A method for measuring the center of mass of a large-span wing aircraft

Abstract

This invention relates to a method for measuring the center of mass of a large-span wing aircraft. The method involves placing the aircraft under test on a mass center of mass measuring device and reading its mass. The aircraft coordinate system is defined as a left-handed three-dimensional coordinate system, with the aircraft's nose as the origin and the aircraft's retrograde direction as the x-axis. The axial center of mass x-axis is obtained by calculating the torque along the y-axis using the unbalanced torque method. c The torque along the x-axis is obtained by using the unbalanced torque method, and the axial centroid y-axis is then obtained. c Rotate the aircraft under test counterclockwise and clockwise around the x-axis respectively, and obtain the corresponding center of mass x using the method in the first two steps. c1 x c2 ; center of mass y c1 y c2 ; Calculate the radial centroid z of the flight under test c This invention effectively solves the problem of being unable to measure the center of mass when an aircraft cannot rotate within a large range. It is particularly useful for large-span wing aircraft, where rotation is restricted due to wing movement. The invention provides a method for measuring the center of mass of an aircraft with small-angle rotation. The design is simple and does not require complex modifications to existing auxiliary measurement devices.

Description

Technical Field

[0001] This invention belongs to the field of aircraft measurement technology, specifically relating to a method for measuring the center of mass of a large-span wing aircraft. Background Technology

[0002] Current methods for measuring the center of mass of aircraft require extensive rotation of the aircraft to obtain its radial center of mass position. For aircraft with large wingspans, traditional methods involve rotating the aircraft sequentially at large angles of 90°, 180°, and 270° along the flight direction (axial direction) to determine the radial center of mass position by calculating the corresponding torque. This large-angle rotation typically requires the use of other auxiliary rotation mechanisms, making the measurement process cumbersome. When measuring large-wingspan aircraft, the significant rotation can interfere with the testing equipment. Using elevated mounting brackets would make aircraft installation and equipment operation very inconvenient, and the mounting brackets require extremely high rigidity, posing certain safety hazards. Summary of the Invention

[0003] (1) Purpose of the invention:

[0004] This method proposes a centroid measurement method that can obtain the centroid position of an aircraft when the aircraft rotates at a small angle.

[0005] The present invention aims to develop a method for measuring the center of mass of an aircraft, which solves the problem of measuring the center of mass of an aircraft when the wing cannot rotate within a wide range.

[0006] (2) Invention technical solution:

[0007] The present invention proposes a method for measuring the center of mass of a large-span wing aircraft, which involves placing the aircraft under test on a mass center of mass measuring device and reading the mass of the aircraft under test.

[0008] Define the aircraft coordinate system as a left-handed three-dimensional coordinate system, with the aircraft's nose as the origin and the aircraft's retrograde direction as the x-axis;

[0009] Step S1: Calculate the torque along the y-axis using the unbalanced torque method to obtain the axial centroid x. c ;

[0010] Step S2: Calculate the torque along the x-axis using the unbalanced torque method to obtain the axial centroid y. c ;

[0011] Step S3: Rotate the aircraft under test counterclockwise and clockwise around the x-axis respectively, and obtain the corresponding centroid x using the methods in steps S1 and S2. c1 x c2 ; center of mass y c1 yc2 ;

[0012] Step S4: Calculate the radial centroid z of the flight to be tested. c .

[0013] Furthermore, in order to eliminate the problem of deviation between the axial direction of the aircraft under test and the mass center of mass measuring device, after completing one measurement, the aircraft can be rotated 180° around the x-axis and placed on the measuring device, and steps S1-S4 can be repeated, and finally the average value is calculated.

[0014] Furthermore, the mass center of mass measuring device is equipped with three weighing sensors; one weighing sensor is arranged on the x-axis; the other two sensors are symmetrically arranged on both sides of the aircraft.

[0015] Furthermore, the mass of the aircraft is the sum of the measured values ​​of each weighing sensor; w = w1 + w2 + w3; w is the mass of the aircraft, and w1, w2, and w3 are the measured values ​​of the sensors at points 1, 2, and 3, respectively.

[0016] Furthermore, the axial center of mass of the aircraft, y c The moment of the aircraft in the oxy plane is obtained by taking moments about ox in the plane oxy based on the principle of force and moment balance; the radial centroid y of the aircraft in the oxy plane is... c = (w1H1-w2H2) / w.

[0017] Furthermore, the axial center of mass of the spacecraft x c The moment obtained by taking moments over OY is the axial centroid x of the spacecraft. c = (w1L1+w2L2-w3L3) / w.

[0018] Furthermore, the aircraft is rotated counterclockwise around the x-axis by a certain angle to obtain the position of the center of mass c1, and rotated clockwise around the x-axis by a certain angle to obtain the position of the center of mass c2, and c1 and c2 lie on the arc centered at point o.

[0019] Furthermore, based on the principle of force and torque balance, the following equation can be obtained.

