CN109342073A - Acquisition methods, device and the realization device of road excitation load - Google Patents
Acquisition methods, device and the realization device of road excitation load Download PDFInfo
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Abstract
The present invention provides acquisition methods, device and the realization devices of a kind of road excitation load；Wherein, this method is applied in the NVH performance evaluation of vehicle；This method comprises: obtaining the parameter on road surface；Parameter includes pavement grade and frequency separation to be analyzed；According to pavement grade, the corresponding power spectral density function in road surface is chosen；According to frequency range to be analyzed and power spectral density function, road excitation load is obtained；Road excitation load includes road roughness frequency domain spectra.Present invention reduces the complexities of the cost and acquisition methods that obtain road excitation load.
Description
Technical Field
The invention relates to the technical field of road vibration noise analysis, in particular to a method and a device for acquiring a road excitation load and a device for realizing the method.
Background
The road excitation load can be used as an input parameter for the simulation analysis of road Vibration Noise and the performance development of NVH (Noise, Vibration, Harshness, Noise, Vibration and Harshness) of the automobile; the frequency domain spectrum of the road surface unevenness can be used as an expression mode of road surface excitation load. In a reliability test of a vehicle, a sextant can be adopted to detect the wheel center force applied to the vehicle, and the wheel center force is taken as a road surface excitation load; the excitation frequency of the road excitation load which can be obtained in the method can reach about 40Hz at most, and the upper limit of the load frequency required in the road noise analysis and NVH performance development is higher (usually about 200 Hz), so that the road excitation load in the road noise analysis and NVH performance development cannot be obtained by using a sextant.
At present, the method for acquiring the road excitation load applied to road noise analysis and NVH performance development mainly comprises a direct method and an inverse matrix method; the direct method is to directly measure the unevenness (vertical displacement) of the actual road surface as the excitation load, however, the direct method directly scans the unevenness of the road surface by means of laser detection equipment and the like, special test road surfaces and data acquisition equipment are needed, the cost is high, and the time consumption is long; the inverse matrix method is to measure the vibration response of the suspension when the vehicle runs on the road surface, and inversely calculate the road surface load by using the inverse matrix method in combination with the vibration transfer function from the road surface to the response point; however, the method needs a fixed test road surface and a fixed sample vehicle, and cannot be performed in the early stage of vehicle development (stage without sample vehicle), so that the road vibration noise NVH simulation analysis optimization and performance risk control cannot be performed in the early stage of development, and each system such as quality, progress, cost and the like may pay a large cost in the sample vehicle training stage, thereby greatly increasing the research and development cost and developing risk, and causing low research and development efficiency.
Disclosure of Invention
In view of the above, the present invention provides a method, an apparatus and a device for acquiring a road excitation load, so as to reduce the cost of acquiring a frequency domain spectrum of road unevenness and the complexity of the acquiring method.
In a first aspect, an embodiment of the present invention provides a method for acquiring a road excitation load, where the method is applied to NVH performance analysis of a vehicle; the method comprises the following steps: acquiring parameters of a road surface; the parameters comprise road surface grade and a frequency interval to be analyzed; selecting a power spectral density function corresponding to the road surface according to the grade of the road surface; acquiring a road surface excitation load according to a frequency interval to be analyzed and a power spectral density function; the road excitation load comprises a road unevenness frequency domain spectrum.
With reference to the first aspect, an embodiment of the present invention provides a first possible implementation manner of the first aspect, where the step of obtaining the road excitation load according to the frequency interval to be analyzed and the power spectral density function includes: generating a road surface unevenness time domain spectrum of the road surface according to the frequency interval to be analyzed and the power spectral density function; and carrying out Fourier transform on the road surface unevenness time domain spectrum to obtain a road surface unevenness frequency domain spectrum.
