Mine air volume measuring method and system based on optical section scanning

Abstract

The invention provides a mine air volume measuring method and system based on optical section scanning, and relates to the technical field of mine safety monitoring and ventilation. The method comprises the following steps: establishing a measurement coordinate system of a to-be-measured roadway section, and performing discretization measurement on the to-be-measured roadway section through optical scanning to obtain a space coordinate and a scanning geometric parameter of each measurement grid point; resolving the radial wind speed of each measurement grid point point by point by adopting an optical coherent detection technology; based on the space vector projection relation, the radial wind speed of each measurement grid point is converted into the axial wind speed of the roadway; calculating an area infinitesimal element represented by each measurement grid point according to the scanning geometric parameters; and according to the obtained axial wind speed of the roadway and the represented area infinitesimal, performing weighted integration on all measurement grid points in the section of the roadway to be measured to obtain the total wind quantity of the roadway of the section of the roadway to be measured. According to the invention, non-contact, high-precision, rapid and direct measurement of the full-section air volume of the mine can be effectively realized.

Description

Technical Field

[0001] This invention relates to the field of mine safety monitoring and ventilation technology, and in particular to a method and system for measuring mine air volume based on optical cross-sectional scanning. Background Technology

[0002] Mine ventilation systems are critical facilities for ensuring safe production in coal mines, and accurate online monitoring of air volume is of paramount importance for effectively diluting and removing harmful substances such as gas and dust, and preventing major disasters. As a key parameter characterizing mine ventilation capacity, the accuracy of air volume measurement directly determines the effectiveness and reliability of ventilation system control.

[0003] Currently, mine ventilation measurement mainly suffers from the following technical deficiencies:

[0004] (1) Traditional mechanical anemometer measurement method relies on manual operation. The anemometer needs to move the anemometer along a specific route in the roadway cross section, record the wind speed at multiple measuring points, and then calculate the average value. This method has obvious limitations: 1) The measurement process is time-consuming and labor-intensive, and inefficient; 2) The measurement results are greatly affected by the operator's skill level and subjective judgment; 3) Continuous online monitoring cannot be achieved, making it difficult to detect abnormalities in the ventilation system in a timely manner.

[0005] (2) Existing electronic wind measurement technologies, such as ultrasonic time difference method, although have achieved automated measurement, are essentially still single-point wind speed measurement. The measurement accuracy is easily affected by the complex environment downhole (such as high concentration of dust, fog, humidity and gas composition, etc.), resulting in a fundamental measurement deviation and making it difficult to achieve accurate measurement.

[0006] (3) In complex working conditions such as irregular roadway cross-section and interference from pipelines and other structures, the irregular roadway, multi-path bifurcation area and dynamic cross-sectional characteristics of the underground make it difficult for traditional methods to accurately obtain the effective ventilation cross-sectional area and to set up representative measuring points, resulting in significant or even complete failure of air volume estimation error.

[0007] In recent years, the development of optical anemometer technology has provided a new solution for mine ventilation measurement. However, existing optical anemometers mostly adopt a single-point measurement mode, which cannot comprehensively reflect the wind speed distribution characteristics of the tunnel cross-section. Some methods use the construction of a digital twin model of the tunnel to reconstruct a complex three-dimensional flow field. This method is complex, computationally intensive, and overly dependent on the accuracy of the three-dimensional scanning, making it difficult to meet the engineering requirements of real-time, rapid, and stable applications in underground mines. Therefore, there is an urgent need to develop a new mine ventilation monitoring technology that can achieve accurate measurement of the entire cross-section and has good engineering applicability. Summary of the Invention

[0008] To address the technical bottlenecks in existing technologies, such as the large errors caused by "point-to-surface" measurement methods, the difficulty in accurately obtaining the cross-sectional dimensions of complex roadways, and the poor engineering applicability of traditional laser wind measurement methods due to their reliance on complex flow field models, this invention proposes a mine air volume measurement method and system based on optical cross-sectional scanning, using the core ideas of roadway cross-section discretization scanning and area-weighted integration. The aim is to achieve non-contact, high-precision, rapid, and direct measurement of the air volume across the entire mine cross-section.

[0009] On the one hand, this invention proposes a method for measuring mine ventilation based on optical cross-sectional scanning, which includes the following process:

[0010] Establish a measurement coordinate system for the cross-section of the roadway to be measured, and under this measurement coordinate system, perform discretization measurement of the cross-section of the roadway to be measured by optical scanning to obtain the spatial coordinates and scanning geometric parameters of several measurement grid points;

[0011] Based on the spatial coordinates and scanning geometric parameters of all measurement grid points, the radial wind speed of each measurement grid point is calculated point by point using optical coherent detection technology;

[0012] Based on the spatial vector projection relationship, the radial wind speed of each measurement grid point is converted into the axial wind speed of the roadway at each measurement grid point;

[0013] Based on the scanning geometry parameters, calculate the area micro-element represented by each measurement grid point;

[0014] Based on the axial wind speed of each measurement grid point and the area micro-element it represents, a weighted integral is performed on all measurement grid points in the cross-section of the roadway to be measured to obtain the total air volume of the roadway cross-section.

[0015] Furthermore, the specific details of establishing a measurement coordinate system for the cross-section of the roadway to be measured, and discretizing the cross-section of the roadway to be measured by optical scanning under this measurement coordinate system to obtain the spatial coordinates and scanning geometric parameters of several measurement grid points are as follows:

[0016] For any cross-section of the roadway to be measured, the origin of the coordinate system is the measurement reference point within that cross-section. Establish a spatial rectangular coordinate system This serves as the measurement coordinate system for the cross-section of the roadway to be measured; where... Both represent coordinate axes, and The positive direction of the axis is along the axis of the roadway to be measured and points in the expected downstream direction of the airflow. The positive direction of the axis is perpendicular to the axis of the roadway in the horizontal plane and points to the other side of the roadway. The positive direction of the axis points vertically upwards towards the tunnel roof;

[0017] Based on the aforementioned measurement coordinate system, the cross-section of the roadway to be measured is discretized into... The measurement grid points are determined according to a set rule, and a scan path is generated; where Indicates the number of scan points in the horizontal direction. Indicates the number of scan points in the vertical direction;

[0018] Based on the generated scanning path, optical scanning is performed on the cross-section of the roadway to be measured, and the spatial coordinates and scanning geometric parameters of each measurement point on the cross-section of the roadway to be measured are obtained in sequence.

