Vehicle NVH calculation method based on modal supercell

Abstract

The present invention discloses a whole vehicle NVH calculation method based on modal super units, comprising constructing a whole vehicle model and dividing a TB model and a chassis model, respectively condensing them into super units, and connecting each modal super unit; collecting and obtaining boundary conditions, connection point freedom constraints, modal frequency ranges and whole vehicle acoustic calculation conditions, and performing correlation matching with modal super units such as chassis and TB; adopting a modal super unit reduction algorithm and combining boundary conditions, freedom constraints, modal frequency ranges and whole vehicle acoustic calculation conditions to obtain whole vehicle calculation results and vibration curves; comparing and analyzing the whole vehicle calculation results with the vibration curves and conventional results; extracting the peak values ​​and frequencies corresponding to the whole vehicle noise and vibration curves according to the whole vehicle calculation results and vibration curves; adopting the above scheme, the present invention has the advantages of high calculation and analysis efficiency, small space occupation, high result accuracy, simple and reliable logic, etc., and has high practical value and promotion value in the field of whole vehicle NVH technology.

Description

Technical Field

[0001] The present invention relates to the field of whole vehicle NVH technology, and in particular to a whole vehicle NVH calculation method based on a modal super unit. Background Art

[0002] NVH (Noise, Vibration, Harshness) is a comprehensive issue to measure the quality of automobile manufacturing, which gives the most direct experience to automobile users. Statistics show that about 1 / 3 of the failure problems of the whole vehicle are related to the NVH problem of the car, and nearly 20% of the research and development expenses of major automobile companies are spent on solving the NVH problem of the car.

[0003] For vehicle-level NVH analysis, there are often millions of nodes and units in the vehicle. Under the premise of relatively scarce computing resources and short project schedules, how to quickly and efficiently perform vehicle NVH analysis and propose more solutions in a limited time, and sometimes it is particularly important to use super-unit methods.

[0004] At present, the existing technology of vehicle NVH analysis has the following problems:

[0005] The existing technology mainly uses conventional analysis models or frequency response function super-unit methods to solve the whole vehicle NVH simulation. The frequency response function super-unit is mainly a method to calculate the whole vehicle NVH based on the frequency response function of the attachment point. The creation time of the super-unit calculation model is relatively long, especially when there are many attachment points, the transfer function will be very large, that is, the result file will be very large. And because the frequency response function method is used, it contains the complete matrix of the transfer function between the nearby points and the interface, and generally only supports direct method solution. And because the whole vehicle NVH model often includes millions of units, the calculation time is long, sometimes one calculation takes a day of calculation time, and only limited solution calculations and optimizations can be performed in a limited time, which is difficult to meet the project node and performance development requirements, and it will also consume a lot of manpower and material resources.

[0006] Therefore, in order to solve the problems of vehicle NVH simulation efficiency and shorten calculation time, it is urgent to propose a vehicle NVH calculation method based on modal super units with high calculation efficiency, low time consumption, reliable logic and high result accuracy. Summary of the invention

[0007] The purpose of the present invention is to provide a whole vehicle NVH calculation method based on modal super units to solve the problems raised in the above background technology.

[0008] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0009] The whole vehicle NVH calculation method based on the modal super unit is characterized by comprising the following steps:

[0010] Construct a whole vehicle model and divide the whole vehicle model into a TB model and a chassis model, shrink the TB model and the chassis model into super units respectively, and connect each modal super unit;

[0011] Collect and obtain boundary conditions, connection point freedom constraints, modal frequency range and vehicle acoustic calculation conditions, and associate and match them with chassis and TB modal super units;

[0012] The modal super-element reduction algorithm is used in combination with boundary conditions, degree of freedom constraints, modal frequency range and vehicle acoustic calculation conditions to obtain the vehicle calculation results and vibration curves.

[0013] The vehicle calculation results, vibration curves and conventional results were compared and analyzed, and it was concluded that the accuracy of the modal super unit calculation results met the vehicle calculation requirements;

[0014] According to the calculation results and vibration curve of the whole vehicle, the peak values ​​and frequencies corresponding to the noise and vibration curve of the whole vehicle are extracted.

[0015] Preferably, the boundary conditions include structural connection points and acoustic response points.

[0016] Preferably, the modal synthesis super-element method is derived through a static super-element, which is based on an accurate dynamic condensation transformation matrix to obtain a high-precision system dynamics equation and super-element results.

