Aircraft gravity center measuring method and system

Abstract

The invention discloses an aircraft gravity center measuring method and system, and the method comprises the steps: weighing the weights of three landing wheels of an aircraft at the same time on the same horizontal plane, and taking the sum of the weights of the three landing wheels as the total weight of the aircraft; then selecting a datum point in front of an aircraft nose and a plane perpendicular to an aircraft route as a datum plane, and taking the aircraft route as an X-axis forward direction to establish a space rectangular coordinate; a first horizontal measuring point is taken at the rear end of a rear landing gear axle on an aircraft construction horizontal line, and a second horizontal measuring point is taken between a front landing gear axle and the rear landing gear axle on the aircraft construction horizontal line; based on the included angle between the airplane construction horizontal line and the ground horizontal line and the theoretical gravity center of the airplane, the distance between the gravity center of the airplane in the X-axis direction and the measurement datum plane is calculated, the gravity center point of the airplane on the X-axis is obtained, the gravity center point of the airplane can be rapidly determined, and the problem that errors are large in the airplane gravity center measurement process in an existing method is effectively solved. The method is suitable for accurate measurement of gravity centers of various types of aircrafts.

Description

Technical Field

[0001] The invention relates to the fields of aircraft design, flight performance and manufacturing, and in particular to an aircraft center of gravity measurement method and system. Background Art

[0002] The center of gravity of an aircraft not only affects the stability and maneuverability of the aircraft, but also affects the flight performance and flight safety. According to the statistics of previous air crash data, the proportion of accidents caused by errors in center of gravity calculation and imbalance of center of gravity is relatively high, which indirectly reflects that the accuracy of the center of gravity calculation of the aircraft is not high and the reliability is insufficient. The center of gravity range is related to the neutral point, maneuvering point and maneuverability of the aircraft. The whole aircraft is weighed and the center of gravity is calculated throughout the entire process of aircraft design, manufacturing, delivery, use, maintenance and repair. Daily maintenance and replacement of parts, material deformation, and even the sedimentation of the fuel system will affect the center of gravity of the aircraft. During the flight, due to different cargo loading positions and fuel consumption, material delivery, ammunition launch, changes in aerodynamic shape, etc., the center of gravity position will change. Therefore, in all possible flight conditions, the center of gravity position of the aircraft should be within the design allowable range.

[0003] There are several situations in which the center of gravity of an aircraft is measured: ① Weighing the aircraft after final assembly and before the first flight; ② The cumulative empty weight change of the aircraft exceeds 0.5% of the empty weight of the aircraft; ③ The forward and backward movement of the center of gravity of the empty aircraft exceeds 0.5% of the average aerodynamic chord length; ④ After major repairs and modifications; ⑤ Regular maintenance weighing of the aircraft. The current methods for measuring the center of gravity of an aircraft mainly include the top weighing method, the suspension method, the moment balance method, and the main buffer strut compression conversion method. The advantages and disadvantages of the above center of gravity measurement methods are analyzed as follows: (1) The top weighing method requires the use of a jack to lift the aircraft to a horizontal level. Due to the objective conditions of existing materials and manufacturing processes, the aircraft body structure cannot be absolutely rigid under stress. When the weighing device is lifted, the body will be deformed, and deformation stress will be generated. This stress cannot be removed during the weighing process, resulting in deviations in the weighing data. This data deviation changes with the strength and weight of the aircraft, causing interference to the test data; (2) The suspension method is only applicable to lightweight small aircraft; (3) The main launch cushion strut compression conversion method has uncertain errors such as landing gear failure; (4) The moment balance method places the aircraft on the weighing equipment via the main landing gear and the nose landing gear. There is no stress caused by structural deformation, and there is no error in the weighing method itself. However, there are defects such as too much measurement data and angles. The data obtained by using conventional level instruments and steel rulers for distance measurement is inaccurate. There have been multiple instances of different measurement data on site. Summary of the invention

[0004] The purpose of the present invention is to provide a method and system for measuring the center of gravity of an aircraft, so as to overcome the problem of large errors in weighing aircraft in the existing methods.

