A damping boring bar with built-in stiffness-damping variable damper

Abstract

This invention discloses a vibration-damping boring bar with a built-in variable stiffness damper, comprising a cutting head, a connecting cover, a boring bar body, an electromagnet, an oscillator, a cantilever rod, a sliding support, a cantilever seat, a connecting rod, a pusher, a lead screw, a coupling, a motor base, a stepper motor, an intelligent control unit, and an acceleration sensor. An electromagnet is installed in the cavity at the front end of the boring bar body, with an axial gap between the electromagnet and the oscillator. The magnitude of the eddy current damping of the oscillator is controlled by the voltage. The other end of the oscillator is a cantilever rod, which passes through the sliding support and connects to the cantilever seat. The cantilever seat is fixedly connected to the boring bar. The motor controls the position of the sliding support, changing the cantilever rod's extension and thus altering the oscillator's stiffness. The acceleration sensor is located outside the boring bar, on one side of the cutting head. The intelligent control unit analyzes vibration signals and adjusts the motor rotation angle and electromagnet voltage to control the damping and stiffness of the oscillator system, achieving optimal vibration reduction. This invention is used for deep hole machining.

Description

Technical Field

[0001] This invention relates to a vibration damping boring bar with a built-in variable stiffness damper and its control method, belonging to the field of cutting and machining technology. Background Technology

[0002] Boring is an important metal removal process in the mechanical manufacturing industry, and it is currently the main method for machining deep-hole shaft parts. It plays an irreplaceable role in aerospace, precision machinery, instrumentation, and engine manufacturing. During boring, the changing cutting forces between the workpiece and the tool cause continuous vibration in the tool. When the hole is deep, the tool holder overhang is long, reducing stiffness, and the machine tool-tool-workpiece system will generate strong self-excited vibration. When the frequency of the excitation force is close to the natural frequency of the tool holder, chatter is particularly severe, seriously affecting the machining quality.

[0003] Enterprises and scholars have designed vibration-damping boring bars with built-in vibrator absorbers. Some scholars have also designed vibration-damping boring bars with vibrator absorbers that have adjustable stiffness and damping. However, the implementation of such designs requires the addition of piezoelectric crystals or brake components and stepper motors to the limited cavity inside the boring bar to adjust the parameters. For example, patent document CN113814432A, published on December 21, 2021, discloses a stiffness and damping adjustable vibration damping boring bar and its control method. The boring bar has a front-end open cavity, and a cutter head connector is provided at the front-end opening of the cavity. The fixed end of the cantilever beam is located at the center point of the inner wall of the cutter head connector. The mass block is a cylinder with a central through hole. The left end of the mass block is sleeved on the suspended end of the cantilever beam and can move along the axial direction of the cantilever beam. An iron block is provided on the right end face of the mass block. An electromagnet and the iron block are coaxially opposite each other, and there is an axial gap between them. When the electromagnet is energized, an attraction force is generated between it and the iron block, thereby realizing damping and vibration reduction. The damping magnitude is adjusted by controlling the voltage value at both ends of the electromagnet. For example, patent document CN114535633A, published on May 27, 2022, discloses a rotary variable stiffness and variable damping vibration damping boring bar. A support sleeve is inserted into the front end of the boring bar cavity. The front end of a rectangular cantilever beam is fixed to the output shaft of a stepper motor and fitted with a sleeve. An outer shell is provided between the inner wall of the rear end of the support sleeve and the outer wall of the sleeve. A brake assembly is installed along the circumferential direction on the inner wall of the outer shell through multiple evenly distributed grooves. An electromagnet is fixed to the bottom of the boring bar cavity. The stepper motor, brake assembly, and electromagnet are all electrically connected to the control system. Clearly, this design is difficult to operate in actual engineering, and its structure also presents problems such as inconvenient control, slow response, and inaccurate precision. Based on these problems, this invention proposes a vibration damping boring bar with a built-in variable stiffness and damping damper and its control method. Summary of the Invention

[0004] In response to the aforementioned existing technology, and in order to solve the problem that the long overhanging tool bar has a large vibration amplitude during the machining process, which in turn affects the machining efficiency and the surface quality of the machined material, this invention designs a vibration-damping boring bar with a built-in variable stiffness damper.

