An automatic cutting device for lining oil pipes

Abstract

The present application relates to the field of mechanical manufacturing and pipe processing equipment, in particular to an automatic cutting device for inner lining oil pipe processing; it comprises a bed body, a main shaft transmission mechanism, a feeding transmission mechanism, a variable stiffness tool holder mechanism and a self-adaptive antagonistic mechanism; the main shaft and the feeding mechanism are respectively used for oil pipe clamping rotation and tool holder radial feeding, the variable stiffness tool holder provides dynamic adjustable cutting stiffness and sprays deep cooling airflow, and the self-adaptive antagonistic mechanism uses cutting deflection force to stimulate reverse counteracting prestress; the core is that a control system performs interface identification based on servo motor output torque change, dynamically reduces excitation current when a blade is about to penetrate an outer layer steel pipe, and makes the magnetic fluid in a buffer cavity switch to a flexible compliant state; the present application discards the constant stiffness cutting mode, absorbs the residual kinetic energy of the feeding system by using the state conversion of the magnetorheological fluid, solves the tool forward thrust problem caused by the sudden drop of cutting resistance, and effectively avoids tool overcutting.

Description

Technical Field

[0001] This invention relates to the field of machinery manufacturing and pipe processing equipment, specifically to an automated cutting device for processing inner-lined oil pipes. Background Technology

[0002] In the current rotary cutting environment for lined oil pipes, the pipe is usually composed of an outer metal layer and an inner non-metal layer. The cutting operation is completed by rotating the spindle and coordinating with the radial feed of the tool. To cut such composite pipes, existing equipment generally adopts a machining architecture with a constant stiffness tool holder and conventional cooling. Although this solution can meet the cutting requirements of homogeneous materials in the case of cutting a single homogeneous metal, there are significant differences in cutting resistance, thermal sensitivity, and elastic response between the inner and outer layers of the lined oil pipe. When the tool penetrates the hard outer metal layer and enters the interface of the flexible inner non-metal layer, the cutting resistance decreases abruptly. The existing system uses static rigid support, which cannot absorb the residual kinetic energy of the feed system caused by the sudden change in resistance, resulting in the tool overcutting. At the same time, conventional cooling cannot change the high toughness and easy adhesion characteristics of the inner non-metal layer, and the constant stiffness tool holder cannot adaptively offset the tangential yaw and chatter caused by the force fluctuation after cutting into the inner layer, which will cause deep damage to the machined surface.

[0003] Therefore, how to balance the rigidity and compliance requirements for cutting different material layers, and adaptively suppress tool deflection during abrupt interface changes to reduce the probability of liner breakage, tearing and interlayer separation, has become an urgent technical problem to be solved. Summary of the Invention

[0004] To solve the above-mentioned technical problems, the present invention provides an automated cutting device for processing inner-lined oil pipes. Specifically, the technical solution of the present invention includes:

[0005] The machine bed, spindle drive mechanism, and feed drive mechanism are provided. One end of the machine bed is fixedly connected to the spindle drive mechanism, and the middle of the machine bed is slidably connected to the feed drive mechanism. A variable stiffness tool post mechanism is installed on the top surface of the feed drive mechanism. An adaptive antagonistic mechanism is provided inside the variable stiffness tool post mechanism. The variable stiffness tool post mechanism is filled with magnetorheological fluid and equipped with an excitation coil.

[0006] The cutting device also includes a control system, and the feed transmission mechanism includes a servo motor; the control system performs interface recognition based on the output torque change of the servo motor in the feed transmission mechanism, and dynamically adjusts the current of the excitation coil.

[0007] Furthermore: the spindle transmission mechanism includes a spindle box fixedly connected to one end of the bed, and the spindle is supported inside the spindle box by a double-row cylindrical roller bearing. The front flange of the spindle is fixedly connected to a three-jaw self-centering chuck by bolts, and the rear end of the spindle is connected to the output shaft of the spindle motor by a flexible coupling.

[0008] Furthermore: the feed transmission mechanism includes a feed slide slidably connected to the middle of the bed via a linear guide rail, and a lead screw bearing housing is fixedly connected to the bed parallel to the linear guide rail. A ball screw is supported in the lead screw bearing housing by an angular contact ball bearing. The nut flange of the ball screw is fixedly connected to the bottom of the feed slide. One end of the ball screw is connected to the output shaft of the servo motor via a diaphragm coupling.

[0009] Furthermore: the variable stiffness tool holder mechanism includes an outer housing fixedly connected to the top surface of the feed slide, and the interior of the outer housing is machined with a guide cavity with a rectangular cross section. An inner tool holder is slidably fitted in the guide cavity, and the front end of the inner tool holder extends out of the outer housing and is fixedly connected to a cutting blade by a pressure plate bolt.

[0010] Furthermore: a gap is left between the outer wall of the inner tool holder and the inner wall of the guide cavity of the outer shell to form a closed buffer chamber. The magnetorheological fluid in the variable stiffness tool holder mechanism is filled in the buffer chamber. The excitation coil in the variable stiffness tool holder mechanism is wound and fixed to the inner wall of the outer shell along the axial direction. The inner tool holder has a through central air channel machined inside, and the outlet of the central air channel is aligned with the back face of the cutting blade. The inlet of the central air channel is connected to a liquid nitrogen storage tank through a high-pressure hose. An electromagnetic proportional valve is installed in series on the high-pressure hose.

[0011] Furthermore, the adaptive antagonistic mechanism is arranged between the inner tool holder and the outer shell, and four hydraulic chambers are machined in a cross-shaped symmetrical distribution on the rear and sides of the inner tool holder, namely the front left hydraulic chamber, the rear right hydraulic chamber, the front right hydraulic chamber and the rear left hydraulic chamber.

[0012] Furthermore: the front left hydraulic chamber and the rear right hydraulic chamber are connected by a first cross oil pipe, and the front right hydraulic chamber and the rear left hydraulic chamber are connected by a second cross oil pipe, and the closed end of each hydraulic chamber is connected to an energy storage chamber.

[0013] Furthermore: the accumulator chamber is filled with pre-pressurized nitrogen, and the hydraulic chamber is separated from the accumulator chamber by a diaphragm with a fixed throttling orifice plate. The hydraulic chamber, the first cross oil pipe and the second cross oil pipe are all filled with hydraulic oil. A control system is also provided on one side of the outer casing, and the control system is electrically connected to the spindle motor, the servo motor, the excitation coil and the electromagnetic proportional valve respectively.

[0014] Furthermore, the control system is configured to perform the following operations: control the servo motor to drive the ball screw to drive the feed slide to radially feed the inner liner oil pipe, while simultaneously supplying a preset working current to the excitation coil to keep the electromagnetic proportional valve in a closed state; and perform interface recognition when the cutting blade is about to penetrate the outer layer of the oil pipe to be cut and enter the inner liner layer, dynamically reducing the excitation current of the excitation coil.

[0015] Furthermore, the control system is also configured to: monitor the output waveform of the servo motor and extract the characteristic value of the torque micropulse during the cutting feed process, and dynamically adjust the excitation current of the excitation coil based on the characteristic value; extract the high-frequency harmonic component of the stator current of the spindle motor, and drive the electromagnetic proportional valve to open according to the high-frequency harmonic component, releasing a high-pressure cryogenic liquid nitrogen gas flow that is injected through the central air passage onto the back face of the cutting blade.

[0016] The present invention has the following beneficial effects:

[0017] 1. This invention, by setting up a variable stiffness tool holder mechanism and a control system, enables the control system to identify the interface based on the output torque change of the servo motor when the cutting blade is about to penetrate the outer steel pipe and enter the inner lining layer. It also dynamically reduces the excitation current of the excitation coil, causing the magnetorheological fluid in the buffer chamber to switch to a flexible compliant state. This structure can effectively absorb the remaining kinetic energy of the feed system caused by the sudden drop in cutting resistance, fundamentally preventing the tool from overcutting.

