Time-varying removal function controlled time grinding compensation processing method and system of optical element

Abstract

The application discloses a time-varying removal function controlled time grinding compensation processing method and system of an optical element, and the method comprises the following steps: obtaining a removal function of different processing parameter combinations; extracting a removal efficiency; measuring a surface shape error distribution of a to-be-processed surface; calculating a feed speed distribution matrix according to the removal function of a reference processing parameter combination and the surface shape error distribution of the to-be-processed surface with an additional removal layer; determining whether to reduce the thickness of the additional removal layer or select a reference processing parameter combination with a smaller removal efficiency according to the size relationship between the elements in the matrix and the upper limit of the feed speed, and then solving a speed threshold value according to the average combined speed of the reference processing parameter combination; for the elements greater than the speed threshold value in the feed speed distribution matrix, compensation replacement is performed, and the processing parameter combination of the corresponding position is updated; and the processed surface is processed by using the compensated feed speed distribution matrix and the processing parameter combination. The thickness of the additional removal layer is reduced, and the controlled time grinding processing efficiency is further improved.

Description

Technical Field

[0001] This invention relates to the field of optical element processing, and in particular to a time-varying removal function controlled grinding compensation processing method and system for optical elements. Background Technology

[0002] With advancements in optical component manufacturing capabilities, based on the Rayleigh criterion, larger aperture optical components offer greater resolution and are now widely used in various high-resolution observation systems. For example, the primary mirror of a reconnaissance satellite's optical system has an aperture on the order of 3 meters; the primary mirror of the James Webb Space Telescope (JWST) in the United States has an aperture of 6.5 meters; and the primary mirror of the E-ELT ground-based telescope, which the European Space Agency will complete by 2030, has an aperture of 39.8 meters. This places extremely high demands on the processing efficiency of optical components. In the 1980s, when manufacturing the Hubble Space Telescope's primary mirror, the optical manufacturing capability requirement was approximately 1 meter. 2 / year, while the expected processing efficiency for the E-ELT project exceeds 100m 2 / year. This places higher demands on the processing efficiency of optical components.

[0003] Existing large-aperture optical processing methods mainly consist of: milling and shaping—precision / ultra-precision grinding—grinding and polishing—deterministic reshaping. The first three processes converge the surface shape error of the optical element to sub-micron level, and the final high-precision deterministic reshaping completes the processing from sub-micron to final precision. Controlled-time grinding (CCOS) is based on the CCOS deterministic optical processing method, significantly improving material removal efficiency and effectively shortening the processing cycle of optical elements. The CCOS method is based on the Preston principle, using a removal function with a constant material removal rate per unit time. At high error points, the dwell time is long, resulting in more material removal; at low error points, the dwell time is short, resulting in less material removal. The surface shape error of the workpiece fluctuates, with a highest point P (Peak) and a lowest point V (Valley). Near the lowest error point, the amount of material to be removed is relatively small, and the calculated dwell time is often very short. Especially at the lowest error point, the theoretical removal rate is 0, which would lead to an infinitely high processing head speed at that position, which is clearly unrealistic. Even if the machining head passes through the point of lowest error at the machine tool's highest speed, some material will still be removed. Therefore, in actual shaping, an additional removal layer is added on top of the error distribution to be corrected, to compensate for the extra removal amount by the removal function at the point of lowest error. The additional removal layer is related to the surface error distribution and the efficiency of the removal function. When the surface error distribution is the same, the higher the removal efficiency of the removal function, the thicker the corresponding additional removal layer needs to be.

[0004] Existing CCOS optical deterministic machining methods, such as magnetorheological and small-head grinding methods, have low removal function efficiency, resulting in a small additional removal layer thickness. Time-controlled grinding methods have very high removal efficiency, reaching 10 to 50 times that of magnetorheological methods. Therefore, to achieve a high convergence ratio for surface shape errors, a larger additional removal layer thickness is required, reducing machining efficiency. Summary of the Invention

[0005] The technical problem to be solved by the present invention is as follows: In view of the above-mentioned problems of the prior art, a time-controlled grinding compensation method and system for time-varying removal function of optical elements is provided. The dwell time is calculated based on the time-varying removal efficiency with minimum additional removal layer thickness. At the low error point, it can operate in a low removal efficiency mode, reduce the thickness of the additional removal layer, and further improve the time-controlled grinding efficiency.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] A time-controlled grinding compensation method for time-varying removal functions of optical elements includes the following steps:

[0008] Obtain removal functions for different combinations of processing parameters;

[0009] Extraction efficiency of the removal function;

[0010] Measure the surface shape error distribution of the surface to be processed;

[0011] Select a reference machining parameter combination from different machining parameter combinations, and calculate the feed rate distribution matrix based on the removal function of the reference machining parameter combination and the surface shape error distribution of the surface to be machined with an additional removal layer.

