Thin-wall workpiece cutting force and displacement field reconstruction method and system based on single sensor

Abstract

According to the thin-wall workpiece cutting force and displacement field reconstruction method and system based on the single sensor, the elastic boundary constraint stiffness of the thin-wall workpiece is reversely identified through the modal frequency of the thin-wall workpiece, the identified elastic boundary constraint stiffness of the thin-wall workpiece is combined, the thin-wall workpiece analysis modal shape is calculated, and the cutting force and displacement field of the thin-wall workpiece are reconstructed. According to the method, a single sensor is used for measuring displacement, a mapping relation function of cutting force and displacement response is established, and the cutting force and a displacement field can be reconstructed by using the established mapping relation function of cutting force and displacement response according to the displacement measured by the single sensor. Single sensor reconstruction has higher reconstruction efficiency, better reliability and lower test cost, and the real-time performance and accuracy of online reconstruction are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field related to thin-walled workpieces, and in particular relates to a method and system for reconstructing cutting force and displacement fields of thin-walled workpieces based on a single sensor. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] Thin-walled workpieces are characterized by low stiffness and high deformation tendency. They are prone to frequent vibrations under the action of cutting forces, resulting in deviations in dimensional accuracy and surface integrity. Unlike high-rigidity workpieces, thin-walled workpieces exhibit complex dynamic behaviors during machining, such as local deformation and vibration. Technologies such as online error compensation and autonomous adjustment of machining parameters can effectively handle these complex dynamic behaviors. Online monitoring of geometric and physical quantities (such as cutting force and displacement) during machining is a prerequisite for the implementation of these technologies. Direct measurement of cutting forces and displacements involves high costs, which is not ideal in industrial applications. Therefore, the industry urgently needs simple and cost-effective alternative technologies: indirectly predicting cutting forces by measuring the response of the structure; indirectly predicting the displacement response at the cutting point or even the entire field of thin-walled workpieces using the vibration response of a limited number of measuring points.

[0004] During thin-wall machining, both cutting force and workpiece vibration response show time-varying and spatial distribution characteristics, and the frequency response function of the cutting point changes dynamically. Domestic and foreign scholars have proposed many methods to indirectly predict cutting force, such as predicting cutting force by measuring the vibration response of machine tool components through multiple sensors. Although cutting force can be effectively predicted in certain situations, it is limited by factors such as complexity, low signal-to-noise ratio and prediction bandwidth, which will lead to increased costs and reduced reliability. Using a single sensor for cutting force prediction is obviously a cost-effective and simple alternative, which reconstructs the cutting force in real time by inverse method from the vibration response of a single measurement point.

[0005] Indirectly predicting the displacement response of unmeasured locations of thin-walled structures using the responses of a small number of measured points remains a difficult problem in industry. The traditional finite element method is time-consuming and its accuracy depends largely on the quality of the mesh. In order to achieve online calculation without relying on finite elements, domestic and foreign scholars have proposed methods for online reconstruction of displacement fields based on modal superposition or modal expansion. These reconstruction methods require solving the pseudo-inverse matrix of the vibration mode. In order to make the system of equations computable, the number of sensors required must reach or exceed the number of modes of interest. For structures with complex or dense modes, more modes need to be superimposed to improve the reconstruction accuracy, so a large number of sensors are required. The current displacement field reconstruction technology has only reported relatively simple geometries (such as straight thin walls) and has not yet been extended to thin-walled cylindrical shells. When milling thin-walled cylindrical shells, the relative motion of the tool / workpiece is complex. This situation increases the difficulty of installing sensors at the cutting point and recording displacement data.