[0018] 2. This invention sprays cryogenic liquid nitrogen gas onto the back face of the cutting blade through the central air channel, weakening the high toughness and adhesion properties of the inner liner. At the same time, the cross-shaped symmetrical hydraulic chambers in the adaptive antagonistic mechanism are linked with the energy storage chamber through cross oil pipes. When the blade deflects tangentially, the hydraulic oil is squeezed into the diagonal hydraulic chambers and compresses the pre-pressurized nitrogen, instantly generating a reverse support force that is transmitted back to the inner tool holder, forming a mechanical reverse cancellation, which effectively reduces the probability of inner liner cracking and tearing. Attached Figure Description

[0019] 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,

[0020] Figure 1 This is a schematic diagram of the overall structure of the device;

[0021] Figure 2 This is a schematic diagram of the internal structure of the device's bed;

[0022] Figure 3 This is a schematic diagram of the variable stiffness tool holder mechanism of the device;

[0023] Figure 4 This is a cross-sectional schematic diagram of the adaptive antagonistic mechanism of the device;

[0024] Figure 5 This is a schematic diagram of the structure of the first and second intersecting oil pipes of the device.

[0025] In the diagram: 1. Bed; 2. Spindle drive mechanism; 3. Feed drive mechanism; 4. Variable stiffness tool post mechanism; 5. Adaptive antagonistic mechanism; 6. Spindle box; 7. Double row cylindrical roller bearing; 8. Spindle; 9. Three-jaw self-centering chuck; 10. Flexible coupling; 11. Spindle motor; 12. Output shaft; 13. Linear guide; 14. Feed slide; 15. Screw bearing housing; 16. Angular contact ball bearing; 17. Ball screw; 18. Nut flange; 19. Diaphragm coupling; 20. Servo motor; 21. Housing; 22. Guide cavity; 23. Inner blade holder; 24. Pressure plate bolt; 25. Cutting blade; 26. Buffer chamber; 27. Magnetorheological fluid; 28. Excitation coil; 29. ​​Central air passage; 30. High-pressure hose; 31. Liquid nitrogen storage tank; 32. Electromagnetic proportional valve; 33. Hydraulic chamber; 34. Front left hydraulic chamber; 35. Rear right hydraulic chamber; 36. Front right hydraulic chamber; 37. Rear left hydraulic chamber; 38. First cross oil pipe; 39. Second cross oil pipe; 40. Accumulator gas chamber; 41. Pre-pressurized nitrogen; 42. Diaphragm; 43. Throttling orifice plate; 44. Hydraulic oil; 45. Control system. Detailed Implementation

[0026] 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.

[0027] Example 1:

[0028] Combination Figure 1 An automated cutting device for processing inner-lined oil pipes, comprising:

[0029] The machine bed 1, the spindle drive mechanism 2, and the feed drive mechanism 3 are provided. The spindle drive mechanism 2 is fixedly connected to one end of the machine bed 1, and the feed drive mechanism 3 is slidably connected to the middle of the machine bed 1. A variable stiffness tool post mechanism 4 is installed on the top surface of the feed drive mechanism 3. An adaptive antagonistic mechanism 5 is provided inside the variable stiffness tool post mechanism 4. The variable stiffness tool post mechanism 4 is filled with magnetorheological fluid 27 and equipped with an excitation coil 28.

[0030] The cutting device also includes a control system 45, and the feed transmission mechanism 3 includes a servo motor 20. The control system 45 performs interface recognition based on the output torque change of the servo motor 20 in the feed transmission mechanism 3, and dynamically adjusts the current of the excitation coil 28.

[0031] This embodiment addresses the significant differences in cutting resistance, thermal sensitivity, and elastic response between the outer metal layer and the inner non-metal layer of composite pipes. The bed 1 serves as the mounting base for the entire machine, supporting the spindle drive mechanism 2, feed drive mechanism 3, variable stiffness tool post mechanism 4, and adaptive antagonistic mechanism 5, and maintaining the relative positional stability between the components. The spindle drive mechanism 2 is located at one end of the bed 1, used to clamp and drive the inner lining oil pipe to rotate around its own axis, creating continuous circumferential cutting conditions at the part to be cut.

[0032] The feed transmission mechanism 3 is located in the middle of the bed 1 and slides along a predetermined guide direction. It is used to drive the variable stiffness tool post mechanism 4 to feed radially toward the inner liner oil pipe, so that the cutting edge gradually penetrates the outer layer material and approaches the inner layer material. The variable stiffness tool post mechanism 4 is installed on the top surface of the feed transmission mechanism 3. Its function is not only to provide tool mounting support, but also to provide a first preset force transmission stiffness during the cutting stage of the outer layer material, and switch to a second preset support stiffness that is less than the first preset force transmission stiffness during the cutting stage of the inner layer material, so as to reduce the residual kinetic energy transmission caused by the sudden drop in cutting resistance.

[0033] The mechanism also includes a cryogenic airflow channel to guide the low-temperature medium to the vicinity of the flank face in the cutting area, thereby changing the local mechanical state of the inner layer material. The adaptive antagonistic mechanism 5 is set inside the variable stiffness tool holder mechanism 4 or in the structural gap that cooperates with it. When the tool is subjected to periodic disturbances and tends to wobble, it establishes mechanical counter-pressure by increasing the pressure on the force side and providing reverse support on the diagonal side, thereby suppressing the additional deflection of the tool during the flexible support stage.

[0034] The above four parts are not simply superimposed, but form a joint working mechanism through the correspondence between rotary cutting, radial feed, stiffness switching, low temperature embrittlement and yaw resistance. This allows the rigidity required for outer layer cutting and the compliance required for inner layer cutting to be taken into account in the same device, reducing the probability of lining breakage, tearing and interlayer separation.

[0035] Combination Figure 2As shown, the spindle drive mechanism 2 includes a spindle box 6 fixedly connected to one end of the bed 1, and a spindle 8 is supported inside the spindle box 6 by a double row cylindrical roller bearing 7. The front flange of the spindle 8 is fixedly connected to a three-jaw self-centering chuck 9 by bolts, and the rear end of the spindle 8 is connected to the output shaft 12 of the spindle motor 11 by a plum blossom flexible coupling 10.

[0036] In this embodiment, the spindle transmission mechanism 2 adopts a combination structure of spindle box 6, spindle 8, double-row cylindrical roller bearing 7, three-jaw self-centering chuck 9, plum blossom flexible coupling 10 and spindle motor 11; the spindle box 6 is fixedly connected to one end of the bed 1, and is used to form the support housing of the spindle 8 and bear the radial load and axial additional load brought by the rotation of the tube during the cutting process;

[0037] The spindle 8 is located inside the spindle box 6 and is supported by a double-row cylindrical roller bearing 7. In this embodiment, the double-row cylindrical roller bearing 7 is used to provide radial load capacity within the rated threshold range and limit rotational runout within the preset tolerance range so as to maintain the rotational stability of the inner lining oil pipe to be cut during the cutting process and reduce the cutting thickness fluctuation caused by the rotational error of the spindle 8.

[0038] A flange is installed at the front end of the spindle 8, and the flange is fixedly connected to a three-jaw self-centering chuck 9 by bolts. The three-jaw self-centering chuck 9 is used to clamp oil pipes of different specifications, and the self-centering structure keeps the axis of the pipe consistent with the axis of the spindle 8, reducing the impact of clamping eccentricity on the cutting trajectory. The rear end of the spindle 8 is connected to the output shaft 12 of the spindle motor 11 through a flexible coupling 10. The flexible coupling 10 is used to transmit torque and absorb installation deviations within the preset tolerance range between the spindle 8 and the motor, avoiding the introduction of additional loads by rigid direct connection, while retaining a power transmission path without intermediate reduction mechanism to reduce the accumulation of backlash in the transmission chain.