[0020] y c1 =(y c 2 +z c 2 ) 0.5 cos(a+b)

[0021] y c2 =(y c 2 +z c 2 ) 0.5 cos(ab)

[0022] yc1 / y c2 =cos(a+b) / cos(ab)

[0023] By rationally designing the rotation angle based on the actual situation of the aircraft, the original angle 'a' at position 'c' can be obtained, and 'z' can be obtained based on the positional relationship. c =y c tana=tana(w1H1-w2H2) / w; in the formula, b is the angle of clockwise rotation of the aircraft around the x-axis.

[0024] (3) Beneficial technical effects of the invention:

[0025] This invention effectively solves the problem of being unable to measure the center of mass when an aircraft cannot rotate within a large range. It is particularly useful for large-span wing aircraft, where rotation is restricted due to the wing's movement. The invention provides a method for measuring the center of mass of an aircraft with small-angle rotation. The design is simple and does not require complex modifications to existing auxiliary measuring devices. Attached Figure Description

[0026] Figure 1 This is a schematic diagram showing the placement of the aircraft under test.

[0027] The equipment includes: 1. Measuring platform; 2. Rolling mechanism; 3. Reference ruler; 4. Aircraft under test.

[0028] Figure 2 This is a schematic diagram showing the sensor installation location;

[0029] Figure 3 This is a schematic diagram showing the location of the centroid on the oyz plane. Detailed Implementation

[0030] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] The method for measuring the center of mass of an aircraft proposed in this invention includes the following steps:

[0032] (1) See Appendix Figure 1The aircraft under test is placed on the mass center of mass measuring device. To facilitate rotation and adjustment of the aircraft under test, the mass center of mass measuring device is equipped with a mechanism to facilitate the rotation of the large-span wing aircraft under test. Alternatively, corresponding finished equipment, such as the MPTA-F500 UAV center of mass and thrust measuring platform, can be directly used with adaptive modifications. The measuring device used includes: measuring device platform 1, rolling mechanism 2, reference ruler 3, and aircraft under test 4. During measurement, the aircraft under test 4 is mounted on the measuring device platform 1, and both ends are connected by the rolling mechanism 2. The clamping and rolling mechanism 2 is designed to facilitate the rotation adjustment of the aircraft under test; the reference ruler 3 is used to adjust the spatial fixed position of the aircraft under test to ensure that its heading coincides with the X-axis of the measuring equipment; as described in the invention, the aircraft under test needs to be rotated counterclockwise and clockwise around the X-axis during the measurement process. The front and rear ends of the aircraft are fixed and positioned by a circular frame structure. In order to achieve more accurate rotation positioning, several circumferentially arranged limiting holes are provided on the circular end frame; after rotating to the designated position, the spatial position can be achieved by cooperating with the positioning pin.

[0033] In the design of centroid measurement equipment, a multi-point weighing method is used for measurement, typically employing a three-point support method; the vertical projection of the three weighing sensors on the platform is as follows: Figure 2 As shown in the diagram; points 1, 2, and 3 represent the contact points between the three load cells and the upper platform, respectively. ox and oy are the reference axes of the measuring equipment, the origin o is the positioning center of the device, and H1, H2, L1, L2, and L3 are the perpendicular distances between the three load cells and the reference axes ox and oy, respectively. Let oxyz be the coordinate axes of the aircraft, with the x-axis of device o coinciding with the ox axis, and point C being the center of mass of the aircraft in the oxy plane.

[0034] (2) Adjust the clamping fixture design to ensure that the projection of the aircraft axis on the oxy plane coincides with the ox axis when the aircraft is installed. Typically, to eliminate the influence of the coincidence degree between the aircraft axis and the ox axis on the test results, after completing one measurement, the aircraft can be rotated 180° around the x-axis and placed on the measuring equipment. Steps S1-S4 are repeated, and the average value is calculated. When the aircraft is placed upright, if the aircraft axis and the ox axis form a certain angle clockwise; after rotating the aircraft 180° around the x-axis, the aircraft axis and the ox axis will form a certain angle counterclockwise. In later calculations, the influence of this error can be automatically eliminated. For details on how to eliminate this error, please refer to the subsequent implementation process.

[0035] (3) As shown in the figure Figure 1 , 3As shown, the rotation angle b should be reasonably designed according to the actual situation of the aircraft, marked on the tooling fixture, and fixed devices such as pins should be set. The rotation angle b should be given before the aircraft is tested and used for tooling design and manufacturing. In the specific implementation process, the rotation angle b can be selected from some angles that are easy to calculate, such as 10°, 15°, etc.

[0036] (4) During measurement, first install the aircraft in place as required in step (2), and then measure the axial center of mass x of the aircraft according to the method. c Then measure y c And record it;

[0037] Based on the principle of force and moment balance, taking moments about ox in the plane oxy, we can obtain the radial center of mass y of the aircraft in the oxy plane. c 0° =(w1H1-w2H2) / w;

[0038] Taking moments about OY yields the axial centroid x. c 0° =(w1L1+w2L2-w3L3) / w;

[0039] During the calculation, 0° represents the initial horizontal measurement state of the aircraft under test;

[0040] Rotate the spacecraft counterclockwise by an angle b around the x-axis to obtain the position of the center of mass c1, and rotate it clockwise by an angle b around the x-axis to obtain the position of the center of mass c2. The positions c1 and c2 lie on an arc centered at point o. Figure 3 As shown.