[0005] To address the aforementioned technical problems, this invention proposes a vibration-damping boring bar with a built-in variable stiffness damping damper, comprising a boring bar body, a cutter head, and an intelligent control unit; the front part of the boring bar body has a cavity, and the rear part of the boring bar body has a coaxial shaft hole communicating with the cavity; the cutter head is mounted at the cavity port of the boring bar body via a connecting cover; within the cavity, along the axial direction of the boring bar body, from front to back, are arranged an electromagnet, an oscillator, a sliding support, a cantilever seat, and a pusher; the electromagnet is fixedly connected to the connecting cover, the cantilever seat is fixed to the boring bar body, and the sliding support and... Each cantilever base has a central hole, and the pusher body has a central threaded hole. A cantilever rod is fixed to the cantilever base through the central hole. The vibrator is fixed to the cantilever rod, and there is an air gap of no more than 3mm between the electromagnet and the vibrator. The sliding support slides with the cantilever rod through the central hole. A lead screw is installed in the shaft hole, with its front end engaging the central threaded hole of the pusher body. The rear end of the lead screw is connected to the output end of the stepper motor via a coupling. The sliding support, cantilever base, and pusher body each have N+M through holes arranged circumferentially around the central axis. N through holes are for balancing air pressure, and M are for connecting rods, where N and M are both ≥ 2. The axes of the M connecting rod holes on the sliding support, cantilever seat, and pusher body are respectively coincident, and a connecting rod passes through each connecting rod hole. The sliding support and the pusher body are respectively fixed to both ends of the connecting rod. The diameter of the connecting rod hole on the cantilever seat is larger than the diameter of the connecting rod. An acceleration sensor is provided on the outer wall of the boring bar body located on one side of the cutter head. The acceleration sensor, electromagnet, and stepper motor are all connected to the intelligent control unit. The intelligent control unit includes a central... The system includes an accelerometer signal acquisition card, a DC electromagnet voltage controller, and a stepper motor controller. The central processing unit includes a stiffness and damping control program. By analyzing the signal from the accelerometer, the current excitation frequency is extracted. Based on the excitation frequency-vibration amplitude function of the two-degree-of-freedom system dynamics model, the stiffness and damping values ​​of the oscillator that minimize the vibration amplitude at the current excitation frequency are obtained. By adjusting the voltage of the electromagnet and the rotation angle of the stepper motor, the damping and stiffness of the oscillator are adjusted to the values ​​that minimize the vibration amplitude at the current excitation frequency.

[0006] Furthermore, in the vibration-damping boring bar described in this invention, wherein,

[0007] The electromagnet is fixed to the connecting cover by bolts. The connecting cover has a reserved hole, through which the wire of the electromagnet passes and is connected to the intelligent control unit.

[0008] The rear end of the boring bar body is provided with a motor connecting frame, and the stepper motor is fixed on the motor connecting frame.

[0009] The cantilever seat is positioned and fixed to the boring bar body by two radial set screws.

[0010] The electromagnet includes an excitation coil and a cup-shaped iron core. After the excitation coil generates a magnetic field, the magnetic field forms a closed loop through the air gap between the electromagnet and the oscillator, the oscillator, and the cup wall of the cup-shaped iron core.

[0011] Compared with the prior art, the beneficial effects of the present invention are:

[0012] (1) By adopting a reasonable variable stiffness and variable damping mechanism, this invention achieves the ability to simultaneously and independently adjust the damping and stiffness of the damper within the limited cavity inside the tool holder through a clever combination and structural design. Compared with similar inventions that only adjust damping or stiffness, this invention has a wider adjustment space, a wider range of applications and a better damping effect.

