A method for optimizing the vibration transmission of a manned aircraft

Abstract

The application provides a manned aircraft vibration transmission optimization design method, comprising the following steps: a dynamic characteristic analysis model of a new type of manned aircraft is established, dynamic characteristic parameters of the aircraft are solved, then according to a modal transfer function of the aircraft, in combination with information such as noise, vibration excitation source and transmission path, vibration transmission characteristic analysis of the aircraft structure is carried out, and the aircraft structure is optimized according to the analysis result; different vibration isolation measures are designed according to the structure optimization design scheme, so as to reduce the vibration response of the vibration excitation transmitted to important electrical equipment and the driving position of the personnel, the riding comfort of the pilot in the vibration and noise environment is comprehensively evaluated, and finally the effectiveness of the vibration reduction measure is verified. The application can greatly improve the environmental adaptability of the new type of manned aircraft structure and improve the use experience of the pilot.

Description

Technical Field

[0001] This invention relates to a vibration transmission optimization design method for manned aircraft, belonging to the field of mechanical environment design and optimization technology for novel micro manned aircraft. Background Technology

[0002] This patent addresses a novel manned aircraft. To ensure that the noise and vibration generated by the aircraft engine during operation do not damage the main structure of the aircraft, and to provide a more comfortable piloting environment, the development process requires suppressing the radiated noise of the engine and the vibration caused by the noise environment during flight. Simultaneously, ground tests are conducted during development to measure vibration and noise mechanical environmental parameters at key locations of the aircraft, and to evaluate pilot comfort. Since the load-bearing structural components of this aircraft are mainly composed of a composite material skeleton and thin-walled outer shell panels, the thin-walled outer shell is highly susceptible to vibration from external excitations. As the energy of the excitation source increases, the possibility of fatigue failure of the aircraft's structural components also increases, significantly impacting the aircraft's flight safety. This aircraft differs from all current manned aircraft in that the pilot's seating arrangement is unlike that of traditional aircraft. The engine is located in the center of the aircraft, and the pilot stands upright. This means the pilot's space is open, lacking the enclosed space of a cockpit. Analysis shows that the vibration transmission path of this new manned aircraft differs significantly from traditional aircraft. Vibrations experienced by the pilot are primarily transmitted to their body through their feet. Simultaneously, since the pilot is standing, noise originates from below and is transmitted to their body from the airspace. Without a sealed cabin, noise reduction for personnel relies mainly on external measures. Therefore, in the design and development of this new manned aircraft, research on vibration and noise environments, as well as minimizing harm to the pilot, became crucial technologies that needed to be addressed. Summary of the Invention

[0003] The technical problem solved by this invention is to overcome the shortcomings of the prior art, provide a vibration transmission optimization design method for manned aircraft based on the structural optimization design scheme of noise and vibration transmission path analysis, and evaluate the optimized structural form and final passenger comfort through relevant ground tests, thus verifying the feasibility of the scheme.

[0004] The technical solution of this invention is:

[0005] This invention discloses a vibration transmission optimization design method for manned aircraft, comprising:

[0006] Modal dynamics analysis of the manned spacecraft was performed to obtain a dynamics analysis model;

[0007] Ground modal tests were conducted on the manned aircraft under different operating conditions, and the modal test results were obtained.

[0008] The dynamic characteristic analysis model is revised based on the modal test results;

[0009] Based on the modal test results, vibration transmission path analysis is performed on the dynamic characteristic analysis model to obtain the modal vibration transfer function;

[0010] Conduct ignition tests of manned aircraft under different engine operating conditions and obtain ignition test results;

[0011] Based on the modal vibration transfer function and the ignition test results, the structural vibration transfer function of the manned aircraft in free flight state is obtained;

[0012] Based on the modal test results and the structural vibration transfer function, the manned spacecraft is structurally optimized to obtain an optimized structural design scheme.

[0013] In the above design method, the manned spacecraft is structurally optimized based on the obtained structural optimization design scheme, and ground ignition and flight tests are carried out to verify the structural optimization design scheme.

