An aircraft landing gear shimmy test bench and test method

Abstract

The application discloses an airplane landing gear shimmy test bench and a test method, which comprises a main bench, a hanging basket system, a large flywheel, a flywheel driving system, an excitation device, and a follow-up displacement measurement system. The application can simulate the control effect of a damping system on the stability of a landing gear after the landing gear of different design configurations is subjected to an interference excitation force or an interference torque during the process of airplane takeoff, taxiing, landing and the like, has a short excitation time, can simulate real working conditions, can accurately detect the shimmy stability performance of the landing gear, continuously excites under the condition of continuously changing test states, and greatly improves work efficiency. The follow-up displacement measurement system designed in the application can keep the excitation force and the wheel shaft center always in the same horizontal plane, can apply torque control and torque excitation control, is suitable for the shimmy test of landing gears with different wheel shaft heights, different tire diameters and different excitation modes, and has certain universality.

Description

Technical Field

[0001] This invention relates to the field of aircraft landing gear testing technology, and in particular to an aircraft landing gear shimmy test bench and test method. Background Technology

[0002] Shimmy testing is a crucial step in the development of aircraft landing gear systems. It aims to verify the stability and vibration resistance of the landing gear under extreme conditions by simulating dynamic disturbances during aircraft taxiing. In the field of landing gear shimmy testing, the shimmy test bench and its testing methods directly affect the accuracy of test data and flight safety. Currently, aircraft landing gear shimmy test benches mainly employ fixed mechanical excitation or single-degree-of-freedom traction disturbance methods. These methods have significant shortcomings in terms of control precision, functional integration, and safety.

[0003] Chinese patent CN119551213A discloses a test bench for simulating the shimmy vibration of an aircraft nose landing gear during taxiing. The vibration excitation mechanism in this patent includes a lateral excitation hammer and a steering servo directional exciter. The lateral excitation hammer is mounted on the main frame and corresponds to the side of the nose landing gear, providing lateral excitation by striking the nose landing gear. The directional excitation hammer is mounted on the main frame and corresponds to the stress point of the nose landing gear, providing directional excitation to the nose landing gear. This simulates the vibration impact of a complex road surface on the aircraft's nose landing gear during taxiing, in order to test the vibration reduction performance of the nose landing gear. However, this device only applies excitation to the landing gear struts of small aircraft, lacking direct excitation to the landing gear axles during taxiing, thus compromising the simulation effect. Furthermore, the device has poor adaptability to different landing gear models and limited adjustability.

[0004] Chinese patent CN105730713A discloses an excitation method and device for testing aircraft landing gear shimmy during flight. During the test, as the aircraft taxis on the runway, the landing gear wheel to be excited rolls past the excitation device along a trapezoidal cross-section slope from one side of the device. This can apply left-side and negative-heading excitation to the nose landing gear. After the test, the excitation device needs to be removed, the runway restored to normal operational function. This method closely resembles the excitation experienced during actual aircraft flight; however, due to limitations in test site and methodology, the testing cost is high. Summary of the Invention

[0005] To address the shortcomings of the existing technology, this invention proposes a test bench that applies a shorter excitation time to the landing gear axle to simulate real working conditions, has low testing costs, is versatile, and can accurately detect the shimmy stability of the landing gear.

[0006] The technical solution of the present invention: an aircraft landing gear shimmy test bench, comprising: The main frame serves as the support and guide structure for the test bench; A suspended platform system for mounting and applying loads to the landing gear, the suspended platform system being able to move up and down along the main frame; The large flywheel provides a continuous tangential velocity to the landing gear and bears the vertical loads applied by the basket system; A flywheel drive system that provides power to the large flywheel; An excitation device is provided on one side of the landing gear wheel axle and connected to the landing gear wheel axle. The excitation device applies an instantaneous lateral excitation force to the landing gear wheel axle for a duration not exceeding 0.2s and a swing angle not exceeding 5°. A follow-up displacement measurement system measures the distance between the landing gear wheel axle and the large flywheel in real time, and controls the ground clearance of the excitation device in real time based on this distance, so that the relative position of the excitation device and the landing gear wheel axle remains unchanged.

[0007] In one embodiment, the suspended platform system includes a first crossbeam, a second crossbeam, and a servo hydraulic loading cylinder. The first crossbeam is fixed on the main frame, the second crossbeam is slidably mounted on the main frame, the first crossbeam is located above the second crossbeam, the servo hydraulic loading cylinder is mounted between the first crossbeam and the second crossbeam, and the landing gear is mounted on the lower surface of the second crossbeam.

