Gear fault simulation method and system based on complex transmission rigid-flexible coupling model

Abstract

The application discloses a gear fault simulation method and system based on a complex transmission rigid-flexible coupling model, and considers time-varying meshing stiffness, transmission error and meshing impact and other nonlinear factors of a gear, simultaneously considers flexible deformation analysis of a weak stiffness component, and establishes a rigid-flexible coupling model of a complex gear transmission system; time-varying meshing stiffness of gear meshing under different fault states is calculated according to an energy method, and gear fault meshing forces under different fault types are calculated according to a lumped parameter model of a fault gear; different types of gear faults are described by implanting different fault meshing forces into gear meshing pairs of the rigid-flexible coupling model of the complex gear transmission system; the rigid-flexible coupling model after implantation of the faults is solved, vibration signal calculation results of the rigid-flexible coupling complex gear transmission system containing the gear faults are obtained, simulation of gear faults in the complex gear transmission system is realized, and support is provided for fault diagnosis of the complex gear transmission system.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of fault simulation of complex transmission gear transmission system, and particularly relates to a gear fault simulation method and system based on a complex transmission rigid-flexible coupling model. BACKGROUND

[0002] In the past 20 years, with the development of gear transmission system towards high power density, high precision, low vibration, high reliability and other directions, the transmission load and design size of complex gear transmission system are further increased. The complex gear transmission system has the advantages of large transmission ratio and strong bearing capacity, and is widely used in the transmission systems of wind turbines, helicopters, heavy vehicles and other equipment. As a key functional component, it is very important to ensure the operation reliability of the complex gear transmission system under complex working conditions. In actual engineering, the operation conditions of equipment are often complex and diverse, and effective actual operation data are difficult to obtain. Therefore, in order to ensure the safe and stable operation of mechanical equipment, timely fault detection and fault diagnosis are implemented to develop corresponding maintenance strategies, and it is very important to accurately study the dynamic performance, fault simulation and fault diagnosis of complex gear transmission system.

[0003] At present, some achievements have been made in the research on gear fault simulation and simulation in transmission system, but in general, there are still the following deficiencies:

[0004] The traditional lumped parameter dynamics model of gear transmission system has certain limitations in establishing the model of complex system, and it is difficult to comprehensively describe the dynamic characteristics of complex gear transmission system. The finite element model considers a large number of degrees of freedom, and can accurately calculate the dynamic characteristics of gear transmission system, but the processing process is complex, the calculation amount is large, and the requirements of computer software and hardware are high. The existing fault simulation research of gear transmission system is mostly based on lumped parameter model or finite element model, but the models established by lumped parameter method and finite element method are mostly simple models, and there are still deficiencies in the fault simulation of complex gear transmission system. The pure rigid body dynamics model of complex gear transmission system ignores the flexible deformation of weak stiffness components in the system, and the flexible deformation of components directly affects the dynamic characteristics of the system as the internal excitation of planetary gear transmission system, and then affects the accuracy of gear fault simulation and simulation results, which is not conducive to accurate diagnosis of faults. The existing multi-body dynamics model of gear transmission system has low accuracy or low calculation efficiency, and it is necessary to consider the flexible deformation of components under the working state of gear transmission system to study the fault simulation of multi-stage complex gear transmission system and improve the calculation accuracy of dynamic response under fault state. On the other hand, flexible deformation provides more modal information for components, and the calculation and analysis time will be greatly increased.

[0005] Therefore, there is an urgent need for a method that can simulate the failure of a complex gear transmission system while ensuring the accuracy and efficiency of the simulation results to some extent. SUMMARY

[0006] The technical problem to be solved by the present application is to provide a gear failure simulation method based on a rigid-flexible coupling model of a complex transmission system to solve the technical problems of difficulty in obtaining fault data of a complex gear transmission system in actual device operation, low simulation accuracy and low simulation calculation efficiency, by considering the deficiencies in the prior art.

