Ultraprecise cutting method for microstructure

Abstract

The invention discloses a micro-structure ultra-precision cutting method, and relates to the technical field of ultra-precision machining. Comprising the following steps that a contour error pre-compensation model is constructed based on an overall transfer function of a tool servo system, and the tool servo system comprises a fast tool servo system and a slow tool servo system; based on a frequency decomposition method, decomposing a processing track obtained by the contour error pre-compensation model to obtain a high-frequency small-amplitude track and a low-frequency large-amplitude track; and the high-frequency small-amplitude track is sent to a fast tool servo system, and the low-frequency large-amplitude track is sent to a slow tool servo system for cutting machining. According to the method, the requirement for machining precision can be met while the machining efficiency of the complex curved surface microstructure is guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of ultra-precision machining, and in particular to a microstructure ultra-precision cutting method. Background Art

[0002] Complex curved surface microstructures are widely used in optical applications. In order to ensure their application performance, higher requirements are placed on the processing accuracy of curved surface microstructures. Compared with the processing of flat parts, curved surface microstructures have larger strokes, more frequency components, and more complex motion trajectories. In the existing technology, it is difficult to complete the processing of such components and meet the processing accuracy requirements of curved surface microstructures only through the machine tool slow tool servo system (Slow tool servo, abbreviated as STS, which is controlled by the XZC three-axis closed-loop servo linkage, with Z-axis reciprocating motion combined with C-axis rotation and X-axis feed to achieve cutting and creation of complex surfaces) or the following error compensation method (through real-time monitoring and compensation of the deviation between the actual output of the system and the instruction target (i.e., "following error"), thereby reducing tracking lag or steady-state error). Summary of the Invention

[0003] In response to the technical problem that the existing technology cannot meet the requirements of use in the processing accuracy of complex curved surface microstructures, the present invention provides a microstructure ultra-precision cutting method that can ensure the processing efficiency of complex curved surface microstructures while meeting the requirements of processing accuracy.

[0004] The present invention is achieved through the following technical solutions:

[0005] The present invention provides a microstructure ultra-precision cutting method, comprising the following steps:

[0006] Based on the overall transfer function of the tool servo system, a contour error compensation model is constructed, wherein the tool servo system includes a fast tool servo system and a slow tool servo system;

[0007] Decomposing the machining trajectory obtained by the contour error pre-compensation model based on a frequency decomposition method to obtain a high-frequency small-amplitude trajectory and a low-frequency large-amplitude trajectory;

[0008] The high-frequency and small-amplitude trajectory is sent to a fast tool servo system, and the low-frequency and large-amplitude trajectory is sent to a slow tool servo system for cutting processing.

[0009] The microstructure ultra-precision cutting method provided by the present invention first constructs a contour error pre-compensation model based on the overall transfer function of the tool servo system including the fast tool servo system and the slow tool servo system, which can reduce the contour error. Then, the processing trajectory obtained by the contour error pre-compensation model is decomposed based on the frequency decomposition method to obtain a high-frequency small-amplitude trajectory and a low-frequency large-amplitude trajectory. Finally, the high-frequency small-amplitude trajectory is sent to the fast tool servo system, and the low-frequency large-amplitude trajectory is sent to the slow tool servo system for cutting processing. In this way, ultra-precision turning processing is achieved through the fast tool servo while meeting the stroke conditions to obtain a higher-precision processed part.

[0010] Therefore, the microstructure ultra-precision cutting method provided by the present invention can ensure the processing efficiency of complex curved surface microstructures while meeting the requirements of processing accuracy.

[0011] Specifically, when constructing the contour error pre-compensation model, the contour error after processing, the input trajectory of the machine tool Z axis after pre-compensation, and the actual output position are calculated according to the accuracy prediction model.

[0012] Specifically, the contour error E after processing is P For E P =Z in -Z out ;

[0013] The input trajectory after pre-compensation of the machine tool Z axis is Z in1 =Z in -E P ;

[0014] The actual output location is:

[0015]

[0016] Where G all '(s) is the overall transfer function of the tool servo system.