[0019] Furthermore, the measurement reference point is the optical center of the device that is fixedly installed within the cross-section of the roadway to be measured and used for all-fiber coherent laser detection of the cross-section of the roadway to be measured.

[0020] Furthermore, the scanning geometry parameters include: scanning distance, horizontal scanning angle, vertical scanning angle, horizontal angular resolution, and vertical angular resolution.

[0021] Furthermore, the specific details of calculating the radial wind speed at each measurement grid point using optical coherent detection technology based on the spatial coordinates and scanning geometric parameters of all measurement grid points are as follows:

[0022] For any measurement grid point The laser beam direction is determined based on the spatial coordinates, horizontal scanning angle, and vertical scanning angle of the measurement grid points; whereby... Indicates the grid index in the horizontal direction, and ; Indicates the grid index in the vertical direction, and ;

[0023] According to the laser beam direction, the laser beam is focused toward the measurement grid point, and the backscattered light signal from the measurement grid point is collected using optical coherent detection technology; the backscattered light signal is coherently mixed and balanced with the local oscillator light generated by splitting the laser beam to generate an analog electrical signal containing velocity information;

[0024] An analog-to-digital converter is used to convert analog electrical signals into digital electrical signals, and the Doppler frequency shift is extracted from the digital electrical signals.

[0025] The radial wind speed at the measurement grid point is calculated based on the Doppler frequency shift. .

[0026] Furthermore, the spatial vector projection relationship is as follows:

[0027] ;

[0028] in, Indicates measurement grid points The axial wind speed in the tunnel; The horizontal scanning angle; This is the vertical scanning angle.

[0029] Furthermore, the specific details of obtaining the total air volume of the roadway cross-section to be measured by performing a weighted integral on all measurement grid points based on the axial wind speed of each grid point and the area element it represents are as follows:

[0030] For each measurement grid point, the area micro-element represented by the measurement grid point is used as the weighting factor, and the product of the roadway axial wind speed of the measurement grid point and the weighting factor is calculated as the air volume contribution value of the measurement grid point.

[0031] The total air volume of the roadway section to be measured is obtained by summing the air volume contribution values ​​of all measurement grid points.

[0032] On the other hand, the present invention proposes a mine air volume measurement system based on optical cross-section scanning, which is used to implement the aforementioned mine air volume measurement method based on optical cross-section scanning. The system includes: an all-fiber coherent laser detection module, a two-dimensional optical scanning module, a signal processing module, and a wind field synthesis and integration calculation module.

[0033] The all-fiber coherent laser detection module is used to generate a laser beam and focus it onto a specified measurement grid point on the cross-section of the roadway to be measured. It performs coherent optical mixing and photoelectric conversion on the received echo signal through coherent optical mixing and balanced detection to generate an analog electrical signal containing velocity information.

[0034] The two-dimensional optical scanning module is used to discretize the cross-section of the roadway to be measured into several regular measurement grid points, and perform optical scanning on the cross-section of the roadway to be measured according to a preset scanning path to obtain the spatial coordinates and scanning geometric parameters of each measurement grid point.

[0035] The signal processing module is used to convert the analog electrical signal containing velocity information into a digital electrical signal through an analog-to-digital converter, and extract the Doppler frequency shift from the digital electrical signal based on the spatial coordinates and scanning geometric parameters of all measurement grid points, and then calculate the radial wind speed of each measurement grid point based on the Doppler frequency shift.

[0036] The wind field synthesis and integration module is used to convert the radial wind speed of each measurement grid point into the axial wind speed of the roadway at each measurement grid point; calculate the area micro-element represented by each measurement grid point according to the scanning geometric parameters; and then perform weighted integration on all measurement grid points in the roadway section to be measured according to the roadway axial wind speed and the area micro-element represented by each measurement grid point to obtain the total roadway air volume of the roadway section to be measured.

[0037] Furthermore, the all-fiber coherent laser detection module includes a light source unit, an optical path processing unit, an optical transceiver antenna unit, and a photoelectric conversion unit connected by optical fiber paths; and an auxiliary unit for stabilizing the optical path connections between the light source unit, the optical path processing unit, the optical transceiver antenna unit, and the photoelectric conversion unit.

[0038] The light source unit is used to generate a coherent detection laser beam;

[0039] The optical path processing unit is used to divide the coherent laser beam generated by the light source unit into local oscillator light and signal light, and to directionally transmit the signal light to the optical transceiver antenna unit; to receive the echo signal from the optical transceiver antenna unit, and to coherently mix the local oscillator light with the echo signal to obtain an interference light signal and send it to the photoelectric conversion unit.

[0040] The optical transceiver antenna unit is used to focus the signal light onto a designated measurement grid point on the cross-section of the roadway to be measured, and to collect the echo signal from the measurement grid point.

[0041] The photoelectric conversion unit is used to perform photoelectric conversion on the interference light signal to obtain an analog electrical signal containing speed information and transmit it to the signal processing module.

[0042] Furthermore, the two-dimensional optical scanning module includes: a scanning control unit and a scanning execution mechanism;

[0043] The scanning control unit, based on the measurement coordinate system of the cross-section of the roadway to be measured, discretizes the cross-section of the roadway to be measured into several regular measurement grid points, and presets the scanning path according to the spatial coordinates of the measurement grid points, thereby generating scanning control commands and sending them to the scanning execution mechanism; it records the spatial coordinates and scanning geometric parameters of each measurement grid point and simultaneously sends them to the signal processing module and the wind field synthesis and integration calculation module.

