Aircraft landing gear test wheel force sensor and information acquisition system and decoupling method

Abstract

The invention discloses a wheel force sensor for testing an aircraft landing gear, an information collection system and a decoupling method. In the device, the wheel force sensor comprises a wheel shaft, a shaft sleeve sleeved on the wheel shaft, a force sensor elastic body sleeved on the shaft sleeve, a left wheel hub and a right wheel hub symmetrically arranged on both sides of the force sensor elastic body and connected to the force sensor elastic body, and a fixing part for fixing the left wheel hub and the right wheel hub; the force sensor elastic body comprises an inner ring sleeved on the shaft sleeve, 8 elastic strain beams uniformly arranged on the circumference of the inner ring, an outer ring for connecting the elastic strain beams, and a strain gauge bridge module adhered to the elastic beams of the elastic body; the device integrates the wheel sensor inside the wheel and measures the force and torque acting on the tire in real time, thereby providing real-time data of load and impact borne by the aircraft tire in a real working scenario, and providing a means for tire performance evaluation.

Description

Technical Field

[0001] The invention relates to a wheel force measurement for aircraft take-off and landing, in particular to a wheel force sensor for aircraft landing gear testing, an information collection system and a decoupling method, and relates to the technical field of aviation machinery. Background Art

[0002] Aircraft landing gear is a system that provides suspension support during taxiing, takeoff and landing, and is an important load-bearing structure of the aircraft. As an important part of the landing gear system, aircraft tires bear the entire weight of the aircraft during taxiing, takeoff and landing, and meet various demanding working conditions. Landing gear wheels are components with extremely high safety and reliability requirements. The safe takeoff and landing of aircraft must rely on the various unique functions of aircraft tires. Therefore, it is important to study the real-time stress of aircraft tires during operation, monitor and analyze the stress of aircraft tires in real time, and determine the loads and impacts applied to tires during aircraft takeoff and landing. This is of great significance to aircraft performance evaluation, parameter design, standard formulation, and the study of system factors and environmental factors that affect the performance of aircraft tires.

[0003] In the prior art, CN117382909B discloses an aircraft landing gear fatigue characteristic test assembly, which applies radial alternating load to the aircraft landing gear to simulate the fatigue strength test of the landing gear under the conditions of aircraft landing, ground taxiing and take-off. CN117191316A discloses a drop shock test platform for aircraft landing gear testing and a drop shock test method thereof. The test platform adopts a chain plate-roller structure, and simulates the horizontal speed of the landing gear and the ground when the aircraft lands by rotating the transmission chain plate on the impact platform, which greatly saves the space occupied by the equipment, realistically simulates the speed change when the aircraft lands, and can effectively test the aircraft landing gear. CN111169653B discloses a front landing gear hinge force test device and load calibration method, which simulates different operating conditions of the front landing gear with the help of the test bench, accurately tests the hinge force of the front landing gear under various working conditions, and realizes a hinge force test method with high precision, long service life, and the ability to withstand large impact vibration, and provides data guidance for the design of the structure and strength of the front landing gear. There are few public research reports on the technology of in-situ online testing of aircraft landing gear. The embedded tire force sensor for civil aircraft developed by Professor J Pytka of the School of Mechanical Engineering of Lublin University of Technology in Poland in 2018 is a typical representative of such research abroad, while domestic research in this field is still blank.

[0004] At the same time, the above patents still have many deficiencies in practical applications:

[0005] 1. The device and test method described in the above patent are for indoor bench testing. Although indoor bench testing can provide real-time stress conditions of aircraft tires under given working conditions, it still cannot fully simulate the actual operating scenarios of aircraft, such as the condition of the whole aircraft, road performance and weather conditions, which have an important impact on the performance of aircraft tires;

[0006] 2. At the same time, indoor test benches require a large amount of road spectrum data (displacement / load-time curve) as input for road condition simulation. The existing simulation excitation data cannot truly reflect the real-time load of tire-ground interaction.

[0007] Therefore, how to measure the wheel force during aircraft takeoff and landing is a problem that needs to be solved at present. Summary of the invention

[0008] Purpose of the invention: To provide an aircraft landing gear test wheel force sensor and an information collection system and a decoupling method to solve the above-mentioned problems existing in the prior art.

[0009] Technical solution: Aircraft landing gear test wheel force sensor and information collection system and decoupling method, including:

[0010] The wheel force sensor includes a wheel shaft, a shaft sleeve sleeved on the wheel shaft, a force sensor elastic body sleeved on the shaft sleeve, a left wheel hub and a right wheel hub symmetrically arranged on both sides of the force sensor elastic body and connected to the force sensor elastic body, and a fixing part for fixing the left wheel hub and the right wheel hub;

[0011] The force sensor elastic body comprises an inner ring sleeved on the shaft sleeve, 8 elastic strain beams uniformly arranged on the circumference of the inner ring, an outer ring for connecting the elastic strain beams, and a strain gauge bridge module attached to the elastic beams of the elastic body.

[0012] The left wheel hub and the right wheel hub have the same structure and are both split structures, including a bearing seat and a wheel hub;

[0013] An outer gear ring is provided on one side of the bearing seat, and a gear ring is provided on the inner wall of the inner ring. The bearing seat is connected to the inner ring by meshing the outer gear ring with the gear ring, and the inner wall of the outer gear ring abuts against the outer wall of the sleeve;

[0014] The outer ring is provided with at least three bolt holes in the axial direction, and a support seat is provided on the inner wall of the hub, and the hub is fixed by using bolts passing through the bolt holes and the bolt holes on the outer ring;

[0015] The fixing part includes a bearing located in the bearing seat and sleeved on the shaft sleeve, a bearing washer abutting against the bearing, a bearing end cover connected to the bearing washer, a nut washer sleeved on the machine wheel shaft, and a slot nut for fixing the bearing end cover on the machine wheel shaft;

[0016] During operation, the wheel hub transmits force to the outer ring in the force sensor elastic body through bolt connection, and the outer ring transmits force to the inner ring in the force sensor elastic body through the strain beam; during the transmission process, the force sensor elastic body is deformed to complete the measurement work.