[0017] Specifically, the contour error after pre-compensation is E p1 (s)=Z in (s)-Z p1 (s)=E P (s)(1-G' all (s)).

[0018] Specifically, the contour error pre-compensation model is a multiple-iteration pre-compensation model.

[0019] Specifically, the contour error after N compensations is E pN (s)=Z in (s)-Z pN (s)=E P (s)(1-G'all (s)) N .

[0020] Specifically, the iterative pre-compensation value of the contour error pre-compensation model is Z cN (s)=-E P (s)-E P (s)(1-G' all (s))-......-E P (s)(1-G' all (s)) N-1 .

[0021] Specifically, the calculation model of the high-frequency small-amplitude trajectory is: FTS =Z in -Z STS ;

[0022] The calculation model of the low-frequency and large-amplitude trajectory is: STS =FFT -1 (G f (f)Z in (f));

[0023] Among them, FFT -1 is the inverse fast Fourier transform, Z in (f) is the fast Fourier transform result of the Z-axis trajectory, G f (z) is the transfer function of the low-pass filter after z-transformation.

[0024] Specifically, in the process of decomposing the machining trajectory obtained by the contour error pre-compensation model based on the frequency decomposition method, the passband cutoff frequency is 15 Hz and the stopband cutoff frequency is 17 Hz.

[0025] Specifically, before cutting, it is determined whether the processing of the curved surface microstructure meets the execution capability of the fast tool servo system;

[0026] If the overall stroke is less than the fast tool servo stroke, the execution capability of the fast tool servo system is further judged by the machining trajectory frequency. If the frequency meets the fast tool execution capability, fast tool servo machining is performed and contour error evaluation is carried out. If the frequency does not meet the requirement, the machining parameters are adjusted, the theoretical tool machining trajectory is re-extracted, and the above judgment process is repeated.

[0027] If the overall stroke is greater than the fast tool stroke, the trajectory is decomposed based on the frequency decomposition method. The decomposed trajectory is sent to the fast and slow tool servo systems respectively to verify whether the stroke meets the requirements;

[0028] If the travel is satisfied, compound processing is carried out through the tool servo system;

[0029] If the stroke does not meet the stroke requirements of each part of the tool servo system, the processing parameters should be modified.

[0030] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0031] The microstructure ultra-precision cutting method provided by the present invention first constructs a contour error pre-compensation model based on the overall transfer function of the tool servo system including the fast tool servo system and the slow tool servo system, which can reduce the contour error, and then decomposes the processing trajectory obtained by the contour error pre-compensation model based on the frequency decomposition method to obtain a high-frequency small-amplitude trajectory and a low-frequency large-amplitude trajectory. Finally, the high-frequency small-amplitude trajectory is sent to the fast tool servo system, and the low-frequency large-amplitude trajectory is sent to the slow tool servo system for cutting processing. In this way, ultra-precision turning processing is achieved through the fast tool servo while meeting the stroke conditions to obtain higher-precision processed parts, which can ensure the processing efficiency of complex curved surface microstructures while meeting the processing accuracy requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0033] in:

[0034] Figure 1 A schematic flow chart of a microstructure ultra-precision cutting method according to an embodiment of the present invention;

[0035] Figure 2 Schematic diagram of a contour error pre-compensation model according to an embodiment of the present invention;

[0036] Figure 3 A schematic diagram of an accuracy prediction model provided by an embodiment of the present invention;

[0037] Figure 4 Schematic diagram of a curved surface microstructure targeted by an embodiment of the present invention;

[0038] Figure 5 This is a theoretical trajectory extraction diagram of an embodiment of the present invention;

[0039] Figure 6 This is a theoretical trajectory spectrum diagram of an embodiment of the present invention;

[0040] Figure 7 A schematic diagram of a low-pass filter used in an embodiment of the present invention;

[0041] Figure 8This is a schematic diagram of the fast and slow tool coordinated servo machining process according to an embodiment of the present invention;

