Method for predicting and optimizing noise vibration in whole vehicle under excitation of cooling fan

Abstract

The invention relates to a whole vehicle interior noise vibration prediction and optimization method under cooling fan excitation. The method comprises the steps that cooling fan simulation working condition first-order unbalance excitation test calculation is carried out; carrying out finite element modeling and assembling on the whole vehicle; fan accessory modeling; checking the whole vehicle model; establishing an acoustic cavity finite element model; in-vehicle vibration noise prediction under fan excitation in the whole vehicle state; optimizing the design; performing problem frequency diagnosis; and a plurality of optimization schemes are formulated for problem frequency diagnosis. First-order unbalance excitation is applied to the mass center of the cooling fan to simulate the working condition, in-vehicle noise and vibration response are obtained through simulation under excitation of the cooling fan, the problem frequency is screened, an optimization scheme is proposed through diagnostic analysis, the effectiveness of whole-vehicle NVH problem investigation excited by the cooling fan and the correctness of the optimization direction can be guaranteed, and the method is suitable for large-scale popularization and application. Fan scheme selection and target control can be carried out in the early stage of a project, indexes can be verified in the middle stage of the project, if not, optimization scheme design is carried out, cost can be saved, and the research and development period can be shortened.

Description

Technical Field

[0001] The invention belongs to the technical field of automobiles, and in particular relates to a method for predicting and optimizing the noise and vibration inside a vehicle under the excitation of a cooling fan. Background Art

[0002] As people are increasingly pursuing riding comfort, automobile manufacturers are also paying more and more attention to the comfort performance of vehicles. Among them, the noise and vibration inside the vehicle generated during driving are an important factor affecting the comfort of the vehicle. The working noise of the cooling fan is one of the main noise sources affecting the noise inside the vehicle. Especially today when electric vehicles are becoming more and more popular, due to the lack of the cover of the engine working noise, the noise of the cooling fan at work becomes more obvious in the car, which is easy to cause customer complaints and affect the riding comfort of the whole vehicle. In order to solve the impact of the working noise of the cooling fan on the comfort inside the car and reduce the noise inside the car, it is particularly necessary to predict and control the working noise of the cooling fan at the front end of the electric vehicle.

[0003] At present, the analysis of automobile cooling fan noise is usually measured and optimized on a cooling fan single-unit test bench, while the vehicle-level cooling fan noise is generally tested under the condition that the air conditioner is turned on on the vehicle. The voltage at the cooling fan terminal is affected by factors such as battery power and coolant temperature in the vehicle state, resulting in uncontrollable speed of the cooling fan during actual operation. At the same time, when the air conditioner is turned on, the noise of the cooling fan is also affected by the working noise of the compressor and blower, and it is impossible to measure and optimize it alone in the vehicle state. Existing simulation technology mainly analyzes the in-vehicle response under engine excitation and road excitation, ignoring the in-vehicle noise vibration response generated by the cooling fan excitation, and it is difficult to formulate selection and layout plans in the early stage of the project. The above factors make it difficult to accurately control and optimize the cooling fan noise in the middle and late stages of the project. Summary of the invention

[0004] The purpose of the present invention is to provide a method for predicting and optimizing the interior noise and vibration of a vehicle under the excitation of a cooling fan, so as to solve the problem of the influence of the working noise of the cooling fan on the comfort inside the vehicle and reduce the noise inside the vehicle.

[0005] The objective of the present invention is achieved through the following technical solutions:

[0006] A method for predicting and optimizing vehicle interior noise and vibration under cooling fan excitation comprises the following steps:

[0007] A. First-order unbalanced excitation test calculation for cooling fan simulation working condition;

[0008] B. Finite element modeling and assembly of the whole vehicle;

[0009] C. Fan accessory modeling;

[0010] D. Carry out vehicle model inspection;

[0011] E. Establishment of finite element model of vocal cavity;

[0012] F. Prediction of in-vehicle vibration and noise under fan excitation in the whole vehicle state;

[0013] G. Optimize design;

[0014] H. Problem frequency diagnosis;

[0015] I. Problem frequency diagnosis and formulation of multiple optimization plans.