[0044] The scanning execution mechanism is used to deflect the laser beam generated by the all-fiber coherent laser detection module according to the received scanning control command, and control the laser spot formed by focusing the laser beam to traverse all measurement grid points sequentially according to the preset scanning path.

[0045] The beneficial effects of adopting the above technical solution are as follows:

[0046] This invention proposes a method and system for measuring mine air volume based on optical cross-sectional scanning. It is primarily used for non-contact, precise measurement of full-section air volume in confined spaces such as mine roadways and tunnels. It is particularly suitable for monitoring ventilation air volume in coal mines, metal mines, and various tunnel projects. It is mainly applied to the precise measurement of air volume in various ventilation roadways, including main intake roadways, main return air roadways, belt conveyor roadways, mining face roadways, and standard anemometer stations. Detailed analysis follows:

[0047] (1) Achieve true full-section accurate measurement: By discretizing the roadway cross section into a dense grid and scanning point by point, the inherent defect of the traditional method of "using points to represent the surface" is fundamentally solved, and the wind speed distribution in the complex roadway can be truly reflected.

[0048] (2) It breaks through the adaptability bottleneck of complex roadway environment: It adopts non-contact laser scanning method, which is not limited by complex conditions such as roadway cross-section shape and pipeline obstruction. It is particularly suitable for scenarios where traditional methods are difficult to apply, such as underground irregular roadways and multi-path bifurcation areas.

[0049] (3) Significantly improved measurement accuracy and reliability: Based on rigorous mathematical modeling and physical principles, the air volume is directly calculated by area weighted integral, avoiding the cumulative error caused by traditional empirical formulas and coefficient conversion, and the measurement accuracy is significantly improved.

[0050] (4) It has good engineering applicability: the method has a clear principle and a simple calculation model. It does not require the construction of a complex digital twin model or the reconstruction of a three-dimensional flow field, which makes it easy to achieve rapid and stable engineering applications in the underground environment. It provides reliable technical support for the real-time monitoring, intelligent control and disaster early warning of the mine ventilation system, and helps to improve the intelligent management level of mine safety production. Attached Figure Description

[0051] Figure 1 This is a flowchart of a mine ventilation measurement method based on optical cross-sectional scanning in this embodiment;

[0052] Figure 2 This is a structural diagram of a mine ventilation measurement system based on optical cross-sectional scanning in this embodiment;

[0053] Figure 3 This is a schematic diagram illustrating the principle of measuring wind speed across the entire cross-section of a roadway in this embodiment;

[0054] In the diagram: 1-Invalid measurement point; 2-Valid measurement point; 3-Gas extraction pipe; 4-Fire sprinkler pipe; 5-Yellow mud grouting pipe; 6-Compressed air pipe; 7-Area corresponding to the valid measurement point. Detailed Implementation

[0055] To facilitate understanding of this application, specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and embodiments. The following embodiments are illustrative of the invention but are not intended to limit its scope. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0056] Example 1:

[0057] This embodiment provides a method for measuring mine ventilation volume based on optical cross-sectional scanning, such as... Figure 1 As shown, the method specifically includes the following steps:

[0058] A measurement coordinate system is established for the cross-section of the roadway to be measured. Under this measurement coordinate system, the cross-section of the roadway to be measured is discretized by optical scanning to obtain the spatial coordinates and scanning geometric parameters of several measurement grid points.

[0059] The establishment of a measurement coordinate system for the cross-section of the roadway to be measured, and the discretization measurement of the cross-section of the roadway to be measured by optical scanning under this measurement coordinate system, to obtain the spatial coordinates and scanning geometric parameters of several measurement grid points, are as follows:

[0060] For any cross-section of the roadway to be measured, the origin of the coordinate system is the measurement reference point within that cross-section. Establish a spatial rectangular coordinate system This serves as the measurement coordinate system for the cross-section of the roadway to be measured; where... Both represent coordinate axes, and The positive direction of the axis is along the axis of the roadway to be measured and points in the expected downstream direction of the airflow. The positive direction of the axis is perpendicular to the axis of the roadway in the horizontal plane and points to the other side of the roadway. The positive direction of the axis points vertically upwards towards the roof of the tunnel.

[0061] The measurement reference point is the optical center of the device that is fixedly installed within the cross-section of the roadway to be measured and is used for all-fiber coherent laser detection of the cross-section of the roadway to be measured.

[0062] In this embodiment, the origin of the coordinate system is the optical center of the all-fiber coherent laser detection module of the laser Doppler velocimetry system (i.e., a mine air volume measurement system based on optical cross-section scanning), which is fixedly installed at approximately the center of the mine roadway cross-section. Establish a spatial rectangular coordinate system The all-fiber coherent laser detection module emits a laser beam towards the cross-section of the roadway to be measured and receives the echo signal. The echo signal is then coherently mixed and photoelectrically converted. The positive direction of the axis is along the tunnel axis and points in the expected downstream direction of the airflow. The positive direction of the axis is perpendicular to the tunnel axis in the horizontal plane and points to the other side of the tunnel. The positive axis points vertically upwards towards the tunnel roof, thus forming a right-handed coordinate system.

[0063] Based on the aforementioned measurement coordinate system, the cross-section of the roadway to be measured is discretized into... The measurement grid points are determined according to a set rule, and a scan path is generated; where Indicates the number of scan points in the horizontal direction. This indicates the number of scan points in the vertical direction.

[0064] Based on the generated scanning path, optical scanning is performed on the cross-section of the roadway to be measured, and the spatial coordinates and scanning geometric parameters of each measurement point on the cross-section of the roadway to be measured are obtained in sequence.

