Vibration suppression structure for deep hole machining of nuclear power unloading device and control method thereof

Abstract

The application provides a vibration suppression structure for deep hole machining of a nuclear power unloading device and a control method thereof, and relates to the technical field of deep hole machining.The vibration suppression structure comprises a tool bar, a first damping unit, a second damping unit, a signal sensing unit and a cooperative control unit.The tool bar comprises a first rigid section, a second rigid section and a third rigid section.The second rigid section comprises an inner core and an outer shell.The first damping unit comprises a first excitation coil group, a ring-shaped inertial mass and a magneto-rheological fluid.The second damping unit comprises a second excitation coil group, a plurality of granular damping media and a magneto-rheological fluid.The cooperative control unit is in communication connection with the signal sensing unit, the first damping unit and the second damping unit respectively.The application can realize self-adaptive suppression of wideband multi-modal vibration in deep hole machining with a large length-diameter ratio under the condition that the external size is unchanged, and significantly improves machining precision, surface quality and machining efficiency.

Description

Technical Field

[0001] This invention relates to the field of deep hole machining technology, and specifically to a vibration suppression structure and control method for deep hole machining of nuclear power plant unloading devices. Background Technology

[0002] With the accelerated localization of nuclear power equipment in my country, the quality of deep-hole machining of the nuclear power plant unloading device housing, a core component for the safe operation of the reactor, directly determines the assembly accuracy and service life of the assembly. The unloading device housing is mostly made of high-strength alloy materials, and its internal deep-hole structure is characterized by a large length-to-diameter ratio, high machining accuracy requirements (hole diameter tolerance ≤ ±0.02mm), and stringent surface quality requirements (roughness ≤ 0.4μm). Currently, this type of deep-hole machining is typically completed using multi-axis CNC machining equipment, relying on the coordinated movement of the tool system and the machine tool axis system to remove material. In traditional machining methods, the tool holder is generally a cylindrical structure of equal diameter, with one end connected to the machine tool spindle and the other end fitted with a cutting head. The spindle rotation drives the cutting head to cut the workpiece.

[0003] However, during the aforementioned machining process, due to the large overhang length and relatively insufficient rigidity of the tool holder in deep hole machining, the tool holder is prone to bending deformation and torsional vibration under the action of cutting force, generating forced vibration. Simultaneously, dynamic fluctuations in the cutting thickness can easily trigger regenerative chatter, which forms positive feedback within the tool holder system, rapidly amplifying the vibration amplitude. These vibration problems are coupled during machining, leading to chatter marks on the hole wall, deterioration of surface roughness, deviation in hole diameter, and axial misalignment, making it difficult to meet the stringent requirements for hole diameter tolerances and surface quality of nuclear power plant unloading device housings. Furthermore, abnormal tool wear and chipping caused by vibration increase machining costs, severely restricting the improvement of machining efficiency and product qualification rate. Summary of the Invention

[0004] To address the problems in related technologies, this invention provides a vibration suppression structure and its control method for deep hole machining in nuclear power plant unloading devices.

[0005] To achieve the above objectives, the technical solution adopted by the present invention includes: According to a first aspect of the present invention, a vibration suppression structure for deep hole machining of a nuclear power plant unloading device is provided, comprising: A tool holder, comprising a first rigid section, a second rigid section, and a third rigid section connected in sequence; the first rigid section is used to mount on the spindle end of a multi-axis linkage machining unit, and the third rigid section is used to mount a tool head; the second rigid section comprises an inner core and an outer shell sleeved outside the inner core; the inner core contains a first annular cavity and a second annular cavity spaced apart; the outer shell contains a third annular cavity corresponding to the first annular cavity and a fourth annular cavity corresponding to the second annular cavity; The first damping unit includes a first excitation coil assembly installed in the third annular cavity, an annular inertial mass housed in the first annular cavity, and a magnetorheological fluid filled in the first annular cavity. The annular inertial mass is configured to be able to suspend in the first annular cavity. The second damping unit includes a second excitation coil assembly installed in the fourth annular cavity, a plurality of particulate damping media contained in the second annular cavity, and magnetorheological fluid filled in the second annular cavity. The plurality of particulate damping media are configured to be immersed in the magnetorheological fluid in the second annular cavity. The system includes a signal sensing unit and a collaborative control unit. The signal sensing unit is used to collect vibration signals, cutting force signals, temperature signals, displacement signals, and current and / or voltage signals of the multi-axis linkage machining unit during the machining process. The collaborative control unit is communicatively connected to the signal sensing unit, the first damping unit, and the second damping unit, respectively, and is used to control the damping coefficients of the first damping unit and the second damping unit according to the data collected by the signal sensing unit.

[0006] Optionally, the tool holder further includes an injection channel and several drainage channels; The fluid injection channel is formed within the first rigid section, the inner core, and the third rigid section. The fluid injection channel includes an inlet section and a plurality of injection sections. The inlet section extends along the axial direction of the tool holder. The first annular cavity and the second annular cavity are respectively sleeved outside the inlet section. One end of the inlet section extends into the third rigid section, and the other end of the inlet section extends to the side of the first rigid section away from the second rigid section. One end of the plurality of injection sections extends into the third rigid section and communicates with the inlet section. The other end of the plurality of injection sections extends to the peripheral wall of the third rigid section for conveying cutting fluid into the deep hole to be machined. A plurality of drainage channels are arranged circumferentially along the tool holder. Each drainage channel includes an inlet section and a drainage section extending axially along the tool holder. The drainage section is formed within the first rigid section, the outer shell, and the third rigid section. One end of the drainage section extends to the side of the first rigid section away from the second rigid section, and the other end extends into the third rigid section. The drainage section is sequentially disposed between the first annular cavity and the third annular cavity, and between the second annular cavity and the fourth annular cavity. One end of the inlet section extends into the third rigid section and communicates with the drainage section. The other end of the inlet section extends to the peripheral wall of the third rigid section for the entry of cutting fluid and chips. The inlet section is closer to the second rigid section than the injection section.

[0007] Optionally, the inner core is interference-fitted within the outer shell, and the outer diameter of the first rigid section is... The outer diameter of the second rigid section and the outer diameter of the third rigid segment satisfy: , .

[0008] Optionally, the substrate of the first rigid segment is powder metallurgy high-speed steel, and the outer wall of the first rigid segment is coated with a tungsten carbide-cobalt hard alloy gradient coating by hot isostatic pressing. The thickness of the gradient coating gradually decreases along the direction from the second rigid segment to the first rigid segment. The matrix of the third rigid segment is made of fully dense cemented carbide, and the outer diameter of the third rigid segment gradually decreases along the direction from the second rigid segment to the third rigid segment.

[0009] Optionally, the signal sensing unit includes: An accelerometer sensor array is mounted on the tool holder to collect vibration signals from the tool holder. A cutting force sensor is mounted on the tool holder and located at the interface between the third rigid section and the second rigid section, and is used to collect cutting force signals during the cutting process; A temperature sensor is mounted on the tool holder to collect the tool holder temperature signal; A displacement sensor is used to be mounted on the end of the spindle to collect spindle displacement signals; Current sensors and / or voltage sensors are used to acquire current signals and / or voltage signals of the multi-axis linkage machining unit.

[0010] According to a second aspect of the present invention, a vibration suppression method for deep hole machining of a nuclear power plant unloading device is also provided, applied to the vibration suppression structure for deep hole machining of a nuclear power plant unloading device described in any of the technical solutions of the first aspect of the present invention, comprising the following steps: Step S1: System initialization, install the tool holder on the spindle end of the multi-axis linkage machining unit, clamp the workpiece to be processed, and load the machining process parameters and control algorithm parameters in the collaborative control unit; Step S2: Start the multi-axis linkage machining unit to perform deep hole cutting. The signal sensing unit collects multi-source signals during the machining process in real time and transmits them to the collaborative control unit. The multi-source signals include vibration signals, cutting force signals, temperature signals, displacement signals, and current signals and / or voltage signals of the multi-axis linkage machining unit. Step S3: Based on the received vibration signal, the collaborative control unit estimates the vibration state of the tool holder in real time through an extended Kalman filter vibration state observer. The vibration state includes the generalized displacement component and generalized velocity component of the first multi-mode, and extracts the vibration amplitude and vibration frequency of each mode. Based on the acquired cutting force signal, the dynamic cutting force component is calculated, and chatter is identified according to the dynamic cutting force component and the real-time estimated vibration amplitude to determine whether the alarm threshold is exceeded. If the alarm threshold is exceeded, emergency chatter suppression control is executed. The emergency chatter suppression control includes setting the excitation current of the first damping unit and the second damping unit to the maximum value, reducing the feed speed, and adjusting the spindle speed until the vibration amplitude falls back below the alarm threshold. Step S4: The collaborative control unit calculates the excitation current commands of the first damping unit and the second damping unit based on the real-time estimated vibration amplitude, vibration frequency and dynamic cutting force components, and sends them to the damping adjustment drive circuit. The damping adjustment drive circuit adjusts the actual excitation current of the first excitation coil group and the second excitation coil group through pulse width modulation to change the shear yield stress of the magnetorheological fluid and realize the real-time adjustment of the damping coefficient. Step S5: The collaborative control unit uses the real-time estimated radial vibration displacement of the tool holder as the feedforward compensation amount to correct the tool center point trajectory in real time, and sends the corrected trajectory command to the servo drives of each axis of the multi-axis linkage machining unit. S6: Repeat steps S2 to S5 until the current deep hole machining is completed. After machining is completed, machining quality information is generated.

[0011] Optionally, in step S3, the state equation and observation equation of the extended Kalman filter vibration state observer are respectively expressed as: In the formula, The state vector includes the generalized displacement and generalized velocity components of the tool holder's modal coordinates. for The first derivative with respect to time, The control input vector includes the excitation current control signal of the first damping unit and the second damping unit. Its covariance matrix is , For observation vectors; The observation matrix; The covariance matrix of the observation noise is: , For the system matrix, The input matrix; The prediction step of the extended Kalman filter is represented as follows: The update step of the extended Kalman filter is represented as follows: In the formula, To utilize the first The estimated value at time t for the th The prior estimate of the state vector at time step [time]. For the first The posterior estimate of the state vector at time step [time]. For the first The error covariance matrix of the prior estimate at time step, For the first The error covariance matrix of the posterior estimate at time step [time]. For the first The posterior estimate of the state vector at time step [time]. For the first The error covariance matrix of the posterior estimate at time step [time]. For the first The Kalman gain matrix at time 10:00. For the first The state transition matrix at time t and , The discretized process noise covariance matrix is... This is the discretized observation noise covariance matrix. It is the identity matrix. The sampling period.

