Aircraft center of gravity measurement method and system

Abstract

The present invention discloses a method and system for measuring the center of gravity of an aircraft. The method comprises the following steps: simultaneously weighing the weights of three landing wheels of an aircraft 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 aircraft nose and a surface perpendicular to the aircraft flight path as the reference plane, taking the aircraft flight path as the positive direction of the X-axis to establish spatial rectangular coordinates; taking a first horizontal measurement point on the aircraft structural horizontal line at the rear end of a rear landing gear axle, and taking a second horizontal measurement point on the aircraft structural horizontal line between the front landing gear axle and the rear landing gear axle; calculating the distance from the center of gravity of the aircraft to the measurement reference plane in the X-axis direction 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 obtaining the center of gravity of the aircraft on the X-axis line. The method can quickly determine the center of gravity of the aircraft, effectively solving the problem of large errors in the process of measuring the center of gravity of the aircraft in the existing methods, and the method is applicable to the accurate measurement of the center of gravity of various aircraft models.

Description

Technical Field

[0001] The present 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] An aircraft's center of gravity not only affects its stability and maneuverability, but also its flight performance and safety. Historical air crash statistics show a high proportion of accidents caused by errors in center of gravity calculation and imbalance, indirectly reflecting the low accuracy and reliability of aircraft center of gravity calculations. The center of gravity range is related to the aircraft's neutral point, maneuverability, and maneuverability. Throughout the entire aircraft design, manufacturing, delivery, operation, maintenance, and repair process, aircraft weighing and center of gravity calculation are consistently performed. Routine maintenance and component replacement, material deformation, and even fuel system sedimentation can affect the aircraft's center of gravity. During flight, the center of gravity can vary due to differences in cargo loading positions, fuel consumption, material delivery, ammunition launch, and changes in aerodynamic shape. Therefore, under all possible flight conditions, the aircraft's center of gravity should be within the design's allowable range.

[0003] There are currently several situations in which the center of gravity of an aircraft is measured: 1. Weighing the aircraft after final assembly and before its first flight; 2. The cumulative empty weight change of the aircraft exceeds 0.5% of the aircraft's empty weight; 3. The forward and backward movement of the empty aircraft's center of gravity exceeds 0.5% of the average aerodynamic chord length; 4. After major repairs and modifications; 5. Regular aircraft maintenance weighing. Currently, there are three main methods for measuring the center of gravity of an aircraft: the top weighing method, the suspension method, the moment balance method, and the main suspension strut compression conversion method. The advantages and disadvantages of the above center of gravity measurement methods are analyzed as follows:

[0004] (1) The top weighing method requires the use of a jack to lift the aircraft to a horizontal position. Due to the objective conditions of existing materials and manufacturing processes, the aircraft body structure cannot ensure absolute rigidity when subjected to force. When the weighing device is lifted, the body will deform, and then generate deformation stress. This stress cannot be relieved during the weighing process, resulting in deviations in the weighing data. This data deviation changes with the changes in aircraft strength and weight, causing interference to the test data.

[0005] (2) The suspension method is only applicable to lightweight small aircraft;

[0006] (3) The main launch cushion strut compression conversion method has uncertain errors such as landing gear failure;

[0007] (4) The moment balance method places the aircraft on the weighing equipment through 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 distance measurement method using conventional levels and steel rulers is inaccurate. There have been many cases where the measurement data are different on site. Summary of the Invention

[0008] 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 existing methods.

[0009] A method for measuring the center of gravity of an aircraft comprises the following steps:

[0010] 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;

[0011] A reference point is selected in front of the aircraft nose, and the surface perpendicular to the aircraft's flight path is used as the reference plane. The aircraft's flight path is taken as the positive direction of the X-axis to establish spatial rectangular coordinates. A first horizontal measurement point is taken on the aircraft's structural horizontal line at the rear end of the rear landing gear axle, and a second horizontal measurement point is taken on the aircraft's structural horizontal line between the front and rear landing gear axles. Based on the angle between the aircraft's structural horizontal line and the ground horizontal line, the theoretical center of gravity of the aircraft, and the calculated distance from the aircraft's center of gravity in the X-axis direction to the measurement reference plane, as well as the aircraft's gross weight, the aircraft's center of gravity on the X-axis is calculated.

[0012] 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. The obtained nominal points are then measured in sequence again, and the data obtained are used as the measurement combination point. Each nominal point and the measurement combination point are selected for best fitting transformation to complete the establishment of the common coordinate system. The projection of the set position of the front 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.