With reference to the first possible implementation manner of the first aspect, an embodiment of the present invention provides a second possible implementation manner of the first aspect, where the step of generating a road surface irregularity time domain spectrum of a road surface according to a frequency interval to be analyzed and a power spectral density function includes: dividing the frequency interval to be analyzed into a set number of sub-frequency intervals, and calculating the unevenness variance of the road surface by the following formula:
wherein,the unevenness variance of the road surface in the kth sub-frequency interval is taken as (k is 1,2,3, m, m is a set number); f. ofmid_kIs the center frequency of the kth sub-frequency interval; gq(fmid_k) Corresponding to the central frequency of the k-th sub-frequency interval in the power spectral density function corresponding to the road surface gradeFunction values; Δ fkThe interval length of the kth sub-frequency interval; and generating a road surface unevenness time domain spectrum according to the road surface unevenness variance and the statistical characteristics of the road surface unevenness.
With reference to the second possible implementation manner of the first aspect, an embodiment of the present invention provides a third possible implementation manner of the first aspect, where the step of generating a road surface irregularity time domain spectrum according to the road surface irregularity variance and the statistical characteristics of the road surface irregularity includes: generating a random number for each sub-frequency interval; the value interval of the random number is [0, 2 pi ]; according to the statistical theory, the time domain spectrum of the unevenness of each sub-frequency interval is expressed as a cosine wave function shown in the following formula:
wherein σkIs the standard deviation of the unevenness of the road surface in the kth sub-frequency intervalkA random number of the kth sub-frequency interval; and generating a road surface unevenness time domain spectrum by using the unevenness time domain spectrum of the sub-frequency interval according to a harmonic superposition algorithm.
With reference to the third possible implementation manner of the first aspect, an embodiment of the present invention provides a fourth possible implementation manner of the first aspect, where the step of generating the road surface unevenness time domain spectrum by using the unevenness time domain spectrum of the sub-frequency intervals according to the harmonic superposition algorithm includes: superposing cosine wave functions of the unevenness time domain spectrums representing the sub-frequency intervals, and determining the road surface unevenness time domain spectrums by the following formula:
wherein q (t) is a road surface unevenness time domain spectrum.
In a second aspect, an embodiment of the present invention further provides an apparatus for acquiring a road excitation load, where the apparatus is applied to NVH performance analysis of a vehicle; the device includes: the parameter acquisition module is used for acquiring the parameters of the road surface; the parameters comprise road surface grade and a frequency interval to be analyzed; the function selection module is used for selecting a power spectral density function corresponding to the road surface according to the road surface grade; the road surface excitation load acquisition module is used for acquiring a road surface excitation load according to the frequency interval to be analyzed and the power spectral density function; the road excitation load comprises a road unevenness frequency domain spectrum.
With reference to the second aspect, an embodiment of the present invention provides a first possible implementation manner of the second aspect, where the road surface excitation load module is further configured to: generating a road surface unevenness time domain spectrum of the road surface according to the frequency interval to be analyzed and the power spectral density function; and carrying out Fourier transform on the road surface unevenness time domain spectrum to obtain a road surface unevenness frequency domain spectrum.
With reference to the first possible implementation manner of the second aspect, the embodiment of the present invention provides a second possible implementation manner of the second aspect, wherein the road surface excitation load module is further configured to: dividing the frequency interval to be analyzed into a set number of sub-frequency intervals, and calculating the unevenness variance of the road surface by the following formula:
wherein,the unevenness variance of the road surface in the kth sub-frequency interval is taken as (k is 1,2,3, m, m is a set number); f. ofmid_kIs the center frequency of the kth sub-frequency interval; gq(fmid_k) The function value corresponding to the central frequency of the kth sub-frequency interval in the power spectral density function corresponding to the pavement grade is obtained; Δ fkThe interval length of the kth sub-frequency interval; and generating a road surface unevenness time domain spectrum according to the road surface unevenness variance and the statistical characteristics of the road surface unevenness.
With reference to the second possible implementation manner of the second aspect, the embodiment of the present invention provides a third possible implementation manner of the second aspect, wherein the road surface excitation load module is further configured to: generating a random number for each sub-frequency interval; the value interval of the random number is [0, 2 pi ]; according to the statistical theory, the time domain spectrum of the unevenness of each sub-frequency interval is expressed as a cosine wave function shown in the following formula:
wherein σkIs the standard deviation of the unevenness of the road surface in the kth sub-frequency intervalkA random number of the kth sub-frequency interval; and generating a road surface unevenness time domain spectrum by using the unevenness time domain spectrum of the sub-frequency interval according to a harmonic superposition algorithm.
