Light aircraft landing gear structure on-line health monitoring device and method

Abstract

The application provides a light aircraft landing gear structure online health monitoring device and method, and relates to the technical field of structure health monitoring. A pre-crack is installed on the hole edge of a landing gear yoke mounting hole, and a statistical test of the cycle number of the landing gear yoke with different crack forms reaching failure and damage under a given load is carried out by using a testing machine, so as to establish the relationship among different crack forms, ultrasonic waveforms and the residual life of the landing gear yoke corresponding to the two cases of normal landing and hard landing. The online health monitoring of the landing gear yoke mounting hole of the light aircraft is carried out during flight, the ultrasonic waveforms returned from the landing gear yoke mounting hole are monitored by using the light aircraft landing gear structure online health monitoring device, and then the residual life of the landing gear yoke at this moment is inferred and the disposal scheme of replacing or repairing the landing gear yoke is determined in combination with the above relationship, so that the health monitoring problem of the light aircraft landing gear structure is solved.

Description

Technical Field

[0001] This invention relates to the field of structural health monitoring technology, and in particular to an online health monitoring device and method for the landing gear structure of a light aircraft. Background Technology

[0002] With the increasing application of light aircraft in training, tourism, agriculture, and other fields, the safety of light aircraft has become an unavoidable topic. Currently, fault detection for light aircraft is mainly completed on the ground. After landing, technicians use non-destructive testing techniques such as ultrasonic testing, magnetic particle testing, and X-rays to inspect and detect flaws. This inspection process often requires disassembling aircraft parts and placing them in a special testing environment, which significantly reduces the efficiency of aircraft use and increases labor costs. In addition, light aircraft may experience "hard landings" due to improper operation. Compared to normal landings, hard landings are more likely to cause cracks at the edges of critical components such as landing gear wheel fork mounting holes. These cracks are potential hazards leading to landing gear wheel fork fracture failure. However, from an economic perspective, if the cracks at the landing gear wheel fork mounting holes caused by a hard landing do not have a decisive impact on the overall structural performance, the landing gear wheel fork can still be used. Therefore, systems or methods capable of real-time online health monitoring of critical structures of light aircraft have become a research focus.

[0003] Current technologies for online health monitoring of aircraft structures primarily rely on piezoelectric sensors for automatic damage assessment. However, this method inevitably introduces measurement biases for localized structural damage, which can impact aircraft safety evaluations. Technicians have also proposed using transmitted and received energy waves for health monitoring, identifying structural anomalies through waveform or impedance changes, but they haven't addressed how to handle these anomalies after identification. Besides these existing methods, strain data under different attitudes can be acquired to generate stress statistics, assessing the degree of structural damage. Real-time monitoring of strain signals allows for damage assessment using statistical data and finite element models. However, since finite element models still deviate from experimentally obtained data models, it's impossible to determine whether the assessed structure can continue to be used. Summary of the Invention

[0004] To address the shortcomings of the existing technologies, this invention proposes an online health monitoring device and method for light aircraft landing gear structures, aiming to solve the health monitoring problem of light aircraft landing gear structures.

[0005] The first aspect of this invention provides an online health monitoring device for the landing gear structure of a light aircraft, the device comprising: a test fixture, a landing gear wheel fork, and an online health monitoring system;

[0006] The test fixture is used to fix the landing gear wheel fork according to a predetermined installation method, and is simultaneously fixedly connected to the test machine and the ground;

[0007] The landing gear wheel fork is used as a test piece to conduct a statistical test on the number of cycles that the landing gear wheel fork undergoes before it fails under a given load.

[0008] The online health monitoring system is fixedly connected to the landing gear wheel fork and is used to perform online health monitoring of the landing gear wheel fork and predict the remaining life of the landing gear wheel fork during conventional landing or hard landing based on the test results.

