals, and after filtering, they can be used to establish a model relating welding electrical signals to the penetration state. Studies have shown that welding heat input serves as a significant indicator of weld penetration; surface fluctuations in the weld pool during welding also reflect the state of weld penetration.

[0004] Therefore, there is an urgent need to design a system that provides real-time feedback on the STT root weld penetration level to solve the problems mentioned above. Summary of the Invention

[0005] To address the technical problem mentioned in the background art that the STT welding process, being a short-circuit transfer process, has poorer molten pool stability compared to conventional tungsten inert gas welding, and that visual and acoustic signals often fail to extract effective features, a system is provided to provide real-time feedback on the STT root weld penetration level, thus solving the problem of real-time feedback on the STT root weld penetration level.

[0006] To achieve the above objectives, the specific technical solution of the system for real-time feedback of STT root weld penetration degree of the present invention is as follows: A system for real-time feedback of STT root weld penetration degree consists of a welding power source, a motion mechanism, a welding torch, a current sensor, a voltage sensor, a data acquisition card, and an industrial control computer; The welding torch is located at the clamping end of the motion mechanism; The current sensor, based on the Hall effect principle, is installed in the welding circuit to measure the welding current and communicates with the industrial control computer through a data acquisition card; Voltage sensors are installed at both ends of the welding arc to measure the circuit voltage and communicate with the industrial control computer via a data acquisition card; The welding electrical parameters of the welding power source are controlled by the output signals of the industrial control computer; The industrial control computer uses predictive control software and data acquisition cards to collect the current and voltage of the welding circuit and control the electrical parameters of the welding power supply.

[0007] Furthermore, the welding power source is equipped with an STT welding mode, enabling digital control of welding electrical parameters and wire feed speed.

[0008] Furthermore, the current sensor is manufactured using the Hall magnetic compensation principle and is used to measure 300A~500A DC, AC and pulse currents, and truly follows the linear changes of the input current.

[0009] Furthermore, the voltage sensor is manufactured using the Hall magnetic compensation principle and is used to measure DC, AC, and pulse voltages from 10V to 600V (10mA), and it truly follows the linear changes of the input voltage.

[0010] Furthermore, the data acquisition card provides 16 analog input channels, supporting simultaneous sampling; it also provides 2 analog output channels, which can be used for signal generation or control applications.

[0011] Furthermore, industrial control computers support multi-core parallel computing to quickly process complex tasks.

[0012] Furthermore, the industrial PC motherboard provides multiple network cable interfaces for communication with industrial equipment; it also has multiple optional PCI-E expansion slots to support the installation of additional industrial acquisition cards.

[0013] Furthermore, an adaptive predictive controller was established, which characterizes weld penetration using the average welding heat input (J) and the voltage fluctuation (K) during the peak period under the action of normalized arc force. It adopts a rolling optimization mechanism and achieves feedback correction by identifying the parameters of the system model online to control the degree of STT flat weld penetration.

[0014] Furthermore, the welding torch is clamped on the motion mechanism, enabling precise control of the welding trajectory and welding speed.

[0015] The system of the present invention for real-time feedback of STT root weld penetration has the following advantages: By adjusting welding parameters in real time, an automated welding penetration control system is achieved. Current and voltage sensors are installed on the STT root welding system, and the collected current and voltage are transmitted to the industrial control computer via a data acquisition card. The software of the industrial control computer calculates and outputs control signals to adjust the welding electrical parameters, thereby controlling the degree of penetration. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the system for real-time feedback of STT root weld penetration degree according to the present invention; Figure 2 This is a system software model diagram of the present invention for real-time feedback of STT root weld penetration degree; Figure 3 This is a system control flowchart for real-time feedback of STT root weld penetration degree according to the present invention; Figure 4 This is a waveform diagram of the STT root weld voltage in the system that provides real-time feedback on the STT root weld penetration level according to the present invention. Figure 5 This is a diagram showing the back width distribution of the weld seam in the open-loop test of the STT root weld penetration system, which provides real-time feedback on the penetration level of the STT weld according to the present invention. Figure 6 This is a diagram showing the width distribution of the back side of the weld in the closed-loop test system for real-time feedback of STT root weld penetration in this invention. Figure 7 This is a distribution diagram of J, K, and Ib values ​​during the welding process of the closed-loop test system for real-time feedback of STT root weld penetration degree according to the present invention; Figure 8 This is a diagram showing the width distribution of the weld back side in a closed-loop test system for real-time feedback of STT root weld penetration in this invention.