[0008] In one embodiment, a wire displacement sensor is provided between the first crossbeam and the second crossbeam.

[0009] In one embodiment, the flywheel drive system includes at least a drive motor, a coupling, and a reducer. The drive motor and the reducer are connected via the coupling. The drive motor provides power to the flywheel, and the reducer is used to increase the output torque and match the flywheel speed requirements.

[0010] In one embodiment, the excitation device includes a hydrostatic support cylinder, a hydraulic servo system, a wire rope, and a fixed pulley. The hydraulic servo system provides power to the hydrostatic support cylinder. One end of the wire rope is connected to the landing gear wheel axle, and the other end of the wire rope passes around the fixed pulley and is connected to the hydrostatic support cylinder.

[0011] In one embodiment, the follow-up displacement measurement system includes an axle height sensor, a follow-up bracket, a movable enclosure, a motor, a transmission mechanism, and a host computer control system. The axle height sensor is disposed on the lower edge of the landing gear axle. The excitation device is mounted on the movable enclosure, which is slidably mounted on the follow-up bracket. The transmission mechanism is connected to the movable enclosure and drives it to move along the follow-up bracket. The motor is the power source for the drive device. The axle height sensor is electrically connected to the host computer control system, which is also electrically connected to the motor. The host computer control system converts the distance difference detected by the axle height sensor between the lower edge of the landing gear axle and the large flywheel into a voltage value for the drive motor. The motor controller then drives the motor to operate and drive the transmission mechanism, ensuring that the relative position of the excitation device and the landing gear axle remains unchanged.

[0012] In one embodiment, the transmission mechanism is a lead screw, and the motor drives the lead screw to rotate, causing the movable sealing box to move up and down along the follower bracket.

[0013] Based on the same inventive concept, the present invention also provides a method for testing aircraft landing gear shimmy, the method comprising the following steps: Step 1: Install the landing gear on the vibration test bench, start the follow-up displacement measurement system, adjust the excitation device to keep it at the same horizontal height as the landing gear wheel axle, and connect the excitation device to the landing gear wheel axle; Step 2: Calculate the excitation force arm generated by the excitation device on the landing gear wheel axle; Step 3: Press the aircraft landing gear against the large flywheel below and apply pressure, then start the large flywheel to reach the required test speed; Step 4: Set the excitation displacement, excitation time, and excitation count in the test bench control system. Apply instantaneous excitation to the excitation device. The test bench control system automatically detects the landing gear sway angle. After the landing gear swaying stops and stabilizes, the test bench control system automatically performs subsequent excitations until the set number of excitations is reached. Collect and record relevant data during the excitation process. Step 5: After the test, lift the landing gear to disengage it from the large flywheel. The excitation device will move along the center of the wheel axle. After the large flywheel comes to a complete stop, disconnect the excitation device from the landing gear wheel axle. In one embodiment, during step four, if an emergency occurs during continuous excitation, the axle is immediately lifted, and the follow-up system is activated to avoid damaging the test product.

[0014] In one embodiment, during step four, if an emergency occurs during continuous excitation, the axle is immediately lifted, and the follow-up system is activated to follow the axle, thus avoiding damage to the test product.

[0015] This invention can simulate the control effect of the anti-shield system on the stability of landing gear under disturbance excitation forces or disturbance torques during takeoff, taxiing, and landing of aircraft with different design configurations. This invention features a short excitation time to simulate real-world operating conditions, accurately detects the shield stability performance of the landing gear, and allows for continuous excitation even with continuous changes in test conditions—that is, continuous excitation can be applied to the wheel axle without stopping the machine—significantly improving work efficiency.