[0014] In the above design method, the dynamic characteristic analysis model specifically refers to the mass, center of mass, and structural connection stiffness of the aircraft under full-load and no-load conditions.

[0015] In the above design method, the modal test results specifically refer to the modal frequencies and mode shapes of the aircraft under conditions of full fuel tank load, no load, and manned operation.

[0016] In the above design method, the step of correcting the dynamic characteristic analysis model based on the modal test results is as follows: based on the frequencies and mode shapes obtained from the ground modal test, the structural mass distribution in the dynamic characteristic analysis model is adjusted to make the mass and center of mass consistent with the test product. At the same time, the connection stiffness of the aircraft is adjusted using a finite element simulation model based on the mode shape data so that the first two overall mode shapes and frequencies of the dynamic characteristic analysis model match the test results.

[0017] In the above design method, vibration transmission path analysis is performed on the dynamic characteristic analysis model to obtain the modal vibration transfer function. The specific method is as follows:

[0018] For the aircraft dynamics analysis model, a fast sinusoidal scanning excitation is applied at the engine mounting frame. The excitation signal frequency is F, the magnitude is G, and the scanning rate is S. The vibration frequency response at the pilot's standing position, the inertial navigation system mounting position, and the vibration excitation response at the engine mounting position are output.

[0019] Based on the vibration frequency response and vibration excitation response, the vibration transfer function is obtained, and the formula is:

[0020]

[0021] Among them, a i (ω) represents the vibration frequency response at the pilot's standing position and the inertial navigation system mounting position, and a0(ω) represents the vibration excitation response at the engine mounting position.

[0022] In the above design method, F = 20~2000Hz, G = 1~2g, S = 2~4oct / min, where F is the excitation signal frequency, G is the order of magnitude, and S is the scan rate.

[0023] In the above design method, the method of conducting ignition tests of manned aircraft under different engine operating conditions and obtaining ignition test results is as follows: vibration sensors are arranged at the pilot's standing position, the inertial navigation system installation position, and the main load-bearing structure of the aircraft; noise sensors are arranged in the space at radii of 1m, 3m, and 5m away from the center of the aircraft; vibration and noise data are monitored in real time during the ignition test to obtain the ignition test results.

[0024] In the above design method, the structural vibration transfer function of the manned spacecraft in free flight state is obtained based on the modal vibration transfer function and the ignition test results. The specific method is as follows:

[0025] H = (H1 + H2) / 2

[0026] Wherein, H1 is the vibration transfer function obtained from the modal test, H2 is the vibration transfer function obtained from the aircraft ignition test, and H is the structural vibration transfer function of the manned aircraft in free flight.

[0027] In the above design method, the structural optimization design scheme includes: increasing structural stiffness without increasing structural mass; adding vibration damping pads at the engine mounting frame; adjusting the vibration damping efficiency of the inertial navigation system and control computer vibration dampers to ensure that the electrical equipment can withstand the vibration environment. Based on the preliminary assessment of the electrical equipment's adaptability to the vibration environment, the vibration response at the equipment mounting location on the aircraft structure within the range of 20 to 2000 Hz is less than 3 Grms.

[0028] In the above design method, the different working conditions specifically refer to the working states of the manned aircraft under the conditions of full load, empty load, with load, and without load.

[0029] The advantages of this invention over the prior art are as follows:

[0030] (1) This invention combines a novel manned aircraft and designs a structural optimization design scheme based on noise and vibration transmission path analysis, which has the advantages of strong practicality and engineering.

[0031] (2) In combination with the usage requirements of a manned aircraft, this invention designed a ground test scheme for obtaining the vibration and noise mechanical environment parameters at key locations of the aircraft and successfully implemented it, obtaining the original vibration and noise data of the key locations where passengers sit under different flight conditions, which provides important data support for subsequent pilot comfort evaluation.