[0039] The rotational power output by the spindle motor 11 is transmitted to the spindle 8 via the flexible coupling 10. The spindle 8 then drives the three-jaw self-centering chuck 9 and the inner oil pipe to rotate synchronously, thereby providing a stable circumferential motion basis for subsequent radial feed cutting. This structure makes the clamping accuracy, rotational stability and torque transmission capability work together, which is beneficial to obtaining a more stable basic signal when identifying the material interface through electrical parameters and load changes.

[0040] The feed transmission mechanism 3 includes a feed slide 14 slidably connected to the middle of the bed 1 via a linear guide rail 13, and a screw bearing seat 15 fixedly connected to the bed 1 parallel to the linear guide rail 13. A ball screw 17 is supported in the screw bearing seat 15 by an angular contact ball bearing 16. The nut flange 18 of the ball screw 17 is fixedly connected to the bottom of the feed slide 14. One end of the ball screw 17 is connected to the output shaft of the servo motor 20 via a diaphragm coupling 19.

[0041] In this embodiment, the feed transmission mechanism 3 adopts a combination of linear guide rail 13, feed slide 14, lead screw bearing seat 15, angular contact ball bearing 16, ball screw 17, nut flange 18, diaphragm coupling 19 and servo motor 20; the linear guide rail 13 is fixedly installed in the middle of the bed 1 to limit the movement direction of the feed slide 14, so that it only moves back and forth in the direction corresponding to the radial cutting of the tool; the feed slide 14 is slidably connected to the linear guide rail 13, and the variable stiffness tool post mechanism 4 is installed on the top surface of the feed slide 14. Therefore, the displacement of the feed slide 14 directly determines the cutting depth of the cutting blade 25 relative to the inner oil pipe.

[0042] A ball screw bearing seat 15 is installed on the bed 1 parallel to the linear guide rail 13. The ball screw bearing seat 15 is used to install and position the ball screw 17. The ball screw 17 is supported in the ball screw bearing seat 15 by an angular contact ball bearing 16. The angular contact ball bearing 16 is used to simultaneously bear the axial load caused by the rotation drive and the combined load transmitted by the cutting reaction force, so as to maintain the axial positioning accuracy of the ball screw 17. The nut flange 18 of the ball screw 17 is fixedly connected to the bottom of the feed slide 14. When the ball screw 17 rotates, the nut flange 18 drives the feed slide 14 to move linearly along the linear guide rail 13.

[0043] One end of the ball screw 17 is connected to the output shaft of the servo motor 20 via a diaphragm coupling 19. The diaphragm coupling 19 is used to compensate for minor deviations in the shaft system under high-response transmission conditions and maintain a preset standard torsional stiffness, so that the angular displacement output by the servo motor 20 can be accurately converted into the linear displacement of the feed slide 14 according to a preset transmission ratio. Under the command of the control system 45, the servo motor 20 outputs adjustable speed and adjustable torque, and the ball screw 17 converts this drive into a stable radial feed motion.

[0044] The transmission accuracy of the ball screw 17 meets the preset requirements, and the load change of the servo motor 20 is mapped to the change of cutting resistance. Therefore, this structure not only completes the tool feed, but also provides an execution link for the subsequent extraction of the torque micro-pulse derivative.

[0045] Combination Figure 3 As shown, the variable stiffness tool holder mechanism 4 includes an outer shell 21 fixedly connected to the top surface of the feed slide 14, and a guide cavity 22 with a rectangular cross section is machined inside the outer shell 21. An inner tool holder 23 is slidably fitted inside the guide cavity 22. The front end of the inner tool holder 23 extends out of the outer shell 21 and is fixedly connected to a cutting blade 25 by a pressure plate bolt 24.

[0046] In this embodiment, the variable stiffness tool holder mechanism 4 consists of an outer shell 21, a guide cavity 22, an inner tool holder 23, a pressure plate bolt 24, and a cutting blade 25. The outer shell 21 is fixedly connected to the top surface of the feed slide 14 and serves as a load-bearing component of the tool holder assembly, transmitting the displacement and load from the feed slide 14 to the tool support part. The outer shell 21 has a rectangular guide cavity 22 inside. The rectangular guide cavity 22 restricts the inner tool holder 23 from rotating around the axis without a predetermined direction, so that when the inner tool holder 23 is subjected to cutting load, it mainly exhibits a small relative displacement or elastic yielding in a predetermined direction.

[0047] Compared with the circular guide structure, the rectangular guide cavity 22 can provide a clear attitude constraint boundary, which is beneficial for establishing diagonal reaction force through the pressure difference of the hydraulic cavity 33. The inner tool holder 23 is slidably set in the guide cavity 22. As the execution component that directly supports the cutting blade 25, the inner tool holder 23 bears the first stage peak cutting reaction force in the outer cutting stage and undertakes the transition function between compliance buffering and yaw compensation in the inner cutting stage. The front end of the inner tool holder 23 extends out of the outer shell 21 and is fixedly connected to the cutting blade 25 by the pressure plate bolt 24.

[0048] The clamping bolt 24 is used to provide a detachable clamping force to the cutting blade 25 to accommodate the replacement requirements of different blade materials and specifications. After the cutting blade 25 is installed, its cutting edge is set towards the inner lining oil pipe to be cut, and it cuts radially into the pipe wall under the drive of the feed slide 14. This structure provides a reference support through the outer shell 21, defines the movement form of the inner tool holder 23 through the rectangular guide cavity 22, transmits the cutting load through the inner tool holder 23 and installs the cutting blade 25, thereby providing a unified structural basis for subsequent magnetorheological fluid 27 stiffening, cryogenic airflow introduction and adaptive antagonistic compensation.

[0049] A gap is left between the outer wall of the inner tool holder 23 and the inner wall of the guide cavity 22 of the outer shell 21, forming a closed buffer chamber 26. The magnetorheological fluid 27 in the variable stiffness tool holder mechanism 4 is filled into the buffer chamber 26. The excitation coil 28 in the variable stiffness tool holder mechanism 4 is wound and fixed along the axial direction to the inner wall of the outer shell 21. The inner tool holder 23 has a through central air passage 29 machined inside, and the outlet of the central air passage 29 is aligned with the back face of the cutting blade 25. The inlet of the central air passage 29 is connected to the liquid nitrogen storage tank 31 through the high pressure hose 30. An electromagnetic proportional valve 32 is installed in series on the high pressure hose 30.

[0050] In this embodiment, a predetermined gap is provided between the outer wall of the inner tool holder 23 and the inner wall of the guide cavity 22 of the outer shell 21. This gap forms a closed buffer chamber 26 under the action of the outer shell 21 and the sealing member. The buffer chamber 26 is filled with magnetorheological fluid 27. In this embodiment, magnetorheological fluid 27 refers to a suspension medium whose apparent yield stress can be adjusted after being subjected to an external magnetic field. Its special meaning is not a general vibration damping medium, but a working medium for controllable force transmission stiffness between the inner tool holder 23 and the outer shell 21.

[0051] When the excitation coil 28 is not energized, the magnetorheological fluid 27 maintains its initial shear resistance, and the inner tool holder 23 can generate limited flexible displacement relative to the outer shell 21. When the excitation coil 28 is energized with working current and forms a preset intensity magnetic field, the magnetic particles inside the magnetorheological fluid 27 form a chain structure along the direction of the magnetic field, which increases the shear force transmission stiffness between the inner tool holder 23 and the outer shell 21 to the set working threshold. The excitation coil 28 is axially wound and fixed along the inner wall of the outer shell 21 so as to apply a uniform magnetic field to the magnetorheological fluid 27 in the buffer chamber 26, reducing the stiffness response differences caused by uneven local magnetic field distribution.