[0017] The information acquisition system includes an acquisition and conditioning unit connected to the wheel force sensor, and a data acquisition and analysis host computer connected to the acquisition and conditioning unit;

[0018] The acquisition and conditioning unit includes a control module and a power module, an analog-to-digital conversion module, a communication module and a turning angle module that interact bidirectionally with the control module, and a signal conditioning module that interacts with the analog-to-digital conversion module;

[0019] The data acquisition and analysis host computer includes four sub-function modules: system configuration, real-time control, real-time display and data management;

[0020] The acquisition and conditioning unit is installed on one side of the elastic body and fixed by bolts, and is used to acquire the voltage at both ends of the strain gauge.

[0021] In a further embodiment, the strain gauge bridge module includes resistor R1, resistor R2, resistor R3, resistor R4, resistor R5, resistor R6, resistor R7, resistor R8, resistor R9, resistor R10, resistor R11, resistor R12, resistor R13, resistor R14, resistor R15, and resistor R16;

[0022] Each elastic strain beam is provided with two resistors, and the installation order of the resistors in a clockwise direction is resistor R2, resistor R1, resistor R16, resistor R15, resistor R8, resistor R7, resistor R14, resistor R13, resistor R6, resistor R5, resistor R12, resistor R11, resistor R4, resistor R3, resistor R10, resistor R9;

[0023] Wherein, one end of the resistor R1 is respectively connected to one end of the resistor R5, one end of the resistor R3, one end of the resistor R7, one end of the resistor R9, one end of the resistor R10 and the positive electrode of the input voltage, the other end of the resistor R1 is connected to one end of the resistor R6, the other end of the resistor R6 is respectively connected to the negative electrode of the output voltage, one end of the resistor R2, one end of the resistor R8, one end of the resistor R4, one end of the resistor R16 and one end of the resistor R15, the other end of the resistor R2 is connected to one end of the resistor R5, the other end of the resistor R8 is connected to the other end of the resistor R3, the other end of the resistor R4 is connected to the other end of the resistor R7, the other end of the resistor R16 is connected to one end of the resistor R14, the other end of the resistor R14 is connected to one end of the resistor R11, the other end of the resistor R11 is connected to the other end of the resistor R9, the other end of the resistor R15 is connected to one end of the resistor R13, the other end of the resistor R13 is connected to one end of the resistor R12, and the other end of the resistor R12 is connected to the other end of the resistor R10;

[0024] Then the channel voltage difference between the connection point of resistor R1 and resistor R6 and the connection point of resistor R5 and resistor R2 is calculated as ΔU Fz , measure the channel voltage difference between the connection of resistor R3 and resistor R8 and the connection of resistor R4 and resistor R7 as ΔU Fx , and the channel voltage difference at the connection between resistor R11 and resistor R14 and at the connection between resistor R13 and resistor R12 is ΔU My Then, ΔU Fz , ΔU Fx and ΔU My The value is transmitted to the acquisition and conditioning unit.

[0025] In a further embodiment, the elastic body of the force sensor should be subjected to finite element analysis results to determine the pasting position of the strain gauge, and the strength should be checked by the maximum shear stress theory. The criteria are:

[0026]

[0027] Among them, σ1 and σ3 represent the maximum normal stress and neutral stress at each point inside the object respectively; Indicates the yield strength of the material;

[0028] Finite element analysis uses the finite element method to analyze static or dynamic physical objects or physical systems; in this method, an object or system is decomposed into a geometric model consisting of multiple interconnected, simple, independent points.

[0029] In a further embodiment, f x 、f z and m y Strain analysis is performed when the three forces and moments act alone. According to the principle of mechanical superposition, the micro-deformation of the structure is composed of three basic deformations, namely tension, compression, bending and torsion, or their combination and superposition.

[0030] Therefore, the output value of the wheel force multi-channel is:

[0031]

[0032] Where t x 、f z and m y They are ΔU Fx , ΔU Fz and ΔU My The force output corresponding to the measured channel; σ i (i=1-16) is the strain gauge strain corresponding to the serial number; k1, k2 and k3 are calibration coefficients; according to the designed layout and bridge assembly method, when each component of the three-dimensional force is loaded separately, the output of the remaining channels is close to 0.

[0033] In a further embodiment, the analog-to-digital conversion module in the acquisition and conditioning unit is an A / D conversion module, the communication module is a Bluetooth communication module, and the control module is an STM32 control module;

[0034] The power module described therein realizes power supply to other parts of the acquisition system through various buck and voltage stabilizing chips. The power module uses a 12V lithium battery as a power supply device, and then uses different buck chips to reduce its voltage to 5V, and then reduces the 5V voltage to 3.3V and 2.5V, of which the 2.5V voltage provides a reference voltage for the signal conditioning module;

[0035] The signal conditioning module realizes zeroing, amplification and filtering of the bridge output and transmits the processed bridge output signal to the A / D conversion module, wherein the signal conditioning module is provided with three;

[0036] The A / D conversion module realizes analog-to-digital conversion of the signal conditioning circuit and outputs the sensor data to the STM32 control module through the SPI bus;

[0037] The angle acquisition module is responsible for transmitting the collected wheel angle information to the STM32 control module;

[0038] The STM32 control module packages the data according to the designed communication protocol and sends it to the host computer via Bluetooth communication to complete the data collection.

[0039] In a further embodiment, the signal conditioning module includes an operational amplifier U1, whose model is AD620, a resistor R17, a resistor R18, a resistor R19, a resistor R20, a capacitor C1, a capacitor C7, a capacitor C8 and a sliding rheostat VR1;

[0040] Wherein a first pin of the operational amplifier U1 is connected to one end of the resistor R20, and the other end is connected to the eighth pin of the operational amplifier U1; a second pin of the operational amplifier U1 is respectively connected to one end of the resistor R19, one end of the capacitor C1 and the connection point between the resistor R5 and the resistor R2 in the strain bridge module; the other end of the resistor R19 is connected to a first pin of a sliding rheostat VR1; a second pin of the sliding rheostat VR1 is connected to one end of a resistor R18; the other end of the resistor R18 is connected to the connection point between the resistor R1 and the resistor R6, the other end of the capacitor C1 and the third pin of the operational amplifier U1; the third pin of the sliding rheostat VR1 is respectively connected to the seventh pin of the operational amplifier U1 and one end of the capacitor C1; a sixth pin of the operational amplifier U1 is connected to one end of the resistor R17, and the other end of the resistor R17 is connected to one end of the capacitor C8;

[0041] The other ends of the capacitor C7 and the capacitor C8 are grounded, and the fourth pin of the operational amplifier U1 is grounded;

[0042] The fifth pin of the operational amplifier U1 is connected to the regulated 2.5V voltage in the power module.