[0009] Furthermore, the test fixture includes a first connector, a support arm, a second connector, and a third connector; the center point of the first connector is fixedly connected to one end of the support arm by a fastener, and the other end of the support arm is fixedly connected to the second connector by a fastener; the second connector and the third connector are connected by the landing gear wheel fork; the two ends of the first connector are used as connection ends to the testing machine, and the two ends of the third connector are used as connection ends to the ground;

[0010] There are two landing gear wheel forks, which are symmetrically installed on both sides of the test fixture; both ends of each landing gear wheel fork are fixedly connected to the second connector and the third connector respectively by fasteners; the top of the landing gear wheel fork is provided with a landing gear wheel fork mounting hole;

[0011] The online health monitoring system includes a telescopic support column, a positioning rod one, a coupling agent connecting rod, a coupling agent nozzle, a positioning rod two, an ultrasonic connecting rod, and an ultrasonic probe; wherein the telescopic support column, positioning rod one, positioning rod two, and ultrasonic connecting rod all have built-in motors embedded in them;

[0012] One end of the retractable strut is fixedly connected to the side of the landing gear wheel fork with a landing gear wheel fork mounting hole, and extends or retracts under the drive of a built-in motor according to the actual needs of health monitoring; both positioning rod one and positioning rod two are connected to the other end of the retractable strut, and rotate, extend or retract around the retractable strut under the drive of their respective built-in motors; the other end of positioning rod one is fixed to the coupling agent nozzle via a coupling agent connecting rod; the length of the coupling agent connecting rod is fixed; the coupling agent nozzle is used to spray coupling agent onto the surface of the landing gear wheel fork; the other end of positioning rod two is fixedly connected to an ultrasonic probe via an ultrasonic connecting rod; the ultrasonic connecting rod extends or retracts under the drive of a built-in motor; the ultrasonic probe is used to emit ultrasonic waves to the monitoring area and is electrically connected to the ultrasonic testing equipment;

[0013] Furthermore, each of the built-in motors is electrically connected to a control device pre-installed on the light aircraft's control panel via a built-in motor controller, which is used to receive commands issued by the control device and control the motors to drive them.

[0014] The second aspect of this invention proposes an online health monitoring method for the landing gear structure of a light aircraft, the method comprising the following two stages:

[0015] During the test design phase, cracks were pre-introduced at the edge of the mounting holes of the landing gear wheel forks, and the ultrasonic waveforms corresponding to different crack types were detected to establish the relationship between crack types and ultrasonic waveforms. The test machine was used to conduct tests on the number of cycles required for landing gear wheel forks with different crack types to reach failure under given average loads for conventional or hard landings. Based on the test results, the relationship between different crack types, ultrasonic waveforms, and the remaining life of the landing gear wheel forks under both conventional and hard landing conditions was established.

[0016] During the online health monitoring phase, the landing gear wheel fork mounting holes of the light aircraft are monitored online during flight. The ultrasonic wave pattern returned from the landing gear wheel fork mounting holes is obtained using the online health monitoring device for the landing gear structure of the light aircraft. The crack pattern of the landing gear wheel fork mounting holes at that moment is inferred based on the relationship between the crack pattern and the ultrasonic wave pattern. By combining the relationship between the different crack patterns, ultrasonic wave pattern and remaining life of the landing gear wheel fork under the two conditions of conventional landing and hard landing, the remaining life of the landing gear wheel fork at that moment is inferred, and the disposal plan for replacing or repairing the landing gear wheel fork is determined.

[0017] Furthermore, the experimental design phase includes the following steps:

[0018] Step 1.1: Pre-fabricate cracks at the edge of the landing gear wheel fork mounting holes;

[0019] Step 1.2: Using the crack form exhibited by the pre-existing crack as the experimental variable, calibrate the parameters of the ultrasonic testing equipment according to the different crack forms of the pre-existing crack, and use the ultrasonic testing equipment to detect the pre-existing crack to obtain the ultrasonic waveforms corresponding to different crack forms.