[0012] Based on the relationship between the elements in the feed rate distribution matrix and the upper limit of the feed rate, determine whether to reduce the thickness of the additional removal layer or select a baseline machining parameter combination with a smaller removal efficiency. Then, solve the speed threshold based on the average combined speed of the baseline machining parameter combination. For elements in the feed rate distribution matrix that are greater than the speed threshold, compensate and replace them, and update the machining parameter combination at the corresponding position.

[0013] Machining is performed using a compensated feed rate distribution matrix and a combination of machining parameters for each position.

[0014] Furthermore, when calculating the feed rate distribution matrix based on the removal function of the baseline machining parameter combination and the surface shape error distribution of the surface to be machined with the added removal layer, the following is included:

[0015] An additional removal layer thickness is added to the surface to be processed, and then the removal function RF corresponding to the baseline processing parameter combination is used. sThe surface shape error distribution of the surface to be processed is calculated by the dwell time solution algorithm to obtain the dwell time distribution matrix T(x,y) of the workpiece surface;

[0016] Dividing the discrete interval Δd of the surface shape by the dwell time distribution matrix T(x,y) yields the feed rate distribution matrix FS(x,y).

[0017] Furthermore, when determining whether to reduce the thickness of the additional removal layer or select a baseline machining parameter combination with lower removal efficiency based on the relationship between the elements in the feed rate distribution matrix and the upper limit of the feed rate, the following steps are taken:

[0018] If all the element values ​​in the feed rate distribution matrix FS(x,y) are less than the upper limit of the feed rate FS... max The process involves reducing the thickness of the additional removal layer, and then performing the steps of calculating the feed rate distribution matrix based on the removal function of the reference machining parameter combination and the surface error distribution of the surface to be machined with the added additional removal layer.

[0019] If the element values ​​in the feed rate distribution matrix FS(x,y) are greater than the feed rate upper limit FS max If the proportion of elements is greater than the proportion threshold, the step of selecting a benchmark processing parameter combination from different processing parameter combinations is performed, including: selecting a new benchmark processing parameter combination in descending order of removal efficiency, and the removal efficiency of the new benchmark processing parameter combination is less than the removal efficiency of the current benchmark processing parameter combination.

[0020] If the element values ​​in the feed rate distribution matrix FS(x,y) are greater than the feed rate upper limit FS max If the element ratio is less than or equal to the ratio threshold, perform the step of solving the speed threshold based on the average combined speed of the baseline processing parameter combination.

[0021] Furthermore, after obtaining the removal function with different combinations of processing parameters, the process also includes: extracting the surface roughness of the removal function;

[0022] When selecting a new benchmark processing parameter combination in descending order of removal efficiency, the following applies: if there are two or more processing parameter combinations with the same removal efficiency, the processing parameter combination is selected as the new benchmark processing parameter combination in ascending order of surface roughness.

[0023] Furthermore, when solving for the speed threshold based on the average resultant speed of the reference machining parameter combination, the following steps are included:

[0024] The average feed rate FS is obtained by averaging the values ​​of all elements in the feed rate distribution matrix FS(x,y). a ;

[0025] Obtain the vibration frequency f in the reference machining parameter combination sThe corresponding linear velocity of vibration v fs Calculate the average feed rate FS a Vibration linear velocity v fs The belt update linear speed v in the combination of reference machining parameters s The average resultant velocity v is obtained by vector summation. a ;

[0026] The average resultant velocity v a Multiply by a preset upper limit coefficient, based on the vibration linear velocity v fs , sanding belt replacement linear speed v s The new average feed rate is obtained by solving the new average resultant velocity and used as the velocity threshold.

[0027] Furthermore, after selecting a benchmark processing parameter combination from different processing parameter combinations, the process also includes: calculating the coefficient between the removal efficiency corresponding to the benchmark processing parameter combination and other processing parameter combinations;

[0028] When compensating and replacing elements in the feed rate distribution matrix that are greater than the rate threshold, and simultaneously updating the machining parameter combination at the corresponding position, the following steps are taken: selecting target coefficients such that point (x i ,y i The feed rate FS(x) at position ) i ,y i If the product of the target coefficient and the target coefficient is less than or equal to the speed threshold, the combination of processing parameters corresponding to the target coefficient is selected as the point (x). i ,y i The new combination of machining parameters at position ) will increase the feed rate FS(x) i ,y i The product of (x) and the target coefficient is used as the point (x). i ,y i The new feed rate at the location.

