Gravity heat exchange tube welding device and control system

Abstract

The present application discloses a gravity heat exchange pipe welding device and control system, and relates to the technical field of heat exchange equipment manufacturing, which comprises a machine base, a workpiece positioning platform, a welding execution end and a control system. The welding execution end is integrated with a hollow shaft rotary drive unit and a welding tool head. A detection sleeve is coaxially sleeved on the outer periphery of the welding tool head and can independently slide axially. At least three non-contact displacement sensors are embedded in the end of the detection sleeve. A six-dimensional force sensor is fixed to the root of the welding tool head. During the welding process, the six-dimensional force sensor real-time feedbacks the radial offset force component of the welding tool head. When the offset force component exceeds the preset threshold, the control system will be used as a correction term to the center axis equation for secondary operation to obtain the instantaneous compensation axis. The welding execution end drives the welding tool head for real-time dynamic compensation. The present application can correct the pose of the welding tool head in real time during the welding process, and is suitable for the tube sheet welding of the tube sheet heat exchanger.

Description

Technical Field

[0001] This invention relates to the field of heat exchange equipment manufacturing technology, specifically to a gravity heat exchange tube welding device and control system. Background Technology

[0002] In the field of heat exchange equipment manufacturing, especially in the production of tube sheet heat exchangers, the welding quality and efficiency of heat exchange tubes and tube sheets directly determine product performance and manufacturing costs. Existing technology CN110860824A discloses a welding system for heat exchange tubes, the core of which employs a crosshead positioning device. This device locates the center of the tube hole through physical contact and pressure sensor feedback, and works in conjunction with a rotating cylinder to achieve station switching for the welding device. This system overcomes, to a certain extent, the drawbacks of traditional visual positioning, such as susceptibility to weld blackening and the need for secondary grinding, thus improving the stability and automation of positioning.

[0003] However, in-depth analysis revealed inherent technical flaws in the system. First, its positioning reference suffers from the risk of accumulated secondary transmission errors: the crosshead positioning module and the welding torch are installed at different positions on the outer circumferential wall of the rotating cylinder. During operation, the cylinder must first rotate to the detection position to obtain the pipe hole center data, and then rotate half a turn to send the welding torch to the same station for welding. The detection, withdrawal, rotation, and reproduction process relies entirely on the memory and mechanical reproduction of previous position data. Mechanical return clearance of the rotating cylinder, encoder pulse errors, and long-term wear can all cause the actual landing point of the welding torch to deviate from the theoretical center, especially for deep-hole or thin-walled pipe welding, easily resulting in misaligned welds or incomplete fusion. Second, the system lacks effective compensation and utilization of gravity: its multi-stage cylinder-driven welding torch moving platform has a cantilever structure. In different spatial orientations, such as flat welding, vertical welding, and overhead welding positions, its own gravity and pipeline drag force can cause end-positioning accuracy and directional drift. Furthermore, without any gravity compensation or attitude adaptive strategy, it is difficult to guarantee the consistency of weld quality across the circumference of the pipe sheet. In addition, the tube sheet clamping module has limited rigidity and is prone to micro-deformation under the action of welding thermal cycle. The system lacks a real-time monitoring and compensation mechanism. At the same time, the conveying device can only push the heat exchange tube in one direction and cannot correct the coaxiality deviation caused by the weight of the tube itself. This results in uneven gaps between the end of the heat exchange tube and the root of the welding hole, which affects the root penetration.

[0004] It is evident that the existing technology is essentially still an open-loop memory positioning and fixed posture welding mode, which fails to solve the technical problems of accuracy loss during rotation switching, gravity influence, and thermal deformation compensation, and urgently needs improvement. Summary of the Invention

[0005] The purpose of this invention is to provide a gravity heat exchanger tube welding device and control system to solve the problems mentioned in the background art.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a gravity heat exchanger tube welding device, comprising a base, a workpiece positioning platform disposed on the base, a welding execution end disposed above the workpiece positioning platform and movable along three orthogonal directions in space, and a control system respectively connected to the welding execution end and each drive mechanism, wherein the welding execution end integrates:

[0007] A hollow shaft rotary drive unit, the output end of which is fixedly connected to a welding tool head;

[0008] A detection sleeve is coaxially sleeved on the outer periphery of the welding tool head. An axial sliding guide structure is provided between the detection sleeve and the welding tool head. The detection sleeve is driven by a first driving element to slide independently axially relative to the welding tool head.

[0009] At least three non-contact displacement sensors are uniformly embedded in the end of the detection sleeve in the circumferential direction, and the detection direction of each non-contact displacement sensor is parallel to the radial direction of the detection sleeve.

[0010] A six-dimensional force sensor is fixedly installed at the root of the welding tool head to sense the force vector acting on the welding tool head in its spatial orientation.

[0011] The control system includes a data fusion and pose calculation module, which is configured to: when the detection sleeve extends and the non-contact displacement sensor is close to the end face of the tube hole of the tube plate to be welded, receive radial distance data of multiple cross sections of the inner wall of the tube hole collected by each of the non-contact displacement sensors, fit the actual spatial center axis equation of the tube hole and use it as the initial positioning reference.

[0012] While the welding tool head is inserted into the pipe hole along the initial positioning reference to perform welding, the data fusion and pose calculation module continuously receives the real-time force signal fed back by the six-dimensional force sensor. It separates the radial offset force component of the welding tool head from the real-time force signal. When the radial offset force component exceeds a preset force threshold, the data fusion and pose calculation module substitutes the radial offset force component as a correction term into the equation of the actual spatial center axis for secondary calculation to obtain the instantaneous compensation axis under the current working condition. The control system drives the welding execution end to dynamically compensate the real-time pose of the welding tool head according to the instantaneous compensation axis.

[0013] Preferably, the non-contact displacement sensor is a laser triangulation sensor or an eddy current sensor, and each of the non-contact displacement sensors is independently connected to the data acquisition port of the control system.

[0014] Preferably, the welding tool head is connected to the output end of the hollow shaft rotary drive unit via a universal joint linkage mechanism; the universal joint linkage mechanism includes a ball joint support fixed to the output end of the hollow shaft rotary drive unit, a ball head rod fixedly connected to the root of the welding tool head, and at least four electrically controlled proportional throttling dampers circumferentially embedded between the ball joint support and the ball head rod, wherein the damping coefficient of each electrically controlled proportional throttling damper is independently adjusted by the control system based on the direction and magnitude of the gravity vector fed back by the six-dimensional force sensor.

[0015] Preferably, the control system separates the gravity vector from the real-time force signal of the six-dimensional force sensor, and calculates the component force of the gravity vector in each radial direction according to the current spatial attitude angle of the welding execution end. The control system independently adjusts the damping coefficient of each of the electronically controlled proportional throttling dampers according to the component force value in each radial direction, so that the reaction force applied by each of the electronically controlled proportional throttling dampers to the ball joint is opposite to the direction of the gravity component force in the corresponding radial direction.

