Method for identifying main transmission path of main vibration reduction of closed differential coaxial helicopter

Abstract

The invention provides a method for identifying a main transmission path of main vibration reduction of a closed differential coaxial helicopter, and relates to the technical field of vibration state analysis. Establishing an energy loss calculation model of the junction surfaces between the boxes and between the bearing and the bearing seat, and obtaining junction surface characteristic parameters; coupling the interface characteristic parameters, the transmission system dynamical model and the box polycondensation model, and establishing a main reducer dynamical model; setting an excitation source and a target point, and determining a transmission path. Selecting a coupling point of each transmission path, solving the kinetic equation, and calculating the power flow of the kinetic equation; simulating to obtain the energy transmission rate of each transmission path from the coupling point to the target point; multiplying the power of each path coupling point by the energy transmission rate to obtain the transmission power of each path; the path contribution degree of each transmission path is calculated, the main transmission path is determined, and fault diagnosis of the main speed reducer is facilitated.

Description

Technical Field

[0001] The present invention relates to the technical field of vibration state analysis, and particularly to a method for identifying the main transmission paths of vibration of a main reducer of a coaxial helicopter with a closed differential Background Art

[0002] The coaxial helicopter has no tail rotor arrangement and uses two sets of upper and lower rotors with coaxial reverse rotation to balance torque. While providing greater lift, it reduces the risk of crashing caused by tail rotor failure, has irreplaceable advantages over single-rotor helicopters, and is one of the typical configurations of existing high-speed helicopters. As one of the key configurations of the main reducer of a coaxial helicopter, the closed differential gear train has the advantages of a compact structure and strong load-bearing capacity, and is widely used. Due to the complex working environment and large loads, the main reducer is prone to faults such as gear tooth root cracks, tooth surface pitting, and local bearing damage, which may lead to major accidents and losses to personal safety. However, the transmission system of the closed differential gear train has a complex structure, and the internal fault source signals need to pass through multiple transmission paths and multiple interfaces before being transmitted to the box body. In order to clarify the load transmission mechanism of the coupled structure of the transmission components, analyze the transmission and amplitude attenuation of vibrations caused by component faults inside the coaxial main reducer, and identify the main transmission paths, it is of great significance for the arrangement of fault detection sensors of the main reducer, fault diagnosis, and vibration reduction and noise reduction of the main reducer.

[0003] At present, the research objects for identifying the contribution degree of transmission paths and the main transmission paths are mostly the surfaces of simple gearboxes or fixed-axis gearboxes. There is less research on identifying the main transmission paths for planetary gearbox, especially for the main reducer of a coaxial helicopter with a multi-stage planetary gear train. There is no identification method for the main transmission paths of the main reducer of a coaxial helicopter with a closed differential. The power flow method, as one of the commonly used methods for identifying the main transmission paths, has the following main defects when applied to the main reducer of a coaxial helicopter: First, when establishing the dynamic model of the transmission path, existing research only considers the dynamic model of the transmission system inside the gearbox body and does not couple the dynamic model of the box body; second, existing research does not consider the energy loss problems at transmission interfaces such as the box body joint surface and the bearing joint surface; finally, existing research on the energy transfer rate is usually determined based on the transmission path length or obtained through finite element simulation. However, the former is mainly obtained by artificially giving the expression of vibration energy amplitude attenuation, and the latter does not eliminate the mutual coupling effect between paths, and the applied excitation is mostly sinusoidal excitation, both of which have no practical physical meaning. Summary of the Invention

[0004] To solve the problems existing in the prior art, the present invention discloses a method for identifying the main transmission paths of vibration of a main reducer of a coaxial helicopter with a closed differential, and solves the problem of how to accurately identify the main transmission paths of a coaxial helicopter main reducer with a multi-stage planetary gear train.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for identifying the main vibration transmission paths of a closed differential coaxial helicopter main reducer, comprising the following steps:

[0007] 1) Calculate the characteristic parameters of the bonding interfaces between the boxes and between the bearings and the bearing seats;

[0008] 2) Establish a dynamic model of the main reducer;

[0009] 3) Set the excitation source and the target points, and determine the transmission paths; select the coupling points of each transmission path, solve the dynamic equations, and calculate their power flows;

[0010] 4) Apply excitation at the coupling points, and simulate to obtain the energy transfer rates of each transmission path from the coupling points to the target points;

[0011] 5) Multiply the power at the coupling points of each transmission path by the energy transfer rate to calculate the power transmitted from the excitation source to the target points for each path;

[0012] 6) Sum the powers transmitted to the target points for each path to obtain the total power at the target point; calculate the ratio of the power transmitted by each path to the total power at the target point to obtain the contribution degrees of each transmission path.