[0032] (3) This invention targets a novel micro manned aircraft. Based on its novel load-bearing structure, materials and engine installation form, it identifies and analyzes the transmission paths of structural vibration and noise, and identifies the main vibration transmission paths and key parameters affecting vibration transmission.

[0033] (4) This invention addresses the main transmission paths and key parameters, starting from the characteristics of vibration transmission and noise radiation. It adopts innovative structural design and optimization methods to suppress vibration and noise response. Without affecting the structural strength, it reduces the vibration response at key structural locations and improves the pilot's riding experience. Attached Figure Description

[0034] Figure 1 This is a flowchart of the optimized design method of the present invention. Detailed Implementation

[0035] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0036] This invention discloses a vibration transmission optimization design method for manned aircraft, comprising:

[0037] Step 1: Perform modal dynamics analysis on the manned aircraft to obtain a dynamics analysis model; For the three-dimensional structural model of the manned aircraft, use ABAQUS software to create a dynamics simulation model, and set the mass and center of mass of each component according to the actual state of the aircraft to make the final mass of the aircraft consistent with the three-dimensional structural model.

[0038] Step 2: Using the dynamic characteristic simulation model from Step 1, perform modal analysis on the new manned aircraft to obtain the overall mode shapes and frequencies under full and empty fuel tank conditions, and input the calculation results; conduct ground modal tests on the manned aircraft under different working conditions such as full load, empty load, loaded and unloaded conditions, and obtain the modal test results.

[0039] Step 3: Conduct ground modal tests on the prototype aircraft, so that the aircraft suspension is in a free state, and obtain the modal frequencies and mode shapes of the aircraft under the conditions of full fuel tank, empty load and crewed conditions.

[0040] Step 4: Correct the dynamic characteristic analysis model based on the modal test results. The specific method is as follows: Based on the dynamic characteristic model established in Step 1 and the calculation results in Step 2, combined with the frequencies and mode shapes obtained from the ground test in Step 3, adjust the structural mass distribution in the simulation model to make the mass and center of mass as consistent as possible with the test product. At the same time, adjust the connection stiffness of the aircraft using the finite element simulation model based on the mode shape data. Finally, make the first two overall mode shapes and frequencies of the simulation analysis model match the test results.

[0041] The dynamic characteristic analysis model specifically includes the mass, center of mass, and structural connection stiffness of the aircraft under fully loaded and unloaded conditions.

[0042] Step 5: Based on the modal test results, perform vibration transmission path analysis on the dynamic characteristic analysis model to obtain the modal vibration transfer function. The specific method is as follows:

[0043] For the aircraft dynamics analysis model, a fast sinusoidal scanning excitation is applied to the engine mounting frame. The excitation signal frequency is F, the magnitude is G, and the scan rate is S. The vibration frequency response at the pilot's standing position, the inertial navigation system (INS) mounting position, and the vibration excitation response at the engine mounting position are output. F = 20–2000 Hz, G = 1–2 g, S = 2–4 oct / min. Using ABAQUS for dynamic analysis, the vibration responses at the pilot's footrest position, the INS mounting position, and the control unit mounting position are output.

[0044] Based on the vibration frequency response and vibration excitation response, the vibration transfer function is obtained, and the formula is:

[0045]

[0046] Among them, a i (ω) represents the vibration frequency response at the pilot's standing position and the inertial navigation system mounting position, and a0(ω) represents the vibration excitation response at the engine mounting position.

[0047] The modal test results are specifically: the modal frequencies and mode shapes of the aircraft under the conditions of full fuel tank, empty load, and manned operation.

[0048] Step Six: Conduct ignition tests of the manned aircraft under different engine operating conditions to obtain ignition test results. The specific method is as follows: Vibration sensors are placed at the pilot's footrest, the inertial navigation system installation location, and the main load-bearing structure of the aircraft. Noise sensors are placed in the space at radii of 1m, 3m, and 5m from the center of the aircraft. Vibration and noise data are monitored in real time during the ignition test, and time-domain measurement data is recorded to obtain the ignition test results.