[0017] Explanation of markings in the diagram: 1. Welding power source; 2. Motion mechanism; 3. Welding torch; 4. Current sensor; 5. Voltage sensor; 6. Data acquisition card; 7. Industrial computer; 8. Pipeline. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of the invention and form different embodiments. For example, in the claims, any of the claimed embodiments can be used in any combination.

[0020] The following is a reference to the appendix. Figure 1 To be continued Figure 8 The present invention describes a system for real-time feedback of STT root weld penetration.

[0021] like Figure 1 As shown, the real-time feedback system for STT root weld penetration in this invention consists of a welding power source 1, a motion mechanism 2, a welding torch 3, a current sensor 4, a voltage sensor 5, a data acquisition card 6, and an industrial control computer 7. The welding torch 3 is located at the clamping end of the motion mechanism 2. The current sensor 4, based on the Hall effect principle, is installed in the welding circuit to measure the welding current and communicates with the industrial control computer 7 through the data acquisition card 6. The voltage sensor 5 is installed at both ends of the welding arc to measure the circuit voltage and communicates with the industrial control computer 7 through the data acquisition card 6. The welding electrical parameters of the welding power source 1 are controlled by the output signal of the industrial control computer 7. The industrial control computer 7, through the predictive control software system and the data acquisition card 6, realizes the acquisition of the current and voltage of the welding circuit and the control of the electrical parameters of the welding power source 1.

[0022] Furthermore, such as Figure 1 As shown, welding power supply 1 is equipped with STT welding mode, realizing digital control of welding electrical parameters and wire feed speed; current sensor 4 is model CHB-500SG of Yubo module, which is manufactured with Hall magnetic compensation principle, and is used to measure 300A~500A DC, AC and pulse current, and truly follows the linear change of input current; voltage sensor 5 is model CHV-25P / 50 of Yubo module, which is manufactured with Hall magnetic compensation principle, and is used to measure 10V~600V (10mA) DC, AC and pulse voltage, and truly follows the linear change of input voltage.

[0023] Preferably, the device for real-time feedback control of STT root weld penetration includes a hardware system and a software system. The hardware system includes: a welding power source 1, which is a Lincoln STT-II welding power source 1; a Kumagai A-305 motion mechanism 2, which clamps the welding torch 3 to achieve the movement of the welding torch; welding sensing devices, which include a current sensor 4 and a voltage sensor 5; and the collected current and voltage, which are transmitted to an industrial control computer 7 via a data acquisition card 6. The software part of the industrial control computer 7 calculates and outputs control signals to adjust the parameters of the welding power source 1 to control the penetration degree.

[0024] The main component of the software system is an adaptive predictive controller. The control algorithm is written in MATLAB, and the controller is modeled using MATLAB's Simulink simulation tool. The constructed adaptive predictive controller uses two characteristic parameters: average welding heat input (J) and voltage fluctuation during the peak period under normalized arc force (K) for calculating the penetration control model.

[0025] The average welding heat input can be calculated from the collected electrical signal data and welding speed: Where U is the welding voltage, I is the welding current, v is the welding speed, Fs is the short-circuit transition frequency within one welding torch 3 oscillation cycle (within 1 second), and J is the average heat input within one welding torch 3 oscillation cycle during the welding process.

[0026] The calculation method for voltage fluctuation (K) during the peak period under normalized arc force is as follows: The voltage waveform ΔU during the peak period is obtained from the difference between the maximum and minimum voltage values ​​in the peak interval. Multiple calculations are performed and the average value is taken to reduce error. The characteristic parameter K is defined as follows: In the formula, n is the number of welding cycles within 1 second, IP is the real-time peak current, and β is the coefficient for balancing the data volume.

[0027] The predictive control employed has three distinct characteristics: model prediction, rolling optimization, and feedback correction. The predictive model's role is to predict the dynamic changes of the system output or state in the future based on historical information and assumed control variables for future moments.