[0020] Step 1.3: Assemble the test fixture and landing gear wheel fork in the online health monitoring device for the landing gear structure of light aircraft, and fix the test fixture to both the test machine and the ground simultaneously;

[0021] Step 1.4: Design and conduct a statistical test to determine the number of cycles required for the landing gear wheel fork to fail under a given load, and record the test results;

[0022] The statistical test process is as follows: using a test machine, load spectra are applied to the landing gear wheel fork according to the expected equivalent force of hard landing and conventional landing, and the number of cycles when the landing gear wheel fork reaches failure under different crack forms is counted.

[0023] Step 1.5: Based on the test results of Step 1.4 and the ultrasonic patterns corresponding to different crack types obtained in Step 1.2, fit the relationship between different crack types, ultrasonic patterns and remaining life of landing gear wheel forks for conventional landing and hard landing respectively.

[0024] Furthermore, the crack type includes: crack orientation, crack size, and number of cracks;

[0025] The online health monitoring phase includes the following steps:

[0026] Step 2.1: Install the online health monitoring system of the light aircraft landing gear structure online health monitoring device on the landing gear wheel fork of the light aircraft. During the flight of the light aircraft, the command to carry out health monitoring of the landing gear wheel fork mounting holes is issued manually or at regular intervals through the control device preset in the control panel.

[0027] Step 2.2: After the online health monitoring system receives the instruction, the telescopic support column is extended or shortened by the built-in motor to coarsely adjust the position of the coupling agent nozzle and the ultrasonic probe;

[0028] Step 2.3: Use positioning rod one to fine-tune the position of the coupling agent nozzle to ensure that the coupling agent nozzle sprays the coupling agent evenly onto the surface of the landing gear wheel fork; use positioning rod two and ultrasonic connecting rod to fine-tune the position of the ultrasonic probe to ensure that the ultrasonic probe uses the coupling agent to monitor the cracks in the mounting holes of the landing gear wheel fork.

[0029] Step 2.4: Use an ultrasonic probe to emit ultrasonic waves toward the crack at the landing gear wheel fork mounting hole, and return the detection waveform to the ultrasonic testing equipment through the ultrasonic probe. By comparing the detection waveform with the ultrasonic waveforms corresponding to different known crack types, the crack type of the landing gear wheel fork mounting hole at that moment can be deduced.

[0030] Step 2.5: Combining the fitting results from Step 1.5, obtain the remaining life of the landing gear wheel fork during conventional or hard landing, corresponding to the crack pattern of the landing gear wheel fork mounting hole, and then determine the replacement or repair solution for the landing gear wheel fork.

[0031] The beneficial effects of adopting the above technical solution are as follows:

[0032] Compared to traditional non-destructive testing, the device of this invention does not require disassembling aircraft parts during the health monitoring of aircraft landing gear wheel forks. It can perform online monitoring, which greatly improves the efficiency of aircraft use, reduces labor costs, and enables pilots or managers to detect problems in the aircraft structure in real time and take timely remedial measures.

[0033] The method of this invention can accurately determine the relationship between different crack types, ultrasonic type, and remaining life through designed experiments, and use it as the basis for judging the crack condition of the landing gear wheel fork mounting hole.

[0034] The device and method of this invention conduct health monitoring of the landing gear wheel fork mounting holes by issuing timed or manual commands. Through ultrasonic testing, technicians obtain the crack type and remaining life, and then take corresponding measures, namely, replacing or repairing the landing gear wheel fork. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the structure of an online health monitoring device for a light aircraft landing gear structure in this embodiment;

[0036] Figure 2 This is a schematic diagram illustrating the installation of an online health monitoring device for a light aircraft landing gear structure in this embodiment.