[0043] In a further embodiment, the A / D conversion module includes an integrated circuit U9, a resistor R24, a resistor R26, a capacitor C40, a capacitor C30, a capacitor C31, a capacitor C34, a capacitor C35, a capacitor C36, a capacitor C37, an inductor L4, and an inductor L5; the model of the integrated circuit U9 is AD7607;

[0044] Among them, the twenty-third pin of the integrated circuit U9 is respectively connected to the 3.3V voltage in the power module and one end of the capacitor C30, the forty-fourth and forty-fifth pins of the integrated circuit U9 are connected and then connected to one end of the capacitor C31, the thirty-sixth pin of the integrated circuit U9 is connected to one end of the capacitor C34, the thirty-ninth pin of the integrated circuit U9 is connected to one end of the capacitor C35, the first pin, the forty-eighth, the thirty-seventh and the thirty-eighth pins of the integrated circuit U9 are connected and then connected to one end of the inductor L4 and one end of the capacitor C36, the other end of the inductor L4 is connected to one end of the capacitor C37 and one end of the inductor L5, the sixth pin of the integrated circuit U9 is respectively connected to one end of the resistor R24 ​​and the resistor R26, and the forty-second pin of the integrated circuit U9 is connected to one end of the capacitor C40;

[0045] The seventh and thirty-fourth pins of the integrated circuit U9 and the other end of the resistor R24 ​​are respectively connected to the stabilized 3.3V voltage in the power module;

[0046] The other end of capacitor C30, the other end of capacitor C31, the other end of capacitor C34, the other end of capacitor C35, the other end of capacitor C36, the other end of capacitor C37, the other end of inductor L5, the other end of resistor R26, the other end of capacitor C40, and pins 3, 4, 5, 50, 52, 54, 56-64, 40, 41, 47, 35, 26, 2, 46, and 43 of integrated circuit U9 are grounded respectively.

[0047] In a further embodiment, the system configuration module is used to perform comprehensive management of the experimental equipment, including equipment initialization, calibration, and connection status monitoring. It can also perform basic system settings, such as sampling frequency, data format, storage path, etc., to ensure the accuracy and consistency of data collection;

[0048] The real-time control module is used to control the experimental process in real time to ensure stable data collection. Through the preset control logic, it can accurately control the operating status of the experimental equipment, as well as the start, pause and end of data collection, so as to completely record all data in the experimental process;

[0049] Real-time display The real-time display module provides a friendly interface design. Through charts, curves, numbers and other forms, the module can display the dynamic changes of experimental data in real time, helping users to monitor the experimental process in real time and quickly find potential problems;

[0050] The data management module focuses on the query and management of historical data and has a data retrieval function, allowing users to easily query previous data files. At the same time, the data management module is also responsible for data backup, recovery and export operations to ensure data security and availability. At the same time, the module realizes real-time storage and long-term preservation of experimental data through storage algorithms and storage devices.

[0051] A wheel force decoupling method of an information collection system of a wheel force sensor based on aircraft landing gear testing comprises the following steps:

[0052] Step 1: Establish the input-output relationship model between the axes corresponding to the multiple axes of the sensor, that is, the multiple channels, and solve the relationship between the output voltage data of each channel of the sensor and the actual force through calibration experiments;

[0053] The relationship between the multi-channel voltage output and the multi-dimensional force output of the wheel force sensor can be expressed as:

[0054] f=Cv (3)

[0055] Where, f = [f x ,f z ,m y ] Tis the multi-dimensional force output of the sensor, that is, the multi-dimensional force output corresponding to the multi-channel measured in the strain gauge bridge module, v = [v x ,v z ,v y ] T is the multi-channel voltage output, C is the calibration matrix;

[0056] It is necessary to solve the calibration matrix C using the least squares method based on the calibration experimental data, as shown below:

[0057] C=FV -1 (4)

[0058] Where F=[f1,···,f n ] is the multi-channel load data in the calibration experiment; V = [v1,···,v n ] is the corresponding voltage response data, where n is the number of channels;

[0059] Step 2: The sensor output needs to be rotationally decoupled to obtain the wheel force in the wheel coordinate system;

[0060] According to the principle of force coordinate decomposition and the measured rotation angle, the sensor output can be converted into six-dimensional force in wheel coordinates by the following formula:

[0061] F w =R(θ)·F e (5)

[0062] in is the force in the wheel coordinate system, is the force in the elastic body coordinate system, is the rotation matrix;

[0063] Then, the wheel angle measured by the angle acquisition module is used to convert the force in the elastic body coordinate system to the wheel coordinate system to complete the rotational decoupling and realize the measurement of runway load data.

[0064] Beneficial effect: The present invention discloses a wheel force sensor for testing aircraft landing gear, an information collection system and a decoupling method. By integrating the wheel force sensor into the aircraft landing gear tire by modifying the landing gear tire structure, the forces and moments in all directions of the landing gear tire can be monitored in real time in the actual working scene of the aircraft take-off and landing operation, and real-time data of the load and impact borne by the aircraft tire in the real working scene can be provided. These data not only include simple load and impact information, but also can comprehensively reflect the actual working state of the landing gear tire under the condition of the whole machine, facing different road performance and weather conditions, and provide information for the performance evaluation of the landing gear. It provides a means to provide a basis for the aircraft parameter design and optimization. At the same time, these data also help to conduct a more in-depth study of the system factors and environmental factors that affect the performance of the landing gear tire, thereby further improving the safety and reliability of the aircraft; integrating the wheel sensor inside the wheel provides real-time data on the load and impact of the aircraft tire in real working scenarios by measuring the force and torque acting on the tire in real time, providing a means for tire performance evaluation and a basis for aircraft parameter design and optimization. At the same time, it is of great significance to study the system factors and environmental factors that affect tire performance, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0066] Figure 2 Detailed description of the invention FIG.

[0067] Figure 3 It is an isometric view of the wheel force sensor of the present invention.

[0068] Figure 4 It is an exploded schematic diagram of the wheel force sensor of the present invention.

[0069] Figure 5 is an embodiment of the present invention x Directional Mises strain cloud diagram.

[0070] Figure 6 is m of one embodiment of the present invention y Directional Mises strain cloud diagram.