[0016] Preferably, the workpiece positioning platform is provided with an annular guide rail, and the welding execution end is slidably engaged with the annular guide rail via a sliding seat; the sliding seat integrates a magnetorheological fluid damping unit, and the damping coefficient of the magnetorheological fluid damping unit is dynamically adjusted by the control system.

[0017] Preferably, the welding device further includes an infrared temperature measuring array fixedly mounted on the workpiece positioning platform. The detection field of the infrared temperature measuring array covers the tube sheet mounting area on the workpiece positioning platform. The control system receives the welding zone temperature field signal fed back by the infrared temperature measuring array and adjusts the damping coefficient of the magnetorheological fluid damping unit according to the temperature field signal.

[0018] Preferably, the workpiece positioning platform is embedded with a distributed fiber optic strain sensor. The signal output end of the distributed fiber optic strain sensor is connected to the signal input end of the control system. The control system generates a full-domain deformation cloud map of the tube sheet based on the tube sheet deformation data fed back by the distributed fiber optic strain sensor, and pre-calculates the center offset of the next hole to be welded based on the deformation cloud map. Before the welding tool head moves to the next hole to be welded, the control system corrects the initial positioning coordinates of the welding execution end based on the center offset.

[0019] Preferably, the data fusion and pose calculation module performs the following operations cyclically at a fixed sampling frequency: receiving the real-time force signal from the six-dimensional force sensor, separating the radial offset force component, comparing with a preset force threshold, calculating the instantaneous compensation axis, and outputting the pose correction amount; when the duration for which the radial offset force component continuously exceeds the preset force threshold exceeds a preset time threshold, the control system issues an alarm signal and stops the welding process of the current hole position.

[0020] A method for welding gravity heat exchanger tubes, using the aforementioned gravity heat exchanger tube welding device, includes the following steps:

[0021] S1. Initial positioning steps: The control system drives the detection sleeve to extend relative to the welding tool head, so that the non-contact displacement sensor at the end of the detection sleeve is close to the end face of the tube hole of the tube plate to be welded. Each non-contact displacement sensor collects radial distance data of multiple cross sections of the inner wall of the tube hole and feeds it back to the control system. The control system fits the equation of the actual spatial center axis of the tube hole as the initial positioning reference.

[0022] S2. Insertion welding step: The control system drives the welding tool head to insert into the pipe hole along the initial positioning reference, and starts welding;

[0023] S3. In-situ real-time sensing step: Throughout the welding process, the control system continuously receives real-time force signals from the six-dimensional force sensor and separates the radial offset force component of the welding tool head from the real-time force signals.

[0024] S4. Dynamic compensation step: When the radial offset force component exceeds the preset force threshold, the control system substitutes the radial offset force component as a correction term into the equation of the actual spatial center axis for secondary calculation to obtain the instantaneous compensation axis under the current working condition, and drives the welding execution end to perform dynamic compensation on the real-time pose of the welding tool head.

[0025] S5. Cyclic execution steps: The control system cyclically executes steps S3 to S4 at a fixed sampling frequency until the welding of the current hole position is completed.

[0026] Preferably, in step S3, the control system further separates the gravity vector from the real-time force signal of the six-dimensional force sensor, and calculates the component force of the gravity vector in each radial direction according to the current spatial attitude angle of the welding execution end. The control system independently adjusts the damping coefficient of each electronically controlled proportional throttling damper in the universal joint linkage mechanism according to the component force value in each radial direction, so that the reaction force applied by each electronically controlled proportional throttling damper to the ball joint is opposite to the direction of the gravity component force in the corresponding radial direction.

[0027] This invention provides a gravity heat exchanger tube welding device and control system. It has the following beneficial effects:

[0028] By coaxially integrating the detection sleeve and welding tool head onto the same welding execution end, the detection of the borehole center axis and the insertion and welding of the welding tool are continuously completed at the same station and on the same axis. This eliminates the intermediate switching links caused by detection and welding belonging to different stations, and avoids the damage to positioning accuracy caused by mechanical backlash and encoder pulse errors resulting from rotational switching. During the welding process, the six-dimensional force sensor continuously feeds back the radial offset force component of the welding tool head. The control system uses this offset force component as a correction term and substitutes it back into the borehole center axis equation for secondary calculation to obtain the instantaneous compensation axis and adjust the position and posture of the welding tool head in real time. This forms a closed-loop execution sequence of detection, welding, feedback, and correction, ensuring that the welding tool head always follows the actual center axis of the borehole throughout the welding process. This effectively suppresses the radial offset of the welding tool head caused by factors such as initial positioning deviation, thermal deformation extrusion, or asymmetric surface tension of the molten pool. The electronically controlled proportional throttling dampers in the universal joint linkage mechanism enable the control system to independently adjust the damping reaction force in each radial direction based on the direction and magnitude of the gravity vector fed back by the six-dimensional force sensor. This counteracts the off-center load caused by the welding tool head's own weight under different spatial postures, preventing the welding tool head from deviating from the preset axis direction due to gravity drooping. The distributed fiber optic strain sensors embedded inside the workpiece positioning platform monitor the deformation of the tube sheet under the action of welding thermal cycle in real time. The control system corrects the initial positioning coordinates in advance before the welding tool head moves to the next hole position, realizing feedforward compensation for thermal deformation.

[0029] The combination of the aforementioned detection sleeve and non-contact displacement sensor enables in-situ fitting of the central axis of the tube hole. The combination of a six-dimensional force sensor and a data fusion pose calculation module enables real-time sensing of radial offset force and dynamic pose compensation during welding. The combination of each electronically controlled proportional throttling damper in the universal joint linkage mechanism and gravity vector decomposition control enables neutralization of gravity off-center load under all spatial attitudes. The combination of distributed fiber optic strain sensors and sliding seats on the ring guide rail enables feedforward compensation of thermal deformation and stable support during the welding process. The synergy between these technical features ensures that the welding tool head can maintain axial alignment accuracy and attitude stability during welding of each hole in the circumferential direction of the tube sheet. This improves the welding defects such as off-center welding and lack of fusion that are prone to occur in deep hole welding and thin-walled tube welding, and enhances the consistency of weld formation in the circumferential direction of the tube sheet. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the gravity heat exchanger tube welding device and control system of the present invention;

[0031] Figure 2 This is a schematic diagram of the process of the present invention.

[0032] In the diagram: 1. Base; 2. Workpiece positioning platform; 3. Welding execution end; 4. Detection sleeve; 5. Non-contact displacement sensor; 6. Six-dimensional force sensor; 7. Hollow shaft rotation drive unit; 8. Welding tool head; 9. Ball joint support; 10. Ball head rod; 11. Electrically controlled proportional throttling damper; 12. Circular guide rail; 13. Sliding seat; 14. Magnetorheological fluid damping unit; 15. Infrared temperature measurement array; 16. Distributed fiber optic strain sensor. Detailed Implementation

[0033] 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, and 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.

