Ground resonance calculation method considering influence of fuselage elasticity

Abstract

The invention belongs to the field of helicopter dynamics, and relates to a ground resonance calculation method considering fuselage elasticity influence. The method comprises the following steps: ground resonance calculation and analysis considering fuselage elasticity influence: on the basis of establishing a full-aircraft dynamics finite element model and performing simulation calculation to obtain vibration mode characteristic parameters of a fuselage on an undercarriage, performing calculation under the condition of considering a certain helicopter loading state and a certain rotor pulling force; and finally, giving a stability margin through stability analysis.

Description

Technical Field

[0001] The invention belongs to the field of helicopter dynamics and relates to a ground resonance calculation method taking into account the influence of fuselage elasticity. Background Art

[0002] The dynamic instability problem of the coupled vibration system of helicopter rotors and fuselage is a self-excited vibration problem often encountered in the development of helicopters. In the early stage of helicopter development, in the conventional ground resonance calculation and analysis, it is generally assumed that the stiffness, damping characteristics of the landing gear and the damping characteristics of the blade damper are linear, and the fuselage and blades are rigid bodies. Their elastic deformation is not considered. The perturbation motion equation is established using a spatial dynamic model, and the ground resonance calculation and analysis is performed by solving the matrix eigenvalue method. In fact, the elastic deformation of the fuselage will bring about changes in the vibration modal characteristics of the fuselage on the landing gear, thereby affecting the ground resonance stability characteristics of the rotor and fuselage coupling. Therefore, the influence of fuselage elasticity needs to be considered in the ground resonance calculation model. Summary of the invention

[0003] Purpose of the invention: To provide a ground resonance calculation method taking into account the influence of fuselage elasticity, improve the accuracy of ground resonance calculation, effectively guide the design in the early stage of development, avoid increasing the repetition of subsequent tests and development design, and reduce the risk of helicopter development.

[0004] Technical solution:

[0005] A ground resonance calculation method considering the influence of fuselage elasticity is provided, including:

[0006] The ground resonance calculation and analysis considering the influence of fuselage elasticity is carried out by establishing a finite element model of the whole aircraft dynamics, simulating and calculating the vibration modal characteristic parameters of the fuselage on the landing gear, considering a certain helicopter loading state and a certain rotor pull, and finally giving the stability margin through stability analysis.

[0007] Furthermore, the ground resonance calculation analysis considering the influence of fuselage elasticity is based on the establishment of a full-aircraft dynamics finite element model, the simulation calculation obtains the vibration modal characteristic parameters of the fuselage on the landing gear, and the calculation is performed under certain helicopter loading conditions and a certain rotor pull. Finally, the stability margin is given through stability analysis, including:

[0008] Obtain the three-dimensional digital model of the helicopter design structure, establish the dynamic finite element models of the components and sections respectively, then assemble and splice the dynamic finite element models of the components and sections, and finally establish the dynamic finite element model of the whole aircraft considering the influence of fuselage elasticity; the sections include: front fuselage, mid-fuselage, transition section, and tail section;

[0009] After selecting a certain loading state and rotor thrust, the helicopter should be in a certain static balance state. According to the mechanical balance relationship of the whole aircraft, the ground load borne by the landing gear under different rotor thrusts is obtained by simulation calculation, and then the position information of the connection points between the landing gear and the fuselage, the wheels of the landing gear and the buffer in the whole aircraft coordinate system and the compression displacement of the wheels of the landing gear and the buffer are obtained;

[0010] According to the position information of the connection points between the landing gear and the fuselage, the wheels of the landing gear and the buffer in the whole aircraft coordinate system and the compression displacement of the wheels of the landing gear and the buffer, a ground resonance calculation model considering the influence of the fuselage elasticity is established;

[0011] According to the ground resonance calculation model which takes into account the influence of fuselage elasticity, the ground resonance calculation is carried out for different loading states and different rotor thrusts, and finally the stability margin is given through stability analysis.

