Method and system for determining engine speed during idle charging operating condition

Abstract

The present application relates to a kind of engine speed determination method and system when idling charging working condition, the method specifically is: S1: establishing the finite element simulation model of vehicle NVH, and carrying out vehicle modal analysis;S2: through the engine speed range under idling charging working condition, obtain the excitation frequency range corresponding to each subsystem and power assembly of vehicle;S3: based on S1 and S2, whether the vehicle modal can avoid the excitation frequency of each subsystem and power assembly of vehicle is judged, if can avoid then end, if cannot then enter S4;S4: obtain the cylinder pressure excitation of engine at different speeds under idling charging working condition, carry out vehicle NVH performance analysis, obtain the vibration speed at steering wheel and the noise sound pressure at the right ear of driver under different speeds;S5: based on steering wheel vibration speed and the noise sound pressure at the right ear of driver, determine the engine speed of idling charging working condition.The present application reaches vehicle NVH performance target requirement, reduces later rectification cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hybrid electric vehicles, in particular to NVH technology. BACKGROUND

[0002] At present, under the pressure of energy saving and emission reduction and double credit policy, electrification will be an important trend and development direction of the future automobile industry; and the electrification with engine is classified as hybrid, which is the only way to the transition from traditional power to pure electric, and will exist for a long time. Most car companies have launched corresponding hybrid models, realizing a hybrid power actual use fuel economy of 40%-50%, reducing fuel consumption, helping users to significantly reduce vehicle costs, and meeting increasingly stringent fuel consumption and emission regulations. However, when the battery power is insufficient during idling, the engine needs to charge the battery, resulting in higher idling speed and output power than traditional fuel vehicles; there is coupling of steering system modal, first-order acoustic cavity modal, etc., which easily leads to low-frequency ear-pressing sound, steering wheel vibration and other vehicle NVH problems, and the comfort is obviously worse than that of traditional fuel vehicles, which easily causes customer complaints. SUMMARY

[0003] One of the purposes of the present application is to provide a method for determining engine speed during idling charging condition, to solve the problem of low-frequency ear-pressing sound, steering wheel vibration and other vehicle NVH problems during idling charging condition of hybrid vehicles; the second purpose is to provide a speed control system during idling charging condition.

[0004] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0005] A method for determining engine speed during idling charging condition, the method specifically comprises:

[0006] S1: establishing a vehicle NVH finite element simulation model and performing vehicle modal analysis;

[0007] S2: obtaining the excitation frequency range of each subsystem and powertrain of the vehicle through the engine speed range during idling charging condition;

[0008] S3: based on S1 and S2, determining whether the vehicle modal can avoid the excitation frequency of each subsystem and powertrain of the vehicle, if yes, ending, if not, entering S4;

[0009] S4: obtaining the cylinder pressure excitation of the engine at different speeds during idling charging condition, performing vehicle NVH performance analysis, and obtaining the steering wheel vibration speed and the noise sound pressure at the right ear of the driver at different speeds;

[0010] S5: determining the optimal idling speed of the engine during idling charging condition based on the steering wheel vibration speed and the noise sound pressure at the right ear of the driver.

[0011] According to the above technical means, based on the finite element simulation, the excitation frequency range of each subsystem and the power assembly of the whole vehicle in the engine idle condition is judged, and then whether to perform the speed optimization of the engine idle charging condition is judged according to whether there is the possibility of resonance, and then the simulation means is used to identify the NVH performance risk of the hybrid vehicle in the idle charging condition in the early stage of the project development, and the speed optimization is performed based on the vibration speed at the steering wheel and the noise sound pressure at the right ear of the driver, that is, the subjective experience of the driver, so as to effectively reduce the influence of the vibration in the idle charging condition on the passengers and the driver, and the optimal engine speed in the idle condition can be locked in advance in the project development, and the development cycle is shortened.

[0012] Further, the S5 is specifically:

[0013] ① If the steering wheel vibration speed and the noise sound pressure at the right ear of the driver both meet the performance target requirements, the engine speed corresponding to the minimum steering wheel vibration is selected to run;

[0014] ② If one of the steering wheel vibration speed and the noise sound pressure at the right ear of the driver meets the performance target, and the other does not meet the performance target, the optimal engine speed is determined based on the fuel consumption economy or the cost of optimizing the project that does not meet the performance target;

[0015] ③ If the steering wheel vibration speed and the noise sound pressure at the right ear of the driver both do not meet the performance target requirements, the engine speed corresponding to the minimum steering wheel vibration is selected to run.

[0016] Further, the method for obtaining the cylinder pressure excitation under different idle charging speeds in the S4 is:

[0017] The in-cylinder pressure under different loads and different speeds in the idle condition is obtained, and the time domain excitation of the engine is obtained based on the cylinder pressure data and the basic parameters of the engine, and then the time domain excitation is converted into frequency domain excitation, and then the cylinder pressure excitation under different idle charging speeds is obtained.