In a third aspect, an embodiment of the present invention further provides an apparatus for obtaining a road surface excitation load, including a memory and a processor, where the memory is used to store one or more computer instructions, and the one or more computer instructions are executed by the processor to implement the above method for obtaining a road surface excitation load.
The embodiment of the invention has the following beneficial effects:
the embodiment of the invention provides a method and a device for acquiring a road excitation load and a device for realizing the same; after the parameters of the road surface are obtained, selecting a power spectral density function corresponding to the road surface according to the grade of the road surface; acquiring a pavement excitation load according to the frequency interval to be analyzed and the power spectral density function; the method reduces the cost of acquiring the road surface excitation load and the complexity of the acquiring method.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the invention as set forth above.
In order to make the aforementioned and other objects, features and advantages of the present invention comprehensible, preferred embodiments accompanied with figures are described in detail below.
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In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
Fig. 1 is a flowchart of a method for acquiring a road excitation load according to an embodiment of the present invention;
FIG. 2 is a power spectral density map of road surface irregularities according to an embodiment of the present invention;
FIG. 3 is a plot of power spectral density obtained by smoothing and curve fitting according to an embodiment of the present invention;
fig. 4 is a schematic diagram illustrating a principle of a national standard-based graded pavement reconstruction method according to an embodiment of the present invention;
fig. 5 is a schematic structural diagram of a device for acquiring a road excitation load according to an embodiment of the present invention;
fig. 6 is a schematic structural diagram of a device for acquiring a road excitation load according to an embodiment of the present invention.
Detailed Description
To make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings, and it is apparent that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
At present, the existing road excitation load acquisition mode is complex, the cost is high, and based on this, the embodiment of the invention provides a road excitation load acquisition method, a road excitation load acquisition device and a road excitation load realization device, which can be applied to the fields of road vibration noise simulation analysis, NVH performance development and the like.
For the convenience of understanding the present embodiment, a method for acquiring a road excitation load disclosed in the present embodiment will be described in detail first.
Referring to a flow chart of a method for acquiring a road excitation load shown in fig. 1, the method comprises the following steps:
s100, acquiring road surface parameters; the parameters include road surface grade and frequency interval to be analyzed.
The parameters can be input by engineering technicians; the road surface grade can be specified by national standards, such as national standard (GB/T7031-; the road surface excitation load has a certain frequency range, and if the road surface excitation load in a certain frequency interval is to be acquired, a corresponding frequency interval to be analyzed needs to be determined.
And S102, selecting a power spectral density function corresponding to the road surface according to the road surface grade.
The power spectral density function corresponds to the grade of the road surface; the two can be road surface grade and corresponding power spectrum function given by the national standard (GB/T7031-.
Step S104, acquiring a road surface excitation load according to the frequency interval to be analyzed and the power spectral density function; the road excitation load comprises a road unevenness frequency domain spectrum.
The step S104 may be specifically implemented by the following steps:
(1) generating a road surface unevenness time domain spectrum of the road surface according to the frequency interval to be analyzed and the power spectral density function;
specifically, firstly, a frequency interval to be analyzed is divided into a set number of sub-frequency intervals, and the unevenness variance of the road surface is calculated by the following formula:
wherein,the unevenness variance of the road surface in the kth sub-frequency interval is taken as (k is 1,2,3, m, m is a set number); f. ofmid_kIs the center frequency, G, of the kth sub-frequency intervalq(fmid_k) The function value corresponding to the central frequency of the kth sub-frequency interval in the power spectral density function corresponding to the pavement grade is obtained; Δ fkThe interval length of the kth sub-frequency interval;
secondly, generating a road surface unevenness time domain spectrum according to the road surface unevenness variance and the statistical characteristics of the road surface unevenness; because the road surface unevenness can be regarded as a random sample of probability distribution with known statistical parameters, a harmonic superposition method can be adopted to generate a road surface unevenness time domain spectrum, and the specific mode is as follows:
1. generating a random number for each sub-frequency interval; the random number is in the [0, 2 pi ] interval; in the prior art, there are many methods for generating random numbers, which are referred to as random number generators.
