Tool for testing center of mass and rotational inertia

Abstract

The invention discloses a mass center and rotational inertia testing tool, which comprises an upper frame used for loading a tested product, the tested product forms a load through the gravity of the tested product, and the load is uniformly distributed in the length range of the tested product; a mounting surface is formed on the lower frame, the lower frame is fixedly connected to the upper frame through the mounting surface, the measuring equipment is connected to the lower frame through screws, and loads are uniformly distributed on the lower frame so that the upper frame can generate deflection errors. According to the mass center and rotational inertia testing tool, the influence of deformation errors of the tool on the accuracy of measured data is fundamentally solved, the deflection deformation of the tool in a cantilever state is reduced to 0.02 mm, the influence of the deflection deformation on the mass center and rotational inertia measurement can be ignored, meanwhile, through repeated positioning design of the tool, the measurement accuracy of the mass center and the rotational inertia is improved, and the measurement accuracy is improved. Therefore, the tool required in the testing process has repeated positioning precision in a controllable precision range, the cost is low, and accurate centroid and rotational inertia parameters can be obtained.

Description

Technical Field

[0001] The invention relates to the technical field of satellite center of mass testing, and in particular to a center of mass and moment of inertia testing tool. Background Art

[0002] The center of mass and moment of inertia are inherent characteristics of spacecraft and are important parameters that affect their operating attitude and stability. Therefore, it is necessary to obtain accurate center of mass and moment of inertia parameters. When the L-type quality measurement fixture measures large-load products, it can be regarded as a cantilever beam structure. The gravity load of the measured product is evenly distributed on the quality measurement fixture through the installation point. The evenly distributed load will cause the horizontal axis of the product to shift, and the vertical section where the center of mass is located will shift to produce deflection errors. The longer the size, the greater the load and the easier it is to shift downward, which will greatly affect the accuracy of quality measurement and moment of inertia.

[0003] Generally, the tooling for testing the center of mass and moment of inertia of a product is to first measure the center of mass data in the vertical state through the quality measuring flower pot tooling, and then fix the product and the flower pot at the L end through the thin-walled L-shaped tooling to measure the data in the horizontal state, and use the laser tracker to assist in calibrating the center of mass position in each state, and calculate the center of mass by calculating the conversion matrix. For example, the invention patent with the publication number of CN111947834A discloses a satellite high-precision center of mass measurement method combined with a laser tracker, which eliminates the tooling manufacturing error and tooling deformation error through high-precision measurement technology, and adopts the combined laser tracker to calibrate the center of mass position of each side downward, and then calculates a more accurate center of mass position through the conversion matrix and the measurement value. First of all, this method is not compatible with the measuring equipment, and can only calculate a more accurate center of mass position through calibration alone, and the measurement of the moment of inertia is measured by directly using the measured center of mass position in the equipment. Therefore, this method cannot change the measuring equipment software data to the calculated accurate center of mass position, so the error in the moment of inertia measurement still exists, and more complex calculation conversion is required to reduce the error, and the method of combining the laser tracker is expensive.

[0004] Based on the above technical problems, technicians in this field urgently need to develop a center of mass and moment of inertia testing tool that can reduce the impact of deformation errors on the accuracy of measurement data, has low cost, and can obtain accurate center of mass and moment of inertia parameters. Summary of the invention

[0005] The object of the present invention is to provide a center of mass and moment of inertia testing tool which can reduce the influence of deformation error on the accuracy of measurement data, has low cost, and can obtain accurate center of mass and moment of inertia parameters.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A center of mass and moment of inertia testing tool of the present invention comprises:

[0008] An upper frame is used to load the product under test, the product under test forms a load by its own gravity, and the load is evenly distributed within the length of the product under test. A mounting surface is formed on the upper frame, and the load is evenly distributed on the upper frame to generate a deflection error on the upper frame; and

[0009] A lower frame is fixedly connected to the upper frame, and a measuring device is connected to the lower frame by screws.

[0010] Furthermore, according to the formula, the centroid measurement error e1 is:

[0011] Wherein, T is the torque accuracy of the measuring device, and M is the mass of the measured product;

[0012] The mass of the measuring equipment is at most 3T, and the mass of the measured product is at most 0.7T.

[0013] Preferably, the measuring device has a central coarse positioning pin with a diameter of 40 mm, and the center of the lower frame and the coarse positioning pin are hole-shaft matched, and the diameter gap is 0.1 mm.

[0014] Furthermore, the geometric dimensions of the upper frame are 2100 mm long and 2300 mm high, and the bending section coefficient W of the rectangular cross-section beam is: in,

[0015] b is the width of the rectangular section and h is the height of the section.

[0016] The measuring device is provided with a plurality of threaded holes for connecting with the lower frame, and the measuring device is provided with at least two mounting holes on the outer circle, and a positioning pin is formed by a turned screw head at a relative position at the bottom of the lower frame, and positioning is achieved by the positioning pin cooperating with the mounting hole, and the diameter of the positioning pin is 15 mm, and the gap with the mounting hole is 0.02 mm.