[0065] In this embodiment, a two-dimensional optical scanning module (using a deflectable wedge prism or reflector) sequentially points a laser beam to different positions on the cross-section of the roadway to be measured. This cross-section is perpendicular to the roadway axis. The plane of the axis controls the two-dimensional optical scanning module, ensuring that the laser focus's movement trajectory on the tunnel cross-section covers the entire area to be measured, and discretizes it into... A regular measurement grid of points.

[0066] The scanning geometry parameters include: scanning distance, horizontal scanning angle, vertical scanning angle, horizontal angular resolution, and vertical angular resolution.

[0067] In this embodiment, the scanning geometric parameters include: scanning distance. That is, the origin of the coordinate system The vertical distance to the tunnel cross-section is a known module installation parameter; measurement grid points. Corresponding horizontal scan angle (Azimuth); Grid points Corresponding vertical scan angle (Pitch angle); Horizontal angular resolution (Radian measure), determined by the angular stepping accuracy of the scanning module; vertical angular resolution. (Radian measure), determined by the angular stepping accuracy of the scanning module.

[0068] Based on the spatial coordinates and scanning geometric parameters of all measurement grid points, the radial wind speed of each measurement grid point is calculated point by point using optical coherent detection technology.

[0069] In this embodiment, for each measurement grid point The two-dimensional optical scanning module is controlled to position the laser focus at that point, and the radial wind speed at that point is measured using optical coherence detection technology. .

[0070] The specific details of calculating the radial wind speed at each measurement grid point using optical coherence detection technology, based on the spatial coordinates and scanning geometric parameters of all measurement grid points, are as follows:

[0071] For any measurement grid point The laser beam direction is determined based on the spatial coordinates, horizontal scanning angle, and vertical scanning angle of the measurement grid points; whereby... Indicates the grid index in the horizontal direction, and ; Indicates the grid index in the vertical direction, and .

[0072] According to the laser beam direction, the laser beam is focused toward the measurement grid point, and the backscattered light signal from the measurement grid point is collected using optical coherent detection technology; the backscattered light signal is coherently mixed and balanced with the local oscillator light generated by splitting the laser beam to generate an analog electrical signal containing velocity information.

[0073] An analog-to-digital converter is used to convert analog electrical signals into digital electrical signals, and the Doppler frequency shift is extracted from the digital electrical signals.

[0074] The radial wind speed at the measurement grid point is calculated based on the Doppler frequency shift. .

[0075] Based on the spatial vector projection relationship, the radial wind speed of each measurement grid point is converted into the axial wind speed of the roadway at each measurement grid point.

[0076] The spatial vector projection relationship is as follows:

[0077] (1)

[0078] in, Indicates measurement grid points The axial wind speed of the tunnel.

[0079] In this embodiment, based on the spatial vector projection relationship, for grid points Assume the laser beam direction is from the horizontal scanning angle and vertical scan angle The cosine of the angle between the unit vector of the laser beam direction and the unit vector of the roadway axis direction is jointly determined. Therefore, the coordinate transformation formula for the axial wind speed of the roadway is shown in formula (1).

[0080] Based on the scanning geometry parameters, calculate the area element represented by each measurement grid point.

[0081] Let the scanning distance be The formula for calculating the area micro-element is:

[0082] (2)

[0083] in, Indicates measurement grid points The area of ​​the micro-element.

[0084] Based on the axial wind speed of the roadway and the area element represented by each measurement grid point, a weighted integral is performed on all measurement grid points to obtain the total air volume of the roadway section to be measured.

[0085] The specific details of obtaining the total air volume of the roadway cross-section to be measured by performing a weighted integral on all measurement grid points based on the axial wind speed of each grid point and the area micro-element they represent are as follows:

[0086] For each measurement grid point, the area element represented by the measurement grid point is used as a weighting factor, and the product of the roadway axial wind speed of the measurement grid point and the weighting factor is calculated as the air volume contribution value of the measurement grid point.

[0087] The total air volume of the roadway section to be measured is obtained by summing the air volume contribution values ​​of all measurement grid points.

[0088] In this embodiment, due to the geometric characteristics of the scanning system (such as conical scanning), the same angular intervals are achieved at different locations on the tunnel cross-section. and The corresponding physical areas are not equal, as shown in formula (2), the area varies with the angle. Therefore, the axial wind speed of the roadway at each measurement grid point is... Multiply by the infinitesimal area represented by that point Then, by summing the products of all the measurement grid points, the total air volume passing through the entire tunnel cross-section can be obtained. :

[0089] (3)

[0090] in, This represents the summation over all valid measurement grid points in the horizontal and vertical directions; area infinitesimal element. The use of area micro-elements as weighting factors ensures that measuring points at different spatial locations contribute to the total air volume in proportion to the actual ventilation area they represent.

[0091] Example 2:

[0092] This embodiment provides a mine ventilation measurement system based on optical cross-sectional scanning, such as... Figure 2 As shown, the system includes: an all-fiber coherent laser detection module, a two-dimensional optical scanning module, a signal processing module, and a wind field synthesis and integration calculation module.

[0093] The all-fiber coherent laser detection module is used to generate a laser beam and focus it onto a designated measurement grid point on the cross-section of the roadway to be measured. It performs coherent optical mixing and photoelectric conversion on the received echo signal through coherent optical mixing and balanced detection to generate an analog electrical signal containing velocity information.

[0094] The all-fiber coherent laser detection module includes, in sequence, a light source unit, an optical path processing unit, an optical transceiver antenna unit, and a photoelectric conversion unit; and an auxiliary unit for stabilizing the optical path connection between the light source unit, the optical path processing unit, the optical transceiver antenna unit, and the photoelectric conversion unit.

[0095] The light source unit is used to generate a coherent laser beam.

[0096] In this embodiment, the light source unit uses a narrow linewidth continuous fiber laser to generate highly coherent probe light and integrates laser driving and temperature control circuits to ensure the stability of laser wavelength and power.

