Aircraft buffer system energy absorption efficiency calculation method based on flight measured data

Abstract

The invention belongs to the technical field of flight tests, and particularly relates to an aircraft buffer system energy absorption efficiency calculation method based on flight measured data, in particular to an aircraft with an undercarriage as a buffer system. Comprising the steps of performing a load calibration test on an undercarriage to obtain test data, and determining a coefficient of a load test model according to the test data; actual measurement data are substituted into the load measurement model, an actual measurement external load is obtained, the actual measurement external load is projected to a ground coordinate system according to the attitude angle of the aircraft, and an actual measurement load under the ground coordinate system is obtained; the actually-measured sensor position, the aircraft attitude and the initial sensor installation position are substituted into the coordinate transformation matrix, and the position of the gravity center of the aircraft under the ground coordinates is obtained; integrating the actually measured load under the ground coordinate system and the position of the center of gravity of the aircraft under the ground coordinate system to obtain energy absorbed by an aircraft buffer system, and calculating the energy absorption efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of flight test, and specifically relates to a method for calculating the energy absorption efficiency of an aircraft buffer system based on actual flight measured data, and relates to a method for calculating the buffer energy absorption efficiency of an aircraft landing gear buffer system, and particularly relates to calculating the energy absorbed by the buffer system and calculating the energy absorption efficiency of the buffer system according to actual measured flight loads, aircraft positions and attitude parameters in a flight test. Background Art

[0002] The aircraft landing gear is the most important buffer component during the aircraft take-off and landing process. It absorbs the impact energy during the take-off and landing process and cushions the impact of the ground, making the aircraft take-off and landing process smoother. At the same time, it reduces the landing load to reduce the structural weight of the aircraft, ensuring the safety of the structure and making the aircraft more economical and practical.

[0003] At present, the cushioning effect of the landing gear is mainly verified through ground drop tests, and the energy absorption efficiency is calculated by calculating the energy absorbed by the landing gear during the drop. However, the drop test cannot truly simulate the horizontal speed of the aircraft and the support stiffness of the landing gear, resulting in differences between the verified cushioning performance and the actual situation.

[0004] How to calculate the energy absorption efficiency of the aircraft landing gear buffer system through measured flight data, so as to verify and evaluate the buffering capacity of the aircraft landing gear buffer system under actual installation conditions and actual usage conditions. Summary of the invention

[0005] Purpose of the invention: To provide a method for calculating the energy absorption efficiency of an aircraft cushioning system based on actual flight measured data, to calculate the energy absorbed by the aircraft landing gear cushioning system and the energy absorption efficiency through actual flight measured data, and to provide support for evaluating the aircraft landing gear cushioning performance through actual flight measured data.

[0006] The technical solution of the present invention is:

[0007] A method for calculating the energy absorption efficiency of an aircraft buffer system based on actual flight data, the method being used for calculating the energy absorption efficiency of an aircraft buffer system under actual flight conditions, the method comprising the following steps:

[0008] Carry out load calibration test on landing gear to obtain test data, and determine the coefficient of load measurement model according to the test data;

[0009] The measured data is brought into the load measurement model to obtain the measured external load, and the measured external load is projected to the ground coordinate system according to the attitude angle of the aircraft to obtain the measured load in the ground coordinate system;

[0010] Substitute the measured sensor position, aircraft attitude and initial sensor installation position into the coordinate transformation matrix to obtain the position of the aircraft's center of gravity in ground coordinates;

[0011] The measured load in the ground coordinate system and the position of the aircraft's center of gravity in the ground coordinate system are integrated to obtain the energy absorbed by the aircraft's buffer system and calculate the energy absorption efficiency.