[0016] The servo displacement measurement system designed in this invention can keep the excitation force and the wheel axle center on the same horizontal plane. It can apply both torque control and torque excitation control, and is suitable for landing gear shimmy tests with different wheel axle heights, different tire diameters and different excitation methods, and has a certain degree of versatility. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall structure of Embodiment 1 of the present invention; Figure 2 This is a schematic diagram showing the positions of the various structures and sensors in Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the sensor setup at each measurement point in Embodiment 1 of the present invention; Figure 4 for Figure 3 Schematic diagram of the structure at point A in the middle; Figure 5 This is a schematic diagram of the follower displacement measurement system and excitation device according to Embodiment 1 of the present invention; Figure 6 This is a schematic diagram of the excitation angle calculation in Embodiment 1 of the present invention; Figure 7 This is a flowchart of the aircraft landing gear shimmy test method according to Embodiment 1 of the present invention; Figure 8 This is a flowchart of the aircraft landing gear oscillation stability test in Embodiment 1 of the present invention; Figure 9 This is a flowchart of the servo loading test of the nose landing gear angle in a reduced yaw state, according to Embodiment 2 of the present invention. Figure 10 This is a flowchart of the servo loading test of the nose landing gear angle of an aircraft in a controlled state, as described in Embodiment 3 of the present invention. Figure 11 This is a flowchart of the nose landing gear angle command loading test of an aircraft landing gear in a controlled state, as described in Embodiment 4 of the present invention. In the diagram, 1. Main frame; 2. Suspended platform system; 3. Large flywheel; 4. Flywheel drive system; 5. Excitation device; 6. Follow-up displacement measurement system; 7. Landing gear; 8. Landing gear axle; 201. First crossbeam; 202. Second crossbeam; 203. Servo hydraulic loading cylinder; 204. Wire displacement sensor; 205. Guide rail; 401. Drive motor; 402. Coupling; 403. Reducer; 501. Hydrostatic support cylinder; 502. Steel wire rope; 503. 601 Fixed pulley, 602 Wheel axle height sensor, 603 Follower bracket, 604 Moving sealing box, 605 Motor, 606 Drive screw, 607 Moving slider, 608 Motor bracket, 609 Fixed platform, 6000 Commutator, 9. Triaxial force sensor, 10. Triaxial acceleration sensor, 11. Encoder, 12. Upper connecting rod, 13. Lower connecting rod, 14. Upper clamp, 15. Lower clamp, 16. Uniaxial acceleration sensor, 17. Pressure sensor. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "or / and" as used herein includes any and all combinations of one or more of the associated listed items.

[0020] Example 1 like Figure 1 As shown, the aircraft landing gear vibration test bench consists of a main frame 1, a basket system 2, a large flywheel 3, a flywheel drive system 4, an excitation device 5, a follow-up displacement measurement system 6, and landing gear 7.

[0021] In this embodiment, the main frame 1 is the foundation support and guide structure of the test bench. Its main function is to provide a stable mounting base and motion guidance for other devices. The main frame 1 is welded from high-strength steel plates and profiles. Its structural design adopts the principle of force self-balancing to avoid structural deformation or vibration interference caused by external forces, thereby ensuring the accuracy and reliability of test data.

[0022] like Figure 2As shown, in this embodiment, the suspended platform system 2 includes a first crossbeam 201, a second crossbeam 202, and a servo hydraulic loading cylinder 203. The first crossbeam 201 is fixed on the main frame 1, and the second crossbeam 202 is slidably mounted on the main frame 1. The first crossbeam 201 is located above the second crossbeam 202. The servo hydraulic loading cylinder 203 is installed between the first crossbeam 201 and the second crossbeam 202, and the landing gear 7 is installed on the lower surface of the second crossbeam 202. The servo hydraulic loading cylinder 203 is responsible for pressing down and lifting the landing gear 7. Adjusting the pressure of the servo hydraulic loading cylinder 203 controls the downward load, and adjusting the flow rate of the servo hydraulic loading cylinder 203 controls the downward speed.

[0023] Among them, the guide rail 205 is responsible for guiding the vertical movement of the suspended platform and bearing the yaw load applied by the suspended platform.

[0024] The basket system 2 is designed as a frame structure that can move vertically along the guide rails on the main frame 1. The basket system 2 is not only responsible for installing and fixing the landing gear 7 under test, but also directly bears the vertical test load and its reaction force generated by the servo hydraulic loading cylinder 203. By controlling the servo hydraulic loading cylinder 203, the vertical load on the landing gear 7 is precisely controlled, simulating the vertical load state of the landing gear 7 under different operating conditions.