2. According to the statistical theory, the time domain spectrum of the unevenness of each sub-frequency interval is expressed as a cosine wave function shown in the following formula:
wherein σkIs the standard deviation of the unevenness of the road surface in the kth sub-frequency intervalkIs a random number of the k-th sub-frequency interval.
3. According to a harmonic superposition algorithm, generating a road surface unevenness time domain spectrum of a set road surface grade by using the unevenness time domain spectrum of the sub-frequency interval; specifically, cosine wave functions representing the unevenness time domain spectrums of the respective sub-frequency sections may be superimposed, and the road surface unevenness time domain spectrum for setting the road surface grade may be determined by the following formula:
wherein q (t) is a road surface unevenness time domain spectrum.
In addition to the harmonic superposition method described above, the road surface unevenness time domain spectrum of the set road surface level may be generated by using an integral unit white noise method, a filter shaping white noise method, an AR (Auto regression) model, an ARMA (Auto-regression and moving average) model, or the like.
(2) And carrying out Fourier transform on the road surface unevenness time domain spectrum to obtain a road surface unevenness frequency domain spectrum.
The embodiment of the invention provides a method for acquiring a road excitation load; after the parameters of the road surface are obtained, selecting a power spectral density function corresponding to the road surface according to the grade of the road surface; acquiring a pavement excitation load according to the frequency interval to be analyzed and the power spectral density function; the method reduces the cost for acquiring the road surface excitation load and the complexity of the acquiring method.
The embodiment of the invention also provides a national standard-based grade pavement reconstruction method; the method is realized on the basis of the method shown in FIG. 1, and the road surface grade and the power spectral density of the road surface unevenness provided in the mechanical vibration road surface spectral measurement data report (GB/T7031-; and reconstructing the road surface unevenness load according with the national standard by using a computer, and converting the road surface unevenness load into the road surface excitation load directly available for NVH simulation analysis. The method is a virtual road surface reconstructed according to the parameters of various levels of road surfaces provided in the national standard and a public and mature algorithm, and the road surface and a sample vehicle do not need to be actually tested, so that the method is extremely low in cost and short in time consumption, road vibration noise harv (noise, vibration and harshness) simulation analysis optimization and performance risk control work can be carried out in the early stage of vehicle development, the research and development period is shortened, the development risk is reduced, and the research and development cost is saved.
The actual measurement of the road surface unevenness shows that the road surface unevenness is a traversing Gaussian random field which is locally uniform and has zero mean value. This reflects the following features of the road surface unevenness:
(1) local uniformity: and may be considered uniform over a sufficiently short length to reflect a smooth transition of the road surface.
(2) Zero mean value: the probability of starting from volts is the same.
(3) Traversing: covering all frequencies.
(4) Gaussian random field: the field is a spatial concept, corresponding to a normal stochastic process in the time domain.
From the above characteristics, the mean value of the road surface unevenness is known (0) and the distribution form (normal or gaussian distribution) is known, so that the statistical characteristics can be determined only by acquiring the variance thereof, which can be uniquely determined by the power spectral density.
The national standard 'road surface spectrum measurement data report of mechanical vibration road' (GB/T7031-. The Power Spectral Density (PSD) of the road surface unevenness is well described in this standard.
The national standard indicates that the curve form of the power spectrum density of the road surface roughness under the double logarithmic coordinates is approximately an oblique line, and as shown in fig. 2, the power spectrum density curve of the road surface roughness measured by Xstad (place name) in belgium is shown; smoothing the curve and fitting the curve to obtain a power spectral density curve as shown in fig. 3, wherein rmsd is a displacement root mean square, and rmsv is a velocity root mean square in a general description of the curve; the road surface power spectral density can be expressed as the following fitting formula:
Gd(n)＝Gd(n0)(n/n0)-w
wherein: n is0For reference to spatial frequency, the value is 0.1, w is usually 2.0, and n is the spatial frequency
Gd(n0) The road surface is classified into eight grades A to H according to the difference of the fitting coefficients (the geometric mean value of the fitting coefficients), and the fitting coefficients of the road surfaces of all grades are shown in Table 1:
TABLE 1
From the above table, the power spectral density function is known for the standard grade pavement specified by the national standard (GB/T7031-. Therefore, for the standard grade pavement in the national standard, the statistical characteristics are uniquely determined by the power spectral density.