[0017] The general system statics equation is expressed as:

[0018] [K]{U}={F} (1)

[0019] Among them, K represents the super unit mass matrix, F represents the external load vector of the super unit, and U represents the displacement vector.

[0020] Decomposing the formula (1) into a set of two degrees of freedom, namely, the boundary degree of freedom and the internal degree of freedom, its expression is:

[0021]

[0022] Among them, the subscripts M and S correspond to the master degree of freedom node and the slave degree of freedom node respectively.

[0023] In the model calculation, the nodes that need to be connected are generally selected as the main degree of freedom nodes, and the rest of the whole is used as the slave degree of freedom nodes. Decomposing formula (2), we can get:

[0024] K UM U M + KM SU S =F M (3)

[0025] K SM U M +K SS U S =F S (4)

[0026] From formula (4), we can get:

[0027]

[0028] Substituting formula (5) into formula (2), we can get:

[0029]

[0030] in, is the stiffness matrix of the superelement; is the loading matrix of the superelement.

[0031] Formula (1) to Formula (6) are the processing process of super units in statics. It can be seen that the main degrees of freedom of the sub-model become the node degrees of freedom at the required connection points; while the subordinate degrees of freedom of the sub-model become nodeless or additional degrees of freedom, so they can be deleted in the design calculation and do not participate in the calculation.

[0032] On the basis of the static super-element, without considering the system damping, the super-element dynamic equation of the modal super-element model is constructed, and its expression is:

[0033]

[0034] Among them, M and K represent the mass matrix and stiffness matrix of the super unit respectively, and F represents the external load vector of the super unit. represents the acceleration vector, and U represents the displacement vector. According to the analysis purpose, the original system is divided into several subsystems along the interface, which is the super unit. At this time, the super unit degree of freedom set consists of the boundary node degree of freedom set on the interface and the super unit internal node degree of freedom set, so the mass matrix M of the super unit is ff and the stiffness matrix K ff It can be expressed as:

[0035]

[0036] The formula (1) is expanded with internal and external degrees of freedom, and its expression is:

[0037]

[0038] Among them, F m and F s represents the superelement interface bonding force corresponding to the master degree of freedom node and the slave degree of freedom node, M mmand K mm Respectively represent the mass matrix and stiffness matrix of the internal nodes; M ms and M sm They represent the coupled mass matrices, which are mutually symmetric; M ss and K ss They represent the mass matrix and stiffness matrix of the boundary nodes respectively; K ms and K sm They represent the coupled stiffness matrices respectively, which are symmetric to each other; represents the internal node acceleration vector, represents the boundary node acceleration vector; U m represents the internal node displacement vector, U s Represents the boundary node displacement vector.

[0039] The calculation of the fixed interface modal of a component is to construct the modal matrix of the component based on the fixed interface modal and the constraint modal, that is, the main mode of the component substructure system under the displacement condition on the completely fixed boundary surface. mm} can be calculated by solving the following equation (3)

[0040]

[0041] Where ω r ,φ mm are the eigenvalues ​​and eigenvectors under fixed superelement boundary conditions.

[0042] The motion equation of the super-element in the modal coordinate {p} is established, and its expression is:

[0043] {F}=[M]{P}+[K]{P} (10)

[0044] in γm represents the modal coordinate vector.

[0045] After obtaining the reduced modal equation of the component, the displacement coordination conditions and force balance conditions of the component substructure are used to perform component modal synthesis to obtain the motion equation of the entire structural system, and then the natural frequencies and modes of each order of the entire structural system are calculated. The modal superposition method is then used to solve the dynamic characteristics of the system, and the various solution parameters of the system can be obtained at the same time.

[0046] The equation of motion after super-element reduction is obtained, and its expression is:

[0047]

[0048] in, represents the reduced mass matrix, represents the reduced system acceleration vector, represents the reduced stiffness matrix, p represents the reduced system displacement vector, Represents the reduced resultant force.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] (1) Compared with the traditional frequency response function-based superunit calculation method, the modal superunit calculation method of the present invention has the following advantages: it is based on the modal method, including structural modes and acoustic cavity modes, and by establishing a modal superunit model, it reduces the number and time of repeated calculations of the finite element submodule model in the simulation analysis. In addition, since the creation time of the superunit calculation model is generally short, the calculation time of the modal solution is also relatively short. At the same time, the calculation results of the modal superunit can be obtained by the modal method and the direct method, which greatly reduces the time required for calculation and increases the calculation efficiency. In addition, the modal information obtained by the solution is very rich, such as the stiffness, mass, damping, etc. of the modal space. These modal parameters can be used to understand the characteristics and influence of each mode, which provides great help for the calculation and analysis of the NVH of the whole vehicle.