[0007] To achieve the above object, the technical scheme adopted by the present application is as follows: a gear failure simulation method based on a rigid-flexible coupling model of a complex transmission system, comprising the following steps:

[0008] According to the two-dimensional topological structure diagram of the complex transmission gear transmission system and the multi-body dynamics principle, the kinematic pairs between components are described by applying bearing force elements and gear force elements, the nonlinear factors including time-varying meshing stiffness, transmission error and meshing impact are considered, and a pure rigid body model of the complex gear transmission system is established;

[0009] According to the load distribution in the actual operation of the gear transmission system and the finite element substructure reduction theory, the gear shaft, the gear ring and the box body which are prone to deformation are flexibilized;

[0010] According to the structure and stress relationship between the components of the gear transmission system, the flexibilized gear shaft, gear ring and box body are coupled with the pure rigid body model of the complex gear transmission system through hinge points and force elements, thereby establishing a rigid-flexible coupling dynamics model of the complex gear transmission system without failure;

[0011] The time-varying meshing stiffness of gear engagement under healthy state and failure state is calculated according to the energy method;

[0012] A translational-torsional coupling dynamics model of gear engagement is established according to the lumped parameter method, and the gear failure engagement force under different failure types is calculated through the translational-torsional coupling dynamics model and the time-varying meshing stiffness;

[0013] The gear failure engagement force under different failure types is implanted into the gear engagement pair of the rigid-flexible coupling dynamics model of the complex gear transmission system to describe different types of gear failure;

[0014] The input torque simulating the power input of the motor is set at the input end of the rigid-flexible coupling dynamic model after the fault is implanted, and the torsional damping is set at the output end to describe the load condition of the gear transmission system, the dynamic simulation model is solved, the calculation result of the vibration signal of the rigid-flexible coupling complex gear transmission system containing the gear fault is obtained, and the simulation analysis of the gear fault in the complex gear transmission system is realized.

[0015] Further, according to the structure of the complex transmission system, the kinematic pair relationship between each component is analyzed and a two-dimensional topological structure diagram of the complex gear transmission system is drawn.

[0016] Further, the established rigid-flexible coupling dynamic model of the complex gear transmission system includes a group of compound planetary gear trains, a group of bevel gears, a plurality of groups of parallel shaft gear transmissions, bearings and a gear transmission system body model.

[0017] Further, the rigid-flexible coupling dynamic model of the complex gear transmission system is established in the multi-body dynamics simulation software SIMPACK according to the principle of the relative coordinate system.

[0018] In the rigid-flexible coupling dynamic model of the complex gear transmission system, the geometric model of each gear is parameterized, and the meshing between gears is simulated by FE225 force elements. FE225 force elements consider many nonlinear factors, including tooth side clearance, time-varying meshing stiffness, time-varying transmission error, gear and transmission shaft fixed hinge, rotate with shaft, transmission shaft and box connected through bearing, transmission shaft and box simulated by FE186 force elements, FE186 force elements apply spring, damping and torque in multiple directions of the shaft, including axial translation, radial translation, axial torsion and tilt torsion between two markers.

[0019] Further, in the established rigid-flexible coupling dynamic model, the flexible body includes: the compound planetary gear train ring gear, the compound planetary gear train pinion, the compound planetary gear train transmission main shaft, the input end transmission shaft and the box;

[0020] In the rigid-flexible coupling dynamic model, the flexible body is created according to the finite element substructure modal reduction method, and the Craig-Bampton component modal synthesis method is used to convert the component overall mass matrix M g and the stiffness matrix K g generated by the finite element method into the reduced mass and stiffness matrices M r and K r , respectively, and the first k modes are retained. The undamped free vibration equation corresponding to the flexible body is:

[0021]

[0022] Wherein:

[0023]

[0024] In the formula, x b and x i are the generalized displacements of the master node and the slave node respectively, which retain the first k modes, X g is the generalized displacement of the whole finite element model node, χ is the modal matrix, and is recorded as:

[0025]

[0026] Ψ i k is the interface modal matrix, is the constraint modal matrix, I is the unit matrix,

[0027] The reduced flexible body is coupled with the rigid body model of other components, and finally a complex gear transmission system rigid-flexible coupling model is established, and the system rigid-flexible coupling dynamics equation is obtained according to the Lagrange principle as:

[0028]

[0029] In the formula: L is the kinetic energy of the system generalized coordinates, ξ is the system generalized coordinates, Γ is the energy loss function, Φ is the system constraint function, λ is the Lagrange multiplier corresponding to the system constraint equation, Q is the projection of the generalized force on Φ,

[0030] According to the above principle, the establishment of the rigid-flexible coupling dynamics model of the complex gear transmission system is completed in the multi-body dynamics software SIMPACK.