[0041] (5) Data processing:

[0042] Based on the principle of force and torque balance and step (3), the following equation can be obtained.

[0043] y c1 0° =(y c 2 +z c 2 ) 0.5 cos(a+b)

[0044] y c2 0° =(y c 2 +z c 2 ) 0.5 cos(ab)

[0045] y c1 0° / y c2 0°=cos(a+b) / cos(ab)

[0046] Since the rotation angle b of the aircraft is known, the original angle a at position c can be calculated, and z can be obtained based on the positional relationship. c =y c tan a=tan a(w1H1-w2H2) / w.

[0047] (6) Due to the machining and installation errors between the equipment axis and the aircraft axis, the accuracy of axial and radial torque calculations will be affected, resulting in a deviation in the calculated center of mass position. To eliminate the problem of deviation between the axial direction of the aircraft under test and the mass center of mass measuring equipment, after completing one measurement, the aircraft is rotated 180° around the x-axis and placed on the measuring equipment. (2) to (5) are repeated to obtain x c 180° y c 180° z c 180° .

[0048] (7) Calculate the center of mass of the aircraft:

[0049] Xc=(x c 0° +x c 180° ) / 2

[0050] Yc=(y c 0° +y c 180° ) / 2

[0051] Zc=(z c 0° +z c 180° ) / 2

[0052] This provided accurate data on the center of mass of the large wingspan aircraft.

[0053] Through the above specific implementation process, this invention can effectively solve the problem of being unable to measure the center of mass when the aircraft cannot rotate within a large range. It provides a method for measuring the center of mass of an aircraft with small-angle rotation; the operation is simple and the measurement results are reliable.

[0054] The above specific embodiments or examples are only used to explain the technical solutions of the present invention and are not intended to limit the present application. Parts not described in detail are considered to be conventional technical means or common knowledge in the field. Those skilled in the art should understand that, based on the design concept of the present application, it is possible to make adaptive modifications to the technical solutions described in the foregoing embodiments or to make equivalent substitutions for some or all of the technical features. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for measuring the center of mass of a large-span wing aircraft, characterized in that, Place the aircraft under test on the mass center of mass measurement device and read the mass of the aircraft under test; Define the aircraft coordinate system as a left-handed three-dimensional coordinate system, with the aircraft's nose as the origin and the aircraft's retrograde direction as the x-axis; Step S1: Calculate the torque along the y-axis using the unbalanced torque method to obtain the axial centroid x. c ; Step S2: Calculate the torque along the x-axis using the unbalanced torque method to obtain the radial centroid y. c ; Step S3: Rotate the aircraft under test counterclockwise and clockwise around the x-axis respectively, and obtain the corresponding axial centroid x using the methods in steps S1 and S2. c1 x c2 Radial centroid y c1 y c2 ; Step S4: Calculate the radial centroid z of the test aircraft. c ; The mass centroid measuring device is equipped with three weighing sensors; one weighing sensor is located on the x-axis; the other two sensors are symmetrically arranged on both sides of the aircraft. The mass of the aircraft is the sum of the measured values ​​from all the weighing sensors; w = w1 + w2 + w3; where w is the mass of the aircraft. 1、 w2 and w3 are the measured values ​​of the sensor at points 1, 2 and 3, respectively; The axial center of mass of the aircraft y c The moment of the aircraft in the oxy plane is obtained by taking moments about ox in the plane oxy based on the principle of force and moment balance; the radial centroid y of the aircraft in the oxy plane is... c =(w1H1-w2H2) / w; The axial center of mass of the aircraft x c The moment obtained by taking moments about oy is the axial centroid x of the spacecraft. c =(w1L1+w2L2-w3L3) / w; The radial centroid c1 is obtained by rotating the aircraft counterclockwise around the x-axis by a certain angle, and the radial centroid c2 is obtained by rotating it clockwise around the x-axis by a certain angle. Points c, c1, and c2 lie on the arc centered at point o. Based on the principle of force and torque balance, the following equation can be obtained: and c1 =(and c 2 +z c 2 ( 0.5 cos(a+b) and c2 =(and c 2 +z c 2 ( 0.5 cos(ab) and c1 / and c2 = cos(a+b) / cos(ab) By rationally designing the rotation angle based on the actual situation of the aircraft, the original angle 'a' at position 'c' can be obtained, and 'z' can be obtained based on the positional relationship. c =y c tana = tana(w1H1-w2H2) / w; where b is the angle of clockwise rotation of the aircraft around the x-axis; H1, H2, L1, L2, and L3 are the vertical distances between the three load cells and the reference axes ox and oy, respectively.

2. The method for measuring the center of mass of a large-span wing aircraft as described in claim 1, characterized in that, After completing one measurement, the aircraft can be rotated 180° around the x-axis and placed on the measuring device. Repeat steps S1-S4, and finally calculate the average value.

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