Mechanical vibration quantitative evaluation system and method based on microphone sensor

Abstract

The invention provides a mechanical vibration quantitative evaluation system and method based on a microphone sensor, and belongs to the technical field of mechanical vibration state monitoring. The system comprises a plurality of integrated probes, a signal processing unit, a sound insulation door state sensor, a signal processing unit and a man-machine interaction unit, an ultrasonic sensor in the integrated probe is used for measuring the distance to the surface of a workpiece, and a microphone sensor is used for synchronously collecting audio signals generated in the workpiece machining process. The soundproof door state sensor is used for inputting a switching value signal representing the opening and closing state of the soundproof door to the signal processing unit; the signal processing unit is used for synchronously receiving audio signals collected by the microphone sensors and distance data collected by the ultrasonic sensors, processing the audio signals and the distance data in combination with switching value signals, calculating to obtain vibration acceleration and displaying the vibration acceleration on the man-machine interaction unit. According to the method, the absolute quantity, repeatable and high-reliability quantitative evaluation of all the processing vibration intensities can be effectively realized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of mechanical vibration state monitoring, and particularly relates to a mechanical vibration quantitative evaluation system and method based on a microphone sensor. BACKGROUND

[0002] In the field of precision equipment, numerical control machine tools, etc., vibration during use is a key factor affecting the machining accuracy, service life, etc. of the equipment. Therefore, real-time and accurate monitoring and evaluation of the vibration of the equipment is crucial.

[0003] At present, the commonly used vibration measurement sensor is an acceleration sensor. Its advantages are direct measurement and high precision, but it has some inherent disadvantages: 1) contact type installation is required, which is difficult to install on high-speed rotating or high-temperature workpieces, or even cannot be installed; 2) the installation position has a huge impact on the measurement results, and different machine tools or workpieces need to redesign the installation scheme, which has poor universality; 3) the cost is relatively high, especially when multiple point monitoring is required.

[0004] The microphone sensor, as a non-contact acoustic sensor, provides a possibility to solve the above problems. It does not need to be installed on the measured object, and is flexible in arrangement and low in cost. However, there are two major challenges in directly using the microphone for vibration measurement: 1) distance sensitivity: the sound pressure intensity is inversely proportional to the square of the distance from the sound source to the microphone. For the same vibration source, the signal intensity collected by the microphone at different distances differs greatly, making it impossible to conduct unified and repeatable quantitative evaluation. 2) Environmental interference: environmental noise (such as the sound of other equipment running, air flow sound) in the processing site and the opening and closing state of the machine tool soundproof door will seriously pollute the vibration signal, resulting in distorted measurement results.

[0005] In the prior art, the method of simply using a microphone to collect sound and calculate the amplitude cannot overcome the influence of distance and environmental interference, and therefore cannot be used as a reliable quantitative evaluation basis, limiting the widespread application of microphone sensors in this field. SUMMARY

[0006] The present application provides a mechanical vibration quantitative evaluation system and method based on a microphone sensor to overcome the deficiencies in the prior art. The present application can effectively compensate for the influence of distance changes between the microphone and the workpiece, and can identify and correct the interference of the soundproof door state on the signal, ultimately achieving absolute, repeatable, and highly reliable quantitative evaluation of all processing vibration intensities.

[0007] To achieve the above object, the present application adopts the following technical solutions: In a first aspect, the present application provides a mechanical vibration quantitative evaluation system based on microphone sensors, comprising: a plurality of integrated probes, a signal processing unit, a soundproof door state sensor, a signal processing unit and a man-machine interaction unit; the integrated probe is integrated with a microphone sensor and an ultrasonic sensor, the ultrasonic sensor is used to measure the distance from the workpiece surface, the microphone sensor is used to synchronously collect the audio signals generated in the workpiece processing process, and the plurality of integrated probes are installed to point to the workpiece from different angles; the soundproof door state sensor is installed on the machine tool soundproof door and used to input the on-off signal representing the opening and closing state of the soundproof door to the signal processing unit; the signal processing unit is used to synchronously receive the audio signals collected by the plurality of microphone sensors and the distance data collected by the plurality of ultrasonic sensors, process in combination with the on-off signal, calculate the vibration acceleration, and display on the man-machine interaction unit.

[0008] Optionally, the signal processing unit adopts an industrial computer equipped with a multi-channel high-speed data acquisition card.

[0009] Optionally, the soundproof door state sensor adopts a magnetic proximity switch or a limit switch.