[0012] Furthermore, a load calibration test is performed on the landing gear to obtain test data, and the coefficients of the load measurement model are determined according to the test data, including:

[0013] Step 1: Install multiple load-measuring strain gauges on the main force transmission channel of the landing gear structure;

[0014] Step 2: Load calibration test: After the landing gear is installed and fixed, the landing gear is subjected to vertical, azimuth, and lateral unidirectional loading and two-way and three-way combined loading under the fixed buffer stroke. The loading load and structural strain data are recorded synchronously during the test; unidirectional loading in each direction must be performed, as well as two-way and three-way combined loading; the buffer fixed stroke includes at least three, named in sequence: s1, s2, s3, s1 <s2<s3;

[0015] Step 3: Substitute the loading load and the structural strain data measured by the load-measuring strain gauge under each stroke into the load-measuring model, and obtain the coefficients of the load-measuring model through linear regression; the coefficients of the load-measuring model for other strokes are obtained through linear difference;

[0016] The load model is:

[0017] F J =Kε ​​(1)

[0018] Linear regression solution formula for load model coefficients:

[0019] K=F J (εε T ) -1 (2)

[0020] In formula (1) and formula (2): F J is the loading load of the load calibration test; K is the load measurement model coefficient; ε is the structural strain measured by the load measurement strain gauge;

[0021] Other trips: the trip is not any of s1, s2, and s3;

[0022] The difference formula of the load model coefficient for other strokes:

[0023]

[0024] In formula (3): s is the buffer stroke; K sis the load model coefficient of stroke s; are the load measurement model coefficients for strokes s1, s2, and s3 respectively.

[0025] Furthermore, the measured data is brought into the load measurement model to obtain the measured external load, and the measured external load is projected to the ground coordinate system according to the attitude angle of the aircraft to obtain the measured load in the ground coordinate system, including:

[0026] Step 4: Before the flight test, install GPS or GNS to measure three-dimensional position and three-dimensional speed, and inertial navigation to measure three-dimensional attitude on the aircraft; on the landing gear, in addition to the strain gauge installed in step 1, a buffer displacement sensor needs to be installed; at the same time, install test equipment to measure and record these parameters on the aircraft;

[0027] Step 5: Flight test: Conduct a landing test flight with a high sinking speed, requiring the pilot to control the aircraft to land at the required sinking speed; during the test, the test equipment collects and records flight data;

[0028] Step 6: Flight load calculation: Substitute the structural strain data and buffer stroke data from the flight data measured in step 5 into the load measurement model in step 3 to obtain the flight measured load F F ;

[0029] F F is a column vector, and the measured heading load F x , lateral load F y and vertical load F z composition:

[0030]

[0031] Step 7: Convert the measured load into the load in the ground coordinate system: Substitute the measured load and aircraft attitude into the conversion formula between the body coordinate system and the ground coordinate system:

[0032] Conversion formula between body coordinate system and ground coordinate system:

[0033]

[0034] P D is a column vector, which consists of three loads in the ground coordinate system, namely, the heading load P x , lateral load P y and vertical load P z composition:

[0035]

[0036] In formula (5), L T-Dis the transformation matrix from the aircraft body axis coordinates to the ground coordinate system, and its calculation formula is:

[0037]

[0038] In formula (6): is the aircraft's yaw angle, θ is the aircraft's pitch angle, and φ is the aircraft's roll angle, which are measured by attitude sensors such as gyroscopes on the aircraft.

[0039] Furthermore, the measured sensor position, aircraft attitude and initial sensor installation position are brought into the coordinate transformation matrix to obtain the position of the aircraft's center of gravity in ground coordinates, including:

[0040] Step 8: Calculate the initial installation angle of the sensor: Get the installation position of the GNS position sensor in the body coordinate system as [x cgq_T y cgq_T z cgq_T ] T , calculate the initial installation angle of the sensor from the installation position;

[0041] The calculation formula for the initial installation angle is:

[0042]

[0043]

[0044] Where: is the initial installation yaw angle of the sensor, θ0 is the initial installation pitch angle of the sensor; cgq_ T.y cgq_ T and z cgq_T They are the heading, lateral and vertical installation positions of the position sensor in the body coordinate system;

[0045] Step 9: Calculate the coordinate transformation matrix of the sensor: Substitute the initial installation angle of the sensor in step 8 and the aircraft attitude angle in the flight data measured in step 5 into the position coordinate transformation matrix. The position coordinate transformation matrix is ​​the transformation matrix from the aircraft body axis coordinate to the ground coordinate system taking into account the sensor installation position.