[0034] Example: Please refer to Figure 1 and Figure 2 This invention provides a gravity heat exchanger tube welding device: a hollow shaft rotation drive unit 7 is integrated into the welding execution end 3, and a welding tool head 8 is fixedly connected to the output end of the hollow shaft rotation drive unit 7. The welding tool head 8 can be a welding torch or a laser welding head. The detection sleeve 4 has a cylindrical structure, with an inner diameter larger than the outer diameter of the welding tool head 8, and the detection sleeve 4 is coaxially sleeved on the outside of the welding tool head 8. An axial sliding guide structure is provided between the detection sleeve 4 and the welding tool head 8. The axial sliding guide structure includes a guide keyway formed in the inner wall of the detection sleeve 4 and a guide key fixed to the outer wall of the welding tool head 8, or includes an axial slide rail formed in the outer wall of the welding tool head 8 and a sliding block fixed to the inner wall of the detection sleeve 4. The detection sleeve 4 is driven by a first driving element to slide independently axially relative to the welding tool head 8. The first driving element can be an electric push rod or a pneumatic cylinder, the cylinder body of which is fixed to the housing of the welding execution end 3, and its output end is fixedly connected to the root of the detection sleeve 4. With this structure, the detection sleeve 4 can extend forward or retract backward independently while the welding tool head 8 remains stationary.

[0035] At least three non-contact displacement sensors 5 are uniformly embedded circumferentially at the end of the detection sleeve 4. These non-contact displacement sensors 5 can be laser triangulation sensors or eddy current sensors. When the detection sleeve 4 extends, its end face is close to the end face of the pipe hole in the tube sheet to be welded. Each non-contact displacement sensor 5 emits a detection signal towards the inner wall of the pipe hole and receives the reflected signal, thereby acquiring radial distance data in its respective detection direction. Due to the uniform circumferential distribution of the sensors, radial distance values ​​in multiple directions of the inner wall of the pipe hole can be obtained at a single axial position. During the extension process, the detection sleeve 4 can move axially to multiple different positions, thereby acquiring radial distance data of the inner wall of the pipe hole at multiple axial sections. Using the central axis of the pipe hole as the target to be fitted, and using the multiple radial distance data obtained at each section as constraint points, the least squares method is used for spatial linear fitting or spatial cylindrical surface fitting to solve for the equation of the actual spatial central axis of the pipe hole, including the spatial position coordinates and direction vector of the central axis. Specifically, during the extension of the sleeve 4, the control system selects four to six axial cross-sectional positions at equal intervals along the axial direction of the pipe hole. At each cross-sectional position, it reads the radial distance data of each non-contact displacement sensor 5, obtaining multiple spatial coordinate points at each cross-section. These spatial coordinate points are then compiled into a constraint point set. The control system performs outlier filtering on each coordinate point in the constraint point set, removing outliers whose distance to the fitted straight line exceeds three times the average distance of the remaining points. The removed point set is then fitted using the least squares method to obtain a spatial straight line equation that minimizes the sum of the squares of the distances from each constraint point to the fitted straight line. This spatial straight line equation is the actual spatial center axis equation of the pipe hole. This equation serves as the initial positioning reference for the subsequent insertion of the welding tool head 8.

[0036] The six-dimensional force sensor 6 referred to in this paper is a sensor capable of simultaneously detecting force components in three orthogonal directions and torque components around the three orthogonal directions. The six-dimensional force sensor 6 is fixedly mounted at the root of the welding tool head 8, located between the welding tool head 8 and the output end of the hollow shaft rotation drive unit 7. The six-dimensional force sensor 6 can simultaneously sense force components in three orthogonal directions and torque components around the three orthogonal directions. During the process of inserting the welding tool head 8 into the pipe hole and performing welding, the tip of the welding tool head 8 may come into slight contact with the molten pool, the inner wall of the pipe hole, or the weld formation area, or be subjected to thermal deformation and compression. Simultaneously, the weight of the welding tool head 8 itself will produce eccentric loads with changing directions under different spatial postures. The six-dimensional force sensor 6 continuously outputs real-time force signals to the data fusion and pose calculation module of the control system.

[0037] During the initial positioning phase, the data fusion and pose calculation module receives radial distance data collected by each non-contact displacement sensor 5 and performs the aforementioned fitting calculation to obtain the actual spatial center axis equation of the pipe hole. Once the welding tool head 8 is inserted into the pipe hole along this center axis and welding begins, the data fusion and pose calculation module continuously receives real-time force signals fed back by the six-dimensional force sensor 6. This real-time force signal contains all forces and torques acting on the welding tool head 8, including gravity components, inertial force components, and external contact force components. The data fusion and pose calculation module extracts the radial force component from the real-time force signal, i.e., the force perpendicular to the central axis of the pipe hole, as the radial offset force component. The specific extraction method is as follows: The data fusion and pose calculation module transforms the real-time force signal, based on the six-dimensional force sensor 6 coordinate system, into a local coordinate system with the pipe hole center axis as the Z-axis, using the sensor's installation orientation parameters relative to the welding execution end 3. The origin of this local coordinate system is located at the center of the welding tool head 8 front end. In the transformed local coordinate system, the real-time force signal is decomposed into an axial force component along the pipe hole axis and two radial force components perpendicular to the pipe hole axis. The two radial force components are vector-synthesized to obtain the radial offset force component. This radial offset force component reflects the actual radial offset that occurs at the front end of the welding tool head 8 within the pipe hole. The reasons for this offset may include: an initial deviation between the actual insertion direction of the welding tool head 8 and the true center axis of the pipe hole; displacement of the pipe hole center axis during welding due to welding thermal deformation; or lateral tension generated at the front end of the welding tool head 8 due to asymmetric surface tension of the molten pool.

[0038] The data fusion and pose calculation module has a preset force threshold, the specific value of which is determined based on the structural stiffness of the welding tool head 8 and the diameter tolerance of the tube hole. When the value of the radial offset force component is within the force threshold, it indicates that the actual pose deviation of the welding tool head 8 is within the allowable range, and the control system maintains the current drive parameters unchanged. When the radial offset force component exceeds the force threshold, the data fusion and pose calculation module uses the radial offset force component as a correction term and substitutes it back into the previously fitted actual spatial center axis equation for secondary calculation. The specific method of secondary calculation is as follows: the vector direction of the radial offset force component is taken as the offset direction, the amplitude of the radial offset force component is multiplied by a preset scaling factor to obtain the offset amount, and in a plane perpendicular to the original center axis direction, the spatial position coordinates of the original center axis are translated along the offset direction by the offset amount to obtain the offset spatial coordinate point; using the offset spatial coordinate point as the new position reference, keeping the direction vector of the original center axis unchanged, the spatial straight line equation is reconstructed, and the reconstructed spatial straight line equation is the instantaneous compensation axis under the current working condition. This instantaneous compensation axis reflects the true position of the actual center axis of the bore at the current welding moment.

