A fastening device for polishing stainless steel pipe and a method thereof

Abstract

The present application relates to the field of mechanical processing and metal pipe surface treatment equipment, in particular to a fastening device for polishing and grinding of stainless steel pipes and a method thereof; the device comprises a base, a hollow drive shaft, a servo motor, a rotary cylinder, a push-pull rod, a conical expansion block, an arc-shaped support block and a disc spring set; the device drives the hollow shaft to rotate through the servo motor, drives the conical expansion block to move axially through the cylinder and the push-pull rod, forces the arc-shaped support block to expand radially and tighten the inner wall of the pipe, and maintains the tension pre-tightening through the spring set; the core is to construct a clamping and driving coaxial integrated structure, and to dynamically increase the basic pull-back pressure based on the step torque and angular acceleration inversion friction coefficient in the no-load stage; the present application overcomes the transmission lag and eccentric clamping caused by the traditional separation of clamping and driving, effectively deals with the changes of the interface friction caused by dust adhesion and wear, avoids the driving deficiency or clamping overload, and significantly improves the transmission and clamping stability of the device.

Description

Technical Field

[0001] This invention relates to the field of machining and metal pipe surface treatment equipment, specifically a fastening device and method for polishing and grinding stainless steel pipes. Background Technology

[0002] Existing pipe clamping and rotary drive solutions generally employ a mechanical structure where the clamping and rotary drive components are separate, applying a fixed normal clamping force and adjusting it by monitoring spindle speed feedback. Because clamping and drive are separated, transmission lag and eccentric clamping are prone to occur. For thick-walled alloy steel pipes with high self-weight and high rotational inertia, traditional single-end cantilever clamping easily generates gravitational deflection, leading to excessive straightness deviations in pipe processing. Simultaneously, polishing contact loads exhibit abrupt changes, and the interface friction coefficient changes in real time due to dust, wear, and temperature rise. A fixed clamping force is difficult to match dynamic friction requirements, easily leading to insufficient drive force or clamping overload. Furthermore, pure speed feedback adjustment is slow, and existing processes do not consider the heat accumulation and material load-bearing capacity degradation caused by continuous grinding, easily triggering localized plastic deformation of the pipe. Therefore, a method is needed that can adaptively adjust the clamping force in real time based on dynamic friction states, abrupt changes in cutting load, and thermal decay phenomena to improve transmission stability and prevent pipe deformation. Summary of the Invention

[0003] This invention provides a fastening device and method for polishing and grinding stainless steel pipes. Addressing the issues of straightness deviations caused by the weight of thick-walled pipes and clamping misalignment due to sudden load changes and heat accumulation, this invention ensures machining straightness through double-end coaxial support and adaptively adjusts the clamping force in real time based on dynamic friction and thermal decay to achieve yield protection. To solve the above technical problems, the technical solution of this invention is as follows: A fastening device for polishing and grinding stainless steel pipes includes: Base; first bearing housing, rigidly fixed to the base; hollow drive shaft, supported in the inner hole of the first bearing housing, with radial guide grooves machined on its outer wall; A servo motor is mounted on the base, and its output end is connected to the hollow drive shaft to provide rotational driving force; a rotary cylinder is fixed on the base, and its piston rod is connected to a push-pull rod; A push-pull rod coaxially passes through the internal hollow channel of the hollow drive shaft, and its end away from the rotary cylinder is connected to a conical expansion block; a tailstock synchronous clamping mechanism is set at the end of the base away from the first bearing seat, and the tailstock synchronous clamping mechanism is configured to cooperate with the hollow drive shaft to form a double-end coaxial support to constrain the self-weight deflection of the thick-walled alloy steel pipe and maintain the machining straightness; A conical expansion block has an outer conical surface machined on its outer surface; an arc-shaped support block is slidably installed in the radial guide groove, and its inner side has an inner conical surface machined to match the outer conical surface. A disc spring assembly is fitted onto the outside of the push-pull rod and is used to release preload when the rotary cylinder exhausts and unloads. Both ends of the disc spring assembly abut against the push-pull rod and the hollow drive shaft respectively to form a preload fit.

[0004] In some embodiments, the radial guide grooves are evenly distributed along the circumferential direction, and the arc-shaped support blocks are embedded in the corresponding radial guide grooves; wherein, the outer side of the arc-shaped support block is covered with a polyurethane friction layer; the polyurethane friction layer is fixed to the outer periphery of the arc-shaped support block and is used to provide heavy-load rigidity transmission and shear resistance when bearing the heavy cutting resistance torque of thick-walled tubes.

[0005] In some embodiments, a reduced-diameter shoulder step is machined in the inner hole of the hollow drive shaft, and a limit nut is fixed on the push-pull rod; wherein, one end of the disc spring assembly abuts against the shoulder step, and the other end of the disc spring assembly abuts against the limit nut.

[0006] In some embodiments, the servo motor is connected to the input end of the hollow drive shaft via a quincunx flexible coupling; wherein the hollow drive shaft is axially and radially positioned by back-to-back angular contact ball bearings.

[0007] In some embodiments, the taper of both the outer conical surface and the inner conical surface is 15°; wherein, the end of the push-pull rod is machined with an external thread, and the conical expansion block is screwed and fixed to the external thread through a central threaded hole.

[0008] In some embodiments, the device further includes: a photoelectric encoder connected to the hollow drive shaft; wherein the photoelectric encoder is used to record the rotational state of the hollow drive shaft and output a position signal; and an industrial control computer communicatively connected to the photoelectric encoder, the servo motor, and the rotary cylinder; wherein the industrial control computer is configured to calculate angular acceleration based on the rotational state and dynamically control the air pressure of the rotary cylinder and the rotational speed of the servo motor.

[0009] A method for controlling a fastening device for polishing and grinding stainless steel pipes includes the following steps performed sequentially: S1. Friction State Inversion Stage: During the no-load rotation process, the servo motor is controlled to output a step torque, driving the hollow drive shaft to accelerate the rotation of the stainless steel tube; the rotational speed data is recorded and the angular acceleration is calculated; based on the preset total system moment of inertia, the step torque, and the angular acceleration, the resistance torque caused by friction transmission loss is separated; based on the preset initial normal tension force determined by the preload released by the disc spring assembly and the basic pull-back pressure of the rotary cylinder, the friction coefficient is inverted and calculated; if the friction coefficient is less than the preset friction coefficient threshold, the rotary cylinder is controlled to increase the basic pull-back pressure; if the friction coefficient is greater than or equal to the preset friction coefficient threshold, the basic pull-back pressure is kept unchanged; and the adjusted normal tension force or the unchanged preset initial normal tension force is used as the current normal tension force. S2, Load Sudden Change Feedforward Compensation Stage: During the polishing and grinding process, the negative sudden change value of the angular acceleration of the hollow drive shaft is monitored in real time; when the decrease in angular acceleration exceeds the preset negative critical lower limit, the negative sudden change value is obtained based on the difference exceeding the negative critical lower limit, and the required normal tension force is determined based on the negative sudden change value, the preset total rotational inertia of the system, the preset inner radius of the stainless steel tube to be processed, and the friction coefficient; the rotary cylinder is controlled to increase the pull-back force on the push-pull rod according to the required normal tension force; S3, Adaptive Stage for Preventing Yield Fading: During continuous grinding, the real-time current feedback value of the servo motor driver is read and combined with a preset torque constant, which is the inherent torque proportional coefficient of the servo motor and is determined by the motor's factory calibration parameters; the current cutting resistance torque is obtained, and the instantaneous cutting power is obtained based on the current cutting resistance torque and the angular velocity of the hollow drive shaft, and the heat accumulation state of the stainless steel tube is obtained based on the processing time and the instantaneous cutting power; the preset maximum allowable tensile force threshold is dynamically lowered according to the heat accumulation state to obtain the lowered maximum allowable tensile force threshold; when the required normal tension force is greater than the lowered maximum allowable tensile force threshold, the increase in the tension of the rotary cylinder is limited, and the speed of the servo motor is actively reduced by issuing a speed command; when the required normal tension force is less than or equal to the lowered maximum allowable tensile force threshold, the rotary cylinder is controlled to output the required normal tension force.

