A method for evaluating dynamic stiffness NVH of a pure electric vehicle type suspension main drive end support

Abstract

The present application relates to pure electric vehicle howling control technology, belongs to the field of vibration and noise (NVH) control. Specifically relates to a kind of pure electric vehicle type suspension active end support dynamic stiffness NVH evaluation method, the evaluation method includes two parts of the contents of evaluation process and evaluation curve derivation process.This application can be applied in the development stage of pure electric vehicle digital prototype, help suspension active end support NVH design, so as to achieve the purpose of eliminating or weakening the howling in the car, and verified by a certain pure electric vehicle project.

Description

Technical Field

[0001] This invention relates to a whistling control technology for pure electric vehicles, specifically to a method for evaluating the dynamic stiffness (NVH) of the active suspension bracket of a pure electric vehicle, belonging to the field of vibration and noise (NVH) control. Background Technology

[0002] With societal development, the full electrification of automobiles is an inevitable trend, and numerous domestic and international OEMs have joined the research and development of pure electric vehicles. However, the excitation sources of pure electric vehicles differ significantly from those of traditional gasoline vehicles. Traditional gasoline vehicles primarily use low-frequency excitation, while pure electric vehicles primarily use high-frequency excitation, easily generating various harsh whistling sounds, thus reducing the user experience. Therefore, controlling the dynamic stiffness of the active suspension mount is crucial for suppressing whistling. Since the excitation frequencies of pure electric vehicles range from hundreds to tens of thousands of kilometres, they will inevitably couple with the active suspension mount's modes. If the dynamic stiffness of the active suspension mount is too low, the active suspension will amplify vibrations, transmitting them through the suspension and body to the passenger compartment, causing harsh whistling and leading to consumer complaints. Therefore, in the early stages of vehicle development, it is necessary to control the dynamic stiffness of the active suspension mount to avoid whistling issues in prototype vehicles that result in complaints.

[0003] After extensive data collection and literature review, the general target for the dynamic stiffness of the active suspension bracket in pure electric vehicles is 10,000 N / mm. During the digital prototype stage, CAE analysis shows that if the dynamic stiffness of the active suspension bracket is less than 10,000 N / mm, optimization of the active suspension bracket's dynamic stiffness is necessary. Increasing the bracket's dynamic stiffness during the digital prototype stage typically leads to increased costs. However, if, due to cost, space, or other reasons, a lower-than-target state is accepted during the digital prototype stage, and related problems arise after the prototype is produced, further optimization of the active suspension bracket is required, resulting in mold scrapping and remanufacturing, leading to significant waste. Therefore, OEMs urgently need a method for evaluating the NVH (Noise, Vibration, and Harshness) dynamic stiffness of the active suspension bracket in pure electric vehicles to avoid unnecessary waste of time and costs. Summary of the Invention

[0004] This invention provides a method for evaluating the dynamic stiffness and NVH (Noise, Vibration, and Harshness) of the active suspension bracket in pure electric vehicles. During the digital prototype development phase of pure electric vehicles, this method assists in the NVH design of the active suspension bracket, thereby eliminating or reducing in-vehicle whine. The method has been validated through a pure electric vehicle project. The specific technical solution is as follows:

[0005] A method for evaluating the dynamic stiffness (NVH) of the active suspension bracket in a pure electric vehicle, including the evaluation process and the derivation process of the evaluation curve:

[0006] (1) Evaluation process

[0007] s1: CAE analysis of the dynamic stiffness of the active suspension bracket to determine whether the target of 10000 N / mm has been achieved;

[0008] s2: If the goal is achieved, development is complete; if the goal is not achieved, CAE analysis is performed on the transfer function NTF1 from the elastic center point of the passive end bracket of the suspension to the driver's outer ear inside the vehicle.

