Automatic tightening device and method for large-length-diameter-ratio thin-wall large-thread pipe fitting

Abstract

The invention belongs to the technical field of assembly manufacturing, and discloses a large-length-diameter-ratio thin-wall large-thread pipe fitting automatic tightening device which comprises a truss robot, an automatic screwing-on device, a butt joint platform and a control system, and the control system is in communication connection with the truss robot, the automatic screwing-on device and the butt joint platform. The device is used for controlling the motion trail, adjusting the clamping force, analyzing torque data and optimizing the tightening process. The invention further discloses a using method of the device. According to the invention, thread jamming, radial deformation of the barrel section and the like possibly caused by manual tightening are avoided, and the barrel section tightening quality and efficiency are improved; and finally, automatic tightening of the barrel section is achieved, the consistency of tightening quality and the butt joint efficiency are improved, the labor intensity of workers is reduced, and the safety risk of product collision is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of assembly manufacturing, and relates to an automatic tightening device and method for large aspect ratio thin-walled large-thread pipe fittings. Background Art

[0002] Large-size threaded connections are widely used in fields such as petrochemical industry, aerospace, and military equipment. Among them, tubular parts with an outer diameter to wall thickness ratio greater than 20 are called thin-walled large-thread pipe fittings, which are important barrel sections of multiple products in the aerospace field. In the traditional assembly mode of such products, most of them adopt the assembly method of manually tightening with the help of tooling. Due to the large tightening torque requirement, this method requires multiple people to cooperate to apply a large tightening force, resulting in high labor intensity of personnel, low docking efficiency, and poor tightening consistency.

[0003] With the continuous increase in product supply demand, the manual tightening method can no longer meet the needs of high-efficiency and high-reliability development of products. In order to achieve the automatic assembly of thin-walled large-thread pipe fittings, domestic experts and scholars have proposed a tightening device using a nine-degree-of-freedom robot and a laser ranging module. This device integrates a Stewart six-degree-of-freedom pose adjustment platform and a three-degree-of-freedom series mechanism at the end, and a plurality of micro laser ranging modules are arranged along the circumferential direction on the outer wall of the barrel section for coaxial consistency measurement and pose compensation calculation. Using the compensation control algorithm, the automatic assembly of thin-walled large-thread pipe fittings is basically realized. The above nine-degree-of-freedom tightening device is a cantilever structure in the horizontal direction, and is only suitable for grasping barrel sections with short axial length and light weight. When the ratio of the axial length to the outer diameter of the barrel section exceeds 3, due to the large shift of the center of gravity, a large overturning moment will be generated, which will affect the rigidity and accuracy of the entire device; in addition, when facing a barrel section with a large aspect ratio, the plurality of laser ranging modules arranged in the circumferential direction of the nine-degree-of-freedom tightening device can only complete the measurement of the center position of one cross-section of the barrel section, and cannot measure the entire axis position of the barrel section; and this device does not solve the support problem of the barrel section. When the control program fails, the barrel section cannot be immediately unlocked. If the nine-degree-of-freedom robot swings, it may even cause the barrel section to collide with other surrounding objects, posing a great safety hazard. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies in the prior art, such as insufficient rigidity and accuracy of the tightening device, difficulty in measuring the axis of the barrel section, and lack of support for the barrel section with potential safety hazards, during the butt joint assembly process of large aspect ratio thin-walled large-thread pipe fittings, and provides an automatic tightening device and method for large aspect ratio thin-walled large-thread pipe fittings.

[0005] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0006] An automatic tightening device for large aspect ratio thin-walled large-thread pipe fittings includes a truss robot, an automatic make-up device, a docking platform, and a control system.