[0046] The calculation formula of the position coordinate transformation matrix is:

[0047]

[0048] Step 10: Get the height of the aircraft's center of gravity relative to the ground: Substitute the position sensor data in the flight data measured in step 5 and the position coordinate conversion matrix in step 9 into the center of gravity height calculation formula to obtain the center of gravity height:

[0049] Center of gravity height calculation formula:

[0050]

[0051] Where: z cg is the height of the aircraft center of gravity, x cgq_T ,y cgq_T and z cgq_T are the heading, lateral and vertical installation positions of the position sensor in the body coordinate system, L T_D_str (3, all) is the third row of the position coordinate transformation matrix in step 9.

[0052] Furthermore, the measured load in the ground coordinate system and the position of the center of gravity of the aircraft in the ground coordinate system are integrated to obtain the energy absorbed by the aircraft buffer system, and the energy absorption efficiency is calculated, including:

[0053] Step 11: Calculate the energy absorbed by the cushioning system during the landing process: For the vertical load data P in step 7 z and the center of gravity height data z in step 10 cg Perform discrete integration to obtain the energy absorbed by the buffer system;

[0054] Discrete integral formula:

[0055]

[0056] Where: A c is the energy absorbed by the buffer system, P Z_i and P Z_i+1 is the vertical load of the landing gear at sampling point i and i+1, z cg_i and z cg_i+1 is the height of the aircraft center of gravity at sampling point i;

[0057] Step 12: Count the maximum vertical load P measured during the aircraft landing process in step 7 z_max and the maximum vertical height z of the center of gravity cg_max ;

[0058] Step 13: Buffer system energy absorption efficiency: Substitute the energy absorbed by the buffer system in step 11 and step 12 into the buffer system efficiency calculation formula;

[0059] Buffer system efficiency calculation formula:

[0060]

[0061] Where: η is the efficiency of the buffer system.

[0062] Furthermore, in step 1, the main force transmission channel at least includes a wheel axle, a piston rod, an outer cylinder and a support rod.

[0063] Furthermore, in step 1, a strain gauge sensitive to the vertical, heading and lateral loads of the landing gear is installed on the wheel axle; a strain gauge sensitive to the vertical and heading loads of the landing gear is installed on the piston rod; a strain gauge sensitive to the heading and lateral loads of the landing gear is installed on the outer cylinder; and a strain gauge sensitive to the heading load of the landing gear is installed on the strut.

[0064] Furthermore, during the actual flight measurement, the sampling rate of the test parameters shall not be lower than 128 Hz.

[0065] Furthermore, in step 4, sensors for measuring three-dimensional position, three-dimensional velocity and three-dimensional attitude are installed on the aircraft.

[0066] Furthermore, in step 4, the measured load in the ground coordinate system and the position of the center of gravity of the aircraft in the ground coordinate system are integrated to obtain the energy absorbed by the aircraft buffer system.

[0067] The beneficial effects of this application are:

[0068] (1) Compared with the previous calculation and evaluation of the energy absorption efficiency of the shock absorber based on laboratory drop data, this method calculates the energy absorption efficiency of the shock absorber system based on the actual measured data of the aircraft under real flight conditions. The calculated results reflect the performance of the shock absorber system under real conditions and have unparalleled authenticity;

[0069] (2) Compared with the previous calculation of the buffer energy absorption efficiency based on laboratory drop test data, this method provides a method for calculating the buffer energy based on actual flight test data. It can not only evaluate the performance of the aircraft buffer system, but also compare it with the drop test, providing direction for the optimization of the drop test. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Figure 1 is a flow chart of the method of the present invention;

[0071] Figure 2 It is the vertical load and center of gravity height curve in the ground coordinate system. DETAILED DESCRIPTION