[0013] Further, in the step 1), based on the finite element method or the experimental method, obtain the hysteresis loops of the bolt connection interfaces between the upper box and the middle box, between the middle box and the lower box, and the contact interfaces between the outer rings of the bearings and the bearing seats; analyze the hysteresis loops and calculate the interface characteristic parameters such as the equivalent stiffness and damping of the interfaces.

[0014] Further, in the step 2), first, based on the lumped mass method, establish a dynamic model of the main reducer transmission system; based on the finite element method, establish a dynamic condensation model of the box; the dynamic equation of the box condensation model is:

[0015]

[0016] In the formula, q x is the vibration displacement vector of the box condensation nodes, q x ={q sx ,q zx ,q xx} T ; Q x is the load vector, Q x ={Q sx ,Q zx ,Q xx} T ; M x is the mass matrix of the box condensation nodes, C xis the damping matrix of the condensed nodes of the housing, and K x is the stiffness matrix of the condensed nodes of the housing. The expressions of each matrix are as follows:

[0017]

[0018] In the formula, M sx 、M zx、 M xx are the mass matrices composed of the condensed nodes of the upper housing, the middle housing, and the lower housing respectively. C sx 、C zx 、C xx are the damping matrices composed of the condensed nodes of the upper housing, the middle housing, and the lower housing respectively; are the damping matrices of the coupling bolts of the condensed nodes of the upper housing, the middle housing, and the lower housing respectively; are the damping matrices of the joint surfaces of the upper housing, the middle housing, and the lower housing respectively; K sx 、K zx 、K xx are the stiffness matrices of the condensed nodes of the upper housing, the middle housing, and the lower housing respectively; are the stiffness matrices of the coupling bolts of the condensed nodes of the upper housing, the middle housing, and the lower housing respectively; are the equivalent stiffness matrices of the joint surfaces of the upper housing, the middle housing, and the lower housing respectively.

[0019] Furthermore, based on the deformation compatibility condition, the above dynamic model of the main reducer transmission system and the dynamic model of the condensed housing, and the interface characteristic parameters obtained in the step 1) are coupled to obtain the dynamic model of the main reducer, thereby constructing the vibration transfer model of the main reducer; the expression of the dynamic model of the main reducer is:

[0020]

[0021] In the formula, C tx 、C xt are the coupling damping matrices of the main reducer transmission system and the housing respectively, and K tx 、K xt are the coupling stiffness matrices of the main reducer transmission system and the housing respectively. q t and Q t are the node vibration displacement vector of the transmission system and the load vector respectively.

[0022] Furthermore, in the step 3), taking the gear pair meshing frequency, faulty gears, bearings, etc. of the internal transmission system of the main reducer as the excitation sources, target points are set on the main reducer housing; based on the physical structure of the main reducer, the transmission paths from the excitation sources to the target points are determined; the coupling points of each transmission path are determined, the dynamic differential equations are solved to obtain the velocities and forces of the coupling points, and the power P ci。

[0023] Further, in step 4), only the components between the coupling point and the target point on each transmission path are retained, other components are removed, and a three-dimensional model of each transmission path from the coupling point to the target point is established; with the aid of finite element software, according to the actual force condition at the coupling point, an excitation is applied at the coupling point; the power P of the excitation point is obtained by simulation oi and the power P of the target point mi , according to formula A i =P mi / P oi , the energy transfer rate A of each transmission path from the coupling point to the target point is calculated i 。

[0024] Further, in step 5), according to the formula P i =P ci ×A i , the power P transmitted from the excitation source to the target point of each transmission path is obtained i 。

[0025] Further, in step 6), the total power P of the target point t is the sum of the powers of each transmission path. According to formula B i =P i / P t , the contribution degree B of each transmission path is obtained i , and the transmission path with a large contribution degree is considered the main transmission path.

[0026] Compared with the prior art, the present invention has at least the following beneficial effects:

[0027] Based on the solution of the dynamic equation of the coaxial helicopter main reducer, the power of the coupling points of each path is obtained. At the same time, based on the finite element method, the energy transfer rate from the coupling point to the target point of each path is obtained, and the two are multiplied to quantitatively obtain the contribution degree of each transmission path, so as to identify the main transmission path of the coaxial helicopter main reducer.