[0025] In this embodiment, the excitation device 5 is positioned laterally on the landing gear axle 8 to simulate instantaneous external disturbance impacts during aircraft takeoff. The excitation device 5 includes a hydrostatic support cylinder 501, a hydraulic servo system, a steel wire rope 502, and a fixed pulley 503. The hydraulic servo system provides power to the hydrostatic support cylinder 501, allowing the axle end cap to be installed on the landing gear axle 8. One end of the steel wire rope 502 is connected to the axle end cap, while the other end passes around the fixed pulley 503 and connects to the piston rod of the hydrostatic support cylinder 501. At this time, the piston rod of the hydrostatic support cylinder 501 remains in a floating state, ensuring that the hydrostatic support cylinder 501 and the axle steel wire rope 502 can extend normally for easy connection. The excitation device 5, by connecting the steel wire rope 503 to the landing gear axle 8, provides an instantaneous lateral excitation force to the landing gear 7, thereby effectively exciting the shimmy mode of the landing gear 7.

[0026] The large flywheel 3 is the core component for simulating aircraft takeoff. The large flywheel 3 provides a continuous tangential speed to the landing gear 7 tires, driving the landing gear 7 wheels to rotate to a set speed. At the same time, it directly bears the vertical load applied by the servo hydraulic loading cylinder 203 in the basket, realistically simulating the load situation of the wheels during high-speed rolling when the landing gear is landing.

[0027] The flywheel drive system 4 is responsible for providing rotational power to the large flywheel 3, and typically includes components such as a drive motor 401, a coupling 402, and a reducer 403. The drive motor 401 can be a servo motor or a high-power AC motor, possessing a wide speed range adjustment capability; the reducer 403 is used to increase output torque and match the speed requirements of the large flywheel 3; the coupling 402 ensures the smoothness and alignment accuracy of power transmission. The entire drive system must possess high-precision speed control and torque stability to accurately simulate various taxiing conditions during aircraft takeoff and landing.

[0028] like Figure 3 As shown, during the excitation test, the landing gear vibration performance needs to be measured in real time, mainly including: Vibration overload measurement at hinge point: A triaxial acceleration sensor 10 and a triaxial force velocity sensor 9 are installed at the hinge point connecting the basket system and the landing gear for triaxial vibration overload measurement at the hinge point. like Figure 4 As shown, the landing gear wheel sway angle is measured: the encoder 11 is used to measure the sway angle of the landing gear 7 wheel. The four-bar linkage consisting of the upper link 12, the lower link 13, the upper clamp 14, and the lower clamp 15 is used to dynamically measure the sway angle of the landing gear 7 wheel. The linkage mechanism is assembled between the outer cylinder of the landing gear and the rotating sleeve when in use.

[0029] Lateral vibration overload measurement at the wheel axle: The vibration overload of the landing gear wheel axle 8 is measured using a unidirectional acceleration sensor 16, which is located on both sides of the landing gear wheel axle 8.

[0030] Lateral overload measurement at the connection of the upper and lower torque arms: The vibration overload at the connection of the upper and lower torque arms of the landing gear 7 is measured using lateral acceleration sensors, which are set on both sides of the torque arm connection.

[0031] Pressure measurement of the left and right chambers of the turning actuator: The pressure sensor 17 is used to measure the pressure of the left and right chambers of the turning actuator. The pressure sensor 17 is connected to the oil supply line of the turning actuator through a tee.

[0032] Excitation load and displacement measurement: The excitation load and displacement are measured using load sensors and displacement sensors. Both are integrated into the hydrostatic support cylinder design and are installed inside the hydrostatic support cylinder.

[0033] Large flywheel speed measurement: The speed of the large flywheel is measured using a speed sensor.

[0034] like Figure 5As shown, in this embodiment, the follow-up displacement measurement system 6 includes a wheel axle height sensor 601, a follow-up bracket 602, a movable sealing box 603, a motor 604, a transmission screw 605, and a host computer control system. The static pressure support cylinder 501 is installed on the movable sealing box 603. A screw nut is installed in the movable sealing box 603 for connecting the transmission screw 605. Four movable sliders 606 are installed on both sides of the movable sealing box 603. The follow-up bracket 602 is provided with a guide rail, and the movable sliders 606 can slide up and down on the guide rail.

[0035] Among them, the motor 604 is mounted on the motor bracket 607, and the motor bracket 607 is mounted on the fixed platform 608 on the top of the follower bracket 602.

[0036] The motor 604 is connected to the reducer via a coupling, and the reducer is connected to the commutator 609 via a coupling, transmitting power to the lead screw 605. Bearings are mounted on the lead screw 605, which are supported by bearing supports on the base plate. The motor 604 provides power to the lead screw 605, driving the commutator 609 to rotate the lead screw 605. The lead screw 605 is connected to the lead screw nut in the movable sealing box 603, thereby causing the movable sealing box 603 to move rapidly up and down. The motor controller drives the motor 604 to operate and rotate the lead screw 605, ensuring that the piston rod of the hydrostatic support cylinder 501 and the landing gear axle 8 are always on the same horizontal plane, so that transient lateral disturbance excitation can be applied to the landing gear axle after the vertical load is applied.