[0097] The optical path processing unit is used to divide the coherent laser beam generated by the light source unit into local oscillator light and signal light, and to directionally transmit the signal light to the optical transceiver antenna unit; to receive the echo signal from the optical transceiver antenna unit, and to coherently mix the local oscillator light with the echo signal to obtain an interference light signal and send it to the photoelectric conversion unit.

[0098] In this embodiment, the optical path processing unit is composed of all-fiber devices such as optical isolators, fiber beam splitters, fiber circulators, and fiber couplers. The optical isolator is placed after the laser to prevent back-reflected light from damaging the laser; the fiber beam splitter splits the light into local oscillator light and signal light; the fiber circulator enables directional transmission of the signal; and the fiber coupler completes coherent mixing of the local oscillator light and the signal light.

[0099] The optical transceiver antenna unit is used to focus the signal light onto a designated measurement grid point on the cross-section of the roadway to be measured, and to collect the echo signal from the measurement grid point.

[0100] In this embodiment, the optical transceiver antenna unit adopts an integrated transceiver optical antenna, and the front end of the optical antenna is integrated with a variable focus lens group, which is used to focus the laser on the target point and collect backscattered light.

[0101] The photoelectric conversion unit is used to perform photoelectric conversion on the interference light signal to obtain an analog electrical signal containing speed information and transmit it to the signal processing module.

[0102] In this embodiment, the photoelectric conversion unit uses a balanced detector.

[0103] The auxiliary unit is used to stabilize the optical path connection between the light source unit, the optical path processing unit, the optical transceiver antenna unit, and the photoelectric conversion unit.

[0104] In this embodiment, the auxiliary unit includes an optical fiber connector / connector and a polarization controller to ensure low-loss and stable optical path connection between the components and to optimize coherence efficiency.

[0105] In this embodiment, the all-fiber coherent laser detection module serves as the core of the system's physical sensing, responsible for generating the laser beam and extracting velocity information. Employing an all-fiber optical path design, the coherent laser beam generated by the narrow-linewidth continuous fiber laser is split into a local oscillator beam and a signal beam by a fiber beam splitter, laying the foundation for subsequent optical mixing and giving the system good electromagnetic interference resistance. An optical isolator prevents back-reflected light from damaging the laser. The local oscillator beam is guided to one input port of the fiber coupler; the signal beam is directionally transmitted by a fiber circulator to the transceiver integrated optical antenna. The signal beam is then focused onto the atmospheric aerosol at a designated measurement point by a variable-focus lens group integrated at the front end of the optical antenna, enabling precise focusing at different distances and ensuring efficient coupling of the echo signal. The generated backscattered echo signal is then received by the same optical antenna and transmitted back to the fiber optic circulator, and then directionally transmitted to another input port of the fiber optic coupler. In the fiber optic coupler, the local oscillator light and the echo signal are coherently mixed to generate an interference light signal containing Doppler frequency shift information. This interference light signal is sent to a balanced detector for photoelectric conversion, which effectively suppresses common-mode noise, improves the detection sensitivity of weak scattered signals, and finally outputs a differential analog electrical signal containing velocity information.

[0106] The two-dimensional optical scanning module is used to discretize the cross-section of the roadway to be measured into several regular measurement grid points, and perform optical scanning on the cross-section of the roadway to be measured according to a preset scanning path to obtain the spatial coordinates and scanning geometric parameters of each measurement grid point.

[0107] The two-dimensional optical scanning module includes a scanning control unit and a scanning execution mechanism.

[0108] The scanning control unit discretizes the cross-section of the roadway to be measured into several regular measurement grid points based on the measurement coordinate system of the cross-section of the roadway to be measured, and presets the scanning path according to the spatial coordinates of the measurement grid points, thereby generating scanning control commands and sending them to the scanning execution mechanism; it records the spatial coordinates and scanning geometric parameters of each measurement grid point and sends them to the signal processing module and the wind field synthesis and integration calculation module at the same time.

[0109] In this embodiment, the scanning control unit is an industrial computer or an embedded controller.

[0110] The scanning execution mechanism is used to deflect the laser beam generated by the all-fiber coherent laser detection module according to the received scanning control command, and control the laser spot formed by focusing the laser beam to traverse all measurement grid points sequentially according to the preset scanning path.

[0111] In this embodiment, the scanning actuator includes a drive motor and an optical deflection element. The drive motor can be implemented as a stepper motor or a servo motor. The optical deflection element is installed at the front end of the optical transceiver antenna unit of the all-fiber coherent laser detection module and can be implemented as a rotating wedge prism or a two-dimensional scanning galvanometer.

[0112] Specifically, the two-dimensional optical scanning module, as the system's spatial positioning actuator, is responsible for expanding point measurement into area measurement. This embodiment employs a scanning scheme based on a rotating wedge prism, precisely driven by a stepper motor. The prism's rotation causes the laser beam to produce a fixed deflection angle of 10°–30°. By controlling the continuous rotation of the prism, the laser focus forms a conical scanning trajectory on the tunnel cross-section, achieving full coverage of the cross-section. The scanning control unit (industrial computer) serves as the control center, presets the scanning path, and discretizes the cross-section into... A regular grid is formed, and the laser focus is controlled to traverse all grid points in sequence.

[0113] The signal processing module is used to convert the analog electrical signal containing velocity information into a digital electrical signal through an analog-to-digital converter, and extract the Doppler frequency shift from the digital electrical signal based on the spatial coordinates and scanning geometric parameters of all measurement grid points, and then calculate the radial wind speed of each measurement grid point based on the Doppler frequency shift.

[0114] In this embodiment, the high-speed real-time signal processing module serves as the system's information processing center, responsible for converting the raw analog signal into reliable wind speed data. Its core process is as follows: a high-speed analog-to-digital converter (ADC) performs high-fidelity digitization of the signal, converting the analog electrical signal from the all-fiber coherent laser detection module into a digital electrical signal; subsequently, a dedicated real-time signal processing pipeline built on an FPGA (Field-Programmable Gate Array) processes this digital signal. This processing includes, but is not limited to, digital filtering, Fast Fourier Transform (FFT), and spectral refinement analysis to accurately and with low latency extract the Doppler frequency shift, and to calculate the radial wind speed at the current measurement grid point in real time based on a physical model. In this embodiment, the FPGA, through an optimized parallel processing architecture, enables high-speed real-time execution of these algorithms to meet the needs of rapid measurement of mine wind fields.

