阅读说明：本技术 一种车身振动传递路径分析方法 (Analysis method for vibration transmission path of vehicle body ) 是由 王昆 王玉雷 李雪平 罗德洋 倪晓波 朱平 王增伟 于 2018-07-24 设计创作，主要内容包括：本发明公开一种车身振动传递路径分析方法。所述方法包括：建立传递路径分析模型；在怠速工况下测量工况响应和传递函数；根据测得的工况响应和传递函数,基于结构动力学修改重分析技术预测悬置结构虚拟改变后的工况响应；根据得到的悬置结构虚拟改变后的工况响应,计算悬置结构改变前的悬置刚度；根据悬置刚度计算怠速工况下悬置截面耦合力,进而计算传递路径贡献度。本发明基于结构动力学修改重分析技术预测局部结构虚拟修改后的系统响应,避开了对车身频响函数和悬置动刚度的直接实验测量,提高了传递路径分析的效率,为车身振动传递路径分析奠定了基础。(The invention discloses a method for analyzing a vibration transmission path of a vehicle body. The method comprises the following steps: establishing a transmission path analysis model; measuring working condition response and a transfer function under an idling working condition; predicting the working condition response of the suspension structure after virtual change based on a structural dynamics modification re-analysis technology according to the measured working condition response and the transfer function; calculating the suspension stiffness of the suspension structure before changing according to the obtained working condition response of the suspension structure after virtual change; and calculating the coupling force of the suspension section under the idle working condition according to the suspension rigidity, and further calculating the contribution degree of the transmission path. The method predicts the system response after the virtual modification of the local structure based on the structural dynamics modification re-analysis technology, avoids direct experimental measurement of the frequency response function and the suspension dynamic stiffness of the vehicle body, improves the analysis efficiency of the transmission path, and lays a foundation for the analysis of the vibration transmission path of the vehicle body.)

1. A vehicle body vibration transmission path analysis method is characterized by comprising the following steps:

step 1, establishing a transmission path analysis model by taking an engine as a source, suspensions as a path and a vehicle body as a receiver, wherein the suspensions comprise a left suspension, a right suspension and a rear suspension, and each suspension comprises an engine side mounting point, namely an active end, and a vehicle body side mounting point, namely a passive end;

step 2, measuring working condition response and transfer functions under an idling working condition, wherein the working condition response comprises the acceleration of two ends of each suspension and a vehicle body target point, and the transfer functions comprise exciting force-acceleration transfer functions from one end of each suspension to the other end of each suspension, from one end of each suspension to the vehicle body target point, and from the vehicle body target point to one end of each suspension;

step 3, predicting the virtual changed working condition response of the variable suspension structure based on the structural dynamics modification re-analysis technology according to the working condition response and the transfer function measured in the step 2;

step 4, calculating the suspension stiffness of the suspension structure before changing according to the working condition response of the suspension structure after virtual changing obtained in the step 3;

and 5, calculating the coupling force of the suspension section under the idle working condition according to the suspension rigidity, and further calculating the contribution degree of the transmission path.

2. The method for analyzing the vibration transmission path of the vehicle body according to claim 1, wherein the step 2 specifically includes:

acceleration sensors are arranged at two ends of the suspension and at a target point of a vehicle body to measure working condition response;

the unit force is respectively applied to the local coordinate systems at the two ends of the suspension in three directions, the acceleration of a target point of the vehicle body is measured, and the transfer function from the two ends of the suspension to the target point of the vehicle body is calculated.