[0012] Optionally, in step S3, the radial, tangential, and axial components of the dynamic cutting force are respectively expressed as: In the formula, The radial component of the dynamic cutting force component. This refers to the tangential component of the dynamic cutting force component. This refers to the axial component of the dynamic cutting force component. , and These are the radial, tangential, and axial cutting force coefficients, respectively. For cutting width, For dynamic cutting thickness fluctuation and , For the tool rotation cycle, Main spindle speed This refers to the number of teeth on the cutting tool. The principal angle; In step S4, the excitation current of the first damping unit and the second damping unit is calculated according to the following control law: in, Corresponding to the first damping unit and the second damping unit respectively, Indicates the modal order. For the first Real-time excitation current of the damping unit and The first The minimum and maximum excitation currents of the damping unit, For the Sigmoid function, For the first Real-time vibration amplitude estimates for the first mode. For the first Real-time vibration frequency estimates of the first mode. Let be the Euclidean norm of the dynamic cutting force components. For the first The amplitude-frequency weighting coefficient of the damping element, For the first Force weighting coefficient of damping element.

[0013] Optionally, in step S3, the reduction of the feed rate is performed according to the following formula: In the formula, For real-time feed rate, For nominal feed rate, The attenuation coefficient and , For real-time vibration amplitude, the weighted root mean square value of the amplitudes of the first multiple modes of vibration is taken. The preset vibration amplitude threshold; The spindle speed is adjusted according to the following formula: In the formula, For real-time spindle speed, Nominal spindle speed, Main spindle speed adjustment amount For adjustment coefficient and , For real-time vibration frequency estimation, the dominant frequency components of the first few modal vibration frequencies are taken. Let be the natural frequency of the tool holder.

[0014] Optionally, in step S5, the corrected tool center point trajectory command is expressed as: In the formula, This is the corrected tool center point trajectory command vector. The nominal tool center point trajectory vector, The estimated value vector of the radial vibration displacement of the tool holder contains vibration displacement components in the X and Y directions, and is extracted from the state vector by the extended Kalman filter vibration state observer.

[0015] Beneficial effects: 1. First, the present invention integrates two damping units with different physical principles in the annular space between the inner core and the outer shell of the tool holder (the first damping unit uses the relative shear motion of the annular inertial mass in the magnetorheological fluid to dissipate energy, focusing on suppressing the lateral bending vibration of the tool holder; the second damping unit uses the mutual collision and friction between the granular damping media to dissipate energy, focusing on suppressing the broadband high-frequency flutter component). The energy dissipation frequency bands of the two complement each other, and with the millisecond-level controllable rheological characteristics of the magnetorheological fluid, it has a significant suppression effect on both forced vibration and self-excited flutter.

[0016] Secondly, the present invention configures two damping units with independent excitation coil groups, and the two damping units are arranged at intervals in the axial direction. The collaborative control unit can independently and continuously change the magnetic flux density in the region where each damping unit is located by adjusting the excitation current of the first excitation coil group and the second excitation coil group based on the multi-source information such as vibration and cutting force collected in real time by the signal sensing unit. This enables independent real-time adjustment of the damping coefficients of the first damping unit and the second damping unit to match the differentiated requirements of damping force for different processing stages such as changes in cutting parameters, step transitions, and tool wear.

[0017] Third, this invention integrates an acceleration sensor group and a cutting force sensor on the tool holder, enabling the tool holder to perceive its own vibration state and cutting force state in real time. Based on the data collected by the sensors in real time, the collaborative control unit issues control commands to the two damping units and synchronously corrects the tool center point trajectory, forming a closed-loop control link of state perception—real-time decision-making—active execution. This allows for suppression during the chatter initiation stage, achieving continuous regulation of machining stability.

[0018] Fourth, this invention arranges the inlet section of the fluid injection channel on the radially inner side of the damping cavity, and the drainage section is arranged between the first and third annular cavities, and between the second and fourth annular cavities, allowing the cutting fluid delivery and damping functions to coexist in the same radial space of the tool holder without interfering with each other. All damping elements are integrated within the tool holder wall thickness range, without changing the tool holder's external diameter and profile, and can directly replace existing tool holders without requiring adaptive modifications to the machine tool spindle interface and tool clamping method, thus possessing good prospects for industrial applications.

[0019] 2. Other beneficial effects or advantages of the present invention will be described in detail in the specific embodiments. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] in: Figure 1 This is a three-dimensional structural schematic diagram from one perspective of a vibration suppression structure for deep hole machining of a nuclear power plant unloading device, provided by an exemplary embodiment of the present invention. Figure 2 This is a three-dimensional structural schematic diagram from another perspective of a vibration suppression structure for deep hole machining of a nuclear power plant unloading device, provided by an exemplary embodiment of the present invention. Figure 3 This is a partial cross-sectional schematic diagram of a vibration suppression structure for deep hole machining of a nuclear power plant unloading device, provided by an exemplary embodiment of the present invention. Figure 4 This is a schematic diagram of the arrangement of a signal sensing unit and a cooperative control unit provided in an exemplary embodiment of the present invention.

[0022] Explanation of the labels in the attached drawings: 100 - Vibration suppression structure for deep hole machining in nuclear power plant unloading equipment; 1 - Tool holder; 11 - First rigid section; 12 - Second rigid section; 121 - Inner core; 1211 - First annular cavity; 1212 - Second annular cavity; 122 - Outer shell; 1221 - Third annular cavity; 1222 - Fourth annular cavity; 13 - Third rigid section; 14 - Liquid injection channel; 141 - Inlet section; 142 - Liquid injection section; 15 - Liquid discharge channel; 151 - Inlet section; 152 - Liquid discharge section; 2 - First damping unit; 21 - First excitation coil group; 22 - Annular inertial mass; 3 - Second damping unit; 31 - Second excitation coil group; 4 - Signal sensing unit; 5 - Cooperative control unit; 61 - Acceleration sensor group; 62 - Cutting force sensor; 63 - Temperature sensor; 64 - Displacement sensor; 65 - Current sensor; 66 - Voltage sensor. Detailed Implementation

[0023] To facilitate a clearer and more accurate understanding of the technical solutions of this invention by those skilled in the art, the existing related technologies and their technical problems will be described in more detail below.

[0024] The nuclear power plant unloading unit housing is the core load-bearing component for the transfer and positioning of reactor fuel assemblies. It contains multiple sets of axially extending deep holes for mounting precision-fitting components such as guide sleeves and control rod drive mechanism connectors. These deep holes are characterized by a large aspect ratio, high machining accuracy requirements, and stringent surface quality requirements. The housing material is typically austenitic stainless steel or nickel-based superalloys, such as 316LN or Inconel 718. These materials exhibit high plasticity, strong work hardening tendency, and low thermal conductivity during machining, further increasing the difficulty of deep hole machining.

[0025] Currently, this type of deep hole machining is usually completed on multi-axis CNC machine tools. During machining, the machine tool spindle drives the tool head mounted at the end of the tool holder to rotate, while the feed motion of the Z-axis slide drives the tool holder to penetrate axially into the workpiece to remove material.

[0026] Taking a typical machining process as an example, when the overhang length of the tool holder reaches more than ten times its diameter, under the combined action of radial cutting force, tangential cutting force, and axial feed force, its slender structure causes it to exhibit significant flexibility under this condition (the tool holder undergoes elastic bending under the push of the cutting force and springs back after the cutting force is removed). A periodic radial displacement trajectory is formed at the end of the tool holder, leaving spiral chatter marks on the machined hole wall. These chatter marks cause the actual cutting thickness to deviate from the nominal cutting thickness during subsequent cutting, with the deviation equal to the amplitude of the chatter marks left by the previous tooth rotation. This creates a positive feedback relationship between cutting thickness fluctuations and tool vibration. When the system stability boundary is exceeded, this positive feedback relationship further evolves into self-excited chatter, i.e., regenerative chatter. In this chatter state, the vibration amplitude rapidly amplifies to several times the nominal cutting thickness within several tool rotation cycles. The amplitude of the alternating load on the tool tip far exceeds its static design bearing capacity, leading to high-frequency fretting fatigue damage on the tool tip surface, and in severe cases, tool tip breakage.

[0027] Meanwhile, the deep holes in the housing are not through holes, but rather consist of multiple segments of different diameters distributed along the axial direction, connected by stepped or conical transition surfaces. When machining the transition points, the tool needs to transition from one segment of a different diameter to another, causing abrupt changes in the cutting depth and width before and after the transition, resulting in a sharp jump in the cutting force amplitude within a short time domain.

[0028] Taking the continuous machining of two adjacent deep holes with different diameters using the same tool as an example, when the tool is machining from the small diameter hole to the step surface, the radial cutting force of the tool jumps within a very short stroke, and the elastic deformation of the tool holder system changes abruptly, resulting in axial misalignment between the machined hole and the hole to be machined. This misalignment is difficult to compensate for by adjusting the cutting parameters in subsequent processes, and ultimately affects the concentricity of each group of holes in the housing.

[0029] The aforementioned processing quality issues have further triggered a chain reaction in actual production.

[0030] Dimensional deviations and surface defects caused by borehole wall vibration marks and axial misalignment require correction through subsequent honing or grinding processes. However, these correction processes have limited accessibility for deep, stepped holes and are prone to introducing new geometric errors. Workpieces that cannot be salvaged through correction processes must be scrapped entirely. The manufacturing cycle for nuclear power plant unloading device housings can last for several months, and individual workpieces have already accumulated significant material and labor costs in the early forging, rough machining, and heat treatment stages. Therefore, the economic losses from scrapping are substantial.

[0031] Furthermore, since the aforementioned vibration and precision issues heavily rely on high-rigidity processing equipment and supporting active vibration damping technology, the relevant technological accumulation in this field in China is still insufficient. The deep hole processing of the nuclear power unloading device box still mainly relies on imported special machine tools and cutting tool systems, which further increases the cost of equipment procurement and maintenance, and also restricts the independent controllability of the nuclear power equipment supply chain.

[0032] In view of this, the present invention provides a novel solution: a vibration suppression structure and method for deep hole machining in nuclear power plant unloading devices. The technical concept of the present invention is as follows: the tool holder is constructed as a double-layer structure with an inner core and an outer shell coaxially nested. A controllable damping unit based on magnetorheological fluid is integrated within the annular space between the inner core and the outer shell. A signal sensing unit mounted on the tool holder collects multi-source signals such as vibration, force, and temperature during the machining process in real time. A collaborative control unit dynamically adjusts the excitation current of the damping unit based on signal feedback to change the rheological properties of the magnetorheological fluid, thereby achieving adaptive suppression of multimodal vibrations generated during machining. This transforms the tool holder from a passive force-transmitting component into an intelligent execution unit with active vibration suppression capabilities, significantly improving the dynamic stability of the high aspect ratio deep hole machining system without changing the external geometry of the tool holder.

[0033] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings.