[0051] (2) The present invention uses modal parameter information to perform whole vehicle calculations, cleverly collects and obtains boundary conditions, degree of freedom constraints, modal frequency ranges and whole vehicle acoustic calculation conditions, and realizes the transmission of forces and torques through the connection between each modal super unit, which greatly improves the efficiency of analysis, calculation and optimization. For a whole vehicle model reaching a million level, the calculation and analysis time is shortened from nearly 4 hours to about 30 minutes. The improvement effect is very obvious, and the calculation accuracy is high, which is consistent with the original calculation and analysis results, and the calculation results occupy little storage space.

[0052] In summary, the present invention has the advantages of high calculation and analysis efficiency, small space occupation, high result accuracy, simple and reliable logic, etc., and has high practical value and promotion value in the field of vehicle NVH technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope of protection. For those skilled in the art, other related drawings can be obtained based on these drawings without creative work.

[0054] Figure 1 It is a structural schematic diagram of the modal super unit model of the present invention.

[0055] Figure 2 Schematic diagram of the boundary definition for the modal superelement TB model.

[0056] Figure 3It is a comparative analysis curve diagram of the calculation results of the present invention.

[0057] Figure 4 It is a logic flow chart of the present invention. DETAILED DESCRIPTION

[0058] In order to make the purpose, technical scheme and advantages of this application clearer, the present invention is further described below in conjunction with the accompanying drawings and embodiments, and the embodiments of the present invention include but are not limited to the following embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0059] Example

[0060] like Figure 1-Figure 4 As shown, this embodiment provides a whole vehicle NVH calculation method based on modal super units, which can greatly shorten the solution time, and the calculation results and accuracy are consistent with conventional methods, which brings great changes and efficiency improvements to the whole vehicle NVH simulation.

[0061] Specifically, the vehicle NVH calculation method based on the frequency function super unit of this embodiment includes the following steps:

[0062] Step 1: construct a whole vehicle model and divide the whole vehicle model into a TB model and a chassis model, shrink the TB model and the chassis model into super units respectively, and connect each modal super unit.

[0063] Step 2: Collect and obtain boundary conditions, connection point freedom constraints, modal frequency range and vehicle acoustic calculation conditions, and associate and match them with modal super units such as chassis and TB.

[0064] Step 3: Use the modal superelement reduction algorithm and combine the boundary conditions, degree of freedom constraints, modal frequency range and vehicle acoustic calculation conditions to obtain the vehicle calculation results and vibration curves.

[0065] Step 4: Compare and analyze the calculation results of the whole vehicle with the vibration curve and conventional results to obtain that the accuracy of the modal super unit calculation results meets the calculation requirements of the whole vehicle.

[0066] Step 5: According to the calculation results and vibration curve of the whole vehicle, the peak values ​​and frequencies corresponding to the noise and vibration curve of the whole vehicle are extracted.

[0067] In this embodiment, as follows:

[0068] The modal synthesis super-element method is derived through the static super-element. It is based on the accurate dynamic condensation transformation matrix to obtain high-precision system dynamics equations and super-element results.

[0069] The general system statics equation is expressed as:

[0070] [K]{U}={F} (1)

[0071] Among them, K represents the super unit mass matrix, F represents the external load vector of the super unit, and U represents the displacement vector.

[0072] Decomposing the formula (1) into a set of two degrees of freedom, namely, the boundary degree of freedom and the internal degree of freedom, its expression is:

[0073]

[0074] Among them, the subscripts M and S correspond to the master degree of freedom node and the slave degree of freedom node respectively.

[0075] In the model calculation, the nodes that need to be connected are generally selected as the main degree of freedom nodes, and the rest of the whole is used as the slave degree of freedom nodes. Decomposing formula (2), we can get:

[0076] K UM U M +K MS U S =F M (3)

[0077] K SM U M +K SS U S =F S (4)

[0078] From formula (4), we can get:

[0079]

[0080] Substituting formula (5) into formula (2), we can obtain:

[0081]

[0082] in, is the stiffness matrix of the superelement; is the loading matrix of the superelement.

