Aircraft nose landing gear taxiing and shimmy simulation test bed

Abstract

The invention relates to an aircraft nose landing gear taxiing and shimmy simulation test bed. The test bed comprises a test device main body structure, a power execution control mechanism, a vibration excitation mechanism and a vibration detection system. The method solves the problems of determination, contrast evaluation and detection analysis of the shimmy influence factors of the nose landing gear of the aircraft. The torsion steering engine is added, so that the turning condition of a ground plane can be simulated. The height-adjustable supporting cross beam can adapt to undercarriages of different sizes only by replacing the undercarriage clamp instead of replacing the whole frame, so that the use cost is greatly reduced. And more accurate data are provided for the design of the nose landing gear of the aircraft.

Description

Technical Field

[0001] The invention relates to the technical field of aircraft front landing gear design, in particular to an aircraft front landing gear simulated taxiing and shimmying test bench. Background Art

[0002] The front landing gear of an aircraft is the only key load-bearing and control component on the aircraft body that is responsible for bearing the weight of the entire aircraft. Its main functions are reflected in three aspects: first, it supports the weight of the aircraft when it is taxiing and parked on the ground; second, it provides control and braking force for the aircraft during the taxiing process; finally, it ensures that the aircraft can complete a safe and smooth landing and effectively absorbs the energy impact caused by external vibrations.

[0003] During the takeoff or landing process of the aircraft, the wheels may deflect due to external stimuli such as uneven runway and gravel. Even if the excitation disappears, the wheels may still experience periodic or divergent vibrations, which is called nose gear shimmy. With continuous energy input, the shimmy amplitude may gradually increase. In severe cases, it will not only shorten the service life of the nose gear and the aircraft, but also threaten flight safety. Shimmy will also reduce the stability and controllability of the aircraft, while affecting the safety and comfort of passengers, cargo or weapons. Therefore, studying the causes of shimmy is of great significance for discovering potential problems, optimizing nose gear design, improving flight safety, and improving maintenance methods.

[0004] The factors that induce the shimmy phenomenon are complex and varied. For example, when the structure of a new aircraft model does not match the tire parameters, shimmy may be caused. Studies have shown that the important factors affecting shimmy include: tire wear (for example, a runway surface that is too rough will cause the tread to wear too quickly at the moment of landing, while a runway surface that is too smooth may cause skidding), wheel mass imbalance (such as uneven tread wear, tire roundness or static imbalance of the wheel hub), excessive torsional clearance (caused by component wear, looseness or jamming), insufficient strut torsional stiffness, improper stability distance design, and excessive gas content in the shimmy damper oil. In addition, with the development of composite materials and active control technology, the influence of the elastic characteristics of the airframe structure on shimmy has gradually become a research focus. When landing encounters crosswind yaw or ground rolling is subject to lateral excitation, the nonlinear characteristics of the tire will cause the energy to be transferred to the front landing gear through deformation and interact with the fuselage. At this time, if there are design defects or component loss problems, it may cause self-excited vibration of the front landing gear.

[0005] Traditional vibration test methods usually cannot cover these complex causes, or require high costs for real-machine testing. Since safety in the early stages of the test is difficult to guarantee, it is not feasible to conduct tests directly using a physical aircraft. According to relevant literature, there are very few cases of front landing gear shimmy test flights abroad. Therefore, it is particularly necessary to develop a front landing gear vibration test platform for use in the laboratory. The platform simulates the effects of external excitation, external environment, and the front landing gear design itself on shimmy under high-speed taxiing conditions. Through precise control and comparative testing of these factors, the platform can provide scientific test data support for the optimal design of the front landing gear, thereby facilitating the formulation of safer and more efficient front landing gear design and maintenance plans. Summary of the invention

[0006] In view of the deficiencies in the prior art, the present invention aims to develop an aircraft front landing gear shimmy test device, aiming to more accurately determine and evaluate the factors affecting shimmy, provide a more comprehensive detection and analysis method, and provide reliable data support for the optimal design of the front landing gear.

[0007] The shimmy test is a key step in the design of the nose landing gear of an aircraft. Its main goal is to verify the shimmy reduction performance of the nose landing gear under different excitation conditions to ensure the stability of the aircraft during takeoff and landing. The commonly used initial deflection excitation method releases the wheels by setting an initial deflection angle to evaluate the anti-skid performance of the nose landing gear. However, the limitation of this method is that it does not take into account the effect of fuselage vibration, and it is impossible to apply (lateral, heading or lateral) vibration frequencies alone or in combination, so it is impossible to fully study the interference of these vibrations on the shimmy performance.