[0037] To make the movement of the movable sealing box 603 more stable, in this embodiment, two sets of lead screw, lead screw nut, commutator, bearing, bearing support, etc. are provided, located on both sides of the movable sealing box 603 respectively.

[0038] The wheel axle height sensor 601 is electrically connected to the host computer control system, which in turn is electrically connected to the motor 604. The wheel axle height sensor 601 is installed on the lower edge of the landing gear wheel axle 8 and measures the relative distance between the lower edge of the landing gear wheel axle 8 and the surface of the large flywheel 3 in real time. After obtaining the measured distance, the wheel axle height sensor 601 directly feeds this distance back to the host computer control system. The host computer calculates the wheel axle height and compares it with the height of the currently driven steel wire rope 502 shaft. If the distance difference exceeds the set disturbance threshold (the static pressure support cylinder does not move up and down within 3 mm of the landing gear wheel axle moving vertically), the computer converts the distance difference into the voltage value of the drive motor 604. The motor controller then drives the motor 604 to work, and the transmission screw 605 moves the static pressure support cylinder 501, causing the shaft of the steel wire rope 502 to move to the same height as the shaft of the landing gear wheel axle 8, thus achieving real-time following. If the distance difference is less than the set disturbance threshold, the computer will determine that the distance difference is caused by system vibration disturbance and will not control the drive motor to operate, thereby preventing the servo system from malfunctioning.

[0039] When the follow-up displacement measurement system 6 is working, the static pressure support cylinder 501 is always in a floating state, and its piston rod can move freely within a certain range. The steel wire rope connected to the piston rod has a certain extension and contraction margin, which can prevent the real-time follow-up reaction from being untimely during the follow-up process, and will not cause damage to the equipment and products.

[0040] The specific parameters and functions of the test bench are as follows: (1) Large flywheel dimensions: 5000(mm)×1600(mm) (diameter×width); (2) The maximum rotational speed of the large flywheel is 425 r / min (gliding speed: 400 km / h); and it can rotate at a constant speed at any speed from 10 to 400 km / h; (3) The acceleration / deceleration of the large flywheel is not greater than: 1.5 m / s² 2 ; (4) Vertical load applied by servo hydraulic loading cylinder: 800KN, 420KN in the heading direction (the landing gear structure and bearing bear the brake and braking loads). The vertical load has a two-way loading function of tension and compression. The landing gear can be lifted by the servo hydraulic loading cylinder for small load (its value is less than the mass force of the hoist and clamp) loading test.

[0041] (5) The function of the excitation device 5 is: lateral excitation force of 200KN. The excitation loading period is less than 0.1s, the swing angle is 4°±1°, and the excitation torque is not less than 2.5KN·m. The excitation loading angle can be adjusted to simulate the direction of lateral disturbance during actual taxiing; the excitation loading axis can be automatically adjusted with the wheel axle height to ensure that the direction of excitation loading is at the same horizontal level as the landing gear wheel axle axis under various test conditions; the excitation impact can be performed continuously multiple times without manual intervention, which can greatly improve the test efficiency and continuously change the test state according to a certain load spectrum.

[0042] like Figure 7 As shown, in this embodiment, the operation steps of the aircraft landing gear shimmy test method include: Step 1: Install the landing gear 7 on the vibration test bench, start the follow-up displacement measurement system 6, and adjust the wire rope 502 to keep it at the same horizontal height as the center of the landing gear wheel axle 8 according to the height of the landing gear 7.

[0043] Step Two: Calculate the excitation arm generated by the excitation device 5 on the landing gear axle 8: The magnitude of the excitation torque acting on the landing gear is a standard for measuring the performance of the excitation device and an important parameter for evaluating whether the oscillation test meets the relevant specifications. The magnitude of the excitation torque is directly related to the excitation angle, so the excitation angle must be measured first. The excitation angle is calculated using the known axle length and the distance from the axle to the fixed pulley, through a proportional relationship.