[0009] s3: Determine the NTF2 transfer function from the elastic center point of the passive suspension to the driver's outer ear inside the vehicle, corresponding to the dynamic stiffness of the active suspension support, based on the evaluation curve;

[0010] s4: If NTF1≤NTF2, then development is complete; if NTF1>NTF2, then CAE analysis is performed on the dynamic stiffness of the active suspension mounting point. The general target for the dynamic stiffness of the active suspension mounting point is 100000N / mm.

[0011] s5: If the dynamic stiffness of the mounting point at the active end of the suspension reaches the target of 100,000 N / mm, then optimize the bracket structure and return to s1; if the dynamic stiffness of the mounting point at the active end of the suspension does not reach the target of 100,000 N / mm, then optimize the position and number of mounting points to improve the dynamic stiffness of the mounting points and return to s1.

[0012] (2) Evaluation curve derivation process:

[0013] Assume the dynamic stiffness of the suspension active end support is K. a The dynamic stiffness of the suspension rubber is K. b， The dynamic stiffness of the suspended passive end support is K c The total dynamic stiffness K1 of the suspension system is:

[0014]

[0015] Assuming the dynamic stiffness of the suspension rubber is infinite and the suspension system has no vibration isolation, then the total dynamic stiffness K2 of the suspension system is:

[0016]

[0017] The force F transmitted to the passive end support c The excitation force F on the active end support of the suspension a The ratio is the transmissibility T. Comparing equation (2) with equation (1), we obtain the transmissibility T as follows:

[0018]

[0019] Assuming the transfer function from the center point of the passive suspension bracket to the driver's outer ear is NTF, then the noise S in the driver's outer ear is:

[0020]

[0021] From equation (4), we can know the dynamic stiffness K of the active end of the suspension. a The NTF (Net Transfer Function) relationship between the passive suspension end bracket's elastic center point and the driver's outer ear inside the vehicle is as follows:

[0022]

[0023] Based on data collection and literature review, the dynamic stiffness K of the suspended passive end support was determined to be between 500Hz and 1500Hz. c The dynamic stiffness K of the suspension rubber is 10000 N / mm. b The value is 3000 N / mm, and the dynamic stiffness K of the active end bracket is... a The general objective is 10000 N / mm, and the general objective of the transfer function NTF from the elastic center point of the passive end bracket of the suspension to the driver's outer ear inside the vehicle is 44 dB / N. That is, in equation (5), the coordinates of a point are (10000 N / mm, 44 dB / N), and then the dynamic stiffness K of the active end of the suspension is obtained. a The NTF (Net Transfer Function) relationship between the passive suspension end bracket's elastic center point and the driver's outer ear inside the vehicle is as follows:

[0024]

[0025] Plot K according to equation (6) a The curve showing the relationship between the curve and the NTF is the evaluation curve.

[0026] Furthermore, the CAE analysis method for the dynamic stiffness of the suspended active end support in s1 is as follows:

[0027] s11: The mass of the suspension rubber is concentrated at the elastic center point of the suspension active end bracket, and the digital model only retains the suspension active end bracket and the motor assembly;

[0028] S12: Apply a unit force in a certain direction at the elastic center point of the active suspension support, obtain the displacement at the elastic center point of the active suspension support, and then take the reciprocal, which is the dynamic stiffness of the active suspension support in that direction.

[0029] Furthermore, the CAE analysis method for the transfer function from the elastic center point of the passive end bracket of the suspension in s2 to the driver's outer ear inside the vehicle is as follows:

[0030] S21: Remove the motor assembly, active suspension bracket, and suspension rubber, while retaining the passive suspension bracket and the vehicle body digital model;

[0031] S22: Apply a unit force in a certain direction at the elastic center point of the passive end bracket of the suspension to obtain the noise value of the driver's outer ear in the vehicle, which is the NTF of the transfer function from the elastic center point of the passive end bracket of the suspension to the driver's outer ear in the vehicle.