[0013] (2) The three-section cantilever structure of the present invention (i.e., sliding support 8, cantilever seat 9 and pusher 12) can change the cantilever extension without changing the position of the mass block and the cantilever, which creates a basis for the adjustment of damping and ultimately realizes the independent adjustment of the oscillator stiffness and damping.

[0014] (3) This invention controls the stiffness change of the oscillator by changing the cantilever length of the cantilever rod. Compared with using rubber to provide stiffness, it is not easy to age and can be adjusted. It adopts the electromagnetic eddy current damping principle. Compared with products using damping fluid, it is not easy to leak, easy to install, highly controllable, sensitive to response, and has a long service life.

[0015] (4) The present invention uses an intelligent control module to process and analyze the collected acceleration signal in real time, obtains the optimal damping and stiffness through the internally stored correspondence, and controls the actuator to achieve adaptive adjustment under different working conditions without human intervention. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall structure of the vibration-damping boring bar described in this invention;

[0017] Figure 2 yes Figure 1 An enlarged cross-sectional view of the AA section shown in the diagram;

[0018] Figure 3 yes Figure 1An enlarged cross-sectional view of the BB section shown;

[0019] Figure 4 This is the correspondence between the cantilever extension length and stiffness in this invention;

[0020] Figure 5 This is an enlarged schematic diagram of the electromagnet magnetic circuit in this invention.

[0021] In the picture:

[0022] 1-Cutter head 2-Connecting threaded hole 3-Connecting cover 4-Bolt

[0023] 5-Electromagnet; 51-Excitation coil; 52-Cup-shaped iron core; 6-Oscillator

[0024] 7-Cantilever rod 8-Sliding support 81-Balancing air hole 9-Cantilever seat

[0025] 91-Balance air pressure hole; 10-Connecting rod; 11-Lead screw; 12-Push body

[0026] 13-Bore boring bar body; 14-Motor connecting frame; 15-Coupling; 16-Stepper motor

[0027] 17-Intelligent Control Unit; 18-Acceleration Sensor; 19-Radial Set Screw Detailed Implementation

[0028] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the following embodiments are by no means intended to limit the present invention.

[0029] like Figure 1 As shown, the present invention proposes a vibration damping boring bar with a built-in variable stiffness damper, including a boring bar body 13, a cutting head 1, and an intelligent control unit 17.

[0030] The front part of the boring bar body 13 is provided with a cavity, and the rear part of the boring bar body is coaxially provided with a shaft hole that communicates with the cavity. The cutting head 1 is installed at the cavity port of the boring bar body 13 through the connecting cover 3. In this embodiment, the cutting head 1 and the connecting cover 3 are connected by three screws. That is, the end face of the connecting cover 3 is provided with three connecting threaded holes 2, and the cutting head 1 is provided with three corresponding through holes. The cutting head 1 is connected to the connecting cover 3 by screws, which provides better connection performance. The connecting cover 3 and the boring bar body 13 are connected by threads, and after assembly, the connection strength with the boring bar body 13 is strengthened by radial holes.

[0031] The cavity contains, from front to back along the axial direction of the boring bar body 13, an electromagnet 5, a vibrator 6, a sliding support 8, a cantilever seat 9, and a pusher 12. The electromagnet 5 is fixed to the connecting cover 3 by bolts 4. The connecting cover 3 has a reserved hole for wires, through which the wires of the electromagnet 5 pass and connect to an intelligent control unit 17 that can control the voltage. The cantilever seat 9 is positioned and fixed to the boring bar body 13 by two radial set screws 19. Both the sliding support 8 and the cantilever seat 9 have a central hole. The central hole of the sliding support 8 passes through the cantilever rod 7, and the pusher 12 has a central threaded hole. The cantilever seat 9 is fixed to the cantilever rod 7 through the central hole. The sliding support 8 slides with the cantilever rod 7 through the central hole, allowing axial sliding, and the outer cylindrical surface of the sliding support 8 can slide relative to the inner wall of the cavity of the boring bar body 13. The vibrator 6 is fixed to the cantilever rod 7, and the vibrator 6 is connected to the cantilever base 9 through the cantilever rod 7. There is an air gap of no more than 3mm between the electromagnet 5 and the vibrator 6. The electromagnet 5 includes an excitation coil 51 and a cup-shaped iron core 52. After the excitation coil generates a magnetic field, the magnetic field forms a closed loop through the air gap between the electromagnet 5 and the vibrator 6, the vibrator 6, and the cup wall of the cup-shaped iron core 52. Figure 5 As shown.

