Spacecraft thin-walled cabin lightening groove on-line measurement and compensation processing method

Abstract

The application provides a spacecraft thin-wall cabin lightening groove online measurement and compensation processing method, comprising the following steps: installing a thickness measuring head; setting a measurement point on the surface of each to-be-processed lightening groove and obtaining a theoretical thickness and an outer contour position; measuring the actual thickness of each measurement point and obtaining an actual outer contour position; calculating a compensation value of each measurement point according to the theoretical value and the measured value of the thickness and the outer contour; judging whether the compensation requirement is met according to the compensation value, if yes, processing after compensating the tool length based on the comprehensive compensation value, if not, reconstructing the processing surface based on the actual thickness and the outer contour position, and processing by using the initial tool length based on the reconstructed processing surface. The application calculates the compensation value according to the contour and thickness data, and finally processes by calling the compensation value, thereby improving the automation degree of measurement and processing, realizing efficient and high-precision processing of the spacecraft thin-wall cabin lightening groove and ensuring the thickness size precision.

Description

Technical Field

[0001] This invention belongs to the field of spacecraft manufacturing and CNC machining technology, and specifically relates to an online measurement and compensation machining method for thin-walled cabin weight reduction grooves in spacecraft. Background Technology

[0002] Both the new-generation manned spacecraft's sealed cabin structure and the lunar lander's sealed cabin structure are sealed welded cabins, constructed from welded ring segments, with an overall height of 2-3.5 meters and a diameter of approximately 3 meters. Their complex shapes feature hundreds of weight-reducing grooves and thin walls, with the thinnest part reaching 1.2±0.2 mm. To meet the design requirements of lightweighting, sealing performance, and strength, the wall thickness must be precisely controlled during the machining of the weight-reducing grooves. Because the structure is prone to deformation, uneven thickness processing leads to difficulties in controlling dimensional accuracy and making machining challenging. Typically, to control the structural thickness, trial cutting is performed before executing the theoretical machining program, leaving a margin for error. The thickness of the weight-reducing grooves is then manually measured to obtain the difference between the measured and theoretical thickness values. Finally, the machining program is adjusted based on this difference. The entire process requires manual measurement of thickness information at numerous points, recording, calculating, and inputting a large amount of data. It also necessitates executing the processing program more than twice. The measurement results are highly dependent on human factors, resulting in low compensation accuracy. Repeated measurements and corrections are necessary, leading to long processing cycles, low efficiency, high labor costs and requirements, and significant processing risks. Another approach involves compensating for structural thickness by superimposing contour scanning and thickness measurements. However, this method is time-consuming, has poor scanning accuracy for large structures, and requires significant time and efficiency when importing large datasets into programming software. Summary of the Invention

[0003] The technical problem solved by this invention is to overcome the shortcomings of the prior art and provide an online measurement and compensation processing method for the thin-walled cabin weight reduction groove of a spacecraft, thereby realizing the automated online measurement and compensation processing of the thin-walled cabin weight reduction groove of a spacecraft and improving processing efficiency and processing accuracy.

[0004] The technical solution of this invention is:

[0005] A method for online measurement and compensation machining of lightweight grooves in thin-walled spacecraft cabins includes the following steps:

[0006] (1) Clamp the thin-walled cabin onto the worktable of the CNC machine tool and import the design model of the thin-walled cabin into the control software of the CNC machine tool;

[0007] (2) Install a thickness measuring head on a CNC machine tool;

[0008] (3) uniformly setting m measuring points on the surface of each to-be-processed lightening groove of the thin-walled cabin body, and obtaining the theoretical thickness and the theoretical outer contour position of each measuring point according to the design model;

[0009] (4) measuring the actual thickness of each measuring point by a thickness measuring head, the cutting edge of the thickness measuring head being in contact with each measuring point when measuring the thickness, and obtaining the actual outer contour position of each measuring point by obtaining the position of the cutting edge of the thickness measuring head;

[0010] (5) calculating the compensation value for thickness compensation of each measuring point according to the actual thickness, the actual outer contour position, the theoretical thickness and the theoretical outer contour position of each measuring point;

[0011] (6) judging whether the compensation requirement is met according to the compensation values of all the measuring points of the current to-be-processed lightening groove, if yes, entering step (7), and if no, entering step (8);