[0037] Figure 3 This is a schematic diagram of the landing gear wheel fork of a light aircraft in this embodiment;

[0038] Figure 4 This is a schematic diagram of the online health monitoring system in an online health monitoring device for a light aircraft landing gear structure according to this embodiment;

[0039] Figure 5 This is a flowchart of an online health monitoring method for a light aircraft landing gear structure according to this embodiment;

[0040] Wherein: 1-Connector 1, 2-Support arm, 3-Connector 2, 4-Landing gear wheel fork, 5-Connector 3, 6-Connection end to the testing machine, 7-Connection end to the ground, 8-Landing gear wheel fork mounting hole, 9-Telescopic support, 10-Positioning rod 1, 11-Coupled agent connecting rod, 12-Coupled agent nozzle, 13-Positioning rod 2, 14-Ultrasonic connecting rod, 15-Ultrasonic probe. Detailed Implementation

[0041] To facilitate understanding of this application, specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and embodiments. The following embodiments are illustrative of the invention but are not intended to limit its scope. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0042] The first aspect of this embodiment proposes an online health monitoring device for the landing gear structure of a light aircraft, such as... Figure 1-4 As shown, the device includes: a test fixture, a landing gear wheel fork 4, and an online health monitoring system;

[0043] The test fixture is used to fix the landing gear wheel fork 4 according to a predetermined installation method, and simultaneously fix it to the test machine and the ground.

[0044] The landing gear wheel fork 4 serves as a test piece for statistical testing of the number of cycles experienced by the landing gear wheel fork before it fails under a given load.

[0045] The online health monitoring system is fixedly connected to the landing gear wheel forks and is used to perform online health monitoring of the landing gear wheel forks and predict the remaining life of the landing gear wheel forks during conventional or hard landings based on the test results.

[0046] The test fixture includes connector 1, support arm 2, connector 2, and connector 3; the center point of connector 1 is fixedly connected to one end of support arm 2 by fasteners, and the other end of support arm 2 is fixedly connected to connector 2 by fasteners; connector 2 and connector 3 are connected by the landing gear wheel fork 4; the two ends of connector 1 are used as connection ends 6 to the test machine, and the two ends of connector 3 are used as connection ends 7 to the ground.

[0047] There are two landing gear wheel forks 4, which are symmetrically installed on both sides of the test fixture; both ends of each landing gear wheel fork 4 are fixedly connected to the second connector 3 and the third connector 5 respectively by fasteners; the top of the landing gear wheel fork 4 is provided with a landing gear wheel fork mounting hole 8.

[0048] The online health monitoring system includes a telescopic support column 9, a positioning rod 10, a coupling agent connecting rod 11, a coupling agent nozzle 12, a positioning rod 2 13, an ultrasonic connecting rod 14, and an ultrasonic probe 15; wherein the telescopic support column 9, the positioning rod 10, the positioning rod 2 13, and the ultrasonic connecting rod 14 are all equipped with built-in motors.

[0049] One end of the retractable strut 9 is fixedly connected to the side of the landing gear wheel fork with a landing gear wheel fork mounting hole, and extends or shortens under the drive of a built-in motor according to the actual needs of health monitoring; the first positioning rod 10 and the second positioning rod 13 are both connected to the other end of the retractable strut 9, and rotate, extend or shorten around the retractable strut 9 under the drive of their respective built-in motors; the other end of the first positioning rod 10 is fixed to the coupling agent nozzle 12 through a coupling agent connecting rod 11; the length of the coupling agent connecting rod 11 is fixed; the coupling agent nozzle 12 is used to spray coupling agent on the surface of the landing gear wheel fork; the other end of the second positioning rod 14 is fixedly connected to the ultrasonic probe 15 through an ultrasonic connecting rod 14; the ultrasonic connecting rod 14 extends or shortens under the drive of a built-in motor; the ultrasonic probe 15 is used to emit ultrasonic waves to the monitoring part and is electrically connected to the ultrasonic testing equipment.

[0050] The built-in motors are all electrically connected to the control device pre-installed on the light aircraft's control panel via built-in motor controllers, receiving commands from the control device and controlling the motors to drive them; the built-in motors are all powered by batteries or external power sources, and all have the ability to overcome their own weight and motion resistance during the monitoring process.