[0032] A lead screw 11 is provided in a shaft hole coaxially disposed at the rear of the boring bar body 13 and communicating with the cavity. The front end of the lead screw 11 is engaged with the central threaded hole of the push body 12, and the rear end of the lead screw 11 is connected to the output end of the stepper motor 16 through a coupling 15. A motor connecting frame 14 is provided at the rear end of the boring bar body 13, and the stepper motor 16 is fixed on the motor connecting frame 14.

[0033] The sliding support 8, cantilever seat 9, and pusher body 12 are all provided with N+M through holes arranged circumferentially around the central axis. In this embodiment, there are a total of 4 through holes, such as... Figure 2 The sliding support 8 has two through holes for balancing air pressure holes 81, and two other through holes for the connecting rod 10 to pass through. Figure 3 As shown, similarly, the two through holes on the cantilever seat 9 are pressure balancing holes 91, and the other two through holes are connecting rod holes for the connecting rod 10 to pass through; the axes of the two connecting rod holes on the sliding support 8, the cantilever seat 9, and the pusher 12 are respectively coincident, and a connecting rod 10 passes through each connecting rod hole. The sliding support 8 and the pusher 12 are respectively fixed to both ends of the connecting rod 10, and the diameter of the connecting rod hole on the cantilever seat 9 is larger than the diameter of the connecting rod 10. Figure 1 and Figure 2As shown, the sliding support 8 is fixed to the connecting rod 10 through circumferentially arranged threaded holes. The connecting rod 10 passes through the cantilever seat 9 and is connected to the pusher 12. The two connecting rods 10 are symmetrically arranged around the cantilever rod 7 and do not interfere with the cantilever rod 7. The remaining two balancing air pressure holes 81 are left unused. The pusher 12 adjusts the position of the sliding support 8 through the connecting rods 10 passing through the cantilever seat 9. Figure 1 As shown, the pusher 12 has circumferentially distributed holes, which are fixed to the connecting rod 10. The center of the pusher 12 is a lead screw thread hole connected to the lead screw 11. The lead screw 11 extends out of the tail of the boring bar body 13 through the through hole at the rear of the boring bar body 13, and is connected to the stepper motor 16 through the coupling 15. The stepper motor 16 is connected to the tail of the boring bar body 13 through the hollow motor connecting frame 14. The hollow motor connecting frame 14 can accommodate the coupling 15 used to connect the motor shaft and the lead screw 7. The stepper motor 16 is connected to the intelligent control unit 17.

[0034] An acceleration sensor 18 is provided on the outer wall of the boring bar body 13, located on one side of the cutter head 1.

[0035] The accelerometer 18, electromagnet 5, and stepper motor 16 are all connected to the intelligent control unit 17. The intelligent control unit 17, together with the electromagnet 5, accelerometer 18, and stepper motor 16, forms a control loop of sensor, controller, and actuator. The intelligent control unit 17 includes a controllable voltage power supply for controlling the electromagnet 5, a driver for the stepper motor 16 and its power supply, a central processing unit that can be controlled via Wi-Fi, and integrates an acceleration signal acquisition card, a DC electromagnet voltage controller, and a stepper motor controller. It can collect and process the signal from the accelerometer 18 through a charge amplifier and automatically calculate and output corresponding parameters to control the stepper motor 16 and the electromagnet 5.