[0010] In some implementations, the logic for separating the resistance torque in step S1 is as follows: it is obtained based on the step torque, the preset total system moment of inertia, and the angular acceleration; wherein, the logic for inverting and calculating the friction coefficient is as follows: it is obtained based on the resistance torque, the preset inner radius, and the preset initial normal tension force.

[0011] In some embodiments, in step S2, the logic for calculating the increment of the normal tensioning force is as follows: based on the increase in the instantaneous cutting resistance torque, the preset inner radius, and the friction coefficient; wherein, the logic for calculating the required normal tensioning force is as follows: based on the current normal tensioning force and the increment of the normal tensioning force; wherein, the pull-back force increased by the rotary cylinder is mechanically amplified through the outer conical surface of the conical expansion block.

[0012] In some implementations, in step S3, the command to actively reduce the speed of the servo motor is configured to be implemented by reducing the cutting line speed.

[0013] The present invention has the following beneficial effects: 1. This invention directly drives a hollow drive shaft with a servo motor, which, in conjunction with a push-pull rod and a tapered expansion block inserted therein, drives an arc-shaped support block to slide along a radial guide groove. This overcomes the transmission lag and eccentric clamping problems caused by the separation of clamping and driving. At the same time, during the no-load stage, the friction coefficient is inverted based on the step torque and angular acceleration, and the base pull-back pressure is dynamically adjusted upwards. This effectively addresses the changes in interface friction caused by dust adhesion and wear, avoids insufficient driving or clamping overload caused by fixed clamping force, and significantly improves the transmission and clamping stability of the device. 2. This invention uses an industrial control computer to monitor the negative abrupt change in angular acceleration in real time, calculates the increase in cutting resistance torque using feedforward, and directly compensates for the normal clamping force, thus solving the problems of slow adjustment and difficulty in coping with sudden changes in polishing load caused by pure speed feedback. In addition, it obtains the heat accumulation state of the stainless steel tube by calculating the instantaneous cutting power through integration, and dynamically lowers the maximum allowable tensile force threshold accordingly. When the limit is exceeded, it actively limits the cylinder tensile force and reduces the motor speed command, effectively preventing the material bearing capacity decay and local plastic deformation caused by continuous grinding, and achieving reliable anti-yield protection. 3. This invention effectively controls the surface thermal stress input during polishing and grinding by combining an industrial control computer with dynamic pressure limiting and speed reduction based on heat accumulation, suppressing the generation of residual tensile stress and significantly improving the fatigue life of pipe fittings under deep-sea alternating load conditions. At the same time, the polyurethane friction layer covered by the arc-shaped support block has excellent resistance to chloride ion corrosion and salt spray, improving the long-term service reliability of the fastening device in the high humidity and high salt spray heavy industrial environment of the ocean. Attached Figure Description

[0014] The following drawings, illustrating embodiments of this application, are incorporated herein by reference and are used to understand this application. The drawings illustrate embodiments of this application and their descriptions, serving to explain the principles of this application. In the drawings, Figure 1 This is a schematic diagram of the overall external structure of the device; Figure 2 This is a schematic diagram of the external structure of the hollow drive shaft; Figure 3 This is a cross-sectional structural diagram of the hollow drive shaft; Figure 4 This is a flowchart of the method of the present invention.

[0015] In the diagram: 1. Base; 2. First bearing housing; 3. Hollow drive shaft; 4. Radial guide groove; 5. Servo motor; 6. Rotary cylinder; 7. Push-pull rod; 8. Conical expansion block; 9. Outer conical surface; 10. Arc-shaped support block; 11. Inner conical surface; 12. Disc spring assembly; 13. Polyurethane friction layer; 14. Annular groove; 15. Annular tension spring; 16. Shoulder step; 17. Limit nut; 18. Plum blossom-shaped elastic coupling; 19. Angular contact ball bearing; 20. External thread; 21. Central threaded hole. Detailed Implementation

[0016] In the following description, numerous specific details are set forth to provide a more thorough understanding of this application. However, it will be apparent to those skilled in the art that embodiments of this application may be practiced without one or more of these details. In other instances, certain technical features well-known in the art have not been described to avoid confusion with embodiments of this application.

[0017] Combination Figure 1 A fastening device for polishing and grinding stainless steel pipes, comprising: Base 1; First bearing seat 2, rigidly fixed to base 1; Hollow drive shaft 3, supported in the inner hole of first bearing seat 2, with radial guide groove 4 machined on its outer wall; Servo motor 5 is mounted on base 1, and its output end is connected to hollow drive shaft 3 to provide rotational driving force; A rotary cylinder 6 is fixed on the base 1, and its piston rod is connected to a push-pull rod 7. The push-pull rod 7 coaxially passes through the internal hollow channel of the hollow drive shaft 3, and its end away from the rotary cylinder 6 is connected to a conical expansion block 8. A tailstock synchronous clamping mechanism is set at the end of the base 1 away from the first bearing seat 2. The tailstock synchronous clamping mechanism is configured to cooperate with the hollow drive shaft 3 to form a double-end coaxial support to constrain the self-weight deflection of the thick-walled alloy steel pipe and maintain the machining straightness. The conical expansion block 8 has an outer conical surface 9 machined on its outer surface; The arc-shaped support block 10 is slidably installed in the radial guide groove 4, and its inner side is machined with an inner conical surface 11 that matches the outer conical surface 9; The disc spring assembly 12 is fitted outside the push-pull rod 7 and is used to release the preload when the rotary cylinder 6 exhausts and unloads. Its two ends abut against the push-pull rod 7 and the hollow drive shaft 3 respectively to form a preload fit. In this embodiment, the base 1 is set as the mounting base for supporting each actuator and force transmission component, and is used to maintain the consistency between the rotation axis and the clamping axis, and reduce the additional wobble of the stainless steel tube during the polishing process; after the first bearing seat 2 is fixed to the base 1, it provides a support boundary for the hollow drive shaft 3, so that the hollow drive shaft 3 maintains the set rotation accuracy when subjected to polishing resistance torque and radial disturbance. The hollow drive shaft 3 has a hollow structure with an internal hollow channel through which the push-pull rod 7 passes. The outer wall forms a radial guide groove 4, which limits the arc-shaped support block 10 to only move radially, thereby stably converting the axial displacement of the conical expansion block 8 into the radial expansion displacement of the arc-shaped support block 10. After the servo motor 5 is connected to the hollow drive shaft 3, it outputs a rotational driving force, causing the stretched stainless steel tube to rotate synchronously with the hollow drive shaft 3, thus solving the transmission lag problem caused by the separation of the clamping component and the rotational driving component in the existing structure. After the piston rod of the rotary cylinder 6 is connected to the push-pull rod 7, it can apply an adjustable axial pull force to the push-pull rod 7. The push-pull rod 7 transmits this axial pull force to the conical expansion block 8. The conical expansion block 8 then converts the axial force into a radial clamping force through the cooperation between the outer conical surface 9 and the inner conical surface 11 of the arc-shaped support block 10. After the arc-shaped support block 10 contacts the inner wall of the stainless steel tube, it forms a normal clamping force. This normal clamping force is used to establish the friction driving torque and to suppress the local vibration of the stainless steel tube under the polishing load. The disc spring assembly 12 is fitted outside the push-pull rod 7. As a mechanical energy storage unit independent of the external air source, it continues to push the push-pull rod 7 to maintain the tension of the conical expansion block 8 when the rotary cylinder 6 is in the exhaust unloading state, so that the arc-shaped support block 10 maintains the basic support force. Thus, the device forms a clamping structure that combines pneumatic adjustment and mechanical pressure holding. It forms a continuous force transmission chain between rotation drive, clamping establishment and pressure loss holding, which can maintain the stable clamping of the stainless steel tube under the conditions of friction coefficient fluctuation and cutting resistance change.