[0008] In order to solve this problem, the front landing gear shimmy test device and its supporting method and analysis system designed by the present invention can effectively simulate the aircraft vibration effects in various real environments. Specifically, the device can simulate various factors that may affect the shimmy performance, including: 1. Wheel imbalance; 2. Runway surface roughness; 3. Taxiing and vertical load; 4. Turning taxiing conditions; 5. Lateral impact load; 6. Tire slip, etc.

[0009] The device is designed to realistically simulate the impact of fuselage vibration on the front landing gear swing performance during aircraft take-off and landing. By applying interference with different vibration frequencies, the specific impact on the swing characteristics is studied, providing a scientific basis for the design and optimization of the front landing gear.

[0010] The present invention is achieved through the following technical solutions.

[0011] An aircraft nose landing gear simulated taxiing vibration test bench comprises a test device main structure, a power execution control mechanism, a vibration excitation mechanism, and a vibration detection system;

[0012] The main structure of the test device includes a power system base, a main frame, a support beam, a slide rail, a hydraulic device, a front landing gear fixture, and a front landing gear to be tested. The main frame is in an "n" shape. The lower end of the main frame is fixed on the power system base. The slide rail is symmetrically arranged on the upper end of the inner side of the main frame. The upper end of the hydraulic device is connected to the upper end of the main frame. The lower end of the hydraulic device is connected to the support beam. The support beam is slidably connected to the slide rail. The front landing gear fixture is arranged at the lower end of the support beam. The front landing gear fixture is used to install the front landing gear. The hydraulic device applies pressure to the support beam to simulate the vertical load of the front landing gear.

[0013] The power execution control mechanism includes a steering servo, a simulated runway, a transmission mechanism, and a drive motor. The simulated runway, the transmission mechanism, and the drive motor are installed on a power system base. The simulated runway is located below the front landing gear. When the hydraulic device applies pressure to the supporting crossbeam, the front landing gear contacts the simulated runway, and the drive motor drives the simulated runway to move through the transmission mechanism to simulate the taxiing state of the front landing gear when it lands. The steering servo is installed at the lower end of the supporting crossbeam. The steering servo controls the steering of the front landing gear through a connecting rod, and the drive motor drives the simulated runway to move through the transmission mechanism to simulate the state of the front landing gear when it is taxiing and turning.

[0014] The vibration excitation mechanism includes a lateral excitation hammer and a steering servo heading exciter. The lateral excitation hammer is installed on the main frame and corresponds to the side position of the front landing gear. The lateral excitation hammer strikes the front landing gear to provide lateral excitation. The heading excitation hammer is installed on the main frame and corresponds to the force point of the front landing gear. The heading exciter provides heading excitation for the front landing gear, and the steering servo provides torsional excitation. The lateral excitation hammer, the steering servo and the heading exciter are controlled by a control system to generate vibrations with different vibration frequencies and amplitudes, so as to simulate the vibration impact of complex roads on the front landing gear of the aircraft during taxiing.

[0015] The vibration detection system detects the vibration signal of the front landing gear, and generates time domain and frequency domain information through further data processing, providing a data basis for subsequent data analysis.

[0016] Furthermore, the power system base and the main frame are an integrated frame structure.

[0017] Furthermore, the vibration detection system includes a force sensor, a displacement sensor, an acceleration sensor, a laser vibrometer (which can measure displacement and acceleration), a non-contact angular displacement sensor, a non-contact angular acceleration sensor and a speed sensor. In addition, the speed of the motor can be displayed on the console, and the difference between the tire speed and the runway speed can also be calculated to study the tire slip phenomenon; the force sensor is installed on the surface where the hydraulic device contacts the crossbeam, and a displacement sensor and an acceleration sensor are installed on the lateral and heading sides of the lower part of the front landing gear pillar to measure the lateral and longitudinal vibrations of the front landing gear pillar respectively; the lower side surface of the tire of the front landing gear is scanned by a laser vibrometer to measure the lateral displacement and compression of the tire; a non-contact angular displacement sensor and a non-contact angular acceleration sensor are installed near the position where the torsion of the front landing gear pillar occurs to measure the torsion of the pillar; the speed sensor is installed on the wheel hub, and the tire speed can be measured by the speed sensor to calculate the taxiing speed.

[0018] Furthermore, the simulated runway is a flywheel.

[0019] Furthermore, the support crossbeam is height-adjustable via a slide rail to accommodate front landing gears of different sizes.