[0034] like Figures 1 to 4 As shown, this embodiment provides a vibration suppression structure 100 for deep hole machining in a nuclear power plant unloading device according to a first aspect of the present invention, comprising a tool holder 1, a first damping unit 2, a second damping unit 3, a signal sensing unit 4, and a cooperative control unit 5. Wherein, The tool holder 1 includes a first rigid section 11, a second rigid section 12, and a third rigid section 13 connected in sequence. The first rigid section 11 is used to install on the spindle end of the multi-axis linkage machining unit, and the third rigid section 13 is used to install the tool head. The second rigid section 12 includes an inner core 121 and an outer shell 122 sleeved outside the inner core 121. The inner core 121 is provided with a first annular cavity 1211 and a second annular cavity 1212 spaced apart. The outer shell 122 is provided with a third annular cavity 1221 corresponding to the first annular cavity 1211 and a fourth annular cavity 1222 corresponding to the second annular cavity 1212. The first damping unit 2 includes a first excitation coil group 21 installed in the third annular cavity 1221, an annular inertial mass 22 housed in the first annular cavity 1211, and a magnetorheological fluid filled in the first annular cavity 1211. The annular inertial mass 22 is configured to be able to suspend in the first annular cavity 1211. The second damping unit 3 includes a second excitation coil group 31 installed in the fourth annular cavity 1222, a plurality of particulate damping media contained in the second annular cavity 1212, and magnetorheological fluid filled in the second annular cavity 1212. The plurality of particulate damping media are configured to be immersed in the magnetorheological fluid in the second annular cavity 1212. The signal sensing unit 4 is used to collect vibration signals, cutting force signals, temperature signals, displacement signals, and current and / or voltage signals of the multi-axis linkage machining unit during the machining process. The collaborative control unit 5 is communicatively connected to the signal sensing unit 4, the first damping unit 2, and the second damping unit 3, respectively, and is used to control the damping coefficients of the first damping unit 2 and the second damping unit 3 according to the data collected by the signal sensing unit 4.

[0035] Through the above technical solution, firstly, the present invention can achieve synergistic suppression of broadband multimodal vibration. Specifically, existing deep hole machining tool holders rely solely on the internal friction of the structural material to attenuate vibration, and their equivalent damping ratio is typically only 0.01~0.03, resulting in extremely low dissipation efficiency for low-frequency bending vibration and almost no suppression effect on high-frequency flutter components.

[0036] This invention integrates two damping units based on different physical principles along the axial direction within the same tool holder 1. The first damping unit 2 utilizes the relative shear motion of the annular inertial mass 22 in the magnetorheological fluid to dissipate energy, focusing on suppressing the lateral bending vibration of the tool holder 1; the second damping unit 3 utilizes the mutual collision and friction between granular damping media to dissipate energy, focusing on suppressing broadband high-frequency flutter components. This allows the energy dissipation frequency bands of the two damping units to complement each other. Thus, through this combined mechanism of shear energy dissipation and particle collision energy dissipation, the tool holder 1 system of this invention can possess high energy dissipation capability across the entire frequency range, simultaneously suppressing forced vibration and self-excited flutter.

[0037] Secondly, this invention enables independent decoupling and real-time adjustment of the damping coefficient. Specifically, the invention configures two damping units with independent excitation coil groups, and the two annular cavities are arranged axially at intervals. The first excitation coil group 21 only controls the magnetic flux density in the first annular cavity 1211, without affecting the magnetorheological fluid state in the second annular cavity 1212, and vice versa. The response time of the magnetorheological fluid is on the order of milliseconds, allowing the damping coefficients of the first damping unit 2 and the second damping unit 3 to be independently and continuously adjusted in real time during the machining process without interference. In this way, for different vibration modes that occur at different stages of deep hole machining (for example, the sudden change in cutting force at the step transition mainly excites low-frequency bending vibration, while the stable cutting stage mainly faces the risk of high-frequency chatter), this independent adjustment capability allows the output of the corresponding damping unit to be adjusted separately under different vibration modes, achieving precise matching between the vibration suppression strategy and the real-time vibration mode.

[0038] Third, this invention possesses the ability to self-sensitize and actively decide on the vibration state of the tool holder 1. Specifically, in existing deep hole machining, operators can only roughly judge the machining state based on indirect signals such as spindle load current, and cannot take intervention measures in the chatter initiation stage (when the vibration amplitude is only a few micrometers).

[0039] This invention integrates a signal sensing unit 4 onto the tool holder 1 body, transforming the tool holder 1 from a simple passive force transmission component into one capable of real-time sensing of its own vibration and cutting force states. After the signal sensing unit 4 is communicatively connected to the collaborative control unit 5, the collaborative control unit 5 issues control commands to the two damping units based on the real-time collected multi-source signals. This allows the vibration response of the tool holder 1 system to shift from passively bearing the load to actively controlling it, suppressing chatter at its inception and effectively avoiding the lag problem of intervention only after the vibration has fully developed.

[0040] Fourth, this invention can improve the dynamic stability of the system without changing the external geometry of the tool holder 1. Specifically, in deep hole machining with a large aspect ratio, the outer diameter of the tool holder 1 is strictly limited by the diameter of the hole to be machined, and rigidity cannot be improved by simply thickening it. This invention constructs the second rigid section 12 as a double-layer structure with the inner core 121 and the outer shell 122 coaxially nested. The first annular cavity 1211 and the second annular cavity 1212 are respectively formed in the inner core 121 and arranged axially at intervals. The corresponding third annular cavity 1221 and the fourth annular cavity 1222 are formed in the outer shell 122. Both damping units are accommodated in the radial space between the inner core 121 and the outer shell 122. Magnetorheological fluid is filled in this space, and the excitation coil group is embedded in the outer shell 122. That is to say, all damping elements are integrated within the wall thickness range of the tool holder 1, which can maintain the external diameter and contour of the tool holder 1. In this way, this invention can directly replace the existing tool holder 1 without adapting to the machine tool spindle interface and tool clamping method.

[0041] In this embodiment, it should be noted that the application of magnetorheological fluids and their matching excitation coils in the field of controllable dampers is relatively mature. Magnetorheological fluids are typically formed by dispersing micron-sized carbonyl iron powder particles in a carrier liquid (such as silicone oil or synthetic hydrocarbon oil). Under zero magnetic field conditions, they exhibit low-viscosity Newtonian fluid behavior. However, under the action of an applied magnetic field, the suspended particles align in a chain-like structure along the magnetic field lines, transforming the fluid into a Bingham fluid with controllable yield stress within milliseconds. The shear stress and magnetic flux density exhibit a monotonically increasing relationship. The excitation coil generates a magnetic field by passing current through it, and its magnetic flux density is approximately linearly related to the excitation current (within the unsaturated region of the iron core). Therefore, the shear yield stress of the magnetorheological fluid can be continuously adjusted by regulating the excitation current using pulse width modulation. The composition and ratio of the aforementioned materials, the number of turns and wire diameter of the coil, the structural design of the magnetic circuit, and the topology of the drive circuit can all be determined by those skilled in the art through a limited number of experiments based on specific application requirements. This invention will not elaborate on these aspects.

[0042] Furthermore, the density of the annular inertial mass 22 of the present invention is adapted to the density of the magnetorheological fluid, so that the annular inertial mass 22 can be suspended in the magnetorheological fluid under zero magnetic field conditions, thereby generating relative shear motion between the annular inertial mass 22 and the magnetorheological fluid when the tool bar 1 generates lateral vibration.

[0043] In one embodiment of the present invention, such as Figure 3 As shown, the blade holder 1 of the present invention may further include an injection channel 14 and a plurality of drainage channels 15; wherein, The fluid injection channel 14 is formed within the first rigid section 11, the inner core 121, and the third rigid section 13. The fluid injection channel 14 includes an inlet section 141 and a plurality of fluid injection sections 142. The inlet section 141 extends along the axial direction of the tool holder 1. The first annular cavity 1211 and the second annular cavity 1212 are respectively sleeved outside the inlet section 141. One end of the inlet section 141 extends into the third rigid section 13, and the other end of the inlet section 141 extends to the side of the first rigid section 11 away from the second rigid section 12. One end of the plurality of fluid injection sections 142 extends into the third rigid section 13 and communicates with the inlet section 141. The other end of the plurality of fluid injection sections 142 extends to the peripheral wall of the third rigid section 13 for conveying cutting fluid into the deep hole to be machined. A plurality of drainage channels 15 are arranged circumferentially along the tool holder 1. Each drainage channel 15 includes an inlet section 151 and a drainage section 152 extending axially along the tool holder 1. The drainage section 152 is formed within the first rigid section 11, the outer shell 122, and the third rigid section 13. One end of the drainage section 152 extends to the side of the first rigid section 11 away from the second rigid section 12, and the other end of the drainage section 152 extends into the third rigid section 13. The drainage section 152 is sequentially disposed between the first annular cavity 1211 and the third annular cavity 1221, and between the second annular cavity 1212 and the fourth annular cavity 1222. One end of the inlet section 151 extends into the third rigid section 13 and communicates with the drainage section 152. The other end of the inlet section 151 extends to the peripheral wall of the third rigid section 13 for the entry of cutting fluid and chips. Among them, the inlet section 151 is closer to the second rigid section 12 than the injection section 142.

[0044] In this embodiment, the inlet section 141 of the injection channel 14 extends axially along the cutter bar 1, and the first annular cavity 1211 and the second annular cavity 1212 are respectively fitted outside the inlet section 141, that is, the injection channel 14 passes through the radially inner side of the damping cavity; the drain section 152 of the drain channel 15 extends axially along the cutter bar 1, and the drain section 152 passes between the first annular cavity 1211 and the third annular cavity 1221, and between the second annular cavity 1212 and the fourth annular cavity 1222, that is, the drain channel 15 passes through the radially outer side of the damping cavity (the first annular cavity 1211 and the second annular cavity 1212). Both the inlet section 141 and the drain section 152 axially penetrate the second rigid section 12, but are located radially inner and radially outer sides of the damping cavity, respectively, and are radially offset from the damping cavity, not occupying the same radial space. Meanwhile, the third rigid section 13 is equipped with a fluid injection section 142 and an inlet section 151. The fluid injection section 142 guides the cutting fluid from the inlet section 141 to the cutting area of ​​the tool tip, while the inlet section 151 introduces the cutting fluid carrying chips from the tool tip area into the drain section 152. The inlet section 151 is closer to the second rigid section 12 than the fluid injection section 142, creating a directional flushing path for the cutting fluid in the tool tip area, flowing backward from the tool tip, which facilitates timely chip removal. In this way, the cutting fluid delivery and damping functions can be spatially compatible without increasing the outer diameter of the tool holder 1.

[0045] Furthermore, it is understood that the radial dimensions, number of installations, and arrangement (e.g., evenly spaced along the circumference of the blade holder 1) of the injection section 142 and the drainage channel 15 of the present invention can be selected and adjusted according to actual conditions and requirements, and the present invention does not impose specific limitations on them.

[0046] In existing technologies, deep hole tool holders 1 are generally cylindrical with a constant outer diameter, maintaining this diameter throughout their axial length. While this design facilitates manufacturing, it is not optimal from a structural mechanics perspective. The end closest to the spindle experiences the greatest bending moment, yet there are no restrictions on the bore diameter at that point. Conversely, the end closest to the tool tip experiences a smaller bending moment but faces the most stringent restrictions on the bore diameter. The constant-diameter design means that the entire outer diameter of the tool holder 1 is limited by the minimum bore diameter, making it impossible to increase rigidity by increasing the diameter at the spindle end where the bending moment is greatest.