[0044] like Figure 6 As shown, based on their geometric relative relationship, the included angle between the wire rope and the landing gear axle can be directly calculated. For the axles of different models, see the diagram. B The position of the point only moves in the X direction, while remaining unchanged in the Y direction. That is, after the landing gear contacts the large flywheel vertically (Y direction), the applied lateral excitation will only cause the landing gear wheels to deflect horizontally (X direction). Once the excitation device is fixed in place... L 1 and L The length of 2 can be obtained directly. Before using the formula for calculation, it is also necessary to obtain the width of the test wheel and input this information directly into the control system. The control system will calculate the excitation angle based on the above known information.

[0045]

[0046]

[0047]

[0048]

[0049]

[0050] in, L 1: The horizontal distance from the landing gear buffer strut to the wheel axle center; L 2: Horizontal displacement of the landing gear buffer strut to the tangent point of the fixed pulley; O Point: The center of rotation of the fixed pulley; B Point: Location of the wheel axle; A point: O The intersection of point B and the extension line of point B; C Point: The location of the point of tangency between the wire rope and the fixed pulley; r : Wire rope radius; R : Inner radius of the fixed pulley; The angle between wire rope 502 and the landing gear wheel axle 8 can be calculated using the above formula. α By combining the geometric dimensions of the landing gear, the corresponding excitation arm can be obtained directly, and the excitation torque can be calculated based on the excitation arm.

[0051] Alternatively, after the excitation device is fixed, the position of the landing gear wheel axle 8, the length and relative position of the wire rope 502 after pretensioning will not change. Calculate the distance from point B to the Y-direction wire rope. This distance is the excitation lever arm. The excitation torque can be calculated based on the excitation lever arm.

[0052] The excitation torque is the force applied to the wire rope in the Y direction multiplied by the distance between point B and the wire rope in the Y direction.

[0053] Step 3: Test Preparation: Press the landing gear 7 against the large flywheel 3 below and apply pressure to simulate the compression of the landing gear by the aircraft's own weight. Start the flywheel to rotate to the required test speed, and start the hydrostatic support cylinder 501 to apply preload to the wire rope 502.

[0054] Step Four: Continuous Excitation: Set the excitation displacement, excitation time, and number of excitations on the test bench control system interface. The test bench control system controls the servo valve to perform instantaneous excitation of the hydraulic cylinder. The control system automatically detects the landing gear sway angle. Once the landing gear swaying stops and stabilizes, the system automatically performs subsequent excitations until the set number of excitations is reached. The data acquisition system automatically records relevant data during the excitation process. During continuous excitation, in case of an emergency, the wheel axle immediately lifts, and the servo system activates to follow the wheel axle, preventing damage to the test product.

[0055] Step 5: End of Test: Raise the landing gear 7 to disengage the tires from the large flywheel 3. The excitation device moves along the center of the axle, and the large flywheel 3 stops rotating. After it comes to a complete stop, disconnect the steel cable 502 from the axle and shut down the entire system.

[0056] like Figure 8As shown, this embodiment discloses a shimmy test of an aircraft landing gear under reduced shimmy conditions: The landing gear control system is in a reduced-sway state. The landing gear landing vertical load is simulated using the servo hydraulic loading cylinder 203 and the basket system (i.e., the vertical load is constant under different tire inflation states and the set filling state of the landing gear buffer). The vertical load of the landing gear 7 is controlled by the downward pressing of the servo hydraulic loading cylinder 203. The compression amount corresponding to the vertical load is used as the set value for applying the control vertical load. The landing gear 7 wheels are rotated by rotating the large flywheel 3 to simulate the landing gear takeoff / landing speed. When the friction of the large flywheel 3 drives the landing gear 7 wheels to rotate to the set rotation speed, the lateral transient disturbance excitation force is applied to the center of the landing gear wheel axle 8 through the lateral disturbance excitation system to simulate the transient ground disturbance during the landing gear taxiing process. During this process, the triaxial load at the landing gear hinge point, the displacement of the basket center, the displacement of the landing gear buffer strut, and the acceleration at the wheel axle and anti-torsion arm are measured.

[0057] This embodiment discloses a shimmy stability test of an aircraft landing gear under reduced shimmy conditions: The landing gear steering control system is in a reduced yaw state. A lateral disturbance excitation system applies transient disturbances to the landing gear at the wheels during the taxiing process. The specific excitation method is as follows: the servo hydraulic loading cylinder 203 is controlled to press the landing gear 7 onto the rotating flywheel 3 at a speed of 30 mm / s to the set load value (compression amount) and set speed. After waiting for 3 seconds, the lateral disturbance excitation system applies a transient disturbance angle of 4°±1° to the center of the front landing gear wheel axle for excitation. After the transient excitation is released, the taxiing continues for 3 seconds, and the landing gear 7 is raised to the initial suspended state, thus completing one test state.