[0007] For the column, main cross beam, secondary cross beam, x-axis cross beam, x-axis moving mechanism, y-axis moving mechanism, and z-axis moving mechanism of the truss robot, the x-axis moving mechanism, y-axis moving mechanism, and z-axis moving mechanism are respectively guided by linear guides and driven by gear racks to achieve movement in the x-axis, y-axis, and z-axis directions;

[0008] The automatic make-up device is provided at the lower end of the z-axis of the truss robot through a connection interface, and includes a translation mechanism, a sliding base, a make-up mechanism, a floating mechanism, and a laser distance sensor. The translation mechanism is provided at the lower end of the connection interface and is used to provide an axial pressing force; the sliding base is installed at the lower end of the translation mechanism and is connected with a cylinder; the floating mechanism is connected to the lower end of the sliding base, the make-up mechanism is connected to the floating mechanism through a pin shaft, and a laser distance sensor is installed below the make-up mechanism;

[0009] The docking platform includes a fixed support and an auxiliary support. The fixed support is used to support the fixed cylinder section, and the auxiliary support is a floating support with adjustable height and is used to adjust the axis position of the cylinder section to be tightened;

[0010] The control system is communicatively connected to the truss robot, the automatic make-up device, and the docking platform, and is used to control the movement trajectory, adjust the clamping force, analyze the torque data, and optimize the tightening process.

[0011] As a preferred method, the x-axis moving mechanism of the truss robot is installed at the rear side of the x-axis cross beam, the y-axis moving mechanism is installed at the front side of the x-axis cross beam, and the z-axis moving mechanism is installed on the y-axis.

[0012] As a preferred method, the make-up mechanism includes a housing, a cylinder, a crank connecting rod mechanism, a torque sensor, a servo motor, and a make-up roller. The servo motor drives the make-up roller to rotate, and the make-up roller makes the cylinder section to be tightened rotate through friction to achieve the make-up function. The torque sensor is used for torque detection during the tightening process. The cylinder drives the make-up roller to clamp or release the cylinder section through the crank connecting rod, and the cylinder is connected with a precision pressure reducing valve to adjust the clamping force.

[0013] As a preferred method, the floating mechanism includes an upper end, an outer ring, a middle end, a lower end, and disc springs. The upper end is connected to the sliding base through a pin shaft and disc springs are placed in the middle. The middle end and the lower end are connected by threads, disc springs are placed between the middle end and the inner bottom of the outer ring, the upper end and the outer ring are connected by threads, and disc springs are placed between the upper end and the middle end.

[0014] As a preferred method, the disc springs are elastic and can adaptively float slightly in two directions of the y-axis and z-axis.

[0015] As a preferred method, the auxiliary support of the docking platform is provided with rollers, so that the cylinder section to be tightened can rotate relative to the auxiliary support.

[0016] The present invention also discloses a method for using an automatic tightening device for a thin-walled large-thread pipe fitting with a large length-diameter ratio, which includes the following steps:

[0017] S1. Place the barrel section to be tightened at the left end of the docking platform, and place the fixed barrel section at the right end of the docking platform. The docking platform has been pre-adjusted so that the fixed barrel section and the barrel section to be tightened have a certain coaxiality, and adjust the distance between the fixed barrel section and the barrel section to be tightened;

[0018] S2. Uniformly obtain multiple groups of coordinate data on the surfaces of the barrel section to be tightened and the fixed barrel section through a laser distance sensor, fit the axis equations of the two barrel sections based on the least squares method, and calculate the axis deviation. Adjust the position of the barrel section to be tightened through the docking platform to obtain an accurate clamping position. After determining the clamping position, drive the cylinder of the screwing device to work, open the screwing rollers, and drive the truss robot to reach the clamping point position, and then control the cylinder to clamp the outer shell of the barrel section to be tightened;

[0019] S3. The barrel section to be tightened advances under the drive of the cylinder of the translation device, and the servo motor on the screwing device simultaneously drives the barrel section to be tightened to perform a rotation and screwing operation;

[0020] S4. After all the threads are screwed in, start tightening. A pre-tightening force is generated between the fixed barrel section and the barrel section to be tightened. Under the condition of not exceeding the thread tension limit, apply a tightening torque to ensure the tight connection of the threads of the two.

[0021] As a preferred method, in step S2, the axis deviation between the fixed barrel section and the barrel section to be tightened is calculated by fitting the coordinate data collected by the laser distance sensor based on the least squares method.

[0022] Further preferably, in step S2, the specific steps for fitting the axis based on the least squares method include: constructing a cylindrical axis equation, assuming that the axis direction vector is d=(a, b, c) and passing through the origin O; defining the sum of the squares of the distances from all measurement points to the assumed axis as the error function, and obtaining the cylindrical axis parameters by solving the system of equations with zero partial derivatives; calculating the spatial deviation amount of the axes of the two barrel sections according to the fitting result.