[0029] Furthermore, the combination of processing parameters corresponding to the target coefficient is selected as the point (x). i ,y i When a new combination of processing parameters is used at a given location, the following applies: if there are two or more combinations of processing parameters with the same target coefficient, the processing parameter combinations are selected in order of increasing surface roughness.

[0030] Furthermore, when selecting the target coefficient, the following steps are included: dividing the velocity threshold by the feed rate FS(x) i ,y i Obtain the reference value of the coefficient, and select the coefficient whose value is the same as the reference value as the target coefficient.

[0031] Furthermore, when selecting the target coefficient, this includes: setting the feed rate FS(x) as the target coefficient. i ,y iDivide the reference value by the speed threshold, match the reference value with the preset interval distribution, and select the preset coefficient corresponding to the interval to which the reference value belongs as the target coefficient based on the matching result.

[0032] The present invention also proposes a time-varying removal function controlled-time grinding compensation machining system for optical elements, including a computer device, the computer device being programmed or configured to perform any of the time-varying removal function controlled-time grinding compensation machining methods for optical elements.

[0033] Compared with the prior art, the present invention has the following advantages:

[0034] This invention first selects a baseline machining parameter combination from different machining parameter combinations. Based on the removal function of the baseline machining parameter combination and the surface shape error distribution of the surface to be machined with an additional removal layer, a feed rate distribution matrix is ​​calculated. Then, based on the relationship between the elements in the feed rate distribution matrix and the upper limit of the feed rate, it is determined whether to reduce the thickness of the additional removal layer or select a new baseline machining parameter combination. Finally, a speed threshold is calculated based on the average resultant speed of the baseline machining parameter combination. Elements in the feed rate distribution matrix that are greater than the speed threshold are compensated and replaced, and the machining parameter combination at the corresponding positions is updated. The final result is a compensated feed rate distribution matrix. This reduces the thickness of the additional removal layer while simultaneously compensating for the dwell time at all positions on the surface to be machined, achieving a stable removal function.

[0035] When selecting a new combination of reference machining parameters, this invention selects a new combination of reference machining parameters in order of increasing surface roughness of the removal function for multiple combinations of machining parameters with the same removal function efficiency, in order to ensure the best machining effect.

[0036] When compensating and replacing elements in the feed rate distribution matrix that are greater than the speed threshold, this invention uses an interval compensation method to replace multiple elements belonging to a preset interval with feed rates under the same combination of machining parameters. This can effectively reduce the number of compensation adjustments and has little impact on machining accuracy. Attached Figure Description

[0037] Figure 1 This is a flowchart of Embodiment 1 of the present invention.

[0038] Figure 2 This is a schematic diagram illustrating the efficiency of the removal function obtained by different combinations of processing parameters in Embodiment 1 of the present invention.

[0039] Figure 3 This is the feed rate distribution matrix calculated after dwell time in Embodiment 1 of the present invention.

[0040] Figure 4 This is a schematic diagram of the speed components related to time-controlled grinding of optical elements in Embodiment 1 of the present invention.

[0041] Figure 5 This is the feed rate distribution matrix divided using the interval compensation strategy in Embodiment 1 of the present invention.

[0042] Figure 6 This is the final feed rate distribution matrix after the interval compensation strategy in Embodiment 1 of the present invention. Detailed Implementation

[0043] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention.

[0044] Example 1

[0045] In the processing of optical components, in order to operate in a low-removal-efficiency mode at low error points, reduce the thickness of the additional removal layer, and further improve the time-controlled grinding efficiency, this embodiment proposes a time-controlled grinding compensation method for optical components based on a time-varying removal function. The dwell time is calculated based on the time-varying removal efficiency at the minimum additional removal layer thickness. Figure 1 As shown, it includes the following steps:

[0046] S1) Obtain the removal function for different combinations of processing parameters;

[0047] S2) Extract the removal efficiency of the removal function and extract the surface roughness of the removal function;

[0048] S3) Select a benchmark processing parameter combination from different processing parameter combinations, and establish the equivalent relationship between the removal function efficiency and time for different processing parameter combinations by calculating the coefficient relationship between the benchmark processing parameter combination and other processing parameter combinations.