[0005] A method for measuring the center of gravity of an aircraft comprises the following steps: Weigh the weight of the three landing wheels of the aircraft at the same level at the same time, and take the sum of the weights of the three landing wheels as the total weight of the aircraft; A reference point is selected in front of the nose of the aircraft, and the surface of the reference point perpendicular to the aircraft route is taken as the reference plane, and the aircraft route is taken as the positive direction of the X-axis to establish the spatial rectangular coordinates; the first horizontal measurement point is taken at the rear end of the rear landing gear axle on the aircraft structural horizontal line, and the second horizontal measurement point is taken between the front landing gear axle and the rear landing gear axle on the aircraft structural horizontal line. Based on the angle between the aircraft structural horizontal line and the ground horizontal line, the theoretical center of gravity of the aircraft, the distance from the center of gravity of the aircraft in the X-axis direction to the measuring reference plane and the total weight of the aircraft are calculated, and the center of gravity of the aircraft on the X-axis line is calculated.

[0006] Preferably, a laser tracker is used to sequentially measure a plurality of common points set around the aircraft, and the coordinates of each common point are obtained as the measurement nominal point, and then the acquired nominal points are measured in sequence again, and the data obtained are used as the measurement combination point, and each nominal point and the measurement combination point are selected for best fitting transformation to complete the establishment of the common coordinate system, and the projection of the set position of the front of the nose on the ground is selected as the reference line perpendicular to the fuselage, and the plane passing through the reference line and perpendicular to the ground is used as the reference plane, and the heading is taken as the positive direction of the X-axis to establish a spatial rectangular coordinate system.

[0007] Preferably, an electronic platform scale is used to obtain the weight of each landing gear axle of the aircraft.

[0008] Preferably, the weight data of the aircraft weighed this time can be obtained by obtaining the weighing data of three electronic scales respectively, and the formula is as follows:

[0009] In the formula, The actual measurement of the aircraft's air and space weight; When weighing the aircraft, the left main landing gear wheel is weighed; When weighing the aircraft, the right main landing gear wheel is weighed; When weighing an aircraft, weigh the front landing gear on the wheels.

[0010] Preferably, the plane where the reference point is perpendicular to the aircraft route is taken as the reference plane, and the aircraft route is taken as the positive direction of the X-axis to establish the spatial rectangular coordinates; a first horizontal measurement point is taken at the rear end of the rear landing gear axle on the aircraft structural horizontal line, and a second horizontal measurement point is taken between the front landing gear axle and the rear landing gear axle on the aircraft structural horizontal line. Based on the angle between the aircraft structural horizontal line and the ground horizontal line and the theoretical center of gravity of the aircraft, the distance from the center of gravity of the aircraft in the X-axis direction to the measurement reference plane is calculated, thereby obtaining the center of gravity of the aircraft on the X-axis line, which is specifically calculated by the following formula:

[0011] In the formula, is the distance from the left main landing gear axle to the front landing gear axle; is the distance from the right main landing gear axle to the front landing gear axle; is the distance between the theoretical center of gravity of the aircraft and the construction horizontal plane; Set the starting surface projection distance for the second measurement point of the aircraft; It is the distance from the center of gravity of the aircraft to the measurement reference plane in the X-axis direction.

[0012] Preferably, the angle between the aircraft structure horizontal line and the ground horizontal line is To obtain it, follow these steps:

[0013]

[0014] In the formula, is the height of the first horizontal measuring point; The height of the second horizontal measurement point of the aircraft; is the height difference between the first and second horizontal measuring points; L is the projection distance between the first horizontal measuring point and the second horizontal measuring point on the ground horizontal line.