[0016] Further, step A is specifically as follows: according to the fan speed, unbalanced mass and eccentric distance, etc., by using the dynamic balancing principle, the forces in the Y, Z, RY and RZ directions of the whole vehicle coordinates are calculated to obtain the first-order unbalanced excitation.

[0017] Furthermore, step B specifically includes: fully decorated body modeling, powertrain modeling, chassis system modeling, and connection between chassis and chassis and body; the fully decorated body modeling includes body sheet metal parts and structural parts modeling, body accessory modeling: non-structural mass, concentrated mass points and connection modeling.

[0018] Furthermore, step C specifically includes: establishing mass points according to the center of mass and inertia position of the fan, assigning inertia, and using a CBUSH unit to simulate the connection between the fan and the bracket.

[0019] Furthermore, step D is specifically as follows: performing modal analysis on the whole vehicle model to check whether there are connection errors and attribute assignment errors in the model.

[0020] Furthermore, in step E, when establishing the acoustic cavity, only the panels that fit the acoustic cavity are considered, including the panels and seats inside the vehicle, and the panels in contact with the air are displayed separately, and then the Acoustic Cavity Mesh method is used for modeling.

[0021] Furthermore, step F is specifically as follows: loading the obtained centrifugal force and moment of inertia in the Y direction and the Z direction at the centroid of the fan into the vehicle interior noise and vibration prediction simulation model to obtain the vehicle interior noise and vibration response results.

[0022] Furthermore, step G is specifically as follows: comparing the obtained simulation result with the fan control target to identify the problem frequency that needs to be optimized.

[0023] Furthermore, step H is specifically as follows: by performing modal contribution analysis, node contribution analysis and sensitivity analysis on the identified problem frequency, the excitation source, key node contribution, key modal contribution, key components and highly sensitive parameters that cause the problem corresponding to the problem frequency are identified.

[0024] Furthermore, step I: is executed in a computer program of a computer, and the cooling fan control target, the excitation source frequency distribution table and the vehicle modal distribution table are stored in the computer as a comparison database, and then the problem frequency to be optimized is input into the computer program, and the node contribution, modal contribution and high sensitivity parameters of the screened problem frequency are obtained after calculation by the program.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The present invention proposes an in-vehicle noise and vibration response analysis under a whole vehicle state based on blower excitation. The working condition is simulated by applying a first-order unbalanced excitation at the center of mass of the cooling fan, and the in-vehicle noise and vibration response are simulated under the excitation, the problem frequency is screened, and then an optimization plan is proposed through diagnostic analysis. The effectiveness of the NVH problem troubleshooting of the whole vehicle under cooling fan excitation and the correctness of the optimization direction can be ensured. Fan plan selection and target control can be carried out in the early stage of the project, and verification indicators can be carried out in the middle stage of the project. If they are not achieved, an optimization plan design is carried out. This method can save vehicle development funds and time costs and shorten the research and development cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] 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. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0028] Figure 1 : Schematic diagram of first-order unbalanced excitation in the Y direction;

[0029] Figure 2 : Flow chart of the steps of the method for predicting and optimizing the interior noise and vibration of a vehicle under the excitation of the cooling fan of the present invention. DETAILED DESCRIPTION

[0030] The present invention will be further described below in conjunction with embodiments:

[0031] At present, the analysis of automobile cooling fan noise is generally measured and optimized on a cooling fan unit test bench. When the cooling fan is installed on the whole vehicle, it is affected by factors such as the compressor, blower, engine, battery power, and cooling temperature. It is impossible to accurately test and optimize it alone in the whole vehicle state.

[0032] To this end, the present invention provides a method for predicting and optimizing the interior noise and vibration of a vehicle under the excitation of a cooling fan, including first-order unbalanced excitation calculation of the cooling fan simulation working condition, finite element modeling and assembly of the whole vehicle, establishment of a finite element model of the acoustic cavity, calculation of the interior vibration and noise under the excitation of the fan in the whole vehicle state, and optimization design to solve the above problems. The method includes the following steps:

[0033] 1. Calculation of first-order unbalanced excitation test for cooling fan simulation conditions: Based on the fan speed, unbalanced mass and eccentric distance, etc., the forces in the Y, Z, RY and RZ directions of the vehicle coordinates are calculated through the dynamic balancing principle to obtain the first-order unbalanced excitation.