[0031] Further, the gear fault types include gear tooth breakage, gear root crack and gear face peeling.

[0032] Further, when the time-varying meshing stiffness of the gear engagement under the healthy state and the fault state is calculated according to the energy method, the time-varying meshing stiffness of the gear under the three fault forms of gear tooth breakage, gear root crack and gear face peeling is calculated by the analytical energy method, and then the finite element method is used for verification.

[0033] According to the verified time-varying meshing stiffness of the gear, the dynamic meshing force F of the gear pair containing the fault is obtained as:

[0034]

[0035] In the formula, k i is the time-varying meshing stiffness of the i pair of gear teeth of the gear pair, c i is the meshing damping coefficient of the i pair of gear teeth of the gear pair, and δ is the dynamic transmission error of the gear pair.

[0036] Further, the gear failure engagement force under different failure types is implanted in the gear engagement pair of the rigid-flexible coupling model of the complex gear transmission system, and when describing different types of gear failures, the calculated failure engagement force is applied to the engagement line of the fault gear of the overall complex gear transmission system rigid-flexible coupling model, and the engagement force containing different failure forms is applied to the gear engagement line, and the modeling of different types of gear failures is completed.

[0037] Further, after the fault implantation is completed, the rigid-flexible coupling model of the complex gear transmission system containing different failure types is simulated in the multi-body dynamics software SIMPACK, the dynamic simulation model is solved according to the SODASRT 2 integral method, the dynamic simulation model realizes the simulation analysis under different working conditions by adjusting the transmission relationship of the compound planetary gear train, and finally the vibration signal of the model is obtained, so as to realize the gear failure simulation calculation based on the rigid-flexible coupling model of the complex gear transmission system.

[0038] In addition, a gear failure simulation system based on a complex transmission rigid-flexible coupling model is provided, which comprises a pure rigid body model construction module, a rigid-flexible coupling dynamics model construction module, a time-varying engagement stiffness acquisition module, a gear failure loading module and an analysis module.

[0039] The pure rigid body model construction module is used to establish a pure rigid body model of the complex gear transmission system by applying bearing force elements and gear force elements to describe the motion pairs between components according to the two-dimensional topological structure diagram of the complex gear transmission system and the multi-body dynamics principle, considering the nonlinear factors including time-varying engagement stiffness of gears, transmission error and meshing impact.

[0040] The rigid-flexible coupling dynamics model construction module is used to flexibly process the gear shaft, gear ring and box that are prone to deformation according to the load distribution in the actual work of the gear transmission system and the finite element substructure reduction theory, and to couple the flexibly processed gear shaft, gear ring and box with the pure rigid body model of the complex gear transmission system through hinge points and force elements according to the structure and stress relationship between the components of the gear transmission system, so as to establish a rigid-flexible coupling dynamics model of the complex gear transmission system without failure.

[0041] The time-varying engagement stiffness acquisition module is used to calculate the time-varying engagement stiffness of gear engagement under healthy state and failure state respectively according to the energy method.

[0042] The gear failure loading module is used to establish a translational-torsional coupling dynamics model of gear engagement according to the lumped parameter method, to calculate the gear failure engagement force under different failure types through the translational-torsional coupling dynamics model and the time-varying engagement stiffness, and to implant the gear failure engagement force under different failure types into the gear engagement pair of the rigid-flexible coupling dynamics model of the complex gear transmission system to describe different types of gear failures.

[0043] The analysis module is used for setting the power input of the input torque simulation motor at the input end of the rigid-flexible coupling dynamics model after implanting the fault, setting the torsional damping at the output end to describe the load condition of the transmission gear transmission system, solving the dynamics simulation model, obtaining the calculation result of the vibration signal of the rigid-flexible coupling complex gear transmission system containing the gear fault, and realizing the simulation analysis of the gear fault in the complex gear transmission system.