[0018] Combination Figure 2 Radial guide grooves 4 are evenly distributed along the circumference, and arc-shaped support blocks 10 are embedded in the corresponding radial guide grooves 4; wherein, the outer side of the arc-shaped support block 10 is covered with a polyurethane friction layer 13; the polyurethane friction layer 13 is fixed to the outer periphery of the arc-shaped support block 10, and is used to provide heavy load rigidity transmission and shear resistance when bearing the heavy cutting resistance torque of thick-walled pipe.

[0019] In this embodiment, the radial guide grooves 4 are evenly distributed along the circumference of the hollow drive shaft 3, so that multiple arc-shaped support blocks 10 form a circumferentially symmetrical support relationship around the central axis. This uniformly distributed structure is used to reduce the eccentric clamping caused by unilateral force, so that the inner wall of the stainless steel tube obtains a uniformly distributed normal pressure. After the arc-shaped support block 10 is embedded in the corresponding radial guide groove 4, its movement trajectory is limited to reciprocating movement in the radial direction, avoiding relative rotation in the circumferential direction, and ensuring that each support block expands synchronously when the cone surface transmits force. The outer side of the arc-shaped support block 10 is covered with a polyurethane friction layer 13. In this embodiment, the polyurethane friction layer 13 is defined as a composite contact layer with a high-strength copper alloy as the basic force transmission skeleton and polyurethane elastic micro-protrusions locally embedded on its contact surface through micro-nano texture technology. In this composite structure, the thick-walled copper alloy skeleton at the bottom layer provides rigid support and shear resistance when bearing the cutting resistance torque of the thick-walled tube, preventing the clamping center from shifting due to excessive material compression or softening, and ensuring the coaxiality of the spindle rotation from a physical basis. The polyurethane elastic micro-protrusions embedded on the surface layer can absorb some high-frequency surface micro-vibrations after contacting the inner wall of the stainless steel tube, providing ultimate rigidity while taking into account interface contact compliance, effectively meeting the stable friction transmission requirements under the heavy load of the submarine steel tube. An annular groove 14 is provided on the outer side of the arc-shaped support block 10. After the annular tension spring 15 is embedded in the annular groove 14, it applies a contracting force towards the central axis to the multiple arc-shaped support blocks 10, so that the arc-shaped support blocks 10 automatically reset when the conical expansion block 8 is released from the pullback. This reset structure is used to ensure the consistency of opening and closing during clamping and unloading, and also to keep each arc-shaped support block 10 continuously close to the conical surface when the conical expansion block 8 is axially adjusted within a preset range, reducing the impact caused by the gap. Through the combination of evenly distributed guide, elastic friction layer and spring reset, the clamping interface has positioning, force transmission and buffering functions at the same time, thereby improving the clamping stability under dust adhesion and wear degradation conditions.

[0020] Combination Figure 3 The hollow drive shaft 3 has a reduced-diameter shoulder step 16 machined in its inner hole, and a limit nut 17 is fixed on the push-pull rod 7; one end of the disc spring assembly 12 abuts against the shoulder step 16, and the other end of the disc spring assembly 12 abuts against the limit nut 17.

[0021] In this embodiment, the inner hole of the hollow drive shaft 3 is provided with a reduced-diameter shoulder step 16 to form the fixed reaction end of the disc spring assembly 12; a limiting nut 17 is fixed on the push-pull rod 7 to form the force-bearing moving end of the disc spring assembly 12; after one end of the disc spring assembly 12 abuts against the shoulder step 16 and the other end abuts against the limiting nut 17, compression and release occur during the axial displacement of the push-pull rod 7, thereby establishing a repeatable preload force inside the structure; the relative position between the shoulder step 16 and the limiting nut 17 is used to limit the working compression amount of the disc spring assembly 12, so that the disc spring assembly 12 still outputs a predetermined basic tension after the rotary cylinder 6 is unloaded; The basic tension is transmitted to the conical expansion block 8 via the push-pull rod 7, and then converted into the basic normal clamping force of the arc-shaped support block 10 through the conical surface. This is used to maintain the minimum safe clamping level of the stainless steel pipe in the non-pressurized state. The relative contact between the shoulder step 16 and the limit nut 17 ensures that the energy storage path of the disc spring assembly 12 is coaxial with the force transmission path of the push-pull rod 7, reducing uneven spring force caused by off-center loading. This structure also makes it easy to change the pre-compression of the disc spring assembly 12 by adjusting the installation position of the limit nut 17, so that the basic clamping force can be adapted to stainless steel pipes with different diameters and wall thicknesses. Thus, the disc spring assembly 12 not only serves as a holding mechanism in the air-cut state, but also as a mechanical setting mechanism for the basic clamping force in the entire fastening process.

[0022] The servo motor 5 is connected to the input end of the hollow drive shaft 3 via a plum blossom-shaped flexible coupling 18; wherein the hollow drive shaft 3 is axially and radially positioned by angular contact ball bearings 19 mounted back to back.

[0023] In this embodiment, the servo motor 5 is connected to the input end of the hollow drive shaft 3 via a plum blossom-shaped flexible coupling 18. The plum blossom-shaped flexible coupling 18 is used to compensate for the installation deviation between the output shaft of the servo motor 5 and the hollow drive shaft 3 while transmitting torque, reducing the additional load caused by the deviation being directly transmitted to the bearing support end. Since there are periodic cutting resistance fluctuations and instantaneous torque changes during the polishing process, the elastic element of the coupling is also used to weaken the direct impact of torque pulsation on the hollow drive shaft 3, making the angular acceleration measurement signal closer to the load change. The hollow drive shaft 3 is axially and radially positioned by back-to-back angular contact ball bearings 19. In this embodiment, the back-to-back installation means that the force lines of the two bearings are spread out in opposite directions along the axial direction, so as to improve the ability of the spindle assembly to withstand bidirectional axial force and overturning moment. This support form is used to limit the axial movement and radial swing of the hollow drive shaft 3 under the combined action of rotation and clamping, and to ensure the stability of the coaxial fit between the tapered expansion block 8, the push-pull rod 7 and the arc support block 10. Compared with the support method of ordinary deep groove ball bearings, the combined support of angular contact ball bearing 19 is more suitable for bearing the composite load caused by polishing contact force, which helps to reduce the interference of rotational state fluctuations on friction state inversion calculation. Thus, the servo motor 5, coupling and bearing support form a stable power input and support unit, providing a repeatable mechanical basis for subsequent angular acceleration identification and clamping force adjustment.