[0071] Figure 7 Schematic diagram of a strain gauge layout according to an embodiment of the present invention.

[0072] Figure 8 Schematic diagram of a strain gauge bridge assembly according to an embodiment of the present invention.

[0073] Fig. 9 It is a signal conditioning circuit diagram of an embodiment of the present invention.

[0074] Fig.10FIG. 1 is a pin diagram of AD620 according to an embodiment of the present invention.

[0075] Fig.11 1 is an A / D sampling circuit diagram of an embodiment of the present invention.

[0076] Fig.12 It is a block diagram of a runway load collection and analysis system according to an embodiment of the present invention.

[0077] The reference numerals in the drawings are: slotted nut 1, bearing end cover 2, bearing 3, left wheel hub 4, force sensor elastomer 5, shaft sleeve 6, machine wheel axle 7, right wheel hub 8, bearing gasket 9, nut gasket 10. DETAILED DESCRIPTION

[0078] The invention discloses an aircraft landing gear test wheel force sensor and information collection system and decoupling method, comprising: a slotted nut 1, a bearing end cover 2, a bearing 3, a left wheel hub 4, a force sensor elastomer 5, a shaft sleeve 6, a wheel shaft 7, a right wheel hub 8, a bearing gasket 9, and a nut gasket 10.

[0079] The device comprises the runway load acquisition system including a wheel force sensor, an acquisition and conditioning unit connected to the wheel force sensor, and a data acquisition and analysis host computer connected to the acquisition and conditioning unit;

[0080] The acquisition and conditioning unit includes a control module and a power module, an analog-to-digital conversion module, a communication module and a turning angle module that interact bidirectionally with the control module, and a signal conditioning module that interacts with the analog-to-digital conversion module;

[0081] The data acquisition and analysis host computer includes four sub-function modules: system configuration, real-time control, real-time display and data management;

[0082] The wheel force sensor includes a wheel shaft 7, a sleeve 6 sleeved on the wheel shaft 7, a force sensor elastic body 5 sleeved on the sleeve 6, a left wheel hub 4 and a right wheel hub 8 symmetrically arranged on both sides of the force sensor elastic body 5 and connected to the force sensor elastic body 5, and a fixing part for fixing the left wheel hub 4 and the right wheel hub 8;

[0083] The force sensor elastic body 5 includes an inner ring sleeved on the shaft sleeve 6, 8 elastic strain beams uniformly arranged on the circumference of the inner ring, an outer ring for connecting the elastic strain beams, and a strain gauge bridge module attached to the elastic beams of the elastic body.

[0084] The acquisition and conditioning unit is installed on one side of the elastic body and fixed by bolts, and is used to collect the voltage at both ends of the strain gauge;

[0085] The left wheel hub 4 and the right wheel hub 8 have the same structure and are both split structures, including a bearing 3 seat and a wheel hub;

[0086] An outer gear ring is provided on one side of the bearing 3 seat, and a gear ring is provided on the inner wall of the inner ring. The bearing 3 seat is connected to the inner ring by meshing the outer gear ring with the gear ring, and the inner wall of the outer gear ring abuts against the outer wall of the sleeve 6;

[0087] The outer ring is provided with at least three bolt holes in the axial direction, and a support seat is provided on the inner wall of the hub, and the hub is fixed by using bolts passing through the bolt holes and the bolt holes on the outer ring;

[0088] During operation, the wheel hub transmits force to the outer ring in the force sensor elastomer 5 through bolt connection, and the outer ring transmits force to the inner ring in the force sensor elastomer 5 through the strain beam; during the transmission process, the force sensor elastomer 5 is deformed to complete the measurement work; the fixing part includes a bearing 3 located in the bearing 3 seat and sleeved on the shaft sleeve 6, a bearing gasket 9 abutting against the bearing 3, a bearing 3 end cover 2 connected to the bearing gasket 9, a nut gasket 10 sleeved on the machine wheel shaft 7, and a groove nut 1 for fixing the bearing 3 end cover 2 on the machine wheel shaft 7; the overall structure is connected to the machine wheel shaft 7 through the groove nut 1 at the shaft end to complete the axial fixation of the overall structure.

[0089] The strain gauge bridge module includes resistors R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, R15 and R16;

[0090] Each elastic strain beam is provided with two resistors, and the installation order of the resistors in a clockwise direction is resistor R2, resistor R1, resistor R16, resistor R15, resistor R8, resistor R7, resistor R14, resistor R13, resistor R6, resistor R5, resistor R12, resistor R11, resistor R4, resistor R3, resistor R10, resistor R9;

[0091] Wherein, one end of the resistor R1 is respectively connected to one end of the resistor R5, one end of the resistor R3, one end of the resistor R7, one end of the resistor R9, one end of the resistor R10 and the positive electrode of the input voltage, the other end of the resistor R1 is connected to one end of the resistor R6, the other end of the resistor R6 is respectively connected to the negative electrode of the output voltage, one end of the resistor R2, one end of the resistor R8, one end of the resistor R4, one end of the resistor R16 and one end of the resistor R15, the other end of the resistor R2 is connected to one end of the resistor R5, the other end of the resistor R8 is connected to the other end of the resistor R3, the other end of the resistor R4 is connected to the other end of the resistor R7, the other end of the resistor R16 is connected to one end of the resistor R14, the other end of the resistor R14 is connected to one end of the resistor R11, the other end of the resistor R11 is connected to the other end of the resistor R9, the other end of the resistor R15 is connected to one end of the resistor R13, the other end of the resistor R13 is connected to one end of the resistor R12, and the other end of the resistor R12 is connected to the other end of the resistor R10;

[0092] Then the channel voltage difference between the connection point of resistor R1 and resistor R6 and the connection point of resistor R5 and resistor R2 is calculated as ΔU Fz , measure the channel voltage difference between the connection of resistor R3 and resistor R8 and the connection of resistor R4 and resistor R7 as ΔU Fx , and the channel voltage difference at the connection between resistor R11 and resistor R14 and at the connection between resistor R13 and resistor R12 is ΔU My Then, ΔU Fz , ΔU Fx and ΔU My The value is transmitted to the acquisition and conditioning unit.