[0042] Figure 9 Schematic diagram of a fast and slow knife collaborative servo simulation model according to an embodiment of the present invention;

[0043] Figure 10 This is the high-frequency trajectory and spectrum diagram after frequency decomposition according to an embodiment of the present invention;

[0044] Figure 11 This is the low-frequency trajectory and spectrum diagram after frequency decomposition according to an embodiment of the present invention;

[0045] Figure 12 Schematic diagram of the slow tool servo machining trajectory and following error according to an embodiment of the present invention;

[0046] Figure 13 Schematic diagram of machining trajectory and following error after deterministic compensation of following error according to an embodiment of the present invention;

[0047] Figure 14 Schematic diagram of machining trajectory and following error of the cutting method provided by an embodiment of the present invention

[0048] Figure 15 A comparison chart of the following errors of the cutting method, slow tool servo method, and error deterministic compensation method provided by an embodiment of the present invention;

[0049] Figure 16 A comparison chart of contour errors of the cutting method, slow tool servo method, and error deterministic compensation method provided by an embodiment of the present invention;

[0050] Figure 17 A schematic structural diagram of a cutting method experimental system provided in an embodiment of the present invention;

[0051] Figure 18 A comparison chart of the following error simulation and experimental results of the cutting method, slow tool servo method, and error deterministic compensation method provided in an embodiment of the present invention;

[0052] Figure 19 The experimental machining contour extraction and contour error calculation results of the cutting method, slow tool servo method, and error deterministic compensation method provided in the embodiments of the present invention are presented. DETAILED DESCRIPTION

[0053] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments.

[0054] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments in the present application without creative work are within the scope of protection of the present application.

[0055] It should be noted that the embodiments and features of the embodiments in this application may be combined with each other unless they conflict. Furthermore, in the following description, numerous specific details are set forth to provide a thorough understanding of the present invention. However, it will be apparent to one of ordinary skill in the art that these specific details are not necessarily required to practice the present invention. In other embodiments, well-known methods are not specifically described to avoid obscuring the present invention.

[0056] Example

[0057] Combine Figure 1 , this embodiment provides a microstructure ultra-precision cutting method, comprising the following steps:

[0058] S100 , constructing a contour error compensation model based on the overall transfer function of the tool servo system, wherein the tool servo system includes a fast tool servo system (FTS) and a slow tool servo system.

[0059] Combine Figure 2 Specifically, the overall transfer function of the tool cooperative servo system is expressed by Gall'(s), combined with Figure 3 , calculate the contour error EP after processing according to the accuracy prediction model. When constructing the contour error pre-compensation model, calculate the contour error after processing, the input trajectory of the machine tool Z axis after pre-compensation and the actual output position according to the accuracy prediction model. Specifically:

[0060] The contour error after processing E P For E P =Z in -Z out ;

[0061] Among them, Z in is the theoretical trajectory instruction, Z out is the actual output displacement, and the difference between the two is defined as the contour error E P .

[0062] The input trajectory after pre-compensation of the machine tool Z axis is Z in1 =Z in -E P ;

[0063] The actual output location is:

[0064]

[0065] Where G all '(s) is the overall transfer function of the tool servo system.

[0066] At the same time, the contour error after pre-compensation is E p1 (s)=Z in (s)-Z p1 (s)=E P (s)(1-G' all (s)), thus, the following error after pre-compensation can be reduced to (1-G' all (s)) times.

[0067] It should be noted that existing research has found that direct pre-compensation methods struggle to fully pre-compensate for sections of curve with significant curvature. Disturbance errors consisting of small noise and a few sharp peaks of significant curvature are also difficult to fully pre-compensate. To address these issues and further reduce following error, this embodiment proposes a multi-iteration pre-compensation scheme.

[0068] Specifically, the contour error after N compensations is E pN (s)=Z in (s)-Z pN (s)=E P (s)(1-G' all (s)) N .