[0052] The inner tool holder 23 has a through central air passage 29 machined inside, and the outlet of the central air passage 29 is aligned with the back face of the cutting blade 25. The back face is the tool face that is adjacent to the machined surface after cutting. If the temperature rises or the adhesion increases at this point, it is easy to cause the inner lining material to melt and tear. Therefore, directing the low temperature medium directly to the vicinity of the back face helps to reduce the local temperature rise. The inlet of the central air passage 29 is connected to the liquid nitrogen storage tank 31 through a high-pressure hose 30, and an electromagnetic proportional valve 32 is installed in series on the high-pressure hose 30.

[0053] The liquid nitrogen storage tank 31 is used to provide the cryogenic medium, and the electromagnetic proportional valve 32 is used to regulate the flow rate of the medium entering the central gas passage 29, so that the injection intensity corresponds to the material state change requirements. This structure integrates the stiffness adjustment path and the cryogenic treatment path in the same tool holder, so that the tool can change both the support conditions and the local cutting conditions of the inner layer material when passing through the material interface, reducing the problem that a single mechanical support or a single cooling method cannot take care of everything at the same time.

[0054] The adaptive antagonistic mechanism 5 is arranged between the inner tool holder 23 and the outer shell 21, and four hydraulic chambers 33 are machined in a cross-shaped symmetrical distribution at the rear and sides of the inner tool holder 23. The four hydraulic chambers 33 are the front left hydraulic chamber 34, the rear right hydraulic chamber 35, the front right hydraulic chamber 36 and the rear left hydraulic chamber 37.

[0055] In this embodiment, the adaptive antagonistic mechanism 5 is disposed at the corresponding position between the inner tool holder 23 and the outer shell 21, and establishes a hydraulic response by utilizing the displacement difference when the inner tool holder 23 deflects slightly relative to the outer shell 21; four hydraulic chambers 33 are machined at the rear and sides of the inner tool holder 23, and the four hydraulic chambers 33 are distributed in a cross-shaped symmetrical manner, namely the front left hydraulic chamber 34, the rear right hydraulic chamber 35, the front right hydraulic chamber 36, and the rear left hydraulic chamber 37; here, front, rear, left, and right are used to describe the relative orientation relationship corresponding to the feed direction and the lateral direction of the inner tool holder 23, and their function is to define the diagonal force path of hydraulic compensation, rather than limiting the absolute installation orientation;

[0056] The symmetrical arrangement of the four hydraulic chambers 33 allows the inner tool holder 23 to form a corresponding pressure side and anti-support side under any tangential yaw tendency. Compared with the structure with only a single elastic element, the cross-shaped symmetrical hydraulic chamber layout 33 can simultaneously respond to minute attitude changes in two orthogonal directions and transform yaw disturbances into pressure migration conditions in the diagonal direction. Since the tool holder support stiffness is reduced relative to the outer cutting stage after the cutting blade 25 enters the inner liner, the tangential component force generated by material inhomogeneity, pipe rotation fluctuation and local friction changes is more likely to cause slight deviation of the tool tip.

[0057] The distribution of the four hydraulic chambers 33 matches the orientation change direction of the inner tool holder 23, so that once the sway occurs, a volume change can be formed in the corresponding hydraulic chamber 33, providing a prerequisite for subsequent pressure transmission through cross oil pipes and establishment of reverse support; this arrangement improves the orientation suppression capability in the flexible cutting stage and reduces the kerf deviation caused by insufficient unidirectional support.

[0058] Combination Figure 5 The front left hydraulic chamber 34 and the rear right hydraulic chamber 35 are connected by the first cross oil pipe 38, and the front right hydraulic chamber 36 and the rear left hydraulic chamber 37 are connected by the second cross oil pipe 39. The closed end of each hydraulic chamber 33 is connected to an energy storage chamber 40.

[0059] In this embodiment, the front left hydraulic chamber 34 and the rear right hydraulic chamber 35 are connected by the first cross oil pipe 38, and the front right hydraulic chamber 36 and the rear left hydraulic chamber 37 are connected by the second cross oil pipe 39, thereby forming two sets of diagonal hydraulic transmission paths; the closed end of each hydraulic chamber 33 is connected to the accumulator chamber 40; the function of this structure is that when the inner tool holder 23 has a slight sway in a certain tangential direction, the hydraulic chamber 33 on the swaying retreat side is compressed, the pressure inside the chamber increases, and the hydraulic oil 44 is transmitted along the corresponding cross oil pipe to the hydraulic chamber 33 in the diagonal direction, so that the diagonal hydraulic chamber 33 pushes its corresponding accumulator chamber 40 to be pressurized;

[0060] The compressible medium in the accumulator chamber 40 has a recovery tendency after being compressed, and then the supporting force is transmitted back to the inner tool holder 23 through the hydraulic oil 44, thereby establishing a reverse counteracting force on the opposite side of the sway direction; when the cutting blade 25 is subjected to tangential resistance fluctuations and tangential sway occurs during the flexible cutting stage, the inner tool holder 23 exhibits a tilting tendency of being squeezed on the compressed side and tilted up on the diagonal side.

[0061] The hydraulic oil 44, which rises due to the decrease in volume in the hydraulic chamber 33 on the pressurized side, is directly guided to the diagonal hydraulic chamber 33 on the raised side. The pressure in the diagonal hydraulic chamber 33 increases and squeezes the accumulator gas chamber 40 outward. The pre-pressurized nitrogen gas 41 in the accumulator gas chamber 40 is compressed and generates a reverse expansion restoring force. This restoring force is transmitted back through the incompressible hydraulic oil 44 and acts precisely on the raised side of the inner tool holder 23, forming a counteracting torque opposite to the initial yaw direction, which adaptively suppresses the additional tool deflection during the flexible cutting stage. Each hydraulic chamber 33 is equipped with an accumulator gas chamber 40, which allows hydraulic force transmission to be combined with gas compression energy storage.

[0062] Hydraulic oil 44 performs the function of pressure transmission, and accumulator 40 performs the function of reverse recovery. The combination of the two enables the device to generate a corresponding counteracting force by utilizing the displacement change caused by cutting wobble without external power. This structure makes the wobble disturbance more obvious and the diagonal support more fully established, thereby improving the tool posture maintenance ability in the inner cutting stage.

[0063] Example 2:

[0064] Combination Figure 4 The accumulator chamber 40 is filled with pre-pressurized nitrogen gas 41, and the hydraulic chamber 33 is separated from the accumulator chamber 40 by a diaphragm 42 with a fixed throttling orifice plate 43. The hydraulic chamber 33, the first cross oil pipe 38 and the second cross oil pipe 39 are all filled with hydraulic oil 44. A control system 45 is also provided on one side of the outer casing 21, and the control system 45 is electrically connected to the spindle motor 11, the servo motor 20, the excitation coil 28 and the electromagnetic proportional valve 32 respectively.

[0065] In this embodiment, the energy storage chamber 40 is filled with pre-pressurized nitrogen gas 41. Pre-pressurized nitrogen gas 41 refers to a gas medium that is pre-filled and maintained within a set pressure range before the device is put into cutting. Its function is to provide an initial elastic support reference for the hydraulic compensation system, so that the hydraulic chamber 33 can maintain a stable mechanical balance when it is not subjected to obvious swaying and compression. The hydraulic chamber 33 and the energy storage chamber 40 are separated by a diaphragm 42, and a throttling orifice plate 43 is fixedly installed on the diaphragm 42.

[0066] The diaphragm 42 is used to isolate the hydraulic oil 44 from the nitrogen gas to prevent the media from mixing directly; the orifice plate 43 is used to limit the pressure exchange rate generated by the hydraulic oil 44 pushing the diaphragm 42, so that the establishment and fall of the reverse support force have controllable flow damping, and reduce the secondary oscillation caused by excessive pressure migration.