[0093] The elastic body of the force sensor should be subjected to finite element analysis results to determine the pasting position of the strain gauge, and the strength should be checked by the maximum shear stress theory. The criteria are:

[0094]

[0095] Among them, σ1 and σ3 represent the maximum normal stress and neutral stress at each point inside the object respectively; Indicates the yield strength of the material; according to the finite element results, f x 、f z and m y Strain analysis is performed when the three forces and moments act alone. According to the principle of mechanical superposition, the micro-deformation of the structure is composed of three basic deformations, namely tension, compression, bending and torsion, or their combination and superposition.

[0096] Therefore, the output value of the wheel force multi-channel is:

[0097]

[0098] Where f x 、f z and my They are ΔU Fx , ΔU Fz and ΔU My The force output corresponding to the measured channel; σ i (i=1-16) is the strain gauge strain corresponding to the serial number; k1, k2 and k3 are calibration coefficients; according to the designed layout and bridge assembly method, when each component of the three-dimensional force is loaded separately, the output of the remaining channels is close to 0.

[0099] In a further embodiment, the elastic body model is first divided into three entities: the inner ring, the outer ring and the elastic beam. The contact between the parts is an automatic control constraint. A mixed curvature grid is used. The maximum unit size is 4.44617 mm, the minimum unit size is 0.444617 mm, and there are 943303 units in total. The calculation is performed by fixing the inner ring and loading the outer ring. Due to the symmetry of the structure and the load, f x 、f z and m y Finite element analysis is performed on the case where the three forces and moments act separately. x Directional strain analysis such as Figure 5 As shown, f x When the elastic beam CG is in a uniform compressive stress state, the elastic beam AE is in a pure bending shear state. The strain gauge layout scheme is: arrange along the radial direction of the CG beam and form a bridge to measure f x The f z Directional strain and f x The direction is consistent. y Directional strain analysis such as Figure 6 As shown, m y Under the action, the deformation of the 8 elastic beams is bending deformation, but the bending directions are orthogonal. The front of the elastic beam is the neutral layer with small strain. On the side of the elastic beam, the root strain is the largest, and the middle is 0. Therefore, the strain gauge for measuring F3 can be attached to the root of the side of the elastic beam. According to the strain analysis results, the strain gauge layout method and bridge circuit are designed as follows Figure 7 , 8 As shown, the output of each channel of the wheel force can be obtained as mentioned above.

[0100] The analog-to-digital conversion module in the acquisition and conditioning unit is an A / D conversion module, the communication module is a Bluetooth communication module, and the control module is an STM32 control module;

[0101] The power module described therein realizes power supply to other parts of the acquisition system through various buck and voltage stabilizing chips. The power module uses a 12V lithium battery as a power supply device, and then uses different buck chips to reduce its voltage to 5V, and then reduces the 5V voltage to 3.3V and 2.5V, of which the 2.5V voltage provides a reference voltage for the signal conditioning module;

[0102] The signal conditioning module realizes zeroing, amplification and filtering of the bridge output and transmits the processed bridge output signal to the A / D conversion module, wherein the signal conditioning module is provided with three;

[0103] The A / D conversion module realizes analog-to-digital conversion of the signal conditioning circuit and outputs the sensor data to the STM32 control module through the SPI bus;

[0104] The angle acquisition module is responsible for transmitting the collected wheel angle information to the STM32 control module;

[0105] The STM32 control module packages the data according to the designed communication protocol and sends it to the host computer via Bluetooth communication to complete the data collection;

[0106] In a further embodiment, the present invention adopts AK7455 rotation angle sensor to measure the wheel angle. AK7455 is a 14-bit absolute rotation angle sensor suitable for off-axis scenarios. It can achieve high-precision measurement of the wheel angle while improving the integration of the acquisition circuit.

[0107] The signal conditioning module includes an operational amplifier U1, whose model is AD620, a resistor R17, a resistor R18, a resistor R19, a resistor R20, a capacitor C1, a capacitor C7, a capacitor C8 and a sliding rheostat VR1;

[0108] Wherein a first pin of the operational amplifier U1 is connected to one end of the resistor R20, and the other end is connected to the eighth pin of the operational amplifier U1; a second pin of the operational amplifier U1 is respectively connected to one end of the resistor R19, one end of the capacitor C1 and the connection point between the resistor R5 and the resistor R2 in the strain bridge module; the other end of the resistor R19 is connected to a first pin of a sliding rheostat VR1; a second pin of the sliding rheostat VR1 is connected to one end of a resistor R18; the other end of the resistor R18 is connected to the connection point between the resistor R1 and the resistor R6, the other end of the capacitor C1 and the third pin of the operational amplifier U1; the third pin of the sliding rheostat VR1 is respectively connected to the seventh pin of the operational amplifier U1 and one end of the capacitor C1; a sixth pin of the operational amplifier U1 is connected to one end of the resistor R17, and the other end of the resistor R17 is connected to one end of the capacitor C8;

[0109] The other ends of the capacitor C7 and the capacitor C8 are grounded, and the fourth pin of the operational amplifier U1 is grounded;

[0110] The fifth pin of the operational amplifier U1 is connected to the regulated 2.5V voltage in the power module;

[0111] When there is no signal input, the bridge output is set to 0 by adjusting the potentiometer VR1. In order to minimize the impact of the zero adjustment circuit on the original bridge, the resistors R18 and R19 must be much larger than the resistance of the bridge. The bridge strain gauge resistance is 350Ω, so 47K is selected as the bypass resistor of the zero adjustment circuit in this article, and 200K is the maximum range of the potentiometer. In addition, the capacitor is used to filter out high-frequency noise in the bridge circuit. When the wheel is loaded, the output signal of the bridge is usually at the mV level, so the analog signal needs to be amplified before A / D sampling;

[0112] In a further embodiment, the amplifier has a smaller size, higher input impedance, common mode rejection ratio and open loop gain than a discrete operational amplifier, and is suitable for circuits with high precision and stability. At the same time, AD620 can be powered by a single power supply, which simplifies the design of the power supply circuit. Among them, the signal input pins are pins 3 and 2, the power input pins are pins 7 and 4, the reference voltage input pin is pin 5, the amplified output pin is pin 6, and the gain adjustment pins are pins 1 and 8. Because the differential voltage signal output from the elastic body is generally -0.25mV-0.25mV, in order to achieve the A / D conversion range, the voltage signal needs to be amplified 8000-10000 times. By adjusting the potentiometer R_G, as shown, the gain of AD620 reaches about 8000-10000 times. At the same time, after passing through the RC filter, the amplified voltage signal is output to the A / D sampling circuit.