[0028] The objects of existing research on the contribution degree of transmission paths are mostly for the surface of a simple gearbox or a fixed-axis gear pair. For a planetary gear train, especially a multi-stage planetary gear train gearbox, there is less research on the contribution degree of the excitation source in the internal transmission of the transmission system. The present invention proposes a method for identifying the main transmission path of the vibration of a closed differential coaxial helicopter main reducer. Secondly, the present invention obtains the dynamic model of the main reducer by obtaining the dynamic model of the box body based on the condensation method and coupling it with the dynamic model of the transmission system. Thus, the influence of the box body on energy transfer is considered, which is more in line with the actual situation.

[0029] Existing research does not take into account the energy loss caused by the transmission interface. In the present invention, through the hysteresis loops of the box joint surface and the joint surface between the outer ring of the bearing and the bearing housing, the nonlinear characteristic parameters such as the stiffness and damping of the joint interface are analyzed and calculated. And they are coupled into the dynamic model of the system to make the calculation results closer to the actual situation.

[0030] Existing research on the energy transfer rate is usually determined based on the transmission path length or obtained by the finite element simulation method.

[0031] The former is mainly obtained by artificially giving the expression of the vibration energy amplitude attenuation, and the latter does not eliminate the mutual coupling effect between the paths, and the applied excitation is mostly sinusoidal excitation, both of which have no practical physical meaning. In the present invention, only the components between the coupling point and the target point on each transmission path are retained, and other components are removed to establish a three-dimensional model of each transmission path from the coupling point to the target point. With the help of finite element software, according to the actual force condition at the coupling point, excitation is applied. Therefore, the solution of the energy transfer rate is more in line with the actual situation and more accurate, and is suitable for the calculation of the energy transfer rate of the coaxial helicopter main reducer with complex structure and multiple transmission paths.

[0032] To achieve flight in different directions, generally different working conditions are required for coaxial helicopters. However, different working conditions correspond to different main transmission paths. When existing research obtains the contribution degree of the transmission path by the finite element method, it is necessary to apply each working condition separately for simulation, which requires a large amount of time cost. In the dynamic model based on the lumped parameter method proposed by the present invention, working condition parameters such as the rotational speed and torque of the system are introduced. By solving the dynamic equation, the variation law of the contribution degree of the transmission path of the coaxial helicopter main reducer with the working condition can be conveniently obtained.

[0033] Vibration reduction, noise reduction and health management of helicopters are all particularly important. Through the method described in the present invention, the contribution degree of the fault excitation source on each transmission path in the complex interior of the main reducer can be quantitatively and accurately given, so as to identify the main transmission path. The vibration reduction and noise reduction of the system can be achieved by changing the parameters of the main transmission path. At the same time, by reasonably arranging sensors on the main transmission path, it is beneficial to the fault detection and diagnosis of the main reducer.

[0034] The present invention also provides a device, including a memory, a processor and a computer program stored on the memory and executable on the processor. When the processor executes the computer program, the steps of the method are implemented.

[0035] The present invention also provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the method are implemented. Description of the Drawings

[0036] Figure 1 is a flowchart of the method described in the present invention;

[0037] Figure 2 is the working principle diagram of the main reducer described in the present invention;

[0038] Figure 3 is the condensed dynamic model diagram of the main reducer housing described in the present invention;

[0039] Figure 4 are multiple transmission paths from the excitation source to the target point of the main reducer described in the present invention;

[0040] Figure 5 is the selection of the coupling points of each transmission path described in the present invention;

[0041] Figure 6 is the graph showing the variation law of the contribution degree of each transmission path with the input rotational speed described in the present invention

[0042] Figure 7 is the graph showing the variation law of the contribution degree of each transmission path with the load torque described in the present invention. Detailed implementation manners

[0043] The present invention will be elaborated in detail below with reference to the accompanying drawings.