[0039] The control system compares the spatial coordinates of the instantaneous compensation axis with the current actual pose of the welding tool head 8, calculates the positional and angular deviations between the two, and generates a pose correction amount. The control system distributes this pose correction amount to each drive mechanism that drives the welding execution end 3 to move along three orthogonal directions in space. Each drive mechanism performs corresponding displacement compensation according to the allocated correction amount, causing the real-time pose of the welding tool head 8 to align with the instantaneous compensation axis. During this process, the data fusion and pose calculation module executes cyclically in the above manner: receiving real-time force signals, determining whether the radial offset force component exceeds the force threshold, calculating the instantaneous compensation axis if it does, and outputting the pose correction amount, until the welding of the current hole position is completed.

[0040] Each non-contact displacement sensor 5 is embedded in the end of the detection sleeve 4. The end face of the detection sleeve 4 has the same number of mounting holes as the number of sensors, with the mounting holes evenly distributed circumferentially, and the central axis of each mounting hole parallel to the radial direction of the detection sleeve 4. One non-contact displacement sensor 5 is fixedly installed in each mounting hole.

[0041] The laser triangulation rangefinder consists of a laser emitter, a receiving lens, and a linear array photodetector. The laser emitter emits a laser beam towards the inner wall surface of the tube. After the laser beam strikes the inner wall surface, it forms a diffuse reflection spot, which is then imaged onto the linear array photodetector by the receiving lens. When the distance between the inner wall surface of the tube and the sensor front changes, the imaging position of the diffuse reflection spot on the linear array photodetector shifts accordingly. The linear array photodetector outputs an electrical signal corresponding to this imaging position, and the value of this electrical signal corresponds to the distance value.

[0042] An eddy current sensor consists of a detection coil located at the sensor's front end and a high-frequency oscillation circuit. The high-frequency oscillation circuit applies a high-frequency alternating current to the detection coil, generating a high-frequency alternating magnetic field around the coil. When the detection coil approaches the metal surface of the inner wall of the tube, eddy currents are generated on the metal surface under the influence of this high-frequency alternating magnetic field. The reaction magnetic field generated by the eddy currents causes a change in the equivalent impedance of the detection coil. This change in equivalent impedance is converted into a voltage or current signal by a signal conditioning circuit, and the value of this voltage or current signal corresponds to the distance from the sensor's front end to the inner wall surface of the tube.

[0043] Each non-contact displacement sensor 5 has its signal output terminal connected to the data acquisition port of the control system via an independent signal transmission line. The data acquisition port in the control system contains the same number of independent acquisition channels as the number of sensors, with each independent acquisition channel corresponding to one non-contact displacement sensor 5. Each independent acquisition channel is equipped with a signal conditioning circuit, including an amplification circuit and a filtering circuit, used to amplify the amplitude and filter noise from the raw electrical signal output by the sensor. After conditioning, the signals from each channel are converted into digital signals by the analog-to-digital converter in the data acquisition port and then sent to the data fusion and pose calculation module.

[0044] Since each non-contact displacement sensor 5 uses an independent acquisition channel, the data fusion and pose calculation module can acquire the distance data of each sensor in its respective detection direction at the same sampling time.

[0045] The output end of the hollow shaft rotary drive unit 7 is located at the front end of the hollow shaft, and this front end is provided with an end face flange. A connecting flange is provided at the root of the welding tool head 8. A universal joint linkage mechanism is located between the end face flange and the connecting flange. A ball joint support 9 is fixedly connected to the end face flange by bolts, and a spherical concave surface is provided on the end face of the ball joint support 9 facing away from the hollow shaft rotary drive unit 7. One end of the ball head rod 10 is fixedly connected to the connecting flange of the welding tool head 8, and the other end of the ball head rod 10 is provided with a spherical convex surface. The spherical convex surface is embedded in the spherical concave surface, and the outer spherical surface of the convex surface slides in contact with the inner spherical surface of the concave surface, allowing the ball head rod 10 to swing relative to the ball joint support 9 in any radial direction. A limit ring is provided at the opening edge of the spherical concave surface, and the inner diameter of the limit ring is smaller than the diameter of the spherical convex surface to prevent the ball head rod 10 from dislodging from the ball joint support 9.

[0046] At least four electrically controlled proportional throttling dampers 11 are disposed between the ball joint support 9 and the ball head rod 10. The electrically controlled proportional throttling dampers 11 are evenly distributed circumferentially around the axis of the ball joint support 9, with equal circumferential angles between adjacent dampers. The ball joint support 9 has the same number of damper mounting cavities as the number of dampers, each cavity penetrating radially through the side wall of the ball joint support 9, and the inner end of each cavity opening onto the inner surface of a spherical concave surface. Each electrically controlled proportional throttling damper 11 is installed within its corresponding damper mounting cavity.

[0047] Each electronically controlled proportional throttling damper 11 includes a plunger rod and an electromagnetic proportional valve. The plunger rod is slidably disposed within the damper mounting cavity along its axial direction. The inner end of the plunger rod protrudes from the inner surface of the spherical concave surface and contacts the spherical convex surface of the ball-end rod 10. A return spring is disposed between the outer end of the plunger rod and the outer wall of the damper mounting cavity. The interior of the damper mounting cavity is filled with magnetorheological fluid or hydraulic oil.

[0048] The electromagnetic proportional valve is located at the outer end of the damper mounting cavity. Its inlet and outlet are connected to the interior of the cavity. The valve core opening is adjusted by a current signal output from the control system. When the valve core opening changes, the liquid damping force acting on the inner end of the plunger rod changes accordingly. This liquid damping force is transmitted through the plunger rod to the spherical convex surface of the ball-end rod 10, forming a resistance torque on the oscillation of the ball-end rod 10.

[0049] Each electromagnetic proportional valve of the electronically controlled proportional throttling damper 11 is connected to the corresponding output port of the control system through an independent control circuit. The control system outputs an independent current control signal to each electromagnetic proportional valve. Based on the direction and magnitude of the gravity vector in the real-time force signal fed back by the six-dimensional force sensor 6, the control system determines the value of the current control signal applied to each electronically controlled proportional throttling damper 11, so that the damping force generated by each electronically controlled proportional throttling damper 11 is independently regulated.

[0050] The real-time force signal output by the six-dimensional force sensor 6 includes force component data of the welding tool head 8 in three orthogonal directions in space, as well as torque component data around these three orthogonal directions. Upon receiving this real-time force signal, the data fusion and pose calculation module of the control system first filters the signal to remove high-frequency noise components, and then extracts the DC component from the filtered signal. This DC component is the projection value of the gravity vector acting on the welding tool head 8 onto the three axes of the sensor coordinate system. The control system internally stores the mass parameters of the welding tool head 8, which are fixed values ​​pre-measured through a calibration process after the welding tool head 8 is assembled. The control system also stores the installation orientation parameters of the six-dimensional force sensor 6 relative to each joint of the welding execution end 3, which are determined through calibration during equipment assembly.