[0072] The present invention relates to a method for calculating the energy absorption efficiency of a landing gear buffer system based on flight measured data, which belongs to the field of flight test technology. The present invention is based on the data of landing gear load calibration test and test record during aircraft flight, and according to the conversion matrix between the body coordinate system and the ground coordinate system, the landing gear load measured in the body coordinate system during flight is converted into the load in the ground coordinate system, and the initial installation position of the aircraft position sensor is considered at the same time, and the measured position of the position sensor is converted into the position at the center of gravity of the aircraft, and the vertical load in the ground coordinate system and the vertical position at the center of gravity of the aircraft are integrated to obtain the energy absorbed by the aircraft buffer system, and finally the energy absorption efficiency of the buffer system is calculated according to the energy absorbed by the buffer system and the measured vertical load in the ground coordinate system and the vertical position at the center of gravity of the aircraft. The present invention solves the problem of how to calculate the energy absorption efficiency of the aircraft buffer system according to the flight measured data, thereby determining the buffer performance of the aircraft buffer system under real use conditions, and providing more real data for the evaluation of the buffer system.

[0073] The invention calculates the energy absorbed by the aircraft landing gear buffer system and the energy absorption efficiency under full-scale and real flight conditions according to the landing gear load, aircraft position coordinates, aircraft attitude and other data measured during flight.

[0074] The present application is further described in detail below in conjunction with the accompanying drawings of the embodiments.

[0075] A method for calculating the energy absorption efficiency of an aircraft buffer system based on flight measured data, the method comprising the following steps:

[0076] Step 1: Install multiple load-measuring strain gauges on the main force transmission channel of the landing gear structure, including strain gauges sensitive to the vertical, heading and lateral loads of the landing gear; the main force transmission channel at least includes the wheel axle, piston rod, outer cylinder and strut, etc.;

[0077] Among them: a strain gauge sensitive to the vertical, heading and lateral loads of the landing gear is installed on the wheel axle; a strain gauge sensitive to the vertical and heading loads of the landing gear is installed on the piston rod; a strain gauge sensitive to the heading and lateral loads of the landing gear is installed on the outer cylinder; a strain gauge sensitive to the heading load of the landing gear is installed on the strut;

[0078] Step 2: Load calibration test: After the landing gear is installed and fixed, the landing gear is subjected to vertical, azimuth, and lateral unidirectional loading and two-way and three-way combined loading under the fixed buffer stroke. The loading load and structural strain data are recorded synchronously during the test; unidirectional loading in each direction must be performed, as well as two-way and three-way combined loading; the buffer fixed stroke includes at least three, named in sequence: s1, s2, s3, s1 <s2<s3;

[0079] Step 3: Substitute the loading load and the structural strain data measured by the load-measuring strain gauge under each stroke into the load-measuring model, and obtain the coefficients of the load-measuring model through linear regression; the coefficients of the load-measuring model for other strokes are obtained through linear difference;

[0080] The load model is:

[0081] F J =Kε ​​(1)

[0082] Linear regression solution formula for load model coefficients:

[0083] K=F J (εε T ) -1 (2)

[0084] In formula (1) and formula (2): F J is the loading load of the load calibration test; K is the load measurement model coefficient; ε is the structural strain measured by the load measurement strain gauge;

[0085] Other trips: the trip is not any of s1, s2, and s3;

[0086] The difference formula of the load model coefficient for other strokes:

[0087]

[0088] In formula (3): s is the buffer stroke; K s is the load model coefficient of stroke s; are the load measurement model coefficients for strokes s1, s2, and s3 respectively.

[0089] Step 4: Before the flight test, install GPS or GNS to measure three-dimensional position and three-dimensional speed, and inertial navigation to measure three-dimensional attitude on the aircraft; on the landing gear, in addition to the strain sensor installed in step 1, a buffer displacement sensor needs to be installed; at the same time, install test equipment to measure and record these parameters on the aircraft;

[0090] Step 5: Flight test: Conduct a landing test flight with a high sinking speed, requiring the pilot to control the aircraft to land at the required sinking speed; during the test, the test equipment synchronously collects and records the flight data in step 4;

[0091] Step 6: Flight load calculation: Substitute the structural strain data and buffer stroke data from the flight data measured in step 5 into the load measurement model in step 3 to obtain the flight measured load F F ;

[0092] F F is a column vector, and the measured heading load F x , lateral load Fy and vertical load F z composition:

[0093]

[0094] The method further includes converting the three-dimensional load of the flight measured load into the three-dimensional load in the ground coordinate system:

[0095] Step 7: Convert the measured load into the load in the ground coordinate system: Substitute the measured load and aircraft attitude into the conversion formula between the body coordinate system and the ground coordinate system.