[0067] The hydraulic chamber 33 and the intersecting oil pipes are filled with hydraulic oil 44; the hydraulic oil 44 is an incompressible working medium, used to efficiently transmit the volume change of the hydraulic chamber 33 to the diagonal hydraulic chamber 33 and the accumulator 40, thereby forming a stable mechanical reverse support path; a control system 45 is set on one side of the outer casing 21, and the control system 45 is electrically connected to the spindle motor 11, the servo motor 20, the excitation coil 28 and the electromagnetic proportional valve 32 respectively;

[0068] The control system 45 receives the electrical and load parameters of the spindle motor 11 and servo motor 20 during operation and outputs control signals to the excitation coil 28 and the electromagnetic proportional valve 32 accordingly. The spindle motor 11 provides the driving force for the rotation of the tube, the servo motor 20 provides the radial feed power, the excitation coil 28 adjusts the equivalent shear resistance of the magnetorheological fluid 27, and the electromagnetic proportional valve 32 adjusts the flow rate of the cryogenic medium. The control system 45 and the mechanical-hydraulic compensation system have different functions in this embodiment. The control system 45 is responsible for interface identification and active adjustment, while the hydraulic compensation system is responsible for passive counter-support after yaw force. This enables the device to have corresponding adjustment means in both the material interface switching and inner layer continuous cutting stages.

[0069] The control system 45 has several control parameters stored in advance for real-time judgment. These control parameters are not set in isolation, but correspond to different physical meanings and subsequent control actions. The preset working current refers to the upper limit current value that the excitation coil 28 is allowed to continuously apply during the outer steel pipe cutting stage. Its function is to make the magnetorheological fluid 27 in the buffer chamber 26 enter a high shear yield stress state in order to establish the high stiffness support conditions required for the outer cutting.

[0070] The upper limit current can be determined by a combination of no-load energization test, shear response calibration of magnetorheological fluid 27 sample and tool holder displacement response calibration. The determination principle is: under the premise of not overheating and not causing coil insulation risk, the slight displacement of the inner tool holder 23 relative to the outer shell 21 is suppressed within a predetermined range.

[0071] The flexible compliant state refers to the working state in which the magnetorheological fluid 27 changes from a high shear resistance state to a low shear resistance state after the excitation current of the excitation coil 28 is reduced, allowing the inner tool holder 23 to produce controlled micro-displacement relative to the outer shell 21. This state does not completely lose support, but allows the tool holder to retain basic guiding ability, while reducing the risk of forward overcutting after material interface penetration.

[0072] The elastic modulus change requirement of the lining material is a target adjustment quantity used inside the control system 45. It is used to represent the degree of local low temperature adjustment required for the current cutting area to achieve a state where it is easier to break apart. It is not the absolute modulus value of the material body that is directly measured, but the relative control requirement level obtained by mapping the characteristics of the electrical signal.

[0073] The demand level can be divided into at least a first interval, a second interval, and a third interval, which correspond to the first preset opening, the second preset opening, and the third preset opening of the electromagnetic proportional valve 32, respectively, and the flow cross-sectional area of ​​the first preset opening, the second preset opening, and the third preset opening increases sequentially.

[0074] The set pressure range of pre-pressurized nitrogen 41, the throttling capacity of the orifice plate 43, and the viscosity of the hydraulic oil 44 jointly determine the response speed and support amplitude of the passive antagonistic system. The higher the pressure of pre-pressurized nitrogen 41, the stronger the initial anti-support reference; the more obvious the throttling effect, the smoother the establishment of the anti-support force. The above parameters can be tuned through no-load swing test and simulated cutting disturbance test: first, apply a micro-displacement disturbance with known direction and amplitude in the non-cutting state, observe the recovery time, recovery overshoot and residual amplitude of the inner tool holder 23, and then make matching corrections to the pressure of pre-pressurized nitrogen 41 and the orifice diameter of the orifice plate 43 until a parameter combination that meets the attitude suppression requirements and does not introduce obvious secondary oscillations is obtained.

[0075] Thus, a corresponding and tunable logical relationship is formed between the electrical control parameters in the control system 45 and the initial mechanical parameters in the hydraulic compensation system, providing a clear basis for interface identification, stiffness switching and low-temperature flow regulation in subsequent steps.

[0076] The control system 45 is configured to perform the following operations: control the servo motor 20 to drive the ball screw 17 to drive the feed slide 14 to feed radially into the inner liner of the oil pipe, and simultaneously supply a preset working current to the excitation coil 28 to keep the electromagnetic proportional valve 32 in the closed state; when the cutting blade 25 is about to penetrate the outer layer of the oil pipe to be cut and enter the inner liner, perform interface recognition and dynamically reduce the excitation current of the excitation coil 28.

[0077] In this embodiment, the operation of the control system 45 corresponds item by item to the mechanical structure of the device; the outer steel pipe is cut and controlled; the servo motor 20 drives the ball screw 17 to rotate, and the ball screw 17 drives the feed slide 14 to feed radially towards the inner oil pipe through the nut flange 18; since the outer steel pipe has high cutting resistance, the control system 45 supplies the working current within the set upper limit range to the excitation coil 28, so that the magnetic field strength in the buffer chamber 26 is kept at a high level, the magnetorheological fluid 27 exhibits the first preset shear yield stress state, and the relative displacement between the inner tool holder 23 and the outer shell 21 is suppressed, thereby forming a high-rigidity force transmission condition suitable for steel layer cutting; in this stage, the electromagnetic proportional valve 32 remains closed, and the central air passage 29 does not output cryogenic medium to avoid introducing unnecessary low-temperature consumption in the steel layer cutting stage;

[0078] Penetration identification and stiffness switching control; the control system 45 continuously monitors the load change of the servo motor 20. When it identifies that the cutting blade 25 is close to penetrating the outer steel pipe, it dynamically reduces the excitation current of the excitation coil 28. After the excitation current is reduced, the equivalent shear resistance of the magnetorheological fluid 27 decreases accordingly. The inner tool holder 23 and the outer shell 21 switch from the first preset stiffness support to the flexible compliant support, so as to absorb the forward tendency of the outer material after the cutting resistance of the outer material is weakened and still remain in the feed chain.

[0079] Cryogenic airflow and material embrittlement control; the control system 45 outputs a corresponding electromagnetic proportional valve 32 opening control signal according to the characteristic quantity reflecting the change in the state of the inner layer material, so that the high-pressure cryogenic medium in the liquid nitrogen storage tank 31 enters the high-pressure hose 30 and is sprayed into the area near the back face of the cutting blade 25 through the central air channel 29; after the inner layer material is locally cooled, its high toughness and easy adhesion characteristics are weakened, and the cutting fracture mode changes to the state of reaching the preset brittle fracture separation standard.

[0080] Inner liner cutting and adaptive antagonistic control: When cutting the inner liner under flexible support, if the cutting blade 25 is affected by radial resistance fluctuations and undergoes tangential deflection, the volume of the hydraulic chamber 33 on the deflection relief side decreases. The hydraulic oil 44 enters the diagonal hydraulic chamber 33 through the cross oil pipe and pushes the corresponding accumulator 40 to be pressurized. The pre-pressurized nitrogen 41 in the accumulator 40 is further compressed, thereby forming a reverse support force, which is then transmitted back to the inner tool holder 23 through the hydraulic oil 44 to achieve mechanical counter-impact opposite to the deflection direction. In this step, active control and passive antagonism coexist. Active control is responsible for interface transition and material state adjustment, while passive antagonism is responsible for attitude suppression in continuous cutting, so that the cutting blade 25 has both compliance and stability in the inner layer cutting stage.

[0081] The startup sequence and switching conditions in the control system 45 are continuously related, rather than independent of each other; the input signals include at least the current position of the servo motor 20, the current output torque, the speed of the spindle motor 11, and the current current value of the excitation coil 28. The control system 45 only allows the output of the preset working current to the excitation coil 28 and the execution of steel layer cutting feed after confirming that the speed of the spindle 8 is stable and the feed slide 14 is in the initial feed range.