[0018] Further, the method for obtaining the in-cylinder pressure under different loads and different speeds in the idle condition is:

[0019] For a certain load condition, the relationship curve between the angle and the cylinder pressure of the engine at each speed is extracted from the original test data by adjusting the throttle opening;

[0020] The relationship curve between the angle and the cylinder pressure of the engine at each speed under the same load and different speeds is summarized to synthesize the relationship curve of the cylinder pressure-crankshaft angle-engine speed;

[0021] The step of repeatedly acquiring the cylinder pressure-crank angle-engine speed relationship curve is finally performed under different loads and different speeds to obtain cylinder pressure-crank angle-engine speed relationship curves under different loads and different speeds.

[0022] Further, the method for obtaining the time-domain excitation of the engine based on the cylinder pressure data and the engine basic parameters and converting the time-domain excitation into a frequency-domain excitation comprises: calculating the engine excitation time-domain curve of the combustion force, the inertial force and the unbalanced force in a cycle by using the engine cylinder pressure data and the engine basic parameters through the engine MBD model; combining the engine excitation time-domain result, converting the time-domain excitation into a frequency-domain excitation through fast Fourier transform, and then extracting the excitation frequency amplitude and phase corresponding to the relevant order to complete the conversion of the time-domain load into the frequency-domain load.

[0023] Further, the method for obtaining the analysis model for performing the whole vehicle NVH performance analysis in S4 comprises: loading the cylinder pressure excitation under different idle charging speeds as input excitation to the whole vehicle NVH finite element simulation model.

[0024] An idle charging condition speed control system based on the above determination method, comprising a finite element module configured to establish a whole vehicle NVH finite element simulation model and perform whole vehicle modal analysis.

[0025] A whole vehicle modal frequency avoidance judgment module obtains the excitation frequency ranges of each subsystem and the powertrain of the whole vehicle in the engine speed range under the idle charging condition, and compares the whole vehicle modal frequency with the excitation frequency ranges to determine whether the whole vehicle modal frequency can avoid the excitation frequency of each subsystem and the powertrain of the whole vehicle.

[0026] A noise acquisition module configured to acquire the cylinder pressure excitation of the engine under different speeds under the idle charging condition, perform whole vehicle NVH performance analysis, and obtain the response peak values of the steering wheel vibration speed and the noise sound pressure at the right ear of the driver under different speeds.

[0027] A whole vehicle NVH performance rectification strategy selection module configured to determine the engine speed under the idle charging condition based on the steering wheel vibration speed and the noise sound pressure at the right ear of the driver.

[0028] Further, the method for determining the speed under the idle charging condition in the whole vehicle NVH performance rectification strategy selection module comprises:

[0029] ① If the steering wheel vibration speed and the noise sound pressure at the right ear of the driver both meet the performance target requirements of the standard, the engine speed corresponding to the minimum steering wheel vibration is selected for operation.

[0030] If one of the steering wheel vibration speed and the noise sound pressure of the right ear of the driver meets the performance target of the calibration, and the other does not meet the performance target of the calibration, the optimal engine speed is determined based on the fuel consumption economy or the cost of optimizing the item not meeting the performance target;

[0031] If both the steering wheel vibration speed and the noise sound pressure of the right ear of the driver do not meet the performance target of the calibration, the engine speed corresponding to the minimum steering wheel vibration is selected for operation.

[0032] Further, the method for the noise acquisition module to acquire the cylinder pressure excitation of the engine under different speeds in the idling charging working condition is:

[0033] The in-cylinder pressure under different loads and different speeds in the idling working condition is obtained, and the time-domain excitation of the engine is acquired based on the cylinder pressure data and the basic parameters of the engine, and then the time-domain excitation is converted into frequency-domain excitation, and thus the cylinder pressure excitation under different idling charging speeds is obtained.

[0034] Further, the method for the noise acquisition module to acquire the in-cylinder pressure under different loads and different speeds in the idling working condition is:

[0035] For a certain load working condition, the relationship curve between the angle and the cylinder pressure of the engine under each speed is extracted from the original test data by adjusting the throttle opening degree;

[0036] The relationship curves between the angle and the cylinder pressure of the engine under each speed under different speeds of the same load are summarized to synthesize the relationship curve of the cylinder pressure-crankshaft angle-engine speed;

[0037] The relationship curve of the cylinder pressure-crankshaft angle-engine speed is repeatedly acquired under different loads and different speeds, and finally the relationship curve of the cylinder pressure-crankshaft angle-engine speed under different loads and different speeds is obtained.