[0096] Conversion formula between body coordinate system and ground coordinate system:

[0097]

[0098] P D is a column vector, which consists of three loads in the ground coordinate system, namely, the heading load P x , lateral load P y and vertical load P z composition:

[0099]

[0100] In formula (5), L T-D is the transformation matrix from the aircraft body axis coordinates to the ground coordinate system, and its calculation formula is:

[0101]

[0102] In formula (6): is the aircraft yaw angle, θ is the aircraft pitch angle, and φ is the aircraft roll angle, which are measured by attitude sensors such as gyroscopes on the aircraft;

[0103] In actual flight measurements, the center of gravity of the aircraft is often occupied by the central fuel tank or other components, and it is impossible to install sensors. Usually, a suitable location for installation is found on the fuselage of the aircraft to install a position sensor. At this time, the sensor actually measures the position of the sensor, not the center of gravity position of the aircraft. Therefore, the method also includes converting the sensor position measured in flight into the center of gravity position of the aircraft:

[0104] Step 8: Calculate the initial installation angle of the sensor: Get the installation position of the GNS position sensor in the body coordinate system as [x cgq_T y cgq_T z cgq_T ] T , calculate the initial installation angle of the sensor from the installation position.

[0105] The calculation formula for the initial installation angle is:

[0106]

[0107]

[0108] Where: is the initial installation yaw angle of the sensor, θ0 is the initial installation pitch angle of the sensor; cgq_T ,y cgq_T and z cgq_T They are the heading, lateral and vertical installation positions of the position sensor in the body coordinate system;

[0109] Step 9: Calculate the coordinate transformation matrix of the sensor: Substitute the initial installation angle of the sensor in step 8 and the aircraft attitude angle in the flight data measured in step 5 into the position coordinate transformation matrix to obtain the transformation matrix from the aircraft body axis coordinates to the ground coordinate system taking into account the sensor installation position.

[0110] The calculation formula of the position coordinate transformation matrix is:

[0111]

[0112] Step 10: Obtain the height of the aircraft's center of gravity relative to the ground: Substitute the position sensor data measured in step 5 and the position coordinate conversion matrix in step 9 into the center of gravity height calculation formula to obtain the center of gravity height.

[0113] Center of gravity height calculation formula:

[0114]

[0115] Where: z cg is the height of the aircraft center of gravity, x cgq_T ,y cgq_T and z cgq_T are the heading, lateral and vertical installation positions of the position sensor in the body coordinate system, L T_D_str (3, all) is the third row of the position coordinate transformation matrix in step 9;

[0116] The method further includes calculating the energy absorption efficiency of the buffer system based on flight measured data:

[0117] Step 11: Calculate the energy absorbed by the cushioning system during the landing process: For the vertical load data P in step 7 z and the center of gravity height data z in step 10 cg Perform discrete integration to obtain the energy absorbed by the buffer system.

[0118] The curve of the vertical load of the aircraft in the ground coordinate system changing with the height of the aircraft center of gravity is shown in Figure 2 ,right Figure 2 The discrete integral of the curve in is the energy absorbed by the buffer system.

[0119] Discrete integral formula:

[0120]

[0121] Where: A c is the energy absorbed by the buffer system, P Z_i and P Z_i+1 is the vertical load of the landing gear at sampling point i and i+1, z cg_i and z cg_i+1 is the height of the aircraft center of gravity at sampling point i.

[0122] Step 12: Count the maximum vertical load P measured during the aircraft landing process in step 7 z_max and the maximum vertical height z of the center of gravity cg_max ;

[0123] Step 13: Buffer system energy absorption efficiency: Substitute the energy absorbed by the buffer system in step 11 and step 12 into the buffer system efficiency calculation formula.