[0044] Compared with the prior art, the present application has at least the following beneficial effects:

[0045] The present application establishes a rigid-flexible coupling model of the complex gear transmission system, considers the flexibility of the weak stiffness component, considers the influence of various internal excitations and nonlinear factors under the actual operation condition of the complex gear transmission system on the basis of multi-body dynamics, calculates the time-varying meshing stiffness of the gear under the fault state by using the energy method, finally calculates the fault meshing force, implants the fault meshing force into the rigid-flexible coupling model of the complex system, and finally performs simulation calculation based on the multi-body dynamics software SIMPACK, so that the implantation and simulation calculation of different fault forms can be realized, a large amount of dynamic response data containing fault signals can be obtained, and therefore the demand of the complex gear transmission system fault simulation is met.

[0046] The present application is based on the flexible body modeling theory and the rigid-flexible coupling dynamics theory, considers the flexibility of the large gear ring of the compound planetary gear train, the small gear ring of the compound planetary gear train, the transmission main shaft of the compound planetary gear train, the input end transmission shaft and the box, establishes the weak stiffness component prone to deformation in the actual operation process of the complex gear transmission system as a flexible body, and keeps the remaining components rigid, so that the calculation accuracy is ensured and the calculation efficiency is improved. BRIEF DESCRIPTION OF DRAWINGS

[0047] Figure 1 is a flowchart of the method of the present application;

[0048] Figure 2 is a dynamics model of the complex gear transmission system;

[0049] Figure 3 is a schematic diagram of the gear fault. DETAILED DESCRIPTION

[0050] The present application will be described in detail below in combination with the drawings and specific embodiments.

[0051] The technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings of the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0052] The various structural diagrams according to the disclosed embodiments of the application are shown in the drawings. These diagrams are not drawn to scale, in which certain details are exaggerated for the purpose of clarity, and certain details may be omitted. The shapes of various regions, layers and the relative size and positional relationship therebetween shown in the drawings are only exemplary, and in actuality may deviate due to manufacturing tolerances or technical limitations, and regions / layers with different shapes, sizes and relative positions may be additionally designed according to actual needs by those skilled in the art.

[0053] The application provides a gear fault simulation method based on a complex transmission rigid-flexible coupling model, according to the structure of a complex transmission gear transmission system, the kinematic pair relationship between each component is analyzed and a two-dimensional topological structure diagram of the complex transmission gear transmission system is drawn; based on the two-dimensional topological structure diagram and the principle of multi-body dynamics, the kinematic pairs between components are described by applying bearing force elements and gear force elements, and a pure rigid body model of the complex gear transmission system is established; based on the load distribution in the actual work of the gear transmission system, the finite element substructure reduction theory is used to make the components prone to deformation flexible, such as long gear shafts, gear rings and boxes; according to the structure and stress relationship between each component of the gear transmission system, the flexible processed gear shaft, gear ring and box are coupled with the pure rigid body model of the complex gear transmission system through hinged points and force elements, so as to establish a rigid-flexible coupling dynamics model of the complex gear transmission system without faults. The time-varying meshing stiffness of gear engagement under different fault states is calculated according to the energy method; the translational-torsional coupling dynamics model of gear engagement is established according to the lumped parameter method, and the gear fault engagement force under different fault types is calculated through the translational-torsional coupling dynamics model and the time-varying meshing stiffness; the gear fault engagement force under different fault types is implanted into the gear engagement pair of the rigid-flexible coupling model of the complex gear transmission system, and different types of gear faults are described; the input torque is set at the input end of the rigid-flexible coupling model after implanting the fault to simulate the power input of the motor, and the torsional damping is set at the output end to describe the load condition of the transmission gear transmission system, the dynamics simulation model is solved, the vibration signal calculation result of the rigid-flexible coupling complex gear transmission system containing gear faults is obtained, and the simulation of gear faults in the complex gear transmission system is realized, which provides support for the fault diagnosis of the complex gear transmission system.

[0054] The application provides a gear fault modeling and simulation method based on a complex gear transmission system rigid-flexible coupling model, considering the nonlinear factors such as gear time-varying meshing stiffness, transmission error and meshing impact, and considering the flexible deformation of weak stiffness components, a rigid-flexible coupling model of the complex gear transmission system is analyzed and established, and the gear fault forms simulated based on the model include gear tooth breakage, gear root crack and gear surface peeling, which provides support for the fault diagnosis of the complex gear transmission system and ensures the stable operation of the equipment.Figure 1 As shown, the application proposes a gear fault modeling and simulation method based on a rigid-flexible coupling model of a complex gear transmission system, which contains the following steps:

[0055] S1, according to the structure of the complex transmission gear transmission system, the kinematic pair relationship between each component is analyzed and the two-dimensional topological structure diagram of the complex transmission gear transmission system is drawn.

