A method for diagnosing abnormal engine noise

Abstract

This invention belongs to the technical field of power machinery and discloses a method for diagnosing abnormal engine noise, comprising the following steps: S1, engine noise bench testing; S2, protrusion ratio calculation; S3, protrusion ratio MAP feature extraction; S4, abnormal noise frequency band verification; and S5, abnormal noise source tracing and diagnosis. This invention, for the first time, proposes tracking abnormal noise frequency bands based on the protrusion ratio MAP and the protrusion ratio frequency domain peak. Combined with acoustic array technology, this method is applicable to diagnosing both order and non-order abnormal engine noise sources. The protrusion ratio MAP and the protrusion ratio frequency domain peak take into account the noise spectrum characteristics, providing a more representative representation of abnormal noise.

Description

Technical Field

[0001] The invention belongs to the technical field of power machinery, and in particular relates to a method for diagnosing abnormal noise of an engine. Background Art

[0002] Because the human ear is sensitive to high-frequency sounds, abnormal noise can directly impact a product's sound quality. Vehicle and engine structures are complex, and noise signal characteristics are highly nonlinear and non-stationary, making effective diagnosis of abnormal noise sources a challenge.

[0003] Regarding the research on abnormal noise diagnosis, current studies mostly use noise signal order analysis to diagnose, determine the main abnormal noise orders of vehicles and power machinery through order analysis, and finally trace the source based on the order spectrum results to identify the source of the order abnormal noise.

[0004] Since not all abnormal noise sources are order-based, this method has certain limitations for the diagnosis of non-order abnormal noise sources. The introduction of the prominence ratio (PR) parameter provides a possibility for abnormal noise characterization, while the traditional PR parameter is calculated based on the full frequency band. The PR value is not large in the entire frequency band, but in a certain frequency band, the PR peak is very large, and a strong harsh feeling may still occur. Therefore, when diagnosing abnormal noise, the traditional PR ignores the influence of the relative energy between frequency bands, and there is a problem of insufficient parameter abnormal noise representation. From the above analysis, it can be seen that it is necessary to consider the spectral characteristics of the noise and propose a more universal engine abnormal noise diagnosis method to provide guidance for improving engine sound quality. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for diagnosing abnormal noise in an engine, so as to solve the technical problem that the traditional PR ignores the influence of relative energy between frequency bands when performing abnormal noise diagnosis, resulting in insufficient parametric representation of abnormal noise.

[0006] To achieve the above objectives, the specific technical solutions of the engine abnormal noise diagnosis method of the present invention are as follows:

[0007] A method for diagnosing abnormal engine noise, comprising the following steps:

[0008] S1. Engine noise bench test: Conduct a 1m noise test of the entire engine in a semi-anechoic chamber, collect test noise signals, test conditions are abnormal noise conditions, the sampling frequency is 40960Hz, and the test time is 10s;

[0009] S2. Prominence ratio calculation: According to the ECMA-74:2012 standard, calculate the prominence ratio of the test noise signal in S1. The calculation is as follows:

[0010]

[0011] Where W M is the sound energy of the critical frequency band where the monotonic sound is located, W L W M Sound energy in the adjacent lower critical frequency band, W U W M The sound energy of the adjacent high critical frequency band, in Pa 2 ;

[0012] S3, protrusion ratio MAP feature extraction: Based on the engine noise PR calculation results of S2, the protrusion ratio MAP and PR frequency domain peaks are extracted to determine the possible frequency bands where abnormal engine noise is generated;

[0013] S4. Abnormal sound frequency band verification: Perform band-stop filtering on the noise samples of the abnormal sound frequency band obtained in S3, perform sound quality tests on the original samples and the filtered sound samples, monitor the changes in the noise and abnormal sound characteristics, and calculate the changes in the PR frequency domain peak before and after filtering to test the accuracy of the abnormal sound frequency band positioning;

[0014] S5. Abnormal noise tracing and diagnosis: Based on the abnormal noise frequency band obtained in S4, the acoustic array technology is used to diagnose and trace the abnormal engine noise.

[0015] Among them, S5 uses the Bayesian algorithm to diagnose and trace the high-frequency sound source.

[0016] The engine abnormal noise diagnosis method of the present invention has the following advantages: it is the first to propose abnormal noise frequency band tracking based on the protrusion ratio MAP and the protrusion ratio frequency domain peak value, and combined with the acoustic array technology, it is applicable to the diagnosis of both order and non-order abnormal noise sources of the engine; based on the protrusion ratio MAP and the protrusion ratio frequency domain peak value, the noise spectrum characteristics are taken into account, which is more representative of the abnormal noise. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is the technical roadmap of the engine abnormal noise diagnosis method of the present invention;

[0018] Figure 2 To highlight the frequency domain derived characteristic parameter diagram compared to MAP. DETAILED DESCRIPTION

[0019] In order to better understand the purpose, structure and function of the present invention, the following is a further detailed description of an engine abnormal noise diagnosis method of the present invention in conjunction with the accompanying drawings.