[0012] Furthermore, a three-dimensional digital model of the helicopter design structure is obtained, and the dynamic finite element models of the components and sections are established respectively. Then, the dynamic finite element models of the components and sections are assembled and spliced, and finally a full-aircraft dynamic finite element model considering the influence of fuselage elasticity is established, including:

[0013] Obtain a three-dimensional digital model of the helicopter design structure, which at least includes the fuselage structure, main reducer, and landing gear, and the materials and dimensions of all structures covered by the three-dimensional digital model;

[0014] According to the three-dimensional digital model, the MSC.Patran software is used to establish the dynamic finite element models of the components and sections respectively, and then the dynamic finite element models of the components and sections are assembled and spliced, and finally the dynamic finite element model of the whole aircraft considering the influence of fuselage elasticity is established.

[0015] Furthermore, the full aircraft dynamics finite element model considering the influence of fuselage elasticity follows the mechanical equivalence and mass equivalence principles of structural dynamics finite element modeling:

[0016] Simplifying the structure cannot change the actual force transmission path;

[0017] The unit connection method of the finite element model needs to reflect the actual displacement of the unit nodes;

[0018] The unit material, size and other information parameters of the finite element model should ensure the stiffness equivalence;

[0019] The boundary constraint treatment method of the finite element model should be consistent with the actual situation;

[0020] The mass stacking should ensure that the equivalent principle of mass, center of mass, moment of inertia and product of inertia is met.

[0021] Furthermore, according to the position information of the connection points between the landing gear and the fuselage, the wheels of the landing gear and the buffer in the whole aircraft coordinate system and the compression displacement of the landing gear wheels and the buffer, a ground resonance calculation model considering the influence of the fuselage elasticity is established, including:

[0022] According to the landing gear position information, the coordinate position of the landing gear in the full aircraft dynamics finite element model is changed, and the full aircraft dynamics finite element model of the loading state under different rotor thrusts is established;

[0023] According to the compression displacement of the landing gear wheels and buffers, the stiffness and damping parameters of the landing gear with different rotor pulls under a certain loading state are determined;

[0024] Based on the stiffness, damping parameters, material and size of the landing gear, the attributes of the full aircraft dynamics finite element model were added through MSC.Patran software, and a ground resonance calculation model that takes into account the influence of fuselage elasticity was obtained.

[0025] Furthermore, for different loading states and different rotor thrusts, ground resonance calculations are performed based on a ground resonance calculation model that takes into account the influence of fuselage elasticity. Finally, stability margins are given through stability analysis, including:

[0026] Using MSC.Patran&Nastran software, an in-plane unit force is applied to the center of the blade of the full aircraft dynamics finite element model to simulate the excitation load applied to the hub center, and the vibration modal characteristic parameters of the airframe on the landing gear are obtained after considering the elastic deformation of the airframe.

[0027] The plane dynamics method is used to calculate the ground resonance, the results are analyzed and the conclusions are given.

[0028] Furthermore, the vibration modal characteristic parameters include modal frequency, modal damping and other parameters.

[0029] Beneficial effects: This analytical calculation method is universal for ground resonance calculation analysis considering the influence of fuselage elasticity. The parameters required for calculation can be obtained through simulation or experiment. The calculation and analysis conclusions given can be used to guide model forward design. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Flowchart of the ground resonance calculation method considering the influence of fuselage elasticity. DETAILED DESCRIPTION

[0031] In order to ensure the safety of helicopter take-off and landing and operation, and to effectively eliminate the risk of ground resonance, sufficient calculation analysis and experimental verification are required. The calculation analysis of ground resonance considering the influence of fuselage elasticity is based on the establishment of a full-machine dynamics finite element model, the simulation calculation obtains the vibration modal characteristic parameters of the fuselage on the landing gear, and the calculation is performed under certain helicopter loading conditions and a certain rotor pull, and finally the stability margin is given through stability analysis.

[0032] The present invention provides a method for calculating ground resonance taking into account the influence of fuselage elasticity, such as Figure 1 As shown, the steps are as follows:

[0033] Step 1: Obtain a 3D digital model of the helicopter design structure. The 3D digital model is generally created using CATIA software. The model includes the fuselage structure, main reducer, landing gear, etc. At the same time, the 3D digital model also requires information parameters such as materials and dimensions of all structures covered by the model.