[0056] S2, based on the two-dimensional topological structure diagram obtained in S1 and the principle of multi-body dynamics, the kinematic pairs between components are described by applying bearing force elements and gear force elements, and a pure rigid body model of the complex gear transmission system is established by using the dynamics software SIMPACK, which specifically includes a fan drive gear assembly, an input end front transmission assembly, a composite planetary gear train and a gear box, etc. The model is specifically as shown in Figure 2 .

[0057] S3, according to the load distribution in the actual work of the gear transmission system, the finite element substructure reduction theory is adopted, and the components prone to deformation are flexibilized, such as long gear shafts, gear rings and boxes, etc. In the rigid-flexible coupling model, the flexible body is created according to the finite element substructure modal reduction method, and the Craig-Bampton component modal synthesis method is used to convert the component overall mass matrix M g and the stiffness matrix K g generated by the finite element method into the reduced mass and stiffness matrices, respectively, M r and K r , the first k modes are retained, and the undamped free vibration equation of the flexible body is:

[0058]

[0059] S4, the flexibilized gear shaft, gear ring and box are coupled with the pure rigid body model through the hinge points and force elements, thereby establishing a rigid-flexible coupling dynamics model of the fault-free complex gear transmission system. According to the Lagrange principle, the rigid-flexible coupling dynamics equation of the complex gear transmission system can be obtained as:

[0060]

[0061] The final differential form of the dynamics equation based on the Lagrange equation is:

[0062]

[0063] Where M, is the mass matrix of the flexible body and its derivative with respect to time, is the derivative of the flexible body generalized coordinate with respect to time, K is the stiffness matrix under the generalized coordinate, f g is the gravity of the multi-body, and D is the damping matrix under the generalized coordinate.

[0064] S5, the time-varying meshing stiffness of the gear meshing in the healthy state and the fault state is calculated respectively according to the energy method, and then verified by the finite element method, the fault types include three types, which are gear tooth breaking, gear root crack and gear surface peeling, and the specific fault forms are as shown in Figure 3 The time-varying meshing stiffness k1 of the single pair of gear meshing of the gear pair can be expressed as:

[0065]

[0066] The time-varying meshing stiffness k2 of the double tooth meshing can be expressed as:

[0067]

[0068] Wherein, i represents the i-th pair of gear teeth, k h is the Hertz contact stiffness of the gear, k a1 , k a2 are the axial compression stiffnesses of the gears 1 and 2 respectively, k b1 , k b2 are the bending stiffnesses of the gears 1 and 2 respectively, k f1 , k f2 are the elastic matrix stiffnesses of the gears 1 and 2 respectively.

[0069] S6, a translational-torsional coupled dynamic model of the gear meshing is established according to the lumped parameter method, the gear fault meshing force under different fault types is calculated through the translational-torsional coupled dynamic model and the time-varying meshing stiffness of the gear obtained in S2; the dynamic meshing force F of the gear pair containing the fault is:

[0070]

[0071] S7, the gear fault meshing force calculated by the analytical method is applied to the meshing line of the fault gear in the whole complex gear transmission system rigid-flexible coupled dynamic model, the meshing force containing different fault forms is applied to the gear meshing line, and different types of gear faults are described by implanting different fault meshing forces into the gear meshing pair of the complex gear transmission system rigid-flexible coupled dynamic model.

[0072] S8, set input torque at the input end of the rigid-flexible coupling dynamic model after implanting the fault to simulate the power input of the motor, set torsional damping at the output end to describe the load condition of the transmission gear transmission system, simulate the rigid-flexible coupling model of the complex gear transmission system containing different fault forms in the multi-body dynamics software SIMPACK, solve the dynamic simulation model according to the SODASRT 2 integral method, adjust the transmission relationship of the compound planetary gear train and the input and output to realize simulation analysis under different working conditions, and finally obtain the vibration signal of the model, so as to realize gear fault simulation calculation based on the rigid-flexible coupling model of the complex gear transmission system.