[0049] Step 7: Based on the modal vibration transfer function and ignition test results, analyze and obtain the structural vibration transfer function of the manned aircraft in free flight state. The specific method is as follows: During ground testing, the vibration response at the engine mounting frame was measured. This vibration response can be considered as the vibration generated by the engine during actual flight, i.e., vibration input. During the ignition test, the vibration responses at the pilot's footrest, inertial navigation system mounting location, control unit, and key structural connection points were measured. This vibration response can be considered as the vibration response of the aircraft after being subjected to vibration excitation. The input and output are processed according to Step 5 to obtain the vibration transfer function at different locations. The response patterns at different locations and frequencies can be observed. The transfer function formula is:

[0050] H = (H1 + H2) / 2

[0051] Wherein, H1 is the vibration transfer function obtained from the modal test, H2 is the vibration transfer function obtained from the aircraft ignition test, and H is the structural vibration transfer function of the manned aircraft in free flight.

[0052] Step 8: Based on the modal test results and the vibration transfer function of the structure, optimize the structure of the manned aircraft to obtain an optimized structural design scheme. Specifically, compare the transfer functions obtained in Steps 5 and 7 to see the difference in vibration response between the simulation analysis model and the actual product. Simultaneously, perform spectral analysis on the measured vibration response at different locations. For the human body, the vibration response should not be too large. For electrical equipment such as the inertial navigation system, the vibration response at the installation location should not exceed the tolerance limit of the electrical equipment and components. For the structure, the vibration response within the 20–500 Hz range should not be too large, and the vibration response should be less than 3 Grms. There should also be no significant abnormal amplification. Based on the above analysis, the following optimization schemes are proposed for the structure: 1. Increase the structural stiffness without increasing the structural mass; 2. Add vibration damping pads at the engine mounting frame; 3. Adjust the vibration damping efficiency of the inertial navigation system and control computer vibration dampers to ensure that the electrical equipment can withstand the vibration environment.

[0053] Step Nine: Based on the obtained structural optimization design scheme, optimize the structure of the manned aircraft and conduct ground ignition and flight tests to verify the optimized design scheme. Specifically, for the newly optimized manned aircraft, conduct ground ignition and flight tests. Test conditions include four scenarios: full fuel tank, empty fuel tank, and whether or not a crew is present. Engine speed ranges from idle to maximum speed. Vibration sensor locations include the engine mounting frame, pilot's standing area, inertial navigation system (INS) mounting location, control computer mounting location, and fuel tank mounting location. Noise sensor locations include above the pilot's footrest, at the pilot's head position, and at distances of 1m, 3m, 5m, 10m, 30m, and 50m around the aircraft. Measure vibration and noise environmental data during the flight tests. Perform spectral analysis on the measurement results to verify the feasibility of the design scheme.

[0054] Example:

[0055] like Figure 1 As shown, firstly, finite element simulation modeling of the aircraft is carried out in conjunction with the structural design, followed by modal dynamics simulation analysis of the manned aircraft. Based on the overall design scheme, a finite element simulation model of the new manned aircraft is established. The main frame of the aircraft is made of composite materials, and the structural stiffness is set according to the material layup direction. Regarding the aircraft mass, considering the specific operating conditions of the aircraft, two load conditions are set: full fuel tank load and empty load. Simultaneously, considering the need for the aircraft to carry passengers, a load model simulating the aircraft's load is established during modal simulation analysis to simulate its structural form on the aircraft. Dynamic characteristics analysis of the aircraft is conducted to obtain the modal shapes and frequencies of the aircraft under full load and empty load conditions. For the aircraft dynamics simulation model, a fast sinusoidal scanning excitation is applied at the engine mounting frame. Specific conditions include a frequency range of 20–2000 Hz, a magnitude of 1g, and a scan rate of 4 oct / min. The dynamic analysis is displayed using ABAQUS, outputting the vibration responses at the pilot's foot pedal position, the inertial navigation system mounting position, and the control unit mounting position. Here, the input acceleration at the engine mounting frame is a0, and the acceleration response at the foot position and the inertial navigation system mounting position is a. i The vibration transfer function is then... That is, the transfer function is defined as the ratio of the response to the input.