[0013] Preferably, an electronic platform scale is used to obtain the weight of each landing gear axle of the aircraft.

[0014] Preferably, the weight data of the aircraft weighed this time can be obtained by obtaining the weighing data of three electronic scales respectively. The formula is as follows:

[0015]

[0016] Where, 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 wheels.

[0017] Preferably, a plane perpendicular to the aircraft flight path is used as a reference plane, and the aircraft flight path is used as the positive direction of the X-axis to establish a spatial rectangular coordinate; a first horizontal measurement point is taken on the aircraft structural horizontal line at the rear end of the rear landing gear axle, and a second horizontal measurement point is taken on the aircraft structural horizontal line between the front landing gear axle and the rear landing gear axle. 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. Specifically, the calculation is performed using the following formula:

[0018]

[0019] Where, is the distance from the left main landing gear axle to the nose landing gear axle; is the distance from the right main landing gear axle to the nose landing gear axle; is the distance between the theoretical center of gravity of the aircraft and the construction horizontal plane; Set the projection distance of the starting surface 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.

[0020] Preferably, the angle between the aircraft structure horizontal line and the ground horizontal line is To obtain it, follow these steps:

[0021]

[0022]

[0023] Where, 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 and second horizontal measuring points on the ground horizontal line.

[0024] Preferably, based on 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 to the average aerodynamic chord length is obtained; specifically, it is obtained by the following formula:

[0025]

[0026] Where, The weight of missing or extra parts during the actual measurement of the aircraft; The X-axis position of the missing multi-installed parts of the aircraft; is the distance between the measured center of gravity projection and the leading edge of the mean aerodynamic chord; MAC is the mean aerodynamic chord of the aircraft; It is the ratio of the distance between the aircraft's measured center of gravity projection and the leading edge of the mean aerodynamic chord length to the mean aerodynamic chord length.

[0027] An aircraft center of gravity measurement system includes a data acquisition module and a center of gravity calculation module;

[0028] The data acquisition module is used to simultaneously weigh the weight of the three landing wheels of the aircraft on the same horizontal plane, and the sum of the weights on the three landing wheels is taken as the total weight of the aircraft;

[0029] The center of gravity calculation module selects a reference point in front of the aircraft nose, takes the surface perpendicular to the aircraft route as the reference plane, and takes the aircraft route as the positive direction of the X-axis to establish a spatial rectangular coordinate; takes a first horizontal measurement point on the aircraft structural horizontal line at the rear end of the rear landing gear axle, and takes a second horizontal measurement point on the aircraft structural horizontal line between the front landing gear axle and the rear landing gear axle; 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 measurement reference plane and the gross weight of the aircraft are calculated, and the center of gravity of the aircraft on the X-axis is calculated.

[0030] 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. The obtained nominal points are then measured in sequence again, and the data obtained are used as the measurement combination point. Each nominal point and the measurement combination point are selected for best fitting transformation to complete the establishment of the common coordinate system. The projection of the set position of the front 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.

[0031] Preferably, the data acquisition module uses an electronic scale platform to obtain the weight of each landing gear axle of the aircraft.

[0032] Compared with the prior art, the present invention has the following beneficial technical effects:

[0033] The present invention provides a method for measuring the center of gravity of an aircraft. The method comprises the following steps: simultaneously weighing the weights of three landing wheels of the aircraft on the same horizontal plane, taking the sum of the weights of the three landing wheels as the gross weight of the aircraft; selecting a reference point in front of the nose of the aircraft, taking a plane perpendicular to the aircraft flight path as the reference plane, and taking the aircraft flight path as the positive direction of the X-axis to establish a spatial rectangular coordinate; taking a first horizontal measurement point on the aircraft structural horizontal line at the rear end of a rear landing gear axle, and taking a second horizontal measurement point on the aircraft structural horizontal line between the front landing gear axle and the rear landing gear axle; calculating the distance from the center of gravity of the aircraft to the measurement reference plane in the X-axis direction and the gross 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 calculating the center of gravity of the aircraft on the X-axis line. The method can quickly determine the center of gravity of the aircraft, effectively solving the problem of large errors in the process of measuring the center of gravity of the aircraft in the existing method, and the method can be applied to the accurate measurement of the center of gravity of various aircraft models. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments or descriptions of the prior art. 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 any creative work.

[0035] Figure 1 Schematic diagram of the aircraft center of gravity measurement principle in an embodiment of the present invention.

[0036] Figure 2 This is a diagram showing the distance measurement principle of a laser tracker in an embodiment of the present invention.

