A method for assigning stiffness of a chassis bushing in a whole vehicle model

Abstract

The present application relates to a kind of chassis bushing stiffness assignment methods in whole vehicle model.The steps are as follows: the test modal of each bar in rear suspension system in free state is obtained by measurement;Simulation model of rear suspension system is established;According to the preset bushing each direction stiffness value range, simulation model is processed, obtain a plurality of simulation models of different stiffness values, and modal solution is carried out to obtain the simulation modal of each bar in rear suspension system;Mathematical model between the simulation modal of each bar in rear suspension system and the bushing each direction stiffness value is established;According to test modal, the test modal of each bar in rear suspension system in preset frequency range is obtained, and less than or equal to preset number of test modal is selected;According to selected test modal and mathematical model, the target value of bushing each direction stiffness is solved;With the target value of bushing each direction stiffness as the chassis bushing stiffness assignment in whole vehicle NVH model.The present application optimizes the stiffness value of bushing, thereby improves the precision of whole vehicle MVH model.

Description

Technical Field

[0001] This invention relates to the field of automotive NVH technology, specifically to a method for assigning stiffness values ​​to chassis bushings in a complete vehicle model. Background Technology

[0002] Rubber bushings have excellent vibration damping and noise reduction functions and are widely used in automotive suspension systems. In the rear suspension system, the toe-adjusting rod, lower control arm, and upper control arm are all connected to the rear subframe through rubber bushings. As the flexible boundary of the rear suspension system, the rubber bushing affects the mode of the suspension system, and the mode of the rear suspension system has a significant impact on the overall NVH performance of the vehicle. Therefore, how to accurately simulate the flexible boundary in modeling is an urgent problem to be solved.

[0003] Traditional simulation methods simplify the bushings in the vehicle NVH model as linear elastic constraints and assign static stiffness values ​​in six directions. However, bushing stiffness varies non-linearly with frequency. Therefore, traditional simulation methods cannot accurately simulate this flexible boundary, resulting in inaccurate acquisition of the rear suspension system's modal characteristics under such conditions. Furthermore, in certain frequency bands, the suspension exhibits not the overall modal characteristics, but rather the modal characteristics of the individual links that make up the suspension system. The influence of bushing stiffness on the modal characteristics of these individual links is significant. CN104731991A discloses a bushing modeling method, comprising: dividing each part of a predefined bushing 3D model into finite element meshes; determining the material properties of the finite element meshes for each part of the bushing 3D model, wherein the material properties are the density, Poisson's ratio, and elastic modulus of the material selected for each part of the bushing; performing calculations on the finite element meshes according to the order, operation method, and load step of the predefined output modes of the bushing flexible body to obtain the frequencies and mode shapes of each mode of the bushing flexible body, as well as the bushing flexible body animation file; converting the bushing flexible body animation file into a modal neutral file and importing it into flexible body motion simulation software to establish a bushing flexible body model. This method is mainly used in the dynamic analysis model of a whole vehicle, mainly solving the coupling problem of bushing stiffness in all directions, but it cannot be applied to the NVH model of a whole vehicle. Summary of the Invention

[0004] The purpose of this invention is to provide a method for assigning chassis bushing stiffness values ​​in a vehicle model, so as to optimize the bushing stiffness values, thereby accurately determining the mode of the rear suspension system under flexible boundaries, and thus improving the accuracy of the vehicle MVH model.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for assigning stiffness values ​​to chassis bushings in a vehicle model includes the following steps:

[0007] S1. The test modes of each link in the rear suspension system in the free state are obtained by measurement;

[0008] S2. Establish a simulation model of the rear suspension system, in which the CBUSH element is used to simulate the bushing;

[0009] S3. Based on the preset range of stiffness values ​​for each direction of the bushing, the simulation model is processed to obtain multiple simulation models with different stiffness values.