[0069] If the frequency of the input signal is low enough, iterative precompensation can effectively reduce the following error. In order for the proposed iterative precompensation to be effective, the following prerequisites must be met:

[0070]

[0071] ||1-G' all (s)||<1

[0072] Among them, the target allowed maximum contour error ε is set. After multiple iterations, when the maximum contour error value max(E pN )<target error ε, the iterative pre-compensation value of the contour error pre-compensation model is Z cN (s)=-E P (s)-E P (s)(1-G' all (s))-......-E P (s)(1-G' all (s)) N-1 .

[0073] S200 , decomposing the machining trajectory obtained by the contour error pre-compensation model based on a frequency decomposition method to obtain a high-frequency small-amplitude trajectory and a low-frequency large-amplitude trajectory.

[0074] It can be understood that the tool trajectory preprocessing is mainly based on the surface decomposition method and the frequency decomposition method. The core of the surface decomposition method is to obtain the rotationally symmetric surface (or the minimum rotation surface) that is closest to the original surface. Its shortcomings are: first, the decomposition of complex surfaces is limited to seeking rotationally symmetric surfaces; second, based on the analytical calculation of geometry, the algorithm is relatively complex, and there are approximations in the numerical calculation, and the decomposed rotationally symmetric part is not strictly rotationally symmetric. At the same time, the surface decomposition method is generally only applicable to the decomposition of regular non-rotationally symmetric surfaces. The frequency decomposition method has a wider range of application, so this embodiment adopts the frequency decomposition method to achieve trajectory preprocessing.

[0075] It is known that the key to decomposing the tool trajectory of a curved microstructure is that the stroke and frequency response of each of the two decomposed trajectories are within the executable capabilities of the fast tool and the slow tool. For this reason, the existing technology uses stroke decomposition as a means to verify whether the frequency response requirements are met. However, the decomposition algorithm based on stroke is relatively complex and is an approximate calculation, while the decomposition based on frequency is relatively easy. Therefore, the method of verifying whether the stroke meets the requirements based on frequency decomposition in this embodiment is specifically as follows: along the tool trajectory extracted from the Archimedean spiral, a suitable cutoff frequency is selected, and the amplitude decomposition of high and low frequencies is achieved through a low-pass filter, thereby achieving decomposition of the curved microstructure tool processing trajectory without losing accuracy.

[0076] Combine Figure 4 The outer aspheric surface of the curved microstructure in this embodiment has a diameter of 1.5 mm, a height difference of 0.3 mm at the highest point, and a diameter of 20 μm for the small array sphere. in The theoretical trajectory obtained is as follows Figure 5 When the speed is 50r / min during processing, the spectrum of its theoretical trajectory is as follows. Figure 6 As shown in the figure, the theoretical trajectory spectrum shows that the processing trajectory frequency ranges from a few Hz to tens of Hz, which makes the processing difficult. Therefore, trajectory preprocessing is required.

[0077] In view of this, the transfer function G of the low-pass filter used in this embodiment after z-transformation is f (z) is:

[0078]

[0079] Where z is the z-transform operator, and the coefficients of the numerator and denominator are real numbers.

[0080] At the same time, the calculation model of the high-frequency small-amplitude trajectory is: Z FTS =Zin -Z STS ;

[0081] The calculation model of the low-frequency and large-amplitude trajectory is: STS =FFT -1 (G f (f)Z in (f));

[0082] Among them, FFT -1 is the inverse fast Fourier transform, Z in (f) is the fast Fourier transform result of the Z-axis trajectory, G f (z) is the transfer function of the low-pass filter after z-transformation.

[0083] It is understood that filters can be divided into finite impulse response (FIR) filters and infinite impulse response (IIR) filters. Because FIR filters can obtain linear phase characteristics and implement a non-recursive structure, they can maintain a small transition band and avoid instability. Therefore, this embodiment uses an FIR low-pass filter for trajectory decomposition, dividing the tool path into a low-frequency slow tool servo path and a high-frequency fast tool servo path.