[0012] (7) taking the minimum value of the compensation values of all the measuring points of the to-be-processed lightening groove as the compensation value for processing, and processing the to-be-processed lightening groove after compensating the tool length by using the compensation value;

[0013] (8) importing the measurement data of all the measuring points of the to-be-processed lightening groove into the control software of the numerical control machine tool, the measurement data including the actual outer contour position and the actual thickness of each measuring point, reconstructing the processing surface of the to-be-processed lightening groove according to the measurement data of all the measuring points by using the control software of the numerical control machine tool, replacing the to-be-processed surface in the theoretical model with the reconstructed processing surface, and processing the to-be-processed lightening groove by using the initial tool length based on the reconstructed processing surface;

[0014] (9) completing the processing of all the to-be-processed lightening grooves based on the method of steps (4) to (6).

[0015] Preferably, in step (5), the compensation value for thickness compensation of each measuring point is calculated by: calculating a thickness deviation value according to the actual thickness and the theoretical thickness; calculating an outer contour position deviation value according to the actual outer contour position and the theoretical outer contour position; and calculating the compensation value according to the thickness deviation value and the outer contour position deviation value.

[0016] Preferably, the compensation value is calculated by the following expression:

[0017] Δ = ΔZ - ΔH

[0018] ΔZ = Z1 - Z0

[0019] ΔH = H1 - H0

[0020] Wherein, Δ represents a compensation value, ΔZ represents a thickness deviation value, ΔH represents an outer contour position deviation value, Z1 represents an actual outer contour position, Z0 represents a theoretical outer contour position, H1 represents an actual thickness, and H0 represents a theoretical thickness.

[0021] Preferably, in the step (6), it is judged whether the compensation requirement is met, specifically:

[0022] According to the maximum value Δ of all the compensation values of the current to-be-processed lightening groove measuring points max and the minimum value Δ min , the compensation value deviation Δ' of the to-be-processed lightening groove is calculated, Δ' = Δ max - Δ min If Δ' is less than or equal to the size tolerance of the lightening groove, the compensation requirement is met, otherwise the compensation requirement is not met.

[0023] Preferably, the size tolerance of the lightening groove is 0.4 mm.

[0024] Preferably, the value range of m is 4-9.

[0025] Preferably, in the step (9), the processing of all the to-be-processed lightening grooves is completed based on the method of steps (4)-(6), specifically: n to-be-processed lightening grooves are taken as a group for grouping processing, and when each group is processed, the processing is completed after the measurement of all the to-be-processed lightening grooves.

[0026] Preferably, the value range of n is 4-8.

[0027] Compared with the prior art, the present application has the following advantages:

[0028] (1) The present application measures the structure outer contour position and thickness online, calculates the compensation value according to the measured values of the outer contour position and thickness, and then compensates the thickness based on the compensation value for processing, which greatly improves the processing efficiency compared with the method of trial cutting, thickness measurement, and compensation calculation;

[0029] (2) The present application considers both the outer contour position and the thickness, realizes high-precision compensation, and can more accurately control the processing procedure, thereby improving the processing precision;

[0030] (3) The present application reconstructs and replaces the processing surface according to the contour position and thickness measurement data, and then processes based on the reconstructed processing surface, thereby improving the processing precision and solving the problem of size out-of-tolerance of the lightening groove caused by single compensation. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 It is a flowchart of the online measurement and compensation processing method of the spacecraft thin-walled cabin lightening groove of the present application;

[0032] Figure 2 Fig. 1 is a schematic diagram of the profile and thickness comprehensive compensation principle of the present application;

[0033] Figure 3 Fig. 4 is a schematic diagram of the main measurement program of an embodiment of the present application;

[0034] Figure 4 Fig. 5 is a schematic diagram of the measurement path planning of an embodiment of the present application;

[0035] Figure 5 Fig. 6 is a schematic diagram of the measurement point distribution of an embodiment of the present application. DETAILED DESCRIPTION

[0036] The features and advantages of the present application will become more apparent from the detailed description in conjunction with the accompanying drawings.