[0038] The beneficial effects of the present application are:

[0039] The present application provides a method for determining the engine speed in the idling charging working condition of a hybrid vehicle, which optimizes the vehicle NVH performance through the speed control strategy, solves the vehicle NVH problem caused by the high speed in the idling charging working condition of the hybrid vehicle and the easy coupling of the mode, locks the optimal idling charging speed before the data of the project vehicle is frozen, meets the reasonable frequency avoidance with the inherent frequency of other subsystems, achieves the requirement of the vehicle NVH performance target, and reduces the cost of later rectification. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 The flowchart of the embodiment 1 of the present application is shown in the figure;

[0041] Figure 2 The schematic diagram of the cylinder pressure excitation loading position is shown in the figure;

[0042] Figure 3 a transmission path of vibration excited by a power assembly;

[0043] Figure 4 Fig. 2 is a schematic diagram of vehicle NVH performance analysis for different idle charging speeds, wherein (a) is a relationship between speed and right ear noise of a driver under an engine idle charging condition; and (b) is a relationship between speed and steering wheel vibration under the engine idle charging condition;

[0044] Figure 5 Fig. 4 is a structural diagram of embodiment 2 of the present application.

[0045] wherein 1 is a finite element module; 2 is a vehicle modal frequency avoidance judgment module; 3 is a noise acquisition module; and 4 is a vehicle NVH performance improvement strategy selection module. DETAILED DESCRIPTION

[0046] Other advantages and effects of the present application can be easily understood by those skilled in the art from the above description. The present application can also be implemented or applied in other different specific embodiments, and various modifications or changes can be made to the details in the specification based on different views and applications without departing from the spirit of the present application. It should be understood that the preferred embodiments are only for illustrating the present application, but not for limiting the protection scope of the present application.

[0047] It should be noted that the diagrams provided in the following embodiments only schematically illustrate the basic concept of the present application, and only the components related to the present application are shown in the diagrams, but not the number, shape and size of the components in actual implementation. The type, number and proportion of the components in actual implementation can be arbitrarily changed, and the layout type of the components can be more complex.

[0048] Embodiment 1

[0049] The embodiment provides a method for determining engine speed under an idle charging condition, as shown in Fig. 1, specifically comprising the following steps. Figure 1 S1: establishing a vehicle NVH finite element simulation model, and performing vehicle modal analysis;

[0050] S1: establishing a vehicle NVH finite element simulation model, and performing vehicle modal analysis;

[0051] The vehicle parameters include 3D design data of vehicle subsystems such as a body system, an exhaust system, a power transmission system, a fuel system, a suspension system, a braking system, a steering system and a power battery system.

[0052] The power assembly parameters include related parameters such as mass, mass center coordinates, rotational inertia, suspension elastic center coordinates and suspension 20Hz bushing dynamic stiffness values.

[0053] The whole vehicle NVH simulation model building method is:

[0054] Firstly, the powertrain model is established. In the pre-processing software environment, the powertrain mass, mass center coordinates, rotational inertia, suspension elastic center coordinates, suspension dynamic stiffness and other related parameters collected in step 1 are input and set; the powertrain is simplified as a mass point, the mass center point is established and the mass, mass center and rotational inertia information are given through 1D-mass; the suspension dynamic stiffness is simulated by cbush unit, the suspension point is established according to the given suspension elastic center coordinates, and the rbe2 unit is used to connect the suspension point and the engine mass center, so that the related parameters in the powertrain model are consistent with the actual situation. Thus, the powertrain modeling is completed.

[0055] Then the body system model is established. In the pre-processing software environment, the 3D design data of the body sheet metal collected in step 1 is meshed by 2D unit; due to the complex geometry of the body, the main geometric features of the body are retained, and some structures such as flanging, small holes, chamfers and small bosses which have little effect on the calculation results are ignored; at the same time, in order to meet the requirements of calculation efficiency and accuracy, the 8*8mm quadrilateral unit is mainly used for the modeling of the body-in-white and closed parts, the 7*7mm quadrilateral unit is mainly used for the modeling of the hub package and B column, and the 5*5mm quadrilateral unit is mainly used for the modeling of the subframe and torsion beam; the specific related size of the fuel tank, CCB and interior parts is coordinated for modeling; the grid quality of all established finite element models is checked, and the TRIA unit number is less than or equal to 5%; except for structural restrictions, no more than two TRIA units are allowed to be connected together, and the modeling grid is adjusted to the middle surface of the part thickness. The body structure connection mode is complex, mainly including spot welding, bolting and gluing, etc., the connection mode between each part needs to be effectively simulated to ensure the calculation accuracy; the weld is established by CONNECTOR and contains the welding layer information; at least three rows of units are guaranteed for the welding edge, the weld points with different welding layers are placed in different COMPs, the acm(shellgap) weld type is adopted, and the point-to-point modeling is needed for the welding seam, laser welding and plug welding in modeling; the glue is simulated by RBE2-SOLID-RBE3, and the common nodes between the connected units are guaranteed; the bolt is connected by a pair of RBE2 units connecting the hole center node with the first and second layer nodes of the hole. After grid division and connection simulation, the related model needs to be given material properties and structure properties; the weld and glue are given PSOLID properties, and the structure plate is given PSHELL properties; finally, according to the installation position of the actual vehicle, the related interior parts are simplified as concentrated mass points added to the body finite element model to obtain the interior body finite element model