[0084] The principle of low-pass filter is as follows Figure 7 As shown, ω1 represents the passband cutoff frequency, ω2 represents the cutoff frequency, and ω3 represents the stopband cutoff frequency. Typically, the effective processing bandwidth of an ultra-precision machine tool slow tool servo is around 10 Hz. Therefore, in this embodiment, the passband cutoff frequency is set to 15 Hz and the stopband cutoff frequency is set to 17 Hz. By substituting these frequency settings into the low-pass filter module in the simulation, the low-pass filter design can be implemented.

[0085] S300: Send the high-frequency small-amplitude trajectory to a fast tool servo system, and send the low-frequency large-amplitude trajectory to a slow tool servo system, so as to perform cutting processing.

[0086] Combine Figure 8 ,Specifically, it is necessary to determine whether the machining of the ,curved surface microstructure meets the execution capability of the ,fast tool servo system before cutting is performed;

[0087] If the overall stroke is less than the fast tool servo stroke, the execution capability of the fast tool servo system is further judged by the machining trajectory frequency. If the frequency meets the fast tool execution capability, fast tool servo machining is performed and contour error evaluation is carried out. If the frequency does not meet the requirement, the machining parameters are adjusted, the theoretical tool machining trajectory is re-extracted, and the above judgment process is repeated.

[0088] If the overall stroke is greater than the fast tool stroke, the trajectory is decomposed based on the frequency decomposition method. The decomposed trajectory is sent to the fast and slow tool servo systems respectively to verify whether the stroke meets the requirements;

[0089] If the travel is satisfied, compound processing is carried out through the tool servo system;

[0090] If the stroke does not meet the stroke requirements of each part of the tool servo system, the processing parameters should be modified.

[0091] Combine Figure 9 This embodiment builds upon the contour prediction model and deterministic error compensation of the tool servo system by incorporating quadratic trajectory planning and a low-pass filter-based frequency decomposition module. The decomposed trajectory is then implemented by the tool servo system. As a result, the fast tool servo in the simulation model not only enables machining of high-frequency, small-amplitude trajectories, but also dynamically compensates for servo following errors.

[0092] The surface microstructure machining trajectory targeted by this embodiment is brought into the simulation model to obtain high-frequency and low-frequency machining trajectories, such as Figure 10 and Figure 11 As shown in the figure, the high-frequency trajectory is approximately 10 Hz, and the trajectory is not a smooth spherical trajectory. Therefore, the small-amplitude trajectory obtained by subtraction does not correspond to a lens array, but the stroke frequency meets the execution capabilities of the fast tool servo system. Furthermore, the low-frequency trajectory after frequency decomposition is approximately in the middle of the designed surface shape, and its variation trend is consistent with the overall variation, making the decomposed high-frequency components symmetrical along the positive and negative values of the coordinate axis. Furthermore, this symmetrical motion trajectory better conforms to the motion laws of the piezoelectric ceramics in the fast tool servo, further enabling the fast tool servo to fully demonstrate its performance advantages.

[0093] Combine Figure 12 Because curved microstructures are more complex and have more frequency components than flat surfaces, the peak following error reaches ±10μm. Typically, the frequency response range of linear axes in ultra-precision machine tool slow-tool servo machining is around 10Hz. Trajectories exceeding this frequency range make it difficult to achieve high-precision machining while maintaining machining efficiency. However, during constant-speed machining, the outer diameter has a higher linear velocity and machining speed, resulting in more frequency components in the corresponding spectrum. Therefore, the following error gradually decreases as machining progresses from the outer diameter toward the center. Observing the trajectory diagram and the zoomed-in image of the trajectory from 10s to 10.2s reveals a significant deviation between the theoretical trajectory and the actual motion trajectory. This deviation manifests as overshoot oscillation compared to the theoretical trajectory, and is particularly sensitive at transitions along the smooth trajectory, resulting in higher following error. This is because the rapid changes in the machining trajectory cause a response lag in the machine tool servo system, resulting in a larger following error when machining curved microstructures with slow-tool servo machining.