[0024] The outer conical surface 9 and the inner conical surface 11 both have a taper of 15°; the end of the push-pull rod 7 is machined with an external thread 20, and the conical expansion block 8 is screwed and fixed to the external thread 20 through the central threaded hole 21.

[0025] In this embodiment, the outer conical surface 9 of the conical expansion block 8 and the inner conical surface 11 of the arc-shaped support block 10 are set to the same taper to ensure that a continuous surface contact force transmission relationship is formed when the conical surfaces are in contact; when the taper is 15°, the axial tension applied by the push-pull rod 7 can form a controllable radial expansion force during the mechanical conversion process, while maintaining a stable pullback response of the conical expansion block 8 under load fluctuation conditions. This angle setting is designed to balance force amplification capability and motion sensitivity, avoiding excessive taper leading to insufficient amplification of radial displacement by axial displacement, and also avoiding excessive taper leading to increased friction self-locking tendency, which would affect dynamic adjustment; the end of the push-pull rod 7 is machined with an external thread 20, and the tapered expansion block 8 is screwed and fixed to the external thread 20 through the central threaded hole 21, and can be assembled and positioned along the axis of the push-pull rod 7; the threaded connection is used to realize the detachable installation of the tapered expansion block 8, which is convenient for replacing tapered expansion blocks 8 and arc-shaped support blocks 10 of different external dimensions for stainless steel pipes with different inner diameter specifications; The threaded connection is also used to fine-tune the initial axial position of the tapered expansion block 8 relative to the push-pull rod 7, thereby changing the initial expansion amount of the arc-shaped support block 10 in the basic state; through the combination of uniform taper fit and adjustable threaded connection, the device has both a stable mechanical conversion relationship and the ability to adjust the structure to adapt to different workpiece specifications.

[0026] The device also includes: a photoelectric encoder, which is connected to the hollow drive shaft 3; wherein, the photoelectric encoder is used to record the rotation state of the hollow drive shaft 3 and output a position signal; The industrial control computer is connected to the photoelectric encoder, the servo motor 5, and the rotary cylinder 6. The industrial control computer is configured to calculate the angular acceleration based on the rotation state and to dynamically control the air pressure of the rotary cylinder 6 and the speed of the servo motor 5.

[0027] In this embodiment, the device is also equipped with a photoelectric encoder and an industrial control computer so that the mechanical clamping mechanism and the dynamic adjustment logic form a corresponding relationship; after the photoelectric encoder is connected to the hollow drive shaft 3, it rotates synchronously with the hollow drive shaft 3 and outputs a position signal; the rotation state in this embodiment includes angular displacement, angular velocity, and angular acceleration obtained from the change of angular velocity; After the industrial control computer is connected to the photoelectric encoder, servo motor 5, and rotary cylinder 6, it can receive position signals and calculate the rotational state parameters of the hollow drive shaft 3. At the same time, it outputs speed commands or torque-related commands to the servo motor 5 and air pressure adjustment commands to the rotary cylinder 6. The industrial control computer calculates angular acceleration to convert the dynamic response of the rotating system to load changes into a control quantity that can be used for clamping adjustment. Compared with the method of relying on external contact sensors or vision sensors to identify changes in working conditions, the rotational state signal obtained by the photoelectric encoder can directly reflect the torsional response of the hollow drive shaft 3 and the stainless steel tube, reducing the impact of environmental dust on the detection stability. After the industrial control computer dynamically controls the air pressure of the rotary cylinder 6, the pull-back force of the push-pull rod 7 changes accordingly, and the normal clamping force of the arc-shaped support block 10 on the inner wall of the stainless steel tube changes synchronously; after the industrial control computer dynamically controls the speed of the servo motor 5, the surface linear velocity during the cutting contact process changes accordingly; thus, the photoelectric encoder is responsible for providing state data, the industrial control computer is responsible for performing calculations and control, and the mechanical clamping mechanism is responsible for completing the mechanical response, and the three form a clamping and adjustment system based on the rotation state; In this embodiment, the high-resolution position signal is preferably a pulse increment signal or absolute angle code value within a unit sampling period. The industrial control computer processes the signal in the following order: continuously read the angular displacement data of adjacent time points according to the preset sampling period; convert the difference in angular displacement between adjacent time points into an angular velocity sequence; perform differential comparison on the continuous angular velocity sequence to obtain an angular acceleration sequence reflecting the rate of change of angular velocity; and write the angular displacement, angular velocity, and angular acceleration into the control buffer area respectively, as common inputs for subsequent friction state judgment, load disturbance identification, and thermal state assessment. In this embodiment, the preset sampling period is defined as the time interval between the industrial control computer reading and updating the photoelectric encoder signal once. Its value is determined based on the maximum operating speed of the servo motor 5, the resolution of the photoelectric encoder, and the angular acceleration recognition sensitivity, so as to ensure that the speed change before and after the load change can be distinguished during the polishing process, and to avoid the distortion of angular acceleration calculation due to insufficient sampling. In this embodiment, dynamic control is configured to use rotational state parameters as judgment inputs for coordinated adjustment: when the angular acceleration is within the set fluctuation range, the industrial control computer maintains the current air pressure and speed commands; the set fluctuation range is defined in this embodiment as the normal fluctuation range of angular acceleration caused by the surface roughness of the material and the background vibration of the mechanical system under normal grinding conditions of the hollow drive shaft 3. Its upper and lower limits are automatically calculated and determined by the industrial control computer collecting the peak and valley values ​​of angular acceleration when there is no significant change in cutting resistance during the trial operation phase and combining them with the preset tolerance coefficient. When the angular acceleration shows a continuous decrease or a sudden negative change, the industrial control computer recognizes this state as a trigger signal for an increase in cutting resistance and outputs the judgment result that the clamping force needs to be compensated to the subsequent control process; when the thermal state assessment result shows that there is a risk of material yielding if the pressure is increased further, the industrial control computer uses the assessment result as a limiting condition to constrain the pressure increase of the rotary cylinder 6 and simultaneously reduce the speed of the servo motor 5. By defining the signal source, processing order, and result flow as described above, a clear data link is formed between the original encoder signal and the control command in the rotation state calculation process, so that there is a clear correspondence between the calculation object, judgment basis, and control output of the industrial control computer.