[0073] In summary, the present application provides a gear fault simulation method based on a complex transmission rigid-flexible coupling model, according to the structure of the complex transmission gear transmission system, based on the topological structure diagram and the multi-body dynamics principle, the motion pairs between components are described by applying bearing force elements and gear force elements, and a pure rigid body model of the complex gear transmission system is established; the weak stiffness components are flexibilized and coupled with the remaining rigid body component model through the hinge point and the force element by using the finite element substructure reduction theory, so as to establish a rigid-flexible coupling dynamic model of the complex gear transmission system without fault. The time-varying meshing stiffness of gear meshing under different fault conditions is calculated according to the energy method; the translational-torsional coupling dynamic model of gear meshing is established according to the lumped parameter method, and the gear fault meshing force under different fault types is calculated through the dynamic model and the time-varying meshing stiffness of gear; different types of gear faults are described by implanting different fault meshing forces into the gear meshing pair of the rigid-flexible coupling model of the complex gear transmission system; the rigid-flexible coupling model after implanting the fault is solved, and the vibration signal calculation result of the rigid-flexible coupling complex gear transmission system containing gear fault is obtained, so as to realize the simulation of gear fault in the complex gear transmission system and provide support for fault diagnosis of the complex gear transmission system.

[0074] Based on the concept of the method, the present application can also provide a gear fault simulation system based on a complex transmission rigid-flexible coupling model, comprising a pure rigid body model construction module, a rigid-flexible coupling dynamic model construction module, a time-varying meshing stiffness acquisition module, a gear fault loading module and an analysis module;

[0075] The pure rigid body model construction module is used to describe the motion pairs between components by applying bearing force elements and gear force elements according to the two-dimensional topological structure diagram of the complex transmission gear transmission system and the multi-body dynamics principle, consider the nonlinear factors including gear time-varying meshing stiffness, transmission error and meshing impact, and establish a pure rigid body model of the complex gear transmission system;

[0076] The rigid-flexible coupling dynamics model construction module is used for flexibly processing the gear shaft, the gear ring and the box which are prone to deformation according to the load distribution in the actual work of the gear transmission system and the finite element substructure reduction theory; the flexibly processed gear shaft, the gear ring and the box are coupled with the pure rigid body model of the complex gear transmission system through the hinge points and the force elements according to the structure and stress relationship between the components of the gear transmission system, so as to establish the rigid-flexible coupling dynamics model of the complex gear transmission system without faults;

[0077] The time-varying meshing stiffness acquisition module is used for respectively calculating the time-varying meshing stiffness of the gear meshing under the healthy state and the fault state according to the energy method;

[0078] The gear fault loading module is used for establishing the translation-torsion coupling dynamics model of the gear meshing according to the lumped parameter method, calculating the gear fault meshing force under different fault types through the translation-torsion coupling dynamics model and the time-varying meshing stiffness, and implanting the gear fault meshing force under different fault types into the gear meshing pair of the rigid-flexible coupling dynamics model of the complex gear transmission system to describe different types of gear faults.

[0079] The analysis module is used for setting the input torque to simulate the power input of the motor at the input end of the rigid-flexible coupling dynamics model after implanting the fault, setting the torsional damping to describe the load condition of the transmission gear transmission system at the output end, solving the dynamics simulation model, obtaining the vibration signal calculation result of the rigid-flexible coupling complex gear transmission system containing the gear fault, and realizing the simulation analysis of the gear fault in the complex gear transmission system.

[0080] The principle and implementation mode of the present application are described by specific examples, and the above examples are only used to help understand the method and core idea of the present application; meanwhile, for the general technical personnel in the art, the specific implementation mode and application range will be changed according to the idea of the present application. In conclusion, the content of the specification should not be understood as the limitation of the present application.