[0094] Combine Figure 13The following error generated during slow-tool servo machining is compensated in real time. After tool servo system error compensation, the average following error amplitude is ±2μm. The enlarged trajectory diagram shows that compared to slow-tool servo machining, the overlap between the theoretical and actual trajectories is improved, and the following error is compensated. However, compared to existing studies on planar microstructure machining, the following error of curved microstructures produced by tool servo system error compensation is greater, and the error compensation effect is less than ideal. This is due to the increased complexity of the machined surface, the steepness of complex curved microstructures, and the increase in the frequency component of the motion trajectory, which increases the following error of slow-tool servo machining to ±10μm. If the machine tool machining speed is further increased, the following error will also increase further. The following error value generated during slow-tool servo machining will approach the maximum travel of fast-tool servo. Continuing to use the error compensation methods used in the previously studied tool servo system will result in an increase in the micro-stage travel. However, the greater the micro-stage travel, the greater the loss of its high-frequency response characteristics, which greatly limits the effectiveness of the tool servo system error compensation.

[0095] In order to verify the effectiveness of multiple iterations of pre-compensation in the collaborative servo processing technology proposed in this embodiment, the number of pre-compensation iterations in this contraction force is three. Therefore, its trajectory and following error are as follows: Figure 14 As shown in the figure. Among them, through multiple iterations of contour error pre-compensation and trajectory frequency decomposition pre-processing, the processing is completed based on the tool servo system. The trajectory magnification diagram shows that the actual trajectory has a higher degree of overlap with the theoretical trajectory, and the larger following error at the trajectory change is also compensated. Compared with the previous two methods, there is an overshoot phenomenon in the trajectory. In other words, the actual motion trajectory of the cutting method provided by this embodiment can better follow the changes in the theoretical trajectory, and the servo following error can be maintained within 0.5μm, which further shows that this method has higher processing accuracy and is more suitable for curved surface microstructure processing.

[0096] Combine Figure 15 The three colored lines in the figure represent the following errors of the three processing methods. The blue one is the slow tool servo method, the red one is the error deterministic compensation method, and the orange one is the tool servo collaborative cutting method provided in this embodiment. By intuitively comparing the following error values of the three methods, it can be seen that compared with the error deterministic compensation method, the following error generated in the tool servo collaborative cutting method proposed in this embodiment is significantly lower.

[0097] It should be noted that the maximum target contour error is selected as 1 μm according to the actual application requirements. The contour error can be obtained by comparing the workpiece morphology with the ideal morphology. The contours and errors after processing by the above three methods are as follows: Figure 16 As shown. The peak values of contour errors are selected for comparison. The maximum contour errors of the slow tool servo machining method, the error deterministic compensation method, and the fast and slow tool collaborative servo cutting method provided in this embodiment are 9.945μm, 2.549μm, and 0.799μm, respectively. Figure 16A comparison of contour errors between the medium-slow tool servo machining method and the deterministic error compensation method shows that, while tracking error compensation can effectively reduce contour errors in curved microstructures compared to slow tool servo machining, the restricted relationship between the fast tool servo stroke and frequency response in the tool servo cutting system prevents the contour error from achieving the machining accuracy of flat microstructures after error compensation. Comparing contour error simulation results shows that, compared to the other two methods, the fast-slow tool coordinated servo method offers a greater advantage in machining complex curved microstructures with large drop heights, ensuring efficient and high-precision machining of such workpieces, meeting the target contour error requirement of a maximum value of less than 1μm.

[0098] At the same time, by observing the contour error distribution obtained by the tool servo collaborative cutting method, it can be found that the contour error generated at the lens array is relatively large. The reason for this phenomenon is that the speed during the fast and slow tool collaborative servo processing is 50r / min. The calculation of the processing trajectory spectrum is related to the speed. When the speed increases, the horizontal axis frequency value of the spectrum increases, while the overall graph does not change. Therefore, the high-frequency component of the processing trajectory increases. The fast tool servo system bears more high-frequency component trajectories during processing, and the contour error generated by the fast tool servo at the lens array is more obvious. During the slow tool servo processing, the fast tool servo is added to compensate for the slow tool servo's tracking error. Therefore, the large-scale low-frequency processing contour error completed by the slow tool servo is smaller, which further highlights the contour error at the lens array.