[0006] Therefore, it is of great significance to reconstruct the displacement field of thin-walled cylindrical shell including cutting points in real time using the measurement information of a single sensor for state monitoring of the milling process. Summary of the invention

[0007] In order to overcome the shortcomings of the above-mentioned prior art, the present invention provides a method and system for reconstructing the cutting force and displacement field of thin-walled workpieces based on a single sensor. The cutting force and displacement field can be reconstructed based on the measurement data of a single sensor. Compared with the multi-sensor reconstruction method, the single-sensor reconstruction has higher reconstruction efficiency, better reliability and lower testing cost, and improves the real-time and accuracy of online reconstruction.

[0008] In order to achieve the above object, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a method for reconstructing cutting force and displacement field of a thin-walled workpiece based on a single sensor, comprising:

[0010] Obtain the modal frequency, modal damping ratio and main mode vibration shape of thin-walled workpieces;

[0011] The modal frequency of the thin-walled workpiece is used to reversely identify the elastic boundary constraint stiffness of the thin-walled workpiece;

[0012] Combined with the identified elastic boundary constraint stiffness of the thin-walled workpiece, the analytical mode vibration shape of the thin-walled workpiece is calculated;

[0013] According to the calculated analytical modal vibration shape of the thin-walled workpiece, the mapping function between cutting force and displacement response is established by using the modal superposition method.

[0014] For the single measuring point displacement of the thin-walled workpiece during the machining process collected in real time, the corresponding cutting force and displacement field are reconstructed using the constructed mapping relationship function between cutting force and displacement response.

[0015] In a second aspect, the present invention provides a thin-walled workpiece cutting force and displacement field reconstruction system based on a single sensor, comprising:

[0016] An acquisition module, which is configured to: acquire the modal frequency, modal damping ratio and main modal vibration shape of the thin-walled workpiece;

[0017] A reverse identification module, which is configured to: reversely identify the elastic boundary constraint stiffness of the thin-walled workpiece using the modal frequency of the thin-walled workpiece;

[0018] A calculation module is configured to: calculate the analytical mode shape of the thin-walled workpiece in combination with the identified elastic boundary constraint stiffness of the thin-walled workpiece;

[0019] A construction module is configured to: establish a mapping relationship function between cutting force and displacement response by using a modal superposition method according to the calculated analytical modal vibration shape of the thin-walled workpiece;

[0020] The reconstruction module is configured to reconstruct the corresponding cutting force and displacement field using the mapping relationship function between the cutting force and the displacement response for the single measuring point displacement of the thin-walled workpiece collected in real time during the processing.

[0021] In a third aspect, the present invention provides an electronic device comprising a memory and a processor, and computer instructions stored in the memory and executed on the processor, wherein when the computer instructions are executed by the processor, the method described in the first aspect is performed.

[0022] In a fourth aspect, the present invention provides a computer-readable storage medium for storing computer instructions, wherein when the computer instructions are executed by a processor, the method described in the first aspect is performed.

[0023] In a fifth aspect, the present invention provides a computer program product, comprising a computer program, which, when executed by a processor, implements the method described in the first aspect.

[0024] One or more of the above technical solutions have the following beneficial effects:

[0025] The present invention reversely identifies the elastic boundary constraint stiffness of a thin-walled workpiece through the modal frequency of the thin-walled workpiece, calculates the analytical modal vibration type of the thin-walled workpiece in combination with the identified elastic boundary constraint stiffness of the thin-walled workpiece, and then establishes a mapping relationship function between the cutting force and the displacement response. According to the displacement measured by a single sensor, the cutting force and displacement field can be reconstructed using the constructed mapping relationship function between the cutting force and the displacement response. Compared with the multi-sensor reconstruction method, the single-sensor reconstruction has higher reconstruction efficiency, better reliability and lower testing cost, and improves the real-time and accuracy of the online reconstruction.