[0044] There are the following problems in the existing calculation of the contribution degree of the vibration signal transmission path. 1. Most of the research objects are the surfaces of simple gearboxes or fixed-axis gearboxes. For planetary gearbox, especially the multi-stage coaxial helicopter main reducer composed of star gear train and planetary gear train, there is less research on the identification of the main transmission paths. 2. When the existing calculation method of the transmission path contribution degree is applied to the coaxial helicopter main reducer, when establishing the dynamic model of the transmission path, usually only the dynamic model of the transmission system inside the gearbox is considered, and the influence of the housing on the vibration response is rarely considered. 3. The influence of the energy loss caused by the joint interface is not taken into account in the existing research. 4. Regarding the energy transfer rate, usually an expression of the energy amplitude attenuation is artificially given. When obtaining the energy transfer rate through finite element method simulation, the mutual coupling effect between the transmission paths is not eliminated, and the applied excitation is mostly sinusoidal excitation, which has no practical physical meaning. In view of the above problems, taking the transmission system of a coaxial helicopter main reducer based on a closed differential gear train as the research object, as Figure 2 shown, the present invention proposes a calculation method for the contribution degree of the transmission path that couples the energy loss at the transmission interface, the condensed dynamic model of the housing, and the energy transfer rate. Reasonably arranging sensors on the identified main transmission paths is beneficial to the fault detection and diagnosis of the main reducer system, so it has certain engineering significance.

[0045] As Figures 2 to 4As shown in the figure, the main reducer includes an upper housing, a middle housing, a lower housing, an input bevel gear pair, a fixed-axis star gear train (closed stage), a planetary gear train (differential stage), a double-connected internal gear ring, an internal output shaft, and an external output shaft. The closed stage includes a sun gear s1, a star gear a, a star gear b, and an internal gear ring r1. The planetary gear train includes a sun gear s2, a planetary gear p, and an internal gear ring r2.

[0046] The calculation method for identifying the main transmission path of the coaxial helicopter main reducer proposed by the present invention includes the following steps:

[0047] S1. Obtain the hysteresis loops of the mating interfaces between the upper housing and the middle housing, the middle housing and the lower housing, and the bearing and the bearing seat through finite element simulation. Fit the hysteresis loops to obtain the interface nonlinear characteristic parameters such as the equivalent stiffness and damping of the mating surface.

[0048] S2. Establish a dynamic model of the transmission system according to the structure of the transmission system.

[0049]

[0050] In the formula, M t is the mass matrix of the transmission system, C t is the damping matrix of the transmission system, K t is the stiffness matrix of the transmission system, q t is the vibration displacement vector of each node of the transmission system, and Q t is the vector of the applied force and torque. The dynamic model of the transmission system and the expressions of the matrices and vectors listed above are cited from the Ph.D. thesis "Research on the Dynamic Characteristics of the Coaxial Helicopter Main Reducer Based on a Closed Differential Gear Train" by Dr. Zhang Donglin of Nanjing University of Aeronautics and Astronautics, P29-32, P66.

[0051] Combined with the characteristic parameters of the housing mating surface obtained in S1, obtain the dynamic condensation model of the main reducer housing. The model is as Figure 3 shown. The dynamic equation of the housing is as follows:

[0052]

[0053] In the formula, q x is the vibration displacement vector of the condensed nodes of the housing, q x ={q sx ,q zx ,q xx} T ; Q x is the load vector, Q x ={Q sx ,Q zx ,Q xx} T . M x is the mass matrix of the condensed nodes of the housing, Cx is the damping matrix of the lumped nodes of the housing, and K x is the stiffness matrix of the lumped nodes of the housing. The expressions of each matrix are as follows:

[0054]

[0055] In the formula, M sx and M zx、 M xx are the mass matrices composed of the lumped nodes of the upper housing, the middle housing, and the lower housing respectively. C sx and C zx and C xx are the damping matrices of the lumped nodes of the upper housing, the middle housing, and the lower housing respectively. are the damping matrices of the connecting bolts of the lumped nodes of the upper housing, the middle housing, and the lower housing respectively. are the damping matrices of the joint surfaces of the upper housing, the middle housing, and the lower housing respectively. K sx and K zx and K xx are the stiffness matrices of the lumped nodes of the upper housing, the middle housing, and the lower housing respectively. are the stiffness matrices of the connecting bolts of the lumped nodes of the upper housing, the middle housing, and the lower housing respectively. are the equivalent stiffness matrices of the joint surfaces of the upper housing, the middle housing, and the lower housing respectively.

[0056] Couple the dynamic model of the transmission system and the lumped dynamic model of the housing to establish the dynamic model of the main reducer.

[0057]

[0058] In the formula, C tx and C xt are the coupled damping matrices of the main reducer transmission system and the housing respectively, and K tx and K xt are the coupled stiffness matrices of the main reducer transmission system and the housing respectively.