[0115] The wind field synthesis and integration module is used to convert the radial wind speed of each measurement grid point into the axial wind speed of the roadway at each measurement grid point; calculate the area micro-element represented by each measurement grid point according to the scanning geometric parameters; and then perform weighted integration on all measurement grid points in the roadway section to be measured according to the roadway axial wind speed and the area micro-element represented by each measurement grid point to obtain the total roadway air volume of the roadway section to be measured.

[0116] In this embodiment, the wind field synthesis and integration calculation module, as the system's data fusion and calculation unit, is responsible for the final calculation and output of the wind volume. It is implemented using a software algorithm running on the system's main industrial control computer. The specific content of this algorithm is: receiving and storing the radial wind speed array from the FPGA. and its corresponding spatial angle array Based on the spatial vector projection relationship, the radial wind speed is converted into the axial wind speed. Based on the scanning geometry, calculate the area micro-element corresponding to each measurement grid point. Finally, the area-weighted integral algorithm is executed to calculate the total air volume of the roadway cross-section under test, completing the air volume synthesis from point to area.

[0117] In summary, the measurement system proposed in this embodiment follows a highly automated "transmission-scanning-reception-processing-integration" workflow, including:

[0118] (1) Optical emission and spatial positioning: The main control computer of the system synchronously controls two processes: First, it controls the laser to generate a detection laser, which is transmitted through the optical fiber to the optical antenna and focused by the lens group; Second, it controls the actuator (such as the rotating prism) in the two-dimensional optical scanning module to accurately position the laser focus to each measurement point on the tunnel cross section according to the preset grid sequence.

[0119] (2) Signal acquisition and coherent detection: The backscattered light carrying Doppler frequency shift generated by the interaction between the laser focus and the aerosol is received by the optical antenna, coherently mixed with the local oscillator light in the optical path, and finally converted into an analog electrical signal by the balanced detector.

[0120] (3) Real-time processing and wind speed extraction: After the analog electrical signal is digitized by the analog-to-digital converter (ADC) in the high-speed real-time signal processing module, it is sent to the FPGA of the module for real-time processing (including digital filtering, FFT and spectrum analysis) to accurately calculate the radial wind speed value of the current grid point. The result is uploaded to the main control industrial computer in real time.

[0121] (4) Cross-section scanning and air volume synthesis: The system traverses all measuring points to complete the cross-section scanning. The industrial control computer receives and stores the radial wind speed and its spatial coordinates. The radial wind speed is converted into the axial wind speed through coordinate transformation. The system performs weighted integration based on the area of ​​each grid point and finally outputs the accurate air volume value of the entire cross-section of the roadway.

[0122] Example 3:

[0123] This embodiment provides a specific implementation plan for a mine ventilation measurement method based on optical cross-sectional scanning. Through detailed formula derivation and data calculation, it fully demonstrates the entire process from raw signal acquisition to final ventilation output. The specific process is as follows:

[0124] (1) Configure the mine ventilation measurement system based on optical cross-section scanning proposed in Example 2.

[0125] A laser Doppler velocimetry system is used, with the emitted laser wavelength... The output power is 30-100mW (adjustable), and the spectral linewidth is less than 20kHz, meeting the safety requirements for human eyes.

[0126] Set the scan geometry parameters, including: scan radius: Horizontal scanning angle and vertical scan angle Range: 10°–30°; Angular resolution: , .

[0127] Based on the above angle range, such as Figure 3 As shown, the cross-section of the roadway to be measured is discretized into a regular grid of 10×10, with a theoretical number of 100 measurement points. The system can automatically identify and remove invalid measurement points 1 that are blocked by permanent obstacles such as roadway walls, pipelines, gas extraction pipes 3, fire sprinkler pipes 4, yellow mud grouting pipes 5, and compressed air pipes 6. In this embodiment, the number of valid measurement points 2 is 60.

[0128] (2) Data acquisition is carried out using the configured mine ventilation measurement system.

[0129] When a laser irradiates aerosol particles moving with the wind, a Doppler shift occurs. Detected through optical mixing and spectrum analysis techniques And calculate each grid point according to formula (1). radial wind speed :

[0130] (4)

[0131] In this embodiment, some measured data examples are as follows:

[0132] Grid point (15, 10): =1.25MHz, ≈0.97m / s;

[0133] Grid point (16, 10): =1.38MHz, ≈1.07m / s;

[0134] Grid point (15, 11): =1.42MHz, ≈1.10m / s.

[0135] (3) Air volume calculation model based on grid integral

[0136] The above measurement process is entirely based on the spatial rectangular coordinate system established in Example 1. For any measurement grid point The direction of the laser beam originates from the coordinate origin. Starting horizontal scan angle and vertical scan angle The only certainty is the intersection of the laser beam and the target tunnel cross-section. This refers to the actual measurement point. Based on the spatial vector projection relationship, the measurement point... radial wind speed at the location relative to the axial wind speed of the tunnel The conversion relationship is as described in formula (1) in Example 1.

[0137] Taking grid point (15, 10) as an example, assume the scanning angle corresponding to this point is: (Horizontal angle) (Vertical angle) ≈0.97 m / s. Therefore, the calculation process for the axial wind speed in the roadway at this point is as follows:

[0138] ≈1.10m / s (5)

[0139] Let the horizontal angular resolution be The vertical angular resolution is At scanning distance At that point, the arc length corresponding to the angular step is approximately projected onto the cross-section as the side length of a small rectangle. Therefore, the area of ​​each measurement grid point, i.e., the area corresponding to the effective measurement point, can be approximated as:

[0140] (6)

[0141] Taking grid point (15, 10) as an example, the angles must be in radians. .