[0049] S4) Measure the surface shape error distribution of the surface to be processed;

[0050] S5) Calculate the feed rate distribution matrix based on the removal function of the reference machining parameter combination and the surface shape error distribution of the surface to be machined with the added removal layer;

[0051] S6) Determine whether to reduce the thickness of the additional removal layer or select a reference machining parameter combination with a smaller removal efficiency based on the relationship between the elements in the feed speed distribution matrix and the upper limit of the feed speed. Then, solve the speed threshold based on the average combined speed of the reference machining parameter combination. For elements in the feed speed distribution matrix that are greater than the speed threshold, compensate and replace them, and update the machining parameter combination at the corresponding position.

[0052] S7) Machining is performed using the compensated feed rate distribution matrix and the combination of machining parameters for each position.

[0053] Through the above steps, this embodiment first selects a reference machining parameter combination, and calculates the feed rate distribution matrix based on the reference machining parameter combination and the surface shape error distribution of the surface to be machined. Then, based on the relationship between the feed rate distribution matrix and the upper limit of the feed rate, it determines whether to reduce the thickness of the additional removal layer or select a reference machining parameter combination with a smaller removal efficiency. Furthermore, it compensates and replaces elements in the feed rate distribution matrix that are greater than the speed threshold. While reducing the thickness of the additional removal layer, it completes the dwell time compensation at all positions on the surface to be machined, achieving the effect of stabilizing the removal function.

[0054] The specific implementation process for each step is explained below.

[0055] In step S1 of this embodiment, obtaining the removal function for different combinations of processing parameters specifically refers to obtaining the removal function RF of the processing head under different parameter combinations by changing the vibration frequency f and the belt update speed v of the time-controlled grinding head.

[0056] In this embodiment, the vibration frequency f and the abrasive belt renewal speed v are independent and controllable processing variables, both of which are major factors affecting material removal efficiency. Therefore, by using the vibration frequency and abrasive belt renewal speed as two variables and changing their values ​​separately, different processing parameter combinations can be obtained. Multiple processing parameter combinations can be combined to process (f1~f...). n v1~v n ),like Figure 2 As shown, multiple removal functions can be obtained, each corresponding to a combination of processing parameters. Obtaining the removal function by combining the processing parameters is a common method used by those skilled in the art, and its specific calculation process will not be elaborated here.

[0057] In step S2 of this embodiment, the removal efficiency specifically refers to the material removal efficiency E. vf Surface roughness specifically refers to the surface roughness Ra after machining. vf Step S2 specifically includes the following steps:

[0058] 2.1) Extract the three-dimensional profile of the corresponding removal function using an interferometer or profilometer, and calculate the material removal efficiency E of the removal function processed by different parameter combinations using process software. vf ;

[0059] 2.2) Using a contact roughness meter or white light interferometer, the surface roughness Ra corresponding to the removal function region is obtained by averaging multiple points. vf ;

[0060] Using relevant instruments to extract the removal efficiency and surface roughness of the removal function is a common method used by those skilled in the art, and its specific implementation steps and calculation derivation process will not be elaborated here.

[0061] Step S3 in this embodiment specifically includes the following steps:

[0062] 3.1) Establish a removal function library, which includes removal functions, removal efficiencies, and corresponding processing parameter combinations obtained through steps S1 and S2. Select the removal efficiency corresponding to one processing parameter combination as the benchmark, denoted as E. s This combination of processing parameters is the baseline processing parameter combination, and the corresponding removal function is RF. s The vibration frequency and belt refresh rate used in the reference machining parameter combination are denoted as f. s and v s ;

[0063] In this embodiment, the baseline removal efficiency and the corresponding baseline processing parameter combination are selected in descending order of removal efficiency to ensure a better processing effect.

[0064] 3.2) Using removal efficiency as a comparison index, calculate the removal efficiency E for each other combination of processing parameters. vf With E s The coefficient relationships between them are as follows:

[0065] E vf =k*E s (1)

[0066] Where k is the inherent proportionality coefficient under different combinations of processing parameters. For example, let E s The value is 1, in another set of processing parameters (v n f n If the material removal efficiency is 0.5 under the given conditions, then k is 0.5, meaning that when using the processing parameter combination (v... n f n In the case of the removal function, the time required to remove the same material is twice that of the removal function using the baseline processing parameter combination.

[0067] In step S4 of this embodiment, measuring the surface shape error distribution of the surface to be processed specifically refers to measuring the error distribution of the workpiece surface using equipment such as an interferometer, a coordinate measuring machine, or a profilometer. Measuring the error distribution of the workpiece surface using relevant instruments is a common method used by those skilled in the art, and its specific implementation steps and calculation derivation process will not be elaborated here.