[0113] The A / D conversion module includes an integrated circuit U9, a resistor R24, a resistor R26, a capacitor C40, a capacitor C30, a capacitor C31, a capacitor C34, a capacitor C35, a capacitor C36, a capacitor C37, an inductor L4, and an inductor L5;

[0114] Among them, the twenty-third pin of the integrated circuit U9 is respectively connected to the 3.3V voltage in the power module and one end of the capacitor C30, the forty-fourth and forty-fifth pins of the integrated circuit U9 are connected and then connected to one end of the capacitor C31, the thirty-sixth pin of the integrated circuit U9 is connected to one end of the capacitor C34, the thirty-ninth pin of the integrated circuit U9 is connected to one end of the capacitor C35, the first pin, the forty-eighth, the thirty-seventh and the thirty-eighth pins of the integrated circuit U9 are connected and then connected to one end of the inductor L4 and one end of the capacitor C36, the other end of the inductor L4 is connected to one end of the capacitor C37 and one end of the inductor L5, the sixth pin of the integrated circuit U9 is respectively connected to one end of the resistor R24 ​​and the resistor R26, and the forty-second pin of the integrated circuit U9 is connected to one end of the capacitor C40;

[0115] The seventh and thirty-fourth pins of the integrated circuit U9 and the other end of the resistor R24 ​​are respectively connected to the stabilized 3.3V voltage in the power module;

[0116] The other end of capacitor C30, the other end of capacitor C31, the other end of capacitor C34, the other end of capacitor C35, the other end of capacitor C36, the other end of capacitor C37, the other end of inductor L5, the other end of resistor R26, and the other end of capacitor C40 are grounded respectively;

[0117] In a further embodiment, AD7606 is a 16-bit A / D chip that supports 4, 6, and 8 synchronous sampling inputs, supports 5V single power supply, has a precision reference voltage source on the chip, can communicate in parallel or serial interface, and supports a maximum sampling rate of 200kpbs. The acquisition circuit uses an internal reference voltage, and the SPI high-speed serial interface communicates with STM32. Among them, A1~A4 are analog input voltages, and the ±5V range can be selected by pulling down the RANGE pin level. SCLK connects to the clock signal of the SPI bus, CS is the chip select signal, and DB7 / DOUTA connects to the MISO pin of the SPI. In order to achieve six-channel synchronous sampling, the CONVSTA and CONVST pins should be shorted, and a high-level to low-level conversion start signal should be given. This article selects serial byte transmission, so the *PAR / SER / BYTE_SEL pin is pulled up to a high level, and in order to use the internal reference voltage source, the REF_SELECT pin is pulled high.

[0118] The system configuration module is used to manage the experimental equipment comprehensively, including equipment initialization, calibration, and connection status monitoring. It can also perform basic system settings, such as sampling frequency, data format, storage path, etc., to ensure the accuracy and consistency of data collection.

[0119] The real-time control module is used to control the experimental process in real time to ensure stable data collection. Through the preset control logic, it can accurately control the operating status of the experimental equipment, as well as the start, pause and end of data collection, so as to completely record all data in the experimental process;

[0120] Real-time display The real-time display module provides a friendly interface design. Through charts, curves, numbers and other forms, the module can display the dynamic changes of experimental data in real time, helping users to monitor the experimental process in real time and quickly find potential problems;

[0121] The data management module focuses on the query and management of historical data and has a data retrieval function, allowing users to easily query previous data files. At the same time, the data management module is also responsible for operations such as data backup, recovery and export to ensure data security and availability. At the same time, the module realizes real-time storage and long-term preservation of experimental data through storage algorithms and storage devices.

[0122] In a further embodiment, the host computer program is implemented through a VISA interface module. After VISASerial configures the communication, VISA Write is used to send data, and VISA Read is used to receive data. The information transmitted by Bluetooth is received in the form of a string, and is output to the host computer wheel force decoupling program for calculation through a scanning string function. The calculated real wheel force is displayed and stored on the host computer interface. After the serial port is used, VISA Close is used to close the communication with the lower computer.

[0123] Working principle description: The strain gauge is deformed during movement, which in turn causes corresponding changes in the output voltage in the channel, and finally causes the output of the bridge circuit to change. Then the corresponding relationship between the voltage and the force value is determined through calibration experiments. The angle acquisition module is responsible for the angle data of the wheel. The angle data is used for rotational decoupling, thereby realizing the measurement of runway load data. The steps are as follows:

[0124] Step 1: Establish the input-output relationship model between the axes corresponding to the multiple axes of the sensor, that is, the multiple channels, and solve the relationship between the output voltage data of each channel of the sensor and the actual force through calibration experiments;

[0125] The relationship between the multi-channel voltage output and the multi-dimensional force output of the wheel force sensor can be expressed as:

[0126] f=Cv (3)

[0127] Where, f = [f x ,f z ,m y ] T is the multi-dimensional force output of the sensor, that is, the multi-dimensional force output corresponding to the multi-channel measured in the strain gauge bridge module, v = [v x ,v z ,v y ] T is the multi-channel voltage output, C is the calibration matrix;

[0128] It is necessary to solve the calibration matrix C using the least squares method based on the calibration experimental data, as shown below:

[0129] C=FV -1 (4)

[0130] Where F=[f1,···,f n ] is the multi-channel load data in the calibration experiment; V = [v1,···,v n ] is the corresponding voltage response data, where n is the number of channels;

[0131] Step 2: The sensor output needs to be rotationally decoupled to obtain the wheel force in the wheel coordinate system;

[0132] According to the principle of force coordinate decomposition and the measured rotation angle, the sensor output can be converted into six-dimensional force in wheel coordinates by the following formula:

[0133] F w =R(θ)·F e (5)

[0134] in is the force in the wheel coordinate system, is the force in the elastic body coordinate system, is the rotation matrix;

[0135] Then, the wheel angle measured by the angle acquisition module is used to convert the force in the elastic body coordinate system to the wheel coordinate system to complete the rotational decoupling and realize the measurement of runway load data.

[0136] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various equivalent transformations can be made to the technical scheme of the present invention, and these equivalent transformations all belong to the protection scope of the present invention.