[0056] Secondly, the chassis model is established. In the pre-processing software environment, the 3D design data of the chassis subsystems collected in step 1, such as the power system, the exhaust system, the power transmission system, the fuel system, the suspension system, the brake system, the steering system and the power battery system, are meshed and connected. The sheet metal parts in the chassis are connected and modeled in accordance with the requirements of the vehicle body. In addition, the transmission system uses MPC units to establish the transmission ratio of each gear and the main reduction ratio. Each gear needs to be placed in a different loadcollector. When establishing the connection of the exhaust system, the CBUSH is used instead of the corrugated pipe. The internal pipe structure should be drawn out because its weight has a great influence on the modal of the exhaust system. The front and rear suspension strut assemblies are replaced by Bar units instead of springs. The hydraulic cylinder sleeve top is connected with the pull rod by rbe2 and releases the freedom of axial translation. The sleeve inside the pull rod lower end is connected with the sleeve and the pull rod by cbush. The tire mass is placed on the RBE2 coupling point of the rotating part and the other half is placed on the tire outer contour node, releasing the RBE2 connection between the rotating part and the fixed part.

[0057] Furthermore, the sound cavity model is established. The structural noise in the vehicle is caused by the vibration of the body panel, and then it is radiated to the vehicle interior through the sound cavity. The sound cavity is a closed cavity wrapped by its cover. In the interior body model, the finite element model of the vehicle interior in contact with the air is extracted. Without affecting the characteristics, the holes of the sound cavity finite element model are filled, and the geometric surface is generated by the finite element grid. After the geometric surface is generated, the relevant feature lines are created to ensure that the adjacent two surfaces are inclined at about 30 to 60 degrees, and the redundant surfaces are deleted. The remaining geometric surfaces are meshed, the adjacent surface grids are connected, and finally the sound cavity surface grid is generated. The seat surface grid and the sound cavity surface grid are imported to form a closed body, and then the body grid is divided to obtain the required sound cavity body grid. When dividing the sound cavity body grid, the size of the structure and the sound cavity coupling unit should be consistent, and at the same time, the sound cavity unit should have at least 6 units within a wavelength. According to the above rules, the sound cavity grid is established in the pre-processing software, and the corresponding air material properties are assigned.

[0058] The last step is to assemble the above interior body model, chassis model, sound cavity model and power assembly model into a whole vehicle NVH model, which covers all related subsystem models on the transmission path from the power assembly excitation source to the steering wheel and the right ear of the driver, as shown in Figure 2

[0059] The method for whole vehicle modal analysis is:

[0060] ​Modal is the inherent property of the structure, through modal analysis can obtain the inherent frequency, modal shape and damping ratio parameters. The modal parameters of the structure reflect the dynamic characteristics of the structure. According to the dynamic equation, if the system damping and excitation are not considered, the vibration differential equation of the system can be expressed as:

[0061]

[0062] Let the solution be Q=sin(ωt+φ), solve the differential equation:

[0063] M -1 Kx=ω 2 x

[0064] Where M is the mass matrix, K is the stiffness matrix, ω is the inherent angular frequency of the vehicle model, and the inherent frequency f of the system can be obtained from the formula f=ω / 2π. Each ω eigenvalue corresponds to a characteristic vector x, that is, the mode shape of the vehicle model.

[0065] With the continuous development of computers, finite element technology has also developed rapidly. In the early stage of automobile development, try to use finite element technology to reduce product testing, which can effectively control product development cost and development cycle. In order to intuitively judge the modal frequency avoidance of the whole vehicle, the modal of the whole vehicle is calculated through Nastran analysis software, and the boundary conditions are unconstrained, no need to apply load, and the frequency and mode shape of the typical modal of the whole vehicle body, the whole vehicle engine compartment, the front beam of the roof, the floor, the back door, the front seat, the exhaust system, the steering system, the powertrain, the front and rear suspension, the acoustic cavity and other subsystems are calculated. 0-50Hz.

[0066] S2: Obtain the excitation frequency range corresponding to each subsystem and powertrain of the whole vehicle under the condition of idling speed through the engine idling charging speed range.

[0067] S3: Based on S1 and S2, judge whether the modal of the whole vehicle can avoid the idling charging excitation frequency, if not, enter S4;

[0068] The modal frequency avoidance principle of the whole vehicle in this embodiment: the idling charging excitation frequency range needs to avoid the typical modal of the whole vehicle body, the whole vehicle engine compartment, the front beam of the roof, the floor, the back door, the front seat, the exhaust system, the steering system, the powertrain, the front and rear suspension, the battery pack, the acoustic cavity and other subsystems in the range of 3Hz above and below; if the modal of the whole vehicle cannot avoid the idling charging excitation frequency, it needs to be evaluated in combination with the whole vehicle NVH analysis result under the idling charging speed. In this embodiment, the modal frequency avoidance conclusion of the whole vehicle is as follows:

[0069] The adjustable range of idling charging speed is 1000-1500rpm, and the corresponding excitation frequency range is 33Hz-50Hz;

[0070] Typical modal of the whole vehicle: first order bending mode 28Hz, first order torsion mode 23.9Hz;

[0071] Typical modal of the engine compartment: first order yaw mode 23.3Hz, first order pitch mode 21.7Hz;

[0072] Typical modal of the front roof cross beam: first order bending mode 49.6Hz;

[0073] Typical modal of the floor: first order bending mode of the front floor 28.2Hz;

[0074] Typical modal of the back door: first order bending mode 21.7Hz;

[0075] Typical modal of the front seats: first order lateral mode 15.2Hz, first order longitudinal mode 15.7Hz;

[0076] Typical modal of the exhaust system: first order lateral bending mode 15.0Hz, first order vertical bending mode 11.9Hz;

[0077] Typical modal of the steering system: first order yaw mode 38.4Hz, first order pitch mode 40.5Hz;

[0078] Typical modal of the powertrain: three directions of translation and rotation, respectively, front-back translation 9.3Hz, left-right translation 5.4Hz, up-down translation 9.8Hz, longitudinal rotation 14.7Hz, lateral rotation 11.2Hz and vertical rotation 12.4Hz;

[0079] Typical modal of the front and rear suspension: vertical synchronous 13.8Hz, vertical asynchronous 14.7Hz, front-back synchronous 16.7Hz and front-back asynchronous 16.7Hz;

[0080] According to the above whole vehicle modal results and excitation frequency range, the steering system modal and the front roof cross beam modal do not meet the frequency avoidance principle, there is a risk of steering wheel vibration and driver right ear noise, which needs to be evaluated in combination with the whole vehicle NVH analysis results, and the modal of other subsystems meets the frequency avoidance principle.

[0081] S4: Obtain cylinder pressure excitation under different idle charging speeds, and perform whole vehicle NVH performance analysis to obtain vibration speed at the steering wheel and noise sound pressure at the driver's right ear under different idle charging speed conditions.

[0082] The method for obtaining the in-cylinder pressure under different loads and speeds in the idle condition is as follows:

[0083] The idle charging speed adjustable range in this embodiment is assumed to be 1000-1500rpm, and one speed point is taken every 50rpm, so 11 groups of idle charging speeds can be obtained;

[0084] The specific operation process is that after the engine bench test arrangement is completed, different loads are controlled by changing the crank reverse drag torque, different speeds are controlled by adjusting the throttle opening, and after the speed is stable, the pressure data of one cycle in the cylinder is tested.

[0085] The time domain curves of cylinder pressure, speed and crank angle are converted into cylinder pressure excitation files available for NASTRAN, which are used as excitation required for idling charging condition analysis.

[0086] The process is as follows,

[0087] 1. For a certain load condition, the crank angle and cylinder pressure relationship curves at each speed of the engine are extracted from the original test data by adjusting the throttle opening, such as 1000 rpm, 1050 rpm and 1100 rpm.

[0088] 2. The above curves at different speeds under the same load are summarized to synthesize the cylinder pressure-crank angle-engine speed relationship curve, i.e. the cylinder pressure excitation file.

[0089] 3. For different load conditions, repeat the above work, and finally obtain the cylinder pressure-crank angle-engine speed relationship curve under different loads and different speeds.

[0090] S4: Obtain cylinder pressure excitation under different idling charging speeds, perform vehicle NVH performance analysis, and obtain the response peak values of vibration speed at the steering wheel and noise sound pressure at the right ear of the driver under different idling charging speed conditions. The method for obtaining cylinder pressure excitation under different idling charging speeds is:

[0091] 1. Using engine cylinder pressure data and engine basic parameters, calculate the time domain curves of engine excitation in one cycle through the engine MBD model of combustion force, inertia force and unbalanced force;

[0092] The inertia force calculation model is:

[0093] ∑F ι2 =-M rec λrω 2 [cos2θ+cos2(θ+180°)+cos2(θ+180°)+cos2θ]=-4M rec λrω 2 cos2θ;

[0094] Wherein, F t2 is the secondary reciprocating inertia force, Mrec represents the sum of piston mass and 1 / 3 connecting rod mass, λ represents the ratio of half crank length to connecting rod length, ω represents engine speed, θ is the current crank rotation angle, and r represents half crank length.

[0095] The inertia torque calculation model is:

[0096] ∑T i =2M rec r 2 ω 2 sin2θ;

[0097] Among them, T i The engine's inertial torque is represented by Mrec, the sum of the piston mass and 1 / 3 of the connecting rod mass is represented by r, half the crankshaft length is represented by ω, the engine speed is represented by θ, and the crankshaft rotation angle is represented by θ at the current moment.

[0098] The gas torque calculation model is as follows:

[0099]

[0100]

[0101] Among them, T g The engine gas torque is represented by Fg, the gas pressure on the piston is represented by r, half the crankshaft length is represented by θ, the crankshaft rotation angle at the current moment is represented by λ, the ratio of half the crankshaft length to the connecting rod length is represented by Pg, the engine test cylinder pressure is represented by D, and the piston diameter is represented by D.