[0037] 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

[0038] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions 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 embodiments described 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 making creative efforts should fall within the scope of protection of the present invention.

[0039] It should be noted that the terms "first", "second", etc. in the description 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 numbers 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 clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0040] 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:

[0041] 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;

[0042] A reference point is selected in front of the aircraft nose, and the surface perpendicular to the aircraft flight path is used as the reference plane. The aircraft flight path is taken as the positive direction of the X-axis to establish the spatial rectangular coordinates. The first horizontal measurement point is taken on the aircraft structural horizontal line at the rear end of the rear landing gear axle, and the second horizontal measurement point is taken on the aircraft structural horizontal line between the front landing gear axle and the rear landing gear axle. Based on the angle between the aircraft structural horizontal line and the ground horizontal line and the aircraft's theoretical center of gravity, the distance from the aircraft's center of gravity in the X-axis direction to the measurement reference plane is calculated, thereby obtaining the aircraft's center of gravity on the X-axis.

[0043] In this embodiment, an electronic platform scale platform is used to individually measure the weight on each aircraft landing gear axle. This electronic platform scale utilizes wireless electronic platform scales, each of which is a standalone system. Each platform scale provides multiple independent components working together to deliver repeatable, highly accurate portable weighing capabilities for aircraft of varying types and sizes. The platform scale's surface is constructed from aircraft-grade anodized aluminum, ensuring lightweight, durability, and strength.

[0044] During weighing, a tractor is used to tow the aircraft onto the weighing platform. During the towing process, the tractor adjusts the aircraft's weighing position. Once in position, chocks are used to hold the aircraft's tires in place to prevent movement and potential errors. The tractor is used to tow the aircraft and adjust its weighing position. Chocks are used to hold the aircraft's tires in place after the aircraft is towed into position to prevent movement and potential errors.

[0045] In one embodiment of the present application, three electronic platform scales, one tractor, and multiple wheel chock fixing fixtures are used to fix and weigh the aircraft. The weight data of the aircraft weighed this time can be obtained by obtaining the weighing data of the three electronic platform scales respectively. The formula is as follows:

[0046]

[0047] Where, 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 wheels.

[0048] To ensure accuracy during the measurement of an aircraft's center of gravity, the measurement must be performed in a hangar or factory building with no wind, vibration, or magnetic fields.

[0049] When weighing, ensure that all control surfaces of the aircraft are in neutral position, doors, spoilers, hatches, etc. 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 to ensure that the aircraft is always in a rigid support state.

[0050] Fire prevention and anti-slip 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.

[0051] The plane perpendicular to the aircraft's flight path is used as the reference plane, and the aircraft's flight path is used as the positive direction of the X-axis to establish spatial rectangular coordinates. The first horizontal measurement point is located at the rear end of the rear landing gear axle on the aircraft's structural horizontal line, and the second horizontal measurement point is located between the front landing gear axle and the rear landing gear axle on the aircraft's structural horizontal line. Based on the angle between the aircraft's structural horizontal line and the ground horizontal line and the aircraft's theoretical center of gravity, the distance from the aircraft's center of gravity in the X-axis direction to the measurement reference plane is calculated, thereby obtaining the aircraft's center of gravity on the X-axis. This is specifically calculated using the following formula:

[0052]

[0053] Where, is the distance from the left main landing gear axle to the nose landing gear axle; is the distance from the right main landing gear axle to the nose landing gear axle; is the distance between the theoretical center of gravity of the aircraft and the construction horizontal plane; Set the projection distance of the starting surface for the second measurement point of the aircraft; The distance from the aircraft's center of gravity in the X-axis direction to the measurement reference plane;

[0054]

[0055]

[0056] Where, 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 and second horizontal measuring points on the ground horizontal line; The angle between the aircraft construction horizontal line and the ground horizontal line.

[0057] Laser tracker: Laser tracking measurement consists of a laser tracking head, controller, user computer, reflector, and environmental sensors. The laser tracker uses the principle of laser interferometry to measure the distance between the target scope and the tracking head. Angulation sensors on the tracker's pitch and yaw axes measure the angle between the two, and then calculate the three-dimensional coordinates of the target scope's position in the laser tracker's coordinate system. These measurements can acquire data at a rate of up to 3,000 times per second. By locating each measurement point on the aircraft and establishing a spatial rectangular coordinate system, data is measured. Air cavities and air disturbances at different temperatures can affect the direction of the laser beam. Thermal effects from heat sources near the tracker can reduce measurement accuracy. For precise measurements, the laser tracker must be used in a homogeneous air environment, with a temperature between 0°C and 40°C, a relative humidity of 95% or less, and no wind to minimize errors caused by laser refraction. Before measurement, the laser tracker must be warmed up in the measurement environment for at least 1-2 hours to acclimate to the environmental conditions.