[0142] (7)

[0143] The volumetric air volume of the roadway section to be measured is defined as the integral of the axial wind speed on the section. After discretization, it is expressed as the sum of the air volume of all effective grid points, as shown in formula (3).

[0144] Substituting formulas (1) and (2) into formula (3), we get:

[0145] (8)

[0146] After simplification Offset:

[0147] (9)

[0148] Calculate the constant term based on the scanning geometry parameters. :

[0149] (10)

[0150] In the practical application of this embodiment, the two-dimensional optical scanning module sums the values ​​of all 60 valid wind speed measurement points. The value of is assumed to be 225 m / s for the purpose of demonstrating the calculation process.

[0151] m 3 / s (11)

[0152] The above process clearly demonstrates that the total cross-sectional air volume can be obtained from the radial wind speed measurements at all measuring points, their corresponding azimuth angles, and the system's fixed scanning geometric parameters. It can be calculated directly.

[0153] To verify the measurement accuracy and engineering applicability of the method and system described in this invention, performance tests were conducted on a standard wind tunnel simulation platform. The specific process is as follows:

[0154] Setting up the test environment and conditions:

[0155] Experimental environment: ambient temperature (20±5)℃, relative humidity (50±10)%.

[0156] Simulated tunnel: Constructed with stainless steel plates, with a rectangular cross-section and a fixed area of ​​7.5m², ensuring smooth walls and a uniform and stable flow field.

[0157] Reference standard: A high-precision hot-wire anemometer that has been certified by a legal metrology institution is used as the wind speed reference, and its cross-sectional average wind speed and air volume are used as standard values.

[0158] Test conditions: Covered the common wind speed range in mines (1.0-8.0m / s), with a total of 5 wind speed levels.

[0159] Performance tests were conducted based on the set test environment and conditions. The measured wind speed and air volume data were compared with the standard values. The main results are shown in Table 1.

[0160] Table 1 Standard wind tunnel simulated tunnel test data

[0161]

[0162] Analysis of Table 1 shows that:

[0163] 1) Wind speed measurement accuracy: Test data shows that in the medium-to-high wind speed range above 1.5 m / s, the relative error of the device's wind speed measurement is consistently within 5.0%, and the relative error decreases as the wind speed increases, demonstrating good linearity and consistency. The absolute error under all operating conditions meets the preset technical specifications (when wind speed...). At that time, error .

[0164] 2) Airflow measurement accuracy: In terms of full-section airflow measurement, except for the low wind speed condition of 1.0 m / s, the relative error of airflow measurement under other conditions is better than ±5.0%. This proves that the method of cross-section scanning integration of the present invention can effectively overcome the fundamental error of the traditional single-point measurement "substituting a point for a surface", and realize high-precision direct airflow measurement.

[0165] 3) Performance in light winds: Under light wind conditions of 1.0 m / s and 1.5 m / s, the device can still maintain effective detection and measurement capabilities, with an absolute wind speed error of less than 0.1 m / s, which verifies the reliability of its high-sensitivity optical coherent detection module in low signal-to-noise ratio environments.

[0166] In summary, the method described in this invention demonstrates high accuracy and repeatability in standardized tests simulating mine ventilation environments, particularly excelling in the medium wind speed range, which is of utmost concern in engineering. It fully meets the technical requirements for accurate air volume measurement in mine ventilation safety monitoring.

[0167] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope defined by the present invention.

Claims

1. A method for measuring mine ventilation volume based on optical cross-sectional scanning, characterized in that, This method includes the following steps: Establish a measurement coordinate system for the cross-section of the roadway to be measured, and under this measurement coordinate system, perform discretization measurement of the cross-section of the roadway to be measured by optical scanning to obtain the spatial coordinates and scanning geometric parameters of several measurement grid points; Based on the spatial coordinates and scanning geometric parameters of all measurement grid points, the radial wind speed of each measurement grid point is calculated point by point using optical coherent detection technology; Based on the spatial vector projection relationship, the radial wind speed of each measurement grid point is converted into the axial wind speed of the roadway at each measurement grid point; Based on the scanning geometry parameters, calculate the area micro-element represented by each measurement grid point; Based on the axial wind speed of each measurement grid point and the area micro-element it represents, a weighted integral is performed on all measurement grid points in the cross-section of the roadway to be measured to obtain the total air volume of the roadway cross-section.

2. The method for measuring mine ventilation based on optical cross-sectional scanning according to claim 1, characterized in that, The establishment of a measurement coordinate system for the cross-section of the roadway to be measured, and the discretization measurement of the cross-section of the roadway to be measured by optical scanning under this measurement coordinate system, to obtain the spatial coordinates and scanning geometric parameters of several measurement grid points, are as follows: For any cross-section of the roadway to be measured, the origin of the coordinate system is the measurement reference point within that cross-section. Establish a spatial rectangular coordinate system This serves as the measurement coordinate system for the cross-section of the roadway to be measured; where... Both represent coordinate axes, and The positive direction of the axis is along the axis of the roadway to be measured and points in the expected downstream direction of the airflow. The positive direction of the axis is perpendicular to the axis of the roadway in the horizontal plane and points to the other side of the roadway. The positive direction of the axis points vertically upwards towards the tunnel roof; Based on the aforementioned measurement coordinate system, the cross-section of the roadway to be measured is discretized into... The measurement grid points are determined according to a set rule, and a scan path is generated; where Indicates the number of scan points in the horizontal direction. Indicates the number of scan points in the vertical direction; Based on the generated scanning path, optical scanning is performed on the cross-section of the roadway to be measured, and the spatial coordinates and scanning geometric parameters of each measurement point on the cross-section of the roadway to be measured are obtained in sequence.

