Combined chemical storage tank outer wall welding device and method

Abstract

The present application relates to the field of advanced metal materials and surface engineering, in particular to a combined chemical storage tank outer wall welding device and method; it contains a mobile chassis, air pressure sensing, mechanical filtering and conversion, air source and damping, and driving and control module; the device forms local air resistance between left and right air blowing probes and the gap of the bevel edge, uses pressure difference to drive the deformation of the elastic diaphragm, converts the voltage signal into an electric signal by a linear variable differential transformer to control the motor to drive the welding gun to correct the deviation horizontally; the core is to replace the traditional detection with a double-channel air pressure difference sensing, and a capillary damping tube is connected in series in the air path to filter out the transient high-frequency air pressure burrs caused by welding spatter; the present application overcomes the influence of visual and contact type detection on strong arc light, smoke and probe wear and jam, and uses common mode rejection mechanism to eliminate environmental wind disturbance, ensuring the stability and authenticity of deviation detection under complex working conditions.

Description

Technical Field

[0001] This invention relates to the field of advanced metal materials and surface engineering, specifically to a combined welding device and method for the outer wall of a chemical storage tank. Background Technology

[0002] In the current working conditions of chemical storage tank manufacturing and construction, external wall welding usually involves the butt joint of large-sized and large-radius curved steel plates, requiring auxiliary guiding and tracking devices to drive the welding torch to continuously move along the centerline of the tank wall bevel. To achieve automatic bevel tracking, existing solutions generally adopt visual tracking, arc tracking, or contact mechanical detection architecture. That is, by acquiring images of the molten pool through an optical camera, extracting changes in current parameters using an arc sensor, or by relying on a mechanical probe to directly touch the edge of the bevel to calculate the deviation compensation amount and drive the slide table to correct the deviation. Although the above solutions have a certain tracking capability under normal stable working conditions, visual tracking is highly dependent on the optical path environment and is easily affected by strong arc light, reflection, and high-temperature dust. Arc tracking is easily affected by arc parameter fluctuations and working condition disturbances. Contact mechanical probes are prone to end face wear, thermal deformation, and mechanical jamming in the high-temperature spatter area, resulting in large deviation detection errors, frequent signal drift, and slow correction response, making it difficult to support high-precision continuous trajectory tracking under the complex curved surface conditions of the tank's external wall.

[0003] Therefore, improving the anti-interference capability and accuracy of bevel offset detection and correction control during the welding process of the outer wall of storage tanks has become an urgent technical problem to be solved. Summary of the Invention

[0004] The present invention specifically provides the following technical solution: A combined chemical storage tank outer wall welding device, comprising: A mobile chassis and a support frame, wherein the support frame is connected to a cross slide table and a welding torch is mounted on the cross slide table, and the system further includes: The air pressure sensing module includes a left air probe and a right air probe, which are symmetrically mounted on both sides of the front end of the welding torch, with their end faces facing the two edges of the bevel to be welded respectively. The mechanical filtering and conversion module is fixed to a mobile chassis and includes a diaphragm cavity, an elastic diaphragm, and a linear variable differential transformer. The elastic diaphragm is clamped and fixed in the diaphragm cavity by its edge, dividing it into a positive pressure chamber and a negative pressure chamber. Its center is connected to a central push rod, which is connected to the core of the linear variable differential transformer. Air source and damping module, including connected pressure regulating valve and air distribution manifold; The outlet of the manifold is connected to the left and right air blowing probes respectively. The two probes are connected to the positive pressure chamber and the negative pressure chamber respectively. Each connection path is connected in series with a capillary damping tube. Drive and control module, including industrial controller, servo motor and lead screw; The industrial controller is electrically connected to the linear variable differential transformer and the servo motor respectively. The servo motor is driven by the lead screw and drives the cross slide to move the welding torch laterally.

[0005] As a further embodiment of the present invention, both the left and right air-blowing probes are fixed to the welding torch by stainless steel connecting rods, and the left and right air-blowing probes are respectively connected to the positive pressure chamber and the negative pressure chamber by high-temperature resistant Teflon pressure-sensing tubes.

[0006] As a further embodiment of the present invention, the capillary damping tube is connected in series with the high-temperature resistant Teflon pressure-sensing tube between the left air-blowing probe and the positive pressure chamber, and the high-temperature resistant Teflon pressure-sensing tube between the right air-blowing probe and the negative pressure chamber. The inner diameter of the capillary damping tube is 0.5 mm, and the length of the capillary damping tube is 50 mm.

[0007] As a further embodiment of the present invention, the mobile chassis is attached to the outer wall of the chemical storage tank by magnetic suction wheels, the support frame is fixedly connected to the upper surface of the mobile chassis by bolts, the top of the support frame is slidably connected to the base of the cross slide table by guide rails, and the moving platform of the cross slide table is fixedly connected to the welding torch by flanges.

[0008] As a further embodiment of the present invention, the servo motor drives the lead screw through a plum blossom-shaped elastic coupling, and the lead screw is threadedly engaged with the nut seat at the bottom of the moving platform of the cross slide; the diaphragm cavity is fixed to the rear of the moving chassis by bolts, and the coil frame of the linear variable differential transformer is fixed to the outer shell of the diaphragm cavity by a mounting bracket.

[0009] As a further aspect of the present invention, the industrial controller has built-in deviation conversion logic and pre-stores a center reference voltage, a dead zone voltage threshold, and a displacement conversion coefficient. The deviation conversion logic includes: obtaining the lateral physical deviation based on the currently acquired voltage, the center reference voltage, the dead zone voltage threshold, and the displacement conversion coefficient; and outputting a zero speed command when the deviation between the currently acquired voltage and the center reference voltage does not reach the dead zone voltage threshold.