3. The method for analyzing the vibration transmission path of the vehicle body according to claim 1, wherein the step 3 specifically includes:

predicting the working condition response of the suspension passive end in elastic connection with the ground along 9 degrees of freedom according to the working condition response and the transfer function measured in the step 2 and formulas (1) to (5)

in the formula (1), X_itIs the i-th degree of freedom operating condition response matrix, H_itFor the ith degree of freedom transfer function matrix, Δ Z_itIs a matrix formed by elastic connection dynamic stiffness when a passive end is grounded or an active end is grounded at the ith degree of freedom,

4. The method for analyzing the vibration transmission path of the vehicle body according to claim 3, wherein the step 4 specifically includes: calculating H according to equation (6)_dK_cAnd H_d,pit：

In the formula (6), the first and second groups,

all H are determined_d,pitAnd is combined with H_d,pitAssembled into H_dAccording to H_dK_cAnd H_dSolving and dismantling dynamic stiffness matrix K of rear suspension of engine_c。

5. The method for analyzing the vibration transmission path of the vehicle body according to claim 4, wherein the step 5 specifically includes:

calculating the coupling force of the suspension section according to the formula (7):

in the formula (7), F_cA suspension section coupling force matrix;

calculating the contribution degree of the transmission path according to a formula (8), namely the contribution component of the coupling force of the suspension section to the acceleration of a target point of the vehicle body:

in equation (8), P represents a transfer path contribution matrix.

Technical Field

The invention belongs to the technical field of automobile manufacturing, and particularly relates to an analysis method for a vibration transmission path of an automobile body based on a structural dynamics re-analysis technology.

Background

Since the "source-path-receiver" model was developed, Transmission Path Analysis (TPA) has been developed as a method of analyzing and addressing the vibration and noise problems of automobiles. The traditional TPA has the advantages of high precision and mature method as the TPA which is proposed at the earliest, but the traditional TPA is time-consuming and labor-consuming because the active part needs to be decoupled. The TPA developed later can shorten the experimental time, but needs to improve the vibration transmission path analysis process of the vehicle body at the expense of the precision, and the TPA based on the inverse substructure method has difficulty in improving.

According to the traditional transfer path analysis method provided by foreign Gert De Sitter et al, a passive component frequency response function is calculated by applying artificial excitation under the working condition operation, the dynamic stiffness of a connecting point is identified, and the effective identification of working condition force can be carried out by combining measured working condition response data, so that the contribution degree of a transfer path is determined. According to the method, the non-coupling frequency response function can be identified through the coupling frequency response function, the system is prevented from being disassembled, however, manual excitation is required to be applied when the system runs under a working condition, the implementation process is complex and difficult, and the efficiency is low.

Disclosure of Invention

In order to solve the problems in the prior art, the invention provides a vehicle body vibration transmission path analysis method based on a structural dynamics modification re-analysis technology.

In order to achieve the purpose, the invention adopts the following technical scheme:

a vehicle body vibration transmission path analysis method includes:

step 1, establishing a transmission path analysis model by taking an engine as a source, suspensions as a path and a vehicle body as a receiver, wherein the suspensions comprise a left suspension, a right suspension and a rear suspension, and each suspension comprises an engine side mounting point, namely an active end, and a vehicle body side mounting point, namely a passive end;

step 2, measuring working condition response and transfer functions under an idling working condition, wherein the working condition response comprises the acceleration of two ends of each suspension and a vehicle body target point, and the transfer functions comprise exciting force-acceleration transfer functions from one end of each suspension to the other end of each suspension, from one end of each suspension to the vehicle body target point, and from the vehicle body target point to one end of each suspension;

step 3, predicting the virtual changed working condition response of the variable suspension structure based on the structural dynamics modification re-analysis technology according to the working condition response and the transfer function measured in the step 2;

step 4, calculating the suspension stiffness of the suspension structure before changing according to the working condition response of the suspension structure after virtual changing obtained in the step 3;

and 5, calculating the coupling force of the suspension section under the idle working condition according to the suspension rigidity, and further calculating the contribution degree of the transmission path.

Compared with the prior art, the invention has the following beneficial effects:

according to the method, a transfer path analysis model is established, working condition response and a transfer function are measured under an idling working condition, the working condition response after the virtual change of the suspension structure is predicted based on a structural dynamics modification reanalysis technology according to the measured working condition response and the transfer function, the suspension rigidity before the change of the suspension structure is calculated according to the obtained working condition response after the virtual change of the suspension structure, the coupling force of the suspension section under the idling working condition is calculated according to the suspension rigidity, and then the contribution degree of the transfer path is calculated, so that the analysis of the vibration transfer path of the vehicle body based on the structural dynamics reanalysis technology is realized. The method predicts the system response after the virtual modification of the local structure based on the structural dynamics modification re-analysis technology, avoids direct experimental measurement of the frequency response function and the suspension dynamic stiffness of the vehicle body, improves the analysis efficiency of the transmission path, and lays a foundation for the analysis of the vibration transmission path of the vehicle body.