[0034] 2. Finite element modeling and assembly of the whole vehicle: including full body modeling, powertrain modeling, chassis system modeling, and the connection between chassis and chassis and body. The full body modeling includes body sheet metal and structural parts modeling, body accessories modeling: non-structural mass, concentrated mass points and connection modeling, etc.

[0035] 3. Fan accessory modeling: Establish mass points according to the fan's center of mass and inertia position, assign inertia, and use CBUSH units to simulate the connection between the fan and the bracket.

[0036] 4. Check the whole vehicle model: Perform modal analysis on the whole vehicle model to check whether there are connection errors, attribute assignment errors, etc. in the model.

[0037] 5. Establishment of the finite element model of the acoustic cavity: When establishing the acoustic cavity, generally only the panels that fit the acoustic cavity are considered, including the panels and seats inside the vehicle. The panels in contact with the air are displayed separately, and then the Acoustic Cavity Mesh method is used for modeling.

[0038] 6. Prediction of in-vehicle vibration and noise under fan excitation in the whole vehicle state: The centrifugal force and moment of inertia in the Y and Z directions at the center of mass of the fan are loaded into the simulation model for in-vehicle noise and vibration prediction to obtain the in-vehicle noise and vibration response results.

[0039] 7. Optimize design: Compare the simulation results with the fan control objectives to identify the problem frequencies that need to be optimized.

[0040] 8. Problem frequency diagnosis: By performing modal contribution analysis, node contribution analysis and sensitivity analysis on the identified problem frequency, the excitation source, key node contribution, key modal contribution, key components and highly sensitive parameters that cause the problem frequency can be identified.

[0041] 9. Problem frequency diagnosis formulates multiple optimization plans, taking into account the comprehensive impact of multiple optimization plans on cost, weight, engineering implementation complexity and vehicle performance. According to different performance positioning, formulate optimization plan combinations to seek the best balance between performance and benefits, ensure significant results in cost control, weight reduction, engineering implementation convenience improvement and vehicle performance optimization, and better meet the actual needs of different vehicle performance positioning, providing strong support for the overall performance improvement of the vehicle.

[0042] It is executed in a computer program, and the cooling fan control target, the excitation source frequency distribution table and the vehicle modal distribution table are stored in the computer to serve as a comparison database. The problem frequency to be optimized is then input into the computer program, and the node contribution, modal contribution and high sensitivity parameters of the screened problem frequency are obtained after calculation by the program.

[0043] If the optimization scheme can meet the in-vehicle response control requirements under fan excitation, the optimization process ends; otherwise, return to step 7 to continue the analysis.

[0044] Example 1

[0045] A method for predicting and optimizing the interior noise and vibration of a vehicle under the excitation of a cooling fan, so as to effectively control the fan selection and layout in the early stage of the project, and to propose optimization plans for the problems in the later stage of the project, providing an effective reference for the forward development of products, reducing costs, and improving the NVH performance of the vehicle.

[0046] 1. The excitation of the fan is usually related to the centrifugal force generated by the rotation. According to the fan speed, unbalanced mass and rotation radius, the forces in the Y and Z directions and the rotational inertia forces in the Y and Z directions under the vehicle coordinates are calculated through the dynamic balancing principle and the moment of inertia principle, and the first-order unbalanced excitation is obtained, as shown in formula (1). Figure (1) shows the first-order unbalanced excitation in the Y direction.

[0047] F = m * r * ω^2 (1)

[0048] Among them, F is the centrifugal force, m is the unbalanced mass, r is the distance from the unbalanced mass to the rotation axis, that is, the eccentricity, and ω is the angular velocity (rotation speed). The rotational inertia force needs to add a 90° phase.