[0010] As a further aspect of the present invention, the industrial controller has built-in correction control logic, wherein the correction control logic includes: obtaining a target correction speed based on the lateral physical deviation; the industrial controller determines the lateral movement direction according to the positive or negative sign of the lateral physical deviation, determining to move to the right when the lateral physical deviation is greater than zero, determining to move to the left when the lateral physical deviation is less than zero, and remaining stationary when the lateral physical deviation is equal to zero.

[0011] A method for welding the outer wall of a modular chemical storage tank, comprising the following steps: S1, Reference Calibration Stage: The mobile chassis is attached to the outer wall of the chemical storage tank, the support frame is adjusted so that the welding torch is aligned with the center line of the bevel to be welded, the pressure stabilizing valve is started to continuously supply gas, and the voltage signal output by the linear variable differential transformer at this time is recorded as the center reference voltage. S2, Air Pressure Sensing and Mechanical Filtering Stage: During the welding process, the airflow forms a local air resistance in the gap between the left air probe, the right air probe and the edge of the groove to be welded. When the welding torch deviates from the center line of the groove to be welded, a pressure difference is formed in the connecting path. The differential pressure signal drives the elastic diaphragm to deform and drives the central push rod to move. The linear variable differential transformer outputs the corresponding voltage signal. S3, Deviation Conversion Stage: The industrial controller obtains the lateral physical deviation based on the sampled voltage signal and the central reference voltage; S4. Correction control stage: The industrial controller determines the target correction speed and the lateral movement direction based on the lateral physical deviation. S5. Execution Output Stage: The industrial controller converts the target correction speed into control pulses and sends them to the servo motor. The servo motor drives the lead screw to move the welding torch toward the center line of the groove to be welded.

[0012] As a further aspect of the present invention, in the deviation conversion stage, when the deviation between the voltage signal and the center reference voltage is less than a preset dead zone voltage threshold, the industrial controller outputs a zero speed command and the servo motor remains stationary; when the deviation between the voltage signal and the center reference voltage is greater than or equal to the dead zone voltage threshold, the industrial controller outputs a non-zero speed command.

[0013] As a further aspect of the present invention, during the execution output phase, the industrial controller continuously compares the difference between the voltage signal and the center reference voltage. When the deviation between the voltage signal and the center reference voltage is less than a preset dead-zone voltage threshold, the industrial controller stops outputting control pulses; when the deviation between the voltage signal and the center reference voltage is greater than or equal to the dead-zone voltage threshold, the industrial controller continues to output control pulses.

[0014] As can be seen from the above solutions, the advantages of the present invention are: 1. This invention transforms the acquisition of weld offset into a linkage between air pressure difference and diaphragm displacement through an air pressure sensing module and a mechanical filtering and conversion module. By utilizing the symmetrically arranged left and right air blowing probes to create air resistance differences on both sides of the weld bevel, the elastic diaphragm is driven to deform and, through the central push rod, the core displacement of the linear variable differential transformer is driven to output a voltage signal. This design effectively solves the problems of conventional visual tracking being easily affected by arc light and dust, arc tracking being easily affected by working condition fluctuations, and mechanical probes being easily worn, significantly improving the anti-interference capability of bevel offset detection. 2. This invention utilizes the flow resistance characteristics of a capillary damping tube connected in series in the connection path between the air source and the damping module to physically weaken transient high-frequency air pressure disturbances caused by welding spatter or environmental wind disturbances. Combined with the drive and control module, the industrial controller processes the voltage signal and calculates the deviation, thereby driving the servo motor and lead screw to precisely adjust the position of the welding torch using a cross slide. This structure effectively filters out high-frequency interference signals, avoids frequent invalid fine-tuning caused by false offsets, and significantly improves the accuracy of trajectory tracking and automatic correction during the welding process on the outer wall of the storage tank. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort: Figure 1 This is a schematic diagram of the overall external structure of the device; Figure 2 This is a structural diagram of the base; Figure 3 This is a schematic diagram of the structure of a linear variable differential transformer; Figure 4 This is a schematic diagram of the capillary damping tube. Figure 5 A flowchart illustrating the method of an embodiment of the present invention is shown.

[0016] In the diagram: 1. Mobile chassis; 2. Magnetic rollers; 3. Support frame; 4. Guide rail; 5. Cross slide; 6. Base; 7. Mobile platform; 8. Flange; 9. Nut seat; 10. Welding torch; 11. Bevel to be welded; 12. Air pressure sensing module; 13. Left air probe; 14. Right air probe; 15. Stainless steel connecting rod; 16. High-temperature resistant Teflon pressure tube; 17. Mechanical filtering and conversion module; 18. Diaphragm cavity; 19. Outer shell; 20. Elastic diaphragm; 21. Positive pressure chamber; 22. Negative pressure chamber; 23. Central push rod; 24. Linear variable differential transformer; 25. Iron core; 26. Coil frame; 27. Mounting bracket; 28. Air source and damping module; 29. ​​Pressure regulating valve; 30. Gas manifold; 31. Capillary damping tube; 32. Drive and control module; 33. Servo motor; 34. Plum blossom-shaped flexible coupling; 35. Lead screw. Detailed Implementation

[0017] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings, so that the above and other objects, features, and advantages of the present invention will become clearer. In all the drawings, the same reference numerals indicate the same parts. The drawings are not intentionally drawn to scale; the focus is on illustrating the main points of the invention.