[0026] Advantages of additional aspects of the present invention will be given in part in the following description, and in part will become obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0028] Figure 1 This is a single sensor online reconstruction framework diagram in the first embodiment of the present invention;

[0029] Figure 2 is a schematic diagram of modal frequencies of experimental modal analysis in Example 1 of the present invention;

[0030] Figure 3 Schematic diagram of the main modal vibration shape of the experimental modal analysis in the first embodiment of the present invention;

[0031] Figure 4 is a schematic diagram of the analytical modal vibration shape calculated in the first embodiment of the present invention;

[0032] Figure 5(a)-Figure 5(h) It is a schematic diagram of the reconstruction results of the cutting force and displacement field in the first embodiment of the present invention. DETAILED DESCRIPTION

[0033] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0034] It should be noted that the terms used herein are for describing specific embodiments only and are not intended to be limiting of exemplary embodiments according to the present invention.

[0035] In the absence of conflict, the embodiments of the present invention and the features of the embodiments may be combined with each other.

[0036] Embodiment 1

[0037] This embodiment discloses a method for reconstructing cutting force and displacement field of a thin-walled workpiece based on a single sensor, comprising:

[0038] Obtain the modal frequency, modal damping ratio and main mode vibration shape of thin-walled workpieces;

[0039] The modal frequency of the thin-walled workpiece is used to reversely identify the elastic boundary constraint stiffness of the thin-walled workpiece;

[0040] Combined with the identified elastic boundary constraint stiffness of the thin-walled workpiece, the analytical mode vibration shape of the thin-walled workpiece is calculated;

[0041] According to the calculated analytical modal vibration shape of the thin-walled workpiece, the mapping function between cutting force and displacement response is established by using the modal superposition method.

[0042] For the single measuring point displacement of the thin-walled workpiece during the machining process collected in real time, the corresponding cutting force and displacement field are reconstructed using the constructed mapping relationship function between cutting force and displacement response.

[0043] Combine the following Figure 1-Figure 4 A method for reconstructing the cutting force and displacement field of a thin-walled workpiece based on a single sensor proposed in this embodiment is described in detail, specifically including:

[0044] Step S1: For a given machine tool workpiece system, taking a thin-walled cylindrical shell as an example, the modal frequency, modal damping ratio and main modal vibration shape of the thin-walled cylindrical shell are measured through modal experiments.

[0045] In this embodiment, the frequency response function curve of the thin-walled cylindrical shell is obtained through modal experiment. Figure 2 The PolyMAX method is used to extract the modal frequency, modal damping ratio and main modal vibration shape of the thin-walled cylindrical shell in the experimental modal analysis. The main modal vibration shape is shown in Figure 3 As shown;

[0046] Step S2: The elastic boundary constraint stiffness of the thin-walled cylindrical shell is usually unknown and cannot be measured directly, so the frequency inverse identification obtained from the modal analysis experiment is used.

[0047] The initial value of the constraint stiffness is random, and the objective function J is defined as:

[0048]

[0049] Among them, f c To calculate the frequency, f e is the measured frequency, and n is the circumferential wave number of the cylindrical shell. The spring stiffness of the elastic boundary constraint has a greater impact on the low-order modes of the thin-walled cylindrical shell, but has a smaller impact on the high-order modes. Therefore, the first five modal frequencies measured in the experiment are used to adjust the boundary spring and And minimize the objective function. Particle swarm optimization algorithm is used to perform random global search on the objective function J to determine the stiffness parameters of the thin-walled cylindrical shell under elastic boundary conditions.

[0050] Step S3: Combined with the identified elastic boundary constraint stiffness, the analytical mode vibration shape of the thin-walled cylindrical shell is calculated as follows: Figure 4 shown.

[0051] The displacement components of the mid-surface of the thin-walled cylindrical shell along the x, θ, and z directions are denoted as u0, v0, and w0, respectively, and the rotations around the x-axis and θ-axis are denoted as φ θ and φ x .

[0052] The first-order shear deformation theory and wave method are used to calculate the analytical modal vibration function, which is expressed as:

[0053]

[0054] Among them, Φ n (x,θ)=[u 0n (x,θ),v 0n (x,θ),w 0n (x,θ),φ xn (x,θ),φ θn (x,θ)] T is the nth mode shape, and (x,θ) represents the position of the x, θ coordinates of the cylindrical shell.