[0056] Secondly, ground tests were conducted on the aircraft to obtain its modal parameters and noise and vibration transfer functions. The noise and vibration excitation sources were analyzed, and simulation analysis was performed on the noise and vibration sources and their transmission paths. During the ground tests, the vibration response at the engine mounting frame was measured; this vibration response can be considered as the vibration generated by the engine during actual flight, i.e., the vibration input. In the ignition tests, the vibration responses at the pilot's standing position, the inertial navigation system (INS) mounting location, the integrated control unit, and key structural connection points were measured. These vibration responses can be considered as the vibration response of the aircraft after being subjected to vibration excitation. Processing the input and output yields the vibration transfer functions at different locations, revealing the response patterns at different locations and frequencies.

[0057] Combining simulation analysis and ground test results, vibration transmission path analysis and structural optimization design were conducted. For the human body, the primary sensitive vibration frequency should be 0–80 Hz. For electrical products such as inertial navigation systems (INS) and control computers, the primary sensitive vibration frequency is high-frequency, and should not be within the 70–90 Hz range, meaning there should be no structural response amplification within the sensitive frequency range of the INS vibration damper. Simultaneously, spectral analysis was performed on the measured vibration response at different locations. For the human body, the vibration response should not be excessive. For electrical equipment such as INS, the vibration response at the installation location should not exceed the tolerance limit of the equipment and components. For the structure, the vibration response within the 20–500 Hz range should not be excessive, and there should be no significant abnormal amplification. Regarding the transmission path and characteristics, the vibration level at the response point is controlled by reducing the structural load at the passive end of the excitation source or attenuating the transmission characteristics from the passive end to the response point. Specific structural optimization and improvement schemes include adding vibration isolation pads and energy-absorbing components to the engine mounting structure to first reduce the vibration level transmitted from the excitation source to the structure. Secondly, on the transmission path, without affecting the structural stiffness and strength, vibration reduction measures are added to the main transmission path to reduce the vibration level transmitted to important locations on the aircraft. Finally, vibration reduction devices are installed at the pilot's seating position to minimize the pilot's perception of vibration.

[0058] Finally, relevant ground tests were conducted to verify the vibration reduction and noise reduction performance of the optimized structure. For the structurally optimized manned aircraft, ground ignition and flight tests were carried out. For the newly optimized manned aircraft, ground ignition and flight tests were conducted. Test conditions included four scenarios: fully loaded fuel tank, empty fuel tank, and whether or not a crew was present. Engine speed ranged from idle to maximum speed. Vibration sensor locations included the engine mounting frame, pilot's standing position, inertial navigation system (INS) mounting location, control computer mounting location, and fuel tank mounting location. Noise sensor locations included above the pilot's footrest, at the pilot's head position, and at distances of 1m, 3m, 5m, 10m, 30m, and 50m around the aircraft. Vibration and noise mechanical environmental parameters were measured in real time during the tests, obtaining the vibration response of the aircraft structure and key locations under different flight conditions, and the noise level at the human ear in a standing position. Analysis of the test results shows that by optimizing the structure for vibration reduction, the vibration response at important load-bearing locations on the manned aircraft structure decreased by more than 10%, and the vibration response at the pilot's seating position decreased by more than 20%. In conjunction with the ISO 2631 standard, the comfort of personnel in the vibration environment was evaluated. Based on the evaluation results and the actual test flight experience of the pilots, the pilots did not experience any significant discomfort, thus verifying the feasibility of the current solution.