[0036] The central processing unit includes a stiffness and damping control program. By analyzing the signal from the accelerometer 18, it extracts the current excitation frequency. Based on the excitation frequency-vibration amplitude function of the two-degree-of-freedom system dynamics model, it obtains the oscillator stiffness and damping values ​​that minimize the vibration amplitude at the current excitation frequency. By adjusting the voltage of the electromagnet 5 and the rotation angle of the stepper motor 16, the damping and stiffness of the oscillator 6 are adjusted to these values ​​(i.e., the oscillator stiffness and damping values ​​that minimize the vibration amplitude at the current excitation frequency obtained above).

[0037] The entire system of the present invention is connected to an external power source through the intelligent control unit 17, which can distribute voltage to each electrical component.

[0038] Before formal use, several automatic calibration processes are required. These processes include: setting the working conditions, workpiece feed, automatic adjustment of damping and stiffness, collecting and processing acceleration signals, iterating the optimal stiffness and damping based on the amplitude, and correcting the function library. In this invention, the function library refers to the excitation frequency-master system vibration amplitude function in the two-degree-of-freedom system dynamic model. The vibration amplitude of the master system (i.e., the boring bar body 13 in this invention) is affected by the following factors: the equivalent mass of the boring bar, the equivalent stiffness of the boring bar, the mass of the oscillator, the stiffness of the oscillator, and damping. Different working conditions will change the excitation frequency, while the stiffness and damping of the oscillator can be controlled to change it. After external excitation (i.e., vibration during machining), changing the stiffness and damping of the oscillator will change the vibration amplitude of the boring bar. The goal is to minimize the amplitude of the boring bar within the controllable range of oscillator damping and stiffness. The specific function relating the boring bar amplitude to the above parameters... The numerical relationship is a commonly used technical method in the industry; therefore, this invention will not elaborate on how to adjust the stiffness and damping of the oscillator according to the structure provided by the technical solution of this invention. In this invention, the boring bar amplitude is obtained by controlling the electromagnet voltage and the motor rotation angle. The boring bar amplitude, electromagnet voltage, and motor rotation angle are the output and input of the control system. The motor rotation angle and electromagnet voltage that minimize the amplitude of the boring bar body at a certain excitation frequency are determined. For example, the preset is to adjust the voltage to 12V and the motor rotation angle to 3600 degrees at 260Hz. Due to the error between calculation and actual processing, the calculated mass, stiffness, and damping will differ from the actual values, so a correction function is introduced.

[0039] After setting the initial cutting parameters, the tool feed begins. The accelerometer 18 transmits the collected signal to the control unit 17. Once the signal stabilizes, its frequency domain characteristics are extracted. The optimal voltage of the electromagnet 5 and the rotation angle of the stepper motor 16 corresponding to the current vibration frequency are found from the preset function to minimize the amplitude of the boring bar body 13. First, the electromagnet 5 is kept at the preset optimal voltage. The rotation angle of the stepper motor 16 is slowly increased from a low value near the preset value to a high value, and the acceleration amplitude of the accelerometer is recorded during this process. The rotation angle corresponding to the minimum amplitude is selected as the optimal rotation angle. When the stepper motor 16 is at the optimal rotation angle, the voltage of the electromagnet 5 is slowly increased from a low value near the preset value to a high value, and the acceleration amplitude of the accelerometer is recorded during this process. The voltage corresponding to the minimum amplitude is selected as the optimal rotation angle. The above process is repeated, alternating between the voltage and the motor rotation angle, iterating the optimal parameters. When the parameters tend to stabilize, at this point... When the amplitude of the boring bar body 13 is at its minimum, the calibration is complete, and the function is updated. It should be noted that the above calibration process does not need to be performed under every working condition. After calibration under a limited number of working conditions, the system can automatically infer the optimal voltage and rotation angle for the remaining untested working conditions.