[0020] Compared with the prior art, the advantages of the present invention are: the present invention solves the determination, comparative evaluation, detection and analysis of the factors affecting the shimmy of the front landing gear of the aircraft. The torsion servo is added to simulate the turning situation of the ground aircraft. The height-adjustable support beam only needs to replace the landing gear clamp instead of the entire frame, which can adapt to landing gears of different sizes and greatly reduce the use cost. It provides more accurate data for the design of the front landing gear of the aircraft. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 : Schematic diagram of the main frame structure;

[0022] Figure 2 : Schematic diagram of the support beam structure of hydraulic lifting;

[0023] Figure 3 : Schematic diagram of the front landing gear fixture;

[0024] Figure 4 : Schematic diagram of the exciting hammer;

[0025] Figure 5 : Schematic diagram of steering servo;

[0026] Figure 6 : Schematic diagram of contact vibrator;

[0027] Figure 7 : Schematic diagram of the front landing gear torsional excitation installation;

[0028] Figure 8 : Schematic diagram of the front landing gear heading excitation installation;

[0029] Fig. 9 : Schematic diagram of the front landing gear lateral excitation installation;

[0030] Fig.10 : Schematic diagram of the connection of the detection and analysis system;

[0031] In the figure: 1. power system base, 2. main frame, 3. supporting beam, 4. slide rail, 5. hydraulic device, 6. lateral vibration hammer, 7. steering servo, 8. simulated runway, 9. transmission mechanism, 10. drive motor, 11. front landing gear clamp, 12. front landing gear, 13. heading vibration exciter. DETAILED DESCRIPTION

[0032] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0033] like Figures 1 to 10 As shown, a simulated taxiing and shimmying test bench for the front landing gear of an aircraft comprises a main structure of the test device, a power execution control mechanism, a vibration excitation mechanism, and a vibration detection system;

[0034] The main structure of the test device includes a power system base 1, a main frame 2, a support beam 3, a slide rail 4, a hydraulic device 5, a front landing gear fixture 11, and a front landing gear 12 to be tested. The main frame 2 is in an "n" shape. The lower end of the main frame 2 is fixed on the power system base 1. The slide rail 4 is symmetrically arranged on the upper end of the inner side of the main frame 2. The upper end of the hydraulic device 5 is connected to the upper end of the main frame 2. The lower end of the hydraulic device 5 is connected to the support beam 3. The support beam 3 is slidably connected to the slide rail 4. The front landing gear fixture 11 is arranged at the lower end of the support beam 3. The front landing gear fixture 11 is used to install the front landing gear 12. The hydraulic device 5 applies pressure to the support beam 3 to simulate the vertical load of the front landing gear 12.

[0035] The power execution control mechanism includes a steering servo 7, a simulated runway 8, a transmission mechanism 9, and a drive motor 10. The simulated runway 8, the transmission mechanism 9, and the drive motor 10 are installed on the power system base 1. The simulated runway 8 is located below the front landing gear 12. When the hydraulic device 5 applies pressure to the supporting crossbeam 3, the front landing gear 12 contacts the simulated runway 8, and the drive motor 10 drives the simulated runway 8 to move through the transmission mechanism 9 to simulate the taxiing state of the front landing gear 12 when it lands; the steering servo 7 is installed at the lower end of the supporting crossbeam 3, and the steering servo 7 controls the steering of the front landing gear through a connecting rod, and at the same time, the drive motor 10 drives the simulated runway 8 to move through the transmission mechanism to simulate the state of the front landing gear 12 when it taxis and turns;

[0036] The vibration excitation mechanism includes a lateral excitation hammer 6, a steering servo 7 and a heading exciter 13. The lateral excitation hammer 6 is installed on the main frame 2 and corresponds to the side position of the front landing gear 12. The lateral excitation hammer 6 strikes the front landing gear 12 to provide lateral excitation. The heading excitation hammer 13 is installed on the main frame 2 and corresponds to the force point of the front landing gear 12. The heading exciter 13 provides heading excitation for the front landing gear 12, and the steering servo 7 provides torsional excitation. The lateral excitation hammer 6, the steering servo 7 and the heading exciter 13 are controlled by a control system to generate vibrations with different vibration frequencies and amplitudes, so as to simulate the vibration impact of complex roads on the front landing gear 12 of the aircraft during the taxiing process of the aircraft, so as to detect the vibration reduction performance of the front landing gear.

[0037] The vibration detection system detects the vibration signal of the front landing gear 12, and generates time domain diagram and frequency domain diagram information through further data processing, thereby providing a data basis for subsequent data analysis.

[0038] The steering servo 7 can control the steering of the front landing gear 12 through a connecting rod, and can also provide torsional vibration.