[0058] During the measurement process, multiple force sensors are used to support the aircraft in equilibrium to determine the magnitude of the force at each support point. The direction of the force is determined by the direction of the torque (counterclockwise or clockwise), and the position of the force line of action at each support point is determined through measurement. The support point line of action data is measured using a laser tracker. The laser is reflected by a target mirror at the target location, where it interferes with another laser. Based on the principle of interference, the distance from the laser tracking head to the target mirror can be determined. The angle encoders on the two axes of the laser tracking head can be used to determine the pitch and azimuth angles of the target position relative to the laser tracking head. Based on 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.

[0059] Based on 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 to the average aerodynamic chord length is obtained; specifically, it is obtained by the following formula:

[0060]

[0061] Where, The weight of missing or extra parts during the actual measurement of the aircraft; The X-axis position of the missing multi-installed parts of the aircraft; 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 aircraft's measured center of gravity projection and the leading edge of the mean aerodynamic chord length to the mean aerodynamic chord length.

[0062] Specifically, by repeatedly installing multiple different parts on the aircraft, the weight of the missing parts of the aircraft is 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 aircraft's measured center of gravity projection and the leading edge of the mean aerodynamic chord length to the mean aerodynamic chord length.

[0063] This method uses a laser tracker to locate measurement points, significantly improving accuracy compared to traditional levels and plumb lines. While maintaining an accuracy of 70-100 μm, it can perform 360-degree spatial measurements around the measured object, allowing for wide-ranging applications. Once configured, the system can be used by multiple users simultaneously, improving measurement efficiency. It also creates an aircraft data archive, facilitating cross-sectional comparisons of weight, wheelbase, and other information from manufacturing to maintenance. This method does not require jacking, leveling, or weighing the aircraft, nor does it require jacks or large ground pumps. It has lower requirements for aircraft manufacturers or airport facilities, is less costly, and is more universally applicable.

[0064] 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. Specific weighing technical requirements are as follows:

[0065] Aircraft weighing should be carried out in a hangar or factory with a flat ground, no wind and no vibration;

[0066] Before weighing, the actual assembled state of the aircraft should be checked according to the aircraft configuration documents to ensure that the aircraft is fully assembled with no missing items or excess items. Any missing or over-assembled items must be recorded in a timely manner (including their weight and center of gravity position);

[0067] Before weighing, ensure that all control surfaces of the aircraft are in neutral position, and doors, spoilers, hatches, etc. are closed;

[0068] The brakes are released, and the landing gear tires and buffers are inflated according to the design pressure requirements to keep the aircraft in a rigid support state at all times;

[0069] Fire prevention and anti-slip 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;

[0070] The accuracy of the electronic platform scale used for weighing should be no less than ±1%, and the range of the weight to be weighed should be around 2 / 3 of the maximum range of the scale;

[0071] All measuring instruments and equipment should be within the validity period of calibration and marked with the qualification mark.

[0072] The present invention calculates the center of gravity of an aircraft by calculation. Therefore, during aircraft weighing, the distances from the front and main wheel centers to a reference plane must be measured to provide data for center of gravity calculation. A point at a fixed distance from the front of the aircraft nose is selected, and a plane perpendicular to the ground is drawn along the line projected from that point on the ground as the reference plane to facilitate center of gravity calculation. The specific measurement steps are as follows:

[0073] Place three electronic scales of the same height in front of the aircraft's front and main wheels, ensuring that the distance between each electronic scale and the wheels is consistent. Place the base in an area with a wide field of view and level ground, install the laser tracking device, and start preheating.

[0074] Place the wheel chock on the table of the electronic platform scale, and then set the electronic platform scale to zero;

[0075] Use a towing vehicle to pull the aircraft wheels to the middle position of the electronic scale and remove the towing rod;

[0076] Take readings on the nose landing gear wheel and the left and right main landing gear wheels;

[0077] Use towing equipment to move the aircraft and remove the electronic scale under the wheels.

[0078] 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. Initialization is completed after each laser tracker successfully connects to the host computer program.

[0079] 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 the positive direction of the X-axis to establish a spatial rectangular coordinate system.

[0080] Set a common point target 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.