[0034] Step 2: Based on the three-dimensional digital model obtained in step 1, use MSC.Patran software to build the dynamic finite element models of components and sections respectively, and then assemble and splice the dynamic finite element models of components and sections to finally build the dynamic finite element model of the whole aircraft considering the influence of fuselage elasticity. The sections include: front fuselage, mid-fuselage, transition section, and tail section.

[0035] The establishment of a full aircraft dynamics finite element model taking into account the influence of fuselage elasticity generally follows the principles of mechanical equivalence and mass equivalence in structural dynamics finite element modeling:

[0036] 1. Simplification of structure cannot change the actual force transmission path;

[0037] 2. The unit connection method of the finite element model needs to reflect the actual displacement of the unit nodes;

[0038] 3. The unit material, size and other information parameters of the finite element model should ensure the stiffness equivalence;

[0039] 4. The boundary constraint processing method of the finite element model should be consistent with the actual situation;

[0040] 5. Mass accumulation should ensure that the equivalence principle of mass, center of mass, moment of inertia and product of inertia is met.

[0041] Step 3: After selecting a certain loading state and rotor thrust, the helicopter should be in a certain static equilibrium state. According to the mechanical equilibrium relationship of the whole aircraft, the ground load borne by the landing gear under different rotor thrusts is obtained by simulation calculation, and then the position information of the connection points such as the landing gear and the fuselage, the wheels and buffers of the landing gear in the whole aircraft coordinate system and the compression displacement of the wheels and buffers of the landing gear are obtained.

[0042] Step 4: According to the landing gear position information obtained in step 3, the coordinate position of the landing gear in the full aircraft dynamics finite element model is changed, and the full aircraft dynamics finite element model of the loading state under different rotor thrusts is established;

[0043] Step 5: According to the compression displacement of the landing gear wheels and buffers obtained in step 3, determine the stiffness and damping parameters of the landing gear with different rotor thrusts under a certain loading state.

[0044] Step 6: Based on the stiffness and damping parameters of the landing gear and the information parameters such as the material and size of the structure, the attributes of the full aircraft dynamics finite element model are added through the MSC.Patran software to obtain the ground resonance calculation model that takes into account the influence of fuselage elasticity.

[0045] Step 7: Use MSC.Patran&Nastran software to apply an in-plane unit force at the center of the blade of the full aircraft dynamics finite element model to simulate the excitation load applied at the center of the hub, and obtain the vibration modal characteristic parameters of the fuselage on the landing gear after considering the elastic deformation of the fuselage. The vibration modal characteristic parameters include modal frequency, modal damping and other parameters.

[0046] Step 8: Use the plane dynamics method to calculate the ground resonance, analyze the results, and give the analysis conclusion.

[0047] Step 9: According to the development needs, change the loading state of the helicopter and repeat the contents of steps 3 to 8 to obtain the ground resonance calculation model, calculation results and analysis conclusions considering the influence of fuselage elasticity under different loading states and different rotor thrusts.

Claims

1. A method for calculating ground resonance considering the influence of fuselage elasticity, characterized in that: include: The ground resonance calculation and analysis considering the influence of fuselage elasticity is carried out by establishing a finite element model of the whole aircraft dynamics, simulating and calculating the vibration modal characteristic parameters of the fuselage on the landing gear, considering a certain helicopter loading state and a certain rotor pull, and finally giving the stability margin through stability analysis.