[0032] Furthermore, the CAE analysis method for the dynamic stiffness of the suspension active end mounting point in s5 is as follows:

[0033] s51: Only retain the digital model of the motor assembly and the mounting point of the active suspension end, find the center of gravity of the closed shape formed by the mounting points of the active suspension end. If the mounting points are collinear, it is the midpoint of the longest line connecting the mounting points, and the center of gravity is rigidly connected to the mounting point.

[0034] s52: Apply a unit force in a certain direction at the center of gravity, obtain the displacement at the center of gravity, and then take the reciprocal, which is the dynamic stiffness of the suspension mounting point in that direction.

[0035] The evaluation method of this invention helps in the NVH design of the active suspension bracket during the development stage of a digital prototype of a pure electric vehicle, thereby eliminating or reducing in-vehicle whistling. Attached Figure Description

[0036] Figure 1 This is a flowchart for evaluating the dynamic stiffness (NVH) of the active suspension bracket in pure electric vehicles.

[0037] Figure 2 This is a structural diagram of the suspension system for a pure electric vehicle;

[0038] Figure 3 This is the NVH evaluation curve of the dynamic stiffness of the active end bracket of the suspension for pure electric vehicles;

[0039] Figure 4 This is a CAE analysis of the Z-axis dynamic stiffness curve of the right suspension active end bracket in the base state of a certain pure electric vehicle model.

[0040] Figure 5 This is a CAE analysis of the NTF curve of the transfer function from the Z-axis of the elastic center point of the right suspension passive end bracket to the driver's outer ear inside the vehicle for a certain pure electric vehicle model.

[0041] Figure 6 This is a CAE analysis of the Z-direction dynamic stiffness curve of the right suspension active end mounting point for a certain pure electric vehicle model.

[0042] Figure 7 This is a CAE analysis of the Z-axis dynamic stiffness curve of the right suspension active end bracket in the optimized state of a certain pure electric vehicle model.

[0043] Figure 8 This is a color map of the noise level in the driver's outer ear during full-throttle acceleration in D mode of a certain pure electric vehicle. Detailed Implementation

[0044] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] Example

[0046] A method for evaluating the dynamic stiffness (NVH) of the active suspension bracket in a pure electric vehicle includes two parts: the evaluation process and the derivation of the evaluation curve.

[0047] (1) Evaluation process

[0048] like Figure 1 As shown, the NVH evaluation process for the dynamic stiffness of the active suspension bracket of a pure electric vehicle is as follows:

[0049] s1: CAE analysis of the dynamic stiffness of the active suspension bracket to determine whether the target of 10000 N / mm has been achieved;

[0050] s2: If the goal is achieved, development is complete; if the goal is not achieved, CAE analysis is performed on the transfer function NTF1 from the elastic center point of the passive end bracket of the suspension to the driver's outer ear inside the vehicle.

[0051] s3: Determine the NTF2 transfer function from the elastic center point of the passive suspension to the driver's outer ear inside the vehicle, corresponding to the dynamic stiffness of the active suspension support, based on the evaluation curve;

[0052] s4: If NTF1≤NTF2, then development is complete; if NTF1>NTF2, then CAE analysis is performed on the dynamic stiffness of the active end mounting point of the suspension. Through extensive data collection and literature review, the general target for the dynamic stiffness of the active end mounting point of the suspension is 100000 N / mm.

[0053] s5: If the dynamic stiffness of the mounting point at the active end of the suspension reaches the target of 100,000 N / mm, optimize the bracket structure and then return to s1; if the dynamic stiffness of the mounting point at the active end of the suspension does not reach the target of 100,000 N / mm, optimize the position and number of mounting points to improve the dynamic stiffness of the mounting points and then return to s1.

[0054] The CAE analysis method for the dynamic stiffness of the suspended active end support in s1 is as follows:

[0055] 1) such as Figure 2 As shown, the mass of the suspension rubber is concentrated at the elastic center point of the suspension active end bracket, and the digital model only retains the suspension active end bracket and the motor assembly;

[0056] 2) Apply a unit force in a certain direction at the elastic center point of the active suspension support, obtain the displacement at the elastic center point of the active suspension support, and then take the reciprocal, which is the dynamic stiffness of the active suspension support in that direction.