[0028] Before calculating the control input in each control cycle, the model parameters are identified in real time based on the system's input and output information. In predictive control, the control input is calculated by minimizing a performance index function. This function measures the system's dynamic behavior in the future and offers design flexibility, such as minimizing tracking error, minimizing control energy, or combining multiple control objectives.

[0029] In predictive control, optimization is performed in a rolling manner. The calculated multi-step control variables are not implemented all at once, but only one step is implemented. At the next sampling time, the optimization range moves forward one step, and the optimization calculation and one-step control are repeated.

[0030] At each sampling time point, before solving the optimization problem, actual system information is collected to correct the model's predictions. Based on the concept of adaptive control, real-time system input-output information is used to update the prediction model and control law through system identification. Feedback correction makes the optimization basis closer to the actual system dynamics, thus achieving rolling optimization closed loop.

[0031] Furthermore, such as Figure 1 As shown, the preferred data acquisition card 6 is the NI PCI-6221, a high-performance data acquisition card suitable for various applications such as laboratory automation, research, and manufacturing. It provides 16 analog input channels, supports simultaneous sampling, and is suitable for applications requiring multiple sensors or signal sources. The data acquisition card 6 also provides 2 analog output channels, which can be used for signal generation or control applications. It supports both digital input and output.

[0032] The Industrial PC 7 is equipped with the latest generation high-performance Intel Core i9-13900K processor, supporting multi-core parallel computing for rapid processing of complex tasks. It also features 64GB of high-capacity memory to ensure real-time data processing and accuracy. The Industrial PC 7 motherboard provides multiple network cable interfaces for communication with industrial equipment and offers multiple optional PCI-E expansion slots to support the installation of additional industrial data acquisition cards.

[0033] Furthermore, such as Figure 1 As shown, a predictive control software system was also established. The characteristic parameters of average welding heat input (J) and voltage fluctuation during the peak period under the action of normalized arc force (K) were used to calculate the penetration control model. An adaptive predictive controller was established, which adopted a rolling optimization mechanism and realized feedback correction by identifying the parameters of the system model online to control the penetration degree of STT flat welding. The welding torch 3 is clamped on the motion mechanism 2 to realize precise control of welding trajectory and welding speed.

[0034] As a preferred embodiment, the base material is selected as API 5L X65 steel catenary riser with a diameter of 355 mm and a wall thickness of 13.5 mm. The bevel is a 9° U-shaped bevel. The welding wire is ER70S-6 welding wire, and the shielding gas is a mixture of 82% argon and 18% carbon dioxide.

[0035] Appendix 1 shows the main components of API 5L X65 and ER70S-6 welding wires. The welding torch 3 was positioned at the 12 o'clock position on the pipe. The pipe 8 was rotated to a flat welding position. The wire feed speed was set to 4.28 m / min, the welding speed to 0.3 m / min, and the peak current (Ip) was fixed at 350 A. Five sets of control tests with different base currents (Ib) were set (Tests 1-5), and one set of open-loop control tests (Test 6), as shown in Appendix 2. In the five sets of tests, the welding parameters were set before welding. The controller automatically identified the parameters of the system model and adjusted the output values ​​during the welding process to achieve controlled forming. In all five sets of tests, good penetration was achieved. After welding, the width of the weld back side was measured to calculate the deviation range of the welding effect. Appendix 1 Main chemical composition (wt.%) of API 5L X65 steel catenary riser and deposited metal Appendix 2 Welding Parameter Settings In the STT pipe root pass welding under the above conditions, the relationship between characteristic parameters and back width was previously analyzed through orthogonal experiments, resulting in a model of the weld back geometry. This model was used to derive initial reference values ​​for the average welding heat input (J) and the voltage fluctuation (K) during the peak period under normalized arc force: First, an open-loop test was conducted as a control, maintaining Ib = 75A throughout the welding process. Due to the increased effect of gravity, the weld bead size also increased relatively. The width of the weld on the back side fluctuated significantly, ranging from 4.1 to 4.8 mm, with a range of 0.7. Because the open-loop test lacked a feedback mechanism to adjust the base current Ib based on the weld bead size, the overall weld bead size on the back side was uneven, resulting in significant fluctuations in the measured Wb value. The open-loop test results demonstrate that closed-loop control is necessary to achieve uniform weld bead size on the back side.