[0055] Step S4, superimposing the analytical mode shapes to obtain the unit force-induced response, establishing a mapping relationship between the cutting force and the displacement response, and storing it offline in a database.

[0056] The specific formula is as follows:

[0057] The cutting force amplitude is f, and the tool moves at a constant angular velocity Ω, then the time-varying cutting force F is expressed as:

[0058] F(x,θ,t)=f·δ(x * )δ(θ-θ * -Ωt)(3)

[0059] where δ() is the Dirac function. * and θ * is the position of the cutting point at t=0.

[0060] Assuming that the sampling interval is Δt, the force amplitude can be approximated as the time-varying constant f(k) in the M+1 segment. Using the modal superposition method, the mapping relationship between force and displacement response is as follows:

[0061]

[0062] Where M is the number of sampling points, is the unit force-induced displacement response coefficient, as follows:

[0063]

[0064]

[0065] Where N is the cutoff wave number; Ω represents the angular velocity of the tool movement; L, ρ, h, r are the length, density, thickness and average radius of the cylindrical shell respectively; ξ n ,ω n and represent the modal damping ratio, natural frequency and lag phase of the nth mode respectively; w 0n (x) is the nth axial mode shape of the displacement component w0.

[0066] Step S5, using a single displacement sensor (such as model ZA-210500, sensitivity 8V / mm) in conjunction with a data acquisition system (DH5922D) to collect a single measuring point vibration signal on the thin-walled cylindrical shell during the processing process, and the collected signal is transmitted to a computer via a data line;

[0067] Step S6, inputting the displacement signal collected in real time into the mapping relationship function, and reconstructing the cutting force and displacement field of the thin-walled cylindrical shell online.

[0068] The calculation method is as follows:

[0069] In cylindrical shell (x r ,θ r ) is arranged at a single displacement sensor with a sampling interval of Δt. The displacement measured by the sensor at t = kΔt is w0(x r ,θ r , k), input into the mapping function, and reconstruct the cutting force f at this time:

[0070]

[0071] The reconstructed cutting force is input into the mapping function again to reconstruct the displacement of the unknown position. In a cutting test, the result of single sensor reconstruction is as follows: Figure 5(a)-Figure 5(h) As shown, the method successfully captures the cutting force and workpiece displacement field, verifying the effectiveness of the method described in this embodiment.

[0072] It should be noted that this method first uses the vibration response of limited measuring points to reversely reconstruct the cutting force, and then uses the reconstructed cutting force to forwardly reconstruct the full-field displacement response.

[0073] Embodiment 2

[0074] The purpose of this embodiment is to provide a thin-wall workpiece cutting force and displacement field reconstruction system based on a single sensor, comprising:

[0075] An acquisition module, which is configured to: acquire the modal frequency, modal damping ratio and main modal vibration shape of the thin-walled workpiece;

[0076] A reverse identification module, which is configured to: reversely identify the elastic boundary constraint stiffness of the thin-walled workpiece using the modal frequency of the thin-walled workpiece;

[0077] A calculation module is configured to: calculate the analytical mode shape of the thin-walled workpiece in combination with the identified elastic boundary constraint stiffness of the thin-walled workpiece;

[0078] A construction module is configured to: establish a mapping relationship function between cutting force and displacement response by using a modal superposition method according to the calculated analytical modal vibration shape of the thin-walled workpiece;

[0079] The reconstruction module is configured to reconstruct the corresponding cutting force and displacement field using the mapping relationship function between the cutting force and the displacement response for the single measuring point displacement of the thin-walled workpiece collected in real time during the processing.