[0047] In view of this, in one embodiment of the present invention, the inner core 121 can be interference-fitted into the outer shell 122, and the outer diameter of the first rigid section 11 is... The outer diameter of the second rigid section 12 and the outer diameter of the third rigid section 13 satisfy: , .

[0048] In this embodiment, the outer diameter decreases in a stepped manner from the first rigid section 11 to the third rigid section 13. While the maximum outer diameter is limited by the narrowest through-hole diameter, the outer diameter of each section can be made as close as possible to its respective limit. The first rigid section 11 is located outside the workpiece and is not limited by the hole diameter, therefore its outer diameter is the largest. The second rigid section 12 needs to enter the workpiece but does not reach the narrowest through-hole section; its outer diameter is close to but slightly smaller than that of the first rigid section 11. The third rigid section 13 needs to pass through the narrowest through-hole section, therefore its outer diameter is the smallest. Thus, with this stepped outer diameter decreasing configuration, the tool holder 1 can obtain the largest possible moment of inertia for each section while meeting the through-hole requirements.

[0049] Meanwhile, the inner core 121 and the outer shell 122 are fitted with an interference fit. This interference fit allows pre-stress to be generated at the contact interface between the inner core 121 and the outer shell 122. This pre-stress prevents interface separation or relative slippage between the inner core 121 and the outer shell 122 under bending loads, allowing the two components to bear the bending load as a whole. Since the materials of the outer shell 122 and the inner core 121 can be selected separately (the outer shell 122 focuses on wear resistance and corrosion resistance, while the inner core 121 focuses on high elastic modulus), the equivalent cross-sectional stiffness of the combined material can exceed the cross-sectional stiffness of a single material with the same outer diameter. The stepped outer diameter allows each segment of the tool holder 1 to obtain the maximum cross-sectional moment of inertia within its respective confined space. The interference fit further enhances the equivalent stiffness of the composite cross-section of the tool holder 1. Thus, the overall static and dynamic stiffness of the tool holder 1 can be significantly enhanced, and the static bending deformation and dynamic vibration amplitude caused by cutting force can be reduced.

[0050] In one embodiment of the present invention, the substrate of the first rigid segment 11 can be set as powder metallurgy high-speed steel, and the outer wall of the first rigid segment 11 is coated with a tungsten carbide-cobalt cemented carbide gradient coating by hot isostatic pressing process, the thickness of the gradient coating gradually decreases along the direction from the second rigid segment 12 to the first rigid segment 11; the substrate of the third rigid segment 13 can be set as fully dense cemented carbide, and the outer diameter of the third rigid segment 13 gradually decreases along the direction from the second rigid segment 12 to the third rigid segment 13.

[0051] In this embodiment, the substrate of the first rigid section 11 is powder metallurgy high-speed steel, which has good toughness and impact resistance. Its outer wall is coated with a tungsten carbide-cobalt cemented carbide gradient coating through hot isostatic pressing. The hardness of this coating is much higher than that of the substrate, and it forms a metallurgical bond with the substrate through hot isostatic pressing, resulting in high interfacial bonding strength. More importantly, the thickness of the coating gradually decreases along the direction from the second rigid section 12 to the first rigid section 11 (i.e., from the root of the step to the end of the tool holder). The coating is thickest near the side of the second rigid section 12 (i.e., the root of the step, the position of maximum stress), which allows the highest strength of surface compressive stress reinforcement to be obtained at this position. The coating gradually thins near the end of the tool holder (where the stress has decreased), which can avoid material waste and prevent dimensional deviations caused by excessively thick coatings. Because the coefficient of thermal expansion of the cemented carbide coating is less than that of the steel substrate, the coating shrinks less than the substrate during the cooling process after hot isostatic pressing, forming residual compressive stress in the coating. This compressive stress can effectively offset the peak tensile stress generated on the surface by alternating bending loads, thereby delaying the initiation of fatigue cracks.

[0052] Meanwhile, the third rigid section 13 is made of fully dense cemented carbide, which has a much higher elastic modulus than steel, resulting in higher bending stiffness for the same cross-sectional dimensions. Furthermore, the outer diameter of the third rigid section 13 gradually decreases along the direction from the second rigid section 12 to the third rigid section 13 (i.e., from the root of the tool holder 1 towards the tool tip), forming a micro-taper. During deep hole machining, the tool holder 1 elastically retracts under radial cutting force. This micro-taper allows the larger diameter end of the third rigid section 13, closer to the second rigid section 12, to form a slight contact and compression with the machined hole wall after retraction, generating a self-guiding support effect. This shortens the effective overhang length of the tool holder 1, improves the equivalent support conditions, and helps reduce the static deflection and dynamic vibration amplitude at the tool tip.

[0053] In one embodiment of the present invention, the signal sensing unit 4 may include an acceleration sensor group 61, a cutting force sensor 62, a temperature sensor 63, a displacement sensor 64, a current sensor 65, and / or a voltage sensor 66. An acceleration sensor group 61 is mounted on the tool holder 1 to collect vibration signals of the tool holder 1; a cutting force sensor 62 is mounted on the tool holder 1 and located at the interface between the third rigid section 13 and the second rigid section 12 to collect cutting force signals during the cutting process; a temperature sensor 63 is mounted on the tool holder 1 to collect temperature signals of the tool holder 1; a displacement sensor 64 is mounted on the end of the spindle to collect spindle displacement signals; and a current sensor 65 and / or a voltage sensor 66 are used to collect current and / or voltage signals from the multi-axis linkage machining unit.

[0054] In this embodiment, the acceleration sensor group 61 is directly mounted on the tool holder 1, located at the forefront of the vibration transmission path. It can collect the original vibration signal of the tool holder 1 itself, avoiding signal attenuation and distortion through intermediate links such as the spindle bearing. The cutting force sensor 62 is mounted on the interface connecting the third rigid section 13 and the second rigid section 12. This position is the closest available mounting surface to the cutting area of ​​the tool head (the transmission path from the tool head to the sensor is only the length of the third rigid section 13, and the signal transmission path is the shortest). It does not need to pass through the connection interface between the tool holder 1 and the spindle, nor does it need to pass through the workpiece. Therefore, the phase delay between the collected cutting force signal and the actual force at the cutting point is extremely small, and the dynamic response is faster.

[0055] Temperature sensor 63 is mounted on tool holder 1 and monitors the temperature change of tool holder 1 during machining, providing real-time data on the axial thermal elongation of tool holder 1 caused by cutting heat. This data can be used to compensate for the impact of thermal deformation on machining accuracy. Displacement sensor 64 is mounted on the spindle end and monitors the radial runout and axial movement of the spindle end, providing a reference benchmark for distinguishing between the spindle's own motion error and the deformation error of tool holder 1. Current sensor 65 and / or voltage sensor 66 are mounted on the input ends of the drive motors of each axis of the multi-axis linkage machining unit, reflecting the load distribution of each axis. When abnormal fluctuations occur in the load of a certain axis, they can serve as an auxiliary basis for determining abnormal machining conditions.

[0056] According to a second aspect of the present invention, a vibration suppression method for deep hole machining of a nuclear power plant unloading device is also provided, applied to the vibration suppression structure for deep hole machining of a nuclear power plant unloading device according to any one of the technical solutions in the first aspect of the present invention, comprising the following steps: Step S1: System initialization, install the tool holder on the spindle end of the multi-axis linkage machining unit, clamp the workpiece to be processed, and load the machining process parameters and control algorithm parameters in the collaborative control unit; Step S2: Start the multi-axis linkage machining unit to perform deep hole cutting. The signal sensing unit collects multi-source signals in real time during the machining process and transmits them to the collaborative control unit. The multi-source signals include vibration signals, cutting force signals, temperature signals, displacement signals, and current signals and / or voltage signals of the multi-axis linkage machining unit. Step S3: Based on the received vibration signal, the collaborative control unit estimates the vibration state of the tool holder in real time through an extended Kalman filter vibration state observer. The vibration state includes the generalized displacement component and generalized velocity component of the first multi-mode, and extracts the vibration amplitude and vibration frequency of each mode. Based on the acquired cutting force signal, the dynamic cutting force component is calculated, and chatter is identified according to the dynamic cutting force component and the real-time estimated vibration amplitude to determine whether the alarm threshold is exceeded. If the alarm threshold is exceeded, emergency chatter suppression control is executed. Emergency chatter suppression control includes setting the excitation current of the first damping unit and the second damping unit to the maximum value, reducing the feed rate, and adjusting the spindle speed until the vibration amplitude falls back below the alarm threshold. Step S4: The collaborative control unit calculates the excitation current commands of the first damping unit and the second damping unit based on the real-time estimated vibration amplitude, vibration frequency and dynamic cutting force components, and sends them to the damping adjustment drive circuit. The damping adjustment drive circuit adjusts the actual excitation current of the first excitation coil group and the second excitation coil group through pulse width modulation to change the shear yield stress of the magnetorheological fluid and realize the real-time adjustment of the damping coefficient. Step S5: The collaborative control unit uses the real-time estimated radial vibration displacement of the tool holder as the feedforward compensation amount to correct the tool center point trajectory in real time, and sends the corrected trajectory command to the servo drives of each axis of the multi-axis linkage machining unit. S6: Repeat steps S2 to S5 until the current deep hole machining is completed. After machining is completed, machining quality information is generated.

[0057] Through the above technical solution, firstly, in this invention, the collaborative control unit estimates the vibration state of the tool holder in real time based on the vibration signal using an extended Kalman filter vibration state observer. The vibration state includes the generalized displacement and velocity components of the previous multi-mode vibrations, and extracts the vibration amplitude and frequency of each mode. Extended Kalman filtering, as an optimal state estimation method, works by using the system's state equation and observation equation. Through a recursive calculation of a prediction step (predicting the prior state estimate based on the previous estimate) and an update step (weighting and correcting the prior estimate using the measured observation at the current moment), under the condition that the noise statistical characteristics are known, the optimal displacement, velocity, and acceleration estimates are derived from the noisy acceleration measurements. This eliminates the need for additional displacement and velocity sensors; complete vibration state information can be obtained solely through an acceleration sensor. This provides accurate state input for subsequent damping control and trajectory compensation, avoiding noise amplification problems caused by signal differentiation or integration.

[0058] Secondly, in this invention, state estimation, chatter identification, dynamic cutting force calculation, and emergency control are executed within the same process node. The logical sequence is as follows: First, the extended Kalman filter observer extracts the vibration amplitude and frequency from the vibration signal, and simultaneously calculates the dynamic cutting force component from the cutting force signal; then, chatter identification is performed based on the dynamic cutting force component and the real-time estimated vibration amplitude to determine whether the alarm threshold is exceeded; if it is determined to exceed the threshold, emergency chatter suppression control is immediately executed (setting the excitation current of the first and second damping units to the maximum value to provide the maximum damping force, reducing the feed rate to decrease the cutting force excitation amplitude, and adjusting the spindle speed to deviate from the resonant frequency range). The above three measures are executed in parallel, without any time dependence between them, thus enabling synchronous completion in a very short time. In this way, chatter amplitude can be detected and suppressed when it is still in the early stages of growth (on the order of several micrometers) rather than when it has fully developed (on the order of tens to hundreds of micrometers), thus stopping chatter in its infancy and preventing the vibration amplitude from growing exponentially to a destructive level.