Claims

1. Aircraft landing gear test wheel force sensor, characterized by: include: The wheel force sensor includes a wheel shaft, a shaft sleeve sleeved on the wheel shaft, a force sensor elastic body sleeved on the shaft sleeve, a left wheel hub and a right wheel hub symmetrically arranged on both sides of the force sensor elastic body and connected to the force sensor elastic body, and a fixing part for fixing the left wheel hub and the right wheel hub; The force sensor elastic body includes an inner ring sleeved on the shaft sleeve, 8 elastic strain beams uniformly arranged on the circumference of the inner ring, an outer ring for connecting the elastic strain beams, and a strain gauge bridge module attached to the elastic beams of the elastic body. The left wheel hub and the right wheel hub have the same structure and are both split structures, including a bearing seat and a wheel hub; An outer gear ring is provided on one side of the bearing seat, and a gear ring is provided on the inner wall of the inner ring. The bearing seat is connected to the inner ring by meshing the outer gear ring with the gear ring, and the inner wall of the outer gear ring abuts against the outer wall of the sleeve; The outer ring is provided with at least three bolt holes in the axial direction, and a support seat is provided on the inner wall of the hub, and the hub is fixed by using bolts passing through the bolt holes and the bolt holes on the outer ring; The fixing part includes a bearing located in the bearing seat and sleeved on the shaft sleeve, a bearing washer abutting against the bearing, a bearing end cover connected to the bearing washer, a nut washer sleeved on the machine wheel shaft, and a slot nut for fixing the bearing end cover on the machine wheel shaft; During operation, the wheel hub transmits force to the outer ring in the force sensor elastic body through bolt connection, and the outer ring transmits force to the inner ring in the force sensor elastic body through the strain beam; during the transmission process, the force sensor elastic body is deformed to complete the measurement work.

2. The information acquisition system for the wheel force sensor for testing aircraft landing gear according to claim 1 is characterized by: The information acquisition system includes an acquisition and conditioning unit connected to the wheel force sensor, and a data acquisition and analysis host computer connected to the acquisition and conditioning unit; The acquisition and conditioning unit includes a control module and a power module, an analog-to-digital conversion module, a communication module and a turning angle module that interact bidirectionally with the control module, and a signal conditioning module that interacts with the analog-to-digital conversion module; The data acquisition and analysis host computer includes four sub-function modules: system configuration, real-time control, real-time display and data management; The acquisition and conditioning unit is installed on one side of the elastic body and fixed by bolts, and is used to acquire the voltage at both ends of the strain gauge.

3. The information acquisition system for the wheel force sensor for testing aircraft landing gear according to claim 2 is characterized by: The strain gauge bridge module includes resistors R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, R15 and R16; Each elastic strain beam is provided with two resistors, and the installation order of the resistors in a clockwise direction is resistor R2, resistor R1, resistor R16, resistor R15, resistor R8, resistor R7, resistor R14, resistor R13, resistor R6, resistor R5, resistor R12, resistor R11, resistor R4, resistor R3, resistor R10, resistor R9; Wherein, one end of the resistor R1 is respectively connected to one end of the resistor R5, one end of the resistor R3, one end of the resistor R7, one end of the resistor R9, one end of the resistor R10 and the positive electrode of the input voltage, the other end of the resistor R1 is connected to one end of the resistor R6, the other end of the resistor R6 is respectively connected to the negative electrode of the output voltage, one end of the resistor R2, one end of the resistor R8, one end of the resistor R4, one end of the resistor R16 and one end of the resistor R15, the other end of the resistor R2 is connected to one end of the resistor R5, the other end of the resistor R8 is connected to the other end of the resistor R3, the other end of the resistor R4 is connected to the other end of the resistor R7, the other end of the resistor R16 is connected to one end of the resistor R14, the other end of the resistor R14 is connected to one end of the resistor R11, the other end of the resistor R11 is connected to the other end of the resistor R9, the other end of the resistor R15 is connected to one end of the resistor R13, the other end of the resistor R13 is connected to one end of the resistor R12, and the other end of the resistor R12 is connected to the other end of the resistor R10; Then the channel voltage difference between the connection point of resistor R1 and resistor R6 and the connection point of resistor R5 and resistor R2 is calculated as ΔU Fz , measure the channel voltage difference between the connection of resistor R3 and resistor R8 and the connection of resistor R4 and resistor R7 as ΔU Fx , and the channel voltage difference at the connection between resistor R11 and resistor R14 and at the connection between resistor R13 and resistor R12 is ΔU My , then ΔU Fz , ΔU Fx and ΔU My The value is transmitted to the acquisition and conditioning unit.

4. The information acquisition system for the wheel force sensor for testing aircraft landing gear according to claim 3 is characterized by: The elastic body of the force sensor should be subjected to finite element analysis results to determine the pasting position of the strain gauge, and the strength should be checked by the maximum shear stress theory. The criteria are: Among them, σ1 and σ3 represent the maximum normal stress and neutral stress at each point inside the object respectively; Represents the yield strength of the material.

5. The information acquisition system for the wheel force sensor for testing aircraft landing gear according to claim 4 is characterized by: According to the finite element results, f x 、f z and m y Strain analysis is performed when the three forces and moments act alone. According to the principle of mechanical superposition, the micro-deformation of the structure is composed of three basic deformations, namely tension, compression, bending and torsion, or their combination and superposition. Therefore, the output value of the wheel force multi-channel is: Where f x 、f z and m y They are ΔU Fx , ΔU Fz and ΔU My The force output corresponding to the measured channel; σ i (i=1-16) is the strain gauge strain corresponding to the serial number; k1, k2 and k3 are calibration coefficients; according to the designed layout and bridge assembly method, when each component of the three-dimensional force is loaded separately, the output of the remaining channels is close to 0.

6. The information acquisition system for wheel force sensors for testing aircraft landing gear according to claim 5, characterized in that: The analog-to-digital conversion module in the acquisition and conditioning unit is an A / D conversion module, the communication module is a Bluetooth communication module, and the control module is an STM32 control module; The power module described therein realizes power supply to other parts of the acquisition system through various buck and voltage stabilizing chips. The power module uses a 12V lithium battery as a power supply device, and then uses different buck chips to reduce its voltage to 5V, and then reduces the 5V voltage to 3.3V and 2.5V, of which the 2.5V voltage provides a reference voltage for the signal conditioning module; The signal conditioning module realizes zeroing, amplification and filtering of the bridge output and transmits the processed bridge output signal to the A / D conversion module, wherein the signal conditioning module is provided with three; The A / D conversion module realizes analog-to-digital conversion of the signal conditioning circuit and outputs the sensor data to the STM32 control module through the SPI bus; The angle acquisition module is responsible for transmitting the collected wheel angle information to the STM32 control module; The STM32 control module packages the data according to the designed communication protocol and sends it to the host computer via Bluetooth communication to complete the data collection.