[0018] Example 1: Combination Figure 1 As shown, a combined chemical storage tank outer wall welding device includes: The mobile chassis 1 and support frame 3 are connected to the cross slide 5, and a welding torch 10 is mounted on the cross slide 5. The system also includes: The air pressure sensing module 12 includes a left air blowing probe 13 and a right air blowing probe 14, which are symmetrically mounted on both sides of the front end of the welding torch 10, with their end faces facing the two sides of the bevel 11 to be welded. Mechanical filtering and conversion module 17, fixed to mobile chassis 1, includes diaphragm cavity 18, elastic diaphragm 20 and linear variable differential transformer 24; The edge of the elastic diaphragm 20 is clamped and fixed inside the diaphragm cavity 18, dividing it into a positive pressure chamber 21 and a negative pressure chamber 22. Its center is connected to a central push rod 23, which is connected to the core 25 of the linear variable differential transformer 24. The air source and damping module 28 includes a connected pressure regulating valve 29 and a gas distribution manifold 30; The outlet of the manifold 30 is connected to the left air probe 13 and the right air probe 14 respectively. The two probes are connected to the positive pressure chamber 21 and the negative pressure chamber 22 respectively. Each connection path is connected in series with the capillary damping tube 31. Drive and control module 32 includes an industrial controller, servo motor 33 and lead screw 35; The industrial controller is electrically connected to the linear variable differential transformer 24 and the servo motor 33 respectively. The servo motor 33 is connected to the lead screw 35 and drives the cross slide 5 to move the welding torch 10 laterally.

[0019] This device is used for bevel tracking during welding of the outer wall of chemical storage tanks. In response to the problems that conventional visual tracking is easily affected by strong arc light, reflection and dust, arc tracking is easily affected by working condition fluctuations, and mechanical probes are easily worn and stuck, the acquisition of weld offset is changed to the linkage transmission of air pressure difference and diaphragm displacement. The mobile chassis 1 is used to support the whole machine and is attached to the outer wall of the storage tank. The support frame 3 and the cross slide 5 form the basis for the installation and lateral adjustment of the welding torch 10. After the left air probe 13 and the right air probe 14 are symmetrically arranged, a comparable air resistance difference is formed between the probe end face and the two sides of the bevel. The elastic diaphragm 20 in the diaphragm cavity 18 converts this difference into the displacement of the central push rod 23. The linear variable differential transformer 24 converts the displacement into a voltage signal. The industrial controller drives the servo motor 33 and the lead screw 35 to drive the cross slide 5 to laterally correct the position of the welding torch 10. The capillary damping tube 31 physically weakens the transient air pressure disturbance caused by spatter, making the signal entering the controller closer to the actual offset of the welding torch 10 relative to the center line of the bevel, thereby reducing the dependence of the back-end algorithm on strong interference signals.

[0020] Both the left air probe 13 and the right air probe 14 are fixed to the welding torch 10 by stainless steel connecting rods 15. The left air probe 13 and the right air probe 14 are connected to the positive pressure chamber 21 and the negative pressure chamber 22 by high-temperature resistant Teflon pressure tubes 16, respectively.

[0021] After the left air probe 13 and the right air probe 14 are fixed by the stainless steel connecting rod 15, the spatial relative position of the probes on both sides can be kept stable, so that the change in the gap between the probe end face and the edge of the bevel is mainly caused by the lateral offset of the welding gun 10, rather than by the deformation of the probe support. The stainless steel connecting rod 15 is used to improve the structural stability of the area near the welding heat source, and the high-temperature resistant Teflon pressure tube 16 is used to reliably transmit the pressure signal from the probe end to the diaphragm cavity 18, avoiding signal attenuation caused by the softening, bending or local shrinkage of ordinary hoses after heating; this connection method enables the air pressure sensing module 12 and the welding torch 10 to move synchronously. When the welding torch 10 tracks the change in direction, the pressure sampling relationship of the probe relative to the two edges of the bevel remains consistent, which facilitates the output of a comparable differential pressure signal by the diaphragm cavity 18.

[0022] Combination Figure 4As shown, the capillary damping tube 31 is connected in series with the high-temperature resistant Teflon pressure tube 16 between the left air blowing probe 13 and the positive pressure chamber 21, and the high-temperature resistant Teflon pressure tube 16 between the right air blowing probe 14 and the negative pressure chamber 22. The inner diameter of the capillary damping tube 31 is 0.5 mm, and the length of the capillary damping tube 31 is 50 mm.

[0023] The capillary damping tube 31 is connected in series in the pressure path on both sides to weaken the pressure fluctuation received by the probe end as flow resistance. When the inner diameter of the capillary damping tube 31 is 0.5 mm and its length is 50 mm, the gas is difficult to fill or discharge the diaphragm cavity 18 in time under short-term pulse disturbance. The transient high-frequency pressure signal is suppressed, while the continuous differential pressure signal can still pass through. With this setting, transient spike interference signals caused by welding spatter, short-term wind disturbance and local airflow turbulence are not easily transmitted directly to the elastic diaphragm 20. The diaphragm displacement more concentratedly reflects the lateral deviation between the welding torch 10 and the bevel centerline, reducing the ineffective fine-tuning action of the servo motor 33.

[0024] Combination Figure 2 The mobile chassis 1 is attached to the outer wall of the chemical storage tank by magnetic wheels 2. The support frame 3 is fixedly connected to the upper surface of the mobile chassis 1 by bolts. The top of the support frame 3 is slidably connected to the base 6 of the cross slide table 5 by guide rail 4. The moving platform 7 of the cross slide table 5 is fixedly connected to the welding gun 10 by flange 8.