[0051] The coupling agent nozzle should have multiple outlet types suitable for spraying coupling agent, such as holes and slits, and should have an external connecting pipe to replenish the coupling agent.

[0052] The second aspect of this embodiment proposes an online health monitoring method for a light aircraft landing gear structure. This method utilizes the aforementioned online health monitoring device for a light aircraft landing gear structure, such as... Figure 5 As shown, it includes the following two stages:

[0053] During the test design phase, cracks were pre-introduced at the edge of the mounting holes of the landing gear wheel forks, and the ultrasonic waveforms corresponding to different crack types were detected to establish the relationship between crack types and ultrasonic waveforms. The test machine was used to conduct tests on the number of cycles required for landing gear wheel forks with different crack types to reach failure under given average loads for conventional or hard landings. Based on the test results, the relationship between different crack types, ultrasonic waveforms, and the remaining life of the landing gear wheel forks under both conventional and hard landing conditions was established.

[0054] During the online health monitoring phase, the landing gear wheel fork mounting holes of the light aircraft are monitored online during flight. The ultrasonic wave pattern returned from the landing gear wheel fork mounting holes is obtained using the online health monitoring device for the landing gear structure of the light aircraft. Then, based on the relationship between the crack pattern and the ultrasonic wave pattern, the crack pattern of the landing gear wheel fork mounting holes at that moment is inferred. Combining the relationship between the different crack patterns, ultrasonic wave pattern and remaining life of the landing gear wheel fork under the two conditions of conventional landing and hard landing, the remaining life of the landing gear wheel fork at that moment is inferred, and the disposal plan for replacing or repairing the landing gear wheel fork is determined.

[0055] The experimental design phase includes the following steps:

[0056] Step 1.1: Pre-fabricate cracks at the edge of the landing gear wheel fork mounting holes.

[0057] In this embodiment, pre-cracks are pre-formed at the edge of the landing gear wheel fork mounting hole 8. The pre-formed cracks are classified as follows: 1) According to geometric characteristics: surface cracks and through cracks; 2) According to crack shape: rectangular cracks, triangular cracks, and elliptical cracks; 3) According to crack location: pre-formed cracks in single-sided wheel fork mounting holes or pre-formed cracks in double-sided wheel fork mounting holes.

[0058] Step 1.2: Using the crack form exhibited by the pre-existing crack as the experimental variable, calibrate the parameters of the ultrasonic testing equipment according to the different crack forms of the pre-existing crack, and use the ultrasonic testing equipment to detect the pre-existing crack to obtain the ultrasonic waveforms corresponding to different crack forms.

[0059] The crack type includes: crack location, crack size, and number of cracks.

[0060] In this embodiment, the crack form exhibited by the pre-existing crack is used as the experimental variable. That is, any one of the parameters, such as crack orientation, crack size, and crack number, can be used as the experimental variable in the experiment, while the other two parameters remain unchanged. Different crack forms are determined based on the pre-existing crack. For example, the crack form is determined to be a 2mm triangular through crack based on the pre-existing crack. The pre-existing crack is detected using an ultrasonic testing device to obtain the ultrasonic waveforms corresponding to different crack forms.

[0061] Step 1.3: Assemble the test fixture and landing gear wheel fork in the online health monitoring device for the landing gear structure of light aircraft, and fix the test fixture to the test machine and the ground at the same time.

[0062] The testing machine is a standard or non-standard testing machine with force measurement and corresponding control software.

[0063] In this embodiment, the connector 1, support arm 2, connector 3, landing gear wheel fork with pre-existing cracks 4, and connector 5 of the online health monitoring device for the landing gear structure of a light aircraft are sequentially connected and assembled. The connection end 6 of the device to the test machine is fixedly connected to the clamp of the test machine, and the connection end 7 of the device to the ground is fixedly connected to the ground.

[0064] Step 1.4: Design and conduct a statistical test to determine the number of cycles required for the landing gear wheel fork to fail under a given load, and record the test results.

