CN115077690B - Method for evaluating periodic pulsation noise of internal combustion engine - Google Patents
Method for evaluating periodic pulsation noise of internal combustion engine Download PDFInfo
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Abstract
The invention discloses a periodic pulsation noise evaluation method of an internal combustion engine, which comprises the following steps: step 1, collecting noise signals and rotating speed signals; step 2, carrying out sectional filtering on the noise signals; step 3, performing Hilbert transform on the multi-section filtering signal; step 4, carrying out Fourier transform on each section of signal; step 5, calculating the modulation depth of signals of each frequency band; step 6: calculating the modulation depth of each order; and 7, calculating a periodic pulse index. The invention can accurately identify the periodic pulsation noise based on the auditory sense of the human ear and the periodic pulsation nature. The severity of the periodic pulsation noise can be judged by the evaluation method, and the main contribution frequency of the pulsation noise can be judged.
Description
Technical Field
The invention belongs to the technical field of engine NVH analysis and evaluation, and particularly relates to a periodic pulsation noise evaluation method of an internal combustion engine.
Background
For a reciprocating internal combustion engine, sounds like valve sounds, oil injection sounds and the like which periodically pulsate along with the rotation speed of the engine always exist objectively, and the periodic pulsation characteristics can be sensed very sensitively, so that people are concerned and complained; the pulse sound characteristics cannot be effectively identified only by evaluating the indexes of the sound pressure level, and complaints still can be caused by the existence of the pulse sound under the condition that the sound pressure level meets the requirements in the process of project development. The existence of very uncontrollable is measured through subjective evaluation, and the evaluated results are very different due to different hearing characteristics and subjective favorites of different people.
Patent document CN201910035860.1 discloses an objective evaluation method of impulse noise of a diesel engine, which firstly calculates the time-varying specific loudness of 24 critical frequency bands of a sound signal, and then calculates the line-to-pulse amplitude of a 24-frequency band compressed signal and the absolute amplitude of a non-compressed signal to comprehensively obtain an objective impulse noise evaluation index. However, the overall idea of the method is that from the aspect of the magnitude of sound, the root cause of the periodic pulse of the signal is not considered, and for the noise with lower magnitude contribution and larger periodic pulse contribution, the magnitude of the impulse contribution is difficult to accurately identify, and meanwhile, the method is greatly influenced by other background noise with the frequency similar to that of the pulse signal, and has larger limitation.
Therefore, it is necessary to develop a new method for evaluating the periodic pulsation noise of an internal combustion engine.
Disclosure of Invention
The invention aims to provide a periodic pulsation noise evaluation method of an internal combustion engine, which can accurately identify the periodic pulsation noise based on the auditory sense and the periodic pulsation nature of human ears; the severity of the periodic pulsation noise can be judged, and the main contribution frequency of the pulsation noise can be judged.
The invention relates to a periodic pulsation noise evaluation method of an internal combustion engine, which comprises the following steps:
step 1, collecting noise signals and rotating speed signals: collecting a noise signal S and a continuous time domain signal of a crankshaft rotation speed signal RPM under the stable rotation speed operation condition of the internal combustion engine;
Step 2, segment filtering is carried out on the noise signals: carrying out time domain filtering treatment on the noise continuous time domain signals acquired in the step 1 by adopting a band-pass filter, and decomposing the noise continuous time domain signals into 24 time domain signals containing different frequency information, wherein the time domain signals are S 1、S2、......、S24 respectively;
step 3, performing Hilbert transform on the multi-section filtering signal: performing Hilbert transform on the 24 time domain signals S 1、S2、......、S24 to obtain envelope time domain signals of the signals, wherein the envelope time domain signals are T 1、T2、......、T24 respectively;