[0020] In the study of abnormal noise source diagnosis, in order to solve the problems of low versatility of order analysis method and insufficient representation of abnormal noise by traditional PR parameter, this study extracts prominence ratio MAP information based on traditional prominence ratio (PR) and constructs PR frequency domain derived parameters. The spectral source of abnormal noise is determined by prominence ratio MAP, which provides guidance for frequency band tracking of engine abnormal noise diagnosis. The technical route of the engine abnormal noise diagnosis method of this embodiment is as follows: Figure 1 The specific steps are as follows:

[0021] Step 1: Engine noise bench test

[0022] The engine noise test at 1m is carried out in a semi-anechoic chamber. The test condition is the engine abnormal noise condition, the sampling frequency is 40960Hz, the test time is 10s, and the frequency resolution is 1Hz.

[0023] Step 2: Calculation of noise prominence ratio

[0024] Calculate the prominence ratio of the engine noise based on the test data in step 1. According to the ECMA-74:2012 standard, PR is defined as the ratio of the sound energy in the critical frequency band where the monotonic sound is located to the average sound energy in its adjacent critical frequency bands. The calculation is shown in the following formula:

[0025]

[0026] Where W M is the sound energy of the critical frequency band where the monotonic sound is located, W L W M Sound energy in the adjacent lower critical frequency band, W U W M The sound energy of the adjacent high critical frequency band, in Pa 2 .

[0027] Step 3: PR frequency domain derivative feature extraction

[0028] Extract the engine noise prominence ratio MAP based on step 2, such as Figure 2 As shown in the figure, the interval with prominent bright band in the protrusion ratio MAP may have abnormal noise (i.e. Figure 2 The PR frequency domain peak parameter is extracted. The PR frequency domain peak value of the noise signal extracted in this example is 13dB, indicating prominent noise in this frequency band, which may cause abnormal noise. The prominent ratio frequency domain MAP provides guidance for determining the abnormal noise frequency band, and the PR frequency domain peak value lays the foundation for determining abnormal noise.

[0029] Step 4: Locate the abnormal sound frequency band

[0030] Based on the abnormal noise frequency band obtained in step 3, a band-stop filter is designed for the engine abnormal noise. The purpose of the band-stop filter is to filter out possible abnormal noise, and the sound quality test is performed on the original samples and the filtered samples to monitor the changes in the noise abnormality characteristics. At the same time, the changes in the PR frequency domain peak before and after filtering are calculated to verify the accuracy of the abnormal noise frequency band positioning.

[0031] Step 5: Identify the source of abnormal noise

[0032] Acoustic array technology was used to trace the 12,000-14,500 Hz noise identified in step 4. The acoustic array test system consists of an acoustic camera, a Power-over-Ethernet (POE) adapter, and a data acquisition computer. Bayesian algorithms offer higher spatial resolution than other noise processing methods for high-frequency noise signals and are well-suited for both near-field and far-field applications. Using the Bayesian algorithm during testing to trace the source of high-frequency noise abnormalities can help pinpoint the source of abnormal engine noise.

[0033] The beneficial effects brought about by the technical solution of the present invention are:

[0034] (1) The traditional PR parameter is calculated based on the full frequency band. The PR value for the full frequency band is small, and the PR value for the abnormal sound caused by the prominent noise in a certain frequency band is not representative enough. Based on the prominence ratio MAP and the prominence ratio frequency domain peak, the spectral characteristics of the noise are taken into account, which is more representative of the abnormal sound.

[0035] (2) For the first time, it is proposed to track the abnormal noise frequency band based on the protrusion ratio MAP and the protrusion ratio frequency domain peak value. Combined with the acoustic array technology, it is applicable to the diagnosis of engine order and non-order abnormal noise sources.

[0036] Although the embodiments of the present invention are described in conjunction with the accompanying drawings, it is apparent to those skilled in the art that several variations and improvements may be made without departing from the principles of the present invention, and these should also be considered to fall within the scope of protection of the present invention.

Claims

1. A method for diagnosing abnormal engine noise, characterized in that: The following steps are involved: S1. Engine noise bench test: Conduct engine noise test in a semi-anechoic chamber and collect test noise signals; S2. Prominence ratio calculation: According to the ECMA-74:2012 standard, calculate the prominence ratio of the test noise signal described in S1. The calculation is as follows: in is the sound energy of the critical frequency band where the monotonic sound is located, for The sound energy of the adjacent lower critical frequency band, for The sound energy of the adjacent high critical frequency band, in Pa 2 ; S3, protrusion ratio MAP feature extraction: Based on the engine noise PR calculation results of S2, the protrusion ratio MAP and PR frequency domain peaks are extracted to determine the possible frequency bands where abnormal engine noise is generated; S4. Abnormal sound frequency band verification: Perform band-stop filtering on the noise samples of the abnormal sound frequency band obtained in S3, perform sound quality tests on the original samples and the filtered sound samples, monitor the changes in the noise and abnormal sound characteristics, and calculate the changes in the PR frequency domain peak before and after filtering to test the accuracy of the abnormal sound frequency band positioning; S5. Abnormal noise tracing and diagnosis: Based on the abnormal noise frequency band obtained in S4, the acoustic array technology is used to diagnose and trace the abnormal engine noise.

2. The engine abnormal noise diagnosis method according to claim 1, characterized in that: S5 uses the Bayesian algorithm to diagnose and trace high-frequency sound sources.

3. The engine abnormal noise diagnosis method according to claim 1, characterized in that: The test condition of the noise test in S1 is an abnormal sound condition, the sampling frequency is 40960 Hz, and the test time is 10s.

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