[0010] In a second aspect, the present application provides a mechanical vibration quantitative evaluation method based on microphone sensors, which is realized by using the mechanical vibration quantitative evaluation system of the first aspect, and comprises the following steps: S101: after the system is powered on, a plurality of ultrasonic sensors in the machine tool coordinate system are loaded with pre-calibrated three-dimensional coordinates; S102: during the workpiece processing, the plurality of ultrasonic sensors synchronously emit ultrasonic waves and receive echoes at a predetermined frequency; a temporary coordinate system is established with one of the ultrasonic sensors as the origin, a plurality of distance equations of the ultrasonic sensors to the target point P are established, the coordinates of the target point P are obtained by solving the plurality of distance equations, the distance L from the target point P to the microphone sensor integrated with the origin is calculated, and the distance attenuation coefficient is calculated according to the distance L; S103: the plurality of microphone sensors synchronously collect audio signals, and the collected multi-channel audio signals are sent to the signal processing unit for pretreatment to extract characteristic values representing vibration intensity; S104: the signal processing unit reads the signal of the soundproof door state sensor, selects different sound insulation layer sound transmission loss values TL according to the opening and closing state of the soundproof door, and calculates the sound insulation layer attenuation coefficient according to the sound insulation layer sound transmission loss value TL; S105: the vibration acceleration is calculated according to the data obtained in steps S102 to S104, and the numerical value and waveform of the vibration acceleration are displayed on the man-machine interaction unit.

[0011] Optionally, in step S102, the calculation formula of the distance attenuation coefficient is: ; In the formula, Indicates the distance attenuation coefficient. k It is a constant related to the intensity of the sound source. n It is the decay index.

[0012] Optionally, in step S103, the preprocessing process performed by the signal processing unit is as follows: A high-pass filter is used to remove low-frequency power supply interference from multi-channel audio signals; Perform a Fast Fourier Transform on each frame of audio signal to convert it from the time domain to the frequency domain; Based on the known modal frequency characteristics of the workpiece, significant peak frequencies are extracted within the 0-2000Hz frequency band, and the sound pressure level near the peak frequencies is integrated or its root mean square is calculated as a characteristic value representing the vibration intensity. .

[0013] Optionally, in step S104, selecting different sound insulation layer transmission loss values ​​TL according to the opening and closing state of the soundproof door specifically involves: If the door is closed, then TL→∞; If the door is open, then TL=0.

[0014] Optionally, in step S104, the formula for calculating the attenuation coefficient of the sound insulation layer is: ; In the formula, This represents the sound insulation layer attenuation coefficient. This represents the transmission coefficient.

[0015] Optionally, in step S105, the data obtained in steps S102 to S104 are substituted into the following comprehensive relationship model to calculate the vibration acceleration: ; In the formula, Indicates vibration acceleration. This represents the overall proportionality constant, which is determined through experimental calibration. Characteristic values ​​representing vibration intensity A It is the effective area of ​​the sound wave. α It is the sound absorption coefficient of the structural surface. m It is the effective quality of the structure. Indicates the distance attenuation coefficient. This represents the sound insulation layer attenuation coefficient.

[0016] The beneficial effects of this invention are: (1) This invention utilizes a microphone to achieve non-contact measurement, which solves the problem of inconvenient installation of contact sensors and is especially suitable for vibration monitoring of high-speed, high-temperature or complex-shaped equipment.

[0017] (2) By introducing real-time distance compensation and environmental (soundproof door) correction, the main interference factors are eliminated, making the measurement result an absolute value that is independent of distance and environment. Measurement results from different times and different devices can be compared with each other, truly realizing quantitative evaluation.

[0018] (3) One of the core structures of the present invention is a microphone sensor, which is far less expensive than a high-performance accelerometer system and does not require a complex mechanical installation structure, making the device easy to move and use. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the mechanical vibration quantitative evaluation system based on a microphone sensor according to the present invention.

[0020] Figure 2 This is a flowchart of the workflow of the quantitative evaluation method for mechanical vibration based on a microphone sensor according to the present invention.

[0021] The attached figures are labeled as follows: 100, machining center; 101-105, microphone-ultrasonic integrated probe; 106, workpiece; 107, signal processing unit; 108, human-machine interaction unit; 109, soundproof door status sensor; 110, machine tool soundproof door. Detailed Implementation

[0022] The invention will now be described in further detail with reference to the accompanying drawings.