[0059] Third, in this invention, the collaborative control unit calculates the optimal excitation current command for each of the first and second damping units based on the real-time estimated vibration amplitude, vibration frequency, and dynamic cutting force component. The vibration amplitude reflects the severity of the current vibration (a larger amplitude requires a larger damping force), the vibration frequency determines the working mode matching of the damping units (the energy consumption efficiency of the two damping units differs at different frequencies, requiring dynamic adjustment of their output ratio), and the dynamic cutting force component reflects the fluctuation amplitude of the cutting excitation (a larger excitation fluctuation indicates a higher risk of chatter, requiring increased damping force reserve). The excitation current command output after fusing these three pieces of information is not a fixed value but is continuously adjusted according to the real-time changes in the processing state. This ensures that the damping coefficient setting always matches the current processing state, thereby avoiding a decrease in vibration suppression effect caused by deviations between the open-loop calibration value and the actual working conditions.

[0060] Fourth, in this invention, the damping adjustment drive circuit adjusts the actual excitation current of the first and second excitation coil groups through pulse width modulation (PWM). The working principle of PWM is as follows: within a fixed frequency carrier cycle, the average output current is changed by adjusting the proportion of the high-level conduction time to the entire cycle (the larger the conduction duty cycle, the higher the average output current). Its advantages are: the power switching device operates in a switching state (fully on or fully off), with extremely low conduction and cutoff losses, resulting in energy conversion efficiency far exceeding that of linear adjustment; simultaneously, the switching frequency is much higher than the natural frequency of the mechanical system, allowing the magnetic field generated by the excitation coil to be continuously adjustable in time rather than pulsating, thus ensuring a smooth and jitter-free output of the shear yield stress of the magnetorheological fluid. In this way, the excitation current can be adjusted within milliseconds, with a response speed far exceeding the characteristic time of changes in processing conditions, thereby achieving real-time stepless adjustment of the shear yield stress of the magnetorheological fluid.

[0061] Fifth, in this invention, the collaborative control unit uses the real-time estimated radial vibration displacement of the tool holder as a feedforward compensation amount to correct the tool center point trajectory in real time. That is, it achieves this by superimposing the radial vibration displacement in the vibration state onto the nominal tool center point trajectory command. When the vibration state observer estimates that the current tool holder has shifted by a certain displacement in the positive X direction, the command trajectory subtracts this offset in that direction, making the actual movement trajectory of the tool head approximate the nominal trajectory. Since the extended Kalman filter observer outputs the state estimate in real time, this compensation amount is updated in each sampling period. Therefore, the correction frequency of the tool center point trajectory is much higher than the highest frequency component of the tool holder vibration. In this way, the tool head displacement deviation caused by vibration can be actively offset from the control end, reducing the deviation between the actual and theoretical trajectories of the tool head in real time during machining, thus adding a suppression dimension of active trajectory compensation in addition to vibration energy dissipation.

[0062] Sixth, in this invention, step S6 is used as the loop feedback node, and steps S2 to S5 are repeated until the current deep hole machining is completed. The execution cycle of this loop is determined by the sampling cycle and the calculation time. In this way, the closed-loop control can continuously track the changes in the system state throughout the entire machining process and keep the tool holder vibration under control. Even if external disturbances (such as uneven material hardness, fluctuations in cutting fluid supply, etc.) cause sudden changes in the system state, the control loop can re-converge within several sampling cycles.

[0063] In one embodiment of the present invention, in step S3, the state equation and observation equation of the extended Kalman filter vibration state observer can be expressed as follows: In the formula, The state vector includes the generalized displacement and generalized velocity components of the tool holder's modal coordinates. for The first derivative with respect to time, The control input vector includes the excitation current control signal of the first damping unit and the second damping unit. Its covariance matrix is , For observation vectors; The observation matrix; The covariance matrix of the observation noise is: , For the system matrix, The input matrix; The prediction step of the extended Kalman filter is expressed as: The update step of the extended Kalman filter is represented as: In the formula, To utilize the first The estimated value at time t for the th The prior estimate of the state vector at time step [time]. For the first The posterior estimate of the state vector at time step [time]. For the first The error covariance matrix of the prior estimate at time step, For the first The error covariance matrix of the posterior estimate at time step [time]. For the first The posterior estimate of the state vector at time step [time]. For the first The error covariance matrix of the posterior estimate at time step [time]. For the first The Kalman gain matrix at time 10:00. For the first The state transition matrix at time t and , The discretized process noise covariance matrix is... The discretized observation noise covariance matrix is... It is the identity matrix. The sampling period.

[0064] In this implementation, the observer constructs a system model using the state equation and the observation equation, and calculates the optimal estimate of the state vector in real time through alternating recursive operations of prediction and update steps. During this process, the process noise covariance matrix Q and the observation noise covariance matrix R quantify the statistical characteristics of the system model error and sensor measurement error, respectively, and the Kalman gain matrix... The weights of the predicted and measured values ​​in the final estimation result are dynamically adjusted based on the ratio of Q to R. When sensor noise is high, the gain automatically decreases to weaken the influence of the measured values; when model uncertainty is high, the gain automatically increases to rely more on measured values ​​to correct the estimation results. In this way, over a timescale of tens of minutes to several hours during the continuous processing, the estimation results at each step integrate system model information and current measured information, allowing the state estimation values ​​to approximate the true values ​​across the entire frequency band. This provides accurate displacement, velocity, and acceleration information for subsequent damping control and trajectory compensation, avoiding the phase lag problem caused by filtering.

[0065] In this embodiment, it should be noted that, firstly, regarding the state equation and the observation equation, the state equation... It is a mathematical description of the physical motion laws of the tool holder system. Among them, the state vector... This includes the generalized displacement and generalized velocity components of the tool holder's modal coordinates (for example, if the first three modes are taken, then...). It contains displacement and velocity values ​​for each mode, totaling six components. System matrix A reflects the inherent characteristics of the tool holder system (system matrix A can be obtained by combining the mass matrix, damping matrix, and stiffness matrix), describing the evolution of the state vector over time in the absence of external control and noise; input matrix B describes the excitation current control signal. The degree of influence on the rate of change of system state (input matrix B can be obtained through experimental identification or finite element simulation). Process noise. This represents unmodeled disturbances in actual machining, such as cutting force fluctuations caused by uneven material hardness and additional excitations caused by cutting fluid impact. Observation equations This describes the mathematical relationship between sensor measurements and system state. The observation matrix H maps the state vector to the space of physical quantities measurable by the sensor (e.g., when the sensor is measuring acceleration, H extracts the acceleration components from the state vector and combines them into the output vector). Observation noise. This represents the inherent measurement errors of the sensor itself, including quantization error, temperature drift, electromagnetic interference, etc.

[0066] Second, regarding the prediction step, the prediction step The meaning is: using the first The posterior estimate at time t is derived up to the t based on the system dynamic equations. At time t, the prior estimate is obtained. This integration process is essentially solving the state equation over the time interval. The solution within the timeframe is the deduction of the system's expected state at the current moment based on the system state and control input from the previous moment. Error covariance prediction formula. This describes the propagation law of uncertainty in prior estimation. The P matrix represents the error covariance between the estimated and true values; the diagonal elements represent the estimation variance (i.e., uncertainty) of each state variable, and the off-diagonal elements represent the correlation of estimation errors between different state variables. State transition matrix. The error covariance from the previous time step is mapped to the current time step, while the process noise covariance... This reflects the new uncertainty introduced by the unmodeled disturbance.

[0067] Third, for the update step, the Kalman gain formula Used to calculate the weighting coefficients for predicted and measured values ​​in the final estimate. When the observation noise covariance... Relative to prediction error covariance When the value is large (i.e., the sensor measurement is unreliable), the item in parentheses Depend on Dominant, the inverse value is smaller, making The overall value is relatively small, and the update step relies more on the predicted value; conversely, when the value is relatively large, the update step relies more on the predicted value. When the value is relatively large (i.e., the model prediction is unreliable). The weights are too large, making the update step more dependent on the measured values. This weighting method can minimize the estimation error in a statistical sense. (State update formula) In the middle, residual term This represents the deviation between the measured and predicted values. Multiplying this deviation by the Kalman gain allows us to correct the predicted value, resulting in the posterior estimate. Error covariance update formula. This quantifies the degree to which uncertainty is reduced after the introduction of measurement information. Through the alternating recursion of the prediction and update steps described above, the observer can output a set of optimal estimates of the system state in each sampling period.

[0068] In one embodiment of the present invention, in step S3, the radial component, tangential component, and axial component of the dynamic cutting force can be expressed as follows: In the formula, The radial component of the dynamic cutting force component. This refers to the tangential component of the dynamic cutting force component. This refers to the axial component of the dynamic cutting force component. , and These are the radial, tangential, and axial cutting force coefficients, respectively (which can be obtained through standard cutting force coefficient calibration experiments). The cutting width (determined by tool geometry and axial depth of cut). For dynamic cutting thickness fluctuation and , For the tool rotation cycle, Main spindle speed This refers to the number of teeth on the cutting tool. The principal cutting edge angle (the angle between the main cutting edge of the tool and the feed direction); In step S4 of the present invention, the excitation current of the first damping unit and the second damping unit can be calculated according to the following control law: in, Corresponding to the first damping unit and the second damping unit respectively, Indicates the modal order. For the first Real-time excitation current of the damping unit and The first The minimum and maximum excitation currents of the damping unit, For the Sigmoid function, For the first Real-time vibration amplitude estimates for the first mode. For the first Real-time vibration frequency estimates of the first mode. Let be the Euclidean norm of the dynamic cutting force components. For the first The amplitude-frequency weighting coefficient of the damping element, For the first Force weighting coefficient of damping element.

[0069] In this embodiment, mathematical expressions for the dynamic cutting force components are given, wherein, This illustrates the core mechanism of regenerative chatter: the current cutting thickness is influenced by the surface ripples from the previous tool rotation cycle. When the system is in a stable cutting state... The amplitude of the dynamic cutting force component is close to zero, and the dynamic cutting force component is also close to zero. When the system approaches the chatter boundary, the ripple of the previous revolution and the cutting thickness fluctuation of the current revolution form positive feedback, and the amplitude of the dynamic cutting force component increases accordingly.

[0070] Simultaneously, this embodiment also provides a control law for the excitation current, namely, using the weighted sum of the vibration amplitude estimate and the dynamic cutting force norm as the input variable of the control law. The vibration amplitude term reflects the current severity of the vibration, while the dynamic cutting force term reflects the amplitude of the cutting excitation fluctuation. When the dynamic cutting force term increases first while the vibration amplitude has not yet increased significantly (early stage of chatter initiation), the control law still outputs a relatively high excitation current, achieving proactive suppression of chatter.