[0025] When the mobile chassis 1 is attached to the outer wall of the storage tank by the magnetic suction wheel 2, it can provide continuous adhesion to the curved steel plate, so that the device can remain attached during the welding process; the support frame 3 is fixed to the upper surface of the mobile chassis 1 by bolts, which facilitates the adjustment of the assembly position under different tank diameters or bevel postures. The guide rail 4 at the top of the support frame 3 slides with the base 6 of the cross slide table 5, which can limit the movement direction of the welding torch 10 during lateral correction and improve the repeatability of lateral displacement. After the moving platform 7 of the cross slide table 5 is fixed to the welding torch 10 through the flange 8, the posture change of the welding torch 10 can be directly transmitted by the slide table, reducing the accumulation of deviation caused by loose intermediate connection.

[0026] Combination Figure 3 The servo motor 33 drives the lead screw 35 through the plum blossom-shaped elastic coupling 34. The lead screw 35 is threadedly engaged with the nut seat 9 at the bottom of the moving platform 7 of the cross slide table 5. The diaphragm cavity 18 is fixed to the rear of the moving chassis 1 by bolts. The coil frame 26 of the linear variable differential transformer 24 is fixed to the outer shell 19 of the diaphragm cavity 18 by the mounting bracket 27.

[0027] When the servo motor 33 drives the lead screw 35 through the plum blossom-shaped flexible coupling 34, the coupling can absorb some of the axial installation error and minor vibration, reducing the impact of transmission shock on the cross slide table 5; after the lead screw 35 is threadedly engaged with the bottom nut seat 9 of the moving platform 7, the rotational motion output by the servo motor 33 is converted into lateral linear motion, which is used to drive the welding torch 10 to correct the bevel center; the diaphragm cavity 18 is fixed to the rear of the moving chassis 1 by bolts, which can reduce the direct interference of the heat input and spatter at the front end of the welding torch 10 to the diaphragm area; After the coil frame 26 of the linear variable differential transformer 24 is fixed by the mounting bracket 27, the displacement of the iron core 25 and the coil position remain stable, which makes it easy to convert the diaphragm displacement into voltage changes that can be read by the controller. During the correction process, due to the frequent forward and reverse fine adjustments of the servo motor 33, the elastic body of the plum blossom-shaped elastic coupling 34 will produce periodic torsional deformation and elastic hysteresis under the action of alternating torque. This will not only weaken the instantaneous response of the control pulse, but may also form a low-frequency resonance with the rotational inertia of the lead screw 35. To overcome the disruption of the ideal rigid transmission assumption caused by this dynamic interference, the rated torsional stiffness of the plum blossom-shaped flexible coupling 34 is set to be more than ten times the product of the rated torque of the servo motor 33 and the maximum angular acceleration of the lead screw 35 in the matching of the transmission system. This ensures that under dynamic high-frequency correction commands, the lateral displacement of the cross slide 5 corresponding to the maximum elastic deformation angle of the coupling is strictly limited within the allowable process error band, thereby guaranteeing the accurate and lag-free transmission of the servo system speed command to the mechanical displacement at the physical level. Specifically, the rated torsional stiffness of the plum blossom-shaped flexible coupling 34 must satisfy the geometric and physical matching constraint relationship shown in the following formula:

[0028] In the formula, The rated torsional stiffness of the plum blossom-shaped flexible coupling 34, in units of _____ ; The rated torque of servo motor 33, in units of ; The maximum angular acceleration of the lead screw 35° has dimensions of . ;10 is the empirical matching constant, with dimensions of ; The aforementioned rated torsional stiffness threshold is used for conservative margin control during assembly selection and factory verification. In practice, it can be verified through no-load reciprocating test, step speed response test, and displacement tracking test at the maximum correction frequency. During verification, the peak overshoot of the cross slide 5, steady-state tracking error, and recovery time after forward and reverse switching are used as judgment indicators, so that the transmission constraint relationship has measurable and verifiable realization conditions.

[0029] The industrial controller has built-in deviation conversion logic and pre-stores the center reference voltage, dead zone voltage threshold, and displacement conversion coefficient. The deviation conversion logic includes: obtaining the lateral physical deviation based on the currently acquired voltage, center reference voltage, dead zone voltage threshold, and displacement conversion coefficient; and outputting a zero speed command when the deviation between the currently acquired voltage and the center reference voltage does not reach the dead zone voltage threshold.