[0082] The triggering condition originates from the load fluctuation signal of the servo motor 20 continuously collected during the period. When the load fluctuation signal shows a change trend that conforms to the interface approach characteristics, the control system 45 does not immediately unload the stiffness all at once. Instead, it first generates an interface approach flag and then performs a short-term verification of the flag according to a preset time window or a preset feed displacement window. There may be local material inhomogeneity, hard spots or wall thickness tolerances inside the outer steel pipe of the inner oil pipe. These local defects will also cause a sudden drop in the load of the servo motor 20 during cutting. If the control system 45 unloads the stiffness immediately based on a single load drop, it will cause the tool holder to enter the flexible state in advance, which will cause tool vibration or tool breakage risk exceeding the safety threshold during steel layer cutting.

[0083] Therefore, by introducing a short-time verification mechanism based on a preset time window or displacement window, the control system 45 only confirms that the load drop characteristic has been reached when it continues to exist during the verification period and exceeds the typical size characteristics of the local defect, thereby safely executing the excitation current reduction action and effectively avoiding misjudgment caused by a single local defect or instantaneous vibration.

[0084] The cryogenic airflow and material embrittlement control module logically follows the interface recognition program. Its inputs include not only the interface recognition results but also the high-frequency disturbance characteristics extracted from the current signal of the spindle motor 11 and the current opening state of the electromagnetic proportional valve 32. The control system 45 only increases the valve opening step by step according to the requirements of the inner lining material after confirming that the inner layer cutting has started or is about to start, so that the release of cryogenic airflow and interface switching are synchronized. It does not rely on separate electrical control triggering but passively engages the mechanical hydraulic compensation path when cutting disturbances occur after the formation of flexible compliant support and low temperature regulation conditions.

[0085] The output results and their flow direction of each step also have a clear correspondence; the output result is a high-rigidity cutting support state, which directly acts on the inner tool holder 23 and the cutting blade 25 to stabilize the cutting of the outer steel pipe; the output result is the interface proximity judgment result and the reduced excitation coil 28 control quantity, the former serving as an important input for whether to allow the opening of the cryogenic airflow, and the latter directly changing the force transmission state of the magnetorheological fluid 27.

[0086] The output results are the opening degree of the electromagnetic proportional valve 32 and the corresponding cryogenic airflow rate, which directly affects the area near the flank face of the cutting blade 25 to change the local cutting properties of the inner layer material; the output results are the reverse support force formed by the hydraulic chamber 33, the cross oil pipe and the accumulator 40, which directly feeds back to the attitude of the inner tool holder 23; through the above step-by-step input, step-by-step judgment and step-by-step output relationship, the interface recognition-stiffness switching-cryogenic adjustment-passive antagonism in the control system 45 forms a sequential processing link, thereby avoiding the control process from only staying at the result description without intermediate logic.

[0087] The control system 45 is also configured to: monitor the output waveform of the servo motor 20 and extract the characteristic value of the torque micropulse during the cutting feed process, and dynamically adjust the excitation current of the excitation coil 28 based on the characteristic value; extract the high-frequency harmonic component of the stator current of the spindle motor 11, and drive the electromagnetic proportional valve 32 to open according to the high-frequency harmonic component, so as to release the high-pressure cryogenic liquid nitrogen gas flow through the central air passage 29 to the back face of the cutting blade 25;

[0088] In this embodiment, it is further refined into an executable data processing and control process; in the interface recognition and data extraction stage, the control system 45 continuously reads the output torque-related parameters from the servo motor 20 drive unit; in this embodiment, the torque micropulse refers to the short-period minute fluctuation component superimposed on the average load during the feeding process, which can reflect the change in the contact state between the tool tip and the material; the control system 45 performs derivative processing on the continuously collected torque data to obtain the first derivative sequence of the torque micropulse;

[0089] When the cutting blade 25 is in the continuous cutting stage of the outer steel pipe, the torque change is generally constrained by a high cutting resistance. When the blade tip approaches the penetration of the outer steel pipe and transitions to the inner material, the cutting resistance will show a rapid attenuation trend, and the first derivative will change from a positive value to a negative extreme value. The control system 45 determines the derivative distortion interval based on this, and performs frequency domain transformation processing on the interval to extract its frequency domain envelope area. The frequency domain envelope area is used to characterize the energy change magnitude corresponding to this resistance mutation.

[0090] During the stiffness unloading calculation and execution stage, the control system 45 multiplies the frequency domain envelope area by the conversion factor related to structural damping to obtain the step attenuation value of the cutting resistance. The conversion factor related to structural damping can be obtained through device no-load calibration, standard test piece cutting calibration or empirical correction. Its function is to convert the change in electric drive load into the change in resistance corresponding to the mechanical system response.

[0091] The control system 45 then calculates the inertia parameters of the feed transmission mechanism 3. The inertia parameters include the equivalent inertia of the feed slide 14, the inner tool post 23 and the synchronously moving parts therewith, which are used to evaluate the possible forward thrust tendency under the current feed state. Based on the step decay value of the cutting resistance and the inertia parameters, the control system 45 obtains the structural stiffness unloading equivalent.

[0092] In this embodiment, the structural stiffness unloading equivalent refers to the control amount corresponding to the reduction in support stiffness required to offset the continued forward movement of the tool tip, rather than an independent mechanical component parameter. The control system 45 converts this equivalent into the pulse width modulation duty cycle of the excitation coil 28. By adjusting the duty cycle, the average excitation current of the excitation coil 28 is reduced, causing the shear yield stress of the magnetorheological fluid 27 to decrease accordingly, and the inner tool holder 23 enters a flexible compliant support state.

[0093] During the harmonic monitoring and modulus conversion stage, the control system 45 synchronously acquires the stator current signal of the spindle motor 11 and extracts the high-frequency harmonic components. In this embodiment, the high-frequency harmonic components are used to reflect the electromagnetic load disturbance caused by the change in cutting contact state, and their energy jump value can characterize the change in the interaction mode between the tool and the inner layer material. The control system 45 performs energy calculation on the high-frequency harmonic components and uses the energy difference within adjacent system cycles as the energy jump value.

[0094] The energy jump value corresponds to the pre-established material response mapping relationship and is used to calculate the elastic modulus change requirement of the lining material. The elastic modulus change requirement here is not a direct measurement of the material's intrinsic parameters, but refers to the degree of local low temperature regulation required to make the material in the cutting area easier to cut. The elastic modulus change requirement is equivalent to the target cooling control equivalent in the control logic and is used to establish a closed-loop mapping between the micro-cutting characteristics and the deep cryogenic airflow compensation amount. In the valve opening and airflow control stage, the control system 45 generates the opening control signal of the electromagnetic proportional valve 32 according to the elastic modulus change requirement.

[0095] The electromagnetic proportional valve 32 adjusts the flow cross-sectional area under the action of the control signal, so that the high-pressure cryogenic liquid nitrogen gas flow in the liquid nitrogen storage tank 31 enters the high-pressure hose 30 at a corresponding flow rate and is sprayed to the back face of the cutting blade 25 through the central air channel 29. As the spray flow rate changes, the local cooling capacity of the cutting area changes accordingly, so that the inner layer material changes from a state of high toughness and easy adhesion to a separable state that meets the set embrittlement fracture threshold.

[0096] There is a corresponding relationship between torque derivative identification and stiffness unloading, harmonic monitoring and cryogenic flow regulation. The former deals with the problem of tool support state switching, and the latter deals with the problem of adjusting the local cutting properties of the inner material. Both are completed by the control system 45 based on real-time acquired signals, so that mechanical structure response and material state adjustment are achieved in the same cutting process.