[0010] S4. Perform modal analysis on simulation models with different stiffness values ​​to obtain the simulation modes of each link in the rear suspension system;

[0011] S5. Establish a mathematical model between the simulation modes of each link in the rear suspension system and the stiffness values ​​of the bushing in each direction;

[0012] S6. Based on the test modes, obtain the test modes of each link in the rear suspension system within a preset frequency range, and select a preset number of test modes within the preset frequency range that are less than or equal to the preset number.

[0013] S7. Based on the selected test modes and mathematical models, solve for the target values ​​of the bushing stiffness in each direction;

[0014] S8, the target value of the obtained bushing stiffness in each direction is assigned as the chassis bushing stiffness value in the whole vehicle NVH model.

[0015] Preferably, step S6 specifically includes: obtaining the test modes of each link in the rear suspension system within a preset frequency range based on the test modes, and selecting less than or equal to a preset number of test modes within the preset frequency range; dividing important modes and general modes from the selected test modes within the preset frequency range based on the mode shape and mode amplitude, with the following principles: 1) Mode shape importance is greater than mode amplitude; 2) Mode shape: In the vehicle coordinate system, the Z-direction mode is more important than the Y-direction mode, and the Y-direction mode is more important than the X-direction mode; 3) Mode amplitude: In the vehicle coordinate system, the larger the amplitude, the more important it is; among them, important modes are divided into 1 to 2 orders, and general modes are divided into 2 to 4 orders.

[0016] In general, there are multiple test modes within the preset frequency band. When selecting test modes, it is generally necessary to select complete and comprehensive test modes. Therefore, the number selected is generally less than or equal to 6, that is, the preset number value in S6 is 6.

[0017] Preferably, step S7 specifically includes:

[0018] S71. Solve for the stiffness values ​​of the bushing in each direction according to the important modes and the mathematical model to obtain the initial values ​​of the bushing stiffness in each direction under the important modes; obtain the sensitivity of the bushing stiffness in each direction under the important modes according to the initial values ​​of the bushing stiffness in each direction and the frequency change under the important modes; obtain the corresponding number of sensitivity values ​​to be obtained according to the number of test modes selected in the preset frequency range, and obtain the initial value of the bushing stiffness in the corresponding direction according to the number of sensitivity values ​​to be obtained, and use the initial value of the bushing stiffness as the target value of the bushing stiffness in that direction.

[0019] S72. Substitute the target value of the bushing stiffness in this direction into the mathematical model to obtain an updated mathematical model.

[0020] S73. Solve for the stiffness value of the bushing in the remaining direction based on the general mode and the updated mathematical model to obtain the target value of the stiffness of the bushing in the remaining direction.

[0021] Preferably, in step S6, a preset number of test modes, including three-order modes, are selected within a preset frequency band. These modes are designated as α1, α2, and α3, respectively. Based on the mode shape and mode amplitude, α1 is classified as an important mode, while α2 and α3 are classified as general modes.

[0022] Preferably, step S71 specifically includes: solving for the stiffness values ​​of the bushing in each direction based on the important mode α1 and the mathematical model to obtain the initial values ​​of the bushing stiffness in each direction under the important mode; selecting a target frequency within the frequency range of the important mode α1, and taking the change in stiffness of the bushing in each direction when the change in the target frequency is 1Hz as the sensitivity of the bushing stiffness in each direction; setting the number of test modes selected in the preset frequency range as n, and setting the number of corresponding sensitivities to be selected as m1, where m1 is the smallest integer greater than or equal to 6 / n; sorting the sensitivity of the bushing stiffness in each direction from smallest to largest, obtaining the initial values ​​of the bushing stiffness in the direction corresponding to the first m1 sensitivity values, and using these initial values ​​of the bushing stiffness as the target value of the bushing stiffness in that direction.