[0036] A closed-loop control test was then conducted to verify the performance of the control system. The base current Ib was adjusted online by the controller, while all other welding parameters remained constant during the welding process. The desired operating point of the controller was set to Wb* = 4.4 mm. Under this condition, the desired operating points of the characteristic parameters were J* = 350 J / mm and K* = 4.1. The back side formed well using the controller, with a back side width of 4.2-4.5 mm and a range of 0.3. This indicates that the constructed device is suitable for controlling the forming process.

[0037] Appendix Figure 7 The image shows the J, K, and Ib values ​​collected during the welding process. The adaptive predictive control system can effectively control the system outputs J and K around their respective set values, thereby achieving the desired weld back width.

[0038] Appendix Figure 8 As shown, the initial base current values ​​for the weld back side width in the five sets of controlled tests, from bottom to top, were 65A, 70A, 75A, 80A, and 85A, respectively. It can be seen that the weld front width gradually increases with the increase of the initial base current. During the welding process, the system adjusted the welding parameters in real time. At the rear end of the weld, the back side width in all five sets of tests approached the desired value Wb*=4.4mm. Based on a system that provides real-time feedback on the penetration degree of STT root welds, this invention employs the pipe root weld system proposed in this application during STT pipe root welds, which can monitor and control the generation of weld penetration and the width of the back side in real time.

[0039] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A system for real-time feedback of STT root weld penetration, characterized in that, It consists of a welding power source, a motion mechanism, a welding torch, a current sensor, a voltage sensor, a data acquisition card, and an industrial control computer; The welding torch is located at the clamping end of the motion mechanism; The current sensor, based on the Hall effect principle, is installed in the welding circuit to measure the welding current and communicates with the industrial control computer through a data acquisition card; Voltage sensors are installed at both ends of the welding arc to measure the circuit voltage and communicate with the industrial control computer via a data acquisition card; The welding electrical parameters of the welding power source are controlled by the output signals of the industrial control computer; The industrial control computer uses predictive control software and data acquisition cards to collect the current and voltage of the welding circuit and control the electrical parameters of the welding power supply.

2. The system for real-time feedback of STT root weld penetration degree according to claim 1, characterized in that, The welding power source has an STT welding mode, which enables digital control of welding electrical parameters and wire feed speed.

3. The system for real-time feedback of STT root weld penetration degree according to claim 1, characterized in that, The current sensor is manufactured using the Hall magnetic compensation principle and is used to measure DC, AC and pulse currents of 300A~500A, and truly follows the linear change of the input current.

4. The system for real-time feedback of STT root weld penetration degree according to claim 1, characterized in that, The voltage sensor is manufactured using the Hall magnetic compensation principle and is used to measure DC, AC, and pulse voltages from 10V to 600V (10mA), and it truly follows the linear changes of the input voltage.

5. The system for real-time feedback of STT root weld penetration degree according to claim 1, characterized in that, The data acquisition card provides 16 analog input channels, supporting simultaneous sampling; it also provides 2 analog output channels, which can be used for signal generation or control applications.

6. The system for real-time feedback of STT root weld penetration degree according to claim 1, characterized in that, Industrial PCs support multi-core parallel computing to quickly process complex tasks.

7. The system for real-time feedback of STT root weld penetration degree according to claim 1, characterized in that, The industrial PC motherboard provides multiple network cable interfaces for communication with industrial equipment; it also has multiple optional PCI-E expansion slots to support the installation of additional industrial data acquisition cards.

8. The system for real-time feedback of STT root weld penetration degree according to claim 1, characterized in that, An adaptive predictive controller was also established, which characterizes the weld penetration by the average welding heat input (J) and the voltage fluctuation (K) during the peak period under the action of normalized arc force. It adopts a rolling optimization mechanism and realizes feedback correction by identifying the parameters of the system model online to control the penetration degree of STT flat welding.

9. The system for real-time feedback of STT root weld penetration degree according to claim 1, characterized in that, The welding torch is clamped in the motion mechanism, enabling precise control of the welding trajectory and welding speed.

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