[0068] In step S5 of this embodiment, when calculating the feed rate distribution matrix based on the removal function of the reference machining parameter combination and the surface shape error distribution of the surface to be machined with the added removal layer, the following steps are included:

[0069] 5.1) Add an additional removal layer thickness to the surface to be processed, and then use the removal function RF corresponding to the baseline processing parameter combination. s The surface shape error distribution of the surface to be processed is calculated by the dwell time solution algorithm to obtain the current dwell time distribution matrix T(x,y) of the workpiece surface. The dwell time solution algorithm is a commonly used method in the art, and its specific calculation process will not be described in detail here.

[0070] In this embodiment, in order to prevent the dwell time calculation from reaching a point of infinite speed, a very thin additional removal layer must be added on the basis of the workpiece surface error. The initial thickness of the additional removal layer is L, thereby completing the dwell time calculation for this round.

[0071] 5.2) After obtaining the dwell time distribution for this round, divide the surface discrete interval Δd by the dwell time distribution matrix T(x,y) to obtain the feed rate distribution matrix FS(x,y). The calculation formula is as follows:

[0072]

[0073] Where Δd is the discrete interval of the surface shape and T(x,y) is the dwell time matrix, it can be seen that the dwell time is inversely proportional to the feed rate.

[0074] Step S6 in this embodiment specifically includes the following steps:

[0075] 6.1) Based on the machine tool's hardware structure, such as the rated angular acceleration of the linear axis motor, the lead of the ball screw, and the mass of the moving slide, calculate the upper limit of the feed rate FS for normal operation of the machine tool. max The upper limit of the feed rate for normal operation of a computer tool is a method commonly used by those skilled in the art, and the specific calculation process will not be described in detail here;

[0076] 6.2) Based on the feed rate distribution matrix FS(x,y) obtained in step 5.2), analyze the data and determine whether to reduce the thickness of the additional removal layer or select a baseline machining parameter combination with lower removal efficiency based on the relationship between the elements in the feed rate distribution matrix and the upper limit of the feed rate. This includes:

[0077] If all the element values ​​in the feed rate distribution matrix FS(x,y) are less than the upper limit of the feed rate FS... max If the thickness of the additional removal layer is reduced, in this embodiment, the thickness of the additional removal layer can be reduced by the step size method, that is, the current thickness of the additional removal layer is subtracted by a fixed step size to obtain the reduced thickness of the additional removal layer. In addition, other methods can be used, which are not limited here; then return to step 5.1) to execute the step of calculating the feed rate distribution matrix based on the removal function of the reference machining parameter combination and the surface shape error distribution of the surface to be machined with the additional removal layer added;

[0078] If the element values ​​in the feed rate distribution matrix FS(x,y) are greater than the feed rate upper limit FS max If the proportion of elements is greater than the proportion threshold, return to step S3 to execute the step of selecting a benchmark processing parameter combination from different processing parameter combinations. That is, select a new benchmark processing parameter combination in descending order of removal efficiency, and the removal efficiency of the new benchmark processing parameter combination is less than the removal efficiency of the current benchmark processing parameter combination. That is, repeat step S3 and its subsequent steps with the new benchmark processing parameter combination until the requirements are met.

[0079] If the element values ​​in the feed rate distribution matrix FS(x,y) are greater than the feed rate upper limit FS max If the element ratio is less than or equal to the ratio threshold, proceed with the subsequent step of solving the speed threshold based on the average combined speed of the reference processing parameters.

[0080] In this embodiment, the proportional threshold is 50%, and the upper limit of the feed rate is FS. max For 2000, such as Figure 3 As shown in the figure, the gray elements represent elements in the feed rate distribution matrix FS(x,y) whose values ​​are greater than the upper limit of the feed rate FS. max The elements, but since they do not exceed 50% of the total elements, can be used for subsequent steps on this data;

[0081] In this embodiment, considering that there may be multiple different processing parameter combinations with the same removal efficiency, when selecting a new benchmark processing parameter combination in descending order of removal efficiency, the following steps are taken: if there are two or more processing parameter combinations with the same removal efficiency, the processing parameter combination is selected as the new benchmark processing parameter combination in ascending order of surface roughness.