[0049] 2. Finite element modeling and assembly of the whole vehicle: including full body modeling (body sheet metal and structural parts modeling, body accessory modeling: non-structural mass, concentrated mass points and connection modeling, etc.), powertrain modeling, chassis system modeling, and connection between chassis and chassis and body.

[0050] 3. Establish mass points according to the fan's center of mass and inertia position, assign inertia, and use CBUSH units to simulate the connection between the fan and the bracket.

[0051] 4. Check the whole vehicle model: Perform modal analysis on the whole vehicle model to check whether there are connection errors, attribute assignment errors, etc. in the model.

[0052] 5. Establishment of the finite element model of the acoustic cavity: When establishing the acoustic cavity, generally only the panels that fit the acoustic cavity are considered, including the panels and seats inside the vehicle. The panels in contact with the air are displayed separately, and then the Acoustic Cavity Mesh method is used to model it, and the mass stiffness damping is set.

[0053] 6. Prediction of in-vehicle vibration and noise under fan excitation in the whole vehicle state: The centrifugal force and moment of inertia in the Y and Z directions at the center of mass of the fan obtained in step 3 are loaded into the whole vehicle interior noise and vibration prediction simulation model to obtain the in-vehicle noise and vibration response results.

[0054] Y=H×F

[0055] Among them, Y represents the sound pressure or vibration acceleration at the response point in the vehicle, F represents the input excitation force, and H represents the transfer function.

[0056] 7. Optimize the design: Compare the simulation results obtained in step 6 with the fan control target to identify the problem frequencies that need to be optimized.

[0057] 8. Problem frequency diagnosis: Perform modal contribution analysis, node contribution analysis and sensitivity analysis on the problem frequency identified in step 7 to identify the excitation source, key node contribution analysis, key modal contribution analysis, key components and highly sensitive parameters that cause the problem frequency.

[0058] Modal contribution analysis is a frequency response analysis based on structural modes. It uses the modal superposition method to obtain the contribution of each modal order at the peak frequency of the problem. Analyze and control the structure with large contribution to effectively reduce the response inside the vehicle.

[0059] Node contribution analysis directly outputs the contribution of nodes on the fluid-solid interface to the response points in the acoustic cavity. It can effectively identify the size of the acoustic contribution of the local area of ​​the structure to the response point. To solve the problem of in-vehicle noise, it is necessary to optimize the node area with large contribution. The figure below is a schematic diagram of the node contribution of in-vehicle noise at a certain frequency.

[0060] Sensitivity analysis can reflect the sensitivity of the noise response in the car to parameter changes. The greater the sensitivity, the greater the response in the car. The parameter of the present invention is the property cbush of the simulated connection between the bracket and the fan, which includes the stiffness and damping of the directions X, Y and Z of each connection point.

[0061] 9. Based on the problem frequency diagnosis, multiple optimization plans are formulated, taking into account the comprehensive impact of multiple optimization plans on cost, weight, engineering implementation complexity and vehicle performance. According to different performance positioning, a combination of optimization plans is formulated to seek the best balance between performance and benefits, ensuring significant results in cost control, weight reduction, improvement of engineering implementation convenience and vehicle performance optimization, which can better meet the actual needs of different vehicle performance positioning and provide strong support for the overall performance improvement of the vehicle.

[0062] The above steps are executed in a computer program, and the cooling fan control target, the excitation source frequency distribution table and the vehicle modal distribution table are stored in the computer as a comparison database, and then the problem frequency to be optimized is input into the computer program, and the node contribution, modal contribution and high sensitivity parameters of the screened problem frequency are obtained after the program calculates. When the above steps are implemented, the computer program is developed using two programming languages, Java and Python, to achieve the required functions.

[0063] Table 1

[0064]

[0065] The present invention designs a single optimization scheme or a combined optimization scheme for ranking contribution and sensitivity parameters, and re-inputs them into the model for verification. The above schemes include adding an acoustic package, increasing or reducing local stiffness, changing the fan and bracket connection parameters, and combinations of the above schemes. When the optimization scheme can meet the in-vehicle response control requirements under fan excitation, the optimization process ends, otherwise it returns to the optimization design process to continue the analysis.