[0059] The above are merely the best specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

[0060] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A method of vibration transmission optimization design of a manned vehicle, characterized in that, The method comprises the following steps: modal dynamic characteristic analysis is performed on the manned aircraft to obtain a dynamic characteristic analysis model; ground modal tests are carried out on the manned aircraft under different working conditions to obtain modal test results; the dynamic characteristic analysis model is corrected according to the modal test results; vibration transmission path analysis is performed on the dynamic characteristic analysis model according to the modal test results to obtain a modal vibration transmission function; a firing test is performed on the manned aircraft under different engine working conditions to obtain firing test results; a structure vibration transmission function of the manned aircraft in a free flight state is obtained according to the modal vibration transmission function and the firing test results; structure optimization is performed on the manned aircraft according to the modal test results and the structure vibration transmission function to obtain a structure optimization design scheme; ground firing and flight tests are carried out on the manned aircraft after structure optimization to verify the structure optimization design scheme.

2. The method of claim 1, wherein: The dynamic characteristic analysis model is specifically the mass, center of mass and structure connection stiffness of the aircraft under the conditions of full load and empty load of the fuel tank.

3. The method of claim 1, wherein: The modal test results are specifically the modal frequency and mode shape of the aircraft under the conditions of full load, empty load of the fuel tank and manned flight.

4. The method of claim 1, wherein: The method for correcting the dynamic characteristic analysis model according to the modal test results is specifically adjusting the structure mass distribution in the dynamic characteristic analysis model according to the frequency and mode shape measured in the ground modal test, so that the mass and center of mass are consistent with the test product, and adjusting the connection stiffness of the aircraft by using a finite element simulation model according to the mode shape data, so that the first two order overall mode shapes and frequencies of the dynamic characteristic analysis model are consistent with the test results.

5. The method of claim 1, wherein: The method for obtaining the modal vibration transmission function by performing vibration transmission path analysis on the dynamic characteristic analysis model is specifically: a fast sine sweep excitation is applied to the engine mounting frame of the aircraft dynamic characteristic analysis model, the excitation signal frequency is F, the magnitude is G, the sweep rate is S, and the vibration frequency response of the pilot standing place and the inertial unit mounting place and the vibration excitation response of the engine mounting place are outputted; the vibration transmission function is obtained according to the vibration frequency response and the vibration excitation response, and the formula is: where a i (ω) is the frequency response of the vibration at the pilot's standing place, at the mounting place of the IMU, a0(ω) is the frequency response of the vibration excitation at the mounting place of the engine.

6. The method of claim 5, wherein: F=20-2000Hz, G=1-2g, S=2-4oct / min, wherein F is the excitation signal frequency, G is the magnitude, and S is the sweep rate.

7. The method of claim 1, wherein: The method for obtaining the firing test results by performing a firing test on the manned aircraft under different engine working conditions is specifically:

8. The method of claim 1, wherein: vibration sensors are arranged at the pilot standing place, the inertial unit mounting place and the main load-bearing structure of the aircraft, noise sensors are arranged at the space with a radius of 1m, 3m and 5m from the center of the aircraft, vibration and noise data are monitored in real time during the firing test, and the firing test results are obtained. The method for obtaining the structure vibration transmission function of the manned aircraft in a free flight state according to the modal vibration transmission function and the firing test results is specifically: H=(H1+H2) / 2 Wherein, H1 is the vibration transfer function obtained in modal test, H2 is the vibration transfer function obtained in aircraft ignition test, and H is the structural vibration transfer function of the manned aircraft in free flight state.

9. The method of claim 1, wherein: The structural optimization design scheme comprises: improving structural rigidity without increasing structural mass; adding a vibration damping pad at an engine mounting frame; adjusting the vibration damping efficiency of an inertial measurement unit, a control computer and a damper to ensure that the electrical equipment can tolerate the vibration environment; and according to adaptability of the electrical equipment to the vibration environment, the vibration response of the manned aircraft structure at the equipment installation position within 20-2000 Hz is less than 3Grms.

10. The method of claim 1, wherein: The different working conditions are specifically: working states of the manned aircraft under conditions of full load of the fuel tank, empty load of the fuel tank, carrying people and not carrying people.

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