[0097] Interface recognition and data extraction are performed in the following order: the control system 45 continuously reads the output torque data fed back by the servo motor 20 driver at a fixed sampling period and records the corresponding sampling time at the same time; the continuous torque data is processed by moving average to separate the average component that characterizes the overall cutting load change and the short-period fluctuation component superimposed on it, wherein the short-period fluctuation component is defined as torque micropulse;

[0098] The control system 45 calculates the first derivative of the torque micropulse according to the differential method of adjacent sampling points. If the first derivative of multiple consecutive sampling points first maintains a positive change, then quickly turns negative and a local minimum occurs, and the absolute value of the local minimum is greater than the preset resistance attenuation judgment threshold, the judgment threshold is obtained and written in advance by the system based on the previous no-load and cutting resistance calibration experiments on the standard inner-lined oil pipe sample. The specific rule is: extract the extreme value of the first derivative of the cutting resistance at the moment when the cutting blade penetrates the outer layer in the calibration experiment, and take the average absolute value of multiple calibration extreme values ​​as the resistance attenuation judgment threshold.

[0099] Then mark the time period as the candidate derivative distortion interval; perform frequency domain transformation on the data in the candidate interval, extract the envelope curve formed by the outer edge of the main frequency band, and then accumulate the area covered by the envelope curve to obtain the frequency domain envelope area.

[0100] The frequency domain envelope area here is an intermediate characteristic quantity used to characterize the intensity of sudden changes in cutting resistance. The larger the value, the more obvious the resistance attenuation when the outer steel pipe is about to be penetrated. The control system 45 applies a fast Fourier transform to the data in the candidate interval to obtain the amplitude frequency sequence and sets the effective frequency band to filter out overall load changes and high-frequency electrical noise.

[0101] Within the effective frequency band, local amplitude maxima at each discrete frequency point are extracted using a peak-finding algorithm. Spline interpolation is then applied to these maxima points to form a frequency domain envelope curve. The area under this curve is calculated using the trapezoidal numerical integration method, which is the aforementioned frequency domain envelope area. This process clarifies the numerical conversion path from time-domain torque to frequency-domain characteristics. Its output flows to the stiffness unloading calculation module and serves as the direct input for subsequent calculation of the step attenuation value of cutting resistance.

[0102] The stiffness unloading calculation and execution does not directly derive the final control result from a single characteristic quantity, but rather goes through three stages sequentially: characteristic quantity conversion, forward risk assessment, and control quantity output. The control system 45 first multiplies the frequency domain envelope area with the pre-calibrated structural damping related conversion coefficient to obtain the step attenuation value of the cutting resistance. The calculation formula is as follows:

[0103]

[0104] in, For conversion factors, The frequency domain envelope area; the physical meaning of this conversion factor is to convert the observable characteristic changes on the electric drive side into the resistance changes on the mechanical cutting side, and its source can be a calibration table established after repeated cutting of a standard specimen; the control system 45 reads the current feed rate. Equivalent moving mass of feed slide 14 The equivalent inertia parameters of the ball screw 17 transmission chain are used to evaluate the tendency of the tool tip to continue its forward movement due to a sudden decrease in resistance; at this time, the equivalent moving mass of the feed slide 14 is calculated using the kinetic energy absorption balance equation. , is the sum of the physical mass of the feed slide 14, the inner tool post 23 and their synchronous moving parts and the equivalent inertia of the ball screw 17 transmission chain converted to the linear feed direction;

[0105] The structural stiffness unloading equivalent is the control target quantity generated based on this assessment. It represents the extent to which the support stiffness of the magnetorheological fluid 27 needs to be reduced in order to absorb the aforementioned forward thrust trend. During the forward thrust risk assessment stage, a dynamic stiffness unloading calculation model for quantifying support requirements actually runs inside the control system 45. The purpose of this model is to accurately estimate the amount of support stiffness reduction required to just absorb the remaining kinetic energy of the feed system at the instant of a sudden drop in cutting resistance, so as to avoid feed runaway caused by the support stiffness being lower than the preset lower limit, or lining tearing caused by the support stiffness being higher than the preset upper limit.

[0106] In terms of logical structure and data flow, this model receives the step decay value of the aforementioned cutting resistance. The inertia parameters of the feed transmission mechanism 3 are used as input, combined with a preset safe displacement threshold. Average cutting resistance extracted by moving average before mutation The required stiffness is calculated using the kinetic energy absorption balance equation. Among them, the preset safe displacement threshold It is determined jointly based on the liner thickness of the tubing to be cut and the maximum allowable overcutting error, to ensure that the forward displacement of the blade is limited within the geometric boundaries of the effective pipe wall without piercing or tearing the liner during sudden changes in resistance; the equation is:

[0107]

[0108] The structural stiffness unloading equivalent is the sum of the current high stiffness and the required stiffness. The difference; the model outputs this equivalent to the duty cycle mapping module; in terms of the physical relationship represented, the model as a whole simulates the dynamic mechanical dissipation process in which the kinetic energy retained by the feed system due to inertia is converted into heat energy and potential energy by the shear friction and elastic yielding of the magnetorheological fluid 27 between the inner tool holder 23 and the outer shell 21 when the cutting resistance decays instantaneously.

[0109] The control system 45 does not require the operator to directly input the equivalent value. Instead, it queries a pre-established stiffness unloading equivalent-duty cycle correspondence table, converts it into the pulse width modulation duty cycle of the excitation coil 28, and then outputs it to the excitation coil 28 drive unit for execution. If the interface near-disappearance feature or the derivative distortion condition is no longer met in the next sampling window, the control system 45 maintains the current duty cycle and does not continue to decrease, thereby avoiding repeated unloading that would cause the tool holder to become too soft.

[0110] Harmonic monitoring and modulus conversion are performed in the following order: The control system 45 synchronously acquires the original waveform of the stator current of the spindle motor 11 and segments it according to the time window that matches the speed of the spindle 8; in each time window, the fundamental wave and low-order conventional torque components are filtered out, and the high-frequency harmonic components that are more closely related to the changes in the cutting contact state are retained. The lower limit of the effective frequency band of the high-frequency harmonic components avoids the fundamental wave of the spindle motor 11 and the basic vibration frequency of the mechanical body, and the effective frequency band covers the characteristic response frequency band excited by the micro-adhesion and tearing cycle between the tool and the non-metallic lining material; the energy value of the retained high-frequency harmonic components is calculated and the difference is made with the energy value of the previous time window to obtain the energy jump value.

[0111] Within the time window, the control system 45 performs numerical integration of the square of the high-frequency harmonic current and calculates the average value to obtain the current energy value. Then, by subtracting the energy value of the previous time window, the energy jump value is calculated. The energy jump value is a judgment quantity that characterizes whether the contact state between the tool and the inner liner material has changed significantly. When the value enters the first preset energy characteristic range, it indicates that the inner liner material still exhibits toughness characteristics or adhesion characteristics higher than the first threshold, and the local deep cryogenic intensity needs to be increased. When the value enters the second preset energy characteristic range, it indicates that the current cutting state has reached the preset brittle fracture separation standard, and the deep cryogenic flow rate can be maintained or appropriately reduced.

[0112] Based on this, the control system 45 calls the pre-established energy jump value-elastic modulus change demand level mapping table to convert the energy jump value into a certain demand level of low, medium, or high. This mapping table can be obtained in advance by performing trial cuts on known lining material samples and recording the cutting state under different low temperature flow rates.

[0113] The mapping table and related conversion process essentially constitute a material state response evaluation model. Its specific logic is as follows: the harmonic energy when the lining material reaches the preset separation standard is extracted in advance as the benchmark value, the deviation ratio between the energy jump value and the benchmark value is calculated in real time, and the range is set according to this ratio to divide low, medium and high demand levels.

[0114] The purpose of this model is to evaluate the local cutting properties of the inner lining material by observing the small perturbations on the electrically driven side of the spindle 8 when the real-time physical modulus of the inner non-metallic material cannot be directly measured. In terms of logic structure and data flow, the model receives the energy jump value of the high-frequency harmonic component as a single feature input, and discretizes the continuously changing energy jump value through the internally preset multi-level threshold comparator, thereby outputting the corresponding elastic modulus change requirement level.