[0083] Formula (1) to Formula (6) are the processing process of super units in statics. It can be seen that the main degrees of freedom of the sub-model become the node degrees of freedom at the required connection points; while the subordinate degrees of freedom of the sub-model become nodeless or additional degrees of freedom, so they can be deleted in the design calculation and do not participate in the calculation.

[0084] On the basis of the static super-element, without considering the system damping, the super-element dynamic equation of the modal super-element model is constructed, and its expression is:

[0085]

[0086] Among them, M and K represent the mass matrix and stiffness matrix of the super unit respectively, and F represents the external load vector of the super unit. represents the acceleration vector, and U represents the displacement vector. According to the analysis purpose, the original system is divided into several subsystems along the interface, which is the super unit. At this time, the super unit degree of freedom set consists of the boundary node degree of freedom set on the interface and the super unit internal node degree of freedom set, so the mass matrix M of the super unit is ff and the stiffness matrix K ff It can be expressed as:

[0087]

[0088] The formula (1) is expanded with internal and external degrees of freedom, and its expression is:

[0089]

[0090] Among them, F m and F s represents the superelement interface bonding force corresponding to the master degree of freedom node and the slave degree of freedom node, M mm and K mm Respectively represent the mass matrix and stiffness matrix of the internal nodes; M ms and M sm They represent the coupled mass matrices, which are mutually symmetric; M ss and K ss They represent the mass matrix and stiffness matrix of the boundary nodes respectively; K ms and K sm They represent the coupled stiffness matrices respectively, which are symmetric to each other; represents the internal node acceleration vector, represents the boundary node acceleration vector; U m represents the internal node displacement vector, U s Represents the boundary node displacement vector.

[0091] The calculation of the fixed interface modal of a component is to construct the modal matrix of the component based on the fixed interface modal and the constraint modal, that is, the main mode of the component substructure system under the displacement condition on the completely fixed boundary surface. mm} can be calculated by solving the following equation (3)

[0092]

[0093] Where ω r ,φ mm are the eigenvalues ​​and eigenvectors under fixed superelement boundary conditions.

[0094] The motion equation of the super-element in the modal coordinate {p} is established, and its expression is:

[0095] {F}=[M]{P}+[K]{P} (10)

[0096] in γm represents the modal coordinate vector.

[0097] After obtaining the reduced modal equation of the component, the displacement coordination conditions and force balance conditions of the component substructure are used to perform component modal synthesis to obtain the motion equation of the entire structural system, and then the natural frequencies and modes of each order of the entire structural system are calculated. The modal superposition method is then used to solve the dynamic characteristics of the system, and the various solution parameters of the system can be obtained at the same time.

[0098] The equation of motion after super-element reduction is obtained, and its expression is:

[0099]

[0100] in, represents the reduced mass matrix, represents the reduced system acceleration vector, represents the reduced stiffness matrix, p represents the reduced system displacement vector, Represents the reduced resultant force.

[0101] This embodiment reduces the number and time of repeated calculations of the finite element sub-module model in the simulation analysis by establishing a modal super-unit model, and realizes the transmission of force and torque through the connection between each modal super-unit, which greatly improves the analysis calculation and optimization efficiency. The calculation and analysis time is shortened from nearly 4 hours to about 30 minutes, and the improvement effect is very obvious. The calculation accuracy is high, which is consistent with the original calculation and analysis results, and the storage space occupied by the calculation results is reduced.

[0102] The following table shows a simplified vehicle model (with 85784 units), which is solved using the modal super unit and frequency response function super unit methods, as well as the vehicle NVH noise response calculation. The comparison results are as follows:

[0103] Table 1 shows the comparison between the time and storage space of the modal super-unit vehicle NVH calculation and analysis and the frequency response function super-unit analysis.

[0104]

[0105]

[0106] It can be seen from the above table that for a complex vehicle model, if the number of units is in the millions, the advantage of using modal superunits is very obvious. For example, the number of units in a vehicle is 3,298,683. By using modal superunits, the calculation time of vehicle noise under 50 km / h road noise conditions is shortened from nearly 4 hours to about 30 minutes, and the effect is very obvious.

[0107] The above embodiments are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any changes that adopt the design principles of the present invention and are made through non-creative work on this basis should fall within the protection scope of the present invention.