[0037] The present application provides a spacecraft thin-walled cabin lightening groove online measurement and compensation processing method, based on high-precision machine tools, measuring heads and numerical control systems, first measuring the profile and thickness of the thin-walled structure, then designing an algorithm, calculating the compensation value according to the profile and thickness data, and finally calling the compensation value for processing, improving the automation degree of measurement and processing, realizing efficient and high-precision processing of thin-walled structure lightening grooves and ensuring the thickness size precision.

[0038] As shown in Fig. 1, the method comprises the following steps: Figure 1

[0039] Step one, install the thickness online measurement system. Mainly including the thickness measuring head, signal receiver and measurement macro program.

[0040] Step two, calibrate the thickness online measurement system. Including calibrating the ultrasonic propagation velocity of the calibration material and the outer profile measurement accuracy.

[0041] Specifically, the thickness measurement system used in the present application uses ultrasonic waves to measure thickness, and by using a standard block to calibrate the propagation velocity of the material to be processed, the thickness is measured.

[0042] Further, by using a standard block to calibrate, in a specific embodiment, the standard block material is 5B70 aluminum alloy, consistent with the material of the part to be measured, the thickness of the standard block is 5mm, the standard block is placed horizontally on the workbench surface, and the thickness measuring head is used for measurement, the thickness measuring head tip is in contact with the surface of the standard block, the time of ultrasonic wave propagation in the standard block is measured, and the propagation velocity of ultrasonic wave in the material is calculated to be 6200m / s according to the thickness of the standard block and the propagation time. In subsequent measurement, the thickness value of each measurement point is obtained by measuring the ultrasonic wave propagation time at each measurement point combined with the propagation velocity.

[0043] ​Further, the precision of the profile measurement using the standard block is measured, the bottom surface of the standard block is Z=0; when the thickness measuring head tip contacts the measurement point, the position of the measurement point tip is obtained as the outer profile position of the measurement point, the theoretical value is Z=5mm, and the deviation value of the outer profile position measurement is calculated according to the actual measurement value, and the measurement value of the subsequent outer profile position is compensated.

[0044] Further, considering different thickness sizes of the to-be-measured features, calibration standard blocks with different thicknesses are made, which are rectangular blocks with a size of 5mm*8mm, and the thicknesses are 0.7mm, 1.5mm, 2mm, 4mm, 6mm and 8mm.

[0045] Step three, execute the measurement main program. The program content mainly includes initial variables, target points and measurement macro programs.

[0046] Step four, record the profile and thickness data. Measure n lightening grooves, measure m points in each lightening groove, and record the profile and thickness data measured by the macro program in the variables, such as when the pth point in the nth lightening groove is measured, p≤m, the profile data is stored as FCX_ABC[2*(n-1)*m+2*p-1], and the thickness data is stored in FCX_ABC[2*(n-1)*m+2*p].

[0047] Specifically, from the perspective of machining precision, each lightening groove is measured and machined to have optimal machining precision, but the thickness measuring head and the machining tool need to be switched, which affects the machining efficiency, so n lightening grooves are grouped for grouping measurement and machining, n is 4-8 according to actual machining experience, which can improve the working efficiency while ensuring the machining precision.

[0048] Further, considering the measurement precision and efficiency, m is 4-8.

[0049] Step five, design an online measurement compensation value algorithm. After obtaining the profile and thickness data of the features, an algorithm is designed to compensate the profile and thickness simultaneously to achieve accurate high-precision compensation. Figure 2The profile and thickness compensation principle designed for the present application, the theoretical thickness is H0, and the processing program is compiled according to the theoretical outer profile position Z0. The actual position is shown in the figure, and the actual thickness is H1. The measuring head starts measuring when it touches the actual outer profile surface. The position at this point is recorded as Z1. The outer profile changes to ΔZ = Z1-Z0. ΔZ is positive, indicating that the actual outer profile is higher than the theoretical outer profile. ΔZ is negative, indicating that the actual outer profile is lower than the theoretical outer profile. Then the thickness deviation is compensated, and the thickness deviation is ΔH = H1-H0. The final comprehensive compensation value of a single point is Δ = ΔZ-ΔH. The data stored in step four is called to calculate the comprehensive compensation value Δ of all measurement points = FCX_JS[P], such as the comprehensive compensation value of the nth slot at the pth point is stored in FCX_JS[P] = FCX_ABC[2*(n-1)*m+2*p-1]-FCX_ABC[2*(n-1)*m+2*p], as shown in Table 1:

[0050] Table 1 Storage method of measurement information of the embodiment of the present application

[0051]

[0052] Step six, judge and determine the compensation value. Compare the comprehensive compensation values in a single slot to obtain the maximum compensation value Δ max and the minimum compensation value Δ min , Δ' = Δ max - Δ min . When Δ' is less than or equal to the size tolerance, that is, the compensation requirement is met, store the compensation value in a variable, such as the compensation value of the nth slot is stored as FCX_BC[n]. When Δ' is greater than the tolerance, execute step seven.

[0053] Specifically, in a specific embodiment, the size requirement of the processing thickness of the lightening groove is 1.2±0.2mm-8±0.2mm, that is, the size tolerance is 0.4mm. When Δ' ≤ 0.4mm, the compensation requirement is met, otherwise the compensation requirement is not met.

[0054] Step seven, reconstruct the curved surface and regenerate the program. When the compensation value cannot be used alone for compensation processing, the profile and thickness data are imported into the programming software, the curved surface is reconstructed and replaced, and the program is regenerated. After reconstructing the curved surface, the current slot does not need to call the compensation value again, and the compensation value calling module is removed.

[0055] Step eight, execute the compensation value calling processing program. Add a compensation value calling module at the beginning of each lightening groove processing program to call the tool length compensation value of the corresponding slot, so as to realize automatic compensation value calling processing.

[0056] Embodiment

[0057] Developing the measurement main program: first, define the initial variables, including the measured feature thickness, tolerance, minimum allowable thickness, machining allowance, feed rate, etc., then locate the measurement target point, finally call the measurement macro program to measure, the measurement main program is shown in Figure 3 In this embodiment, four lightening grooves are selected as a group for measurement and processing, Figure 4 The path planning diagram of the measurement main program.

[0058] Recording profile and thickness data: five points are measured for each lightening groove, the measurement point position is shown in Figure 5 According to the written loop, the profile and thickness measurement results of the five points are stored, the profile results of the nth lightening groove are stored in FCX_ABC[10*n-9], FCX_ABC[10*n-7], FCX_ABC[10*n-5], FCX_ABC[10*n-3], FCX_ABC[10*n-1] in turn, and the thickness results are stored in FCX_ABC[10*n-8], FCX_ABC[10*n-6], FCX_ABC[10*n-4], FCX_ABC[10*n-2], FCX_ABC[10*n] in turn, and each 10 variable addresses save the complete data of a lightening groove.

[0059] Calculate the comprehensive compensation value of each point: a total of 20 compensation values, FCX_JS[1], FCX_JS[2], …, FCX_JS

[19] , FCX_JS

[20] , in order, every five compensation values are a group, that is, the comprehensive compensation value in the same lightening groove.

[0060] Determine and determine the compensation value: compare the comprehensive compensation value in a single groove, and obtain the maximum compensation value Δ max And the minimum compensation value Δ min , Δ' = Δ max - Δ min When Δ' is less than or equal to the size tolerance, that is, it meets the compensation requirement, store this compensation value in the variable, such as the compensation value of the nth groove is stored as FCX_BC[n], then the final compensation values of the four lightening grooves are FCX_BC[1], FCX_BC[2], FCX_BC[3], FCX_BC[4]. If Δ' is greater than the tolerance, go to step seven.

[0061] Reconstruct the surface and regenerate the program: take out the lightening groove with the out-of-tolerance, import the profile and thickness data into the programming software, reconstruct the surface, replace the surface, and regenerate the program, and remove the compensation value calling module in the program by using ";;;;;".

[0062] The execution compensation value calling processing program: the compensation value module of the beginning program segment is called by each lightening groove processing program, L_39(FCX_BC[1], 0), L_39(FCX_BC[2], 0), L_39(FCX_BC[3], 0), L_39(FCX_BC[4], 0), the tool length compensation value of the corresponding groove is called, and the automatic compensation value calling processing is realized.

[0063] The contents not described in detail in the specification of the present application are the known technology of the person skilled in the art.