[0051] The control system reads the position signals fed back by the encoders of the drive motors of each joint of the welding execution end 3 in real time. Based on the position signals of each joint, it calculates the current spatial attitude angle of the welding execution end 3 through forward kinematics. The standard method for forward kinematics calculation is as follows: each joint of the welding execution end 3 is regarded as a series linkage mechanism. Taking the reference point on the base 1 as the origin of the world coordinate system, the position and attitude of each joint coordinate system relative to the world coordinate system are calculated sequentially through a homogeneous coordinate transformation matrix based on the rotation angle value of each joint and the fixed length parameters of each link. Finally, the spatial position and attitude angle of the flange face of the welding execution end 3 in the world coordinate system are obtained. This spatial attitude angle includes the pitch angle of the welding execution end 3 rotating about the horizontal axis and the deflection angle of the welding execution end 3 rotating about the vertical axis. Based on this spatial attitude angle and the mass parameters of the welding tool head 8, the control system calculates the direction of the gravity vector in the world coordinate system. Since the welding tool head 8 is connected to the hollow shaft rotary drive unit 7 through a universal hinge linkage mechanism, and the hollow shaft rotary drive unit 7 changes its posture with the movement of each joint of the welding execution end 3, the direction of the gravity vector relative to the axis of the ball joint support 9 changes with the posture of the welding execution end 3.

[0052] The control system uses the axis of the ball joint support 9 as the reference direction and decomposes the gravity vector in the vertical plane of this reference direction to obtain the projection vector of the gravity vector on the radial plane. The direction of this projection vector is the direction of the resultant force of gravity in each radial direction. The control system then projects this projection vector onto the direction where each electronically controlled proportional throttling damper 11 is located to obtain the gravity component value in each radial direction. The gravity component value in each radial direction corresponds to the magnitude of the counterforce required to be provided by each electronically controlled proportional throttling damper 11.

[0053] The control system generates current control signals for each electronically controlled proportional throttling damper 11 based on the radial component of gravity. For a given electronically controlled proportional throttling damper 11, when the radial component of gravity corresponding to that damper increases, the current control signal output by the control system reduces the opening of the electromagnetic proportional valve core of that damper, thereby increasing the liquid damping force experienced by the plunger rod during movement. This damping force acts as a reaction force on the ball end rod 10, and its direction is opposite to that of the radial component of gravity. When the radial component of gravity decreases, the control system correspondingly increases the opening of the electromagnetic proportional valve core of that damper, thus reducing the damping force. The reaction forces generated by each electronically controlled proportional throttling damper 11 act together on the spherical convex surface of the ball end rod 10, causing the resultant force of the reaction forces from each damper on the ball end rod 10 to cancel out the resultant force of the welding tool head 8's own weight in the radial direction. This ensures that the welding tool head 8 can maintain its axial direction unaffected by its own gravity under any spatial orientation.

[0054] The upper surface of the workpiece positioning platform 2 is a planar structure used to support the tube sheet to be welded. An annular guide rail 12 is fixedly installed on the upper surface of the workpiece positioning platform 2. The annular guide rail 12 has a closed annular profile, the shape of which is adapted to the outer contour of the tube sheet to be welded. The cross-section of the annular guide rail 12 is V-shaped or rectangular, and the upper surface of the annular guide rail 12 is a sliding mating surface. The welding execution end 3 is installed on a sliding seat 13. The lower end of the sliding seat 13 is provided with a sliding groove adapted to the cross-sectional shape of the annular guide rail 12. The sliding groove engages with the annular guide rail 12, allowing the sliding seat 13 to slide freely along the extension direction of the annular guide rail 12. A drive motor is fixedly installed on the sliding seat 13. A drive gear is fixedly connected to the output shaft of the drive motor. A rack is provided on the side wall of the annular guide rail 12 along its extension direction. The drive gear meshes with the rack. When the drive motor runs, the meshing of the drive gear and rack drives the sliding seat 13 to move along the annular guide rail 12.

[0055] The sliding seat 13 has an internal damper mounting cavity, and the magnetorheological fluid damping unit 14 is disposed within the damper mounting cavity. The magnetorheological fluid damping unit 14 includes a cylinder, a piston rod, and an excitation coil. The cylinder is fixed to the cavity wall of the damper mounting cavity, and the cylinder is filled with magnetorheological fluid. One end of the piston rod extends out of the cylinder and is fixedly connected to the inner wall of the sliding seat 13. A piston head is fixed to the end of the piston rod located inside the cylinder, and the outer circumferential surface of the piston head slides and seals against the inner wall of the cylinder. A coil mounting groove is provided inside the piston head, and the excitation coil is wound in the coil mounting groove. The two ends of the excitation coil are led out of the cylinder through wires and electrically connected to the current output port of the control system.

[0056] When the control system outputs current to the excitation coil, the excitation coil generates a magnetic field around the piston head, which acts on the magnetorheological fluid inside the cylinder. The magnetorheological fluid behaves as a Newtonian fluid with low viscosity when there is no magnetic field; however, when subjected to a magnetic field, the magnetic particles in the magnetorheological fluid align in a chain-like structure along the direction of the magnetic field, increasing the viscosity and flow resistance. As the piston rod moves relative to the cylinder, the piston head compresses the magnetorheological fluid. The damping force generated by the fluid flowing in the gap between the piston head and the cylinder increases with the increase of the current in the excitation coil. The control system adjusts the magnitude of the current output to the excitation coil to change the damping characteristics of the magnetorheological fluid, thereby adjusting the damping force experienced by the sliding seat 13 as it slides along the annular guide rail 12, ensuring the stability of the sliding seat 13 during the operation of the welding execution end 3.

[0057] An infrared temperature measurement array 15 is fixedly installed on the upper surface of the workpiece positioning platform 2, located beside the tube sheet mounting area on the workpiece positioning platform 2. The infrared temperature measurement array 15 includes multiple infrared temperature measurement probes, which are arranged at intervals along a circular direction, with equal spacing between adjacent probes. The detection field of view of each infrared temperature measurement probe faces the tube sheet mounting area, and the detection fields of view of each probe overlap within the tube sheet mounting area, collectively covering the entire tube sheet mounting area. Each infrared temperature measurement probe contains an infrared detection element and a signal processing circuit. The infrared detection element receives infrared radiation from the tube sheet surface, converts the infrared radiation energy into an electrical signal, and the signal processing circuit amplifies and converts this electrical signal from analog to digital before outputting it to the control system.

[0058] When the welding tool head 8 welds the tube holes on the tube sheet, the welding heat source acts on the tube sheet surface around the tube holes, causing a change in the temperature field on the tube sheet surface. Each infrared temperature probe detects the infrared radiation energy on the tube sheet surface within its respective field of view and transmits the corresponding electrical signal to the control system in real time. Based on the electrical signals output by each infrared temperature probe, the control system calculates the temperature value at each detection location, thereby obtaining the temperature field distribution data of the tube sheet welding area.