[0066] The present invention calculates the unbalanced forces in directions Y, Z and RY, RZ as excitation loads according to the cooling fan parameters; establishes a whole vehicle model based on cooling fan excitation by simulation means, and calculates the set in-vehicle vibration and noise response points; develops a computer program, inputs the problem frequency to be optimized into the computer program, and obtains the node contribution, modal contribution and high sensitivity parameters of the screened problem frequency after calculation by the program, so as to provide for subsequent scheme design and optimization.

[0067] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A method for predicting and optimizing the interior noise and vibration of a vehicle under the excitation of a cooling fan, characterized in that: The following steps are involved: A. First-order unbalanced excitation test calculation for cooling fan simulation working condition; B. Finite element modeling and assembly of the whole vehicle; C. Fan accessory modeling; D. Carry out vehicle model inspection; E. Establishment of finite element model of vocal cavity; F. Prediction of in-vehicle vibration and noise under fan excitation in the whole vehicle state; G. Optimize design; H. Problem frequency diagnosis; I. Problem frequency diagnosis and formulation of multiple optimization plans.

2. The method for predicting and optimizing vehicle interior noise and vibration under cooling fan excitation according to claim 1, characterized in that: Step A is specifically as follows: according to the fan speed, unbalanced mass and eccentric distance, etc., the forces in the Y, Z, RY and RZ directions of the vehicle coordinates are calculated by the dynamic balancing principle to obtain the first-order unbalanced excitation.

3. The method for predicting and optimizing vehicle interior noise and vibration under cooling fan excitation according to claim 1, characterized in that: Step B specifically includes: fully decorated body modeling, powertrain modeling, chassis system modeling, and the connection between chassis and chassis and body; the fully decorated body modeling includes body sheet metal parts and structural parts modeling, body accessory modeling: non-structural mass, concentrated mass points and connection modeling.

4. The method for predicting and optimizing vehicle interior noise and vibration under cooling fan excitation according to claim 1, characterized in that: Step C specifically includes: establishing mass points according to the center of mass and inertia position of the fan, assigning inertia, and using CBUSH units to simulate the connection between the fan and the bracket.

5. The method for predicting and optimizing vehicle interior noise and vibration under cooling fan excitation according to claim 1, characterized in that: Step D is specifically as follows: performing modal analysis on the whole vehicle model to check whether there are connection errors and attribute assignment errors in the model.

6. The method for predicting and optimizing vehicle interior noise and vibration under cooling fan excitation according to claim 1, characterized in that: In step E, when establishing the acoustic cavity, only the panels that fit the acoustic cavity are considered, including the interior panels and seats. The panels that come into contact with the air are displayed separately, and then the Acoustic Cavity Mesh method is used for modeling.

7. The method for predicting and optimizing vehicle interior noise and vibration under cooling fan excitation according to claim 1, characterized in that: Step F is specifically as follows: loading the obtained centrifugal force and moment of inertia in the Y direction and the Z direction at the centroid of the fan into the vehicle interior noise and vibration prediction simulation model to obtain the vehicle interior noise and vibration response results.

8. The method for predicting and optimizing vehicle interior noise and vibration under cooling fan excitation according to claim 1, characterized in that: Step G is specifically: comparing the obtained simulation results with the fan control target to identify the problem frequency that needs to be optimized.

9. The method for predicting and optimizing vehicle interior noise and vibration under cooling fan excitation according to claim 1, characterized in that: Step H is specifically as follows: by performing modal contribution analysis, node contribution analysis and sensitivity analysis on the identified problem frequency, the excitation source, key node contribution, key modal contribution, key components and highly sensitive parameters that cause the problem frequency are identified.

10. The method for predicting and optimizing vehicle interior noise and vibration under cooling fan excitation according to claim 1, characterized in that: Step I: Execute in a computer program of a computer, and store the cooling fan control target, the excitation source frequency distribution table and the vehicle modal distribution table in the computer as a comparison database, and then input the problem frequency to be optimized in the computer program, and obtain the node contribution, modal contribution and high sensitivity parameters of the screened problem frequency after calculation by the program.

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