[0023] As a preferred method, step S4 further includes immediately stopping the screwing action and the screwing motor after the tightening action is completed, unlocking the clamping cylinder and opening the screwing rollers at the same time, and the x-axis movement mechanism, y-axis movement mechanism, and z-axis movement mechanism of the truss robot respectively return to their initial positions in sequence, and the screwing rollers return to their normal state and lock the cylinder.

[0024] In the initial stage of tightening of the present invention, kinematic modeling of the device movement and product feature analysis are completed. The tightening work is controlled by the control system, which is the control center of the equipment and is responsible for logical control of the equipment, multi-axis movement control, actuator control, sensor signal acquisition, etc. Taking the initial position of the truss robot as the origin, an assembly coordinate system is established with reference to the directions of the x, y, and z-axis movement mechanisms. The fixed cylinder section and the cylinder section to be tightened are supported, the coordinates of the cylinder section surface are obtained through a laser distance sensor, multiple groups of points on the cylinder section surface are measured using the least squares method, the axis of the cylinder section is obtained by calculation and fitting, and the axis deviation is calculated; the position of the cylinder section to be tightened is adjusted through the docking platform to make the axes of the two cylinder sections coincide, and the tightening work is prepared.

[0025] The rotary buckle device clamps the cylinder section to be tightened, the translation mechanism drives the rotary buckle device to move axially to align with the fixed cylinder section, the motor of the rotary buckle mechanism drives the rotary buckle roller to rotate to complete the tightening, and the floating mechanism and the translation mechanism realize the floating compensation and axial compensation during the tightening process. The control system controls the rotation speed and direction of the motor, the torque sensor is used for real-time torque detection, the control system obtains the measured value and conducts analysis of the diameter-thickness ratio of the cylinder section and air pressure adjustment of the cylinder, and optimizes the tightening process. When the torque set value is less than the measured value, the rotary buckle action is executed. If the torque set value is greater than the measured value, the control system controls the rotary buckle device to immediately stop the rotary buckle movement. The data generated during the tightening process is uploaded to the product tightening process database and can be directly scheduled and used during the docking of the cylinder sections.

[0026] The present invention has the following advantages:

[0027] 1. The large-range movement function of the automatic buckling device is realized through the truss robot, which is convenient for the laser distance sensor to measure the surface point data of the two cylinder sections and is suitable for the working conditions of measuring cylinder sections with a large length-diameter ratio. An explosion-proof electric control cabinet is provided for power distribution control, explosion protection, etc. The entire device is controlled by the control system and completes the clamping and tightening work through the execution program, realizing closed-loop control of clamping force, torque, etc.

[0028] 2. In the automatic buckling device of the present invention, the translation mechanism can provide the pressing force in the X direction for thread tightening, which is more conducive to the thread screwing in; the rotary buckle mechanism can clamp the cylinder section to be tightened to provide the friction force required for tightening and drive the roller to realize thread tightening. The present invention does not require manual handling and force application for tightening the cylinder section to be tightened, greatly improving the automation degree of tightening of thin-walled large threads.

[0029] 3. In the present invention, the axis of the cylinder section is measured through the laser distance sensor to accurately obtain the clamping position of the cylinder section; the adaptive micro-floating is realized through the floating mechanism; the position of the cylinder section to be tightened is adjusted through the docking platform to ensure the centering during the tightening process; and the over-tightening of the cylinder section is avoided through the torque sensor and the consistency of the tightening torque is ensured, etc.

[0030] The present invention avoids problems such as thread jamming and radial deformation of the cylinder section that may occur during manual tightening, and improves the quality and efficiency of tightening the cylinder section.

[0031] The support problem of the cylinder section is solved through platform support, and the clamping force is controlled by air pressure to meet the tightening and docking of cylinder sections with different outer dimensions and wall thicknesses; a method for measuring and fitting the axis of the cylinder section based on the least squares method is proposed, and it guides the docking platform to adjust the posture of the cylinder section axis. Combined with tightening process optimization, floating compensation, etc., the automatic tightening of the cylinder section is finally realized, improving the consistency of tightening quality and docking efficiency, reducing the labor intensity of personnel, and reducing the safety risk of product collision. Brief Description of the Drawings

[0032] Figure 1 It is a schematic diagram of the working process of the present invention;