[0023] Preferably, step S73 specifically includes: solving for the stiffness value of the bushing in the remaining direction based on the general mode α2 and the updated mathematical model to obtain the initial value of the bushing stiffness in the remaining direction under the general mode α2; selecting a target frequency within the frequency band of the general mode, and taking the change in the bushing stiffness in the remaining direction when the change in the target frequency is 1Hz as the sensitivity of the bushing stiffness in the remaining direction; setting the number of test modes selected within the preset frequency band as n, and setting the number of corresponding sensitivities to be selected as m2, where m2 is the largest integer less than or equal to 6 / n; sorting the sensitivity of the bushing stiffness in the remaining direction from smallest to largest, obtaining the initial value of the bushing stiffness in the direction corresponding to the first m2 sensitivity values, using this initial value of the bushing stiffness as the target value of the bushing stiffness in that direction, and substituting the target value of the bushing stiffness in that direction into the updated mathematical model to obtain a further updated mathematical model;

[0024] The stiffness value of the bushing in the remaining direction is solved based on the general mode α3 and the updated mathematical model to obtain the initial value of the bushing stiffness in the remaining direction under the general mode α3, and this initial value of the bushing stiffness is used as the target value of the bushing stiffness in that direction.

[0025] Preferably, in step S2, Hypermesh software is used to establish a simulation model of the rear suspension system.

[0026] Preferably, in S3, the stiffness values ​​of the bushing in each direction include the stiffness values ​​of the bushing in six directions, namely the translational directions of the bushing along the X-axis, Y-axis, and Z-axis, and the rotational directions of the bushing around the X-axis, Y-axis, and Z-axis.

[0027] The simulation model was processed using the Latin hypercube sampling method.

[0028] By using the Latin hypercube sampling method to process the simulation model, the number of experimental processing steps is effectively reduced while ensuring accuracy.

[0029] Preferably, in step S4, Nastran is used to perform modal analysis on simulation models with different stiffness values.

[0030] Preferably, in S1, the links in the rear suspension system include the front lower control arm, the rear trailing arm, the rear toe-adjusting rod, the rear lower control arm, and the rear upper control arm.

[0031] Preferably, in step S1, the measured frequency range is between 100Hz and 500Hz.

[0032] The beneficial effects of this invention are:

[0033] The method for assigning stiffness values ​​to chassis bushings in a vehicle model according to the present invention simulates the bushings using CBUSH elements in the simulation model and establishes a mathematical model between the simulation modes and the stiffness values ​​of the bushings in each direction. Simultaneously, a preset number of test modes are selected from the test modes. By jointly solving the test modes and the mathematical model, the target values ​​of the bushing stiffness in each direction are obtained. These target values ​​are then used as the stiffness values ​​of the chassis bushings in the vehicle NVH model, effectively ensuring the accuracy of the bushing stiffness values. This allows for accurate determination of the suspension system's modes under flexible boundaries, effectively improving the accuracy of the vehicle NVH model. Furthermore, it has the advantages of simple operation and high accuracy, and has significant application value in the field of automotive NVH technology. Attached Figure Description

[0034] Figure 1 This is a flowchart of the method for assigning stiffness values ​​to chassis bushings in the vehicle model of the present invention. Detailed Implementation

[0035] The embodiments of the present invention will be described below with reference to the accompanying drawings and preferred embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are only for illustrating the present invention and not for limiting the scope of protection of the present invention.

[0036] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0037] Example 1

[0038] like Figure 1 As shown, a method for assigning values ​​to the stiffness of chassis bushings in a vehicle model includes the following steps:

[0039] S1. Modal testing: The test modes of each link in the rear suspension system under flexible boundary conditions are obtained by force hammer testing. The measurement state is as follows: the rear suspension system and the rear subframe are connected. In the free state, the measurement frequency range is 100Hz to 500Hz. The links in the rear suspension system include the front lower control arm, the rear trailing arm, the rear toe adjustment rod, the rear lower control arm, and the rear upper control arm.