[0023] Example 1 This embodiment proposes a quantitative evaluation system for mechanical vibration based on a microphone sensor, such as... Figure 1 As shown, it includes the following hardware units: Microphone-Ultrasonic Integrated Probes 101-105: Five such integrated probes are arranged around the interior space of machining center 100. They are mounted on rigid supports outside the machine tool, ensuring their positions are fixed and their coordinates are known. The ultrasonic sensors in the probes are used to accurately measure their distance to point P on the surface of workpiece 106. The microphone sensors in the probes are used to synchronously acquire audio signals generated during machining. The installation positions of all probes should cover the main machining area of ​​the workpiece as much as possible and point at the workpiece from different angles to ensure the effectiveness of ultrasonic ranging and audio acquisition.

[0024] Signal Processing Unit 107: This embodiment uses an industrial computer (IPC) as the core processing unit. The IPC is equipped with a multi-channel high-speed data acquisition card (DAQ card) for simultaneously receiving audio signals from five microphone channels and distance data from five ultrasonic channels. Dedicated signal processing and algorithm software runs within the IPC.

[0025] Human-Machine Interaction Unit 108: A touchscreen display connected to the IPC is used to display workpiece coordinates, distances to each microphone, calculated vibration acceleration values, historical trend graphs, and alarm information in real time. Operators can set system parameters (such as standard reference distance d0 and threshold values) via the touchscreen.

[0026] Soundproof door status sensor 109: A simple magnetic proximity switch or limit switch is installed on the machine tool soundproof door 110 to detect the opening and closing status of the door in real time and input this switching signal to the IPC.

[0027] Example 2 This embodiment proposes a quantitative evaluation method for mechanical vibration based on a microphone sensor, which is implemented using the quantitative evaluation system for mechanical vibration from Embodiment 1. The specific working steps are as follows: S101: System Initialization and Coordinate Calibration After the system is powered on, the three-dimensional coordinates (Xi, Yi, Zi) of the five pre-calibrated ultrasonic sensors (AE) in the machine tool coordinate system are loaded first, i=A, B, C, D, E. These coordinates are calibrated in one go using precision measuring equipment such as a laser tracker after installation and then stored in the system.

[0028] In this embodiment, five ultrasonic sensors are denoted as A, B, C, D, and E. Sensor C is set as the origin of the workpiece coordinate system. The coordinates of the five points are known as (XA, YA, ZA), (XB, YB, ZB), (XC, YC, ZC), (XD, YD, ZD), and (XE, YE, ZE). The coordinates of the measured point P are (XP, YP, ZP). A distance equation between points A and P is established. Similarly, calculate the distances from points B, C, D, and E to point P, and obtain the coordinates (XP, YP, ZP) of the measured point P.

[0029] S102: Distance Measurement and Workpiece Point Positioning During the processing, five ultrasonic sensors synchronously emit ultrasonic waves at a predetermined frequency and receive the echoes. Based on the time-of-flight principle, the signal processing unit calculates in real time the distance Li, i=A, B,C, D, E, from each sensor to the target point P on the workpiece.

[0030] Subsequently, the system establishes a temporary coordinate system with sensor C as the origin. By solving a system of five distance equations (e.g., using the least squares method for optimization), the real-time three-dimensional coordinates (Xi, Yi, Zi) of point P at the current moment are calculated. The distance L from point P to the reference microphone (integrated with sensor C) is also calculated.

[0031] The magnitude of sound pressure is closely related to the distance from the sound source. For a point sound source propagating in a free field, the sound pressure follows the inverse square law. Since sound pressure is inversely proportional to distance, while acceleration is directly proportional to sound pressure, vibration acceleration is inversely proportional to the square of the distance. Introduce a distance attenuation coefficient into the model. C d , ,in, L It is the distance (m) from the sound source to the target structure. n It is the decay index. k It is a constant related to the intensity of the sound source itself.

[0032] S103: Audio Signal Acquisition and Preprocessing While performing ultrasonic ranging, five microphones simultaneously acquire audio signals at a high sampling rate (e.g., 2kHz). The acquired multi-channel audio data is then sent to the signal processing unit.

[0033] The preprocessing steps are as follows: a) Noise reduction: First, a high-pass filter (cutoff frequency 50Hz) is used to filter out low-frequency power supply interference.

[0034] b) Fourier Transform (FFT) converts the time-domain audio signal of each frame into the frequency domain using a fast Fourier transform.

[0035] c) Feature extraction: Based on the known modal frequency characteristics of the workpiece (obtained through simulation or experiment), significant peak frequencies are extracted within the 0-2000Hz frequency band. The sound pressure levels near these peak frequencies are integrated or their root mean square (RMS) values ​​are calculated as characteristic values ​​representing the vibration intensity. (Unit: Pa). In this embodiment, the microphone signal integrated with sensor C is selected as the main signal for calculation.