Drawings

FIG. 1 is a flow chart of a method for analyzing a vibration transmission path of a vehicle body according to an embodiment of the present invention;

FIG. 2 is a comparison graph of a frequency domain transfer function curve from the X direction of the left suspension passive end to the seat mounting point obtained by applying the method of the present invention and a test result, wherein a solid line is the test result, a point solid line is the result obtained by applying the method of the present invention, an abscissa is a frequency value, and an ordinate is a value obtained by multiplying the logarithm of the transfer function amplitude by 20.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings.

The flow chart of the vibration transmission path of the vehicle body in the embodiment of the invention is shown in FIG. 1, and the method comprises the following steps:

s101, establishing a transmission path analysis model by taking an engine as a source, a suspension as a path and a vehicle body as a receiver, wherein the suspension comprises a left suspension, a right suspension and a rear suspension, and each suspension comprises an engine side mounting point, namely an active end, and a vehicle body side mounting point, namely a passive end;

this step is used to build a "source-path-recipient" model, i.e., a delivery path analysis model. In the embodiment, the engine is used as a source, the suspension is used as a path, and the vehicle body is used as a receiver to establish a transmission path analysis model. The suspension of the present embodiment includes a left suspension, a right suspension, and a rear suspension. Each suspension contains two mounting points: an engine-side mounting point and a vehicle-body side mounting point. The engine-side mounting point is generally called an active end, and the vehicle-body side mounting point is generally called a passive end. It should be noted that although the present embodiment is limited to a three-suspension system, the method described in the present embodiment is also applicable to other suspension systems, such as a four-suspension system, with only slight modifications.

S102, measuring working condition response and a transfer function under an idle working condition, wherein the working condition response comprises the acceleration of two ends of each suspension and a vehicle body target point, and the transfer function comprises an exciting force-acceleration transfer function from one end of each suspension to the other end of each suspension, from one end of each suspension to the vehicle body target point, and from the vehicle body target point to one end of each suspension;

this step is used to measure the condition response and transfer function. The working condition refers to an idling working condition; the response refers to acceleration response, and specifically includes the acceleration of both ends (active end and passive end) of each suspension (left, right and rear) and a vehicle body target point (such as a seat mounting point); the transfer function refers to a transfer function from an input excitation force to an output acceleration, and specifically includes an excitation force-acceleration transfer function from one end of the suspension to the other end, from one end of the suspension to a vehicle body target point, and from the vehicle body target point to one end of the suspension. It should be noted that the transfer function herein refers to a frequency domain transfer function, and the frequency domain transfer function can be obtained by performing fast fourier transform on the time domain transfer function.

S103, predicting the working condition response of the suspension structure after virtual change based on the structural dynamics modification re-analysis technology according to the working condition response and the transfer function measured in the S102;

the method is used for predicting the working condition response of the suspension structure after virtual change by utilizing a structure dynamics modification reanalysis technology. The virtual change means that the suspension structure is not really changed, but small changes are performed on the suspension structure, and the working condition response after the suspension structure changes is solved. The re-analysis technology for structural dynamics modification appeared in the early 80 s of the last century, and is a branch of structural dynamics which takes the theory and application research of the high-efficiency re-analysis method and the structural modification re-design technology of the structural vibration characteristic value problem as main contents. At present, the structure dynamics modification re-analysis technology is relatively mature prior art.

S104, calculating the suspension stiffness of the suspension structure before changing according to the working condition response of the suspension structure after virtual changing obtained in the S103;

the method comprises the step of calculating the suspension stiffness of the suspension structure before changing according to the predicted working condition response of the suspension structure after virtual changing. Generally, a predicted working condition response is combined into a transmission path analysis estimation equation, and the equation is solved to obtain the suspension stiffness before the suspension structure is changed.