[0057] Furthermore, the CAE analysis method for the transfer function from the elastic center point of the passive end bracket of the suspension in s2 to the driver's outer ear inside the vehicle is as follows:

[0058] 1) such as Figure 2 As shown, the motor assembly, active suspension bracket, and suspension rubber are removed, while the passive suspension bracket and the vehicle body digital model are retained.

[0059] 2) Apply a unit force in a certain direction at the elastic center point of the passive end bracket of the suspension, and obtain the noise value of the driver's outer ear in the vehicle. This is the NTF transfer function from the elastic center point of the passive end bracket of the suspension to the driver's outer ear in that direction.

[0060] Furthermore, the CAE analysis method for the dynamic stiffness of the suspension active end mounting point in s5 is as follows:

[0061] 1) such as Figure 2 As shown, only the digital model of the motor assembly and the mounting point of the active suspension is retained. The center of gravity of the active suspension mounting point forming a closed shape is found (if the mounting points are collinear, it is the midpoint of the longest line connecting the mounting points), and the center of gravity is rigidly connected to the mounting point.

[0062] 2) Apply a unit force in a certain direction at the center of gravity, obtain the displacement at the center of gravity, and then take the reciprocal, which is the dynamic stiffness of the suspension mounting point in that direction.

[0063] 2. Evaluation Curve Derivation Process

[0064] like Figure 2 As shown, assume the dynamic stiffness of the suspension active end support is K. a The dynamic stiffness of the suspension rubber is K. b， The dynamic stiffness of the suspended passive end support is K c The total dynamic stiffness K1 of the suspension system is:

[0065]

[0066] Assuming the dynamic stiffness of the suspension rubber is infinite and the suspension system has no vibration isolation, then the total dynamic stiffness K2 of the suspension system is:

[0067]

[0068] The force F transmitted to the passive end support c The excitation force F on the active end support of the suspension a The ratio is the transmissibility T. Comparing equation (2) with equation (1), we obtain the transmissibility T as follows:

[0069]

[0070] Assuming the transfer function from the elastic center point of the passive suspension bracket to the driver's outer ear inside the vehicle is NTF, then

[0071] The noise level S in the driver's external ear is:

[0072]

[0073] From equation (4), we can know the dynamic stiffness K of the active end of the suspension. a The NTF (Net Transfer Function) relationship between the passive suspension end bracket's elastic center point and the driver's outer ear inside the vehicle is as follows:

[0074]

[0075] After extensive data collection and literature review, the dynamic stiffness K of the suspended passive end support was determined to be between 500Hz and 1500Hz. c Approximately 10000 N / mm, dynamic stiffness K of the suspension rubber. b Approximately 3000 N / mm, and the dynamic stiffness K of the active suspension end bracket. a The general objective is 10000 N / mm, and the general objective of the transfer function NTF from the elastic center point of the passive end bracket of the suspension to the driver's outer ear inside the vehicle is 44 dB / N. That is, in equation (5), the coordinates of a point are (10000 N / mm, 44 dB / N), and then the dynamic stiffness K of the active end of the suspension can be obtained. a The NTF (Net Transfer Function) relationship between the passive suspension end bracket's elastic center point and the driver's outer ear inside the vehicle is as follows:

[0076]

[0077] Draw K according to equation (6) a The curve showing the relationship between the curve and the NTF is the evaluation curve.