The statistical characteristics of the grade pavement are known, and a random sample meeting the statistical characteristics is generated, so that the grade pavement reconstruction is realized. There are many mathematical methods for generating a sample satisfying the statistical rule from the statistical characteristic parameters, and the embodiment of the invention completes the reconstruction of the road spectrum by using a more extensive and mature harmonic superposition method. Harmonic waveThe superposition algorithm can simulate a stationary random process, the main idea being to represent the road surface irregularity as a sum of a number of sine or cosine functions with random phases. The road spectrum is divided into a plurality of frequency intervals with small enough frequency in a required frequency interval, according to a statistical theory, in each small interval, the road spectrum can be expressed with the frequency as the central frequency of the interval, the phase is uniform and random, and the amplitude is the road surface unevenness standard deviation (variance square) corresponding to the central frequencyA multiplied cosine function; the cosine functions are superposed to obtain a standard grade road surface time domain spectrum, and according to the central limit theorem, when the divided frequency intervals are small enough, namely the number of the frequency intervals is enough, the frequency characteristic of the superposed road spectrum is consistent with the characteristic of the given national standard road surface spectrum. The time domain road spectrum can be converted into a frequency spectrum by fourier transform.
It is noted that the power spectral density fitting function in the national standard is the spatial frequency (in m)-1) If conversion to our usual time frequency (in Hz) is required, then multiplication by vehicle speed is required.
The schematic diagram of the method is shown in fig. 4, and mainly comprises the following steps:
(1) frequency interval (f) of road surface unevenness to be analyzed1，f2) Dividing into m small intervals, and calculating the variance of the unevenness of each small interval. Specifically, according to the selected road surface grade and frequency interval, the road surface unevenness variance can be expressed as the following formula:
wherein f is the time frequency, and the conversion formula of the time frequency and the space frequency is as follows:
f＝nv
in the above formula, v is the vehicle speed, n is the spatial frequency, and f is the temporal frequency.
The desired frequency interval (f)1，f2) Dividing into m cells, and taking the center frequency f of each cellmid_kSpectral density value G at (k ═ 1,2,... m)q(fmidk) In place of Gq(f) The spectral density values within the cell, then the above equation can be approximately written as:
wherein the variance of the unevenness between kth cells may be expressed as:
the standard deviation is:
(2) uniformly distributed random phases are generated. Specifically, a random number generation method is used for generating a group of random phases for m small frequency intervals in the previous step, and the phase corresponding to the k small interval is thetak，θkIs at [0, 2 π]The random numbers above satisfy uniform distribution, most computer languages have random number generation functions, and random arrays satisfying specified probability distribution, such as rand functions in Matlab, can be generated.
(3) And generating cosine waves of the unevenness of each small frequency interval, namely the road surface unevenness containing the amplitude and the phase. In particular, according to statistical theory, for each small interval, there is a frequency fmid_kAnd the standard deviation is sigmakThe cosine wave of (A) is:
(4) and (5) harmonic superposition to obtain a road surface unevenness spectrum in a time domain. Specifically, the cosine wave functions corresponding to the cells are superposed to obtain the time domain road surface random displacement input:
(5) and obtaining a frequency domain spectrum of the road surface unevenness by utilizing Fourier transform.
(6) And (3) performing subsequent processing, namely storing the frequency domain spectrum of the road unevenness into time domain data or frequency domain data format which can be directly used by CAE (computer aided Engineering) software according to NVH road noise analysis requirements.
(7) And programming software, packaging the processes and realizing one-click operation to obtain the required pavement.
In fact, the method for reconstructing a grade road surface based on the national standard provided by the embodiment of the invention is an inverse process of the process of smoothing the power spectrum density of the road surface unevenness and fitting a curve, and the method is used for obtaining the road surface excitation load which is in accordance with the actual road surface.