[0059] S3. Set the sun gear s1 of the fixed-axis gear train with a tooth root crack fault as the excitation source, and set a target point on the upper housing near the bearing seat of the outer output shaft. According to the structural characteristics of the transmission system, determine all the transmission paths from the excitation source to the target point. In Figure 4 there are 4 transmission paths in the shown main reducer transmission system. Substitute the time-varying meshing stiffness caused by the s1 crack fault into the dynamic model of the main reducer transmission system described in S2. Select the coupling points of each transmission path, such as Figure 5As shown in the figure. Among them, the coupling point of transmission path 1 is the support bearing of star wheel a, the coupling point of transmission path 2 is star wheel b, the coupling point of transmission path 3 is internal gear ring r2, and the coupling point of transmission path 4 is the support bearing of the outer output shaft. Solve the dynamic equation described in S2. According to the formula P ci =v ix ×F ix +v iy ×F iy +v iθz ×F iθz , the total power P ci of the coupling point of the i-th transmission path is obtained. Among them, v ix and v iy represent the radial velocities of the coupling point of the i-th transmission path along the x-axis and y-axis, and v iθz represents its velocity in the torsional direction along the z-axis. F ix , F iy represent the radial forces of the coupling point of the i-th transmission path along the x-axis and y-axis, and F iθz represents the force in its torsional direction along the z-axis.

[0060] S4. Only retain the components between the coupling point and the target point on each transmission path, remove other components, and establish a three-dimensional model of each transmission path from the coupling point to the target point. With the help of finite element software, by applying corresponding force excitations at the coupling point, according to the formula A i =P mi / P oi , the energy transfer rate A i of the i-th transmission path from the coupling point to the target point is calculated; where P oi is the power of the excitation point of the i-th transmission path, and P mi is the power transmitted from the excitation source to the target point through the i-th path.

[0061] S5. Multiply the power Pc i at the coupling point of the i-th transmission path obtained in S3 by the energy transfer rate A i obtained in S4, and calculate the power P i transmitted from the excitation source to the target point through the i-th transmission path. P i =P ci ×A i .

[0062] S6. Sum the power P i transmitted from the excitation source to the target point through the i-th path obtained in S5 to obtain the total power P t of the target point. Among them, the parameter n represents that there are n transmission paths from the excitation source to the target point. By calculating the ratio of the power transmitted through the i-th path to the total power of the target point, the contribution degree B of each transmission path is obtainedi , B i = P i / P t . When the load torque is 1000 Nm and the rotational speed is 2000 r / min, the contribution degrees of the 4 transmission paths described in S3 are 0.12, 0.44, 0.40, and 0.04 in sequence. Therefore, under this working condition, transmission path 2 is the main transmission path. In addition, the contribution degree of the transmission path changes with the input rotational speed, and the variation law is as Figure 6 shown. Generally, when the input rotational speed varies within the range of 2000 rpm - 8000 rpm, the contribution degree of transmission path 4 is always the smallest, so this transmission path can be ignored. The contribution degree of transmission path 3 is always less than that of transmission path 2. And when the input rotational speed is 2000 rpm - 4275 rpm and 6950 rpm - 8000 rpm, the contribution degree ranking is: transmission path 2 > transmission path 3 > transmission path 1; when the input rotational speed is between 4275 rpm - 4900 rpm and 6650 rpm - 6950 rpm, the contribution degree ranking is: transmission path 2 > transmission path 1 > transmission path 3; when the input rotational speed is 4900 rpm - 6650 rpm, the contribution degree ranking is: transmission path 1 > transmission path 2 > transmission path 3. When the input rotational speed is set to 2000 rpm, the variation law of the transmission path contribution degree with the load torque is as Figure 7 shown. It can be seen from the figure that the ranking of the contribution degrees of each transmission path, that is, the main transmission path, remains unchanged with the load torque.

[0063] The above content is only to illustrate the technical idea of the present invention, and the protection scope of the present invention cannot be limited thereby. Any modification made on the basis of the technical solution according to the technical idea proposed by the present invention falls within the protection scope of the claims of the present invention.

Claims

1. A method for identifying the main transmission path of the main vibration reduction of a closed differential coaxial helicopter, characterized in that: The following steps are involved: 1) Calculate the characteristic parameters of the interface between the housing and the housing, and between the bearing and the bearing seat; 2) Establish the dynamic model of the main reducer; 3) Set the excitation source and target point and determine the transfer path; Select the coupling points of each transfer path, solve the dynamic equations, and calculate its power flow; 4) Apply excitation at the coupling point and simulate to obtain the energy transfer rate from the coupling point to the target point on each transfer path; 5) Multiply the power at the coupling point of each transfer path by the energy transfer rate to calculate the power transmitted from the excitation source to the target point on each path; 6) Sum the power transmitted from each path to the target point to obtain the total power of the target point; calculate the ratio of the power transmitted from each path to the total power of the target point to obtain the contribution of each transmission path.