Claims

1. A method for online measurement and compensation machining of lightweight grooves in thin-walled spacecraft cabins, characterized in that, Includes the following steps: (1) Clamp the thin-walled cabin onto the worktable of the CNC machine tool and import the design model of the thin-walled cabin into the control software of the CNC machine tool; (2) Install a thickness measuring head on a CNC machine tool; (3) m measurement points are uniformly set on the surface of each lightening groove to be processed in the thin-walled cabin, and the theoretical thickness and theoretical outer contour position of each measurement point are obtained according to the design model. (4) The actual thickness of each measurement point is measured by a thickness probe. The tip of the thickness probe contacts each measurement point when measuring the thickness. The actual outer contour position of each measurement point is obtained by obtaining the position of the tip of the thickness probe. (5) Calculate the compensation value for thickness compensation for each measurement point based on the actual thickness, actual outer contour position, theoretical thickness and theoretical outer contour position of each measurement point; (6) Based on the compensation values ​​of all measurement points of the current lightening groove to be processed, determine whether the compensation requirements are met. If they are met, proceed to step (7); otherwise, proceed to step (8). (7) Obtain the minimum value of the compensation value of all measurement points of the lightening groove to be processed as the compensation value used for processing. After compensating the tool length with this compensation value, process the lightening groove to be processed. (8) Import the measurement data of all measurement points of the lightening groove to be machined into the control software of the CNC machine tool. The measurement data includes the actual outer contour position and actual thickness of each measurement point. Use the control software of the CNC machine tool to reconstruct the machining surface of the lightening groove to be machined according to the measurement data of all measurement points, and use the reconstructed machining surface to replace the machining surface in the theoretical model. Based on the reconstructed machining surface, use the initial tool length to machine the lightening groove to be machined. (9) Based on the methods in steps (4) to (6), complete the processing of all the lightening grooves to be processed.

2. The method for online measurement and compensation processing of a thin-walled spacecraft cabin weight reduction groove according to claim 1, characterized in that, In step (5), the compensation value for thickness compensation at each measurement point is calculated, specifically: the thickness deviation value is calculated based on the actual thickness and the theoretical thickness; the outer contour position deviation value is calculated based on the actual outer contour position and the theoretical outer contour position; and the compensation value is calculated based on the thickness deviation value and the outer contour position deviation value.

3. The method for online measurement and compensation processing of a spacecraft thin-walled cabin weight reduction groove according to claim 2, characterized in that, The compensation value is calculated using the following expression: Δ=ΔZ-ΔH ΔZ=Z1-Z0 ΔH=H1-H0 Where Δ represents the compensation value, ΔZ represents the thickness deviation value, ΔH represents the outer contour position deviation value, Z1 represents the actual outer contour position, Z0 represents the theoretical outer contour position, H1 represents the actual thickness, and H0 represents the theoretical thickness.

4. The method for online measurement and compensation processing of a thin-walled spacecraft cabin weight reduction groove according to claim 3, characterized in that, In step (6), determining whether the compensation requirements are met specifically involves: Based on the maximum compensation value Δ of all measuring points in the current lightening tank to be processed. max and minimum value Δ min Calculate the compensation deviation value Δ' = Δ for the lightening groove to be processed. max -Δ min If Δ' is less than or equal to the dimensional tolerance of the relief groove, then the compensation requirement is met; otherwise, the compensation requirement is not met.

5. The method for online measurement and compensation processing of a thin-walled spacecraft cabin weight reduction groove according to claim 4, characterized in that, The dimensional tolerance of the light-reducing groove is 0.4 mm.

6. A method for online measurement and compensation processing of a spacecraft thin-walled cabin weight reduction groove according to any one of claims 1 to 5, characterized in that, The value of m ranges from 4 to 9.

7. A method for online measurement and compensation processing of a spacecraft thin-walled cabin weight reduction groove according to claims 1-5, characterized in that, In step (9), the processing of all the light-reducing grooves to be processed is completed based on the method of steps (4) to (6). Specifically, the n light-reducing grooves to be processed are grouped and processed. When processing each group, the measurement of all the light-reducing grooves to be processed is completed before processing.

8. The method for online measurement and compensation processing of a spacecraft thin-walled cabin weight reduction groove according to claim 7, characterized in that, The value of n ranges from 4 to 8.

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