The method provided by the embodiment of the invention is based on the road surface data in the national standard (which is also an estimation standard) and a public and mature mathematical algorithm, and converts the power spectral density of the road surface with the national standard grade into the road surface excitation load required by the NVH road noise analysis which is actually available in the vehicle engineering; the method is different from the traditional means for acquiring the load by analyzing the NVH, the road surface excitation with the frequency of more than 200Hz for the NVH can be acquired without physically acquiring a self-built road surface or a rented test road surface, and the method is simple, reliable, practical and extremely low in cost.
The method does not depend on a sample vehicle, can carry out road noise analysis in a concept design stage, can greatly advance road noise development nodes, avoids risks early, saves time and reduces research and development cost; in the method, the complex calculation process and algorithm are transparent to engineers, directly available CAE data are generated in a one-click mode, the process is free of manual intervention, the use threshold is low, simplicity and high efficiency are achieved, and the error rate is low.
Corresponding to the above embodiments, the embodiment of the present invention further provides an apparatus for acquiring a road excitation load, and a schematic structural diagram of the apparatus is shown in fig. 5; the device includes: a parameter obtaining module 600, configured to obtain a parameter of a road surface; the parameters comprise road surface grade and a frequency interval to be analyzed; a function selecting module 602, configured to select a power spectral density function corresponding to a road surface according to a road surface grade; the road surface excitation load obtaining module 604 is used for obtaining the road surface excitation load according to the frequency interval to be analyzed and the power spectral density function; the road excitation load comprises a road unevenness frequency domain spectrum.
Further, the road surface excitation load module is further configured to: generating a road surface unevenness time domain spectrum of the road surface according to the frequency interval to be analyzed and the power spectral density function; and carrying out Fourier transform on the road surface unevenness time domain spectrum to obtain a road surface unevenness frequency domain spectrum.
Further, the road surface excitation load module is further configured to: dividing the frequency interval to be analyzed into a set number of sub-frequency intervals, and calculating the unevenness variance of the road surface by the following formula:
wherein,the unevenness variance of the road surface in the kth sub-frequency interval is taken as (k is 1,2,3, m, m is a set number); f. ofmid_kIs the center frequency of the kth sub-frequency interval; gq(fmid_k) The function value corresponding to the central frequency of the kth sub-frequency interval in the power spectral density function corresponding to the pavement grade is obtained; Δ fkThe interval length of the kth sub-frequency interval; according to the unevenness variance of the road surface andand generating a road surface unevenness time domain spectrum by the statistical characteristic of the road surface unevenness.
Further, the road surface excitation load module is further configured to: generating a random number for each sub-frequency interval; the value interval of the random number is [0, 2 pi ]; according to the statistical theory, the time domain spectrum of the unevenness of each sub-frequency interval is expressed as a cosine wave function shown in the following formula:
wherein σkIs the standard deviation of the unevenness of the road surface in the kth sub-frequency intervalkA random number of the kth sub-frequency interval; and generating a road surface unevenness time domain spectrum by using the unevenness time domain spectrum of the sub-frequency interval according to a harmonic superposition algorithm.
Further, the road surface excitation load module is further configured to: superposing cosine wave functions of the unevenness time domain spectrums representing the sub-frequency intervals, and determining the road surface unevenness time domain spectrums by the following formula:
wherein q (t) is a road surface unevenness time domain spectrum.
The device for acquiring the road surface excitation load provided by the embodiment of the invention has the same technical characteristics as the method for acquiring the road surface excitation load provided by the embodiment, so that the same technical problems can be solved, and the same technical effects can be achieved.
The embodiment provides a device for acquiring the road excitation load corresponding to the method embodiment. Fig. 6 is a schematic structural diagram of the implementation apparatus, and as shown in fig. 6, the apparatus includes a processor 1201 and a memory 1202; the memory 1202 is configured to store one or more computer instructions, and the one or more computer instructions are executed by the processor to implement the method for acquiring the road excitation load.
The implementation apparatus shown in fig. 6 further includes a bus 1203 and a forwarding chip 1204, and the processor 1201, the forwarding chip 1204 and the memory 1202 are connected through the bus 1203. The message transmission implementation device may be a network edge device.