2. The method for identifying the main transmission path of the main vibration reduction of a closed differential coaxial helicopter according to claim 1, characterized in that: In the step 1), based on finite element or experimental method, the hysteresis loops of the bolt connection interface between the upper box and the middle box, the middle box and the lower box, and the contact interface between the bearing outer ring and the bearing seat are obtained; the hysteresis loops are analyzed to calculate the interface characteristic parameters such as equivalent stiffness and damping of the interface.

3. The method for identifying the main transmission path of the main vibration reduction of a closed differential coaxial helicopter according to claim 1, characterized in that: In the step 2), firstly, a dynamic model of the main reducer transmission system is established based on the concentrated mass method; and a dynamic polycondensation model of the housing is established based on the finite element method; the dynamic equation of the housing polycondensation model is: In the formula, q x is the vibration displacement vector of the box condensation node, q x = {q sx ,q zx ,q xx } T ;Q x is the load vector, Q x = {Q sx ,Q zx ,Q xx } T ; M x is the mass matrix of the box condensation node, C x is the damping matrix of the box condensation node, K x is the stiffness matrix of the box condensation node; the matrix expressions are as follows: Where M sx 、M zx、 M xx are the mass matrices composed of the condensed nodes of the upper box, middle box and lower box respectively; C sx , C zx , C xx are the damping matrices composed of the condensed nodes of the upper box, middle box and lower box respectively; are the damping matrices of the condensation node connection bolts of the upper box, middle box and lower box respectively; are the damping matrices of the joint surfaces of the upper box, middle box and lower box respectively; K sx , K zx , K xx are the stiffness matrices of the condensation nodes of the upper box, middle box, and lower box respectively; are the stiffness matrices of the connection bolts of the condensation nodes of the upper box, middle box and lower box respectively; are the equivalent stiffness matrices of the joint surfaces of the upper box, middle box and lower box respectively.

4. The method for identifying the main transmission path of the main vibration reduction of a closed differential coaxial helicopter according to claim 3, characterized in that: Based on the deformation coordination condition, the above-mentioned main reducer transmission system dynamics model and the box polycondensation dynamics model, as well as the interface characteristic parameters obtained in step 1) are coupled to obtain the dynamics model of the main reducer, thereby constructing the main reducer vibration transmission model; the main reducer dynamics model expression is: In the formula, C tx , C xt are the main reducer transmission system and the housing coupling damping matrix, K tx , K xt are the coupling stiffness matrices of the main reducer transmission system and the housing; q t and Q t are the node vibration displacement vector and load vector of the transmission system respectively.

5. The method for identifying the main transmission path of the main vibration reduction of a closed differential coaxial helicopter according to claim 1, characterized in that: In the step 3), the gear pair meshing frequency, faulty gear, bearing, etc. of the internal transmission system of the main reducer are used as excitation sources, and a target point is set on the main reducer housing; based on the physical structure of the main reducer, a transmission path from the excitation source to the target point is determined; Determine the coupling points of each transmission path, solve the dynamic differential equation, obtain the speed and force of the coupling point, and determine the power P of the coupling point ci .

6. The method for identifying the main transmission path of the main vibration reduction of a closed differential coaxial helicopter according to claim 5, characterized in that: In the step 4), only the components between the coupling point and the target point on each transmission path are retained, and other components are removed, and a three-dimensional model of each transmission path from the coupling point to the target point is established; With the help of finite element software, excitation is applied at the coupling point according to the actual force condition of the coupling point; the power P at the excitation point is obtained by simulation. oi And the power P of the target point mi , according to formula A i =P mi / P oi , calculate the energy transfer rate A from the coupling point to the target point of each transmission path i .

7. The method for identifying the main transmission path of the main vibration reduction of a closed differential coaxial helicopter according to claim 6, characterized in that: In step 5), the coupling point power and energy transfer rate are calculated according to the formula P i =P ci ×A i , obtain the power P transmitted from the excitation source to the target point on each transmission path i .

8. The method for identifying the main transmission path of the main vibration reduction of a closed differential coaxial helicopter according to claim 7, characterized in that: In step 6), the total power P of the target point t is the sum of the power of each transmission path; according to formula B i =P i / P t , obtain the contribution B of each transmission path i , the transmission path with large contribution is considered to be the main transmission path.

9. A device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 8 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 8 are implemented.

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