[0099] To further demonstrate the technical effect of this embodiment, an experimental verification is performed, specifically:

[0100] Combine Figure 17 Based on the real-time following error compensation strategy, the data processing and calculation module was modified. Specifically, the experimental system was divided into four modules: a high-frequency trajectory execution module, a low-frequency trajectory execution module, a data processing and calculation module, and a data acquisition and feedback module. The data processing and calculation module incorporates trajectory preprocessing and decomposition, compared to the error compensation strategy principle. The data is then sent to the high-frequency and low-frequency trajectory execution modules of the fast and slow tool servo systems, respectively, to achieve collaborative tool servo machining.

[0101] When performing curved microstructure processing, the ultra-precision lathe controller calculates the following error through the feedback of the grating and the theoretical instructions to obtain the following error after slow-tool servo processing; the position signal of the fast-tool servo is fed back by the capacitive displacement sensor, and the theoretical and actual motion trajectory of the machine tool slow-tool servo system are combined to obtain the following error of the error deterministic compensation method and the cutting method provided in this embodiment.

[0102] In order to compare the accuracy of the theoretical model proposed in this chapter, the experimental results are compared with the simulation results, such as Figure 18As shown in Figure 3, the following errors obtained by simulation and experiment under the three methods are compared. The numerical values and variation patterns of the three methods are well consistent. This verifies that the tool servo collaborative machining method proposed in this embodiment can reduce the following error during the machining of curved microstructures.

[0103] Among them, the three-dimensional white light interferometer measurement results of the three methods and the calculated profile errors are as follows Figure 19 As shown. From this, it can be seen that the peak values of the microstructure contour errors processed by the slow tool servo method, the error deterministic compensation method, and the cutting method provided in this embodiment (tool servo collaborative processing method) are 10.343μm, 2.677μm, and 0.817μm, respectively. This further illustrates that for curved surface microstructures, the cutting method proposed in this embodiment has higher processing accuracy than the first two methods, and the resulting contour error peak value is the lowest.

[0104] In this implementation, the contour error simulation and experimental results are compared, as shown in Table 1. The experimental contour error results are generally larger than the simulation results. This is because the experimental machining process is subject to external interference such as random vibration, which greatly affects the actual machining conditions. Therefore, the experimental contour error values are larger than the simulation results. This shows that the overall error between the simulation and experimental results remains within 5%, further verifying the accuracy of the simulation results and analysis.

[0105] Processing methods Simulation results (μm) Experimental results (μm) error Slow knife servo method 9.925 10.343 4.04％ Error deterministic compensation method 2.549 2.677 4.78％ Tool Servo Collaboration Method 0.799 0.817 2.25％

[0106] Table 1

[0107] In summary, the microstructure ultra-precision cutting method provided in this embodiment first constructs a contour error compensation model based on the overall transfer function of the tool servo system including the fast tool servo system and the slow tool servo system, which can reduce the contour error. Then, the processing trajectory obtained by the contour error compensation model is decomposed based on the frequency decomposition method to obtain a high-frequency small-amplitude trajectory and a low-frequency large-amplitude trajectory. Finally, the high-frequency small-amplitude trajectory is sent to the fast tool servo system, and the low-frequency large-amplitude trajectory is sent to the slow tool servo system for cutting processing, so that ultra-precision turning processing can be achieved through the fast tool servo while meeting the stroke conditions to obtain higher-precision processed parts.

[0108] Furthermore, by analyzing the execution capabilities of the motion trajectories of each module of the tool servo system after trajectory decomposition, it was demonstrated that this embodiment can meet machining accuracy requirements while ensuring machining efficiency. Comparison of experimental results based on the slow tool servo machining method, the error deterministic compensation method, and the cutting method provided by this embodiment shows that, compared with the first two methods, this embodiment can achieve higher machining accuracy while meeting machining efficiency. Following error in this embodiment can be effectively suppressed, with contour error maintained within 0.817μm. Furthermore, the simulated and experimental following errors are highly consistent, and the contour accuracy simulation and experimental results are within 5%, demonstrating the accuracy of the simulation results and analysis of this embodiment.