[0082] In this embodiment, step S6, which involves calculating the speed threshold based on the average combined speed of the reference machining parameter combination, includes the following steps:

[0083] 6.3) Average the values ​​of all elements in the feed rate distribution matrix FS(x,y) to obtain the average feed rate FS. a ;

[0084] 6.4) Obtain the vibration frequency f in the reference machining parameter combination. s The corresponding linear velocity of vibration v fs Calculate the average feed rate FS a Vibration linear velocity v fs The belt update linear speed v in the combination of reference machining parameters s The average resultant velocity v is obtained by vector summation. a ;

[0085] like Figure 4As shown, during time-controlled grinding, the belt renewal speed direction is the same as the feed direction and perpendicular to the vibration direction. Therefore, the average resultant speed v based on the combination of reference machining parameters is... a The calculation expression is as follows:

[0086]

[0087] Among them, v fs Let f be the linear velocity of vibration at the reference vibration frequency, and f be the linear velocity of vibration at the reference vibration frequency. s There is a one-to-one mapping relationship; FS a v represents the average feed rate in step 6.3). s The linear speed of the sand belt update in the baseline machining parameter combination;

[0088] 6.5) The average resultant velocity v a Multiply by a preset upper limit coefficient, based on the vibration linear velocity v fs , sanding belt replacement linear speed v s The new average feed rate is obtained by solving for the new average resultant velocity and used as the velocity threshold.

[0089] In this embodiment, the removal efficiency of the removal function is affected by the actual grinding line speed. To ensure the stability of the removal function (generally within 5%), the upper limit of the actual line speed should not exceed 105% of the average grinding speed. This is because when the timed grinding device passes through the low point of the workpiece error at a relatively high feed rate, although it ensures the accuracy of the dwell time, the high feed rate makes the local efficiency of the removal function higher, resulting in the actual removal amount being higher than expected, which affects error convergence.

[0090] Therefore, in this embodiment, the upper limit coefficient is 1.05, keeping v f and v s Without changing, based on equation (3), change the left-hand side v a Change to 1.05*v a Solve the new FS a FS as the velocity threshold u This serves as the upper limit of the threshold for determining the subsequent feed rate;

[0091] In step S6 of this embodiment, when compensating and replacing elements in the feed rate distribution matrix that are greater than the rate threshold, and simultaneously updating the machining parameter combination at the corresponding position, the following steps are included:

[0092] 6.6) Process each element in the feed velocity distribution matrix FS(x,y) one by one, and process the elements above the velocity threshold FS. u The elements are compensated and replaced;

[0093] In this embodiment, let a certain point (x) be... i ,yi The initial solution feed rate at position ) is FS(x) i ,y i ), and combine it with FS u Compare, if FS(x) i ,y i )≤FS u If the current feed rate is maintained, proceed to the next point; if FS(x i ,y i )>FS u Then, the processing parameters of the local removal function are adjusted. Based on step 3.2), FS(x) i ,y i The original combination of processing parameters used at (f) was (f) s ,v s At this point, a new combination of processing parameters can be selected from the removal function library (v). n f n Based on equation (1), a new feed rate can be obtained:

[0094] FS n (x i ,y i )=kFS(x i ,y i (4)

[0095] FS n (x i ,y i ) for using processing parameter combinations (v n f n The generated point (x) i ,y i The feed rate at position (x) is defined in the same way as in equation (1). For example, at (x) i ,y i The initial feed rate FS(x) is calculated using a removal function based on a combination of baseline machining parameters. i ,y i The speed is 30 mm / s, at which point the machining parameter combination (v) is used. n f n The removal function is given by k = 0.5 (i.e., the removal efficiency is 50% of the baseline removal efficiency), at which point FS... n (x i ,y i The value is 30 * 50% = 15 mm / s, therefore (x i ,y i The feed rate at position ) is compensated to 15 mm / s.

[0096] Therefore, step 6.6) of this embodiment specifically includes: if point (x)i ,y i The feed rate FS(x) at position ) i ,y i If the speed is greater than the speed threshold, select a target coefficient such that point (x) i ,y i The feed rate FS(x) at position ) i ,y i If the product of the target coefficient and the target coefficient is less than or equal to the speed threshold, the combination of processing parameters corresponding to the target coefficient is selected as the point (x). i ,y i The new combination of machining parameters at position ) will increase the feed rate FS(x) i ,y i The product of (x) and the target coefficient is used as the point (x). i ,y i The new feed rate at the location.

[0097] Similarly, considering the possibility that multiple different combinations of processing parameters may have the same coefficient, in this embodiment, the processing parameter combination corresponding to the target coefficient is selected as point (x). i ,y i When selecting a new combination of machining parameters at point (x), the following applies: If there are two or more combinations of machining parameters with the same target coefficient, the combination of machining parameters is selected in ascending order of surface roughness. For example, if machining parameter combinations (v1, f2) and (v2, f1) have the same k value, but the surface roughness of the removal function under parameters (v1, f2) is better than that under (v2, f1), then the parameter combination (v1, f2) is selected first as the point (x). i ,y i A new combination of processing parameters at the location.