The Memory 1202 may include a high-speed Random Access Memory (RAM) and may also include a non-volatile Memory (non-volatile Memory), such as at least one disk Memory. Bus 1203 may be an ISA bus, PCI bus, EISA bus, or the like. The bus may be divided into an address bus, a data bus, a control bus, etc. For ease of illustration, only one double-headed arrow is shown in FIG. 6, but that does not indicate only one bus or one type of bus.
The forwarding chip 1204 is configured to be connected to at least one user terminal and other network units through a network interface, and send the packaged IPv4 message or IPv6 message to the user terminal through the network interface.
The processor 1201 may be an integrated circuit chip having signal processing capabilities. In implementation, the steps of the above method may be implemented by integrated logic circuits of hardware or instructions in the form of software in the processor 1201. The Processor 1201 may be a general-purpose Processor, and includes a Central Processing Unit (CPU), a Network Processor (NP), and the like; the device can also be a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field-Programmable gate array (FPGA) or other Programmable logic device, a discrete gate or transistor logic device, or a discrete hardware component. The various methods, steps and logic blocks disclosed in the embodiments of the present invention may be implemented or performed. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like. The steps of the method disclosed in connection with the embodiments of the present invention may be directly implemented by a hardware decoding processor, or implemented by a combination of hardware and software modules in the decoding processor. The software module may be located in ram, flash memory, rom, prom, or eprom, registers, etc. storage media as is well known in the art. The storage medium is located in the memory 1202, and the processor 1201 reads information in the memory 1202 to complete the steps of the method of the foregoing embodiments in combination with hardware thereof.
The embodiment of the present invention further provides a machine-readable storage medium, where the machine-readable storage medium stores machine-executable instructions, and when the machine-executable instructions are called and executed by a processor, the machine-executable instructions cause the processor to implement the above method for acquiring a road surface excitation load.
The implementation principle and the generated technical effect of the device for acquiring the road excitation load and the implementation device provided by the embodiment of the invention are the same as those of the method embodiment, and for the sake of brief description, the corresponding content in the method embodiment can be referred to where the device embodiment is not mentioned in part.
In the several embodiments provided in the present application, it should be understood that the disclosed apparatus and method may be implemented in other manners. The apparatus embodiments described above are merely illustrative, and the flowcharts and block diagrams in the figures, for example, illustrate the architecture, functionality, and operation of possible implementations of apparatus, methods and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems which perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.
In addition, each functional module or unit in each embodiment of the present invention may be integrated together to form an independent part, or each module may exist alone, or two or more modules may be integrated to form an independent part.
The functions, if implemented in the form of software functional units and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present disclosure may be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present disclosure. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.
Finally, it should be noted that: the above-mentioned embodiments are merely specific embodiments of the present disclosure, which are used for illustrating the technical solutions of the present disclosure and not for limiting the same, and the scope of the present disclosure is not limited thereto, and although the present disclosure is described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: any person skilled in the art can modify or easily conceive of the technical solutions described in the foregoing embodiments or equivalent technical features thereof within the technical scope of the present disclosure; such modifications, changes or substitutions do not depart from the spirit and scope of the embodiments of the present disclosure, and should be construed as being included therein. Therefore, the protection scope of the present disclosure shall be subject to the protection scope of the claims.
Claims (10)
1. The method for acquiring the road excitation load is characterized by being applied to NVH performance analysis of a vehicle; the method comprises the following steps:
acquiring parameters of a road surface; the parameters comprise road surface grade and a frequency interval to be analyzed;
selecting a power spectral density function corresponding to the road surface according to the road surface grade;
acquiring a road surface excitation load according to the frequency interval to be analyzed and the power spectral density function; the road excitation load comprises a road unevenness frequency domain spectrum.
2. The method according to claim 1, wherein the step of obtaining the road surface excitation load according to the frequency interval to be analyzed and the power spectral density function comprises:
generating a road surface unevenness time domain spectrum of the road surface according to the frequency interval to be analyzed and the power spectral density function;
and carrying out Fourier transform on the road surface unevenness time domain spectrum to obtain the road surface unevenness frequency domain spectrum.