Step 4, carrying out Fourier transform on each segment of signal: performing Fourier transform on each envelope time domain signal T 1、T2、......、T24 to obtain frequency domain signals of each envelope signal, wherein the frequency domain signals are Y 1、Y2、......、Y24 respectively;
step 5, calculating modulation depth of signals of each frequency band: dividing the amplitude A m of each modulation frequency in the frequency domain signal Y 1、Y2、......、Y24 of each envelope signal by the corresponding amplitude A C when the modulation frequency is 0 to obtain modulation depth M d corresponding to the modulation frequency one by one; the frequency domain signal Y 1、Y2、......、Y24 of each envelope signal is converted into a new signal X 1、X2、......、X24 by taking the modulation frequency F m as an abscissa and the modulation depth M d as an ordinate;
Step 6: the modulation depth of each order is calculated, specifically:
step 6a, combining the frequency information of the step 2 based on X 1、X2、......、X24 to obtain a critical-band-F m--Md three-dimensional spectrogram;
Step 6b, calculating the crankshaft rotating speed time domain signal RPM in the step 1 according to a formula RPM/60 to obtain the frequency corresponding to the 1 st order of the engine under the rotating speed, namely f orde1＝RPM/60*1,forde0.5＝RPM/60*0.5,forde1.5＝RPM/60*1.5,forde2 =RPM/60×2;
step 6c, in the three-dimensional spectrogram of the critical-band-F m--Md in step 6a, let F m be F orde0.5, and superposing all M d modulation depths under F orde0.5 modulation frequency to obtain M order0.5, and obtaining M order1,Morder1.5,Morder2 in the same way;
Step 7, calculating a periodic pulse index: according to the formula An evaluation index for evaluating the periodic pulsation noise is obtained, wherein i=order 1, order1.5, order2.
Optionally, in step 1, a continuous time domain signal of the noise signal S and the crankshaft rotational speed signal RPM under the stable rotational speed operation condition of the internal combustion engine is collected in a time tracking manner.
Optionally, in step 2, the filtering frequencies of the band-pass filter are sequentially set according to a frequency band range of 1-24bark specified by the critical-band, where the time domain signal S 1 includes only frequency domain information in 1bark band, the time domain signal S 2 includes only frequency domain information in 2bark band, the time domain signal S 3 includes only frequency domain information in 3bark band, … …, and the time domain signal S 24 includes only frequency domain information in 24bark band.
The invention has the following advantages:
According to the invention, firstly, model frequency band division is carried out according to critial-band, physiological and psychological effects of people in terms of sound hearing are fully considered, and on the other hand, from the aspect of signal modulation, the model frequency band division is closer to the periodic characteristics of periodic pulse signals, and quantitative analysis and evaluation are carried out on the noise in a subjective and objective manner more intuitively.
The method provided by the invention is simple to operate and high in practicability, can greatly reduce the labor and time costs for organizing subjective evaluation and achieving unified comments, can effectively unify the subjective and objective evaluation connection according to the method, and establishes the evaluation standard of periodic pulsation noise, thereby providing a basis for the NVH design and optimization control of the internal combustion engine.
Drawings
Fig. 1 is a schematic calculation flowchart of the present embodiment.
Fig. 2 is a schematic diagram of a steady-state noise continuous time domain signal of the internal combustion engine in the present embodiment.
Fig. 3 is a schematic diagram of a crankshaft rotational speed signal of the internal combustion engine in the present embodiment.
Fig. 4 is a schematic diagram of the engine noise segmentation filter according to the present embodiment after decomposition.
Fig. 5 is a schematic diagram of the segment noise after hilbert transform in the present embodiment.
Fig. 6 is a schematic diagram of fourier transform of the noise after hilbert transform in the present embodiment.
Fig. 7 is a schematic diagram of signal amplitude conversion to modulation depth in the present embodiment.
FIG. 8 is a three-dimensional spectrogram of critical-band-Fm-Md in this example.
FIG. 9 is a diagram showing the calculated ranges of 0.5 order, 1 order, 1.5 order, and 2 order modulation depths in the present embodiment
Fig. 10 is a schematic diagram of modulation depth of 0.5 order, 1 order, 1.5 order, and 2 order after superposition in the present embodiment.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings.