[0065] The statistical test process is as follows: using a test machine, load spectrums are applied to the landing gear wheel fork according to the expected equivalent force of hard landing and conventional landing, and the number of cycles when the landing gear wheel fork reaches failure under different crack forms is counted.

[0066] Step 1.5: Based on the test results of Step 1.4 and the ultrasonic patterns corresponding to different crack types obtained in Step 1.2, fit the relationship between the different crack types, ultrasonic patterns and remaining life of the landing gear wheel forks for conventional landing and hard landing respectively.

[0067] In this embodiment, the remaining life of the landing gear wheel fork is also expressed as the remaining number of landings for the landing gear wheel fork.

[0068] The online health monitoring phase includes the following steps:

[0069] Step 2.1: Install the online health monitoring system from the online health monitoring device for the landing gear structure of the light aircraft onto the landing gear wheel forks of the light aircraft. During the flight of the light aircraft, the system can issue commands to conduct health monitoring on the mounting holes of the landing gear wheel forks manually or at set intervals through the preset control device on the control panel.

[0070] Step 2.2: After the online health monitoring system receives the instruction, the telescopic support column is extended or shortened by the built-in motor to coarsely adjust the position of the coupling agent nozzle and the ultrasonic probe.

[0071] In this embodiment, the telescopic support motor drives the telescopic support 9 to shorten by 2mm, and coarsely adjusts the position of the coupling agent nozzle 12 and the ultrasonic probe 15.

[0072] Step 2.3: Use positioning rod one to fine-tune the position of the coupling agent nozzle, and use positioning rod two and ultrasonic connecting rod to fine-tune the position of the ultrasonic probe.

[0073] The process of finely adjusting the position of the coupling agent nozzle using the positioning rod is as follows: the built-in motor of the positioning rod drives the positioning rod to rotate, extend or shorten, finely adjusting the position of the coupling agent nozzle to ensure that the coupling agent nozzle sprays the coupling agent evenly onto the surface of the landing gear wheel fork.

[0074] The process of finely adjusting the position of the ultrasonic probe using the second positioning rod and the ultrasonic connecting rod is as follows: the second positioning rod is driven to rotate, extend or shorten by its built-in motor, and the ultrasonic connecting rod is driven to extend or shorten by its built-in motor, thereby achieving the purpose of finely adjusting the position of the ultrasonic probe, thus ensuring that the ultrasonic probe uses the coupling agent to monitor the cracks in the landing gear wheel fork mounting holes.

[0075] In this embodiment, positioning rod 10 rotates 2° clockwise around telescopic support 9 and shortens by 0.2mm, fine-tuning the position of coupling agent nozzle 12 to ensure that the coupling agent can be evenly sprayed onto the surface of landing gear wheel fork 4 through the coupling agent nozzle; positioning rod 13 rotates 2° clockwise around telescopic support 9 and shortens by 0.3mm, ultrasonic connecting rod extends by 0.1mm, fine-tuning the position of ultrasonic probe 15 to ensure that ultrasonic probe 15 can monitor the crack condition of landing gear wheel fork mounting hole 8 using coupling agent.

[0076] Step 2.4: Use an ultrasonic probe to emit ultrasonic waves towards the crack at the landing gear wheel fork mounting hole, and return the detection waveform to the ultrasonic testing equipment through the ultrasonic probe. By comparing the detection waveform with the ultrasonic waveforms corresponding to different known crack types, the crack type of the landing gear wheel fork mounting hole at that moment can be deduced.

[0077] In this embodiment, ultrasonic testing methods can be classified into various types based on the waveform emitted by the ultrasonic probe, such as longitudinal wave method, transverse wave method, surface wave method, plate wave method, and climbing wave method; the ultrasonic probe can be configured as a multi-probe type according to the actual testing needs.