[0102] 2. Combining the engine excitation time-domain results, the time-domain excitation is converted into the frequency-domain excitation through fast Fourier transform, and then the excitation frequency amplitude and phase corresponding to the relevant order are extracted to complete the conversion of time-domain load to frequency-domain load;

[0103] At this point, the cylinder pressure test and processing are complete. The cylinder pressure has been processed into the engine crankshaft center position input, as shown below. Figure 2 The load force and load torque are shown in the six directions.

[0104] The vibration generated by the powertrain under excitation will be transmitted to the vehicle body through the suspension and other paths, which will cause the vehicle body to vibrate, and then transmit to the steering wheel and the driver's right ear, generating vibration and noise response. The vibration transmission path formula is as follows;

[0105]

[0106] Among them, y k (ω) represents the total response at target point k inside the vehicle, n represents the total number of transmission paths, ω represents the corresponding frequency, and F ik (ω) and Q jk (ω) represent the structural excitation and acoustic excitation at the excitation end, respectively, H ik (ω) and H jk (ω) represents the vibration transfer function and noise transfer function from the excitation point to the response point, respectively.

[0107] Load the 11 groups of idle charging speed condition cylinder pressure excitation to the whole vehicle NVH model; the process is calculated by software, and finally the response peak values of the vibration speed at the steering wheel and the noise sound pressure at the right ear of the driver under different idle charging speed conditions are obtained.

[0108] S5: Determine the engine speed of the idle charging condition based on the steering wheel vibration speed and the noise sound pressure at the right ear of the driver. That is, the method for selecting the optimal engine speed based on the steering wheel vibration and the noise sound pressure at the right ear of the driver is:

[0109] ① If the steering wheel vibration speed and the noise sound pressure at the right ear of the driver both meet the performance target requirements, select the engine speed corresponding to the minimum steering wheel vibration to run;

[0110] ② If one of the steering wheel vibration speed and the noise sound pressure at the right ear of the driver meets the performance target, and the other does not meet the performance target, determine the optimal engine speed based on the fuel consumption economy or the cost of optimizing the item that does not meet the performance target;

[0111] ③ If the steering wheel vibration speed and the noise sound pressure at the right ear of the driver both do not meet the performance target requirements, select the engine speed corresponding to the minimum steering wheel vibration to run.

[0112] Since the steering wheel vibration speed and the noise sound pressure at the right ear of the driver change with the speed, in order to maximize the consideration of human subjective feeling, in this embodiment, when considering the steering wheel vibration speed and the noise at the right ear of the driver, the response peak value of the steering wheel vibration speed and the response peak value of the noise sound pressure at the right ear of the driver are taken as the basis for judging the subjective feeling of the driver. That is, the method for selecting the optimal engine speed based on the steering wheel vibration and the noise sound pressure at the right ear of the driver is:

[0113] ① If the response peak value of the steering wheel vibration speed and the response peak value of the noise sound pressure at the right ear of the driver both meet the performance target requirements, select the engine speed corresponding to the minimum steering wheel vibration to run;

[0114] ② If one of the response peak value of the steering wheel vibration speed and the response peak value of the noise sound pressure at the right ear of the driver meets the performance target, and the other does not meet the performance target, determine the optimal engine speed based on the fuel consumption economy or the cost of optimizing the item that does not meet the performance target;

[0115] ③ If the response peak value of the steering wheel vibration speed and the response peak value of the noise sound pressure at the right ear of the driver both do not meet the performance target requirements, select the engine speed corresponding to the minimum steering wheel vibration to run.

[0116] In this embodiment, 1000-1500 rpm whole vehicle idle speed sweep frequency analysis is completed, and the 12-point xyz three-direction velocity RSS value of the steering wheel and the sound pressure value of the right ear of the driver are obtained, as shown in Figure 3 and Figure 4 The noise of the right ear of the driver meets the performance target at 1000-1250 rpm and does not meet the performance target at 1300-1500 rpm; the steering wheel vibration does not meet the performance target at 1000-1500 rpm, of which 1050-1200 rpm is relatively good. Therefore, considering the results of the noise of the right ear of the driver and the steering wheel vibration, it can be known that the whole vehicle NVH performance is better at 1050-1200 rpm.