[0036] S104: Soundproof door status recognition Read the signal from the soundproof door status sensor 109. Based on the door's open / closed state, select different sound insulation layer transmission loss values ​​TL. If the door is closed, then TL→∞.

[0037] If the door is open, then TL=0.

[0038] The effects of sound insulation layers (such as soundproof enclosures, double-glazed windows, and damping materials) are complex; they typically significantly reduce the sound energy transmitted to a structure. Their effect is usually measured in decibels (dB). Decibels are logarithmic and need to be converted to a linear scaling factor before being used in formulas. The sound insulation layer acts like an attenuator.

[0039] The relationship between sound transmission loss TL and transmission coefficient τ is as follows: Therefore, the transmission coefficient This transmission coefficient τ is the sound insulation layer coefficient to be introduced. With a sound insulation layer, the effective excitation sound pressure becomes... (Because energy is proportional to the square of sound pressure, and force is proportional to sound pressure). To simplify the model, the effective sound pressure is often considered to be... p ⋅ τ c ,in c It is an empirical constant. For practical purposes, it is often combined into a single coefficient.

[0040] Define a sound insulation layer attenuation coefficient ,in, TL TL (Transmission Loss in dB) is the sound transmission loss of the sound insulation layer at a specific frequency. A higher TL value indicates better sound insulation. C t The smaller. C t It is a coefficient between 0 and 1 (TL=0 without sound insulation layer). C t =1; For perfect sound insulation, TL→∞. C t →0).

[0041] S105: Vibration Acceleration Calculation Substituting the data obtained from the above steps into the comprehensive relationship model, the compensated absolute vibration acceleration value is calculated:

[0042] in: It is the peak value of vibration acceleration (m / s²). It is the peak sound pressure level (Pa) at a certain reference distance from the sound source. It is a comprehensive proportionality constant, which includes sound source characteristics and constants. k And other factors resulting from model simplification. This constant usually needs to be determined through experimental calibration. A It is the effective area (m²) of the sound wave action. α It is the sound absorption coefficient of the structural surface. m It is the effective mass of the structure (kg). L It is the distance (m) from the sound source to the target structure.n It is the decay index. TL It is the sound transmission loss (dB) of the sound insulation layer at a specific frequency.

[0043] G , , n , , These parameters require experimental calibration for a specific machine tool-workpiece combination. The calibration method is as follows: Install a standard accelerometer on the workpiece as a reference. Under known distance L and known soundproof door status (usually closed), perform a test machining operation. Simultaneously record the vibration acceleration values ​​measured by the standard accelerometer. And the acceleration values ​​measured by this system By inversely solving the model formula, the comprehensive proportionality constant G and the verification attenuation index can be calculated. n These calibrated parameters are then stored in the system configuration file.

[0044] In this calculation, L is the distance measured in real time in S102. C t These are coefficients calculated in real time based on the gate state in S104. It is the acceleration value obtained from S105.

[0045] Displayed in real time on the screen of the access interaction unit 108 The numerical values ​​and waveforms.

[0046] if If the threshold is exceeded, an audible and visual alarm will be triggered, and an alarm signal will be sent to the CNC system through the data output interface to prompt the operator or trigger the machine tool to automatically reduce speed or stop.

[0047] All data, including timestamps, coordinates, acceleration values, and gate status, are recorded in the database for subsequent process analysis and optimization.

[0048] This system was applied to monitor the high-speed milling process of aluminum alloy workpieces on a five-axis CNC machining center. Five microphone-ultrasonic integrated probes were mounted on a bracket a distance outside the machine tool. After system calibration, the parameters G=0.85 and n=2.1 were determined. During machining, the system displayed the vibration acceleration in real time, varying between 5.2 m / s² and 12.8 m / s². When an abnormal cutting caused the vibration value to suddenly jump to 25.3 m / s² and last for 50 ms, the system reliably issued an alarm. Manual intervention was immediately initiated, and the feed rate was reduced, effectively protecting the tool and preventing workpiece scrap. Post-processing analysis of the data records revealed that this vibration anomaly was related to a sudden increase in the depth of cut. Throughout the entire process, the operator did not open the door, and the soundproof door coefficient was [not specified]. C tBy maintaining a constant value, the system successfully eliminated the influence of distance changes on the sound pressure signal, achieving stable quantitative evaluation.