[0017] In the above technical solution, the center of mass and moment of inertia testing tool provided by the present invention has the following beneficial effects:

[0018] A center of mass and moment of inertia testing tool of the present invention fundamentally solves the influence of the deformation error of the tool on the accuracy of the measurement data, and reduces the deflection deformation of the tool in the cantilever state to 0.02mm, and the influence on the center of mass and moment of inertia measurement can be ignored. At the same time, through the repeated positioning design of the tool, the tool required for the test process has a repeated positioning accuracy within a controllable accuracy range, and the cost is low, so that accurate center of mass and moment of inertia parameters can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0020] Figure 1 A schematic diagram of the overall structure of a center of mass and moment of inertia testing tool provided in an embodiment of the present invention;

[0021] Figure 2 A schematic diagram of the center of mass position and mounting surface of a product under test of a center of mass and moment of inertia test fixture provided in an embodiment of the present invention;

[0022] Figure 3 A schematic diagram of a positioning pin hole on the center of mass mounting surface of a product under test of a center of mass and moment of inertia test tool provided in an embodiment of the present invention;

[0023] Figure 4 A schematic diagram of a horizontal quality test of a product under test of a center of mass and moment of inertia test tool provided by an embodiment of the present invention;

[0024] Figure 5 A first schematic diagram of a deflection error of a center of mass and moment of inertia test tool provided by an embodiment of the present invention;

[0025] Figure 6 A second schematic diagram of a deflection error of a center of mass and moment of inertia test tool provided by an embodiment of the present invention;

[0026] Figure 7 A schematic diagram of an upper frame structure of a center of mass and moment of inertia testing tool provided in an embodiment of the present invention;

[0027] Figure 8 A cross-sectional view of the upper frame structure of a center of mass and moment of inertia testing tool provided in an embodiment of the present invention;

[0028] Fig. 9 A cross-sectional view of a lower frame structure of a center of mass and moment of inertia testing tool provided in an embodiment of the present invention;

[0029] Fig.10 A schematic diagram of the connection between a lower frame of a center of mass and moment of inertia testing tool and a testing device provided by an embodiment of the present invention;

[0030] Fig.11 A schematic diagram of edge mounting holes of a center of mass and moment of inertia test tool measuring device provided in an embodiment of the present invention;

[0031] Fig.12 A schematic diagram of the positioning pins of the lower frame of a center of mass and moment of inertia testing tool provided in an embodiment of the present invention.

[0032] Description of reference numerals:

[0033] 1. Upper frame; 2. Lower frame; 3. Measuring equipment; 4. Product under test;

[0034] 101, mounting surface;

[0035] 201, positioning pin;

[0036] 301. Mounting hole. DETAILED DESCRIPTION

[0037] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0038] See also Figures 1 to 12 As shown;

[0039] A center of mass and moment of inertia testing tool of the present invention comprises:

[0040] The upper frame 1 is used to load the product 4 to be tested, which is equivalent to a cantilever beam structure. The product 4 to be tested is affected by its own gravity load, which is evenly distributed over the entire length of the product 4 to be tested. The evenly distributed load causes the horizontal axis of the product 4 to be tested to shift downward, and the vertical section where the center of mass is located shifts, resulting in a deflection error, thereby affecting the measurement accuracy. An installation surface 101 is formed on the upper frame 1, and the load is evenly distributed on the upper frame to cause a deflection error in the upper frame. Similarly, the load is evenly distributed on the surface of the upper frame 1 through the installation surface 101 connected to the upper frame 1, causing a deflection error in the thin-walled upper frame 1, thereby affecting the measurement accuracy. According to actual conditions, the structural design and rigidity of the product have ensured that its deflection deformation is small, and most tooling considers cost, and the material selection and structural design are relatively simple. In actual conditions, the deflection error caused by the tooling often affects the final measurement accuracy.

[0041] A lower frame fixedly connected to the upper frame, and a measuring device connected to the lower frame by screws,

[0042] As a further introduction to this embodiment, according to the formula, the centroid measurement error e1 is:

[0043] Wherein, T is the torque accuracy of the measuring device 3, and M is the mass of the measured product 4;

[0044] It can be seen from the formula that as the product mass M increases, the center of mass measurement error gradually decreases. The mass of the measuring device 3 is at most 3T, and the mass of the measured product 4 is at most 0.7T, so the center of mass and the overall mass of the rotating tooling need to be controlled within the range of 1.3T-2T. The center of mass and moment of inertia data actually measured are the data of the product based on the coordinate system of the measuring device 3, and what is needed is the data of the product based on its own coordinate system, so the positioning and resetting accuracy of the product on the measuring device will also affect the final measurement result.

[0045] As a preferred technical solution of this embodiment, the measuring device 3 has a central coarse positioning pin with a diameter of 40 mm, and the center of the lower frame 2 is matched with the coarse positioning pin as a hole axis, and the diameter gap is 0.1 mm. While ensuring a certain positioning accuracy, the center of mass and moment of inertia measurement tooling can fall smoothly. One coarse positioning pin cannot position the product and tooling to the required accuracy.