[0028] Combination Figure 4 A method for controlling a fastening device for polishing and grinding stainless steel pipes includes the following steps performed sequentially: S1. Friction State Inversion Stage: During the no-load rotation process, the servo motor 5 is controlled to output a step torque, driving the hollow drive shaft 3 to accelerate the rotation of the stainless steel tube; the rotational speed data is recorded and the angular acceleration is calculated; based on the preset total rotational inertia, step torque, and angular acceleration of the system, the resistance torque caused by friction transmission loss is separated; based on the preset initial normal tension force determined by the preload released by the disc spring assembly and the basic pull-back pressure of the rotary cylinder, the friction coefficient is inverted and calculated; if the friction coefficient is less than the preset friction coefficient threshold, the rotary cylinder 6 is controlled to increase the basic pull-back pressure; if the friction coefficient is greater than or equal to the preset friction coefficient threshold, the basic pull-back pressure is kept unchanged; and the adjusted normal tension force or the unchanged preset initial normal tension force is used as the current normal tension force; S2, Load Sudden Change Feedforward Compensation Stage: During the polishing and grinding process, the negative sudden change value of the angular acceleration of the hollow drive shaft 3 is monitored in real time; when the decrease in angular acceleration exceeds the preset negative critical lower limit, the negative sudden change value is obtained based on the difference exceeding the negative critical lower limit, and the required normal tension force is determined based on the negative sudden change value, the preset total rotational inertia of the system, the preset inner radius of the stainless steel tube to be processed, and the friction coefficient; the rotary cylinder 6 is controlled to increase the pull-back force on the push-pull rod 7 according to the required normal tension force; S3, Adaptive Stage for Preventing Yield Fading: During continuous grinding, the real-time current feedback value of the servo motor 5 driver is read and combined with a preset torque constant. The preset torque constant is the inherent torque proportional coefficient of the servo motor, determined by the motor's factory calibration parameters. The current cutting resistance torque is obtained, and the instantaneous cutting power is obtained based on the current cutting resistance torque and the angular velocity of the hollow drive shaft. The heat accumulation state of the stainless steel tube is obtained based on the processing time and the instantaneous cutting power. The preset maximum allowable tensile force threshold is dynamically lowered according to the heat accumulation state to obtain the lowered maximum allowable tensile force threshold. When the required normal tension force is greater than the lowered maximum allowable tensile force threshold, the increase in the tension of the rotary cylinder 6 is limited, and the speed of the servo motor 5 is actively reduced by issuing a speed command. When the required normal tension force is less than or equal to the lowered maximum allowable tensile force threshold, the rotary cylinder 6 is controlled to output the required normal tension force.

[0029] In this embodiment, the method is used in conjunction with the fastening device to complete the adaptive clamping control of the stainless steel tube during the polishing and grinding process. The steps are executed in sequence according to the friction state inversion stage, the load change feedforward compensation stage, and the anti-yield thermal decay adaptive stage. In the friction state inversion stage, since the friction capability between the polyurethane friction layer 13 and the inner wall of the stainless steel tube changes with dust, wear and surface temperature rise, the servo motor 5 outputs a step torque during the no-load start-up process, the hollow drive shaft 3 drives the stainless steel tube to accelerate rotation, the photoelectric encoder records the rotation speed data, the industrial control computer calculates the angular acceleration from the rotation speed data, and then combines the preset total rotational inertia of the system and the step torque to separate the resistance torque caused by friction transmission loss, and inverts the friction coefficient accordingly. If the coefficient of friction is lower than the preset coefficient of friction threshold, the industrial control computer controls the rotary cylinder 6 to increase the basic pull-back pressure, so that the rotation drive friction margin is restored to the set range; if the coefficient of friction reaches or exceeds the preset coefficient of friction threshold, the basic pull-back pressure is kept unchanged to avoid unnecessary increase in the inner wall contact stress. During the load mutation feedforward compensation stage, to avoid the problem of lag in clamping force establishment caused by relying solely on speed feedback adjustment, the industrial control computer monitors the negative mutation value of angular acceleration in real time. The negative mutation value refers to the decrease in angular acceleration in the current sampling period compared to the previous period, and the magnitude of this decrease exceeds the negative critical lower limit of the set fluctuation band. The industrial control computer extracts the difference exceeding the critical lower limit as the negative mutation value, thereby effectively filtering normal machining vibration interference. It also uses the preset total rotational inertia of the system to calculate the increase in instantaneous cutting resistance torque, and calculates the increment of normal clamping force based on the preset inner radius and friction coefficient to obtain the required normal clamping force. The rotary cylinder 6 increases the pull-back force on the push-pull rod 7 according to the required normal clamping force. The conical expansion block 8 and the arc-shaped support block 10 convert this pull-back force into an increase in the positive pressure on the inner wall of the pipe to maintain the friction transmission capacity during the load increase phase. In the anti-yield thermal decay adaptive phase, in order to prevent the accumulation of heat on the pipe wall from causing a decrease in load-bearing capacity and local plastic deformation, the current cutting resistance torque is multiplied by the rotational speed of the hollow drive shaft 3 to obtain the instantaneous cutting power, and then integrated over the processing time to obtain the heat accumulation state. This integral calculation process is used to dynamically estimate the thermal load level of the stainless steel pipe during continuous grinding when the pipe wall temperature cannot be directly measured. The system receives the rotational speed of the hollow drive shaft 3 and the current cutting resistance torque as real-time inputs, multiplies them to obtain the instantaneous cutting power, and integrates this power over time at a preset sampling period to output the heat accumulation state value. Based on the digital sampling characteristics of the control system, the above integration calculation adopts discrete-time accumulation logic. The specific process is as follows: at the arrival of each preset sampling period, the industrial control computer reads the current cutting resistance torque and angular velocity from the communication bus, performs a multiplication operation to obtain the instantaneous cutting power of the current period, multiplies the instantaneous cutting power by the time length of the preset sampling period, and calculates the single-step heat load increment. The industrial control computer uses a discrete-time accumulation model to calculate the heat accumulation state value, satisfying the following equation:

[0030] in, This represents the cumulative heat state value for the current cycle. This represents the accumulated heat state value from the previous cycle. The environmental heat dissipation coefficient. Instantaneous cutting power, The time length of the sampling period; the calculated... Write the data to the heat accumulation state cache to complete one state update; To more accurately reflect the thermophysical process, a preset heat dissipation coefficient can be introduced before accumulation to proportionally attenuate the heat accumulation state value of the previous cycle, so as to characterize the environmental heat dissipation effect. The preset heat dissipation coefficient is obtained in advance by natural cooling calibration experiments of stainless steel pipes of different specifications and wall thicknesses under different base ambient temperatures, and is stored as a mapping matrix in the parameter library of the industrial control computer. When the industrial control computer is running, it matches and extracts the coefficient based on the ambient temperature and the specifications of the currently clamped workpiece. The above process characterizes the dynamic process of mechanical energy being converted into heat energy at the cutting interface and accumulating over time inside the thin-walled stainless steel tube, thus providing a quantitative basis for subsequent thermal decay protection; the industrial control computer dynamically lowers the preset maximum allowable tensile force threshold based on the heat accumulation state to obtain the allowable tension limit corresponding to the current thermal state; When the required normal clamping force exceeds the threshold, the industrial control computer limits the rotary cylinder 6 from continuing to pressurize and reduces the speed command of the servo motor 5 to reduce the current cutting resistance torque by reducing the cutting line speed; when the required normal clamping force does not exceed the threshold, the rotary cylinder 6 outputs the corresponding clamping force according to the calculation result; this method converts the friction state, load disturbance and thermal state into calculable controllable quantities, so that basic clamping, dynamic pressurization and thermal protection are implemented in a coordinated manner on the same device; In this embodiment, the preset friction coefficient threshold, the current normal tension force, the preset maximum allowable tensile force threshold, and the heat accumulation state are all used as key judgment quantities in the control process. The preset friction coefficient threshold is used in this embodiment to characterize the minimum friction capability benchmark required to maintain stable friction transmission. The preferred method for determining it is to first establish an empirical parameter table based on the material of the stainless steel pipe to be processed, the range of inner wall roughness, and the material of the polyurethane friction layer 13, and then select a safety lower limit based on the historical friction coefficient value obtained during the trial operation. The industrial control computer calls this safety lower limit as the judgment threshold for whether the basic pull-back pressure needs to be increased. In this embodiment, the current normal tension force is defined as the combined state quantity of the basic holding force provided by the disc spring assembly 12, the clamping force after the current output pull-back force of the rotary cylinder 6 is converted by the conical surface, and the compensation result of the previous control cycle. The industrial control computer updates this state quantity at the end of each control cycle so that the calculation of the subsequent normal tension force increment has a continuous reference benchmark. In this embodiment, the heat accumulation state is defined as a state quantity representing the heat load level of the tube wall obtained by the accumulation of cutting power over time during continuous grinding. It is used to characterize the degree of processing heat influence that the current workpiece has accumulated relative to the cold state reference. The preset maximum allowable tensile force threshold is used in this embodiment to limit the maximum safe tension level that the clamping mechanism can apply to the inner wall of the stainless steel tube under the current hot state. The preferred method for determining it is to pre-establish a threshold mapping table based on the stainless steel tube wall thickness, material yield strength and inner support contact area, and set the allowable tensile force under the cold state as the initial upper limit, which is then gradually lowered by the industrial control computer according to the heat accumulation state. The three stages described above have a clear data succession relationship in terms of execution order: the friction coefficient output in step S1 is written into the control parameter area and used as the input for calculating the normal tension force increment in step S2; the required normal tension force output in step S2 is directly transmitted to the rotary cylinder 6 control module on the one hand, and written into the status buffer area on the other hand, used as the comparison object for step S3 to determine whether the maximum allowable tension threshold is exceeded. The pressure limiting and speed reduction results output in step S3 are fed back to the next control cycle as boundary conditions for updating the current normal tension force and speed commands. By defining the physical meaning, source and flow direction of key judgment quantities, the triggering role and connection relationship of each parameter in the three-stage control process are clarified, thereby avoiding the method steps from merely remaining at the level of result description.

[0031] In step S1, the logic for separating the resistance torque is as follows: it is obtained based on the step torque, the preset total rotational inertia of the system, and the angular acceleration; the logic for inverting and calculating the friction coefficient is as follows: it is obtained based on the resistance torque, the preset inner radius, and the preset initial normal tension force.

[0032] In this embodiment, step S1 adopts the resistance torque separation logic based on the rotational dynamics balance relationship; the industrial control computer receives the step torque command value of the servo motor 5 and calculates the angular acceleration from the rotational state data output by the photoelectric encoder; the preset total rotational inertia of the system is the sum of the equivalent rotational inertia of the rotating part of the device and the corresponding stainless steel pipe. This parameter is determined by the industrial control computer calling the corresponding parameter table after clamping the corresponding workpiece specification. Since part of the step torque is used to overcome the system inertia to establish angular acceleration, and the other part is used to overcome frictional transmission loss, the drag torque caused by frictional transmission loss is obtained by subtracting the product of the preset total rotational inertia and angular acceleration from the step torque. The data flow path for this separate calculation is as follows: the industrial control computer extracts the currently issued step torque command value from the control output buffer, and at the same time reads the angular acceleration from the output port of the photoelectric encoder signal processing module; according to the specifications of the currently assembled stainless steel pipe, it calls the corresponding preset total system rotational inertia from the system configuration database; the central processing unit performs multiplication and subtraction operations, and the resulting resistance torque data is appended with the current timestamp and stored in the input register of the friction state inversion module as the divisor for the next calculation; In this embodiment, the resistance torque is used to characterize the friction loss level between the outer friction layer of the arc-shaped support block 10 and the inner wall of the stainless steel tube; the friction coefficient is obtained by dividing the resistance torque caused by friction transmission loss by the product of the preset inner radius and the preset initial normal tension force. The preset inner radius is derived from the specifications of the stainless steel tube to be processed, and the preset initial normal tension force is derived from the preload of the disc spring assembly 12 and the basic pull-back pressure of the rotary cylinder 6, corresponding to the basic clamping state. This step obtains the friction coefficient result based on rotational dynamics data, eliminating the need to place friction sensors on the clamping interface. The result is used to determine the degree of frictional degradation of the current clamping interface and to provide a quantitative basis for subsequent air pressure compensation, so that the adjustment of the basic support force matches the frictional capacity; the above calculation logic is used to extract the frictional characteristics of the clamping interface in real time using the rotational state data of the drive end without adding additional sensors. The above calculation receives a step torque command and angular acceleration as inputs, and combines them with the preset total system inertia to separate the resistance torque used to overcome frictional losses. Using the resistance torque, preset inner radius, and preset initial normal clamping force as inputs, the friction coefficient is calculated and output. This model characterizes the distribution relationship between the rotational driving force in overcoming system inertia and overcoming interface frictional resistance. Based on the known system inertial response and total input, the resistance torque caused by frictional transmission losses is calculated to determine the degree of frictional degradation.

[0033] In step S2, the logic for calculating the increment of the normal tension force is as follows: based on the increase in instantaneous cutting resistance torque, the preset inner radius, and the friction coefficient; the logic for calculating the required normal tension force is as follows: based on the current normal tension force and the increment of the normal tension force; the pull-back force increased by the rotary cylinder 6 is mechanically amplified by the outer conical surface 9 of the conical expansion block 8.

[0034] In this embodiment, step S2 uses the calculation logic of the clamping force compensation amount to be derived from the load disturbance; after the industrial control computer identifies the negative change in the angular acceleration signal, it multiplies the absolute value of the negative change value with the preset total rotational inertia of the system to obtain the increase in instantaneous cutting resistance torque; since the critical condition for the stainless steel pipe to slip is determined by the cutting resistance torque, the preset inner radius and the friction coefficient, the industrial control computer divides the increase in instantaneous cutting resistance torque by the product of the preset inner radius and the friction coefficient to obtain the increase in normal clamping force required to maintain non-slip transmission, i.e., the increment of normal clamping force; The current normal tension force is composed of the basic tension force and the previous adjustment result. The industrial control computer adds the current normal tension force and the normal tension force increment to obtain the required normal tension force, and calculates the additional pull force that the rotary cylinder 6 should output accordingly. The pull force increased by the rotary cylinder 6 is transmitted to the conical expansion block 8 through the push-pull rod 7. After the outer conical surface 9 of the conical expansion block 8 contacts the inner conical surface 11 of the arc-shaped support block 10, the axial pull force is converted into a radial expansion force, so that the arc-shaped support block 10 generates an incremental positive pressure on the inner wall of the stainless steel pipe. This mechanical amplification relationship enables the adjustment amount set on the pneumatic side to form a usable normal force change at the clamping interface, thereby improving the response capability to sudden changes in cutting resistance torque. After adopting the above calculation and force transmission logic, the change in normal clamping force is directly derived from the change in cutting resistance torque, reducing the lag caused by compensation based solely on speed deviation, and making the clamping force adjustment closer to the load requirements.

[0035] In step S3, the command to actively reduce the speed of the servo motor 5 is configured to be implemented by reducing the cutting line speed.