[0015] Preferably, according to the position of the center of gravity of the aircraft on the X-axis and the average aerodynamic chord length of the aircraft obtained by the above method, the ratio of the distance between the measured center of gravity projection of the aircraft and the leading edge of the average aerodynamic chord length and the average aerodynamic chord length is obtained; specifically, it is obtained by the following formula:

[0016] In the formula, The weight of missing or extra parts during the actual measurement of the aircraft; The X-axis position of the missing or over-equipped parts of the aircraft; is the distance between the measured center of gravity projection and the leading edge of the mean aerodynamic chord length; MAC is the mean aerodynamic chord length of the aircraft; It is the ratio of the distance between the leading edge of the aircraft's measured center of gravity projection and the mean aerodynamic chord length to the mean aerodynamic chord length.

[0017] An aircraft center of gravity measurement system includes a data acquisition module and a center of gravity calculation module; The data acquisition module is used to weigh the weight of the three landing wheels of the aircraft at the same level, and the sum of the weights of the three landing wheels is taken as the total weight of the aircraft; The center of gravity calculation module selects a reference point in front of the aircraft nose, takes the surface of the reference point perpendicular to the aircraft route as the reference plane, takes the aircraft route as the positive direction of the X-axis to establish the spatial rectangular coordinates; takes the first horizontal measurement point at the rear end of the rear landing gear axle on the aircraft structural horizontal line, takes the second horizontal measurement point between the front landing gear axle and the rear landing gear axle on the aircraft structural horizontal line, calculates the distance from the center of gravity of the aircraft in the X-axis direction to the measurement reference plane and the total weight of the aircraft based on the angle between the aircraft structural horizontal line and the ground horizontal line, and the theoretical center of gravity of the aircraft, and calculates the center of gravity of the aircraft on the X-axis line.

[0018] Preferably, a laser tracker is used to sequentially measure a plurality of common points set around the aircraft, and the coordinates of each common point are obtained as the measurement nominal point, and then the acquired nominal points are measured in sequence again, and the data obtained are used as the measurement combination point, and each nominal point and the measurement combination point are selected for best fitting transformation to complete the establishment of the common coordinate system, and the projection of the set position of the front of the nose on the ground is selected as the reference line perpendicular to the fuselage, and the plane passing through the reference line and perpendicular to the ground is used as the reference plane, and the heading is taken as the positive direction of the X-axis to establish a spatial rectangular coordinate system.

[0019] Preferably, the data acquisition module uses an electronic platform scale to obtain the weight of each landing gear axle of the aircraft.

[0020] Compared with the prior art, the present invention has the following beneficial technical effects: The invention provides a method for measuring the center of gravity of an aircraft. The method comprises the following steps: weighing the weights of three landing wheels of an aircraft at the same time on the same horizontal plane, taking the sum of the weights of the three landing wheels as the total weight of the aircraft; then selecting a reference point in front of the nose of the aircraft, taking a surface of the reference point perpendicular to the flight path of the aircraft as the reference plane, taking the flight path of the aircraft as the positive direction of the X-axis to establish a spatial rectangular coordinate; taking a first horizontal measurement point located at the rear end of a rear landing gear axle on a structural horizontal line of the aircraft, taking a second horizontal measurement point located between a front landing gear axle and a rear landing gear axle on the structural horizontal line of the aircraft, calculating the distance from the center of gravity of the aircraft to the measurement reference plane in the X-axis direction and the total weight of the aircraft based on the angle between the structural horizontal line of the aircraft and the horizontal line of the ground, and calculating the center of gravity of the aircraft on the X-axis line, thereby quickly determining the center of gravity of the aircraft, effectively solving the problem of large error in the process of measuring the center of gravity of the aircraft in the existing method, and the invention can be applied to the accurate measurement of the center of gravity of various aircraft models. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0022] Figure 1 Schematic diagram of the aircraft center of gravity measurement principle in an embodiment of the present invention.

[0023] Figure 2 This is a schematic diagram of the distance measurement principle of the laser tracker in an embodiment of the present invention.