7. The information acquisition system for wheel force sensors for aircraft landing gear testing according to claim 6 is characterized by: The signal conditioning module includes an operational amplifier U1, a resistor R17, a resistor R18, a resistor R19, a resistor R20, a capacitor C1, a capacitor C7, a capacitor C8 and a sliding resistor VR1, and the model of the operational amplifier U1 is AD620; Wherein a first pin of the operational amplifier U1 is connected to one end of the resistor R20, and the other end is connected to the eighth pin of the operational amplifier U1; a second pin of the operational amplifier U1 is respectively connected to one end of the resistor R19, one end of the capacitor C1 and the connection point between the resistor R5 and the resistor R2 in the strain bridge module; the other end of the resistor R19 is connected to a first pin of a sliding rheostat VR1; a second pin of the sliding rheostat VR1 is connected to one end of a resistor R18; the other end of the resistor R18 is connected to the connection point between the resistor R1 and the resistor R6, the other end of the capacitor C1 and the third pin of the operational amplifier U1; the third pin of the sliding rheostat VR1 is respectively connected to the seventh pin of the operational amplifier U1 and one end of the capacitor C1; a sixth pin of the operational amplifier U1 is connected to one end of the resistor R17, and the other end of the resistor R17 is connected to one end of the capacitor C8; The other ends of the capacitor C7 and the capacitor C8 are grounded, and the fourth pin of the operational amplifier U1 is grounded; The fifth pin of the operational amplifier U1 is connected to the regulated 2.5V voltage in the power module.

8. The information acquisition system for wheel force sensors for testing aircraft landing gear according to claim 7, characterized in that: The A / D conversion module includes an integrated circuit U9, a resistor R24, a resistor R26, a capacitor C40, a capacitor C30, a capacitor C31, a capacitor C34, a capacitor C35, a capacitor C36, a capacitor C37, an inductor L4, and an inductor L5; Among them, the twenty-third pin of the integrated circuit U9 is respectively connected to the 3.3V voltage in the power module and one end of the capacitor C30, the forty-fourth and forty-fifth pins of the integrated circuit U9 are connected and then connected to one end of the capacitor C31, the thirty-sixth pin of the integrated circuit U9 is connected to one end of the capacitor C34, the thirty-ninth pin of the integrated circuit U9 is connected to one end of the capacitor C35, the first pin, the forty-eighth, the thirty-seventh and the thirty-eighth pins of the integrated circuit U9 are connected and then connected to one end of the inductor L4 and one end of the capacitor C36, the other end of the inductor L4 is connected to one end of the capacitor C37 and one end of the inductor L5, the sixth pin of the integrated circuit U9 is respectively connected to one end of the resistor R24 ​​and the resistor R26, and the forty-second pin of the integrated circuit U9 is connected to one end of the capacitor C40; The seventh and thirty-fourth pins of the integrated circuit U9 and the other end of the resistor R24 ​​are respectively connected to the stabilized 3.3V voltage in the power module; The other end of capacitor C30, the other end of capacitor C31, the other end of capacitor C34, the other end of capacitor C35, the other end of capacitor C36, the other end of capacitor C37, the other end of inductor L5, the other end of resistor R26, and the other end of capacitor C40 are grounded respectively.

9. The information acquisition system for wheel force sensors for testing aircraft landing gear according to claim 8, characterized in that: The system configuration module is used to manage the experimental equipment comprehensively, including equipment initialization, calibration, and connection status monitoring. It can also perform basic system settings, such as sampling frequency, data format, and storage path, to ensure the accuracy and consistency of data collection. The real-time control module is used to control the experimental process in real time to ensure stable data collection. Through the preset control logic, it can accurately control the operating status of the experimental equipment, as well as the start, pause and end of data collection, so as to completely record all data in the experimental process; Real-time display The real-time display module provides a friendly interface design. Through charts, curves, and numbers, the module can display the dynamic changes of experimental data in real time, helping users to monitor the experimental process in real time and quickly discover potential problems; The data management module focuses on the query and management of historical data and has a data retrieval function, allowing users to easily query previous data files. At the same time, the data management module is also responsible for data backup, recovery and export operations to ensure data security and availability. At the same time, the module realizes real-time storage and long-term preservation of experimental data through storage algorithms and storage devices.

10. A wheel force decoupling method based on the information acquisition system of the wheel force sensor for testing aircraft landing gear according to any one of claims 2 to 9, characterized in that: include, Step 1: Establish the input-output relationship model between the axes corresponding to the multiple axes of the sensor, that is, the multiple channels, and solve the relationship between the output voltage data of each channel of the sensor and the actual force through calibration experiments; The relationship between the multi-channel voltage output and the multi-dimensional force output of the wheel force sensor can be expressed as: f=Cv (3) Where, f = [f x ,f z ,m y ] T is the multi-dimensional force output of the sensor, that is, the multi-dimensional force output corresponding to the multi-channel measured in the strain gauge bridge module, v = [v x ,v z ,v y ] T is the multi-channel voltage output, C is the calibration matrix; It is necessary to solve the calibration matrix C using the least squares method based on the calibration experimental data, as shown below: C=FV -1 (4) Where F=[f1,···,f n ] is the multi-channel load data in the calibration experiment; V = [v1,···,v n ] is the corresponding voltage response data, where n is the number of channels; Step 2: The sensor output needs to be rotationally decoupled to obtain the wheel force in the wheel coordinate system; According to the principle of force coordinate decomposition and the measured rotation angle, the sensor output can be converted into six-dimensional force in wheel coordinates by the following formula: F w =R(θ)·F e (5) in is the force in the wheel coordinate system, is the force in the elastic body coordinate system, is the rotation matrix; Then, the wheel angle measured by the angle acquisition module is used to convert the force in the elastic body coordinate system to the wheel coordinate system to complete the rotational decoupling and realize the measurement of runway load data.

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