[0058] This embodiment discloses a sway stability test of aircraft landing gear under control conditions, including: Shaking stability test under operating state 1: The landing gear turning control system is in the operating state, and the servo hydraulic loading cylinder 203 is controlled to press the landing gear 7 onto the rotating flywheel 3 at a speed of 30 mm / s to the set load value (compression amount) and set speed. After waiting for 3 seconds, the lateral disturbance excitation system applies a disturbance excitation of the same magnitude as the excitation load in the sway reduction state to the center of the front landing gear wheel axle. After the transient excitation is released, the taxiing continues for 3 seconds, and the landing gear 7 is raised to the initial suspended state to complete one test state.

[0059] Shaking test under operating state 2: The landing gear turning control system is in the operating state. The servo hydraulic loading cylinder 203 is controlled to press the landing gear 7 onto the rotating flywheel 3 at a speed of 30 mm / s to the set load value (compression amount) and set speed. After waiting for 3 seconds, the front wheel turning control command causes the front wheel to suddenly deflect 4°±1°, and then immediately return to 0°. Continue taxiing for 3 seconds, and lift the landing gear to the initial suspended state to complete one test state.

[0060] Example 2 like Figure 9 As shown, this embodiment discloses a servo-load test of the nose landing gear angle under reduced yaw conditions: Step 1: Preparation phase. Operate the on-site equipment and adjust the loading load so that the vertical load applied by the servo hydraulic loading cylinder 203 is in any one of the five states of 20KN, 60KN, 100KN, 150KN, and 200KN. Then apply a speed to the landing gear 7 wheels so that the rotation speed of the landing gear 7 wheels reaches any one of the preset speeds within 30km / h, 50 km / h, 70 km / h, 90 km / h, 110 km / h, 130 km / h, 150 km / h, 170 km / h, 190 km / h, 210 km / h, 230 km / h, 250 km / h, 270 km / h, 290 km / h, 310 km / h, 330 km / h, 350 km / h, 370 km / h, 390 km / h, and 400 km / h. The loading load and loading speed reach the test state. Step 2: Inflate the left and right landing gear tires to the preset pressure; Step 3: Tighten the steel wire rope to apply an excitation; Step 4: Control the hydraulic actuator to apply a 0.1s instantaneous disturbance excitation, causing the landing gear wheel to deflect by 4°, and immediately release the wire rope. Allow the landing gear wheel to reduce sway under damped inertia. Collect and save the data from various sensors.

[0061] Step 5: After this condition test is completed, proceed to preparation, adjust the vertical load, landing gear wheel speed, or left and right chamber pressure, and continue to step 3 for testing until the test is completely completed.

[0062] Example 3 like Figure 10 As shown, this embodiment discloses a servo-load test of the nose landing gear angle under control conditions: Step 1: Preparation stage. Operate the on-site equipment and adjust the vertical load so that the vertical load is in any one of the five states: 20KN, 60KN, 100KN, 150KN, and 200KN. Step 2: Tighten the steel wire rope to apply an excitation; Step 3: Control the hydraulic actuator to apply a 0.1s instantaneous disturbance excitation, causing the landing gear wheel to polarize by 4°, and immediately release the wire rope. Allow the landing gear wheel to reduce sway under damped inertia. Collect and save the data from various sensors.

[0063] Step 4: After this condition test is completed, proceed to preparation, adjust the vertical load, and continue with subsequent tests until the test is completely completed.

[0064] Example 4 like Figure 11 As shown, this embodiment discloses a nose landing gear angle command loading test under control conditions: Step 1: Preparation stage. Operate the on-site equipment and adjust the vertical load so that the vertical load is in any one of the five states of 20KN, 60KN, 100KN, 150KN, and 200KN. Step 2: Tighten the steel wire rope to apply an excitation; Step 3: Send angle signals to the landing gear wheels via the command system. Collect and save data from various sensors.

[0065] Step 4: After this condition test is completed, proceed to preparation, adjust the vertical load, and continue with subsequent tests until the test is completely finished.