[0080] In further embodiments, there is also provided:

[0081] An electronic device includes a memory and a processor, and computer instructions stored in the memory and executed on the processor, wherein when the computer instructions are executed by the processor, the method described in Embodiment 1 is performed. For the sake of brevity, no further description is given here.

[0082] It should be understood that in this embodiment, the processor may be a central processing unit CPU, and the processor may also be other general-purpose processors, digital signal processors DSP, application-specific integrated circuits ASIC, off-the-shelf programmable gate arrays FPGA or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc.

[0083] The memory may include a read-only memory and a random access memory, and provide instructions and data to the processor. A portion of the memory may also include a non-volatile random access memory. For example, the memory may also store information about the device type.

[0084] A computer-readable storage medium is used to store computer instructions. When the computer instructions are executed by a processor, the method described in embodiment 1 is completed.

[0085] The method in the first embodiment can be directly embodied as a hardware processor, or a combination of hardware and software modules in the processor. The software module can be located in a mature storage medium in the field such as a random access memory, a flash memory, a read-only memory, a programmable read-only memory, or an electrically erasable programmable memory, a register, etc. The storage medium is located in the memory, and the processor reads the information in the memory and completes the steps of the above method in combination with its hardware. To avoid repetition, it will not be described in detail here.

[0086] A computer program product includes a computer program, and when the computer program is executed by a processor, the method described in the first embodiment is implemented.

[0087] The present invention also provides at least one computer program product tangibly stored on a non-transitory computer-readable storage medium. The computer program product includes computer executable instructions, such as instructions included in a program module, which are executed in a device on a real or virtual processor of the target to perform the process / method as described above. Typically, program modules include routines, programs, libraries, objects, classes, components, data structures, etc. that perform specific tasks or implement specific abstract data types. In various embodiments, the functions of program modules can be combined or divided between program modules as needed. Machine executable instructions for program modules can be executed in local or distributed devices. In distributed devices, program modules can be located in local and remote storage media.

[0088] The computer program code for implementing the method of the present invention can be written in one or more programming languages. These computer program codes can be provided to the processor of a general-purpose computer, a special-purpose computer or other programmable data processing device, so that the program code, when executed by the computer or other programmable data processing device, causes the function / operation specified in the flow chart and / or block diagram to be implemented. The program code can be executed completely on a computer, partially on a computer, as an independent software package, partially on a computer and partially on a remote computer or completely on a remote computer or server.

[0089] In the context of the present invention, computer program codes or related data may be carried by any appropriate carrier to enable a device, apparatus or processor to perform the various processes and operations described above. Examples of carriers include signals, computer readable media, etc. Examples of signals may include electrical, optical, radio, acoustic or other forms of propagation signals, such as carrier waves, infrared signals, etc.

[0090] Those of ordinary skill in the art will appreciate that the units and algorithm steps of each example described in conjunction with this embodiment can be implemented in electronic hardware or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0091] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without creative work are still within the scope of protection of the present invention.

Claims

1. A method for reconstructing cutting force and displacement fields of thin-walled workpieces based on a single sensor, characterized in that: include: Obtain the modal frequency, modal damping ratio and main mode vibration shape of thin-walled workpieces; The modal frequency of the thin-walled workpiece is used to reversely identify the elastic boundary constraint stiffness of the thin-walled workpiece; Combined with the identified elastic boundary constraint stiffness of the thin-walled workpiece, the analytical mode vibration shape of the thin-walled workpiece is calculated; According to the calculated analytical modal vibration shape of the thin-walled workpiece, the mapping function between cutting force and displacement response is established by using the modal superposition method. For the single measuring point displacement of the thin-walled workpiece during the machining process collected in real time, the corresponding cutting force and displacement field are reconstructed using the constructed mapping relationship function between cutting force and displacement response.