And S105, calculating the coupling force of the suspension section under the idle working condition according to the suspension rigidity, and further calculating the contribution degree of the transmission path.

This step is used to calculate the transfer path contribution. In the structural dynamics modification technique, the response of the position of the target point is considered as the linear sum of the contribution degrees of different transfer paths; each transfer path contribution is the product of the coupling force of that path and the transfer function. Therefore, the suspension section coupling force can be calculated according to the suspension stiffness obtained in the step S104, and then the transfer path contribution degree can be obtained by multiplying the coupling force by the transfer function.

As an optional embodiment, the S102 specifically includes:

acceleration sensors are arranged at two ends of the suspension and at a target point of a vehicle body to measure working condition response;

the unit force is respectively applied to the local coordinate systems at the two ends of the suspension in three directions, the acceleration of a target point of the vehicle body is measured, and the transfer function from the two ends of the suspension to the target point of the vehicle body is obtained.

The embodiment provides a technical scheme for measuring the working condition response and the transfer function. Measuring working condition response by arranging an acceleration sensor; the transfer function is obtained by applying unit exciting force to the input end and arranging an acceleration sensor at the output end to measure acceleration response. In the embodiment, by applying the unit exciting force to the input end, the calculation of dividing the acceleration response of the output end by the exciting force of the input end can be omitted, and the calculation process of the transfer function is simplified.

As an optional embodiment, the S103 specifically includes:

predicting the working condition response of the suspension passive end in elastic connection with the ground along 9 degrees of freedom according to the working condition response and the transfer function measured in the S102 and the formulas (1) to (5)

And working condition response when the suspension active end is elastically connected with the ground along 9 degrees of freedom

i is 1,2 and 3 respectively corresponding to three directions of a left suspension local coordinate system, i is 4,5 and 6 respectively corresponding to three directions of a right suspension local coordinate system, and i is 7,8 and 9 respectively corresponding to three directions of a rear suspension local coordinate system.

In the formula (1), X_itIs the i-th degree of freedom operating condition response matrix, H_itFor the ith degree of freedom transfer function matrix, Δ Z_itIs a matrix formed by elastic connection dynamic stiffness when a passive end is grounded or an active end is grounded at the ith degree of freedom,

or

Is the angular frequency; in the formula (2), H_ttAs a function of the excitation force-acceleration transfer from the target point of the vehicle body to the target point of the vehicle body, H_aitIs an excitation force-acceleration transfer function from the i-th degree of freedom of the active end to the target point of the vehicle body, H_pitIs an excitation force-acceleration transfer function from the ith degree of freedom of the passive end to the target point of the vehicle body, H_aipiIs an excitation force-acceleration transfer function from the ith degree of freedom of the active end to the passive end, H_aiaiIs an excitation force-acceleration transfer function from the i-th degree of freedom of the active end to the i-th degree of freedom of the active end, H_pipiIs an exciting force-acceleration transfer function from the ith degree of freedom of the passive end to the ith degree of freedom of the passive end; in the formula (3), X_t、X_aiAnd X_piRespectively as the target point of the vehicle body, the ith degree of freedom of the active end and the ith degree of freedom of the passive endAcceleration of (2); in the formula (4), the first and second groups,

and

respectively predicting the acceleration of a vehicle body target point, the ith degree of freedom of an active end and the ith degree of freedom of a passive end; in the formula (5), K_igThe dynamic stiffness is elastically connected for the ith degree of freedom.