[0024] In the figure, 5 is the second measuring point; 6 is the first measuring point; 7 is the axis of the left main landing gear axle; 8 is the axis of the right landing gear axle; 9 is the axis of the front landing gear axle; 10 is the measured center of gravity of the aircraft. DETAILED DESCRIPTION

[0025] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0026] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0027] like Figure 1 , Figure 2 As shown, the present invention provides a method for measuring the center of gravity of an aircraft to achieve high-precision measurement of the center of gravity and solve the problem of large errors in the process of measuring the center of gravity of the aircraft. The method specifically includes the following steps: Set up three weighing platforms at the same level; place the three landing gear wheels of the aircraft on a horizontal weighing platform respectively, read the weight data of the three horizontal weighing platforms respectively, and take the sum of the weight data of the three horizontal weighing platforms as the weight of the aircraft; A reference point is selected in front of the nose of the aircraft, and the surface of the reference point perpendicular to the aircraft route is taken as the reference plane, and the aircraft route is taken as the positive direction of the X-axis to establish the spatial rectangular coordinates; the first horizontal measurement point is taken at the rear end of the rear landing gear axle on the aircraft structural horizontal line, and the second horizontal measurement point is taken between the front landing gear axle and the rear landing gear axle on the aircraft structural horizontal line. Based on the angle between the aircraft structural horizontal line and the ground horizontal line and the theoretical center of gravity of the aircraft, the distance from the center of gravity of the aircraft in the X-axis direction to the measurement reference plane is calculated, thereby obtaining the center of gravity point of the aircraft on the X-axis line.

[0028] In the specific implementation of the present application, an electronic platform scale platform is used to obtain the weight on each landing gear axle of the aircraft. The electronic platform scale of the present application adopts a wireless electronic platform scale, and each electronic platform scale is an independent system. Each electronic platform scale provides multiple independent components that work together to provide repeatable, highly accurate portable weighing capabilities for aircraft of different types and sizes. The table of the electronic platform scale is made of aircraft-grade anodized aluminum, which is light, sturdy and durable.

[0029] During weighing, a tractor is used to tow the aircraft to the weighing platform; during the towing process, the tractor is used to adjust the aircraft weighing position. After moving to the position, the wheel chocks are used to limit the position of the aircraft tires to prevent risks and errors caused by aircraft movement. Tractor: used to tow the aircraft and adjust the aircraft weighing position. Wheel chocks: After the aircraft is towed to the position, the aircraft tires are limited to prevent risks and errors caused by aircraft movement.

[0030] In one embodiment of the present application, three electronic platform scales, one tractor, and a plurality of wheel block fixing fixtures are used to fix and weigh the aircraft. The weighing data of the three electronic platform scales are obtained respectively, and the weight data of the aircraft weighed this time can be calculated. The formula is as follows:

[0031] In the formula, The actual measurement of the aircraft's air and space weight; When weighing the aircraft, the left main landing gear wheel is weighed; When weighing the aircraft, the right main landing gear wheel is weighed; When weighing an aircraft, weigh the front landing gear on the wheels.

[0032] During the measurement of the center of gravity of an aircraft, in order to ensure its measurement accuracy, it is necessary to ensure that the measurement environment is in a hangar or factory building with no wind, vibration, or magnetic field.

[0033] When weighing, ensure that all the control surfaces of the aircraft are in neutral position, and the doors, spoilers, and covers are closed. At the same time, the brakes are released, and the landing gear tires and buffers are inflated according to the design pressure requirements, so that the aircraft is always in a rigid support state.

[0034] Fire prevention and anti-skid safety measures should be taken during weighing, such as adding wheel chocks and bracket protection, to prevent the aircraft from sliding off the scale or tipping over during weighing.