[0036] In this embodiment, the active deceleration logic in step S3 is used to deal with the problem of reduced material load-bearing capacity caused by heat accumulation. After obtaining the heat accumulation state, the industrial control computer inputs it into a preset threshold mapping relationship to obtain the maximum allowable tensile force threshold under the current thermal state. When the required normal tension force calculated in step S2 exceeds the allowable range corresponding to the threshold, if the output of the rotary cylinder 6 is increased, the radial normal pressure applied by the arc-shaped support block 10 to the inner wall of the stainless steel pipe will increase, increasing the local compressive stress. To prevent the compressive stress from exceeding the material's yield limit under the current heat accumulation state, the industrial control computer stops increasing the air pressure and sends a control command to the servo motor 5 to reduce its speed. After the servo motor 5 speed is reduced, the cutting speed on the surface of the stainless steel tube decreases accordingly, the cutting resistance torque between the polishing tool and the workpiece decreases accordingly, and the required normal clamping force also decreases. This control logic reduces the clamping requirements to within the range allowed by the current thermal state by reducing the load source strength. When the required normal tension force drops below the adjusted maximum allowable tensile force threshold, the rotary cylinder 6 can maintain a tension force output that is compatible with the load within the limited range. By linking the speed adjustment with the allowable tension threshold, the radial positive pressure applied by the arc-shaped support block 10 can always be constrained by the thermal state of the material, thereby reducing the risk of indentation and plastic deformation of the thin-walled stainless steel tube during continuous grinding. In this embodiment, the threshold mapping relationship is preferably a preset correspondence rule consisting of the heat accumulation state interval and the corresponding maximum allowable tensile force interval. The correspondence rule can be obtained by pre-experimental calibration of stainless steel pipes of the same material and wall thickness: first, determine the initial allowable tensile force under cold conditions without visible indentation or plastic deformation, and then, as the continuous grinding time increases or the heat load increases, record the safe tensile force range before local yielding occurs, and organize it into a segmented threshold table for use by the industrial control computer. The preferred execution flow for the active reduction of servo motor 5 speed command is as follows: The industrial control computer compares the required normal tension force with the maximum allowable tension threshold after reduction; when the comparison result is out of limit, the output channel of the rotary cylinder 6 for continued pressurization is frozen, so that the clamping force is kept near the current allowable upper limit; the servo motor 5 speed command is gradually reduced according to the preset speed reduction gradient, and the angular acceleration and cutting resistance torque change results are reread after each speed reduction; when the recalculated required normal tension force falls back to within the allowable threshold, the speed reduction is stopped, and the new speed command is maintained to enter the next control cycle; The aforementioned speed reduction verification process is executed by the speed reduction control state machine inside the industrial control computer. When the comparison result is out of limit, the state machine switches from normal machining mode to speed reduction mode, extracts the preset speed reduction gradient from the parameter storage area, subtracts the gradient value from the current speed command, generates a speed reduction command, and sends it to the servo motor 5 driver through the communication interface. After sending the command, the state machine starts the preset resampling timer, shields transient fluctuations, and waits for the mechanical transmission to reach a new steady state. After the timer overflows, it triggers the rereading of encoder data and the update calculation of cutting resistance torque. This closed-loop data interaction process of deceleration-waiting-resampling-verification is executed cyclically within the state machine until the verification result meets the standard, thereby ensuring the timing match between control commands and mechanical physical responses; the preset deceleration gradient in this embodiment is used to limit the magnitude of a single speed adjustment, and its configuration is used to avoid sudden changes in polishing contact state or fluctuations in the quality of the processed surface due to a one-time large speed reduction. Preferably, it is preset to multiple decreasing levels according to the current speed level, the contact characteristics of the abrasive, and the surface quality requirements of the workpiece; When the industrial control computer performs active speed reduction, it dynamically matches the decreasing gear according to the difference between the required normal tension force and the maximum allowable tensile force threshold after the reduction: when the difference exceeds the preset warning difference, a large gradient gear is called to achieve rapid load reduction and prevent yielding; when the difference exceeds the preset warning difference, a small gradient gear is called to ensure a smooth transition and avoid over-adjustment. In this embodiment, the yield strength of the material represents the upper limit of local compressive stress that the inner wall material of the stainless steel pipe can withstand under the current heat accumulation state. The industrial control computer indirectly constrains the yield strength of the material through the maximum allowable tensile force threshold corresponding to the heat accumulation state. Therefore, the maximum allowable tensile force threshold constitutes the judgment interface for the material yield risk to enter the control process. The active speed reduction adopts a judgment-pressure limiting-speed reduction-verification processing link; the above active speed reduction and pressure limiting logic is configured to dynamically adjust the clamping parameters under high temperature conditions to prevent local plastic deformation of stainless steel pipes; The control system receives the heat accumulation status as input, and outputs the adjusted maximum allowable tensile force threshold by querying the pre-calibrated threshold mapping relationship. The required normal tension force is compared with the threshold. If the limit is exceeded, control commands to reduce the speed and freezing air pressure are output to the servo motor 5 and the rotary cylinder 6, respectively. This model characterizes the physical law that the yield strength of a material decreases with heat accumulation. As heat accumulation leads to a decrease in the material's load-bearing capacity, reducing the cutting resistance and maintaining the normal clamping force required for transmission by decreasing the rotational speed ensures that the normal pressure at the clamping interface remains within the safe boundary allowed by the current thermal state, achieving an adaptive match between machining parameters and the thermodynamic properties of the material. Comparative experiments are as follows: Experimental subjects and environment: A high-strength alloy steel pipe with an outer diameter of 450 mm, a wall thickness of 40 mm, and a length of 6000 mm was selected for the pressure-resistant fluid pipeline of a certain type of deep-sea submersible; Control group A adopted a traditional single-end clamping and pure rotational speed feedback fixed normal support force device; Experimental group B adopted the double-end coaxial fastening device of the present invention and the control method including the complete adaptive algorithm from S1 to S3.

[0037] The experimental data comparison and analysis are as follows: Straightness index test: In the middle section of grinding, the control group A was affected by the maximum cutting inertia and self-weight deflection. The maximum straightness runout of the whole length after processing was 0.68mm / m, which did not meet the assembly requirement of 0.1mm / m. After introducing the tailstock synchronous clamping mechanism, the double-end support stiffness dynamically and adaptively changed with the position of the grinding head. The straightness runout of the whole length was strictly controlled within 0.03mm / m, which met the processing accuracy requirements and thus suppressed the boundary layer separation and turbulence noise generation during the fluid transportation process. Yield resistance and thermal decay protection test: Under continuous high-load grinding conditions for 4 hours, the inner wall of the pipe in control group A suffered local plastic indentation depth of 0.16mm due to heat accumulation and constant high-pressure clamping force, resulting in irreversible damage; In experimental group B, after triggering step S3, the industrial control computer assessed the heat load level and dynamically limited the pressure and reduced the speed. After processing, the maximum indentation depth of the inner wall was 0.008mm, and the material showed no signs of yielding, indicating the protective capabilities of the control model and polyurethane friction layer of the present invention under heavy-load grinding conditions.

[0038] This application has been described through the above embodiments; however, it should be understood that the above embodiments are for illustrative purposes only and are not intended to limit this application to the described embodiments. Those skilled in the art will understand that many more variations and modifications can be made based on the teachings of this application, and all such variations and modifications fall within the scope of protection claimed in this application.