[0078] In this embodiment, the ultrasonic probe 15 returns the monitored waveform and compares it with the ultrasonic waveforms corresponding to different known crack types, thus deducing that the crack type of the landing gear wheel fork mounting hole at this time is a 2mm triangular through crack.

[0079] Step 2.5: Combining the fitting results from Step 1.5, obtain the remaining life of the landing gear wheel fork during conventional or hard landing, corresponding to the crack pattern of the landing gear wheel fork mounting hole, and then determine the replacement or repair solution for the landing gear wheel fork.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope defined by the claims of the present invention.

Claims

1. An apparatus for online health monitoring of light aircraft landing gear structure, characterized by, The device comprises a test fixture, a landing gear yoke, and an online health monitoring system. The test fixture is used to fix the landing gear yoke in a predetermined installation mode and is fixedly connected with a testing machine and the ground. The test fixture comprises a connecting piece one, a supporting arm, a connecting piece two, and a connecting piece three. The center point of the connecting piece one is fixedly connected with one end of the supporting arm through a fastener, and the other end of the supporting arm is fixedly connected with the connecting piece two through a fastener. The connecting piece two and the connecting piece three are connected through the landing gear yoke. The two ends of the connecting piece one are used as the connecting end with the testing machine, and the two ends of the connecting piece three are used as the connecting end with the ground. The landing gear yoke is used to conduct a statistical test of the cycle number experienced by the landing gear yoke until it is destroyed under a given load. The landing gear yoke is symmetrically installed on both sides of the test fixture.

2. The online health monitoring device for light aircraft landing gear structure according to claim 1, characterized in that, The two ends of each landing gear yoke are fixedly connected with the connecting piece two and the connecting piece three through fasteners, respectively.

3. A method for online health monitoring of a light aircraft landing gear structure, using the online health monitoring device for a light aircraft landing gear structure according to any one of claims 1-2, characterized in that, A landing gear yoke mounting hole is formed in the top of the landing gear yoke. The online health monitoring system is fixedly connected with the landing gear yoke and is used to conduct online health monitoring of the landing gear yoke and predict the remaining life of the landing gear yoke during regular landing or hard landing according to the test results. The online health monitoring system comprises a telescopic support, a positioning rod one, a coupling agent connecting rod, a coupling agent spray head, a positioning rod two, an ultrasonic wave connecting rod, and an ultrasonic wave probe. The telescopic support, the positioning rod one, the positioning rod two, and the ultrasonic wave connecting rod are embedded with built-in motors. One end of the telescopic support is fixedly connected with one side of the landing gear yoke in which a landing gear yoke mounting hole is formed and is elongated or shortened under the driving of the built-in motor according to the actual needs of health monitoring. The positioning rod one and the positioning rod two are connected on the other end of the telescopic support and are rotated, elongated, or shortened around the telescopic support under the driving of the respective built-in motors. The other end of the positioning rod one is fixed to the coupling agent spray head through the coupling agent connecting rod. The length of the coupling agent connecting rod is fixed. The coupling agent spray head is used to spray coupling agent on the surface of the landing gear yoke. The other end of the positioning rod two is fixedly connected with the ultrasonic wave probe through the ultrasonic wave connecting rod. The ultrasonic wave connecting rod is elongated or shortened under the driving of the built-in motor. The ultrasonic wave probe is used to emit ultrasonic waves to the monitoring site and is electrically connected with an ultrasonic detection device. The built-in motors are electrically connected with the control device preset on the light aircraft control panel through the built-in motor controllers and are used to receive the instructions issued by the control device and control the driving of the motors. The method comprises two stages as follows. In the test design stage, the relationship between the crack form and the ultrasonic waveform is established by pre-cracking the hole edge of the landing gear wheel fork mounting hole and detecting the ultrasonic waveform corresponding to different crack forms; the test is performed by using a testing machine to obtain the cycle number of the landing gear wheel fork with different crack forms when it reaches failure under the given average load of normal landing or hard landing, and the relationship between the crack form, the ultrasonic waveform and the remaining life of the landing gear wheel fork corresponding to different crack forms under the conditions of normal landing and hard landing is established according to the test results; In the online health monitoring stage, the online health monitoring of the landing gear wheel fork mounting hole is performed during the flight of the light aircraft, the ultrasonic waveform returned from the landing gear wheel fork mounting hole is obtained by using the light aircraft landing gear structure online health monitoring device, and then the crack form of the landing gear wheel fork mounting hole at this moment is inferred according to the relationship between the crack form and the ultrasonic waveform, and the remaining life of the landing gear wheel fork at this moment is inferred and the disposal scheme of replacing or repairing the landing gear wheel fork is determined by combining the relationship between the crack form, the ultrasonic waveform and the remaining life of the landing gear wheel fork corresponding to different crack forms under the conditions of normal landing and hard landing.