[0035] The plane where the reference point is perpendicular to the aircraft route is taken as the reference plane, and the aircraft route is taken as the positive direction of the X-axis to establish the spatial rectangular coordinates; the first horizontal measurement point is taken at the rear end of the rear landing gear axle on the aircraft structural horizontal line, and the second horizontal measurement point is taken between the front landing gear axle and the rear landing gear axle on the aircraft structural horizontal line. Based on the angle between the aircraft structural horizontal line and the ground horizontal line and the theoretical center of gravity of the aircraft, the distance from the center of gravity of the aircraft in the X-axis direction to the measurement reference plane is calculated, thereby obtaining the center of gravity of the aircraft on the X-axis line, which is specifically calculated by the following formula:

[0036] In the formula, is the distance from the left main landing gear axle to the front landing gear axle; is the distance from the right main landing gear axle to the front landing gear axle; is the distance between the theoretical center of gravity of the aircraft and the construction horizontal plane; Set the starting surface projection distance for the second measurement point of the aircraft; The distance from the center of gravity of the aircraft to the measurement reference plane in the X-axis direction;

[0037]

[0038] In the formula, is the height of the first horizontal measuring point; The height of the second horizontal measurement point of the aircraft; is the height difference between the first and second horizontal measuring points; L is the projection distance between the first horizontal measuring point and the second horizontal measuring point on the ground horizontal line; The angle between the aircraft construction horizontal line and the ground horizontal line.

[0039] Laser tracker: Laser tracking measurement includes laser tracking head, controller, user computer, reflector and environmental sensor. The laser tracker measures the distance between the target mirror and the tracking head based on the principle of laser interference, and measures the angle between the target mirror and the tracking head through the angle measuring sensors on the pitch axis and yaw axis of the tracking head, and then calculates the three-dimensional coordinates of the position of the target mirror in the laser tracker coordinate system. These measurements can collect data at a measurement rate of up to 3000 times per second. By locating each measurement point of the aircraft, a spatial rectangular coordinate system is established to measure the data of the aircraft. The air cavity and air disturbance at different temperatures will affect the direction of the laser beam. The thermal effect of the heat source near the tracker will reduce the measurement accuracy of the instrument. In precise measurement, the laser tracker should be used in the laser beam propagation medium, that is, air, with uniform properties, temperature of 0℃~40℃, relative humidity ≤95%, and windless conditions on site to reduce the error caused by laser refraction. Before measurement, the laser tracker needs to be preheated in the measurement environment for at least 1-2 hours to adapt to the environmental conditions.

[0040] During the measurement process, multiple force sensors are used to support the aircraft body in a balanced state to determine the magnitude of the force at each support point. The direction of the force is determined according to the direction of the torque (counterclockwise or clockwise), and the position of the line of action of each support point is determined by measurement. The support point line of action data is measured using a laser tracker. The laser is reflected back from the target mirror at the target position and interferes with another laser. According to the principle of interference, the distance from the laser tracking head to the target mirror can be obtained. According to the angle encoders on the two axes of the laser tracking head, the pitch angle and azimuth angle of the target position relative to the laser tracking head can be obtained. According to the distance and angle between the laser tracker probe and the target position, the rectangular coordinates of the target position in the laser tracker coordinate system can be calculated.

[0041] According to the position of the center of gravity of the aircraft on the X-axis and the average aerodynamic chord length of the aircraft obtained by the above method, the ratio of the distance between the measured center of gravity projection of the aircraft and the leading edge of the average aerodynamic chord length and the average aerodynamic chord length is obtained; specifically, it is obtained by the following formula:

[0042] In the formula, The weight of missing or extra parts during the actual measurement of the aircraft; The X-axis position of the missing or over-equipped parts of the aircraft; It is the distance between the measured center of gravity projection and the leading edge of the mean aerodynamic chord, which is determined by the geometric shape of the aircraft wing; MAC is the mean aerodynamic chord of the aircraft; It is the ratio of the distance between the leading edge of the aircraft's measured center of gravity projection and the mean aerodynamic chord length to the mean aerodynamic chord length.

[0043] Specifically, by repeatedly installing multiple different parts on the aircraft, the weight of the missing parts and the extra parts on the aircraft are obtained. , and at the same time obtain the position of the aircraft's missing or extra parts on the X-axis; obtain the total weight of the aircraft's missing or extra parts ,calculate It is the ratio of the distance between the leading edge of the aircraft's measured center of gravity projection and the mean aerodynamic chord length to the mean aerodynamic chord length.