Claims

1. A fastening device for polishing and grinding stainless steel pipes, characterized in that, include: Base (1); The first bearing housing (2) is rigidly fixed to the base (1); A hollow drive shaft (3) is supported in the inner hole of the first bearing seat (2), and a radial guide groove (4) is machined on its outer wall. A servo motor (5) is mounted on the base (1), and its output end is connected to the hollow drive shaft (3) to provide rotational driving force. A rotary cylinder (6) is fixed on the base (1), and its piston rod is connected to a push-pull rod (7). A push-pull rod (7) coaxially passes through the internal hollow channel of the hollow drive shaft (3), and its end away from the rotary cylinder (6) is connected to a conical expansion block (8); a tailstock synchronous clamping mechanism is set at one end of the base (1) away from the first bearing seat (2), and the tailstock synchronous clamping mechanism is configured to cooperate with the hollow drive shaft (3) to form a double-end coaxial support to constrain the self-weight deflection of the thick-walled alloy steel pipe and maintain the machining straightness; The conical expansion block (8) has an outer conical surface (9) machined on its outer surface. The arc-shaped support block (10) is slidably installed in the radial guide groove (4), and its inner side is machined with an inner cone surface (11) that matches the outer cone surface (9). The disc spring assembly (12) is fitted outside the push-pull rod (7) and is used to release the preload when the rotary cylinder (6) is venting and unloading. Both ends of the disc spring assembly abut against the push-pull rod (7) and the hollow drive shaft (3) respectively to form a preload fit.

2. The fastening device for polishing and grinding stainless steel pipes according to claim 1, characterized in that, The radial guide grooves (4) are evenly distributed along the circumferential direction, and the arc-shaped support blocks (10) are embedded in the corresponding radial guide grooves (4); wherein, the outer side of the arc-shaped support blocks (10) is covered with a polyurethane friction layer (13); the polyurethane friction layer (13) is fixed to the outer periphery of the arc-shaped support blocks (10) and is used to provide heavy load rigidity transmission and shear resistance when bearing the heavy cutting resistance torque of thick-walled pipes.

3. The fastening device for polishing and grinding stainless steel pipes according to claim 1, characterized in that, The hollow drive shaft (3) has a reduced-diameter shoulder step (16) machined in its inner hole, and a limit nut (17) is fixed on the push-pull rod (7); wherein, one end of the disc spring assembly (12) abuts against the shoulder step (16), and the other end of the disc spring assembly (12) abuts against the limit nut (17).

4. The fastening device for polishing and grinding stainless steel pipes according to claim 1, characterized in that, The servo motor (5) is connected to the input end of the hollow drive shaft (3) via a plum blossom-shaped flexible coupling (18); wherein the hollow drive shaft (3) is axially and radially positioned by angular contact ball bearings (19) mounted back to back.

5. The fastening device for polishing and grinding stainless steel pipes according to claim 1, characterized in that, The outer conical surface (9) and the inner conical surface (11) both have a taper of 15°; wherein, the end of the push-pull rod (7) is machined with an external thread (20), and the conical expansion block (8) is screwed and fixed to the external thread (20) through the central threaded hole (21).

6. The fastening device for polishing and grinding stainless steel pipes according to claim 1, characterized in that, Also includes: A photoelectric encoder is connected to the hollow drive shaft (3); wherein the photoelectric encoder is used to record the rotation state of the hollow drive shaft (3) and output position signals; an industrial control computer is communicatively connected to the photoelectric encoder, the servo motor (5) and the rotary cylinder (6); wherein the industrial control computer is configured to calculate angular acceleration according to the rotation state and dynamically control the air pressure of the rotary cylinder (6) and the rotation speed of the servo motor (5).

7. A method for using the fastening device for polishing and grinding stainless steel pipes as described in claim 6, characterized in that, The following steps are performed sequentially: S1, Friction State Inversion Stage: During the no-load start-up process, the servo motor (5) is controlled to output a step torque to drive the hollow drive shaft (3) to accelerate the rotation of the stainless steel tube; the rotation speed data is recorded and the angular acceleration is calculated; based on the preset total rotational inertia of the system, the step torque and the angular acceleration, the resistance torque caused by friction transmission loss is separated; based on the preset initial normal tension force determined by the preload released by the disc spring group and the basic pull-back pressure of the rotary cylinder, the friction coefficient is inverted and calculated; if the friction coefficient is less than the preset friction coefficient threshold, the rotary cylinder (6) is controlled to increase the basic pull-back pressure; If the coefficient of friction is greater than or equal to the preset coefficient of friction threshold, then the basic pullback pressure remains unchanged; The adjusted normal tension force or the preset initial normal tension force that remains unchanged is taken as the current normal tension force; S2, Load mutation feedforward compensation stage: During the polishing and grinding process, the negative mutation value of the angular acceleration of the hollow drive shaft (3) is monitored in real time; when the decrease of the angular acceleration exceeds the preset negative critical lower limit, the negative mutation value is obtained according to the difference exceeding the negative critical lower limit, and the required normal tension force is determined based on the negative mutation value, the preset total rotational inertia of the system, the preset inner radius of the stainless steel pipe to be processed and the friction coefficient. The rotary cylinder (6) is controlled to increase the pull-back force on the push-pull rod (7) according to the required normal tension force; S3, Adaptive Stage for Preventing Yield Fading: During continuous grinding, the real-time current feedback value of the servo motor (5) driver is read and combined with a preset torque constant, which is the inherent torque proportional coefficient of the servo motor and is determined by the motor's factory calibration parameters; the current cutting resistance torque is obtained, and the instantaneous cutting power is obtained based on the current cutting resistance torque and the angular velocity of the hollow drive shaft, and the heat accumulation state of the stainless steel tube is obtained based on the processing time and the instantaneous cutting power; the preset maximum allowable tensile force threshold is dynamically lowered according to the heat accumulation state to obtain the lowered maximum allowable tensile force threshold; when the required normal tension force is greater than the lowered maximum allowable tensile force threshold, the increase in the tension of the rotary cylinder (6) is restricted, and the speed of the servo motor (5) is actively reduced by issuing a speed command; when the required normal tension force is less than or equal to the lowered maximum allowable tensile force threshold, the rotary cylinder (6) is controlled to output the required normal tension force.

8. The method according to claim 7, characterized in that, In step S1, the logic for separating the resistance torque is as follows: it is obtained based on the step torque, the preset total rotational inertia of the system, and the angular acceleration; wherein, the logic for inverting and calculating the friction coefficient is as follows: it is obtained based on the resistance torque, the preset inner radius, and the preset initial normal tension force.

9. The method according to claim 7, characterized in that, In step S2, the logic for calculating the increment of the normal tension force is as follows: based on the increase in the instantaneous cutting resistance torque, the preset inner radius, and the friction coefficient; wherein, the logic for calculating the required normal tension force is as follows: based on the current normal tension force and the increment of the normal tension force; wherein, the pull-back force increased by the rotary cylinder (6) is mechanically amplified through the outer conical surface (9) of the conical expansion block (8).

10. The method according to claim 7, characterized in that, In step S3, the command to actively reduce the speed of the servo motor (5) is configured to be implemented by reducing the cutting line speed.

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