As shown in fig. 1, in the present embodiment, a periodic pulsation noise evaluation method of an internal combustion engine includes the steps of:
step 1, collecting noise signals and rotating speed signals: a continuous time domain signal of a noise signal S and a crankshaft rotational speed signal RPM under the stable rotational speed operation condition of the internal combustion engine is acquired in a time tracking mode, wherein the noise signal S is shown in fig. 2, and the crankshaft rotational speed signal RPM is shown in fig. 3.
And 2, performing time domain filtering processing on the noise signal S by adopting a band-pass filter, wherein the filtering frequency of the band-pass filter is sequentially set according to a frequency band range of 1-24 barks specified by the critical-band. Decomposing the noise time domain signal S into 24 time domain signals containing different frequency information through a filter, wherein the time domain signals are S 1、S2、......、S24 respectively; as shown in fig. 4.
Step 3, performing Hilbert transform on the multi-section filtering signal: and (3) carrying out Hilbert transformation on the S 1、S2、......、S24 time domain signals decomposed in the step (2) to obtain envelope time domain signals of the signals in the step (S 1、S2、......、S24), wherein the envelope time domain signals are sequentially T 1、T2、......、T24, as shown in fig. 5.
Step 4: each segment of signal is fourier transformed: performing discrete fourier transform on the total of 24 envelope time domain signals T 1、T2、......、T24 in step 3 to obtain a frequency domain signal Y 1、Y2、......、Y24 of the envelope signal, where the abscissa of the calculated Y 1、Y2、......、Y24 signal corresponds to the modulation frequency Fm of each signal S 1、S2、......、S24, and the ordinate corresponds to the amplitude Am of each signal at each frequency, where the amplitude corresponding to the modulation frequency 0 is a C, as shown in fig. 6.
Step 5, calculating modulation depth of signals of each frequency band: dividing the amplitude a m of each modulation frequency in the Y 1、Y2、......、Y24 signal by the corresponding amplitude a C when the modulation frequency is 0, to obtain a modulation depth M d corresponding to the modulation frequency F m one by one, and converting the Y 1、Y2、......、Y24 signal into a new signal X 1、X2、......、X24 by using the modulation frequency F m as the abscissa and the modulation depth M d as the ordinate, as shown in fig. 7.
Step 6, calculating the modulation depth of each order, specifically:
And 6a, combining the frequency information of the 1-24 band in the step 2 on the basis of X 1、X2、......、X24 to obtain a three-dimensional spectrogram of the 1-24 band-F m--Md, as shown in FIG. 8.
Step 6b: and (3) calculating the time domain signal RPM of the crankshaft in the step (1) according to a formula RPM/60 to obtain the frequency corresponding to the 1 st order of the engine under the rotating speed, namely f orde1＝RPM/60*1,forde0.5＝RPM/60*0.5,forde1.5＝RPM/60*1.5,forde2 =RPM/60×2.
As shown in fig. 1, the crankshaft rotational speed RPM is 717, and according to the formula RPM/60, the frequency corresponding to the 1 st order of the engine at this rotational speed of the engine is obtained, that is, f orde1 =rpm/60×1=11.95 Hz, the frequency corresponding to the 0.5 th order f orde0.5 =rpm/60×0.5=5.975 Hz, the frequency corresponding to the 1.5 th order f orde1.5 =rpm/60×1.5=17.925hz, and the frequency corresponding to the 2 nd order f orde2 =rpm/60×2=23.9 Hz.
Step 6c, in the three-dimensional spectrogram of the critical-band-F m--Md in step 6a, let F m be F orde0.5, and superposing all M d modulation depths under F orde0.5 modulation frequency to obtain M order0.5, and obtaining M order1,Morder1.5,Morder2 in the same way;
Step 7, calculating a periodic pulse index: according to the formula An evaluation index for evaluating the periodic pulsation noise is obtained, wherein i=order 1, order1.5, order2.