[0066] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An aircraft landing gear shimmy test bench, characterized in that, include: The main frame serves as the support and guide structure for the test bench; A suspended platform system for mounting and applying loads to the landing gear, the suspended platform system being able to move up and down along the main frame; The large flywheel provides a continuous tangential velocity to the landing gear and bears the vertical loads applied by the basket system; A flywheel drive system that provides power to the large flywheel; An excitation device is provided on one side of the landing gear wheel axle and connected to the landing gear wheel axle. The excitation device applies an instantaneous lateral excitation force to the landing gear wheel axle for a duration not exceeding 0.2s and a swing angle not exceeding 5°. A follow-up displacement measurement system measures the distance between the landing gear wheel axle and the large flywheel in real time, and controls the ground clearance of the excitation device in real time based on this distance, so that the relative position of the excitation device and the landing gear wheel axle remains unchanged. The excitation device includes a hydrostatic support cylinder, a hydraulic servo system, a wire rope, and a fixed pulley. The hydraulic servo system provides power to the hydrostatic support cylinder. One end of the wire rope is connected to the landing gear wheel axle, and the other end of the wire rope passes around the fixed pulley and is connected to the hydrostatic support cylinder. The servo displacement measurement system includes an axle height sensor, a servo support, a movable enclosure, a motor, a transmission mechanism, and a host computer control system. The axle height sensor is located on the lower edge of the landing gear axle. The excitation device is mounted on the movable enclosure, which is slidably mounted on the servo support. The transmission mechanism is connected to the movable enclosure and drives it to move along the servo support. The motor provides power to the transmission system. The axle height sensor is electrically connected to the host computer control system, which is also electrically connected to the motor. The host computer control system converts the distance difference detected by the axle height sensor between the lower edge of the landing gear axle and the large flywheel into a voltage value for the drive motor. The motor controller then drives the motor and the transmission mechanism, ensuring that the relative position of the excitation device and the landing gear axle remains unchanged.

2. The aircraft landing gear shimmy test bench according to claim 1, characterized in that: The suspended platform system includes a first crossbeam, a second crossbeam, and a servo hydraulic loading cylinder. The first crossbeam is fixed on the main frame, and the second crossbeam is slidably mounted on the main frame. The first crossbeam is located above the second crossbeam. The servo hydraulic loading cylinder is installed between the first crossbeam and the second crossbeam, and the landing gear is installed on the lower surface of the second crossbeam.

3. The aircraft landing gear shimmy test bench according to claim 2, characterized in that: A wire displacement sensor is provided between the first crossbeam and the second crossbeam.

4. The aircraft landing gear shimmy test bench according to claim 1, characterized in that: The flywheel drive system includes at least a drive motor, a coupling, and a reducer. The drive motor and the reducer are connected through the coupling. The drive motor provides power to the flywheel, and the reducer is used to increase the output torque and match the flywheel speed requirements.

5. The aircraft landing gear shimmy test bench according to claim 1, characterized in that: The transmission mechanism is a lead screw, and the motor drives the lead screw to rotate, causing the movable sealing box to move up and down along the follower bracket.

6. A method for conducting a shimmy test on an aircraft landing gear using the aircraft landing gear shimmy test bench according to any one of claims 1-5, characterized in that, Includes the following steps: Step 1: Install the landing gear on the vibration test bench, start the follow-up displacement measurement system, adjust the excitation device to keep it at the same horizontal height as the landing gear wheel axle, and connect the excitation device to the landing gear wheel axle; Step 2: Calculate the excitation force arm generated by the excitation device on the landing gear wheel axle; Step 3: Press the aircraft landing gear against the large flywheel below and apply pressure, then start the large flywheel to reach the required test speed; Step 4: Set the excitation displacement, excitation time, and excitation count in the test bench control system. Apply instantaneous excitation to the excitation device. The test bench control system automatically detects the landing gear sway angle. After the landing gear swaying stops and stabilizes, the test bench control system automatically performs subsequent excitations until the set number of excitations is reached. Collect and record relevant data during the excitation process. Step 5: After the test is completed, lift the landing gear to disengage it from the large flywheel. The excitation device will move along the center of the wheel axle. After the large flywheel comes to a complete stop, disconnect the excitation device from the landing gear wheel axle.

7. The aircraft landing gear shimmy test method according to claim 6, characterized in that: In step four, during continuous excitation, if an emergency occurs, the axle will immediately lift, and the servo system will start simultaneously to avoid damaging the test product.

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