[0115] In terms of the physical relationships represented, the model abstracts the influence of the toughness and adhesion properties of the liner material at different temperatures on the cutting resistance of the tool tip. That is, the softer the material and the stronger the adhesion, the higher the frequency and amplitude of the micro-adhesion-tear cycle during the tool tip cutting process, thereby exciting higher energy harmonic components in the stator current of the spindle motor 11. Conversely, when the material is effectively embrittled by the cryogenic airflow, the cutting is in a brittle fracture separation state, the micro-adhesion phenomenon is weakened, and the high-frequency harmonic energy decreases significantly.

[0116] The valve opening and airflow control are executed according to the above-mentioned demand levels. If the elastic modulus change demand is low, the control system 45 outputs a corresponding small opening control signal to keep the electromagnetic proportional valve 32 at the basic injection flow rate. If it is medium, a medium opening control signal is output to enhance the cooling capacity near the back face. If it is high, a large opening control signal is output to make the high-pressure cryogenic liquid nitrogen gas flow quickly enter the central air passage 29 and be concentrated and injected into the area near the back face of the cutting blade 25.

[0117] After each control cycle, the control system 45 rereads the stator current of the spindle motor 11 and the torque signal of the servo motor 20, and repeats the above processing flow to form a closed-loop logic of acquisition, extraction, judgment, execution and verification. Through the above decomposition, the first derivative of the torque micropulse, the derivative distortion interval, the frequency domain envelope area, the step attenuation value of cutting resistance, the structural stiffness unloading equivalent, the energy jump value, and the elastic modulus change requirement all have clear physical meanings, source paths and decision-making roles, avoiding the control algorithm from being presented only in result terms without intermediate processing basis.

[0118] 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. An automated cutting device for processing inner-lined oil pipes, comprising: The bed (1), spindle drive mechanism (2), and feed drive mechanism (3) are characterized in that: One end of the bed (1) is fixedly connected to a spindle transmission mechanism (2), and the middle part of the bed (1) is slidably connected to a feed transmission mechanism (3). A variable stiffness tool post mechanism (4) is installed on the top surface of the feed transmission mechanism (3), and an adaptive antagonistic mechanism (5) is provided inside the variable stiffness tool post mechanism (4). The variable stiffness tool post mechanism (4) is filled with magnetorheological fluid (27) and equipped with an excitation coil (28). The cutting device also includes a control system (45), and the feed transmission mechanism (3) includes a servo motor (20); the control system (45) performs interface recognition based on the output torque change of the servo motor (20) in the feed transmission mechanism (3) and dynamically adjusts the current of the excitation coil (28).

2. The automated cutting device for processing inner-lined oil pipes according to claim 1, characterized in that: The spindle drive mechanism (2) includes a spindle box (6) fixedly connected to one end of the bed (1), and the spindle (8) is supported inside the spindle box (6) by a double-row cylindrical roller bearing (7). The front flange of the spindle (8) is fixedly connected to a three-jaw self-centering chuck (9) by bolts. The rear end of the spindle (8) is connected to the output shaft (12) of the spindle motor (11) by a plum blossom flexible coupling (10).

3. The automated cutting device for processing inner-lined oil pipes according to claim 2, characterized in that: The feed transmission mechanism (3) includes a feed slide (14) slidably connected to the middle of the bed (1) via a linear guide rail (13), and a screw bearing seat (15) is fixedly connected to the bed (1) parallel to the linear guide rail (13). A ball screw (17) is supported in the screw bearing seat (15) by an angular contact ball bearing (16). The nut flange (18) of the ball screw (17) is fixedly connected to the bottom of the feed slide (14). One end of the ball screw (17) is connected to the output shaft of the servo motor (20) via a diaphragm coupling (19).

4. The automated cutting device for processing inner-lined oil pipes according to claim 3, characterized in that: The variable stiffness tool holder mechanism (4) includes an outer shell (21) fixedly connected to the top surface of the feed slide (14), and the outer shell (21) has a guide cavity (22) with a rectangular cross section. An inner tool holder (23) is slidably fitted in the guide cavity (22). The front end of the inner tool holder (23) extends out of the outer shell (21) and is fixedly connected to a cutting blade (25) by a pressure plate bolt (24).

5. The automated cutting device for processing inner-lined oil pipes according to claim 4, characterized in that: A gap is left between the outer wall of the inner tool holder (23) and the inner wall of the guide cavity (22) of the outer shell (21) to form a closed buffer chamber (26). The magnetorheological fluid (27) in the variable stiffness tool holder mechanism (4) is filled into the buffer chamber (26). The excitation coil (28) in the variable stiffness tool holder mechanism (4) is axially wound and fixed to the inner wall of the outer shell (21). The inner tool holder (23) has a through central air passage (29) machined inside, and the outlet of the central air passage (29) is aligned with the back face of the cutting blade (25). The inlet of the central air passage (29) is connected to a liquid nitrogen storage tank (31) through a high-pressure hose (30). An electromagnetic proportional valve (32) is installed in series on the high-pressure hose (30).

6. The automated cutting device for processing inner-lined oil pipes according to claim 5, characterized in that: The adaptive antagonistic mechanism (5) is arranged between the inner tool holder (23) and the outer shell (21), and four hydraulic chambers (33) are machined in a cross-shaped symmetrical distribution on the rear and sides of the inner tool holder (23). The four hydraulic chambers (33) are the front left hydraulic chamber (34), the rear right hydraulic chamber (35), the front right hydraulic chamber (36), and the rear left hydraulic chamber (37).

7. An automated cutting device for processing inner-lined oil pipes according to claim 6, characterized in that: The front left hydraulic chamber (34) and the rear right hydraulic chamber (35) are connected by a first cross oil pipe (38), and the front right hydraulic chamber (36) and the rear left hydraulic chamber (37) are connected by a second cross oil pipe (39). Each hydraulic chamber (33) has a closed end connected to an energy storage chamber (40).

8. An automated cutting device for processing inner-lined oil pipes according to claim 7, characterized in that: The energy storage chamber (40) is filled with pre-pressurized nitrogen (41), and the hydraulic chamber (33) is separated from the energy storage chamber (40) by a diaphragm (42) with a fixed throttling plate (43). The hydraulic chamber (33), the first cross oil pipe (38) and the second cross oil pipe (39) are all filled with hydraulic oil (44). A control system (45) is also provided on one side of the outer shell (21), and the control system (45) is electrically connected to the spindle motor (11), the servo motor (20), the excitation coil (28) and the electromagnetic proportional valve (32).

9. An automated cutting device for processing inner-lined oil pipes according to claim 8, characterized in that: The control system (45) is configured to perform the following operations: control the servo motor (20) to drive the ball screw (17) to drive the feed slide (14) to feed radially into the inner liner oil pipe, and simultaneously supply a preset working current to the excitation coil (28) to keep the electromagnetic proportional valve (32) in a closed state; when the cutting blade (25) is about to penetrate the outer layer of the oil pipe to be cut and enter the inner liner layer, perform interface identification and dynamically reduce the excitation current of the excitation coil (28).

10. An automated cutting device for processing inner-lined oil pipes according to claim 9, characterized in that: The control system (45) is also configured to: monitor the output waveform of the servo motor (20) and extract the characteristic value of the torque micropulse during the cutting feed process, and dynamically adjust the excitation current of the excitation coil (28) based on the characteristic value; extract the high-frequency harmonic component of the stator current of the spindle motor (11), and drive the electromagnetic proportional valve (32) to open according to the high-frequency harmonic component, so as to release the high-pressure cryogenic liquid nitrogen gas flow through the central air passage (29) and spray it onto the back face of the cutting blade (25).

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