3. The method for measuring mine ventilation based on optical cross-sectional scanning according to claim 2, characterized in that, The measurement reference point is the optical center of the device that is fixedly installed within the cross-section of the roadway to be measured and is used for all-fiber coherent laser detection of the cross-section of the roadway to be measured.

4. The method for measuring mine ventilation based on optical cross-sectional scanning according to claim 3, characterized in that, The scanning geometry parameters include: scanning distance, horizontal scanning angle, vertical scanning angle, horizontal angular resolution, and vertical angular resolution.

5. The method for measuring mine ventilation based on optical cross-sectional scanning according to claim 4, characterized in that, The specific details of calculating the radial wind speed at each measurement grid point using optical coherence detection technology, based on the spatial coordinates and scanning geometric parameters of all measurement grid points, are as follows: For any measurement grid point The laser beam direction is determined based on the spatial coordinates, horizontal scanning angle, and vertical scanning angle of the measurement grid points; whereby... Indicates the grid index in the horizontal direction, and ; Indicates the grid index in the vertical direction, and ; According to the laser beam direction, the laser beam is focused toward the measurement grid point, and the backscattered light signal from the measurement grid point is collected using optical coherent detection technology; the backscattered light signal is coherently mixed and balanced with the local oscillator light generated by splitting the laser beam to generate an analog electrical signal containing velocity information; An analog-to-digital converter is used to convert analog electrical signals into digital electrical signals, and the Doppler frequency shift is extracted from the digital electrical signals. The radial wind speed at the measurement grid point is calculated based on the Doppler frequency shift. .

6. The method for measuring mine ventilation based on optical cross-sectional scanning according to claim 5, characterized in that, The spatial vector projection relationship is as follows: ； in, Indicates measurement grid points The axial wind speed in the tunnel; The horizontal scanning angle; This is the vertical scanning angle.

7. The method for measuring mine ventilation based on optical cross-sectional scanning according to claim 6, characterized in that, The specific details of obtaining the total air volume of the roadway cross-section to be measured by performing a weighted integral on all measurement grid points based on the axial wind speed of each grid point and the area micro-element they represent are as follows: For each measurement grid point, the area micro-element represented by the measurement grid point is used as the weighting factor, and the product of the roadway axial wind speed of the measurement grid point and the weighting factor is calculated as the air volume contribution value of the measurement grid point. The total air volume of the roadway section to be measured is obtained by summing the air volume contribution values ​​of all measurement grid points.

8. A mine ventilation measurement system based on optical cross-sectional scanning, used to implement the mine ventilation measurement method based on optical cross-sectional scanning as described in any one of claims 1-7, characterized in that, The system includes: an all-fiber coherent laser detection module, a two-dimensional optical scanning module, a signal processing module, and a wind field synthesis and integration calculation module; The all-fiber coherent laser detection module is used to generate a laser beam and focus it onto a specified measurement grid point on the cross-section of the roadway to be measured. It performs coherent optical mixing and photoelectric conversion on the received echo signal through coherent optical mixing and balanced detection to generate an analog electrical signal containing velocity information. The two-dimensional optical scanning module is used to discretize the cross-section of the roadway to be measured into several regular measurement grid points, and perform optical scanning on the cross-section of the roadway to be measured according to the preset scanning path to obtain the spatial coordinates and scanning geometric parameters of each measurement grid point. The signal processing module is used to convert the analog electrical signal containing velocity information into a digital electrical signal through an analog-to-digital converter, and extract the Doppler frequency shift from the digital electrical signal based on the spatial coordinates and scanning geometric parameters of all measurement grid points, and then calculate the radial wind speed of each measurement grid point based on the Doppler frequency shift. The wind field synthesis and integration module is used to convert the radial wind speed of each measurement grid point into the axial wind speed of the roadway at each measurement grid point; calculate the area micro-element represented by each measurement grid point according to the scanning geometric parameters; and then perform weighted integration on all measurement grid points in the roadway section to be measured according to the roadway axial wind speed and the area micro-element represented by each measurement grid point to obtain the total roadway air volume of the roadway section to be measured.

9. The mine ventilation measurement system based on optical cross-sectional scanning according to claim 8, characterized in that, The all-fiber coherent laser detection module includes a light source unit, an optical path processing unit, an optical transceiver antenna unit, and a photoelectric conversion unit connected by optical fiber paths; and an auxiliary unit for stabilizing the optical path connections between the light source unit, the optical path processing unit, the optical transceiver antenna unit, and the photoelectric conversion unit. The light source unit is used to generate a coherent detection laser beam; The optical path processing unit is used to divide the coherent laser beam generated by the light source unit into local oscillator light and signal light, and to directionally transmit the signal light to the optical transceiver antenna unit; to receive the echo signal from the optical transceiver antenna unit, and to coherently mix the local oscillator light with the echo signal to obtain an interference light signal and send it to the photoelectric conversion unit. The optical transceiver antenna unit is used to focus the signal light onto a designated measurement grid point on the cross-section of the roadway to be measured, and to collect the echo signal from the measurement grid point. The photoelectric conversion unit is used to perform photoelectric conversion on the interference light signal to obtain an analog electrical signal containing speed information and transmit it to the signal processing module.

10. A mine ventilation measurement system based on optical cross-sectional scanning according to claim 9, characterized in that, The two-dimensional optical scanning module includes: a scanning control unit and a scanning execution mechanism; The scanning control unit, based on the measurement coordinate system of the cross-section of the roadway to be measured, discretizes the cross-section of the roadway to be measured into several regular measurement grid points, and presets the scanning path according to the spatial coordinates of the measurement grid points, thereby generating scanning control commands and sending them to the scanning execution mechanism; it records the spatial coordinates and scanning geometric parameters of each measurement grid point and simultaneously sends them to the signal processing module and the wind field synthesis and integration calculation module. The scanning execution mechanism is used to deflect the laser beam generated by the all-fiber coherent laser detection module according to the received scanning control command, and control the laser spot formed by focusing the laser beam to traverse all measurement grid points sequentially according to the preset scanning path.

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