[0039] The vibration excitation mechanism can apply lateral excitation, heading excitation, and torsional excitation to the front landing gear. The vibration of the aircraft fuselage causes the vibration of the front landing gear (lateral, heading, torsion), which is provided by the lateral excitation hammer, heading exciter and steering servo. The external excitation of the front landing gear during taxiing is added to the influence of the aircraft fuselage. For example, suddenly increasing the excitation in a certain direction and immediately restoring the excitation to the initial value can be regarded as an impact load.

[0040] The nose landing gear fixture can be customized according to different nose landing gear structure dimensions, and the height-adjustable support beam can adapt to nose landing gears of different lengths. Compared with replacing the entire frame, it can greatly save the cost of use.

[0041] Furthermore, the power system base 1 and the main frame 2 are an integrated frame structure.

[0042] Furthermore, the vibration detection system includes a force sensor, a displacement sensor, an acceleration sensor, a laser vibrometer, which can measure displacement, acceleration, a non-contact angular displacement sensor, a non-contact angular acceleration sensor and a speed sensor. In addition, the speed of the motor can be displayed on the console, and the difference between the tire speed and the runway speed can also be calculated to study the tire slip phenomenon; the force sensor is installed on the contact surface between the hydraulic device 2 and the crossbeam 3, and a displacement sensor and an acceleration sensor are installed on the lateral and heading sides of the lower part of the pillar of the front landing gear 12 to measure the lateral and longitudinal vibration conditions of the pillar of the front landing gear 12 respectively; the lower side surface of the tire of the front landing gear 12 is scanned by a laser vibrometer to measure the lateral displacement and compression of the tire; a non-contact angular displacement sensor and a non-contact angular acceleration sensor are installed near the position where the torsion of the pillar of the front landing gear 12 occurs to measure the torsion of the pillar; the speed sensor is installed on the wheel hub, and the tire speed can be measured by the speed sensor to calculate the taxiing speed.

[0043] Furthermore, the simulated runway 8 is a flywheel. The speed of the flywheel is controlled by a controller, so that the state of the front landing gear sliding when landing can be truly simulated. At the same time, the actual conditions of different runways (such as cement road surface, gravel road surface, asphalt road surface) can be simulated by changing the surface of the flywheel.

[0044] Furthermore, the support beam 3 can be adjusted in height through the slide rail 4 to adapt to front landing gears of different sizes.

[0045] 1. Wheel imbalance: By adding a mass block to the wheel hub (fixing the mass block on the wheel hub of the front landing gear), the wheel hub rotational inertia is changed to simulate the phenomenon of wheel rotation imbalance.

[0046] 2. Runway surface roughness: By changing the surface of the flywheel with different materials, the surface roughness of different runway surfaces (cement, asphalt, etc.) is simulated

[0047] 3. Taxiing and vertical load: The support beam 3 is pressed by the hydraulic mechanism at the top, and the vertical load is transferred to the front landing gear 12. This simulates the load on the front landing gear when the aircraft is taxiing.

[0048] 4. Turning and rolling conditions: The steering servo is used to simulate the effect of the aircraft turning at a low speed on the ground.

[0049] 5. Lateral impact load: When the vertical load is transferred to the front landing gear 12, the landing gear strut is struck by a lateral vibration hammer to simulate the lateral impact load.

[0050] 6. Tire slip, etc. The tire speed can be measured by the speed sensor installed on the wheel hub, and a difference can be obtained by comparing it with the speed of the motor. The effect of different runway roughness on tire slip can be studied.

[0051] The specific detection methods are as follows:

[0052] 1. By scanning the strut part of the front landing gear 12 with a laser vibrometer, the lateral displacement and acceleration of the strut surface of the front landing gear 12 can be obtained. Through further data processing, time domain and frequency domain information are generated to provide a data basis for subsequent data analysis.

[0053] 2. A displacement sensor and an acceleration sensor are installed on the lower side surface of the tire of the front landing gear 12 to measure the lateral displacement and compression of the tire. A non-contact angular displacement sensor and a non-contact angular acceleration sensor are installed near the point where the torsion of the strut of the front landing gear 12 occurs to measure the torsion of the strut. The tire rotation speed can be measured by the rotation speed sensor installed on the wheel hub, and then the accurate taxiing speed can be calculated.

[0054] The advantages of the present invention are as follows: the present invention solves the problem of determining, comparing, evaluating, detecting and analyzing the factors affecting the shimmy of the front landing gear of an aircraft. The torsion servo is added to simulate the turning situation of a ground aircraft. To adapt to landing gears of different sizes, only the landing gear fixture needs to be replaced, and the entire frame does not need to be replaced, which greatly reduces the use cost. More accurate data is provided for the design of the front landing gear of the aircraft.

[0055] The specific quantity of each sensor is shown in Table 1.