[0030] The industrial controller receives the voltage signal output by the linear variable differential transformer 24 during the sampling period and performs a moving average processing on the multiple sampled values ​​during the period to reduce residual electrical noise and short-term jitter; the voltage deviation is obtained by subtracting the filtered current voltage from the center reference voltage, and the deviation reflects the changing trend of the welding torch 10 relative to the bevel center. When the absolute value of the difference between the filtered current voltage and the center reference voltage is less than the preset dead zone voltage threshold, the controller outputs a zero speed command to avoid frequent adjustments caused by transmission gaps and small signal fluctuations; when the absolute value of the voltage deviation is greater than or equal to the dead zone voltage threshold, the controller converts it into a lateral physical deviation using a displacement conversion factor for subsequent correction control. This conversion logic transforms the diaphragm displacement signal into a control quantity, making it easy to directly correspond with the speed command of the servo motor 33. This deviation conversion logic essentially constitutes a signal conversion and physical quantity mapping model. Its purpose is to accurately map the abstract electromagnetic induction signal into the actual physical offset of the welding torch 10 relative to the bevel under strong interference environment. In terms of logic structure and data flow, the model receives the original voltage signal of the linear variable differential transformer 24, outputs the filtered current voltage through the moving average submodule, enters the difference calculation submodule to compare with the central reference voltage and output the voltage deviation, enters the dead zone judgment and conversion stage in the deviation conversion logic, and outputs the lateral physical deviation or zero speed command according to the threshold condition. In terms of the physical relationship represented, the model represents the complete mapping law from the small mechanical displacement generated by the air pressure difference driving the elastic diaphragm 20 to the induced voltage change caused by the displacement of the coil core 25, and then quantitatively calculates the spatial offset of the welding torch 10 in reverse. Since the dead zone voltage threshold judgment mechanism is introduced, the false offset caused by transmission gap and mechanical vibration is effectively isolated, ensuring that the output lateral physical deviation has a high degree of authenticity and stability. Among them, the dead zone voltage threshold is used to limit the upper limit of voltage fluctuation within the allowable tracking bandwidth. Its value is preset during the device factory calibration in combination with the no-load output fluctuation range of the linear variable differential transformer 24, the static zero-point drift of the diaphragm cavity 18, and the allowable swing accuracy of the welding torch 10 at the welding site, in order to distinguish between effective deviation signals and near-zero disturbance signals. The displacement conversion factor is used to characterize the correspondence between the voltage change and the displacement of the center push rod 23. It is determined by the sensitivity of the linear variable differential transformer 24, the effective pressure-bearing area of ​​the diaphragm, and the transmission ratio of the mechanism. During the calibration stage, it is corrected by the voltage output corresponding to the known lateral offset, so as to ensure that the voltage deviation can be stably converted into the lateral physical deviation. In the complex working conditions of the outer wall of the storage tank, the gravity component of the mobile chassis 1 under different spatial postures will have an asymmetric effect on the self-weight of the elastic diaphragm 20 and the central push rod 23, and the screw 35 nut pair has nonlinear friction and elastic deformation. The simple static linear conversion assumption will lead to physical mapping distortion. Therefore, in order to break the absolute linear assumption under ideal conditions, the displacement conversion coefficient is not a single constant, but a dynamic mapping rule based on the segmented calibration table. The specific data flow is as follows: The industrial controller pre-stores a two-dimensional calibration matrix containing different spatial attitude ranges and different differential pressure ranges; during the conversion, the controller obtains the current operating attitude parameters of the mobile chassis 1. The acquisition of the operating attitude parameters does not rely on additional hardware attitude sensors, but is directly read by the industrial controller from the task parameters issued by the host computer through external communication according to the type of welding process currently being executed, or preset by the operator through the human-machine interface before welding starts, thereby providing attitude dimension data input for the algorithm without adding additional attitude sensors to the hardware structure; according to the range where the voltage deviation is located, the corresponding displacement conversion coefficient is called from the two-dimensional calibration matrix for multiplication operation; This structured lookup table and segmented calculation rule effectively overcomes the disruption of the ideal mapping law by the gravitational component and mechanical nonlinear deformation, ensuring the authenticity of the lateral physical deviation in the dynamic environment. To enable direct programming implementation of this logic, the industrial controller can execute it in five consecutive steps: sampling, filtering, comparison, conversion, and output. First, read multiple voltage values ​​within a fixed sampling period and calculate the average. Then, calculate the difference with the central reference voltage. Based on the dead zone voltage threshold, perform branch judgment and output the corresponding zero speed command or deviation conversion result. This result serves as the sole input for subsequent correction control, thus maintaining a unidirectional closed loop in data source, processing, and output format, facilitating on-site debugging and online verification.

[0031] The industrial controller has built-in correction control logic, which includes: obtaining the target correction speed based on the lateral physical deviation; the industrial controller determines the lateral movement direction according to the positive or negative sign of the lateral physical deviation, determining to move to the right when the lateral physical deviation is greater than zero, determining to move to the left when the lateral physical deviation is less than zero, and remaining stationary when the lateral physical deviation is equal to zero.

[0032] After obtaining the lateral physical deviation, the industrial controller forms a basic correction speed according to the proportional coefficient, so that the welding gun 10 can make a corresponding speed response to the deviation change. After accumulating the lateral physical deviation within the historical sampling period and multiplying it by the integral coefficient, a compensation correction speed can be formed to eliminate long-term small deviations. It is particularly suitable for continuous deviations caused by changes in the curvature of the outer wall of the storage tank, low-frequency drift of the bevel direction, or assembly errors. The target correction speed is obtained by superimposing the base correction speed and the compensation correction speed. The controller then determines the lateral movement direction based on the sign of the deviation: it corrects to the right when the deviation is positive, to the left when the deviation is negative, and remains stationary when the deviation is zero. This logic ensures that the lateral correction of the welding torch 10 is consistent with the deviation direction, reducing unnecessary reciprocating adjustments. Specifically, the calculation rules of the closed-loop kinematic compensation model for the target correction speed are shown in the following formula:

[0033] In the formula, The target correction velocity at the current sampling moment is measured in mm / s. proportionality constant, dimensionless ; The lateral physical deviation at the current sampling time, in mm; Integral coefficient, dimensionless ; The summation symbol indicates that the horizontal physical deviation of the historical sampling period is accumulated item by item; N is the total number of historical sampling periods, which is a dimensionless positive integer. The lateral physical deviation in the j-th historical sampling period, with the dimension in mm; j is the cumulative sequence number of the historical sampling. Let j be the j-th historical sampling time; t be the current sampling time; this correction control logic essentially constructs a closed-loop kinematic compensation model; Its purpose is to accurately calculate the compensation action of the servo motor 33 based on the real-time analyzed physical deviation during dynamic welding, so as to achieve smooth and zero static error automatic correction. In terms of logic structure and data flow, the model includes a proportional calculation branch and an integral calculation branch that are parallel to each other. Both of them receive the lateral physical deviation as input. The proportional branch outputs the basic correction speed in real time, and the integral branch outputs the compensation correction speed by accumulating historical data. The two are combined into the summation module to output the target correction speed. At the same time, the direction determination module outputs the direction command independently according to the positive or negative sign of the input. In terms of the physical relationship represented, the model represents the physical superposition effect of the welding torch 10 correction system's ability to respond quickly to instantaneous spatial position errors and eliminate steady-state hysteresis caused by long-term accumulated assembly errors or changes in tank curvature. Due to the combination of proportional and integral dual control mechanisms, the welding torch 10 can not only quickly follow the sudden turning of the bevel, but also overcome the response delay caused by mechanical transmission inertia, and achieve high-precision trajectory tracking. The proportional coefficient is used to determine the amplification factor of the deviation on the instantaneous speed response. Its setting principle is to make the correction displacement of the welding torch 10 within a single sampling period less than the allowable deviation band of the bevel, so as to avoid overshoot. The integral coefficient is used to determine the intensity of the influence of the historical deviation accumulation on the continuous correction. It is adjusted during debugging according to the response hysteresis of the welding torch 10, the transmission inertia of the lead screw 35, and the allowable convergence time, so as to gradually eliminate the steady-state deviation without causing oscillation. The target correction speed further corresponds to the speed command of the servo motor 33, which the industrial controller converts into a pulse frequency output consistent with the lateral movement direction, so that the correction process has a clear speed level and direction level; in addition, during mechanical operation, when the servo motor 33 drives the lead screw 35 through the coupling, there will inevitably be a backlash in the reverse transmission and a sudden change in nonlinear resistance when the static friction is converted to dynamic friction. If only the ideal linear proportional integral calculation is relied upon, when the welding torch 10 needs to be finely adjusted in the reverse direction, the target correction speed command may be absorbed by the transmission gap or unable to overcome static friction, resulting in the continuous invalid accumulation of the integral term and eventually causing overshoot oscillation; therefore, a nonlinear friction and gap compensation mechanism is further introduced into the calculation rules of this closed-loop kinematic compensation model. The specific calculation rules are as follows: When the industrial controller determines that the lateral movement direction has reversed, before outputting the target correction speed, a preset backlash compensation pulse sequence is first added to the servo motor 33 to quickly eliminate the backlash of the lead screw 35 nut pair; at the same time, when the target correction speed is less than the preset speed switching threshold, a starting compensation speed constant with the dimension of mm / s and equivalent to static friction is superimposed. Once the speed feedback from the encoder built into the servo motor 33 is detected to reach the stable rotation threshold, the starting compensation speed constant is canceled. To prevent the integral branch from accumulating ineffectively due to the physical deviation not being eliminated during the mechanical lag of overcoming static friction and eliminating backlash, which could lead to integral saturation and overshoot due to exceeding the limit, the closed-loop kinematic compensation model also incorporates a conditional integral freezing mechanism. The specific execution logic is as follows: when the industrial controller is outputting a gap compensation pulse sequence, or when the target correction speed is in the static friction equivalent compensation range and the absolute value of the lateral physical deviation does not show a decreasing trend, the industrial controller actively pauses the accumulation of the lateral physical deviation in the historical sampling period and keeps the current accumulated value unchanged. Normal integral accumulation resumes only after it is determined that the mechanical transmission chain has established rigid contact and the servo motor 33 has entered a stable rotation state. The preset speed switching threshold, gap compensation pulse sequence, start compensation speed constant, and stable rotation threshold are all based on the factory torque parameters of the servo motor 33 and the theoretical backlash data of the lead screw 35, and are calibrated during the initialization of the industrial controller. Through this structured decomposition and compensation, the defect of ideal linear control failing under complex mechanical friction and gap interference is effectively overcome, ensuring smooth correction under working conditions. To ensure that the correction control logic has a clear programmable implementation boundary, the industrial controller can split the target correction speed into two data streams: an instantaneous error component and a cumulative error component, which are calculated separately. At the end of each sampling period, a direction indicator and a speed amplitude are output in a unified manner. The direction indicator is determined only by the positive or negative sign of the deviation, and the speed amplitude is determined only by the proportional branch and the integral branch. In this way, control commands that can be directly mapped to the servo drive pulse frequency and pulse direction can be formed.

[0034] Example 2: like Figure 5 As shown, a welding method for the outer wall of a modular chemical storage tank includes the following steps: S1, Reference Calibration Stage: Adsorb the mobile chassis 1 onto the outer wall of the chemical storage tank, adjust the support frame 3 so that the welding torch 10 is aligned with the center line of the bevel 11 to be welded, start the pressure stabilizing valve 29 to continuously supply gas, and record the voltage signal output by the linear variable differential transformer 24 at this time as the center reference voltage. S2, Air Pressure Sensing and Mechanical Filtering Stage: During the welding process, the airflow forms a local air resistance in the gap between the left air probe 13, the right air probe 14 and the edge of the groove to be welded 11. When the welding torch 10 deviates from the center line of the groove to be welded 11, a pressure difference is formed in the connecting path. The differential pressure signal drives the elastic diaphragm 20 to deform and drives the central push rod 23 to move. The linear variable differential transformer 24 outputs the corresponding voltage signal. S3, Deviation Conversion Stage: The industrial controller obtains the lateral physical deviation based on the sampled voltage signal and the central reference voltage. S4, Correction Control Stage: The industrial controller determines the target correction speed and the lateral movement direction based on the lateral physical deviation. S5, Execution Output Stage: The industrial controller converts the target correction speed into control pulses and sends them to the servo motor 33. The servo motor 33 drives the lead screw 35 to move the welding torch 10 toward the center line of the bevel to be welded 11.