2. The method according to claim 1, characterized in that The ground resonance calculation analysis considering the influence of fuselage elasticity is based on the establishment of a full-aircraft dynamics finite element model, the simulation calculation obtains the vibration modal characteristic parameters of the fuselage on the landing gear, and the calculation is performed under certain helicopter loading conditions and a certain rotor pull. Finally, the stability margin is given through stability analysis, including: Obtain the three-dimensional digital model of the helicopter design structure, establish the dynamic finite element models of the components and sections respectively, then assemble and splice the dynamic finite element models of the components and sections, and finally establish the dynamic finite element model of the whole aircraft considering the influence of fuselage elasticity; the sections include: front fuselage, mid-fuselage, transition section, and tail section; After selecting a certain loading state and rotor thrust, the helicopter should be in a certain static balance state. According to the mechanical balance relationship of the whole aircraft, the ground load borne by the landing gear under different rotor thrusts is obtained by simulation calculation, and then the position information of the connection points between the landing gear and the fuselage, the wheels of the landing gear and the buffer in the whole aircraft coordinate system and the compression displacement of the wheels of the landing gear and the buffer are obtained; According to the position information of the connection points between the landing gear and the fuselage, the wheels of the landing gear and the buffer in the whole aircraft coordinate system and the compression displacement of the wheels of the landing gear and the buffer, a ground resonance calculation model considering the influence of the fuselage elasticity is established; According to the ground resonance calculation model which takes into account the influence of fuselage elasticity, the ground resonance calculation is carried out for different loading states and different rotor thrusts, and finally the stability margin is given through stability analysis.

3. The method according to claim 2, characterized in that Obtain the three-dimensional digital model of the helicopter design structure, establish the dynamic finite element models of the components and sections respectively, then assemble and splice the dynamic finite element models of the components and sections, and finally establish the dynamic finite element model of the whole aircraft considering the influence of fuselage elasticity, including: Obtain a three-dimensional digital model of the helicopter design structure, which at least includes the fuselage structure, main reducer, and landing gear, and the materials and dimensions of all structures covered by the three-dimensional digital model; According to the three-dimensional digital model, the MSC.Patran software is used to establish the dynamic finite element models of the components and sections respectively, and then the dynamic finite element models of the components and sections are assembled and spliced, and finally the dynamic finite element model of the whole aircraft considering the influence of fuselage elasticity is established.

4. The method according to claim 3, characterized in that The full aircraft dynamics finite element model considering the influence of fuselage elasticity follows the mechanical equivalence and mass equivalence principles of structural dynamics finite element modeling: Simplifying the structure cannot change the actual force transmission path; The unit connection method of the finite element model needs to reflect the actual displacement of the unit nodes; The unit material, size and other information parameters of the finite element model should ensure the stiffness equivalence; The boundary constraint treatment method of the finite element model should be consistent with the actual situation; The mass stacking should ensure that the equivalent principle of mass, center of mass, moment of inertia and product of inertia is met.

5. The method according to claim 4, characterized in that According to the position information of the connection points between the landing gear and the fuselage, the wheels of the landing gear and the buffer in the whole aircraft coordinate system and the compression displacement of the landing gear wheels and the buffer, a ground resonance calculation model considering the influence of the fuselage elasticity is established, including: According to the landing gear position information, the coordinate position of the landing gear in the full aircraft dynamics finite element model is changed, and the full aircraft dynamics finite element model of the loading state under different rotor thrusts is established; According to the compression displacement of the landing gear wheels and buffers, the stiffness and damping parameters of the landing gear with different rotor pulls under a certain loading state are determined; Based on the stiffness, damping parameters, material and size of the landing gear, the attributes of the full aircraft dynamics finite element model were added through MSC.Patran software, and a ground resonance calculation model that takes into account the influence of fuselage elasticity was obtained.

6. The method according to claim 5, characterized in that According to the ground resonance calculation model considering the influence of fuselage elasticity, the ground resonance calculation is carried out for different loading states and different rotor thrusts. Finally, the stability margin is given through stability analysis, including: Using MSC.Patran&Nastran software, an in-plane unit force is applied to the center of the blade of the full aircraft dynamics finite element model to simulate the excitation load applied to the hub center, and the vibration modal characteristic parameters of the airframe on the landing gear are obtained after considering the elastic deformation of the airframe. The plane dynamics method is used to calculate the ground resonance, the results are analyzed and the conclusions are given.

7. The method according to claim 6, characterized in that The vibration modal characteristic parameters include modal frequency, modal damping and other parameters.

8. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the method according to any one of claims 1 to 7 is implemented.

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