2. A method for reconstructing cutting force and displacement field of a thin-walled workpiece based on a single sensor as claimed in claim 1, characterized in that: The modal frequency of the thin-walled workpiece is used to inversely identify the elastic boundary constraint stiffness of the thin-walled workpiece, specifically: Constructing the objective function based on the modal frequencies measured in the modal analysis experiment; Based on the fact that the elastic boundary constraint stiffness has a greater impact on the low-order modes of thin-walled workpieces than on the high-order modes, the particle swarm optimization algorithm is used to solve the elastic boundary constraint stiffness of thin-walled workpieces with the goal of minimizing the constructed objective function.

3. A method for reconstructing cutting force and displacement field of a thin-walled workpiece based on a single sensor as claimed in claim 1, characterized in that: The analytical modal vibration shape is calculated using the first-order shear deformation theory and the wave method. The analytical modal vibration shape is specifically: Among them, Φ n (x,θ)=[u 0n (x,θ),v 0n (x,θ),w 0n (x,θ),φ xn (x,θ),φ θn (x,θ)] T is the nth mode vibration shape. The displacement components of the mid-surface of the thin-walled workpiece along the x, θ, and z directions are recorded as u0, v0, and w0, respectively. The rotation of the mid-surface of the thin-walled workpiece around the x-axis and the θ-axis is marked as φ. θ and φ x .

4. A method for reconstructing cutting force and displacement field of a thin-walled workpiece based on a single sensor as claimed in claim 1, characterized in that: According to the calculated analytical modal vibration shape of the thin-walled workpiece, the mapping function between cutting force and displacement response is established by using the modal superposition method, which is as follows: The time-varying cutting force is constructed based on the cutting force amplitude and the angular velocity of the tool movement; The mode superposition method is used to construct the mapping function between cutting force and displacement response based on the unit force-induced displacement response coefficient and cutting force.

5. A method for reconstructing cutting force and displacement field of a thin-walled workpiece based on a single sensor as claimed in claim 1 or 4, characterized in that: The mapping function between cutting force and displacement response constructed is as follows: in, is the unit force-induced displacement response coefficient; M is the number of sampling points; w0 is the displacement component of the middle surface of the thin-walled workpiece along the z direction, and f(k) is a time-varying constant.

6. A method for reconstructing cutting force and displacement field of a thin-walled workpiece based on a single sensor as claimed in claim 1, characterized in that: The displacement of the thin-walled workpiece during the machining process collected in real time is input into the mapping relationship function between the cutting force and the displacement response to reconstruct the cutting force; the reconstructed cutting force is then input into the mapping relationship function between the cutting force and the displacement response to reconstruct the unknown displacement response.

7. A thin-wall workpiece cutting force and displacement field reconstruction system based on a single sensor, characterized in that: include: An acquisition module, which is configured to: acquire the modal frequency, modal damping ratio and main modal vibration shape of the thin-walled workpiece; A reverse identification module, which is configured to: reversely identify the elastic boundary constraint stiffness of the thin-walled workpiece using the modal frequency of the thin-walled workpiece; A calculation module is configured to: calculate the analytical mode shape of the thin-walled workpiece in combination with the identified elastic boundary constraint stiffness of the thin-walled workpiece; A construction module is configured to: establish a mapping relationship function between cutting force and displacement response by using a modal superposition method according to the calculated analytical modal vibration shape of the thin-walled workpiece; The reconstruction module is configured to reconstruct the corresponding cutting force and displacement field using the mapping relationship function between the cutting force and the displacement response for the single measuring point displacement of the thin-walled workpiece collected in real time during the processing.

8. An electronic device, characterized in that: The method comprises a memory and a processor and computer instructions stored in the memory and executed on the processor, wherein when the computer instructions are executed by the processor, the method according to any one of claims 1 to 6 is completed.

9. A computer-readable storage medium, characterized in that: Used to store computer instructions, which, when executed by a processor, complete the method described in any one of claims 1 to 6.

10. A computer program product, characterized in that The invention comprises a computer program, which, when executed by a processor, implements the method according to any one of claims 1 to 6.

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