[0044] The present invention uses a laser tracker to locate the measurement point data, which greatly improves the accuracy compared with the traditional level and plumb method. While maintaining an accuracy of 70-100um, it can perform 360-degree spatial measurement around the measured object. The applicable space is very large. After the system configuration is completed, multiple users can use it multiple times at the same time to improve the measurement efficiency. At the same time, an aircraft data file can be established to facilitate the horizontal comparison of the aircraft's weight, wheelbase and other data from manufacturing to maintenance. This method does not involve lifting and leveling the aircraft, and does not require a jack or a large ground pump. It has lower requirements for aircraft manufacturing units or airport plants, and is more universal while being more cost-effective.

[0045] Before weighing an aircraft, it is necessary to inspect the aircraft according to the aircraft weighing technical requirements to ensure that the aircraft weighing process meets the weighing technical requirements, otherwise the weighed weight and calculated center of gravity position will be inaccurate. The specific weighing technical requirements are as follows: Aircraft weighing should be carried out in a hangar or factory building with a flat ground, no wind and no vibration; Before weighing, the actual installation status of the aircraft should be checked according to the aircraft configuration documents to ensure that the aircraft is fully assembled, without missing items or excess items. Missing or over-installed items must be recorded in a timely manner (including their weight and center of gravity position); Before weighing, ensure that all control surfaces of the aircraft are in neutral position, and doors, spoilers, covers, etc. are closed; The brakes are released, and the landing gear tires and buffers are inflated according to the design pressure requirements, so that the aircraft is always in a rigid support state; Fire prevention and anti-skid safety measures should be taken during weighing, such as adding wheel chocks and bracket protection, to prevent the aircraft from sliding off the scale or tipping over during weighing; The accuracy of the electronic platform scale used for weighing should not be less than ±1%, and the range of the weight to be weighed should be around 2 / 3 of the maximum range of the scale; All measuring instruments and equipment should be within the validity period of calibration and marked with a certification mark.

[0046] The present invention calculates the center of gravity of the aircraft by calculation. Therefore, during the aircraft weighing process, it is necessary to measure the distances from the front wheel center and the main wheel center to the reference plane to provide data for the calculation of the center of gravity. A point at a fixed distance from the front of the nose is selected, and a plane perpendicular to the ground is drawn along the projection line of the point on the ground as the reference plane to facilitate the calculation of the center of gravity. The specific measurement steps are as follows: Place three electronic scales of the same height in front of the front and main wheels of the aircraft, ensuring that the front and rear distances between each electronic scale and the wheels are consistent. Place the base in an area with a wide field of vision and level ground, install the laser tracking device, and start preheating. Place the wheel chock on the table of the electronic platform scale, and then set the electronic platform scale to zero; Use a tractor to tow the aircraft wheels to the middle position of the electronic scale and remove the towing rod; Take readings on the nose landing gear wheels and the left and right main landing gear wheels; Use towing equipment to move the aircraft and remove the electronic scale under the wheels.

[0047] System initialization. After connecting at least two laser trackers to the host computer through a switch, assign a different IP address to each laser tracker. After each laser tracker is successfully connected to the host computer program, initialization is completed.

[0048] At least 7 target balls are evenly arranged along the heading on the ground as common points for two laser trackers to establish the same coordinate system. First, use a laser tracker to measure each common point in sequence, and obtain the coordinates of each common point as the measurement nominal point. Then use another laser tracker to measure the nominal point in sequence, and the obtained data is used as the measurement combination point. Select each nominal point and the combination point for best fitting transformation to complete the establishment of the common coordinate system. Select a point at a fixed distance from the front of the nose to project on the ground, and make a reference line perpendicular to the fuselage. The plane passing through the reference line and perpendicular to the ground is used as the reference plane. The heading is taken as the positive direction of the X-axis to establish a spatial rectangular coordinate system.