[0033] Figure 2 It is a schematic diagram of the device structure of the present invention;

[0034] Figure 3 It is a schematic diagram of the structure of the truss robot;

[0035] Figure 4 It is a schematic diagram of the x-axis motion mechanism;

[0036] Figure 5 It is a schematic diagram of the y-axis motion mechanism and the z-axis motion mechanism;

[0037] Figure 6 It is a schematic diagram of the automatic make-up device;

[0038] Figure 7 It is a schematic diagram of the connection of the automatic make-up device;

[0039] Figure 8 It is a schematic diagram of the thread spinning mechanism;

[0040] Figure 9 It is a schematic diagram of the principle of the crank and connecting rod mechanism;

[0041] Figure 10 It is a schematic cross-sectional view of the floating mechanism;

[0042] Figure 11 It is a schematic diagram of the measurement of the product axis;

[0043] Figure 12 It is a schematic diagram of the docking platform;

[0044] Figure 13 It is a schematic diagram of the docking state. Detailed Embodiment

[0045] The present invention will be described in detail below with reference to the accompanying drawings.

[0046] In order to make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0047] Embodiment 1:

[0048] An automatic tightening device for a thin-walled large-thread pipe fitting with a large length-diameter ratio, as Figure 2 shown, includes a truss robot 1, an automatic make-up device 2, a docking platform 3, and a control system. The truss robot 1 realizes the movement of the spatial position of the cylinder section; the automatic make-up device 2 realizes the functions of clamping and tightening the cylinder section. The docking platform 3 supports the cylinder section 4, including the cylinder section 41 to be tightened and the fixed cylinder section 42, to ensure good centering during the tightening process. In addition, there is an explosion-proof electric control cabinet for power distribution control, explosion protection, etc., which is not shown in the figure. The entire device is controlled by the control system and completes the clamping and tightening work through an execution program to achieve closed-loop control of the clamping force, torque, etc.

[0049] The structure of the truss robot is as Figure 3 shown, and includes a column 11, a main cross beam 12, a secondary cross beam 13, an x-axis cross beam 14, an x-axis motion mechanism 15, a y-axis motion mechanism 16, and a z-axis motion mechanism 17. The x-axis motion mechanism 15, the y-axis motion mechanism 16, and the z-axis motion mechanism 17 are all guided by linear guides and driven by gear racks; the guides and racks are fixed on the truss robot. When the motors of each axis rotate, they drive the gears to move, enabling the movement of each axis. The components of the x-axis motion mechanism are installed on the rear side of the x-axis cross beam, the components of the y-axis motion mechanism are installed on the front side of the x-axis cross beam, and the components of the z-axis motion mechanism are installed on the y-axis, generally realizing the movement in the x, y, and z directions.

[0050] The automatic make-up device is as Figure 6 shown. The automatic tightening device includes a connection interface 21, a translation mechanism 22, a sliding base 23, a floating mechanism 24, a screwing mechanism 25, and a laser distance sensor 26. Refer to Figure 7, the connection interface of the automatic make-up device is fixedly connected to the lower end of the z-axis. The translation mechanism is fixedly connected to the lower end of the connection interface, and the sliding base is installed at the lower end of the translation mechanism and is connected to a cylinder. When the cylinder is not working, the translation mechanism can move relative to the sliding base. The floating mechanism is connected to the lower end of the sliding base, and the make-up mechanism is connected to the floating mechanism through a pin shaft. Two laser distance sensors are installed below the make-up mechanism. The truss robot moves the make-up mechanism. First, the axes of the two cylinder sections are measured by the laser distance sensors. The position of the cylinder section to be tightened is adjusted through the docking platform to make the axes of the two cylinder sections coincide, obtaining the clamping position of the cylinder section to be tightened, and it is clamped by the make-up device. The cylinder is connected to the air source, and the translation mechanism drives the make-up mechanism and the cylinder section to be tightened to move in the x-axis direction, providing a pressing force for thread tightening. Finally, the make-up mechanism rotates to tighten the cylinder section to be tightened. During the tightening process, the cylinder does not work, and the translation mechanism and the sliding base can move relative to each other. As the thread is screwed in, the make-up mechanism can move along with the cylinder section to be tightened.