[0071] In this embodiment, it should be noted that, firstly, for the expression of dynamic cutting force components, they respectively correspond to the radial components. Tangential components and axial component Together they constitute the dynamic cutting force vector. The physical meaning of this set of expressions is: the dynamic fluctuation of the cutting force is equal to the product of the cutting force coefficient, the cutting width, and the dynamic cutting thickness fluctuation, and is based on the principal cutting edge angle. Projection allocation in all directions.

[0072] The core variable in the three expressions is the dynamic cutting thickness fluctuation. During rotary cutting, the radial vibration of the tool causes the instantaneous cutting thickness within the current rotation cycle to deviate from the nominal cutting thickness. Let the nominal cutting thickness be... The actual cutting thickness at the current rotation is ,but Because the surface ripples left on the hole wall by the previous cutter teeth directly affect the actual cutting thickness of the next cutter teeth, if the cutter head protrudes outward at that angle position in the previous revolution... If the actual cutting thickness of the cutting tooth at that angle position decreases by the same amount relative to the nominal value, then... Equal to the cutting thickness fluctuation at the same angular position in the previous revolution This relation This is the mathematical expression of regenerative chatter, namely, the surface ripples generated by vibration that occur during the tool rotation cycle. The delayed feedback is sent to the current cutting process, forming a closed positive feedback loop. The gain condition of this positive feedback loop (i.e., the system stability boundary) is jointly determined by the cutting force coefficient, cutting width, number of tool teeth, and frequency response function of the tool holder structure.

[0073] In addition, the cutting force coefficients in each direction , and These are material constants, determined by the shear strength of the workpiece material and geometric parameters such as the tool rake angle, and are typically obtained through standard cutting experiments. Cutting width. The principal cutting edge angle is determined by the tool geometry and axial depth of cut. This is the angle between the main cutting edge of the tool and the feed direction. (Product term) This represents the change in the cross-sectional area of ​​the undeformed chip caused by the fluctuation in cutting thickness. Multiplying this change by the corresponding cutting force coefficient yields the amplitude of the dynamic cutting force fluctuation in that direction.

[0074] Second, regarding the excitation current control law expression, which is used to calculate the real-time excitation current of each damping unit, its principle can be decomposed into the following levels: 1. Variable mapping layer (vibration amplitude term and dynamic cutting force norm term). The control law contains two input variables within parentheses, namely, the amplitude-frequency term ( ) and force parameters ( In the amplitude-frequency term, The product of these terms has the dimension of velocity, and its physical meaning is the vibration intensity of each mode. A larger amplitude and higher frequency indicate that the system needs to dissipate more vibrational energy per unit time, requiring a greater damping force. Therefore, a larger product value results in a higher excitation current output by the control law. The significance of summing the first three modes lies in the fact that the actual vibration of the tool holder is a superposition of multiple modes. Each mode has a different degree of harm to machining quality, but all must be suppressed. Summation allows the control law to comprehensively consider the contributions of all major modes. Force Variation Term The Euclidean norm of the dynamic cutting force component (i.e., the magnitude of the three-dimensional force vector) reflects the overall amplitude of the cutting excitation fluctuation. The larger this term is, the more severe the excitation source is, and the higher the damping force is required to resist it. Therefore, when this term increases, the control law also outputs a higher excitation current.

[0075] 2. Weighting layer (amplitude-frequency weighting coefficient) With force weighting coefficient ). and The weighting of the amplitude-frequency term and the force norm term in the final output are controlled separately. Both can be obtained through offline optimization calibration, and their values ​​differ in different damping units. For example, the first damping unit focuses on suppressing low-frequency bending vibrations, and its... The damping unit is relatively large; the subsequent damping unit focuses on suppressing high-frequency flutter. Relatively large.

[0076] 3. Normalized Output Layer (Sigmoid Function Mapping). Both the amplitude-frequency term and the force norm term are dimensionless; their weighted sum is input to the Sigmoid function. The Sigmoid function outputs a continuous value from 0 to 1, exhibits monotonically increasing characteristics, and saturates naturally at both ends of its domain. This saturation characteristic causes the output current of the control law to approach its minimum value when vibrations are small. To reduce unnecessary energy consumption, the output current approaches its maximum value when there is significant vibration. To provide maximum vibration damping, the current varies approximately linearly in the intermediate region. The output of this expression is multiplied by the current adjustment range. And add the minimum value Then, the excitation current command value with the dimension of current is obtained.

[0077] In one embodiment of the present invention, in step S3, the reduction of the feed rate can be performed according to the following formula: In the formula, For real-time feed rate, For nominal feed rate, The attenuation coefficient and , For real-time vibration amplitude, the weighted root mean square value of the amplitudes of the first multiple modes of vibration is taken. The preset vibration amplitude threshold; The spindle speed can be adjusted according to the following formula: In the formula, For real-time spindle speed, This is the nominal spindle speed. Main spindle speed adjustment amount For adjustment coefficient and , For real-time vibration frequency estimation, the dominant frequency components of the first few modal vibration frequencies are taken. Let be the natural frequency of the tool holder.

[0078] In this embodiment, during the emergency chatter suppression phase, the cutting force excitation is rapidly weakened and resonance avoided through exponential decay of the feed rate and frequency shift of the spindle speed, complementing damping suppression. Specifically, the feed rate decreases exponentially, with the decay coefficient determined by the relative deviation between the vibration amplitude and a preset threshold. The larger the deviation, the more significant the feed rate reduction, thus matching the adjustment amount with the severity of chatter. The spindle speed adjustment is determined by the relative deviation between the real-time vibration frequency and the tool holder's natural frequency, aiming to move the actual excitation frequency out of the resonance range and prevent the system from operating in a resonant state.

[0079] Meanwhile, it is understandable that the above two measures and the maximization adjustment of the damping coefficient in the previous scheme can be implemented in parallel, thereby forming a triple vibration suppression mechanism of increased damping energy consumption + weakened cutting excitation + resonance avoidance, so that flutter can be effectively suppressed in the shortest possible time.

[0080] In this embodiment, it should be noted that, firstly, the feed rate reduction formula is used to calculate the real-time feed rate reduction after chatter occurs. The input variable of the formula is the real-time vibration amplitude. Compared with the preset vibration amplitude threshold The relative deviation between them. When hour, exponent term The feed rate remains at the nominal value. Unchanged; when When the relative deviation is positive, the exponent term is less than 1, and the feed rate begins to decrease. (Attenuation coefficient) By controlling the sensitivity of the feed rate to the vibration amplitude deviation (the more severe the vibration amplitude deviation, the greater the reduction in feed rate), the amount of feed rate reduction can be matched with the severity of chatter: when chatter is mild, the feed rate is reduced moderately to maintain machining efficiency, and when chatter is severe, the feed rate is reduced significantly to quickly reduce the cutting force excitation.

[0081] Second, regarding the spindle speed fine-tuning formula, this formula is used to calculate the real-time adjustment amount of the spindle speed. The formula incorporates the estimated real-time vibration frequency. With the natural frequency of the tool holder Compare the two and calculate the relative deviation between them. near At this point, the system is in or near resonance, and the adjustment amount approaches zero, failing to effectively offset the resonance frequency. When the deviation between the two increases, the adjustment amount increases, causing the actual rotational speed to... It shifts away from the resonance point.

[0082] The principle behind this adjustment is: the natural frequency of the tool holder system. Determined by the structure's mass and stiffness distribution, the system's vibration response is significantly amplified when the cutting excitation frequency (usually related to the spindle speed) approaches the natural frequency. The formula drives speed adjustment by detecting the direction of deviation between the actual vibration frequency and the natural frequency; that is, it adjusts the spindle speed in the direction that causes the excitation frequency to deviate from the natural frequency. Adjustment coefficient. By controlling the step size of the adjustment, it is possible to prevent abrupt changes in the cutting state caused by excessively large single adjustments. In this way, after such adjustment, the operating point of the system can be shifted from near the resonant frequency to the stable region, thereby reducing the dynamic amplification effect of the cutting excitation on the tool holder system.

[0083] In one embodiment of the present invention, in step S5, the corrected tool center point trajectory command can be expressed as: In the formula, This is the corrected tool center point trajectory command vector. The nominal tool center point trajectory vector, This is the estimated vector of radial vibration displacement of the tool holder, containing vibration displacement components in the X and Y directions, which is extracted from the state vector by the extended Kalman filter vibration state observer.

[0084] In this embodiment, the vibration displacement is superimposed on the nominal trajectory command in reverse using a feedforward compensation method, thereby achieving real-time correction of the tool head trajectory without adding additional actuators. Specifically, the estimated radial vibration displacement in the vibration state is used as the compensation amount and subtracted from the nominal trajectory command. When the extended Kalman filter observer estimates that the current tool holder has shifted by a certain displacement in the positive X direction, this offset is subtracted in reverse from the trajectory command in the current sampling period, ensuring that the actual movement trajectory of the tool head always closely approximates the nominal trajectory. This correction is performed on a per sampling period (approximately 0.5 to 1 ms) basis, and its update frequency is much higher than the highest frequency component of the tool holder vibration, thus enabling real-time tracking and compensation of the vibration displacement. In this way, closed-loop correction of the tool head trajectory can be achieved directly at the interpolation level of the CNC system without adding additional physical actuators, forming a dual suppression path of vibration energy dissipation + motion trajectory correction together with the damping suppression in step S5.

[0085] In this embodiment, it should be noted that, for the corrected tool center point trajectory command, this formula is used to calculate the corrected tool center point trajectory command, and its principle is feedforward compensation. In the formula, The nominal tool center point trajectory vector is the theoretical trajectory generated by the CAD / CAM system without considering deformation during the machining process. This is the estimated vector of radial vibration displacement of the tool holder, containing vibration displacement components in the X and Y directions; This is the corrected actual command trajectory sent to each axis servo drive. The formula means that in each sampling cycle, the estimated radial vibration displacement of the tool holder at the current moment is subtracted from the nominal trajectory command to obtain the actual command trajectory for the next moment. When the extended Kalman filter observer estimates that the current tool holder has shifted by a certain amount in the positive X direction, the control unit adds this shift inversely to the trajectory command, allowing the tool to anticipate and compensate for this shift at the motion planning level. This correction process is continuously executed in units of each sampling cycle (approximately 0.5ms to 1ms), and its update frequency is much higher than the highest frequency component of the tool holder vibration. Therefore, the compensation amount can change synchronously with the vibration displacement. In this way, active correction of the tool head motion trajectory can be achieved at the interpolation level of the CNC system, ensuring that the actual motion trajectory of the tool head continuously approximates the nominal trajectory throughout the entire machining process.

[0086] It is understandable that this compensation method works in parallel with the vibration energy dissipation of the damping unit. The damping unit consumes vibration energy and reduces vibration amplitude at the physical level, while trajectory compensation offsets the influence of residual vibration on the tool head position at the motion planning level. The two constitute a dual suppression path of physical energy consumption + motion correction.

[0087] The technical solution of the present invention will be further explained below with reference to the deep hole machining of the housing of a nuclear power plant unloading device.