[0049] Set a common point target ball as the "bird's nest", and place the handheld trigger detector at the "bird's nest" position for "homing" and "alignment", initialize the test data, and move the handheld trigger detector to the coordinates of the second horizontal measurement point and the first horizontal measurement point.

[0050] The front landing gear axle and the main landing gear axle are located by fitting the cylindrical positioning method. A handheld trigger detector is used to place measuring points at three different positions on the outer ring of the landing gear axle. Fitting is performed based on the coordinates of the three points to determine the circular plane. Similarly, the circular plane on the other side of the wheel is measured to determine the midpoint of the coaxial line connecting the two circles as the coordinate position of the wheel. Similarly, the positions of the other two landing gear wheels are measured. The projection position of each measuring point is made, the measurement data is output, and the time, model, and flight number are marked as the weighing file of the aircraft.

[0051] The present invention supports the aircraft body in a balanced state through multiple force sensors to determine the magnitude of the force at each support point. The support point action line data is measured using a laser tracker. According to the distance and angle between the laser tracker probe and the target position, the rectangular coordinates of the target position in the laser tracker coordinate system can be calculated. High-precision measurement of weight and center of gravity is achieved, solving the problem of large errors in the measurement of aircraft weight and center of gravity.

Claims

1. A method for measuring the center of gravity of an aircraft, characterized in that: The following steps are involved: Weigh the weight of the three landing wheels of the aircraft at the same level at the same time, and take the sum of the weights of the three landing wheels as the total weight of the aircraft; A reference point is selected in front of the nose of the aircraft, and the surface of the reference point perpendicular to the aircraft route is taken as the reference plane, and the aircraft route is taken as the positive direction of the X-axis to establish the spatial rectangular coordinates; the first horizontal measurement point is taken at the rear end of the rear landing gear axle on the aircraft structural horizontal line, and the second horizontal measurement point is taken between the front landing gear axle and the rear landing gear axle on the aircraft structural horizontal line. Based on the angle between the aircraft structural horizontal line and the ground horizontal line, the theoretical center of gravity of the aircraft, the distance from the center of gravity of the aircraft in the X-axis direction to the measuring reference plane and the total weight of the aircraft are calculated, and the center of gravity of the aircraft on the X-axis line is calculated.

2. The method for measuring the center of gravity of an aircraft according to claim 1, characterized in that: A laser tracker is used to measure multiple common points set around the aircraft in sequence, and the coordinates of each common point are obtained as the measurement nominal point. The acquired nominal points are then measured in sequence and the obtained data are used as the measurement combination point. Each nominal point and the measurement combination point are selected for the best fitting transformation to complete the establishment of the public coordinate system. The projection of the set position of the front of the nose on the ground is selected as the reference line perpendicular to the fuselage. The plane passing through the reference line and perpendicular to the ground is used as the reference plane. The heading is taken as the positive direction of the X-axis to establish a spatial rectangular coordinate system.

3. The method for measuring the center of gravity of an aircraft according to claim 1, characterized in that: An electronic platform scale is used to obtain the weight of each landing gear axle of the aircraft.

4. The method for measuring the center of gravity of an aircraft according to claim 3, characterized in that: By obtaining the weighing data of the three electronic scales respectively, the weight data of the aircraft weighed this time can be calculated. The formula is as follows: In the formula, The actual measurement of the aircraft's air and space weight; When weighing the aircraft, the left main landing gear wheel is weighed; When weighing the aircraft, the right main landing gear wheel is weighed; When weighing an aircraft, weigh the front landing gear on the wheels.