[0040] S2. Establish simulation model: Establish a simulation model of the rear suspension system identical to that used in the modal test using Hypermesh software, in which the CBUSH unit is used to simulate the bushing;

[0041] S3. Simulation Model Processing: Preset the stiffness value ranges for the bushing in six directions. These six directions include the translational directions along the X, Y, and Z axes, and the rotational directions around the X, Y, and Z axes. The stiffness value ranges for each of the six directions are Δ... X Δ Y Δ Z Δ RX Δ RY and Δ RZ In this embodiment, Δ X Δ Y Δ Z Δ RX Δ RY and Δ RZ The values ​​range from 5000 N / mm to 30000 N / mm;

[0042] To reduce the number of experiments while ensuring accuracy, the Latin hypercube sampling method is used to process the simulation model, resulting in multiple simulation models with different stiffness values. In this embodiment, approximately 300 processing steps are performed.

[0043] S4. Modal solution: Based on Nastran, modal solution is performed on simulation models with different stiffness values ​​to obtain the simulation modes of each link in the rear suspension system;

[0044] S5. Establish a mathematical model: Build a mathematical model between the simulation modes of each link in the rear suspension system and the stiffness values ​​of the connected bushings in six directions using a neural network.

[0045] S6. Select test modes and classify important modes and general modes: Based on the test modes in S1, obtain the test modes of each link in the rear suspension system within the preset frequency range, select 3 test modes within the preset frequency range, and classify important modes and general modes from the 3 test modes selected within the preset frequency range according to the mode shape and mode amplitude.

[0046] In this embodiment, the preset frequency range is 100Hz to 500Hz. The three test modes selected within the preset frequency range include three-order modes, namely α1, α2 and α3. According to the mode shape and mode amplitude screening rules, α1 is divided into important modes, and α2 and α3 are general modes. Among them, α1 = 260Hz, α2 = 353Hz, and α3 = 450Hz.

[0047] The principles for distinguishing important modes from general modes within the preset frequency range are as follows: 1) Mode shape importance is greater than mode amplitude; 2) Mode shape: In the vehicle coordinate system, the Z-axis mode is more important than the Y-axis mode, and the Y-axis mode is more important than the X-axis mode; 3) Mode amplitude: In the vehicle coordinate system, the larger the amplitude, the more important it is; among them, important modes are divided into 1-2 orders, and general modes are divided into 2-4 orders.

[0048] S7. Based on the selected test modes and mathematical model, solve for the target values ​​of the bushing stiffness in each direction, specifically including:

[0049] S71. Solve for the stiffness values ​​of the bushing in the following directions based on the important modes and mathematical models: solve for the stiffness values ​​of the bushing in the six directions based on the important modes α1 and S6 mathematical models, and obtain the initial values ​​of the stiffness of the bushing in the six directions under the important mode α1 = 260Hz.

[0050] Based on the initial values ​​of the bushing stiffness in six directions, with 260Hz as the target frequency, the stiffness in five directions is kept constant, while the stiffness in one direction is changed. When the target frequency change is 1Hz, the change in bushing stiffness in one direction is the sensitivity of the bushing stiffness in that direction. This process is repeated to obtain the sensitivities of the bushing stiffness in each direction at the important mode α1 = 260Hz, β... X1 (Sensitivity of the bushing's stiffness during translation along the X-axis), β Y1 (Sensitivity of the bushing's stiffness during translation along the Y-axis), β Z1 (Sensitivity of the bushing's stiffness during Z-axis translation), β RX1 (Sensitivity of the bushing's stiffness when rotating about the X-axis), β RY1 (Sensitivity of the bushing's stiffness when rotating about the Y-axis) and β RZ1 (Sensitivity of the stiffness of the bushing rotating along the Z-axis), where β X1 =732N / mm, β Y1 =1201 N / mm, β Z1 =846 N / mm,

[0051] β RX1 =3310 N / mm, β RY1 =2455 N / mm, β RZ1 =4361 N / mm, the sensitivity is sorted from smallest to largest, and the result is: β X1 β Z1 β Y1 β RY1 β RX1 and β RZ1 ;

[0052] In this embodiment, the number of modes n selected in the preset frequency band is 3, and the number of sensitivity values ​​to be selected m1 is the smallest integer greater than or equal to 6 / n, so the number of sensitivity values ​​to be selected is 2. Based on the sorted sensitivity, the initial value of the bushing stiffness in the direction corresponding to the first 2 sensitivity values ​​is obtained, that is, the initial value of the bushing stiffness in the translational direction along the X-axis and Z-axis is the target value of the bushing stiffness in the translational direction along the X-axis and Z-axis.