In the data shown in fig. 7, F m is made to be F orde0.5＝5.975Hz,forde1＝11.95Hz,forde1.5＝17.925Hz,forde2 =23.9 Hz in sequence, all M d modulation depths at the corresponding modulation frequencies are superimposed, the region is marked as shown in fig. 9, and M order0.5,Morder1,Morder1.5,Morder2 is obtained, as shown in fig. 10, and M order0.5＝9.1,Morder1＝2.6,Morder1.5＝2.4,Morder2 =1.4; finally according to the formulaThe resulting noise periodic pulsation index was 9.86.
The above examples are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above examples, and any other changes, modifications, substitutions, combinations, and simplifications that do not depart from the spirit and principle of the present invention should be made in the equivalent manner, and the embodiments are included in the protection scope of the present invention.
Claims (3)
1. A method for evaluating periodic pulsation noise of an internal combustion engine, characterized by comprising the steps of: the method comprises the following steps:
step 1, collecting noise signals and rotating speed signals: collecting a noise signal S and a continuous time domain signal of a crankshaft rotation speed signal RPM under the stable rotation speed operation condition of the internal combustion engine;
Step 2, segment filtering is carried out on the noise signals: carrying out time domain filtering treatment on the noise continuous time domain signals acquired in the step 1 by adopting a band-pass filter, and decomposing the noise continuous time domain signals into 24 time domain signals containing different frequency information, wherein the time domain signals are S 1、S2、......、S24 respectively;
step 3, performing Hilbert transform on the multi-section filtering signal: performing Hilbert transform on the 24 time domain signals S 1、S2、......、S24 to obtain envelope time domain signals of the signals, wherein the envelope time domain signals are T 1、T2、......、T24 respectively;
Step 4, carrying out Fourier transform on each segment of signal: performing Fourier transform on each envelope time domain signal T 1、T2、......、T24 to obtain frequency domain signals of each envelope signal, wherein the frequency domain signals are Y 1、Y2、......、Y24 respectively;
step 5, calculating modulation depth of signals of each frequency band: dividing the amplitude A m of each modulation frequency in the frequency domain signal Y 1、Y2、......、Y24 of each envelope signal by the corresponding amplitude A C when the modulation frequency is 0 to obtain modulation depth M d corresponding to the modulation frequency one by one; the frequency domain signal Y 1、Y2、......、Y24 of each envelope signal is converted into a new signal X 1、X2、......、X24 by taking the modulation frequency F m as an abscissa and the modulation depth M d as an ordinate;
Step 6: the modulation depth of each order is calculated, specifically:
step 6a, combining the frequency information of the step 2 based on X 1、X2、......、X24 to obtain a critical-band-F m--Md three-dimensional spectrogram;
Step 6b, calculating the crankshaft rotating speed time domain signal RPM in the step 1 according to a formula RPM/60 to obtain the frequency corresponding to the 1 st order of the engine under the rotating speed, namely f orde1＝RPM/60*1,forde0.5＝RPM/60*0.5,forde1.5＝RPM/60*1.5,forde2 =RPM/60×2;
step 6c, in the three-dimensional spectrogram of the critical-band-F m--Md in step 6a, let F m be F orde0.5, and superposing all M d modulation depths under F orde0.5 modulation frequency to obtain M order0.5, and obtaining M order1,Morder1.5,Morder2 in the same way;
Step 7, calculating a periodic pulse index: according to the formula An evaluation index for evaluating the periodic pulsation noise is obtained, wherein i=order 1, order1.5, order2.
2. The method for evaluating periodic pulsation noise of internal combustion engine according to claim 1, characterized in that: in the step 1, continuous time domain signals of a noise signal S and a crankshaft rotating speed signal RPM under the stable rotating speed running condition of the internal combustion engine are acquired in a time tracking mode.
3. The method for evaluating periodic pulsation noise of an internal combustion engine according to claim 1 or 2, characterized in that: in the step 2, the filtering frequency of the band-pass filter is set in sequence according to the frequency band range of 1-24bark specified by the critical-band, wherein the time domain signal S 1 only includes frequency domain information in 1bark band, the time domain signal S 2 only includes frequency domain information in 2bark band, the time domain signal S 3 only includes frequency domain information in 3bark band, … …, and the time domain signal S 24 only includes frequency domain information in 24bark band.
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