The embodiment provides a technical scheme for predicting the working condition response of a suspension structure after virtual change based on a structure dynamics modification re-analysis technology. In the present embodiment, the virtual change of the suspension structure includes two cases: one is that the suspension passive end is elastically connected with the ground; one is to suspend the active end to be elastically connected with the ground. One end of the suspension is connected with the external force, namely the external force is applied to the end, and the magnitude of the external force and the dynamic stiffness K of the connection_igProportional to acceleration response (K)_ig1000 n/m may be taken). The literature (published "two methods of analysis of absolute and relative paths in discrete systems" by a. inoue, r.singh and g.a. fernandes in 2008 "journal of vibration engineering") gives a formula for predicting the response after a change in the suspension structure, as follows:

unlike the present embodiment, the response in the above equation is displacement, and the response in the present embodiment is acceleration; the transfer function in the above equation is displacement/force and the transfer function in this embodiment is acceleration/force. The steady-state response of the displacement multiplied by the square of the angular frequency is equal to the steady-state response of the acceleration, and accordingly, the prediction formula applicable to the present embodiment, namely formula (1), can be obtained by transforming the above formula. And obtaining the working condition response of the suspension structure after the virtual change according to the formulas (1) to (5).

As an alternative to the previous embodiment,the S104 specifically includes: calculating H according to equation (6)_dK_cAnd H_d,pit：

In the formula (6), the first and second groups,

byThe components are assembled to form the composite material,

by

The components are assembled to form the composite material,

assembled by the difference between the acceleration response of the active end and the acceleration response of the passive end when the suspension passive end is elastically connected with the ground,

assembled from the difference between the active end acceleration response and the passive end acceleration response when the active end and the ground are elastically connected, H_d,pitAnd (3) removing a transfer function from the ith freedom degree of the passive end to the target point of the vehicle body after the engine is removed, wherein the plus represents the solving of the virtual inverse matrix.

All H are determined_d,pitAnd is combined with H_d,pitAssembled into H_dAccording to H_dK_cAnd H_dSolving and dismantling dynamic stiffness matrix K of rear suspension of engine_c。

The embodiment provides a technical scheme for solving a stiffness matrix before structure change based on the working condition response of the suspension structure after virtual change obtained in the previous embodiment. The solving method is to combine the working condition responses predicted in the previous embodiment into a transmission path analysis estimation equation, which can be expressed as follows:

and (6) obtaining the formula (6) after the above formula is converted. The "+" in the formula (6) represents solving an imaginary inverse matrix, which means that the inverse matrix does not exist and is replaced by performing singular value matrix decomposition.

H can be obtained from the formula (6)_dK_cAnd H_d,pitFinding all H_d,pitAnd assembling it into H_d. Has H_dK_cAnd H_dThen K can be obtained_c。

As an optional embodiment of the previous embodiment, the S105 specifically includes:

calculating the coupling force of the suspension section according to the formula (7):

in the formula (7), F_cA suspension section coupling force matrix;

calculating the contribution degree of the transmission path according to a formula (8), namely the contribution component of the coupling force of the suspension section to the acceleration of a target point of the vehicle body:

in equation (8), P represents a transfer path contribution matrix.

This embodiment provides a technical solution for calculating the contribution degree of the transfer path based on the previous embodiment. The suspension section coupling force is first calculated according to formula (7), and then the transfer path contribution is calculated according to formula (8). The coupling force is equal to the product of the stiffness and the displacement steady state response, which is equal to the acceleration steady state response divided by the square of the angular frequency, from which equation (7) can be derived; the transfer path contribution is equal to the product of the coupling force of the path and the transfer function, from which equation (8) can be derived.

In order to verify the feasibility of the method of the invention, experimental verification was carried out: and (3) removing the engine of a certain type of car, and testing the frequency domain transfer function. A comparison curve of a calculation result and a test result obtained by applying the method of the invention is shown in FIG. 2, and FIG. 2 is a frequency domain transfer function curve from the X direction of the left suspension passive end to a seat mounting point (a vehicle body target point). As can be seen from the figure, the results obtained by the method of the invention are basically consistent with the actual measured values, and the feasibility of the method of the invention is shown. The method does not need to actually change the structure, so that the analysis efficiency of the vehicle body transmission path can be improved, and the application difficulty of the vehicle body transmission path analysis method is reduced.

The above description is only for the purpose of illustrating a few embodiments of the present invention, and should not be taken as limiting the scope of the present invention, in which all equivalent changes, modifications, or equivalent scaling-up or down, etc. made in accordance with the spirit of the present invention should be considered as falling within the scope of the present invention.