Claims

1. A gear fault simulation method based on a complex transmission rigid-flexible coupling model, characterized in that, The method comprises the following steps: According to the two-dimensional topological structure diagram of the complex transmission gear system and the multi-body dynamics principle, the motion pairs between components are described by applying bearing force elements and gear force elements, the nonlinear factors including time-varying meshing stiffness, transmission error and meshing impact are considered, and a pure rigid body model of the complex gear transmission system is established; According to the load distribution in the actual work of the gear transmission system and the finite element substructure reduction theory, the gear shaft, the gear ring and the box which are prone to deformation are flexibly processed; According to the structure and stress relationship between the components of the gear transmission system, the flexibly processed gear shaft, the gear ring and the box are coupled with the pure rigid body model of the complex gear transmission system through hinged points and force elements, so as to establish a rigid-flexible coupling dynamics model of the complex gear transmission system without failure; The time-varying meshing stiffness of gear engagement under the healthy state and the failure state is calculated according to the energy method; A translation-torsion coupling dynamics model of gear engagement is established according to the lumped parameter method, and the gear fault engagement force under different failure types is calculated through the translation-torsion coupling dynamics model and the time-varying meshing stiffness; The gear fault engagement force under different failure types is implanted into the gear engagement pair of the rigid-flexible coupling dynamics model of the complex gear transmission system, and different types of gear faults are described; The input torque is set at the input end of the rigid-flexible coupling dynamics model after implanting the fault to simulate the power input of the motor, the torsional damping is set at the output end to describe the load condition of the transmission gear transmission system, the dynamics simulation model is solved, the vibration signal calculation result of the rigid-flexible coupling complex gear transmission system containing gear faults is obtained, and the simulation analysis of the gear faults in the complex gear transmission system is realized.

2. The gear fault simulation method based on a complex transmission rigid-flexible coupling model according to claim 1, characterized in that, According to the structure of the complex transmission system, the motion pair relationship between the components is analyzed and a two-dimensional topological structure diagram of the complex transmission gear system is drawn.

3. The gear fault simulation method based on a complex transmission rigid-flexible coupling model according to claim 1, characterized in that, The established rigid-flexible coupling dynamics model of the complex gear transmission system comprises a group of compound planetary gear trains, a group of bevel gears, a plurality of groups of parallel shaft gear transmissions, bearings and a gear transmission system body model.

4. The gear fault simulation method based on a complex transmission rigid-flexible coupling model according to claim 1, characterized in that, The rigid-flexible coupling dynamics model of the complex gear transmission system is established in the multi-body dynamics simulation software SIMPACK according to the principle of the relative coordinate system; In the rigid-flexible coupling dynamics model of the complex gear transmission system, the geometric models of the gears at all levels are parameterized, the meshing between the gears is simulated by FE225 force elements, the FE225 force elements consider many nonlinear factors, including the backlash, the time-varying meshing stiffness and the time-varying transmission error, the gears are fixedly hinged with the transmission shafts and rotate with the shafts, the transmission shafts are connected with the box through bearings, the transmission shafts and the box are simulated by FE186 force elements, the FE186 force elements apply spring, damping and torque in multiple directions of the shaft, including the axial translation, the radial translation, the axial torsion and the inclined torsion between two markers.

5. The gear fault simulation method based on a complex transmission rigid-flexible coupling model according to claim 1, characterized in that, In the established rigid-flexible coupling dynamics model, the flexible bodies include the compound planetary gear train large gear ring, the compound planetary gear train small gear ring, the compound planetary gear train transmission main shaft, the input end transmission shaft and the box. In the rigid-flexible coupling dynamics model, the flexible body is created according to the finite element substructure modal reduction method, and the Craig-Bampton component modal synthesis method is used to convert the component overall mass matrix M g and the stiffness matrix K g generated by the finite element method into the reduced mass matrix M r and the stiffness matrix K r , respectively, and the first k modes are retained, and the undamped free vibration equation of the flexible body is: In the established rigid-flexible coupling dynamics model, the flexible bodies include the compound planetary gear train large gear ring, the compound planetary gear train small gear ring, the compound planetary gear train transmission main shaft, the input end transmission shaft and the box. In the formula, x b and x i are the generalized displacements of the master node and the slave node respectively, which retain the first k modes, X g is the generalized displacement of the whole finite element model node, and χ is the modal matrix, which is denoted as: where Ψ i k is the interface modal matrix, Ψ c k is the constraint modal matrix, I is the identity matrix, The reduced flexible body is coupled with other rigid body models of components, and finally a complex gear transmission system rigid-flexible coupling model is established. The rigid-flexible coupling dynamics equation of the system is obtained according to the Lagrange principle as follows: In the formula, L is the kinetic energy of the system generalized coordinates, ξ is the system generalized coordinates, Γ is the energy loss function, Φ is the system constraint function, λ is the Lagrange multiplier corresponding to the system constraint equation, Q is the projection of generalized force on Φ, According to the above principle, the establishment of the rigid-flexible coupling dynamics model of the complex gear transmission system is completed in the multi-body dynamics software SIMPACK.