[0124] Buffer system efficiency calculation formula:

[0125]

[0126] Where: η is the efficiency of the buffer system.

Claims

1. A method for calculating the energy absorption efficiency of an aircraft buffer system based on flight measured data, characterized in that: The method is used to calculate the energy absorption efficiency of an aircraft cushioning system under real flight conditions, and the method comprises the following steps: Carry out load calibration test on landing gear to obtain test data, and determine the coefficient of load measurement model according to the test data; The measured data is brought into the load measurement model to obtain the measured external load, and the measured external load is projected to the ground coordinate system according to the attitude angle of the aircraft to obtain the measured load in the ground coordinate system; Substitute the measured sensor position, aircraft attitude and initial sensor installation position into the coordinate transformation matrix to obtain the position of the aircraft's center of gravity in ground coordinates; The measured load in the ground coordinate system and the position of the aircraft's center of gravity in the ground coordinate system are integrated to obtain the energy absorbed by the aircraft's buffer system and calculate the energy absorption efficiency.

2. The method according to claim 1, characterized in that The load calibration test of the landing gear is carried out to obtain the test data, and the coefficients of the load measurement model are determined according to the test data, including: Step 1: Install multiple load-measuring strain gauges on the main force transmission channel of the landing gear structure; Step 2: Load calibration test: After the landing gear is installed and fixed, the landing gear is subjected to vertical, azimuth, and lateral unidirectional loading and two-way and three-way combined loading under the fixed buffer stroke. The loading load and structural strain data are recorded synchronously during the test; unidirectional loading in each direction must be performed, as well as two-way and three-way combined loading; the buffer fixed stroke includes at least three, named in sequence: s1, s2, s3, s1 <s2<s3; Step 3: Substitute the loading load and the structural strain data measured by the load-measuring strain gauge under each stroke into the load-measuring model, and obtain the coefficients of the load-measuring model through linear regression; the coefficients of the load-measuring model for other strokes are obtained through linear difference; The load model is: FAVORITE J =Kε (1) Linear regression solution formula for load model coefficients: K=F J (hey T ) -1 (2) In formula (1) and formula (2): F J is the loading load of the load calibration test; K is the load measurement model coefficient; ε is the structural strain measured by the load measurement strain gauge; Other trips: the trip is not any of s1, s2, and s3; The difference formula of the load model coefficient for other strokes: In formula (3): s is the buffer stroke; K s is the load model coefficient of stroke s; are the load measurement model coefficients for strokes s1, s2, and s3 respectively.

3. The method according to claim 1, characterized in that The measured data is brought into the load measurement model to obtain the measured external load, and the measured external load is projected to the ground coordinate system according to the attitude angle of the aircraft to obtain the measured load in the ground coordinate system, including: Step 4: Before the flight test, install GPS or GNS to measure three-dimensional position and three-dimensional speed, and inertial navigation to measure three-dimensional attitude on the aircraft; on the landing gear, in addition to the strain gauge installed in step 1, a buffer displacement sensor needs to be installed; at the same time, install test equipment to measure and record these parameters on the aircraft; Step 5: Flight test: Conduct a landing test flight with a high sinking speed, requiring the pilot to control the aircraft to land at the required sinking speed; during the test, the test equipment collects and records flight data; Step 6: Flight load calculation: Substitute the structural strain data and buffer stroke data from the flight data measured in step 5 into the load measurement model in step 3 to obtain the flight measured load F F ; F F is a column vector, and the measured heading load F x , lateral load F y and vertical load F z composition: Step 7: Convert the measured load into the load in the ground coordinate system: Substitute the measured load and aircraft attitude into the conversion formula between the body coordinate system and the ground coordinate system: Conversion formula between body coordinate system and ground coordinate system: P D is a column vector, which consists of three loads in the ground coordinate system, namely, the heading load P x , lateral load P y and vertical load P z composition: In formula (5), L T-D is the transformation matrix from the aircraft body axis coordinate to the ground coordinate system, and its calculation formula is: In formula (6): is the aircraft's yaw angle, θ is the aircraft's pitch angle, and φ is the aircraft's roll angle, which are measured by attitude sensors such as gyroscopes on the aircraft.