[0040] The working principle of the vibration damping boring bar of this invention is as follows:

[0041] Regarding stiffness control, one end of the cantilever 7 is fixed to the oscillator 6, and the other end passes through the central hole of the sliding support 8 and is fixed to the cantilever seat 9. The actual overhang length of the cantilever is the portion between the oscillator and the sliding support. When the sliding support 8 slides, the overhang length of the cantilever 7 changes. According to mechanics of materials, the stiffness of the cantilever changes accordingly. The relationship between overhang length and stiffness is as follows: Figure 4 As shown.

[0042] In damping control, eddy current damping is a damping effect generated by induced current, primarily used in engineering and scientific fields. Its principle is based on Faraday's law of electromagnetic induction and the Lorentz force. When a conductor is placed in a changing magnetic field, eddy currents are induced within it according to Faraday's law of electromagnetic induction. These eddy currents generate their own magnetic fields and react against the external magnetic field. This reaction results in an electromagnetic force that impedes the conductor's motion, thus dissipating energy and slowing the system. When the high-density alloy oscillator 6 radially jumps relative to the electromagnet 5, cutting magnetic field lines, an induced current forms a closed loop within the oscillator 6. The resulting eddy current magnetic field interacts with the electromagnet's magnetic field, providing a Lorentz force that impedes the oscillator's motion, which is dissipated as heat. By changing the voltage across the electromagnet, the strength of the magnetic field can be altered, thus changing the damping of the oscillator system. The system's magnetic circuit is as follows: Figure 5 As shown, 51 is the excitation coil, and 52 is the cup-shaped iron core. When the magnetic field is generated from the coil, it passes through the air gap, the oscillator, and the cup wall to form a closed loop.

[0043] The working process of the vibration damping boring bar of this invention is as follows:

[0044] Step 1: Install the boring bar of the present invention on a general-purpose lathe, and set the rotational speed, depth of cut, and feed rate;

[0045] Step 2: Accelerometer 18 monitors the acceleration signal in real time and transmits the data to the intelligent control unit 17 in real time;

[0046] Step 3: When the acquired vibration signal stabilizes, analyze and extract its frequency domain characteristics to obtain the current vibration frequency;

[0047] Step 4: Based on the excitation frequency-vibration amplitude function of the two-degree-of-freedom system dynamic model, obtain the oscillator stiffness and damping value that minimizes the vibration amplitude of the boring bar at the current excitation frequency, and adjust the damping and stiffness of the oscillator to this value by adjusting the voltage of the electromagnet 5 and the rotation angle of the stepper motor 16.

[0048] Step 5: The electromagnet 5 is affected by the voltage change, which in turn changes the magnetic field strength, and thus changes the eddy current damping value of the oscillator 6; the stepper motor is driven by the control signal to rotate the lead screw 11 by a corresponding angle. The rotation of the lead screw 11 drives the pusher 12 to move axially, changing the position of the sliding support 8, and thus changing the overhang length of the cantilever rod 7 between the sliding support 8 and the oscillator 6 (the actual overhang length of the cantilever rod 7 is the part between the oscillator 6 and the sliding support 8). According to the mechanics of materials, the longer the cantilever beam is overhang, the lower the stiffness, and the shorter the overhang, the higher the stiffness. By changing the stiffness of the oscillator 6, the optimal vibration reduction of the boring bar body 13 under the current working condition is achieved.

[0049] Step 6: When the processing parameters change, the system automatically repeats the above process to complete real-time optimal vibration reduction control.

[0050] Although the present invention has been described above in conjunction with the accompanying drawings, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many modifications under the guidance of the present invention without departing from the spirit of the present invention, and these modifications are all within the protection scope of the present invention.