[0051] The schematic diagram of the make-up mechanism is as shown in Figure 8 shown, and it includes a housing 251, a cylinder 252, a crank-link mechanism 253, a torque sensor 254, a servo motor 255, and a make-up roller 256. The cylinder is externally connected to the air source. When the cylinder extends, it drives the upper ends of the left and right connecting rods to open to both sides. The left and right rods move around the center point, driving the rollers to move towards the center, thereby clamping the cylinder section. The distance that the rollers move towards the center is not a fixed value, and the applicable pipe diameter range can be finely adjusted. Then the servo motor rotates to drive the rollers to rotate, and the rollers make the cylinder section to be tightened rotate through friction, realizing the make-up function. Tightening is driven by a servo motor, and the tightening speed is adjustable. The control system controls the rotation of the servo motor. By adjusting its rotation direction and speed, problems such as thread jamming and over-tightening are prevented, and the tightening process is optimized. A precision pressure reducing valve is installed on the cylinder to adjust the air pressure to control the driving force of the cylinder, and thus control the clamping force. The torque sensor is used for torque detection during the tightening process. The measured value of the torque sensor is compared with the set torque value. If it exceeds the set value, an alarm is given and the make-up stops rotating.

[0052] The schematic diagram of the crank-link mechanism is as shown in Figure 9 shown. Under the constraint of the internal structure of the make-up mechanism housing, the four make-up rollers can only move in the horizontal direction, and the middle connecting rod moves in the vertical direction. When the cylinder extends, the make-up rollers move horizontally towards the center, realizing the clamping movement of the make-up rollers.

[0053] As shown in Figure 10As shown in the figure, the floating mechanism includes the upper end 241 of the floating mechanism, the outer ring 242, the middle end 243, the lower end 244, and the disc spring 245. The upper end is connected to the sliding base through a pin shaft, and multiple disc springs are placed in the middle. The middle end and the lower end are connected by threads. Multiple disc springs are placed between the middle end and the inner bottom of the outer ring. The upper end is connected to the outer ring by threads, and multiple disc springs are placed between the inside of the upper end and the middle end. The disc spring has elasticity and can adaptively float slightly in the two directions of the y-axis and the z-axis, preventing the phenomenon of thread jamming between the barrel section to be tightened and the fixed barrel section during the tightening process.

[0054] The schematic diagram of the product axis measurement is as Figure 11 shown. The method for measuring the axis is as follows:

[0055] The truss robot drives the make-up device to move, and multiple groups of point coordinates are obtained evenly distributed on the surface of the barrel section through the laser distance sensor.

[0056] Assume that the direction vector of the cylindrical axis is d = (a, b, c) and it passes through the origin O.

[0057] Construct the objective function: the sum of the squares of the distances from all measurement points to the assumed axis.

[0058] Solve for a, b, c by the least squares method to make the objective function the minimum value. The equation of the cylindrical axis is:

[0059]

[0060] where (x0, y0, z0) is a point on the axis and (a, b, c) is the direction vector of the axis

[0061] The distance from any point (x i , y i , z i ) on the cylindrical surface to the axis:

[0062]

[0063] Define the error function:

[0064]

[0065] where R is the radius of the barrel section and n is the number of points obtained by the laser distance sensor

[0066] Then minimize the error function, take the partial derivatives of each parameter in the function, and set them equal to 0 to obtain a set of equations.

[0067]

[0068] The position and direction of the cylinder axis can be obtained by solving, and finally the cylinder axis is drawn according to the obtained parameters. The axes of the fixed cylinder section and the cylinder section to be tightened are obtained by the above method, the deviation between the two is calculated, and the measurement accuracy is evaluated. The position of the cylinder section to be tightened is adjusted through the docking platform to make it coincide with the axis of the fixed cylinder section, facilitating the subsequent tightening operation to proceed smoothly.

[0069] The docking platform is as Figure 12 shown, including an auxiliary support 31 and a fixed support 32. The auxiliary support 31 supports the cylinder section 41 to be tightened, and the fixed support 32 supports the fixed cylinder section 42. The auxiliary support belongs to a floating support and has a fine floating function, which can eliminate the jumping of the cylinder section 41 to be tightened in the Z direction during the spiral tightening process, and its height can be adjusted to realize the posture adjustment of the cylinder section to be tightened so that its axis coincides with that of the fixed cylinder section. It is equipped with rollers 43, and the cylinder section to be tightened can rotate on the auxiliary support to realize the buckling of the floating tightening method.