[0046] As a further introduction to this embodiment, the geometric dimensions of the upper frame 1 are 2100mm long and 2300mm high. The design first considers its bending resistance. According to finite element analysis, under the same length, height and mass restrictions, the aluminum plate without lightweight and bending resistance structure design will produce a deformation of about 0.5mm at the load center under a product load of 0.7T, which has a great impact on the measurement accuracy. And according to the bending section coefficient W of the rectangular cross-section beam: in,

[0047] b is the width of the rectangular section, and h is the height of the section. From the formula, we can see that increasing the width and height of the section can increase the bending resistance. The length, width and height of the upper frame in the YZ view have been limited according to the product installation size and center of mass position, and have sufficient bending resistance.

[0048] Therefore, increasing the width of the XZ section can substantially increase the bending resistance of the overall structure, but the weight will also increase exponentially, and the structure needs to be designed to be lightweight. Common lightweight forms include tic-tac-toe, X-shaped, W-shaped, and circular hole shapes. After finite element analysis, the W-shaped structure has the greatest stiffness under the same structural material consumption. Combined with the stress points on the installation surface of this product, a W-shaped lightweight design structure is designed at each installation point. The overall lightweight structure adopts a combination of tic-tac-toe and W-shaped structures. After finite element analysis, the deformation at the load center of mass is 0.02mm.

[0049] Finally, the counterweight is designed to adjust the center of mass of the measuring tool when it is unloaded and loaded to within 100 mm of the center area of ​​the measuring equipment.

[0050] As a further introduction to this embodiment, the measuring device 3 is provided with a plurality of threaded holes for connection with the lower frame 2, and the measuring device 3 has no extra pin holes. To ensure the positioning accuracy of the tooling and the disassembly and assembly reset, the measuring device 3 is provided with at least two mounting holes 301 on the outer ring, and the bottom relative position of the lower frame 2 is provided with a positioning pin 201 formed by a turned screw head. The positioning is achieved by the positioning pin 201 cooperating with the mounting hole 301, thereby ensuring the positioning accuracy and reset accuracy of the tooling 2 and the test device 3. The diameter of the positioning pin 201 is 15 mm, and the clearance with the mounting hole 301 is 0.02 mm.

[0051] In the above technical solution, the center of mass and moment of inertia testing tool provided by the present invention has the following beneficial effects:

[0052] A center of mass and moment of inertia testing tool of the present invention fundamentally solves the influence of the deformation error of the tool on the accuracy of the measurement data, and reduces the deflection deformation of the tool in the cantilever state to 0.02mm, and the influence on the center of mass and moment of inertia measurement can be ignored. At the same time, through the repeated positioning design of the tool, the tool required for the test process has a repeated positioning accuracy within a controllable accuracy range, and the cost is low, so that accurate center of mass and moment of inertia parameters can be obtained.

[0053] The above description is only by way of illustration of certain exemplary embodiments of the present invention. It is undoubted that those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A center of mass and moment of inertia test tool, characterized in that: The test fixture includes: An upper frame (1) is used to load a product (4) to be tested, wherein the product (4) to be tested forms a load by its own gravity, and the load is evenly distributed within the length range of the product (4) to be tested, and a mounting surface (101) is formed on the upper frame (1), and the load is evenly distributed on the upper frame (1) so that the upper frame (1) generates a deflection error; and A lower frame (2) is fixedly connected to the upper frame (1), and a measuring device (3) is connected to the lower frame (2) via screws.

2. A center of mass and moment of inertia testing tool according to claim 1, characterized in that: According to the formula, the centroid measurement error e1 is: Wherein, T is the torque accuracy of the measuring device (3), and M is the mass of the measured product (4); The mass of the measuring device (3) is at most 3T, and the mass of the measured product (4) is at most 0.7T.

3. A center of mass and moment of inertia testing tool according to claim 1, characterized in that: The measuring device (3) has a central coarse positioning pin with a diameter of 40 mm, and the center of the lower frame (2) is hole-axis matched with the coarse positioning pin, and the diameter gap is 0.1 mm.

4. A center of mass and moment of inertia testing tool according to claim 1, characterized in that: The geometric dimensions of the upper frame (1) are 2100 mm in length and 2300 mm in height, and the bending section coefficient W of the rectangular cross-section beam is: in, b is the width of the rectangular section and h is the height of the section.

5. A center of mass and moment of inertia testing tool according to claim 1, characterized in that: The measuring device (3) is provided with a plurality of threaded holes for connecting with the lower frame (2), and the measuring device (3) is provided with at least two mounting holes (301) on the outer ring, and a positioning pin (201) formed by a turned screw head is provided at a relative position at the bottom of the lower frame (2), and positioning is achieved by the positioning pin (201) cooperating with the mounting hole (301), and the diameter of the positioning pin (201) is 15 mm, and the gap between the positioning pin (201) and the mounting hole (301) is 0.02 mm.

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