[0059] The data fusion and pose calculation module of the control system identifies high-temperature and low-temperature regions in the temperature field of the tube sheet surface based on the temperature field distribution data, and calculates the real-time temperature value of the tube sheet surface at the current position of the welding tool head 8. The control system adjusts the current output to the excitation coil of the magnetorheological damping unit 14 based on this real-time temperature value. When the real-time temperature value at the current position of the welding tool head 8 increases, the control system increases the current of the excitation coil, increasing the damping force generated by the magnetorheological damping unit 14; when the real-time temperature value decreases, the control system decreases the current of the excitation coil, decreasing the damping force generated by the magnetorheological damping unit 14. The change in the damping force of the magnetorheological damping unit 14 alters the dynamic contact stiffness between the sliding seat 13 and the annular guide rail 12, thereby suppressing system vibration caused by heat input fluctuations during welding.

[0060] The workpiece positioning platform 2 is made of cast iron or steel plate, and has an internal fiber optic laying channel. The fiber optic laying channel is distributed in a grid or ring pattern along the lower surface of the workpiece positioning platform 2, covering the entire tube sheet mounting area. The distributed fiber optic strain sensor 16 includes a continuous optical fiber and fiber optic demodulators at both ends of the optical fiber. The optical fiber is laid within the fiber optic laying channel, with each segment of the fiber corresponding to a different location within the tube sheet mounting area. The optical fiber is arranged in a serpentine or spiral pattern within the laying channel, so that each segment of the optical fiber corresponds to a local area on the upper surface of the workpiece positioning platform 2. A protective sleeve is fitted over the optical fiber, and thermally conductive silicone grease is filled between the protective sleeve and the channel wall of the fiber optic laying channel to ensure that the optical fiber can sensitively sense temperature changes and mechanical strain caused by heat conduction from the tube sheet on the workpiece positioning platform 2.

[0061] One end of the optical fiber is connected to the light source output of the fiber optic demodulator, and the other end is connected to the signal receiver. The fiber optic demodulator emits a broadband or pulsed light source into the fiber and simultaneously receives the backscattered light signal generated within the fiber. The fiber optic demodulator is equipped with a spectral analysis module or a time-domain analysis module to calculate the strain and temperature values ​​at various locations along the fiber's length. When the workpiece positioning platform 2 undergoes thermal expansion or deformation due to heat conduction during tube sheet welding, the corresponding section of the optical fiber is stretched or compressed, causing a frequency shift or phase shift in the backscattered light signal within that section. The fiber optic demodulator calculates the corresponding strain value for that section based on this frequency shift or phase shift. The fiber optic demodulator then transmits the calculated strain value data at various locations along the fiber's length to the control system in real time.

[0062] After receiving strain value data at various positions transmitted by the fiber optic demodulator, the control system maps each strain value data to the corresponding coordinate position in the tube sheet mounting area based on the correspondence between the fiber optic positions and the areas on the upper surface of the workpiece positioning platform 2. Based on the strain values ​​at each coordinate position, the control system generates deformation distribution data for the entire tube sheet mounting area using a spatial interpolation algorithm, and presents it graphically as a global deformation cloud map of the tube sheet. This deformation cloud map includes the deformation displacement of each coordinate position within the tube sheet mounting area in three orthogonal spatial directions.

[0063] The control system internally stores the theoretical coordinate values ​​of each weldable hole on the tube sheet relative to the reference point of the tube sheet mounting area. After generating the deformation cloud map, the control system extracts the deformation displacement at the coordinate position corresponding to each weldable hole from the deformation cloud map, and superimposes this deformation displacement with the theoretical coordinate value of the weldable hole to obtain the actual coordinate value of each weldable hole under the current thermal deformation state. The control system compares the actual coordinate value of each weldable hole with the theoretical coordinate value to calculate the center offset of each weldable hole. This center offset includes the offset direction and offset distance.

[0064] As the welding execution end 3 completes welding at the current hole position and moves towards the next hole position to be welded, the control system retrieves the center offset of the next hole position from memory before the welding tool head 8 reaches it. This center offset is then superimposed on the initial positioning coordinates of the welding execution end 3 to generate corrected positioning coordinates. Based on these corrected coordinates, the control system drives the welding execution end 3 to move to the corrected coordinate position, ensuring that the center of the front end of the welding tool head 8 is aligned with the actual center of the pipe hole when it is inserted into the next hole position.

[0065] The data fusion and pose calculation module of the control system has an internal timer that generates a sampling trigger signal at fixed time intervals. These fixed time intervals are pre-stored in the parameter register of the control system. When each sampling trigger signal arrives, the data fusion and pose calculation module reads the real-time force signal output by the six-dimensional force sensor 6 from the data acquisition port, extracts the force component perpendicular to the central axis of the pipe hole as the radial offset force component from the real-time force signal, and then compares this radial offset force component with a preset force threshold.

[0066] The data fusion and pose calculation module of the control system also includes a counter that records the number of times the radial offset force component continuously exceeds a preset force threshold. At each sampling moment, when the data fusion and pose calculation module determines that the currently read radial offset force component exceeds the preset force threshold, the counter increments by one; when it determines that the currently read radial offset force component does not exceed the preset force threshold, the counter is reset to zero. After each counter value update, the data fusion and pose calculation module compares the current counter value with the preset count threshold. This preset count threshold is a fixed integer value, pre-stored in the parameter register of the control system.

[0067] When the counter's current value reaches the preset threshold, it indicates that the radial offset force component has continuously exceeded the preset threshold for a predetermined duration. At this time, the control system sends an alarm signal to the operation interface, the alarm indicator light on the operation interface illuminates, and an audible alert is emitted. Simultaneously, the control system sends a stop command to the drive controllers of each drive mechanism at the welding execution end 3. Upon receiving the stop command, each drive mechanism immediately stops operating, keeping the welding tool head 8 in its current position and preventing further movement. The control system also simultaneously sends a stop command to the hollow shaft rotation drive unit 7, causing the welding tool head 8 to stop welding, and the welding process at the current hole position is terminated.

[0068] When the current value of the counter has not reached the preset threshold, the data fusion and pose calculation module uses the radial offset force component read at the current sampling moment as a correction term and substitutes it into the equation of the actual spatial center axis for secondary calculation to obtain the instantaneous compensation axis under the current working condition. Based on this instantaneous compensation axis, it generates a pose correction amount and outputs it to the drive controller of each drive mechanism to drive the welding execution end 3 to dynamically compensate the real-time pose of the welding tool head 8. The above process is repeated at each sampling moment until the welding of the current hole position is completed or the welding process is stopped.

[0069] In the initial positioning step, the control system sends an extension command to the first driving element, which drives the detection sleeve 4 to extend forward relative to the welding tool head 8. During the extension process, each non-contact displacement sensor 5 at the end of the detection sleeve 4 continuously collects distance data in its respective detection direction and transmits the collected distance data to the control system in real time. When the control system detects that the distance data collected by each non-contact displacement sensor 5 changes from small to large and then back to small within a certain stroke, it determines that the end of the detection sleeve 4 has passed the end face of the pipe hole and entered the pipe hole. After the end of the detection sleeve 4 enters the pipe hole, the control system controls the detection sleeve 4 to stop at multiple preset axial positions. At each stopping position, the control system records the distance data output by each non-contact displacement sensor 5.