6. The gear fault simulation method based on a complex transmission rigid-flexible coupling model according to claim 1, characterized in that, Gear failure types include gear tooth breakage, gear root crack and gear face spalling.

7. The gear fault simulation method based on a complex transmission rigid-flexible coupling model according to claim 1, characterized in that, According to the energy method, the time-varying meshing stiffness of the gear meshing under the healthy state and the fault state is calculated respectively. First, the time-varying meshing stiffness of the gear under three fault forms of gear tooth breakage, gear root crack and gear face spalling is calculated by analytical energy method, and then it is verified by finite element method. According to the verified time-varying meshing stiffness of the gear, the dynamic meshing force F of the gear pair containing faults is obtained as follows: where k i is the time-varying mesh stiffness of the ith pair of teeth of the gear pair, c i is the mesh damping coefficient of the ith pair of teeth of the gear pair, and δ is the dynamic transmission error of the gear pair.

8. The gear fault simulation method based on a complex transmission rigid-flexible coupling model according to claim 1, characterized in that, The gear fault meshing force under different fault types is implanted into the gear meshing pair of the complex gear transmission system rigid-flexible coupling model. When describing different types of gear faults, the calculated fault meshing force is applied to the meshing line of the overall complex gear transmission system rigid-flexible coupling model fault gear. The meshing force containing different fault forms is applied to the gear meshing line, and the modeling of different types of gear faults is completed.

9. The gear fault simulation method based on a complex transmission rigid-flexible coupling model according to claim 1, characterized in that, After the fault implantation is completed, the rigid-flexible coupling model of the complex gear transmission system containing different fault types is simulated in the multi-body dynamics software SIMPACK. The dynamics simulation model is solved according to the SODASRT 2 integration method. The dynamics simulation model realizes the simulation analysis under different working conditions by adjusting the transmission relationship of the compound planetary gear train, and finally the vibration signal of the model is obtained, thereby realizing the gear fault simulation calculation based on the complex gear transmission system rigid-flexible coupling model.

10. A gear fault simulation system based on a rigid-flexible coupling model of a complex transmission system, characterized in that, The system includes a pure rigid body model construction module, a rigid-flexible coupling dynamics model construction module, a time-varying meshing stiffness acquisition module, a gear fault loading module and an analysis module. The pure rigid body model construction module is used to establish a pure rigid body model of a complex gear transmission system according to the two-dimensional topological structure diagram of the complex transmission gear transmission system and the multi-body dynamics principle, by applying bearing force elements and gear force elements to describe the motion pairs between components, considering nonlinear factors including gear time-varying meshing stiffness, transmission error and meshing impact. The rigid-flexible coupling dynamics model construction module is used to flexibly process the gear shaft, gear ring and box that are prone to deformation according to the load distribution of the gear transmission system in actual work and the finite element substructure reduction theory; the flexibly processed gear shaft, gear ring and box are coupled with the pure rigid body model of the complex gear transmission system through hinge points and force elements according to the structure and stress relationship between the components of the gear transmission system, so as to establish a rigid-flexible coupling dynamics model of the complex gear transmission system without faults. The time-varying meshing stiffness acquisition module is used to calculate the time-varying meshing stiffness of the gear meshing under the healthy state and the fault state respectively according to the energy method. The gear fault loading module is used for establishing a translational-torsional coupled dynamic model of gear engagement according to the lumped parameter method, and calculating the gear fault engagement force under different fault types through the translational-torsional coupled dynamic model and the time-varying engagement stiffness; The gear fault engagement force under different fault types is implanted into the gear engagement pair of the rigid-flexible coupled dynamic model of the complex gear transmission system, so as to describe different types of gear faults. The analysis module is used for setting the input torque simulation motor power input at the input end of the rigid-flexible coupled dynamic model after implanting the fault, setting the torsional damping at the output end to describe the load condition of the transmission gear transmission system, solving the dynamic simulation model, obtaining the vibration signal calculation result of the rigid-flexible coupled complex gear transmission system containing the gear fault, and realizing the simulation analysis of the gear fault in the complex gear transmission system.

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