[0098] In this embodiment, selecting the target coefficient includes: dividing the velocity threshold by the feed rate FS(x) i ,y i Obtain the reference value of the coefficient, and select the coefficient whose value is the same as the reference value as the target coefficient.

[0099] In practice, the time a machine tool spends at each position on the workpiece is relatively short, generally less than 1 second, with some individual points having a dwell time of up to 10 seconds. -2 The value is on the order of s. If the most suitable compensation parameter is selected for each point, the parameter adjustment for the next dwell time will begin before the vibration frequency and update speed have been fully adjusted, affecting the accurate control of the removal function efficiency.

[0100] In this case, based on this step, using an interval compensation strategy can effectively reduce the number of compensation adjustments and has minimal impact on machining accuracy. The main strategy is as follows: when FS...u ≤FS(x i ,y i ) < 1.1*FS u When using the substitution parameter combination (v) n f n The newly generated feed rate FS n (x i ,y i ); when 1.1*FS u ≤FS(x i ,y i ) < 1.2*FS u When using the substitution parameter combination (v) j f j The newly generated feed rate FS j (x i ,y i ); when 1.2*FS u ≤FS(x i ,y i ) < 1.3*FS u When using the substitution parameter combination (v) k f k The newly generated feed rate FS k (x i ,y i ...and so on, such as Figure 5 As shown. Correspondingly, when selecting the target coefficient, it includes: the feed rate FS(x) i ,y i Divide the reference value by the speed threshold, match the reference value with the preset interval distribution, and select the preset coefficient corresponding to the interval to which the reference value belongs as the target coefficient based on the matching result.

[0101] In this embodiment, after compensation and replacement according to the interval compensation strategy, the feed rate distribution matrix is ​​as follows: Figure 6 As shown, after compensation, no element has a value greater than 2000, achieving the effect of stabilizing the removal function.

[0102] Example 2

[0103] This embodiment proposes a time-varying removal function controlled-time grinding compensation machining system for optical elements based on Embodiment 1, including a computer device, which is programmed or configured to execute the time-varying removal function controlled-time grinding compensation machining method for optical elements described in Embodiment 1.

[0104] This embodiment also proposes a computer-readable storage medium storing a computer program programmed or configured to perform the time-varying removal function controlled-time grinding compensation machining method for optical elements described in Embodiment 1.

[0105] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Therefore, any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention should fall within the protection scope of the present invention.

Claims

1. A method for compensating a time-varying removal function controlled time grinding of an optical element, characterized in that, The method comprises the following steps: Obtaining removal functions of different machining parameter combinations; Extracting removal efficiency of the removal functions; Measuring surface profile error distribution of the surface to be machined; Selecting a reference machining parameter combination from the different machining parameter combinations, and calculating a feed speed distribution matrix according to the removal function of the reference machining parameter combination and the surface profile error distribution of the surface to be machined with an additional removal layer added; Determining whether to reduce the thickness of the additional removal layer or select a reference machining parameter combination with smaller removal efficiency according to the size relationship between the elements in the feed speed distribution matrix and the upper limit of the feed speed, and then solving a speed threshold according to the average resultant speed of the reference machining parameter combination, replacing the elements greater than the speed threshold in the feed speed distribution matrix with compensation, and updating the machining parameter combination at the corresponding position; Machining using the compensated feed speed distribution matrix and the machining parameter combination at each position.

2. The time-varying removal function controlled grinding compensation machining method of optical elements according to claim 1, characterized in that, When calculating the feed speed distribution matrix according to the removal function of the reference machining parameter combination and the surface profile error distribution of the surface to be machined with an additional removal layer added, the method comprises the following steps: Adding extra removal layer thickness to the surface to be processed, then using the reference processing parameter combination to correspond to the removal function RF s The surface shape error distribution of the surface to be processed is calculated to obtain the residence time distribution matrix of the workpiece surface through the residence time solving algorithm T (x, y); face shape discrete intervals divide by residence time distribution matrix T (x,y) to get feed velocity distribution matrix FS (x,y).