[0056] Table 1

[0057]

[0058]

[0059] The above description is only a preferred embodiment of the present invention, and does not limit the implementation mode and protection scope of the present invention. For those skilled in the art, it should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the description and illustrations of the present invention should be included in the protection scope of the present invention.

Claims

1. An aircraft front landing gear simulated taxiing shimmy test bench, characterized in that: It includes the main structure of the test device, the power execution control mechanism, the vibration excitation mechanism, and the vibration detection system; The main structure of the test device comprises a power system base (1), a main frame (2), a support beam (3), a slide rail (4), a hydraulic device (5), a front landing gear fixture (11), and a front landing gear (12) to be tested. The main frame (2) is in an "n" shape. The lower end of the main frame (2) is fixed on the power system base (1). The slide rail (4) is symmetrically arranged on the upper end of the inner side of the main frame (2). The upper end of the hydraulic device (5) is connected to the upper end of the main frame (2). The lower end of the hydraulic device (5) is connected to the support beam (3). The support beam (3) is slidably connected to the slide rail (4). The front landing gear fixture (11) is arranged at the lower end of the support beam (3). The front landing gear fixture (11) is used to install the front landing gear (12). The hydraulic device (5) applies pressure to the support beam (3) to simulate the vertical load of the front landing gear (12). The power execution control mechanism comprises a steering servo (7), a simulated runway (8), a transmission mechanism (9), and a drive motor (10). The simulated runway (8), the transmission mechanism (9), and the drive motor (10) are mounted on a power system base (1). The simulated runway (8) is located below a front landing gear (12). When a hydraulic device (5) applies pressure to a supporting crossbeam (3), the front landing gear (12) contacts the simulated runway (8). The drive motor (10) drives the simulated runway (8) to move through the transmission mechanism (9) to simulate the taxiing state of the front landing gear (12) when it lands. The steering servo (7) is mounted at the lower end of the supporting crossbeam (3). The steering servo (7) controls the steering of the front landing gear through a connecting rod. At the same time, the drive motor (10) drives the simulated runway (8) to move through the transmission mechanism to simulate the taxiing state of the front landing gear (12). The vibration excitation mechanism comprises a lateral vibration hammer (6), a steering servo (7) and a heading vibration exciter (13). The lateral vibration hammer (6) is mounted on the main frame (2) and corresponds to the side position of the front landing gear (12). The lateral vibration hammer (6) strikes the front landing gear (12) to provide lateral excitation. The heading vibration hammer (13) is mounted on the main frame (2) and corresponds to the force point of the front landing gear (12). The heading vibration exciter (13) provides heading excitation for the front landing gear (12). The steering servo (7) provides torsional excitation. The lateral vibration hammer (6), the steering servo (7) and the heading vibration exciter (13) are controlled by a control system to generate vibrations with different vibration frequencies and amplitudes, so as to simulate the vibration impact of a complex road on the front landing gear (12) of the aircraft during taxiing. The vibration detection system detects the vibration signal of the front landing gear (12), and generates time domain graph and frequency domain graph information through further data processing, thereby providing a data basis for subsequent data analysis.

2. The aircraft front landing gear simulated taxiing and shimmy test bench according to claim 1, characterized in that: The power system base (1) and the main frame (2) are an integrated frame structure.

3. The aircraft front landing gear simulated taxiing and shimmy test bench according to claim 1, characterized in that: The vibration detection system comprises a force sensor, a laser vibrometer, a non-contact angular displacement sensor, a non-contact angular acceleration sensor and a rotation speed sensor. The force sensor is installed on the contact surface between the hydraulic device (2) and the crossbeam (3). A displacement sensor and an acceleration sensor are installed on the lower side of the pillar of the front landing gear (12) in the lateral direction and the heading direction respectively to measure the lateral vibration and longitudinal vibration of the pillar of the front landing gear (12). The lower side surface of the tire of the front landing gear (12) is scanned by the laser vibrometer to measure the lateral displacement and compression of the tire. A non-contact angular displacement sensor and a non-contact angular acceleration sensor are installed near the position where the torsion of the pillar of the front landing gear (12) occurs to measure the torsion of the pillar. The rotation speed sensor is installed on the wheel hub. The tire rotation speed can be measured by the rotation speed sensor, and the taxiing speed is calculated.

4. The aircraft front landing gear simulated taxiing and shimmy test bench according to claim 1, characterized in that: The simulated runway (8) is a flywheel.

5. The aircraft front landing gear simulated taxiing and shimmy test bench according to claim 1, characterized in that: The support crossbeam (3) is height-adjustable via a slide rail (4).

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