[0109] In summary, the microstructure ultra-precision cutting method provided in this embodiment can ensure the processing efficiency of complex curved surface microstructures while meeting the processing accuracy requirements.

[0110] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A microstructure ultra-precision cutting method, characterized in that: The following steps are involved: Based on the overall transfer function of the tool servo system, a contour error compensation model is constructed, wherein the tool servo system includes a fast tool servo system and a slow tool servo system; Decomposing the machining trajectory obtained by the contour error pre-compensation model based on a frequency decomposition method to obtain a high-frequency small-amplitude trajectory and a low-frequency large-amplitude trajectory; The high-frequency and small-amplitude trajectory is sent to a fast tool servo system, and the low-frequency and large-amplitude trajectory is sent to a slow tool servo system for cutting processing.

2. The microstructure ultra-precision cutting method according to claim 1, characterized in that: When constructing the contour error pre-compensation model, the contour error after machining, the input trajectory of the machine tool Z axis after pre-compensation, and the actual output position are calculated according to the accuracy prediction model.

3. The microstructure ultra-precision cutting method according to claim 2, characterized in that: The contour error after processing E P For E P =Z in -Z out ; The input trajectory after pre-compensation of the machine tool Z axis is Z in1 =Z in -E P ; The actual output location is: Where G all '(s) is the overall transfer function of the tool servo system.

4. The microstructure ultra-precision cutting method according to claim 3, characterized in that: The contour error after pre-compensation is E p1 (s)=Z in (s)-Z p1 (s)=E P (s)(1-G' all (s)).

5. The microstructure ultra-precision cutting method according to claim 4, characterized in that: The contour error pre-compensation model is a multiple-iteration pre-compensation model.

6. The microstructure ultra-precision cutting method according to claim 5, characterized in that: The contour error after N times compensation is E pN (s)=Z in (s)-Z pN (s)=E P (s)(1-G' all (s)) N .

7. The microstructure ultra-precision cutting method according to claim 6, characterized in that: The iterative pre-compensation value of the contour error pre-compensation model is Z cN (s)=-E P (s)-E P (s)(1-G' all (s))-......-E P (s)(1-G' all (s)) N-1 .

8. The microstructure ultra-precision cutting method according to claim 1, characterized in that: The calculation model of the high-frequency small-amplitude trajectory is: FTS =Z in -Z STS ; The calculation model of the low-frequency and large-amplitude trajectory is: STS =FFT -1 (G f (f)Z in (f)); Among them, FFT -1 is the inverse fast Fourier transform, Z in (f) is the fast Fourier transform result of the Z-axis trajectory, G f (z) is the transfer function of the low-pass filter after z-transformation.

9. The microstructure ultra-precision cutting method according to claim 8, characterized in that: In the process of decomposing the machining trajectory obtained by the contour error pre-compensation model based on the frequency decomposition method, the passband cutoff frequency is 15 Hz and the stopband cutoff frequency is 17 Hz.

10. The microstructure ultra-precision cutting method according to claim 9, characterized in that: Before cutting, determine whether the processing of the curved surface microstructure meets the execution capability of the fast tool servo system; If the overall stroke is less than the fast tool servo stroke, the execution capability of the fast tool servo system is further judged by the machining trajectory frequency. If the frequency meets the fast tool execution capability, fast tool servo machining is performed and contour error evaluation is carried out. If the frequency does not meet the requirement, the machining parameters are adjusted, the theoretical tool machining trajectory is re-extracted, and the above judgment process is repeated. If the overall stroke is greater than the fast tool stroke, the trajectory is decomposed based on the frequency decomposition method. The decomposed trajectory is sent to the fast and slow tool servo systems respectively to verify whether the stroke meets the requirements; If the travel is satisfied, compound processing is carried out through the tool servo system; If the stroke does not meet the stroke requirements of each part of the tool servo system, the processing parameters should be modified.

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