[0053] S72. Substitute the target values ​​of stiffness along the translational directions of the X and Z axes into the mathematical model of S5 to obtain an updated mathematical model.

[0054] S73. Based on the general mode and the updated mathematical model, solve for the stiffness values ​​in the remaining directions of the bushing, including:

[0055] S731. Solve for the stiffness value of the bushing in the residual direction according to the general mode α2 and the updated mathematical model in S71 to obtain the initial value of the stiffness of the bushing in the residual direction under the general mode α2, that is, the initial value of the stiffness of the bushing in the translational direction along the Y-axis, and the initial value of the stiffness of the bushing in the rotation around the X-axis, Y-axis and Z-axis.

[0056] Based on the initial values ​​of the bushing stiffness in four directions, with 353Hz as the target frequency, keeping the stiffness constant in three directions, and changing the stiffness in one direction, the change in bushing stiffness in one direction when the target frequency change is 1Hz is the sensitivity of the bushing stiffness in that direction. This process is repeated to obtain the sensitivities of the bushing stiffness in each direction under the general mode α2 = 353Hz, β... Y2 (Sensitivity of the bushing's stiffness during translation along the Y-axis), β RX2 (Sensitivity of the bushing's stiffness when rotating about the X-axis), β RY2 (Sensitivity of the bushing's stiffness when rotating about the Y-axis) and β RZ2 (Sensitivity of the stiffness of the bushing rotating along the Z-axis), where β Y2 =1511 N / mm, β RX2 =4776 N / mm, β RY2 =5235 N / mm, β RZ2 =3215 N / mm, the sensitivity is sorted from smallest to largest, and the result is: β Y2 β RZ2 β RX2 and β RY2 ;

[0057] In this embodiment, the number of modes n selected within the preset frequency band is 3, and the number of sensitivities to be selected m2 is the largest integer less than or equal to 6 / n, so the number of sensitivities to be selected is 2. Based on the sorted sensitivities, the initial values ​​of the bushing stiffness in the directions corresponding to the first two sensitivity values ​​are obtained, that is, the initial values ​​of the bushing stiffness in the translational direction along the Y-axis and the rotational direction around the Z-axis, which are the target values ​​of the bushing stiffness in the translational direction along the Y-axis and the rotational direction around the Z-axis.

[0058] S732. Substitute the target values ​​of stiffness in the direction of translation along the Y-axis and rotation around the Z-axis into the mathematical model updated in S72 to obtain the updated mathematical model again.

[0059] S733. Solve for the stiffness value of the bushing in the remaining direction according to the general mode α3 and the updated mathematical model to obtain the initial value of the stiffness of the bushing in the remaining direction under the general mode α3, that is, the initial value of the stiffness of the bushing rotating about the X-axis and Y-axis.

[0060] Based on the initial values ​​of the bushing stiffness in two directions, with 450Hz as the target frequency, keeping the stiffness in one direction constant and changing the stiffness in the other direction, the change in bushing stiffness in the other direction when the target frequency changes by 1Hz is the sensitivity of the bushing stiffness in that direction. This process is repeated to obtain the sensitivities of the bushing stiffness in each direction under the general mode α3, denoted as β. RX3 (Sensitivity of the bushing's stiffness when rotating about the X-axis) and β RY3 (Sensitivity of the stiffness of the bushing rotating about the Y-axis), where β RX3 =2379 N / mm, β RY3 =3610 N / mm, the sensitivity is sorted from smallest to largest, and the result is: β RX3 and β RY3 ;

[0061] In this embodiment, the number of modes n in the preset frequency band is 3, and the number of sensitivity values ​​to be selected m3 is less than or equal to the largest integer of 6 / n, so the number of sensitivity values ​​to be selected is 2. Based on the sorted sensitivity, the initial values ​​of the bushing stiffness in the direction corresponding to the first 2 sensitivity values ​​are obtained, that is, the initial values ​​of the stiffness of the bushing in the rotation direction around the X-axis and Y-axis, which are the target values ​​of the stiffness of the bushing in the rotation direction around the X-axis and Y-axis.