[0088] It should be noted that, in this exemplary embodiment, the housing material is SA-266 Gr.2 low-alloy steel, and the deep hole to be machined is a three-stage stepped hole. The first stage has a diameter of φ25.00mm and a depth of 300mm, the second stage has a diameter of φ23.75mm and a depth of 250mm, and the third stage has a diameter of φ22.50mm and a depth of 200mm, for a total hole depth of 750mm. The hole diameter tolerance requirement is ≤±0.02mm, and the surface roughness requirement is Ra≤0.4μm. The workpiece material hardness is approximately HB180~220, and the tensile strength is approximately 550MPa.

[0089] I. Configuration of vibration suppression structure.

[0090] 1. Tool holder structure.

[0091] Outer diameter of the first rigid section The outer diameter of the second rigid section The inner core has an outer diameter of 16mm, and the outer shell has an inner diameter of 16.5mm. The inner core and outer shell are interference-fitted with an interference amount of 0.03mm. The inner core material is YG6X cemented carbide, and the outer shell material is 0Cr17Ni4Cu4Nb stainless steel. The outer diameter of the third rigid section... Starting from the second rigid section connection end (23.4mm), the third rigid section tapers gradually at a 1:500 taper along the direction towards the tool tip, with a length of approximately 200mm. After tapering, the outer diameter of the tool tip is approximately 23.0mm. The substrate of the first rigid section is ASP2053 powder metallurgy high-speed steel, and the outer wall is coated with a WC-12Co gradient coating through a hot isostatic pressing process. The coating thickness gradually decreases to 2.5mm from the connection point with the second rigid section (3.5mm) towards the tool holder. The substrate of the third rigid section is YG10X fully dense cemented carbide.

[0092] 2. Injection channel and drainage channel.

[0093] The inlet section of the fluid injection channel extends axially along the tool holder, penetrating the inner core from the rear end of the first rigid section to the interior of the third rigid section. The first and second annular cavities are respectively fitted outside the inlet section. There are two fluid injection sections, one end of which communicates with the inlet section inside the third rigid section, and the other end extends to the peripheral wall of the third rigid section, used to deliver cutting fluid into the deep hole to be machined. There are four fluid drainage channels, evenly distributed along the circumference of the tool holder. The inlet section of the drainage channel is located on the peripheral wall of the third rigid section, used for the entry of cutting fluid and chips. The inlet section is located behind the fluid injection section (on the side closer to the root of the tool holder). The drainage channel extends axially, sequentially passing between the first and third annular cavities, and between the second and fourth annular cavities, with its rear end penetrating to the side of the first rigid section away from the second rigid section, guiding the cutting fluid carrying chips to the outside of the tool holder for recovery.

[0094] 3. Damping unit parameters.

[0095] The first annular cavity has a radial width of approximately 2.5 mm and an axial length of approximately 4.5 mm. The annular inertial mass is made of tungsten alloy with a density of 17.5 g / cm³, suspended in a magnetorheological fluid within the first annular cavity. The second annular cavity also has a radial width of approximately 2.5 mm and an axial length of approximately 4.5 mm. It is filled with several granular damping media (tungsten alloy particles, 0.8 mm to 1.2 mm in diameter, 80% filling rate), with the magnetorheological fluid impregnating the gaps between the particles. A third annular cavity is located within the outer shell and corresponds to the first annular cavity. A fourth annular cavity is also located within the outer shell and corresponds to the second annular cavity. A first excitation coil group is installed in the third annular cavity, and a second excitation coil group is installed in the fourth annular cavity. Each group contains four coils, each with three layers × 10 turns, a resistance of approximately 2.5 Ω, and a current adjustment range of 0 to 2.5 A. The magnetorheological fluid is a carbonyl iron powder-based magnetorheological fluid with a zero-field viscosity of 0.8 Pa·s.

[0096] 4. Sensor configuration.

[0097] An accelerometer sensor array is mounted on the tool holder. Four piezoelectric accelerometers (sensitivity 100mV / g, frequency response 0.5Hz to 10kHz) are evenly distributed circumferentially on the outer wall of the first rigid section, and three identical piezoelectric accelerometers are evenly distributed on the flange end face of the tool holder. The cutting force sensor is located at the interface between the third and second rigid sections on the tool holder and is a hollow annular triaxial piezoelectric force sensor (range 0 to 5000N, resolution 0.1N, natural frequency ≥5kHz). The temperature sensor is mounted on the tool holder and consists of three K-type thermocouples arranged 20mm apart on the outer wall of the second rigid section. The displacement sensor is located at the end of the spindle and is an eddy current displacement sensor (range 2mm, resolution 0.1μm). The current sensor and voltage sensor are located at the input end of the drive motors of each axis (Hall effect sensors, bandwidth ≥100kHz).

[0098] II. Implementation of vibration suppression methods for deep hole machining.

[0099] Step 1: System initialization.

[0100] Install the tool holder at the end of the spindle of the multi-axis linkage machining unit (BT50 taper shank tension), clamp the box-shaped workpiece to be machined, and perform alignment and tool setting.

[0101] Load the following parameters into the collaborative control unit: Machining parameters: Nominal spindle speed Nominal feed rate The cutting width b is determined by the tool geometry parameters (take b = 0.8 mm), the number of tool teeth N = 2, and the principal cutting edge angle... .

[0102] Control algorithm parameters: sampling period ; Initial covariance matrix of extended Kalman filter (state vector) The unit of displacement in this context is meters (m), and the unit of velocity is meters per second (m / s). Therefore... The dimensions of the diagonal elements are respectively and Process noise covariance Observation noise covariance Weighting coefficient of the first damping unit , The weighting coefficient of the second damping unit , , ; attenuation coefficient adjustment coefficient Vibration amplitude alarm threshold Vibration amplitude threshold The minimum current of both the first and second damping units is 0A, and the maximum current of both is 2.5A.

[0103] Step 2: Start processing and signal acquisition.

[0104] The spindle is started rotating at 1200 r / min, and the Z-axis drives the tool holder to penetrate the workpiece at a feed rate of 100 mm / min. The signal sensing unit samples at a frequency of 2 kHz. It can collect vibration signals, cutting force signals, temperature signals, displacement signals, and current and voltage signals of each axis drive motor in real time.

[0105] Taking the first second of processing as an example: the accelerometer measures the vibration acceleration in the X direction as approximately... Approximately in the Y direction Radial force measured by the cutting force sensor Tangential force Axial force The temperature sensor measured the tool holder temperature to be approximately 32℃; the displacement sensor measured the radial runout of the spindle end to be approximately 0.8μm; the current sensor measured the Z-axis drive motor current to be approximately 8.5A; and the voltage sensor measured the voltage to be approximately 220V.

[0106] Step 3: Vibration state estimation, dynamic cutting force calculation and chatter identification.

[0107] 1. Extended Kalman filter vibration state estimation.

[0108] After receiving the vibration signal, the collaborative control unit performs an extended Kalman filter recursive operation.

[0109] State vector We take the generalized displacement and generalized velocity of the first three modes, for a total of 6 dimensions. Starting from the initial time... For example: , (Displacement unit: m, velocity unit: m / s, corresponding to) The dimensions of the diagonal elements are respectively and ).

[0110] Prediction step ( , ): Suppose the current (Initial current is 0), the system matrix A can be determined by the tool holder structure parameters, and the first natural frequency is approximately 180Hz (corresponding to...). ), damping ratio The second natural frequency is approximately 520 Hz. ), damping ratio The third natural frequency is approximately 950 Hz. ), damping ratio Then A is a block diagonal matrix, and the matrices of each second-order subsystem are: .

[0111] After substituting, we get From the components, extract the amplitude and frequency of each modal vibration: , ; , ; , ; Error covariance prediction: ,in , This represents the discretized process noise covariance.

[0112] Update steps: First, calculate the Kalman gain: , where H is the observation matrix, which maps the state vector to the acceleration observations; Then, using the measured acceleration values... Update status: After iterating to a steady state, the amplitude and frequency of each mode vibration are output in real time. For example, the following values ​​were measured during the stable cutting phase: , ; , ; , Real-time vibration amplitude The first three weighted root mean squares are approximately 0.0032 mm.

[0113] 2. Calculation of dynamic cutting force.

[0114] Based on the triaxial force signal acquired by the cutting force sensor, the dynamic cutting force component is calculated (first, the acquired triaxial force signal is low-pass filtered to extract the static cutting force component, and then the instantaneous triaxial force is subtracted from the static component to obtain the dynamic cutting force component). Taking the current moment as an example, the measured instantaneous triaxial force value is... , , The static cutting force component (after low-pass filtering) is , , Then the dynamic cutting force components are: Euclidean norm of dynamic cutting force: 3. Flutter identification.

[0115] Compare real-time vibration amplitude With alarm threshold If the alarm threshold is not exceeded, continue with step S4 for normal control and do not trigger emergency suppression.

[0116] Step S4: Calculation of excitation current command and damping adjustment.

[0117] The collaborative control unit calculates the excitation current command based on the real-time estimated vibration amplitude, vibration frequency, and dynamic cutting force components.

[0118] Control law expression: ; in, These correspond to the first damping unit and the second damping unit, respectively. Indicates the modal order. The dimension is mm / s (rad is a dimensionless quantity).

[0119] For the first damping unit (m=1): ; ; ; ; Calculation yields ; For the second damping unit (m=2): ; ; ; ; Calculation yields ; After the calculation is completed, the co-control unit sends a current command to the damping adjustment drive circuit, which adjusts the actual excitation current of the first and second excitation coil groups to approximately 2.48A and 2.50A respectively using pulse width modulation. At an excitation current of 2.5A, the shear yield stress of the magnetorheological fluid increases to approximately 40kPa to 50kPa, causing the first damping unit to output a damping force of approximately 150N to 200N. The equivalent damping coefficient between particles in the second damping unit also increases significantly, together effectively suppressing the current vibration.

[0120] Step S5: Correction of tool center point trajectory.

[0121] The collaborative control unit uses the radial vibration displacement of the tool holder estimated by the extended Kalman filter observer as a feedforward compensation amount to correct the tool center point trajectory in real time.

[0122] The extended Kalman filter vibration state observer at the current moment starts from the state vector. Radial vibration displacement estimate extracted from The distances are approximately 0.002mm in the X direction and 0.001mm in the Y direction. This is the nominal tool center point trajectory command. The coordinates of the current interpolation point are (10.000mm, 5.000mm, -150.000mm).

[0123] Revised instructions: The corrected trajectory command is sent to the X, Y, and Z axis servo drives to compensate for vibration displacement in advance at the interpolation level, making the actual movement trajectory of the tool head closer to the nominal trajectory.

[0124] Step S6: Execute and terminate repeatedly.

[0125] Repeat steps S2 to S5. Taking the stepped transition as an example, when the cutter head enters the stepped transition area between the second section (φ23.75mm) and the first section (φ25.00mm), the sudden change in cutting width causes a short-term jump in cutting force. At this time, the radial force measured by the cutting force sensor jumps to about 780N, the dynamic cutting force norm increases to about 120N, and the vibration amplitude increases to about 0.012mm (close to the alarm threshold of 0.015mm). The control law then increases the excitation current output, the current of the first damping unit rises to 2.50A, the current of the second damping unit remains at 2.50A, and the feed rate is reduced to about 65mm / min according to the formula, while the spindle speed is finely adjusted to about 1180r / min. After successfully passing through the stepped transition, the vibration amplitude drops back to below about 0.004mm, the feed rate gradually recovers to 100mm / min, and the spindle speed recovers to 1200r / min.