[0035] This method is used to achieve continuous tracking of the bevel of the outer wall of the storage tank by the welding torch 10. In the benchmark calibration stage, after the moving chassis 1 is attached to the tank wall, the welding torch 10 is aligned with the center line of the bevel by adjusting the support frame 3. The output voltage of the linear variable differential transformer 24 under stable gas supply is recorded as the central benchmark for subsequent deviation determination. During the welding process, the left air probe 13 and the right air probe 14 form local air resistance on both sides of the bevel. When the welding torch 10 deviates from the center line, the air resistance on both sides is inconsistent, causing differential pressure in the diaphragm cavity 18. The differential pressure pushes the elastic diaphragm 20 and the central push rod 23 to move. The linear variable differential transformer 24 outputs a voltage signal corresponding to the offset. The industrial controller converts the signal to obtain the lateral physical deviation, and generates the target correction speed and direction of movement accordingly. The servo motor 33 converts the control pulse into the rotation of the lead screw 35. The lead screw 35 drives the welding torch 10 to correct laterally, so that the position of the welding torch 10 gradually returns to the vicinity of the bevel center. The central reference voltage is used to represent the zero-deviation voltage state of the welding torch 10 when it is at the center line of the bevel and the pressure on both sides of the diaphragm is basically balanced during calibration. It is re-acquired after each power-on of the device or after the installation position of the welding torch 10 is changed to eliminate the zero-point offset caused by installation errors and device drift. The control pulse is generated by the industrial controller according to the target correction speed. The pulse frequency corresponds to the lateral correction speed, the pulse direction corresponds to the left or right correction direction, and when the pulse stops, the servo motor 33 maintains the current position. This makes the processing link from voltage signal, deviation, speed command to mechanical displacement public step by step, which is easy to understand and implement.

[0036] During the deviation conversion stage, when the deviation between the voltage signal and the center reference voltage is less than the preset dead zone voltage threshold, the industrial controller outputs a zero speed command and the servo motor 33 remains stationary; when the deviation between the voltage signal and the center reference voltage is greater than or equal to the dead zone voltage threshold, the industrial controller outputs a non-zero speed command.

[0037] During the air pressure sensing and mechanical filtering stage, since the environmental wind disturbance is usually large-scale and uniform, the air pressure changes acting on the left blowing probe 13 and the right blowing probe 14 are in the same direction and have the same amplitude, resulting in equal pressure increments in the positive pressure chamber 21 and the negative pressure chamber 22 of the diaphragm cavity 18. Ultimately, the common mode pressure fluctuations cancel each other out on both sides of the elastic diaphragm 20, and no displacement of the central push rod 23 is generated. Meanwhile, since the capillary damper 31 has high flow resistance characteristics, when welding spatter causes transient high-frequency pressure pulses, the gas cannot overcome the flow resistance to fill or discharge the cavity within the transient high-frequency cycle, thereby filtering out high-frequency interference at the physical level and avoiding converting it into diaphragm displacement. During the deviation conversion stage, since the dead zone voltage threshold limits the system's tolerance insensitive range at the algorithm level, when the lateral physical deviation is less than the dead zone voltage threshold, the system determines that the welding torch 10 is within a reasonable process tolerance zone. The industrial controller outputs a zero speed command to keep the servo motor 33 stationary, thereby avoiding frequent forward and reverse fine-tuning and mechanical wear caused by transmission backlash. When the deviation reaches or exceeds the threshold, a non-zero speed command is output to drive the welding torch 10 to make necessary corrections. This causal processing mechanism ensures that the output of the control system is only for real and continuous trajectory deviations, effectively shielding multi-source short-term interference.

[0038] During the output phase, the industrial controller continuously compares the difference between the voltage signal and the center reference voltage. When the deviation between the voltage signal and the center reference voltage is less than the dead zone voltage threshold, the industrial controller stops outputting control pulses; when the deviation between the voltage signal and the center reference voltage is greater than or equal to the dead zone voltage threshold, the industrial controller continues to output control pulses.

[0039] During the output phase, the welding torch 10 moves laterally under the action of the control pulse, and the gaps between the left and right air probes 13 and 14 and the edge of the bevel converge to a symmetrical state. The differential pressure between the positive pressure chamber 21 and the negative pressure chamber 22 gradually decreases. After the differential pressure weakens, the elastic diaphragm 20 returns to a position close to equilibrium, and the output voltage of the linear variable differential transformer 24 gradually returns to the center reference voltage. The industrial controller continuously compares the lateral physical deviation with the dead zone voltage threshold. When the deviation returns to within the threshold, it stops outputting control pulses, and the servo motor 33 maintains its current position. When the deviation still reaches or exceeds the threshold, it continues to output control pulses until the welding torch 10 returns to the allowable tracking bandwidth. This method gives the welding torch 10 a clear stopping condition during the correction process, which makes it easier to maintain the stability of the weld seam tracking position.

[0040] The various embodiments of this disclosure have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or technical improvements to the embodiments in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A combined chemical storage tank outer wall welding device, comprising: A mobile chassis (1) and a support frame (3), wherein the support frame (3) is connected to a cross slide (5), and a welding torch (10) is mounted on the cross slide (5), characterized in that it further includes: The air pressure sensing module (12) includes a left air blowing probe (13) and a right air blowing probe (14), which are symmetrically mounted on both sides of the front end of the welding torch (10), with their end faces facing the two sides of the bevel (11) to be welded respectively; Mechanical filtering and conversion module (17) is fixed to a mobile chassis (1) and includes a diaphragm cavity (18), an elastic diaphragm (20) and a linear variable differential transformer (24). The edge of the elastic diaphragm (20) is clamped and fixed in the diaphragm cavity (18) to divide it into a positive pressure chamber (21) and a negative pressure chamber (22). The center of the diaphragm is connected to the center push rod (23), which is connected to the core (25) of the linear variable differential transformer (24). The gas source and damping module (28) includes a connected pressure regulating valve (29) and a gas distribution manifold (30). The outlet of the manifold (30) is connected to the left air probe (13) and the right air probe (14), respectively. The two probes are connected to the positive pressure chamber (21) and the negative pressure chamber (22), respectively. Each connection path is connected in series with a capillary damping tube (31). The drive and control module (32) includes an industrial controller, a servo motor (33), and a lead screw (35). The industrial controller is electrically connected to the linear variable differential transformer (24) and the servo motor (33). The servo motor (33) is connected to the lead screw (35) and drives the cross slide (5) to move the welding torch (10) laterally.