[0078] Applied to actual electric vehicle production:

[0079] During the digital prototype development phase of a certain pure electric vehicle, the Z-axis dynamic stiffness of the right-mounted active end bracket of the motor did not meet the target, requiring optimization and risk assessment. Based on the assessment process and assessment curve provided by this invention, the results are as follows:

[0080] s1: CAE analysis results of the Z-axis dynamic stiffness of the right suspension active end bracket of the motor in base state are shown below. Figure 4 At a frequency of 718Hz, the minimum dynamic stiffness is 5885N / mm, which does not meet the target of 10000N / mm.

[0081] s2: CAE analysis of the NTF curve of the transfer function from the Z-axis of the right suspension passive end bracket elastic center point to the driver's outer ear inside the vehicle is shown in the figure. Figure 5 ,pass Figure 5 It can be seen that at a frequency of 718Hz, the NTF value is 40.5dB / N, denoted as NTF1;

[0082] s3: According to Figure 3 The evaluation curve shows that the NTF corresponding to the dynamic stiffness of 5885 N / mm is 36.9 dB / N, denoted as NTF2;

[0083] If s4: NTF1 > NTF2, then CAE analysis of the dynamic stiffness of the right suspension active end mounting is required. The results are shown below. Figure 6 At a frequency of 944Hz, the minimum dynamic stiffness of the installation point is 103714N / mm, which meets the target of 100000N / mm.

[0084] s5: By optimizing the structure of the right-hand suspension active end support, CAE was used to re-analyze the Z-axis dynamic stiffness of the optimized right-hand suspension active end support. The results are shown in [the table below]. Figure 7 At a frequency of 828Hz, the minimum dynamic stiffness is 8180N / mm, which does not meet the target of 10000N / mm.

[0085] s6: Through Figure 5 It can be seen that at a frequency of 828Hz, the NTF value of the transfer function from the Z-direction of the elastic center point of the right suspension passive end bracket to the driver's outer ear inside the vehicle is 36.2dB / N, denoted as NTF3; according to Figure 3 The evaluation curve shows that the NTF corresponding to the dynamic stiffness of 8180 N / mm is 41.3 dB / N, denoted as NTF4;

[0086] s7: NTF3 < NTF4, then the risk of complaints and squealing caused by the right suspension active end bracket not meeting the standard Z-direction dynamic stiffness after evaluation of the actual vehicle is relatively small. Furthermore, if the dynamic stiffness of the bracket is further required to be improved, it will lead to a significant increase in cost and a longer development time. Therefore, the risk is relatively small and the compromise is accepted.

[0087] After the actual vehicle was produced, a driving evaluation test was conducted on the driver's external ear noise level under full throttle acceleration in D mode. Figure 8 As shown, the test data shows that there is no obvious resonance band in the driver's external ear noise around 828Hz, and there is no obvious howling in subjective driving evaluation, thus demonstrating that the evaluation method provided by the present invention is effective.

[0088] The preferred embodiments of this patent have been described in detail above. However, this patent is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of this patent.