[0117] According to the whole vehicle NVH performance rectification strategy of the idle charging working condition, the optimal idle speed is locked;

[0118] According to the classification and sorting of the whole vehicle NVH response results at the idle charging speeds of the above 11 groups, the steering wheel vibration does not meet the performance target at 1050-1200 rpm, and the noise of the right ear of the driver meets the performance target; based on the idle charging speed control strategy, the whole vehicle response result at the idle speed of 1050-1200 rpm belongs to the second type, and the cost and price of optimizing the performance unqualified items need to be compared, and the optimal idle speed is locked;

[0119] The fuel economy performance of the engine is better at 1200-1400 rpm; therefore, it is suggested that the idle speed be set at 1200 rpm. In view of the fact that the steering wheel vibration of 1.77 mm / s exceeds the standard (target ≤1.0 mm / s), the main reason is that the steering system mode is 40 Hz, which is coupled with the idle charging speed of 1200 rpm to cause resonance; therefore, the optimization scheme can start from adjusting the steering system mode to avoid the engine speed; scheme one is to add a 0.5 kg vibration absorber to the steering wheel, and the vibration is reduced to 0.63 mm / s, meeting the performance target; scheme two is to optimize the body structure, and the vibration is reduced to 1.0 mm / s by strengthening the CCB structure, left and right suspension supports, and finger beam structure, meeting the performance target;

[0120] The whole vehicle NVH level of the hybrid vehicle under each idle charging working condition is obtained through the early stage of the project development, and the cost and rectification strategy are considered; it is suggested that the idle charging speed control of the hybrid vehicle be controlled at 1200 rpm; and the simulation means is used to rectify the steering wheel vibration unqualified item at 1200 rpm, and two sets of optimization schemes are provided before the project whole vehicle data is frozen, which effectively reduces the rectification of related problems in the later stage, saves the project development time, and reduces the development cost.

[0121] Embodiment 2

[0122] An idle charging speed control system is provided in this embodiment, which is based on the method provided in embodiment 1, as shown inFigure 5 as shown.

[0123] The finite element module 1 is configured to establish a whole vehicle NVH finite element simulation model and perform whole vehicle modal analysis.

[0124] The whole vehicle modal frequency avoidance judgment module 2 is configured to obtain the excitation frequency ranges of each subsystem and the power assembly of the whole vehicle under the idle condition through the engine idle charging speed range, and compare the whole vehicle modal to judge whether the whole vehicle each subsystem and the power assembly can realize frequency avoidance.

[0125] The noise acquisition module 3 is configured to obtain the cylinder pressure excitation under different idle charging speeds, perform whole vehicle NVH performance analysis, and obtain the response peak values of the steering wheel vibration speed and the noise sound pressure at the right ear of the driver under different idle charging speed conditions.

[0126] The whole vehicle NVH performance rectification strategy selection module 4 is configured to determine the idle charging condition whole vehicle NVH performance rectification strategy based on the response peak values of the steering wheel vibration speed and the noise sound pressure at the right ear of the driver under different idle charging speed conditions.

[0127] The idle charging condition whole vehicle NVH performance rectification strategy is:

[0128] ① If the steering wheel vibration speed and the noise sound pressure at the right ear of the driver both meet the performance target requirements, the engine speed corresponding to the minimum steering wheel vibration is selected for operation.

[0129] ② If one of the steering wheel vibration speed and the noise sound pressure at the right ear of the driver meets the performance target, and the other does not meet the performance target, the optimal engine speed is determined based on the fuel consumption economy or the cost of optimizing the performance target.

[0130] ③ If the steering wheel vibration speed and the noise sound pressure at the right ear of the driver both do not meet the performance target requirements, the engine speed corresponding to the minimum steering wheel vibration is selected for operation.

[0131] The above embodiments are only preferred embodiments for fully illustrating the present application, and the protection scope of the present application is not limited thereto. Any equivalent replacement or transformation of the present application based on the present application is within the protection scope of the present application.

Claims

1. A method of determining engine speed during an idle charge operating condition, the method comprising: The method is specifically: ​ S1: Establish a whole vehicle NVH finite element simulation model, and perform whole vehicle modal analysis; S2: Obtain the excitation frequency range of each subsystem and power assembly of the whole vehicle through the engine speed range under the idling charging working condition; S3: Based on S1 and S2, determine whether the whole vehicle mode can avoid the excitation frequency of each subsystem and power assembly of the whole vehicle, if yes, end, if not, enter S4; S4: Obtain the cylinder pressure excitation of the engine under different speeds under the idling charging working condition, perform whole vehicle NVH performance analysis, and obtain the response peak values of the vibration speed at the steering wheel and the noise sound pressure at the right ear of the driver under different speeds; S5: Based on the response peak values of the vibration speed at the steering wheel and the noise sound pressure at the right ear of the driver, determine the optimal engine idling speed of the idling charging working condition.

2. The determination method of claim 1, wherein: The S5 is specifically: ① If the steering wheel vibration and the noise at the right ear of the driver both meet the performance target requirements, select the engine speed corresponding to the minimum steering wheel vibration to run; ② If one of the response peak values of the steering wheel vibration or the response peak values of the noise sound pressure at the right ear of the driver meets the performance target, and the other does not meet the performance target, determine the optimal engine speed based on the fuel consumption economy or the cost of optimizing the item that does not meet the performance target; ③ If the steering wheel vibration and the noise at the right ear of the driver both do not meet the performance target requirements, select the engine speed corresponding to the minimum steering wheel vibration to run.