[0070] Embodiment 2:

[0071] The usage method of the device in Embodiment 1 includes the following steps:

[0072] 1. Place the cylinder section to be tightened at the left end of the docking platform, and place the fixed cylinder section at the right end of the docking platform. The docking platform is pre-adjusted so that the fixed cylinder section and the cylinder section to be tightened have a certain coaxiality. Adjust the distance between the fixed cylinder section and the cylinder section to be tightened.

[0073] 2. Measure the axis positions of the two cylinder sections through a laser distance sensor, adjust the position of the cylinder section to be tightened through the docking platform to obtain an accurate clamping position. After determining the clamping position, drive the cylinder of the screw buckling device to work, open the screw buckling rollers, and drive the truss robot to reach the clamping point position, and then control the cylinder to clamp the shell of the cylinder section to be tightened by the screw buckling mechanism.

[0074] 3. The cylinder section to be tightened advances under the drive of the cylinder of the translation device, and this cylinder provides the pre-tightening force at the initial stage of thread tightening. The four servo motors on the screw buckling device move synchronously to drive the cylinder section to be tightened to perform a rotational buckling motion. At the buckling stage, the screw buckling device provides a lower torque to overcome the equivalent frictional torque generated by the thread connection to realize the buckling of the fixed cylinder section and the cylinder section to be tightened. During the buckling process, if the fixed cylinder section and the cylinder section to be tightened are misaligned and the torque sensor measures an abnormal increase in the torque value, the control system gives feedback and stops the tightening operation.

[0075] 4. After all the threads are screwed in, start tightening. At this time, a pre-tightening force is generated between the fixed cylinder section and the cylinder section to be tightened to ensure the tightness of the connection. Under the condition of not exceeding the thread tension limit, apply an appropriate tightening torque to ensure the tight connection of the two threads.

[0076] 5. Immediately stop the make-up operation and the make-up motor after the tightening action is completed. At the same time, unlock the clamping cylinder and open the make-up roller. Then, the z-axis, y-axis, and x-axis of the truss robot return to their initial positions in sequence, and the make-up roller returns to its normal state and locks the cylinder.

[0077] The present invention is not limited to the foregoing specific embodiments. The present invention extends to any new feature or any new combination disclosed in this specification, as well as any new combination of steps of any new method or process disclosed.

Claims

1. An automatic tightening device for thin-walled and large-threaded pipe fittings with a large aspect ratio, characterized in that: Including truss robot, automatic buckle device, docking platform, control system, The truss robot column, main beam, auxiliary beam, x-axis beam, x-axis motion mechanism, y-axis motion mechanism, and z-axis motion mechanism are respectively guided by linear guides and driven by gear racks to achieve motion in the x-axis, y-axis, and z-axis directions; The automatic buckle device is arranged at the lower end of the z-axis of the truss robot through a connection interface, and includes a translation mechanism, a sliding base, a screw-down mechanism, a floating mechanism and a laser ranging sensor. The translation mechanism is arranged at the lower end of the connection interface to provide an axial clamping force; the sliding base is installed at the lower end of the translation mechanism and is connected to a cylinder; the floating mechanism is connected to the lower end of the sliding base, the screw-down mechanism is connected to the floating mechanism through a pin shaft, and a laser ranging sensor is installed below the screw-down mechanism; The docking platform includes a fixed support and an auxiliary support, wherein the fixed support is used to support the fixed barrel section, and the auxiliary support is a height-adjustable floating support used to adjust the axial position of the barrel section to be tightened; The control system serves as the control center of the entire device, and is communicated with the truss robot, the automatic buckle device and the docking platform, and is used for strong power control, parameter setting, collecting feedback data, controlling motion trajectory, adjusting clamping force, analyzing torque data and optimizing tightening process.

2. The automatic tightening device for thin-walled and large-threaded pipe fittings with a large aspect ratio according to claim 1, characterized in that: The x-axis motion mechanism of the truss robot is installed on the rear side of the x-axis beam, the y-axis motion mechanism is installed on the front side of the x-axis beam, and the z-axis motion mechanism is installed on the y-axis.