[0062] Thus, the target values ​​of the bushing stiffness in six directions are finally obtained;

[0063] S8. Determine the stiffness value of the chassis bushing in the whole vehicle NVH model: The target value of the stiffness of the obtained bushing in each direction is assigned as the stiffness value of the chassis bushing in the whole vehicle NVH model.

[0064] In summary, the method for assigning chassis bushing stiffness in the whole vehicle model of the present invention simulates the bushing using CBUSH elements in the simulation model and establishes a mathematical model between the simulation modes and the stiffness values ​​of the bushing in each direction. At the same time, important modes and general modes are selected from the test modes and solved together with the mathematical model to obtain the target values ​​of the bushing stiffness in each direction. These target values ​​are then used as the assigned values ​​of chassis bushing stiffness in the whole vehicle NVH model, thereby accurately obtaining the modes of the suspension system under flexible boundaries. This effectively improves the accuracy of the whole vehicle NVH model and has the advantages of simple operation and high accuracy. It has promotional application value in the field of automotive NVH technology.

[0065] The above embodiments are merely preferred embodiments provided to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention.

Claims

1. A method for assigning stiffness values ​​to chassis bushings in a complete vehicle model, characterized in that, Includes the following steps: S1. The test modes of each link in the rear suspension system in the free state are obtained by measurement; S2. Establish a simulation model of the rear suspension system, in which the CBUSH element is used to simulate the bushing; S3. Based on the preset range of stiffness values ​​for each direction of the bushing, the simulation model is processed to obtain multiple simulation models with different stiffness values. S4. Perform modal analysis on simulation models with different stiffness values ​​to obtain the simulation modes of each link in the rear suspension system; S5. Establish a mathematical model between the simulation modes of each link in the rear suspension system and the stiffness values ​​of the bushing in each direction; S6. Based on the test modes, obtain the test modes of each link in the rear suspension system within a preset frequency range, and select less than or equal to a preset number of test modes within the preset frequency range; specifically including: based on the test modes, obtain the test modes of each link in the rear suspension system within a preset frequency range, and select less than or equal to a preset number of test modes within the preset frequency range; based on the mode shape and mode amplitude, distinguish important modes and general modes from the test modes selected within the preset frequency range; S7. Based on the selected test modes and mathematical model, solve for the target values ​​of the bushing stiffness in each direction; specifically including: S71. Solve for the stiffness values ​​of the bushing in each direction according to the important modes and the mathematical model to obtain the initial values ​​of the bushing stiffness in each direction under the important modes; obtain the sensitivity of the bushing stiffness in each direction under the important modes according to the initial values ​​of the bushing stiffness in each direction and the frequency change under the important modes; obtain the corresponding number of sensitivity values ​​to be obtained according to the number of test modes selected in the preset frequency range, and obtain the initial value of the bushing stiffness in the corresponding direction according to the number of sensitivity values ​​to be obtained, and use the initial value of the bushing stiffness as the target value of the bushing stiffness in that direction. S72. Substitute the target value of the bushing stiffness in this direction into the mathematical model to obtain an updated mathematical model. S73. Solve for the stiffness value of the bushing in the remaining direction based on the general mode and the updated mathematical model to obtain the target value of the stiffness of the bushing in the remaining direction. S8, the target value of the obtained bushing stiffness in each direction is assigned as the chassis bushing stiffness value in the whole vehicle NVH model.