5. The method for measuring the center of gravity of an aircraft according to claim 1, characterized in that: The plane where the reference point is perpendicular to the aircraft route is taken as the reference plane, and the aircraft route is taken as the positive direction of the X-axis to establish the spatial rectangular coordinates; the first horizontal measurement point is taken at the rear end of the rear landing gear axle on the aircraft structural horizontal line, and the second horizontal measurement point is taken between the front landing gear axle and the rear landing gear axle on the aircraft structural horizontal line. Based on the angle between the aircraft structural horizontal line and the ground horizontal line and the theoretical center of gravity of the aircraft, the distance from the center of gravity of the aircraft in the X-axis direction to the measurement reference plane is calculated, thereby obtaining the center of gravity of the aircraft on the X-axis line, which is specifically calculated by the following formula: In the formula, is the distance from the left main landing gear axle to the front landing gear axle; is the distance from the right main landing gear axle to the front landing gear axle; is the distance between the theoretical center of gravity of the aircraft and the construction horizontal plane; Set the starting surface projection distance for the second measurement point of the aircraft; It is the distance from the center of gravity of the aircraft to the measurement reference plane in the X-axis direction.

6. The method for measuring the center of gravity of an aircraft according to claim 5, characterized in that: The angle between the aircraft structure horizontal line and the ground horizontal line To obtain it, follow these steps: In the formula, is the height of the first horizontal measuring point; The height of the second horizontal measurement point of the aircraft; is the height difference between the first and second horizontal measuring points; L is the projection distance between the first horizontal measuring point and the second horizontal measuring point on the ground horizontal line.

7. The method for measuring the center of gravity of an aircraft according to claim 1, characterized in that: According to the position of the center of gravity of the aircraft on the X-axis and the average aerodynamic chord length of the aircraft obtained by the above method, the ratio of the distance between the measured center of gravity projection of the aircraft and the leading edge of the average aerodynamic chord length and the average aerodynamic chord length is obtained; specifically, it is obtained by the following formula: In the formula, The weight of missing or extra parts during the actual measurement of the aircraft; The X-axis position of the missing or over-equipped parts of the aircraft; is the distance between the measured center of gravity projection and the leading edge of the mean aerodynamic chord length; MAC is the mean aerodynamic chord length of the aircraft; It is the ratio of the distance between the leading edge of the aircraft's measured center of gravity projection and the mean aerodynamic chord length to the mean aerodynamic chord length.

8. An aircraft center of gravity measurement system, characterized in that: Including data acquisition module and center of gravity calculation module; The data acquisition module is used to weigh the weight of the three landing wheels of the aircraft at the same level, and the sum of the weights of the three landing wheels is taken as the total weight of the aircraft; The center of gravity calculation module selects a reference point in front of the aircraft nose, takes the surface of the reference point perpendicular to the aircraft route as the reference plane, takes the aircraft route as the positive direction of the X-axis to establish the spatial rectangular coordinates; takes the first horizontal measurement point at the rear end of the rear landing gear axle on the aircraft structural horizontal line, takes the second horizontal measurement point between the front landing gear axle and the rear landing gear axle on the aircraft structural horizontal line, calculates the distance from the center of gravity of the aircraft in the X-axis direction to the measurement reference plane and the total weight of the aircraft based on the angle between the aircraft structural horizontal line and the ground horizontal line, and the theoretical center of gravity of the aircraft, and calculates the center of gravity of the aircraft on the X-axis line.

9. The aircraft center of gravity measurement system according to claim 8, characterized in that: A laser tracker is used to measure multiple common points set around the aircraft in sequence, and the coordinates of each common point are obtained as the measurement nominal point. The acquired nominal points are then measured in sequence and the obtained data are used as the measurement combination point. Each nominal point and the measurement combination point are selected for the best fitting transformation to complete the establishment of the public coordinate system. The projection of the set position of the front of the nose on the ground is selected as the reference line perpendicular to the fuselage. The plane passing through the reference line and perpendicular to the ground is used as the reference plane. The heading is taken as the positive direction of the X-axis to establish a spatial rectangular coordinate system.

10. The aircraft center of gravity measurement system according to claim 8, characterized in that: The data acquisition module uses an electronic scale platform to obtain the weight of each landing gear axle of the aircraft.

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