Claims

1. The whole vehicle NVH calculation method based on modal super unit is characterized by: The following steps are involved: Construct a whole vehicle model and divide the whole vehicle model into a TB model and a chassis model, shrink the TB model and the chassis model into super units respectively, and connect each modal super unit; Collect and obtain boundary conditions, connection point freedom constraints, modal frequency range and vehicle acoustic calculation conditions, and associate and match them with chassis and TB modal super units; The modal super-element reduction algorithm is used in combination with boundary conditions, degree of freedom constraints, modal frequency range and vehicle acoustic calculation conditions to obtain the vehicle calculation results and vibration curves. The vehicle calculation results, vibration curves and conventional results were compared and analyzed, and it was concluded that the accuracy of the modal super unit calculation results met the vehicle calculation requirements; According to the calculation results and vibration curve of the whole vehicle, the peak value and frequency corresponding to the noise and vibration curve of the whole vehicle are extracted; The modal synthesis super-element method is derived through the static super-element, which is based on the accurate dynamic condensation transformation matrix to obtain high-precision system dynamics equations and super-element results. The static equation of the system is expressed as: （1） Where K represents the superelement mass matrix, represents the external load vector acting on the superelement, represents the displacement vector; Formula (1) is decomposed into a set of two degrees of freedom, namely, boundary degrees of freedom and internal degrees of freedom, and its expression is: （2） Among them, the subscripts M and S correspond to the master degree of freedom node and the slave degree of freedom node, respectively; In the model calculation, the nodes that need to be connected are selected as the master degree of freedom nodes, and the rest of the whole is used as the slave degree of freedom nodes. Formula (2) is decomposed to obtain: （3） （4） From formula (4), we can get: （5） Substituting formula (5) into formula (2), we can obtain: （6） in, is the stiffness matrix of the superelement; is the load matrix of the superelement, Equations (1) to (6) are the processing of super-elements in statics. The master degrees of freedom of the sub-model become the node degrees of freedom at the points where connections are required, while the slave degrees of freedom of the sub-model become nodeless or additional degrees of freedom. On the basis of the static super-element, without considering the system damping, the super-element dynamic equation of the modal super-element model is constructed, and its expression is: （7） Among them, M and K represent the super unit mass matrix and stiffness matrix respectively. represents the external load vector acting on the superelement, represents the acceleration vector, Represents the displacement vector. According to the analysis purpose, the original system is divided into several subsystems along the interface, namely the super unit. The super unit degree of freedom set consists of the boundary node degree of freedom set on the interface and the super unit internal node degree of freedom set, so the mass matrix of the super unit is and the stiffness matrix It can be expressed as: ； ； Expanding the internal and external degrees of freedom of formula (1), the expression is: (8) in, and represents the superelement interface bonding force corresponding to the master degree of freedom node and the slave degree of freedom node, and denote the mass matrix and stiffness matrix of the internal nodes, respectively. and They represent the coupled mass matrices, which are mutually symmetric matrices. and denote the mass matrix and stiffness matrix of the boundary nodes, respectively. and They represent the coupling stiffness matrices, which are mutually symmetric matrices. represents the internal node acceleration vector, represents the boundary node acceleration vector, represents the internal node displacement vector, represents the boundary node displacement vector; The component fixed interface modal calculation is to construct the component modal matrix based on the component fixed interface mode and constraint mode, that is, the main mode of the component substructure system under the displacement condition on the completely fixed boundary surface, the fixed boundary mode It can be calculated by solving the following equation (3) （9） In the formula , are the eigenvalues ​​and eigenvectors under the fixed conditions of the super unit boundary; Create superelement in modal coordinates The equation of motion under is expressed as: （10） in ; ; ; represents the modal coordinate vector; After obtaining the reduced modal equation of the component, the displacement coordination conditions and force balance conditions of the substructure of the component are used to perform component modal synthesis, obtain the motion equation of the entire structural system, calculate the natural frequencies and modes of each order of the entire structural system, and then use the modal superposition method to solve the dynamic characteristics of the system, and at the same time, various solution parameters of the system can be obtained; The equation of motion after super-element reduction is obtained, and its expression is: (11) in, represents the reduced mass matrix, represents the reduced system acceleration vector, represents the reduced stiffness matrix, represents the displacement vector of the system after reduction, Represents the reduced resultant force.

2. The whole vehicle NVH calculation method based on modal super unit according to claim 1 is characterized in that: Boundary conditions include structural connection points and acoustic response points.

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