[0081] The axis of the front landing gear axle and the main landing gear axle are located using the fitting cylinder positioning method. A handheld trigger detector is used to place measurement 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, and the midpoint of the coaxial line connecting the two circles is determined as the coordinate position of the wheel. Similarly, the positions of the other two landing gear wheels are measured; the projection position of each measurement point is determined, the measurement data is output, and the time, model, and flight number are marked as the weighing file of this aircraft.

[0082] The present invention uses multiple force sensors to maintain the aircraft's balance, determining the force at each support point. The support point's line of action data is measured using a laser tracker. Based on the distance and angle between the laser tracker probe and the target position, the target's rectangular coordinates in the laser tracker's coordinate system are calculated. This enables high-precision weight and center of gravity calculations, addressing the issue of large errors in these calculations.

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 aircraft nose, and the surface perpendicular to the aircraft's flight path is used as the reference plane. The aircraft's flight path is taken as the positive direction of the X-axis to establish spatial rectangular coordinates. A first horizontal measurement point is taken on the aircraft's structural horizontal line at the rear end of the rear landing gear axle, and a second horizontal measurement point is taken on the aircraft's structural horizontal line between the front and rear landing gear axles. Based on the angle between the aircraft's structural horizontal line and the ground horizontal line, the theoretical center of gravity of the aircraft, and the calculated distance from the aircraft's center of gravity in the X-axis direction to the measurement reference plane, as well as the aircraft's gross weight, the aircraft's center of gravity on the X-axis is calculated.

2. The method for measuring the center of gravity of an aircraft according to claim 1, wherein: 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 obtained nominal points are then measured in sequence again, and the data obtained are used as the measurement combination point. Each nominal point and the measurement combination point are selected for best fit transformation to complete the establishment of the public coordinate system. The projection of the set position of the front 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, wherein: 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, wherein: By obtaining the weighing data of three electronic scales respectively, the weight data of the aircraft weighed this time can be calculated. The formula is as follows: Where, 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 wheels.

5. The method for measuring the center of gravity of an aircraft according to claim 1, wherein: The plane perpendicular to the aircraft's flight path is used as the reference plane, and the aircraft's flight path is used as the positive direction of the X-axis to establish spatial rectangular coordinates. The first horizontal measurement point is located at the rear end of the rear landing gear axle on the aircraft's structural horizontal line, and the second horizontal measurement point is located between the front landing gear axle and the rear landing gear axle on the aircraft's structural horizontal line. Based on the angle between the aircraft's structural horizontal line and the ground horizontal line and the aircraft's theoretical center of gravity, the distance from the aircraft's center of gravity in the X-axis direction to the measurement reference plane is calculated, thereby obtaining the aircraft's center of gravity on the X-axis. This is specifically calculated using the following formula: Where, is the distance from the left main landing gear axle to the nose landing gear axle; is the distance from the right main landing gear axle to the nose landing gear axle; is the distance between the theoretical center of gravity of the aircraft and the construction horizontal plane; Set the projection distance of the starting surface 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's structural horizontal line and the ground's horizontal line To obtain it, follow these steps: Where, 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 and second horizontal measuring points on the ground horizontal line.

7. The method for measuring the center of gravity of an aircraft according to claim 1, characterized in that: Based on 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 actual center of gravity projection of the aircraft and the leading edge of the average aerodynamic chord length to the average aerodynamic chord length is obtained; specifically, it is obtained by the following formula: Where, The weight of missing or extra parts during the actual measurement of the aircraft; The X-axis position of the missing multi-installed parts of the aircraft; is the distance between the measured center of gravity projection and the leading edge of the mean aerodynamic chord; MAC is the mean aerodynamic chord of the aircraft; It is the ratio of the distance between the aircraft's measured center of gravity projection and the leading edge of 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 simultaneously weigh the weight of the three landing wheels of the aircraft on the same horizontal plane, and the sum of the weights on 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 perpendicular to the aircraft route as the reference plane, and takes the aircraft route as the positive direction of the X-axis to establish a spatial rectangular coordinate; takes a first horizontal measurement point on the aircraft structural horizontal line at the rear end of the rear landing gear axle, and takes a second horizontal measurement point on the aircraft structural horizontal line between the front landing gear axle and the rear landing gear axle; 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 measurement reference plane and the gross weight of the aircraft are calculated, and the center of gravity of the aircraft on the X-axis is calculated.

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 obtained nominal points are then measured in sequence again, and the data obtained are used as the measurement combination point. Each nominal point and the measurement combination point are selected for best fit transformation to complete the establishment of the public coordinate system. The projection of the set position of the front 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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