[0070] After completing the data acquisition for each axial position, the control system uses the multiple distance data collected by each sensor at the same axial position as multiple constraint points on the axial section. All constraint points are incorporated into the same spatial coordinate system along the axial direction. The constraint point set is fitted by a spatial straight line fitting algorithm to solve for the spatial straight line equation that is best fitted by the constraint point set. This spatial straight line equation is the actual spatial center axis equation of the pipe hole and is stored in the register of the control system as the initial positioning reference.

[0071] During the insertion welding step, the control system reads the initial positioning reference from the register and generates displacement commands for each drive mechanism of the welding execution end 3 based on this initial positioning reference. Each drive mechanism drives the welding execution end 3 to move according to the displacement commands, so that the front end of the welding tool head 8 is aligned with the actual spatial center axis of the pipe hole. The control system continues to drive the welding tool head 8 forward along the axis indicated by the initial positioning reference until the front end of the welding tool head 8 reaches the preset welding start position inside the pipe hole. When the welding tool head 8 reaches the preset welding start position, the control system sends a start command to the hollow shaft rotation drive unit 7, and the hollow shaft rotation drive unit 7 drives the welding tool head 8 to start the rotation welding action.

[0072] In the real-time sensing step, a timer in the control system generates sampling trigger signals at fixed time intervals. Upon each sampling trigger signal, the control system reads the real-time force signal output by the six-dimensional force sensor 6. The control system's data fusion and pose calculation module performs coordinate transformation on the read real-time force signal, converting it from the sensor coordinate system to the borehole center axis coordinate system. In the borehole center axis coordinate system, the force component perpendicular to the center axis is extracted as the radial offset force component.

[0073] In the dynamic compensation step, the data fusion and pose calculation module compares the extracted radial offset force component with a preset force threshold. When the radial offset force component does not exceed the preset force threshold, the control system maintains the current drive parameters unchanged. When the radial offset force component exceeds the preset force threshold, the data fusion and pose calculation module uses this radial offset force component as a correction term to correct the spatial straight line equation of the initial positioning reference. That is, it keeps the direction vector of the spatial straight line unchanged while shifting the position coordinates of the spatial straight line along the direction of the radial offset force component, or it corrects both the position coordinates and direction vector of the spatial straight line simultaneously to obtain the instantaneous compensation axis under the current working condition. The data fusion and pose calculation module compares the current actual pose of the welding tool head 8 with the instantaneous compensation axis, calculates the position deviation of the front end of the welding tool head 8 relative to the instantaneous compensation axis, and generates the pose correction amount of each drive mechanism based on the position deviation. The control system distributes the pose correction amount to each drive mechanism. Each drive mechanism drives the welding execution end 3 to move according to the distributed pose correction amount, so that the front end of the welding tool head 8 moves in the direction of the instantaneous compensation axis until the deviation between the front end of the welding tool head 8 and the instantaneous compensation axis is zero.

[0074] During the cyclic execution process, the control system's timer triggers a dynamic compensation step at each sampling time, ensuring that the real-time pose of the welding tool head 8 is updated and corrected at each sampling time. When the control system detects that the welding length of the current hole position has reached the preset welding depth, the control system sends a stop command to the hollow shaft rotation drive unit 7 and simultaneously sends stop commands to each drive mechanism. The welding of the current hole position is completed, and the control system proceeds to the welding process of the next hole position.

[0075] In step S3, after reading the real-time force signal output by the six-dimensional force sensor 6, the control system first performs low-pass filtering on the real-time force signal to filter out noise components caused by high-frequency vibrations during the welding process. The filtered signal contains DC and AC components, where the DC component corresponds to the constant directional force on the welding tool head 8, which is the projection component of the gravity vector in the sensor coordinate system. The control system extracts the DC component from the filtered signal to obtain the projection values ​​of the gravity vector in the three axes of the six-dimensional force sensor 6 coordinate system.

[0076] The control system reads the position signals fed back by the encoders of the drive motors of each joint of the welding execution end 3 in real time, and substitutes the position signals of each joint into the kinematic forward solution model pre-stored in the control system. The kinematic forward solution model calculates the spatial attitude angle of the flange surface of the welding execution end 3 in the world coordinate system based on the rotation angle value of each joint and the link length parameter. This spatial attitude angle includes the rotation angle about the horizontal axis and the rotation angle about the vertical axis of the world coordinate system. The control system superimposes this spatial attitude angle with the pre-stored installation orientation parameters of the six-dimensional force sensor 6 relative to the flange surface of the welding execution end 3 to obtain the actual spatial attitude angle of the welding tool head 8 at the current moment.

[0077] The control system calculates the direction of the gravity vector in the world coordinate system based on the actual spatial attitude angle of the welding tool head 8 and the pre-stored mass parameters of the welding tool head 8. Since the welding tool head 8 is connected to the output end of the hollow shaft rotary drive unit 7 via a universal joint linkage mechanism, and the axial direction of the output end of the hollow shaft rotary drive unit 7 changes with the attitude of the welding execution end 3, the control system transforms the gravity vector from the world coordinate system to a local coordinate system based on the axis of the ball joint support 9. In this local coordinate system, the control system decomposes the gravity vector into an axial component along the axis of the ball joint support 9 and a radial component perpendicular to the axis of the ball joint support 9, wherein the plane containing the radial component is perpendicular to the axis of the ball joint support 9.

[0078] The control system decomposes the radial component of the gravity vector twice in a plane perpendicular to the axis of the ball joint support 9, projecting each component onto the direction line of each electronically controlled proportional throttling damper 11. Since the electronically controlled proportional throttling dampers 11 are uniformly distributed circumferentially along the ball joint support 9, and the included angle between adjacent dampers is equal, the direction lines of each damper form a set of uniformly distributed direction vectors in a plane perpendicular to the axis. The control system calculates the projection value of the radial component of the gravity vector onto each direction vector; each projection value is the radial gravity component value corresponding to each electronically controlled proportional throttling damper 11.

[0079] The control system generates current control signals for each electrically controlled proportional throttling damper 11 based on the radial component of gravity. For any electrically controlled proportional throttling damper 11, when the corresponding radial component of gravity is oriented in a certain direction, the current control signal output by the control system causes the valve core opening of the electromagnetic proportional valve of that damper to change, thereby applying a damping reaction force opposite to the direction of the gravity component to the spherical convex surface of the ball head rod 10 by the plunger rod of that damper. The damping reaction forces generated by each electrically controlled proportional throttling damper 11 are combined on the spherical convex surface of the ball head rod 10, and the direction of the resultant force is opposite to the direction of the radial component of the gravity vector, while the magnitude of the resultant force is equal to the magnitude of the radial component of the gravity vector. This ensures that the welding tool head 8 maintains its axial direction relative to the ball joint support 9 without deflection in any spatial orientation. The above gravity compensation process is executed synchronously with the extraction of the radial offset force component in step S3 and continues throughout the entire welding process.