3. The time-varying removal function controlled grinding compensation machining method of optical elements according to claim 2, characterized in that, When determining whether to reduce the thickness of the additional removal layer or select a reference machining parameter combination with smaller removal efficiency according to the size relationship between the elements in the feed speed distribution matrix and the upper limit of the feed speed, the method comprises the following steps: if the feed rate distribution matrix FS the element value of the element in (x, y) is less than the upper limit of the feed rate FS max , the thickness of the additional removal layer is reduced, and then the step of calculating the feed rate distribution matrix according to the surface shape error distribution of the machined surface by performing the removal function according to the reference machining parameter combination and adding the additional removal layer is executed; if the element value in the feed speed distribution matrix FS is greater than the upper limit of the feed speed FS max If the proportion of the element is greater than the proportion threshold value, the step of selecting the reference machining parameter combination from different machining parameter combinations is performed, including: selecting a new reference machining parameter combination in descending order of removal efficiency, and the removal efficiency of the new reference machining parameter combination is less than the removal efficiency of the current reference machining parameter combination. If the feed rate distribution matrix FS The element values ​​in (x,y) are greater than the upper limit of the feed rate. FS max If the element ratio is less than or equal to the ratio threshold, perform the step of solving the speed threshold based on the average combined speed of the baseline processing parameter combination.

4. The time-varying removal function controlled grinding compensation machining method of optical elements according to claim 3, characterized in that, After obtaining the removal functions of the different machining parameter combinations, the method further comprises extracting surface roughness of the removal functions. When selecting a new reference machining parameter combination in descending order of removal efficiency, the method comprises the following steps: if there are more than two machining parameter combinations with the same removal efficiency, selecting the machining parameter combination in ascending order of surface roughness.

5. The time-varying removal function controlled grinding compensation machining method of optical elements of claim 2, wherein, When solving the speed threshold according to the average resultant speed of the reference machining parameter combination, the method comprises the following steps: The feed speed distribution matrix is calculated as follows: FS The average feed speed is calculated by averaging the element values of all elements in the matrix (x,y) FS a ; Obtaining a vibration frequency in a reference machining parameter combination f s A corresponding linear vibration velocity v fs , calculating an average feed velocity FS a , a linear vibration velocity v fs and a belt update linear velocity in the reference machining parameter combination v s The average resultant velocity is calculated as a vector sum of v a ; The average resultant velocity v a is multiplied by a preset upper limit coefficient, and a new average resultant velocity is solved according to the vibration linear velocity v fs , the belt sand renewal linear velocity v s and the new average resultant velocity to obtain a new average feed velocity as the speed threshold.

6. The time-varying removal function controlled grinding compensation machining method of optical elements of claim 2, wherein, After selecting the reference machining parameter combination from the different machining parameter combinations, the method further comprises calculating the coefficients between the removal efficiency corresponding to the reference machining parameter combination and the removal efficiency corresponding to other machining parameter combinations. When compensating and replacing elements in the feed rate distribution matrix that are greater than the rate threshold, and simultaneously updating the machining parameter combination at the corresponding position, the following steps are taken: selecting target coefficients such that point (x i ,y i feed rate at position FS (x i ,y i If the product of the target coefficient and the target coefficient is less than or equal to the speed threshold, the combination of processing parameters corresponding to the target coefficient is selected as the point (x). i ,y i The new combination of machining parameters at the location will affect the feed rate. FS (x i ,y i The product of (x) and the target coefficient is used as the point (x). i ,y i The new feed rate at the location.

7. The time-varying removal function controlled grinding compensation machining method of optical elements according to claim 6, characterized in that, Select the target coefficient corresponding to the processing parameter combination as the point (x i ,y i ) position of the new processing parameter combination, including: if there are two or more target coefficient same processing parameter combinations, select the processing parameter combination in the order of surface roughness from small to large.

8. The time-varying removal function controlled grinding compensation machining method of optical elements of claim 6, wherein, When selecting the target coefficient, including: dividing the speed threshold value by the feed speed FS (x i ,y i ) to obtain a coefficient reference value, and selecting a coefficient having the same coefficient value as the coefficient reference value as the target coefficient.

9. The time-varying removal function controlled grinding compensation machining method of optical elements of claim 6, wherein, When selecting target coefficients, this includes: the feed rate FS (x i ,y i Divide the reference value by the speed threshold, match the reference value with the preset interval distribution, and select the preset coefficient corresponding to the interval to which the reference value belongs as the target coefficient based on the matching result.

10. A time-varying removal function controlled on-process grinding compensation machining system of an optical element, comprising a computer device, characterized in that, The computer device is programmed or configured to perform the time-varying removal function controlled time-grinding compensation machining method of the optical element according to any one of claims 1-9.

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