2. The combined chemical storage tank outer wall welding device according to claim 1, characterized in that, The left air probe (13) and the right air probe (14) are both fixed to the welding torch (10) by a stainless steel connecting rod (15). The left air probe (13) and the right air probe (14) are respectively connected to the positive pressure chamber (21) and the negative pressure chamber (22) by a high-temperature resistant Teflon pressure tube (16).

3. The combined chemical storage tank outer wall welding device according to claim 2, characterized in that, The capillary damping tube (31) is connected in series with the high-temperature resistant Teflon pressure tube (16) between the left air blowing probe (13) and the positive pressure chamber (21), and the high-temperature resistant Teflon pressure tube (16) between the right air blowing probe (14) and the negative pressure chamber (22). The inner diameter of the capillary damping tube (31) is 0.5 mm, and the length of the capillary damping tube (31) is 50 mm.

4. The combined chemical storage tank outer wall welding device according to claim 1, characterized in that, The mobile chassis (1) is attached to the outer wall of the chemical storage tank by magnetic suction wheel (2). The support frame (3) is fixedly connected to the upper surface of the mobile chassis (1) by bolts. The top of the support frame (3) is slidably connected to the base (6) of the cross slide (5) by guide rail (4). The moving platform (7) of the cross slide (5) is fixedly connected to the welding gun (10) by flange (8).

5. The combined chemical storage tank outer wall welding device according to claim 4, characterized in that, The servo motor (33) drives the lead screw (35) through a plum blossom-shaped elastic coupling (34). The lead screw (35) is threadedly engaged with the nut seat (9) at the bottom of the moving platform (7) of the cross slide (5). The diaphragm cavity (18) is fixed to the rear of the moving chassis (1) by bolts. The coil frame (26) of the linear variable differential transformer (24) is fixed to the outer shell (19) of the diaphragm cavity (18) by a mounting bracket (27).

6. The combined chemical storage tank outer wall welding device according to claim 1, characterized in that, The industrial controller has built-in deviation conversion logic and pre-stores center reference voltage, dead zone voltage threshold and displacement conversion coefficient. The deviation conversion logic includes: obtaining the lateral physical deviation based on the currently acquired voltage, the center reference voltage, the dead zone voltage threshold and the displacement conversion coefficient; when the deviation between the currently acquired voltage and the center reference voltage does not reach the dead zone voltage threshold, a zero speed command is output.

7. The combined chemical storage tank outer wall welding device according to claim 6, characterized in that, The industrial controller has built-in correction control logic, which includes: obtaining the target correction speed based on the lateral physical deviation; the industrial controller determines the lateral movement direction according to the positive or negative sign of the lateral physical deviation, determining to move to the right when the lateral physical deviation is greater than zero, determining to move to the left when the lateral physical deviation is less than zero, and remaining stationary when the lateral physical deviation is equal to zero.

8. A method for welding the outer wall of a combined chemical storage tank, implemented based on the welding apparatus for the outer wall of a combined chemical storage tank as described in claim 1, characterized in that, Including the following steps: S1, Reference calibration stage: The mobile chassis (1) is attached to the outer wall of the chemical storage tank, the support frame (3) is adjusted so that the welding gun (10) is aligned with the center line of the bevel (11) to be welded, the pressure stabilizing valve (29) is started to continuously supply gas, and the voltage signal output by the linear variable differential transformer (24) at this time is recorded as the center reference voltage. S2, Pressure Sensing and Mechanical Filtering Stage: During the welding process, the airflow forms a local air resistance in the gap between the left air probe (13), the right air probe (14) and the edge of the groove to be welded (11). When the welding torch (10) deviates from the center line of the groove to be welded (11), a pressure difference is formed in the connecting path. The differential pressure signal drives the elastic diaphragm (20) to deform and drives the central push rod (23) to move. The linear variable differential transformer (24) outputs the corresponding voltage signal. S3, Deviation Conversion Stage: The industrial controller obtains the lateral physical deviation based on the sampled voltage signal and the central reference voltage; S4. Correction control stage: The industrial controller determines the target correction speed and the lateral movement direction based on the lateral physical deviation. S5, Execution output stage: The industrial controller converts the target correction speed into control pulses and sends them to the servo motor (33). The servo motor (33) drives the lead screw (35) to drive the welding gun (10) to correct towards the center line of the groove to be welded (11).

9. The welding method for the outer wall of a combined chemical storage tank according to claim 8, characterized in that, During the deviation conversion stage, when the deviation between the voltage signal and the center reference voltage is less than the preset dead zone voltage threshold, the industrial controller outputs a zero speed command and the servo motor (33) remains stationary; when the deviation between the voltage signal and the center reference voltage is greater than or equal to the dead zone voltage threshold, the industrial controller outputs a non-zero speed command.

10. The welding method for the outer wall of the combined chemical storage tank according to claim 8, characterized in that, During the execution output phase, the industrial controller continuously compares the difference between the voltage signal and the center reference voltage. When the deviation between the voltage signal and the center reference voltage is less than a preset dead zone voltage threshold, the industrial controller stops outputting control pulses. When the deviation between the voltage signal and the center reference voltage is greater than or equal to the dead zone voltage threshold, the industrial controller continues to output control pulses.

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