[0080] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A gravity heat exchanger tube welding device, comprising a base, a workpiece positioning platform disposed on the base, a welding execution end disposed above the workpiece positioning platform and movable along three orthogonal spatial directions, and a control system respectively connected to the welding execution end and each drive mechanism, characterized in that, The welding execution end integrates: A hollow shaft rotary drive unit, the output end of which is fixedly connected to a welding tool head; A detection sleeve is coaxially sleeved on the outer periphery of the welding tool head. An axial sliding guide structure is provided between the detection sleeve and the welding tool head. The detection sleeve is driven by a first driving element to slide independently axially relative to the welding tool head. At least three non-contact displacement sensors are uniformly embedded in the end of the detection sleeve in the circumferential direction, and the detection direction of each non-contact displacement sensor is parallel to the radial direction of the detection sleeve. A six-dimensional force sensor is fixedly installed at the root of the welding tool head to sense the force vector acting on the welding tool head in its spatial orientation. The control system includes a data fusion and pose calculation module, which is configured to: when the detection sleeve extends and the non-contact displacement sensor is close to the end face of the tube hole of the tube plate to be welded, receive radial distance data of multiple cross sections of the inner wall of the tube hole collected by each of the non-contact displacement sensors, fit the actual spatial center axis equation of the tube hole and use it as the initial positioning reference. While the welding tool head is inserted into the pipe hole along the initial positioning reference to perform welding, the data fusion and pose calculation module continuously receives the real-time force signal fed back by the six-dimensional force sensor. It separates the radial offset force component of the welding tool head from the real-time force signal. When the radial offset force component exceeds a preset force threshold, the data fusion and pose calculation module substitutes the radial offset force component as a correction term into the equation of the actual spatial center axis for secondary calculation to obtain the instantaneous compensation axis under the current working condition. The control system drives the welding execution end to dynamically compensate the real-time pose of the welding tool head according to the instantaneous compensation axis.

2. The gravity heat exchanger tube welding device according to claim 1, characterized in that, The non-contact displacement sensor is a laser triangulation sensor or an eddy current sensor, and each of the non-contact displacement sensors is independently connected to the data acquisition port of the control system.

3. The gravity heat exchanger tube welding device according to claim 1, characterized in that, The welding tool head is connected to the output end of the hollow shaft rotary drive unit via a universal hinge linkage mechanism. The universal joint linkage mechanism includes a ball joint support fixed to the output end of the hollow shaft rotation drive unit, a ball head rod fixedly connected to the root of the welding tool head, and at least four electrically controlled proportional throttling dampers circumferentially embedded between the ball joint support and the ball head rod. The damping coefficient of each electrically controlled proportional throttling damper is independently adjusted by the control system based on the direction and magnitude of the gravity vector fed back by the six-dimensional force sensor.

4. The gravity heat exchanger tube welding device according to claim 3, characterized in that, The control system separates the gravity vector from the real-time force signal of the six-dimensional force sensor, and calculates the component force of the gravity vector in each radial direction according to the current spatial attitude angle of the welding execution end. The control system independently adjusts the damping coefficient of each of the electronically controlled proportional throttling dampers according to the component force value in each radial direction, so that the reaction force applied by each of the electronically controlled proportional throttling dampers to the ball joint is opposite to the direction of the gravity component force in the corresponding radial direction.

5. The gravity heat exchanger tube welding device according to claim 1, characterized in that, The workpiece positioning platform is provided with an annular guide rail, and the welding execution end is slidably engaged with the annular guide rail via a sliding seat. The sliding seat integrates a magnetorheological fluid damping unit, and the damping coefficient of the magnetorheological fluid damping unit is dynamically adjusted by the control system.

6. The gravity heat exchanger tube welding device according to claim 5, characterized in that, The welding device also includes an infrared temperature measuring array fixedly mounted on the workpiece positioning platform. The detection field of the infrared temperature measuring array covers the tube sheet mounting area on the workpiece positioning platform. The control system receives the welding zone temperature field signal fed back by the infrared temperature measuring array and adjusts the damping coefficient of the magnetorheological fluid damping unit according to the temperature field signal.

7. The gravity heat exchanger tube welding device according to claim 1, characterized in that, The workpiece positioning platform is embedded with a distributed fiber optic strain sensor. The signal output end of the distributed fiber optic strain sensor is connected to the signal input end of the control system. The control system generates a full-domain deformation cloud map of the tube sheet based on the tube sheet deformation data fed back by the distributed fiber optic strain sensor, and pre-calculates the center offset of the next hole to be welded based on the deformation cloud map. Before the welding tool head moves to the next hole to be welded, the control system corrects the initial positioning coordinates of the welding execution end based on the center offset.

8. The gravity heat exchanger tube welding device according to claim 1, characterized in that, The data fusion and pose calculation module performs the following operations cyclically at a fixed sampling frequency: receiving the real-time force signal from the six-dimensional force sensor, separating the radial offset force component, comparing with a preset force threshold, calculating the instantaneous compensation axis, and outputting the pose correction amount; When the duration for which the radial offset force component continuously exceeds the preset force threshold exceeds the preset time threshold, the control system issues an alarm signal and stops the welding process at the current hole position.

9. A method for welding gravity heat exchange tubes, using the gravity heat exchange tube welding apparatus as described in any one of claims 1 to 8, characterized in that, Includes the following steps: S1. Initial positioning steps: The control system drives the detection sleeve to extend relative to the welding tool head, so that the non-contact displacement sensor at the end of the detection sleeve is close to the end face of the tube hole of the tube plate to be welded. Each non-contact displacement sensor collects radial distance data of multiple cross sections of the inner wall of the tube hole and feeds it back to the control system. The control system fits the equation of the actual spatial center axis of the tube hole as the initial positioning reference. S2. Insertion welding step: The control system drives the welding tool head to insert into the pipe hole along the initial positioning reference, and starts welding; S3. In-situ real-time sensing step: Throughout the welding process, the control system continuously receives real-time force signals from the six-dimensional force sensor and separates the radial offset force component of the welding tool head from the real-time force signals. S4. Dynamic compensation step: When the radial offset force component exceeds the preset force threshold, the control system substitutes the radial offset force component as a correction term into the equation of the actual spatial center axis for secondary calculation to obtain the instantaneous compensation axis under the current working condition, and drives the welding execution end to dynamically compensate the real-time pose of the welding tool head; the above steps S3 and S4 are executed cyclically at a fixed sampling frequency until the welding of the current hole position is completed.

10. A method for welding gravity heat exchange tubes according to claim 9, characterized in that, In step S3, the control system further separates the gravity vector from the real-time force signal of the six-dimensional force sensor, and calculates the component force of the gravity vector in each radial direction according to the current spatial attitude angle of the welding execution end. The control system independently adjusts the damping coefficient of each electronically controlled proportional throttling damper in the universal joint linkage mechanism according to the component force value in each radial direction, so that the reaction force applied by each electronically controlled proportional throttling damper to the ball joint is opposite to the direction of the gravity component force in the corresponding radial direction.

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