3. The determination method of claim 1, wherein: The method for obtaining the cylinder pressure excitation of the engine under different speeds under the idling charging working condition in S4 is: Obtain the in-cylinder pressure under different loads and different speeds under the idling working condition, and obtain the time domain excitation of the engine based on the cylinder pressure data and the basic parameters of the engine, then convert the time domain excitation into frequency domain excitation, and further obtain the cylinder pressure excitation under different idling charging speeds.

4. The determination method according to claim 3, characterized in that: The method for obtaining the in-cylinder pressure under different loads and different speeds under the idling working condition is: For a certain load working condition, adjust the throttle opening, extract the angle-cylinder pressure relationship curve of the engine under each speed from the original test data; Summarize the angle-cylinder pressure relationship curve of the engine under each speed under the same load and different speeds, and synthesize the cylinder pressure-crank angle-engine speed relationship curve; Change the load working condition, repeat the steps of obtaining the cylinder pressure-crank angle-engine speed relationship curve, and finally obtain the cylinder pressure-crank angle-engine speed relationship curve under different loads and different speeds.

5. The determination method according to claim 3, characterized in that: The method for obtaining the time domain excitation of the engine based on the cylinder pressure data and the basic parameters of the engine, and then converting the time domain excitation into frequency domain excitation is specifically: using the engine cylinder pressure data and the basic parameters of the engine, calculating the combustion force, inertial force and unbalanced force in a period through the engine MBD model to obtain the engine excitation time domain curve; combining the engine excitation time domain result, converting the time domain excitation into frequency domain excitation through fast Fourier transform, then extracting the excitation frequency amplitude and phase corresponding to the relevant order, and completing the conversion of the time domain load to the frequency domain load.

6. The determination method of claim 4, wherein: The method for obtaining the analysis model for performing the whole vehicle NVH performance analysis in the S4 is specifically: loading the cylinder pressure excitation under different idle charging rotating speeds as input excitation to the whole vehicle NVH finite element simulation model.

7. An idle charging operating speed determination system based on the determination method according to any one of claims 1 to 6, characterized by: The whole vehicle NVH performance analysis system comprises a finite element module configured to establish a whole vehicle NVH finite element simulation model and perform whole vehicle modal analysis; The whole vehicle modal frequency avoidance judgment module obtains the excitation frequency ranges of each subsystem and the power assembly of the whole vehicle through the engine rotating speed range under the idle charging working condition, and compares the whole vehicle modal with the excitation frequency ranges to determine whether the whole vehicle modal can avoid the excitation frequency of each subsystem and the power assembly of the whole vehicle; The noise obtaining module is configured to obtain the cylinder pressure excitation of the engine under different rotating speeds under the idle charging working condition, perform whole vehicle NVH performance analysis, and obtain the response peak values of the steering wheel vibration speed and the noise sound pressure at the right ear of the driver under different rotating speeds; The whole vehicle NVH performance rectification strategy selection module is configured to determine the engine rotating speed under the idle charging working condition based on the response peak values of the steering wheel vibration speed and the noise sound pressure at the right ear of the driver.

8. The system of claim 7, wherein: The method for determining the engine rotating speed in the whole vehicle NVH performance rectification strategy selection module is specifically: ① if both the steering wheel vibration and the noise at the right ear of the driver meet the performance target requirements, the idle rotating speed corresponding to the minimum steering wheel vibration is selected; ② if one of the response peak value of the steering wheel vibration or the response peak value of the noise sound pressure at the right ear of the driver meets the performance target, and the other does not meet the performance target, the optimal idle rotating speed is determined based on the fuel consumption economy or the cost of optimizing the item that does not meet the performance target; ③ if both the steering wheel vibration and the noise at the right ear of the driver do not meet the performance target requirements, the idle rotating speed corresponding to the minimum steering wheel vibration is selected.

9. The system of claim 7, wherein: The method for obtaining the cylinder pressure excitation of the engine under different rotating speeds under the idle charging working condition by the noise obtaining module is: The in-cylinder pressure under different loads and different rotating speeds under the idle working condition is obtained, and the time domain excitation of the engine is obtained based on the cylinder pressure data and the basic parameters of the engine, and then the time domain excitation is converted into frequency domain excitation, and the cylinder pressure excitation under different idle charging rotating speeds is obtained.

10. The system of claim 9, wherein: The method for obtaining the in-cylinder pressure under different loads and different rotating speeds under the idle working condition by the noise obtaining module is: For a certain load working condition, the relationship curves of the crank angle and the cylinder pressure under each rotating speed of the engine are extracted from the original test data by adjusting the throttle opening degree; The relationship curves of the cylinder pressure, the crank angle and the engine rotating speed under different loads and different rotating speeds are obtained by repeating the above steps. The relationship curves of the cylinder pressure, the crank angle and the engine rotating speed under different loads and different rotating speeds are obtained by repeating the above steps.

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