4. The method according to claim 1, characterized in that Substitute the measured sensor position, aircraft attitude, and initial sensor installation position into the coordinate transformation matrix to obtain the position of the aircraft's center of gravity in ground coordinates, including: Step 8: Calculate the initial installation angle of the sensor: Get the installation position of the GNS position sensor in the body coordinate system as [x cgq_T y cgq_T z cgq_T ] T , calculate the initial installation angle of the sensor from the installation position; The calculation formula for the initial installation angle is: Where: is the initial installation yaw angle of the sensor, θ0 is the initial installation pitch angle of the sensor; cgq_ T.y cgq_ T and z cgq_ T are the heading, lateral and vertical installation positions of the position sensor in the body coordinate system, respectively; Step 9: Calculate the coordinate transformation matrix of the sensor: Substitute the initial installation angle of the sensor in step 8 and the aircraft attitude angle in the flight data measured in step 5 into the position coordinate transformation matrix. The position coordinate transformation matrix is ​​the transformation matrix from the aircraft body axis coordinate to the ground coordinate system taking into account the sensor installation position. The calculation formula of the position coordinate transformation matrix is: Step 10: Get the height of the aircraft's center of gravity relative to the ground: Substitute the position sensor data in the flight data measured in step 5 and the position coordinate conversion matrix in step 9 into the center of gravity height calculation formula to obtain the center of gravity height: Center of gravity height calculation formula: Where: z cg is the height of the aircraft center of gravity, x cgq_T ,y cgq_T and z cgq_T are the heading, lateral and vertical installation positions of the position sensor in the body coordinate system, L T_D_str (3, all) is the third row of the position coordinate transformation matrix in step 9.

5. The method according to claim 1, characterized in that Integrate the measured load in the ground coordinate system and the position of the aircraft's center of gravity in the ground coordinate system to obtain the energy absorbed by the aircraft's buffer system and calculate the energy absorption efficiency, including: Step 11: Calculate the energy absorbed by the cushioning system during the landing process: For the vertical load data P in step 7 z and the center of gravity height data z in step 10 cg Perform discrete integration to obtain the energy absorbed by the buffer system; Discrete integral formula: Where: A c is the energy absorbed by the buffer system, P Z_i and P Z_i+1 is the vertical load of the landing gear at sampling point i and i+1, z cg_i and z cg_i+1 is the height of the aircraft center of gravity at sampling point i; Step 12: Count the maximum vertical load P measured during the aircraft landing process in step 7 z_max and the maximum vertical height z of the center of gravity cg_max ; Step 13: Buffer system energy absorption efficiency: Substitute the energy absorbed by the buffer system in step 11 and step 12 into the buffer system efficiency calculation formula; Buffer system efficiency calculation formula: Where: η is the efficiency of the buffer system.

6. The method according to claim 2, characterized in that In step 1, the main force transmission channel at least includes a wheel axle, a piston rod, an outer cylinder and a support rod.

7. The method according to claim 4, characterized in that In step 1, a strain gauge sensitive to the vertical, heading and lateral loads of the landing gear is installed on the wheel axle; a strain gauge sensitive to the vertical and heading loads of the landing gear is installed on the piston rod; a strain gauge sensitive to the heading and lateral loads of the landing gear is installed on the outer cylinder; and a strain gauge sensitive to the heading load of the landing gear is installed on the strut.

8. The method according to claim 7, characterized in that During the actual flight test, the sampling rate of the test parameters shall not be lower than 128HZ.

9. The method according to claim 3, characterized in that: In step 4, sensors for measuring three-dimensional position, three-dimensional velocity and three-dimensional attitude are installed on the aircraft.

10. The method according to claim 5, characterized in that In step 4, the measured load in the ground coordinate system and the position of the center of gravity of the aircraft in the ground coordinate system are integrated to obtain the energy absorbed by the aircraft buffer system.

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