Claims

1. A method for evaluating the dynamic stiffness (NVH) of the active suspension bracket in a pure electric vehicle, characterized in that: Includes the evaluation process and the process for deriving the evaluation curve: (1) Evaluation process s1: CAE analysis of the dynamic stiffness of the active suspension bracket to determine whether the target of 10000 N / mm has been achieved; s2: If the goal is achieved, development is complete; if the goal is not achieved, CAE analysis is performed on the transfer function NTF1 from the elastic center point of the passive end bracket of the suspension to the driver's outer ear inside the vehicle. s3: Determine the NTF2 transfer function from the elastic center point of the passive suspension to the driver's outer ear inside the vehicle, corresponding to the dynamic stiffness of the active suspension support, based on the evaluation curve; s4: If NTF1≤NTF2, then development is complete; if NTF1>NTF2, then CAE analysis is performed on the dynamic stiffness of the active suspension mounting point. The general target for the dynamic stiffness of the active suspension mounting point is 100000N / mm. s5: If the dynamic stiffness of the mounting point at the active end of the suspension reaches the target of 100,000 N / mm, then optimize the bracket structure and return to s1; if the dynamic stiffness of the mounting point at the active end of the suspension does not reach the target of 100,000 N / mm, then optimize the position and number of mounting points to improve the dynamic stiffness of the mounting points and return to s1. (2) Evaluation curve derivation process: Assume the dynamic stiffness of the suspension active end support is K. a The dynamic stiffness of the suspension rubber is K. b， The dynamic stiffness of the suspended passive end support is K c The total dynamic stiffness K1 of the suspension system is: Assuming the dynamic stiffness of the suspension rubber is infinite and the suspension system has no vibration isolation, then the total dynamic stiffness K2 of the suspension system is: The force F transmitted to the passive end support c The excitation force F on the active end support of the suspension a The ratio is the transmissibility T. Comparing equation (2) with equation (1), we obtain the transmissibility T as follows: Assuming the transfer function from the elastic center point of the passive suspension bracket to the driver's outer ear is NTF, then the noise S in the driver's outer ear is: From equation (4), we can know the dynamic stiffness K of the active end of the suspension. a The NTF relationship between the passive end support elastic center point and the driver's outer ear inside the vehicle is as follows: Within the frequency range of 500Hz to 1500Hz, the dynamic stiffness K of the suspended passive end bracket c The dynamic stiffness of the rubber is set to 10000 N / mm. b The value is 3000 N / mm, and the dynamic stiffness K of the active end bracket is... a The general objective is 10000 N / mm, and the general objective of the transfer function NTF from the elastic center point of the passive end bracket of the suspension to the driver's outer ear inside the vehicle is 44 dB / N. That is, in equation (5), the coordinates of a point are (10000 N / mm, 44 dB / N), and then the dynamic stiffness K of the active end of the suspension is obtained. a The NTF relationship between the passive end support elastic center point and the driver's outer ear inside the vehicle is as follows: Plot K according to equation (6) a The curve showing the relationship between the curve and the NTF is the evaluation curve.

2. The method for evaluating the dynamic stiffness (NVH) of the active suspension bracket of a pure electric vehicle according to claim 1, characterized in that: The CAE analysis method for the dynamic stiffness of the suspended active end support in s1 is as follows: s11: The mass of the suspension rubber is concentrated at the elastic center point of the suspension active end bracket, and the digital model only retains the suspension active end bracket and the motor assembly; S12: Apply a unit force in a certain direction at the elastic center point of the active suspension support, obtain the displacement at the elastic center point of the active suspension support, and then take the reciprocal, which is the dynamic stiffness of the active suspension support in that direction.

3. The method for evaluating the dynamic stiffness (NVH) of the active suspension bracket of a pure electric vehicle according to claim 1, characterized in that: The CAE analysis method for the transfer function from the elastic center point of the passive end bracket of the suspension in s2 to the driver's external ear inside the vehicle is as follows: S21: Remove the motor assembly, active suspension bracket, and suspension rubber, while retaining the passive suspension bracket and the vehicle body digital model; S22: Apply a unit force in a certain direction at the elastic center point of the passive end bracket of the suspension to obtain the noise value of the driver's outer ear in the vehicle, which is the transfer function NTF1 from the elastic center point of the passive end bracket of the suspension to the driver's outer ear in the vehicle.

4. The method for evaluating the dynamic stiffness (NVH) of the active suspension bracket of a pure electric vehicle according to claim 1, characterized in that: The CAE analysis method for the dynamic stiffness of the suspension active end mounting point in s5 is as follows: s51: Only retain the digital model of the motor assembly and the mounting point of the active suspension end, find the center of gravity of the closed shape formed by the mounting points of the active suspension end. If the mounting points are collinear, it is the midpoint of the longest line connecting the mounting points, and the center of gravity is rigidly connected to the mounting point. s52: Apply a unit force in a certain direction at the center of gravity, obtain the displacement at the center of gravity, and then take the reciprocal, which is the dynamic stiffness of the suspension mounting point in that direction.

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