4. The method of claim 3, wherein, The test design stage comprises the following steps: Step 1.1: Pre-cracking the hole edge of the landing gear wheel fork mounting hole; Step 1.2: Taking the crack form of the pre-crack as a test variable, calibrating the parameters of the ultrasonic detection equipment according to different crack forms of the pre-crack, detecting the pre-crack by using the ultrasonic detection equipment, and obtaining the ultrasonic waveform corresponding to different crack forms; Step 1.3: Assembling the test fixture in the light aircraft landing gear structure online health monitoring device and the landing gear wheel fork, and simultaneously connecting the test fixture with the testing machine and the ground; Step 1.4: Designing and performing a statistical test of the cycle number experienced by the landing gear wheel fork when it reaches failure under a given load, and recording the test results; Step 1.5: Fitting the relationship between the crack form, the ultrasonic waveform and the remaining life of the landing gear wheel fork corresponding to different crack forms under the conditions of normal landing and hard landing respectively according to the test results of step 1.4 and the ultrasonic waveform corresponding to different crack forms obtained in step 1.

2.

5. The method of claim 4, wherein, The crack form includes crack orientation, crack size and crack number.

6. The method of claim 4, wherein, The process of the statistical test is to use the testing machine to apply a load spectrum to the landing gear wheel fork according to the expected equivalent force of hard landing and normal landing respectively, and to count the cycle number of the landing gear wheel fork when it reaches failure under different crack forms.

7. The method of claim 6, wherein, The online health monitoring stage comprises the following steps: Step 2.1: Installing the online health monitoring system in the light aircraft landing gear structure online health monitoring device on the landing gear wheel fork of the light aircraft, and manually or automatically issuing an instruction to perform health monitoring on the landing gear wheel fork mounting hole through the pre-set control device in the flight panel during the flight of the light aircraft; Step 2.2: When the online health monitoring system receives the instruction, the telescopic support is driven by the built-in motor to extend or shorten, and the positions of the coupling agent nozzle and the ultrasonic probe are coarsely adjusted; Step 2.3: Fine-tune the position of the coupling agent spray head by using the positioning rod 1 to ensure that the coupling agent spray head uniformly sprays the coupling agent to the surface of the landing gear wheel fork; fine-tune the position of the ultrasonic probe by using the positioning rod 2 and the ultrasonic connecting rod to ensure that the ultrasonic probe monitors the crack condition of the landing gear wheel fork mounting hole by using the coupling agent; Step 2.4: The ultrasonic probe emits ultrasonic waves to the crack at the landing gear wheel fork mounting hole, and returns the detection waveform to the ultrasonic detection equipment through the ultrasonic probe; by comparing the detection waveform with the known ultrasonic waveform corresponding to different crack forms, the crack form of the landing gear wheel fork mounting hole at this time is deduced; Step 2.5: Combine the fitting result in step 1.5 to obtain the remaining life of the landing gear wheel fork under the conventional landing or hard landing condition corresponding to the crack form of the landing gear wheel fork mounting hole at this time, and then determine the disposal scheme of replacing or repairing the landing gear wheel fork.

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