3. The method according to claim 2, wherein the step of generating a time domain spectrum of the road surface irregularity according to the frequency interval to be analyzed and the power spectral density function comprises:
dividing the frequency interval to be analyzed into a set number of sub-frequency intervals, and calculating the unevenness variance of the road surface in each sub-frequency interval by the following formula:
wherein,the unevenness variance of the road surface in the kth sub-frequency interval (k is 1,2,3 …, m, m is the set number); f. ofmid_kIs the center frequency of the kth sub-frequency interval; gq(fmid_k) The function value corresponding to the central frequency of the kth sub-frequency interval in the power spectral density function corresponding to the road surface grade is obtained; Δ fkThe interval length of the kth sub-frequency interval;
and generating the road surface unevenness time domain spectrum according to the road surface unevenness variance and the statistical characteristics of the road surface unevenness.
4. The method of claim 3, wherein the step of generating the time domain spectrum of road surface irregularities based on the variance of road surface irregularities and the statistical properties of road surface irregularities comprises:
generating a random number for each of the sub-frequency bins; the value interval of the random number is [0, 2 pi ];
according to a statistical theory, expressing the time domain spectrum of the unevenness of each sub-frequency interval as a cosine wave function shown by the following formula:
wherein σkIs the standard deviation of the unevenness of the road surface in the kth sub-frequency interval thetakA random number of the kth sub-frequency interval;
and generating the road surface unevenness time domain spectrum by using the unevenness time domain spectrum of the sub-frequency interval according to a harmonic superposition algorithm.
5. The method according to claim 4, wherein the step of generating the road surface irregularity time domain spectrum using the irregularity time domain spectrum of the sub-frequency intervals according to a harmonic superposition algorithm comprises:
superposing cosine wave functions of the unevenness time domain spectrums representing the sub-frequency intervals, and determining the road surface unevenness time domain spectrums by the following formula:
wherein q (t) is the road surface unevenness time domain spectrum.
6. The device for acquiring the road excitation load is characterized by being applied to NVH performance analysis of a vehicle; the device comprises:
the parameter acquisition module is used for acquiring the parameters of the road surface; the parameters comprise road surface grade and a frequency interval to be analyzed;
the function selection module is used for selecting a power spectral density function corresponding to the road surface according to the road surface grade;
the road surface excitation load obtaining module is used for obtaining a road surface excitation load according to the frequency interval to be analyzed and the power spectral density function; the road excitation load comprises a road unevenness frequency domain spectrum.
7. The apparatus of claim 6, wherein the road surface excitation load acquisition module is further configured to:
generating a road surface unevenness time domain spectrum of the road surface according to the frequency interval to be analyzed and the power spectral density function;
and carrying out Fourier transform on the road surface unevenness time domain spectrum to obtain the road surface unevenness frequency domain spectrum.
8. The apparatus of claim 7, wherein the road surface excitation load acquisition module is further configured to:
dividing the frequency interval to be analyzed into a set number of sub-frequency intervals, and calculating the unevenness variance of the road surface by the following formula:
wherein,the unevenness variance of the road surface in the kth sub-frequency interval (k is 1,2,3 …, m, m is the set number); f. ofmid_kIs the center frequency of the kth sub-frequency interval; gq(fmid_k) The function value corresponding to the central frequency of the kth sub-frequency interval in the power spectral density function corresponding to the road surface grade is obtained; Δ fkThe interval length of the kth sub-frequency interval;
and generating the road surface unevenness time domain spectrum according to the road surface unevenness variance and the statistical characteristics of the road surface unevenness.
9. The apparatus of claim 8, wherein the road surface excitation load acquisition module is further configured to:
generating a random number for each of the sub-frequency bins; the value interval of the random number is [0, 2 pi ];
according to a statistical theory, expressing the time domain spectrum of the unevenness of each sub-frequency interval as a cosine wave function shown by the following formula:
wherein σkIs the standard deviation of the unevenness of the road surface in the kth sub-frequency interval thetakA random number of the kth sub-frequency interval;
and generating the road surface unevenness time domain spectrum by using the unevenness time domain spectrum of the sub-frequency interval according to a harmonic superposition algorithm.
10. An apparatus for obtaining a road excitation load, comprising a memory and a processor, wherein the memory is configured to store one or more computer instructions, and the one or more computer instructions are executed by the processor to implement the method according to any one of claims 1 to 5.
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