[0126] The entire machining process lasted approximately 7.5 minutes (total hole depth 750 mm, average feed rate 100 mm / min).

[0127] After processing, the system generates processing quality information: the actual measured hole diameters are φ25.005mm (tolerance +0.005 / -0.000), φ23.748mm (tolerance -0.002 / -0.010), and φ22.508mm (tolerance +0.008 / -0.000), the measured surface roughness Ra is approximately 0.31μm to 0.35μm, and the roundness error is 0.003mm, which meets the processing requirements of the nuclear power plant unloading device box.

[0128] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A vibration suppression structure for deep hole machining in nuclear power plant unloading devices, characterized in that, include: A tool holder, comprising a first rigid section, a second rigid section, and a third rigid section connected in sequence; the first rigid section is used to mount on the spindle end of a multi-axis linkage machining unit, and the third rigid section is used to mount a tool head; the second rigid section comprises an inner core and an outer shell sleeved outside the inner core; the inner core contains a first annular cavity and a second annular cavity spaced apart; the outer shell contains a third annular cavity corresponding to the first annular cavity and a fourth annular cavity corresponding to the second annular cavity; The first damping unit includes a first excitation coil assembly installed in the third annular cavity, an annular inertial mass housed in the first annular cavity, and a magnetorheological fluid filled in the first annular cavity. The annular inertial mass is configured to be able to suspend in the first annular cavity. The second damping unit includes a second excitation coil assembly installed in the fourth annular cavity, a plurality of particulate damping media contained in the second annular cavity, and magnetorheological fluid filled in the second annular cavity. The plurality of particulate damping media are configured to be immersed in the magnetorheological fluid in the second annular cavity. The system includes a signal sensing unit and a collaborative control unit. The signal sensing unit is used to collect vibration signals, cutting force signals, temperature signals, displacement signals, and current and / or voltage signals of the multi-axis linkage machining unit during the machining process. The collaborative control unit is communicatively connected to the signal sensing unit, the first damping unit, and the second damping unit, respectively, and is used to control the damping coefficients of the first damping unit and the second damping unit according to the data collected by the signal sensing unit.

2. The vibration suppression structure for deep hole machining of nuclear power plant unloading devices according to claim 1, characterized in that, The cutter bar also includes an injection channel and several drainage channels; The fluid injection channel is formed within the first rigid section, the inner core, and the third rigid section. The fluid injection channel includes an inlet section and a plurality of injection sections. The inlet section extends along the axial direction of the tool holder. The first annular cavity and the second annular cavity are respectively sleeved outside the inlet section. One end of the inlet section extends into the third rigid section, and the other end of the inlet section extends to the side of the first rigid section away from the second rigid section. One end of the plurality of injection sections extends into the third rigid section and communicates with the inlet section. The other end of the plurality of injection sections extends to the peripheral wall of the third rigid section for conveying cutting fluid into the deep hole to be machined. A plurality of drainage channels are arranged circumferentially along the tool holder. Each drainage channel includes an inlet section and a drainage section extending axially along the tool holder. The drainage section is formed within the first rigid section, the outer shell, and the third rigid section. One end of the drainage section extends to the side of the first rigid section away from the second rigid section, and the other end extends into the third rigid section. The drainage section is sequentially disposed between the first annular cavity and the third annular cavity, and between the second annular cavity and the fourth annular cavity. One end of the inlet section extends into the third rigid section and communicates with the drainage section. The other end of the inlet section extends to the peripheral wall of the third rigid section for the entry of cutting fluid and chips. The inlet section is closer to the second rigid section than the injection section.

3. The vibration suppression structure for deep hole machining of nuclear power plant unloading devices according to claim 1, characterized in that, The inner core is interference-fitted within the outer shell, and the outer diameter of the first rigid section... The outer diameter of the second rigid section and the outer diameter of the third rigid segment satisfy: , .

4. The vibration suppression structure for deep hole machining of nuclear power plant unloading devices according to claim 1, characterized in that, The substrate of the first rigid segment is powder metallurgy high-speed steel, and the outer wall of the first rigid segment is coated with a tungsten carbide-cobalt hard alloy gradient coating by hot isostatic pressing. The thickness of the gradient coating gradually decreases along the direction from the second rigid segment to the first rigid segment. The matrix of the third rigid segment is made of fully dense cemented carbide, and the outer diameter of the third rigid segment gradually decreases along the direction from the second rigid segment to the third rigid segment.

5. The vibration suppression structure for deep hole machining of nuclear power plant unloading devices according to claim 1, characterized in that, The signal sensing unit includes: An accelerometer sensor array is mounted on the tool holder to collect vibration signals from the tool holder. A cutting force sensor is mounted on the tool holder and located at the interface between the third rigid section and the second rigid section, and is used to collect cutting force signals during the cutting process; A temperature sensor is mounted on the tool holder to collect the tool holder temperature signal; A displacement sensor is used to be mounted on the end of the spindle to collect spindle displacement signals; Current sensors and / or voltage sensors are used to acquire current signals and / or voltage signals of the multi-axis linkage machining unit.

6. A vibration suppression method for deep hole machining in nuclear power plant unloading devices, characterized in that, The vibration suppression structure applied to the deep hole machining of a nuclear power plant unloading device according to any one of claims 1 to 5 comprises the following steps: Step S1: System initialization, install the tool holder on the spindle end of the multi-axis linkage machining unit, clamp the workpiece to be processed, and load the machining process parameters and control algorithm parameters in the collaborative control unit; Step S2: Start the multi-axis linkage machining unit to perform deep hole cutting. The signal sensing unit collects multi-source signals during the machining process in real time and transmits them to the collaborative control unit. The multi-source signals include vibration signals, cutting force signals, temperature signals, displacement signals, and current signals and / or voltage signals of the multi-axis linkage machining unit. Step S3: Based on the received vibration signal, the collaborative control unit estimates the vibration state of the tool holder in real time through an extended Kalman filter vibration state observer. The vibration state includes the generalized displacement component and generalized velocity component of the first multi-mode, and extracts the vibration amplitude and vibration frequency of each mode. Based on the acquired cutting force signal, the dynamic cutting force component is calculated, and chatter is identified according to the dynamic cutting force component and the real-time estimated vibration amplitude to determine whether the alarm threshold is exceeded. If the alarm threshold is exceeded, emergency chatter suppression control is executed. The emergency chatter suppression control includes setting the excitation current of the first damping unit and the second damping unit to the maximum value, reducing the feed speed, and adjusting the spindle speed until the vibration amplitude falls back below the alarm threshold. Step S4: The collaborative control unit calculates the excitation current commands of the first damping unit and the second damping unit based on the real-time estimated vibration amplitude, vibration frequency and dynamic cutting force components, and sends them to the damping adjustment drive circuit. The damping adjustment drive circuit adjusts the actual excitation current of the first excitation coil group and the second excitation coil group through pulse width modulation to change the shear yield stress of the magnetorheological fluid and realize the real-time adjustment of the damping coefficient. Step S5: The collaborative control unit uses the real-time estimated radial vibration displacement of the tool holder as the feedforward compensation amount to correct the tool center point trajectory in real time, and sends the corrected trajectory command to the servo drives of each axis of the multi-axis linkage machining unit. S6: Repeat steps S2 to S5 until the current deep hole machining is completed. After machining is completed, machining quality information is generated.

7. The vibration suppression method for deep hole machining of nuclear power plant unloading devices according to claim 6, characterized in that, In step S3, the state equation and observation equation of the extended Kalman filter vibration state observer are respectively expressed as: In the formula, The state vector includes the generalized displacement and generalized velocity components of the tool holder's modal coordinates. for The first derivative with respect to time, The control input vector includes the excitation current control signal of the first damping unit and the second damping unit. Its covariance matrix is , For observation vectors; The observation matrix; The covariance matrix of the observation noise is: , For the system matrix, The input matrix; The prediction step of the extended Kalman filter is represented as follows: The update step of the extended Kalman filter is represented as follows: In the formula, To utilize the first The estimated value at time t for the th The prior estimate of the state vector at time step [time]. For the first The posterior estimate of the state vector at time step [time]. For the first The error covariance matrix of the prior estimate at time step, For the first The error covariance matrix of the posterior estimate at time step [time]. For the first The posterior estimate of the state vector at time step [time]. For the first The error covariance matrix of the posterior estimate at time step [time]. For the first The Kalman gain matrix at time 10:

00. For the first The state transition matrix at time t and , The discretized process noise covariance matrix is... This is the discretized observation noise covariance matrix. It is the identity matrix. The sampling period.

8. The vibration suppression method for deep hole machining of nuclear power plant unloading devices according to claim 6, characterized in that, In step S3, the radial, tangential, and axial components of the dynamic cutting force are respectively expressed as: In the formula, The radial component of the dynamic cutting force component. This refers to the tangential component of the dynamic cutting force component. This refers to the axial component of the dynamic cutting force component. , and These are the radial, tangential, and axial cutting force coefficients, respectively. For cutting width, For dynamic cutting thickness fluctuation and , For the tool rotation cycle, Main spindle speed This refers to the number of teeth on the cutting tool. The principal angle; In step S4, the excitation current of the first damping unit and the second damping unit is calculated according to the following control law: in, Corresponding to the first damping unit and the second damping unit respectively, Indicates the modal order. For the first Real-time excitation current of the damping unit and The first The minimum and maximum excitation currents of the damping unit, For the Sigmoid function, For the first Real-time vibration amplitude estimates for the first mode. For the first Real-time vibration frequency estimates of the first mode. Let be the Euclidean norm of the dynamic cutting force components. For the first The amplitude-frequency weighting coefficient of the damping element, For the first Force weighting coefficient of damping element.

9. The vibration suppression method for deep hole machining of nuclear power plant unloading devices according to claim 6, characterized in that, In step S3, the reduction of the feed rate is performed according to the following formula: In the formula, For real-time feed rate, For nominal feed rate, The attenuation coefficient and , For real-time vibration amplitude, the weighted root mean square value of the amplitudes of the first multiple modes of vibration is taken. The preset vibration amplitude threshold; The spindle speed is adjusted according to the following formula: In the formula, For real-time spindle speed, This is the nominal spindle speed. Main spindle speed adjustment amount For adjustment coefficient and , For real-time vibration frequency estimation, the dominant frequency components of the first few modal vibration frequencies are taken. Let be the natural frequency of the tool holder.

10. The vibration suppression method for deep hole machining of nuclear power plant unloading devices according to claim 6, characterized in that, In step S5, the corrected tool center point trajectory command is expressed as: In the formula, This is the corrected tool center point trajectory command vector. The nominal tool center point trajectory vector, The estimated value vector of the radial vibration displacement of the tool holder contains vibration displacement components in the X and Y directions, and is extracted from the state vector by the extended Kalman filter vibration state observer.

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