3. The automatic tightening device for thin-walled and large-threaded pipe fittings with a large aspect ratio according to claim 1 is characterized in that: The spin buckle mechanism includes a shell, a cylinder, a crank-connecting rod mechanism, a torque sensor, a servo motor, and a spin buckle roller. The servo motor drives the spin buckle roller to rotate, and the spin buckle roller rotates the barrel section to be tightened through friction force to achieve the tightening function. The torque sensor is used for torque detection during the tightening process. The cylinder drives the spin buckle roller to clamp or loosen the barrel section through the crank-connecting rod, and the cylinder is connected to a precision pressure reducing valve to adjust the clamping force.

4. The automatic tightening device for thin-walled and large-threaded pipe fittings with a large aspect ratio according to claim 1 is characterized in that: The floating mechanism includes an upper end, an outer ring, a middle end, a lower end, and a disc spring. The upper end is connected to a sliding base through a pin shaft and a disc spring is placed in the middle. The middle end and the lower end are connected by threads. The middle end and the inner bottom of the outer ring are placed with a disc spring. The upper end and the outer ring are connected by threads, and a disc spring is placed between the upper end and the middle end.

5. The automatic tightening device for thin-walled and large-threaded pipe fittings with a large aspect ratio according to claim 4, characterized in that: The disc spring is elastic and can adaptively perform slight floating in the two directions of the y-axis and the z-axis.

6. The automatic tightening device for thin-walled and large-threaded pipe fittings with a large aspect ratio according to claim 1, characterized in that: The auxiliary support of the docking platform is provided with a roller, so that the barrel section to be tightened can rotate relative to the auxiliary support; a floating spring is provided under the roller to eliminate the slight jumping of the barrel section in the Z direction during the tightening process; the auxiliary support has a lifting function, which is convenient for adjusting the axis height of the barrel section.

7. A method for using the automatic tightening device for thin-walled and large-threaded pipe fittings with a large aspect ratio according to any one of claims 1 to 6, characterized in that: The steps include: S1. Place the barrel section to be tightened on the left end of the docking platform, and the fixed barrel section on the right end of the docking platform. The docking platform is pre-adjusted so that the fixed barrel section and the barrel section to be tightened have a certain coaxiality, and adjust the distance between the fixed barrel section and the barrel section to be tightened; S2. Use a laser rangefinder to uniformly obtain multiple sets of coordinate data on the surface of the barrel section to be tightened and the fixed barrel section, obtain the axis equations of the two barrel sections based on the least squares method, and calculate the axis deviation. Adjust the position of the barrel section to be tightened through the docking platform to obtain an accurate clamping position. After determining the clamping position, drive the cylinder of the spin buckle device to work, open the spin buckle roller, and drive the truss robot to the clamping point position, and then control the cylinder to make the spin buckle mechanism clamp the outer shell of the barrel section to be tightened; S3, the barrel section to be tightened moves forward under the drive of the cylinder of the translation device, and the servo motor on the screw-on device drives the barrel section to be tightened to perform a rotation and screw-on motion at the same time; S4. After all the threads are screwed in, start tightening. A pre-tightening force is generated between the fixed barrel section and the barrel section to be tightened. Under the condition that the thread tension limit is not exceeded, the tightening torque is applied to ensure that the threads of the two are tightly connected.

8. The method of use according to claim 7, characterized in that: In step S2, the coordinate data collected by the laser ranging sensor is fitted by the least square method to calculate the axis deviation between the fixed barrel section and the barrel section to be tightened.

9. The method of use according to claim 8, characterized in that: In step S2, the specific steps of fitting the axis based on the least squares method include: constructing the cylindrical axis equation, assuming that the axis direction vector is d=(a, b, c) and passes through the origin O; defining the sum of the squares of the distances from all measurement points to the assumed axis as the error function, and obtaining the cylindrical axis parameters by solving a set of equations with zero partial derivatives; and calculating the spatial deviation of the axes of the two barrel sections based on the fitting results.

10. The method of use according to claim 7, characterized in that: The step S4 also includes that after the tightening action is completed, the screwing action is stopped immediately, the screwing motor stops moving, and at the same time the clamping cylinder is unlocked and the screwing roller is opened, the x-axis motion mechanism, the y-axis motion mechanism, and the z-axis motion mechanism of the truss robot are respectively returned to their initial positions in sequence, the screwing roller returns to normal and the cylinder is locked.

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