Claims

1. A vibration damping boring bar with a built-in variable stiffness damper, comprising a boring bar body (13), a cutting head (1), and an intelligent control unit (17); characterized in that, The front part of the boring bar body (13) is provided with a cavity, and the rear part of the boring bar body is coaxially provided with a shaft hole that communicates with the cavity; the cutting head (1) is installed at the cavity port of the boring bar body (13) through a connecting cover (3); The cavity is provided with an electromagnet (5), an oscillator (6), a sliding support (8), a cantilever seat (9), and a pusher (12) in sequence from front to back along the axial direction of the boring bar body (13); the electromagnet (5) is fixedly connected to the connecting cover (3), the cantilever seat (9) is fixedly connected to the boring bar body (13), the sliding support (8) and the cantilever seat (9) are respectively provided with a central hole, the pusher (12) is provided with a central threaded hole, and the cantilever seat (9) is fixedly connected to the cantilever rod (7) through the central hole; The vibrator (6) is fixed to the cantilever rod (7), and there is an air gap of no more than 3mm between the electromagnet (5) and the vibrator (6); The sliding support (8) is slidably engaged with the cantilever rod (7) through the central hole; A lead screw (11) is provided in the shaft hole. The front end of the lead screw (11) is engaged with the central threaded hole of the push body (12). The rear end of the lead screw (11) is connected to the output end of the stepper motor (16) through a coupling (15). The sliding support (8), cantilever seat (9), and pusher (12) are each provided with N+M through holes arranged circumferentially around the central axis. Among them, N through holes are pressure balancing holes, and M are connecting rod holes, with N and M both ≥ 2. The axes of the M connecting rod holes on the sliding support (8), cantilever seat (9), and pusher (12) are respectively coincident. A connecting rod (10) passes through each connecting rod hole. The sliding support (8) and the pusher (12) are respectively fixed to the two ends of the connecting rod (10). The diameter of the connecting rod hole on the cantilever seat (9) is larger than the diameter of the connecting rod (10). An acceleration sensor (18) is provided on the outer wall of the boring bar body (13) located on one side of the cutting head (1); The accelerometer (18), electromagnet (5) and stepper motor (16) are all connected to the intelligent control unit (17); The intelligent control unit (17) includes a central processing unit, an acceleration signal acquisition card, a DC electromagnet voltage controller, and a stepper motor controller. The central processing unit includes a stiffness and damping control program. By analyzing the signal of the acceleration sensor (18), the current excitation frequency is extracted. Based on the excitation frequency-vibration amplitude function of the two-degree-of-freedom system dynamics model, the stiffness and damping values ​​of the oscillator that minimize the vibration amplitude at the current excitation frequency are obtained. By adjusting the voltage of the electromagnet (5) and the rotation angle of the stepper motor (16), the damping and stiffness of the oscillator (6) are adjusted to the stiffness and damping values ​​of the oscillator that minimize the vibration amplitude at the current excitation frequency.

2. The vibration damping boring bar with a built-in variable stiffness damper according to claim 1, characterized in that, The electromagnet (5) is fixed to the connecting cover (3) by bolts (4). The connecting cover (3) is provided with a reserved hole. The wire of the electromagnet (5) passes through the reserved hole and is connected to the intelligent control unit (17).

3. The vibration damping boring bar with a built-in variable stiffness damper according to claim 1, characterized in that, The rear end of the boring bar body (13) is provided with a motor connecting frame (14), and the stepper motor (16) is fixed on the motor connecting frame (14).

4. The vibration damping boring bar with a built-in variable stiffness damper according to claim 1, characterized in that, The cantilever seat (9) is positioned and fixed to the boring bar body (13) by two radial set screws (19).

5. The vibration damping boring bar with a built-in variable stiffness damper according to claim 1, characterized in that, The electromagnet (5) includes an excitation coil (51) and a cup-shaped iron core (52). After the excitation coil generates a magnetic field, the magnetic field forms a closed loop through the air gap between the electromagnet (5) and the oscillator (6), the oscillator (6), and the cup wall of the cup-shaped iron core (52).

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