2. The method for assigning stiffness values ​​to chassis bushings in a complete vehicle model according to claim 1, characterized in that, In S6, the principle for dividing important modes and general modes from the test modes selected within the preset frequency band is as follows: 1) The mode shape is more important than the mode amplitude; 2) Mode shape: In the vehicle coordinate system, the Z-direction mode is more important than the Y-direction mode, and the Y-direction mode is more important than the X-direction mode; 3) Mode amplitude: In the vehicle coordinate system, the larger the amplitude, the more important it is; Among them, important modes are divided into 1 to 2 orders, and general modes are divided into 2 to 4 orders.

3. The method for assigning chassis bushing stiffness in a vehicle model according to claim 1, characterized in that, In step S6, a preset number of test modes, including third-order modes, are selected within a preset frequency band, and are respectively set as follows: , and Based on the mode shape and mode amplitude, it is divided into As an important mode, and This is the general mode.

4. The method for assigning stiffness values ​​to chassis bushings in a complete vehicle model according to claim 1, characterized in that, S71 specifically includes: based on important modes The mathematical model is used to solve for the stiffness values ​​of the bushing in each direction, thereby obtaining important modes. Initial values ​​of the stiffness of the lower bushing in all directions; in important modes Select a target frequency within the specified frequency range, and use the change in bushing stiffness in each direction when the target frequency changes by 1 Hz as the sensitivity of bushing stiffness in each direction; set the number of test modes selected within the preset frequency range to be n, and set the number of corresponding sensitivities to be selected to be m1, where m1 is the smallest integer greater than or equal to 6 / n; sort the bushing stiffness sensitivity in each direction from smallest to largest, obtain the initial value of bushing stiffness in the direction corresponding to the first m1 sensitivity values, and use this initial value of bushing stiffness as the target value of bushing stiffness in that direction.

5. The method for assigning chassis bushing stiffness in a complete vehicle model according to claim 4, characterized in that, Specifically, S73 includes: based on the general mode The updated mathematical model is used to solve for the stiffness values ​​in the remaining directions of the bushing, thereby obtaining the general modes. Initial value of the residual directional stiffness of the lower bushing; in the general mode A target frequency is selected within the specified frequency band, and the change in bushing residual directional stiffness when the target frequency changes by 1 Hz is taken as the sensitivity of bushing residual directional stiffness. The number of test modes selected within the preset frequency band is set to n, and the number of corresponding sensitivities to be selected is set to m2, where m2 is the largest integer less than or equal to 6 / n. The sensitivities of bushing residual directional stiffness are sorted from smallest to largest, and the initial values ​​of bushing stiffness in the direction corresponding to the first m2 sensitivity values ​​are obtained. These initial values ​​of bushing stiffness are used as the target value of bushing stiffness in that direction, and the target value of bushing stiffness in that direction is substituted into the updated mathematical model to obtain the updated mathematical model. According to general modes The updated mathematical model is used to solve for the stiffness values ​​of the bushing in the remaining directions, thereby obtaining the general modes. The initial value of the remaining stiffness of the lower bushing is used as the target value of the bushing stiffness in that direction.

6. The method for assigning chassis bushing stiffness in a vehicle model according to claim 1, characterized in that, In S2, Hypermesh software is used to establish a simulation model of the rear suspension system.

7. The method for assigning stiffness values ​​to chassis bushings in a complete vehicle model according to claim 1, characterized in that, In S3, the stiffness values ​​of the bushing in each direction include the stiffness values ​​of the bushing in six directions. The six directions are the translational directions of the bushing along the X-axis, Y-axis, and Z-axis, and the rotational directions of the bushing around the X-axis, Y-axis, and Z-axis. The simulation model was processed using the Latin hypercube sampling method; In S4, Nastran is used to perform modal analysis on simulation models with different stiffness values.

8. The method for assigning stiffness values ​​to chassis bushings in a complete vehicle model according to claim 1, characterized in that, In S1, the links in the rear suspension system include the front lower control arm, the rear trailing arm, the rear toe-adjusting rod, the rear lower control arm, and the rear upper control arm.

9. The method for assigning stiffness values ​​to chassis bushings in a complete vehicle model according to claim 1, characterized in that, In S1, the measured frequency range is between 100Hz and 500Hz.

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