[0049] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principle of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A quantitative evaluation system for mechanical vibration based on a microphone sensor, characterized in that, include: The system comprises multiple integrated probes, a signal processing unit, a soundproof door status sensor, and a human-machine interface unit. Each integrated probe incorporates a microphone sensor and an ultrasonic sensor. The ultrasonic sensor measures the distance to the workpiece surface, while the microphone sensor synchronously acquires audio signals generated during workpiece processing. Multiple integrated probes are mounted to point at the workpiece from different angles. The soundproof door status sensor is installed on the machine tool's soundproof door and inputs a switching signal indicating the door's open / closed state to the signal processing unit. The signal processing unit synchronously receives audio signals from multiple microphone sensors and distance data from multiple ultrasonic sensors, processes the switching signal, calculates the vibration acceleration, and displays it on the human-machine interface unit.

2. The mechanical vibration quantitative evaluation system based on a microphone sensor as described in claim 1, characterized in that: The signal processing unit uses an industrial computer equipped with a multi-channel high-speed data acquisition card.

3. The mechanical vibration quantitative evaluation system based on a microphone sensor as described in claim 1, characterized in that: The soundproof door status sensor uses a magnetic proximity switch or a limit switch.

4. A quantitative evaluation method for mechanical vibration based on a microphone sensor, implemented using the quantitative evaluation system for mechanical vibration as described in any one of claims 1-3, characterized in that, Includes the following steps: S101: After the system is powered on, load the three-dimensional coordinates of multiple pre-calibrated ultrasonic sensors in the machine tool coordinate system; S102: During the workpiece processing, multiple ultrasonic sensors synchronously emit ultrasonic waves and receive echoes at a predetermined frequency; a temporary coordinate system is established with one of the ultrasonic sensors as the origin, and distance equations from multiple ultrasonic sensors to the target point P are established. The coordinates of the target point P are obtained by solving multiple distance equations, and then the distance L from the target point P to the microphone sensor integrated with the origin is calculated. The distance attenuation coefficient is calculated based on the distance L. S103: Multiple microphone sensors simultaneously acquire audio signals, and send the acquired multi-channel audio signals to the signal processing unit for preprocessing to extract feature values ​​representing vibration intensity; S104: The signal processing unit reads the signal from the soundproof door status sensor and selects different sound insulation layer transmission loss values ​​TL according to the opening and closing status of the soundproof door, and calculates the sound insulation layer attenuation coefficient based on the sound insulation layer transmission loss value TL. S105: Calculate the vibration acceleration based on the data obtained in steps S102 to S104, and display the value and waveform of the vibration acceleration on the human-machine interaction unit.

5. The method for quantitative evaluation of mechanical vibration based on a microphone sensor as described in claim 4, characterized in that: In step S102, the formula for calculating the distance attenuation coefficient is: ； In the formula, Indicates the distance attenuation coefficient. k It is a constant related to the intensity of the sound source. n It is the decay index.

6. The quantitative evaluation method for mechanical vibration based on a microphone sensor as described in claim 4, characterized in that: In step S103, the preprocessing process performed by the signal processing unit is as follows: A high-pass filter is used to remove low-frequency power supply interference from multi-channel audio signals; Perform a Fast Fourier Transform on each frame of audio signal to convert it from the time domain to the frequency domain; Based on the known modal frequency characteristics of the workpiece, significant peak frequencies are extracted within the 0-2000Hz frequency band, and the sound pressure level near the peak frequencies is integrated or its root mean square is calculated as a characteristic value representing the vibration intensity. .

7. The method for quantitative evaluation of mechanical vibration based on a microphone sensor as described in claim 4, characterized in that: In step S104, the step of selecting different sound insulation layer transmission loss values ​​TL according to the opening and closing status of the soundproof door specifically involves: If the door is closed, then TL→∞; If the door is open, then TL=0.

8. The method for quantitative evaluation of mechanical vibration based on a microphone sensor as described in claim 7, characterized in that: In step S104, the formula for calculating the attenuation coefficient of the sound insulation layer is: ； In the formula, This represents the sound insulation layer attenuation coefficient. This represents the transmission coefficient.

9. The method for quantitative evaluation of mechanical vibration based on a microphone sensor as described in claim 4, characterized in that: In step S105, the data obtained in steps S102 to S104 are substituted into the following comprehensive relationship model to calculate the vibration acceleration: ； In the formula, Indicates vibration acceleration. This represents the overall proportionality constant, which is determined through experimental calibration. Characteristic values ​​representing vibration intensity A It is the effective area of ​​the sound wave. α It is the sound absorption coefficient of the structural surface. m It is the effective quality of the structure. Indicates the distance attenuation coefficient. This represents the sound insulation layer attenuation coefficient.

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