Optimization method of trackside acoustic-infrared coupling monitoring array structure

Abstract

The invention relates to the technical field of trackside monitoring systems, and discloses an optimization method of a trackside acoustic-infrared coupling monitoring array structure. According to the method, the optimal structure parameters of the microphone array are obtained by combining the design basic criterion, the actual condition, the beam forming simulation and the optimal parameter design criterion of the microphone array, and the optimal structure parameters fully consider the response conditions between different sound sources and the microphone array; therefore, when the microphone array is utilized to acquire the sound signal of the target sound source, interference of other sound sources on the microphone array is avoided as much as possible, and the accuracy of the sound signal acquired by the microphone array is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of trackside monitoring systems, and more particularly, to an optimization method for a trackside acoustic-infrared coupled monitoring array structure. Background Art

[0002] The content of this section only provides background information related to the present invention, which may not constitute prior art.

[0003] A trackside acoustic monitoring system is a system that sets up a microphone array beside the train running track to obtain the sound signal of a sound source (such as a wheel pair bearing) in a non-contact measurement manner using the microphone array, and realizes fault diagnosis of the sound source after processing the sound signal. Among them, the structural parameters of the microphone array (such as the number of microphones, the distance between adjacent two microphones, etc.) are particularly important for accurately obtaining the sound signal of the sound source. Therefore, when designing the microphone array, it is necessary to reasonably set the structural parameters of the microphone array.

[0004] In the related design technology of the microphone array, usually, the range of the structural parameters of the microphone array is initially determined based on the basic design criteria of the microphone array, and then the final structural parameters of the microphone array are selected manually within the range of the structural parameters of the microphone array according to experience. In this way, it does not consider and analyze the response of different sound sources to the same microphone array according to the actual situation, so that the determined structural parameters of the microphone array may not be the optimal structural parameters, which may cause the sound signal of other sound sources to interfere with the microphone array when using the microphone array to collect the sound signal of a certain sound source, thereby affecting the accuracy of the obtained sound signal. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide an optimization method for a trackside acoustic-infrared coupled monitoring array structure to at least overcome the technical problem that it is difficult to accurately obtain the optimal structural parameters of the microphone array based on the basic design criteria of the microphone array.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] The present invention discloses an optimization method for a trackside acoustic-infrared coupled monitoring array structure, wherein the trackside acoustic-infrared coupled monitoring array structure includes a microphone array, and the microphone array includes a plurality of microphones arranged at intervals in sequence along the running direction of the train;

[0008] The optimization method includes the following steps:

[0009] Step S1. Based on the basic design criteria of the microphone array, obtain the initial structural parameters of the microphone array; the initial structural parameters include the initial number of microphones and the initial microphone spacing.

[0010] Step S2. Establish an actual trackside sound source model, and based on the actual trackside sound source model, determine the angle β between the sound source adjacent to the target sound source and the length direction of the microphone array when the target sound source passes through the microphone array.

[0011] Step S3. Based on beamforming simulation, the initial number of microphones, and the initial microphone spacing, starting from the smallest initial number of microphones, sequentially draw beamforming diagrams when the number of microphones increases from small to large and the microphone spacing increases from the smallest to the largest, and determine the optimal structural parameters of the microphone array according to the beamforming diagrams, the angle β, and the optimal parameter design criteria; among them, the optimal structural parameters include the optimal number of microphones and the optimal microphone spacing.

[0012] Further, the optimal parameter design criteria include: in the beamforming diagram, the half-power main lobe width is as narrow as possible, the sidelobe level is as low as possible, and the zero point position is as close as possible to the angle β.

[0013] Further, in Step S2, the angle β is calculated based on the spacing between two adjacent sound sources and the longitudinal distance between the actual microphone array and the target sound source.

[0014] Further, the beamforming diagram includes a beam direction diagram and its directional pattern gain, and the beam direction diagram and its directional pattern gain are drawn based on the microphone array response vector and the beam weighting vector.

[0015] Further, the trackside acoustic-infrared coupling monitoring array structure further includes an infrared camera, and the infrared camera is arranged at the microphone array.

[0016] The optimization method further includes:

[0017] Step S4. Determine the optimal setting parameters of the infrared camera according to the imaging principle of the infrared camera and the response characteristics of the infrared camera; among them, the optimal setting parameters include the longitudinal distance from the infrared camera to the target sound source and the minimum exposure time when the infrared camera does not have smear.

[0018] Further, in Step S4, the optimal setting parameters of the infrared camera are determined through the following process:

[0019] Let the resolution of the infrared camera be W×H, the focal length be F, and the width of the imaging range be w; let the longitudinal distance from the infrared camera to the target sound source be l c ; it can be obtained that:

[0020]

[0021] Meanwhile, the response characteristic of the infrared camera and the longitudinal distance l from the infrared camera to the target sound source c are related as follows:

[0022]

[0023] In the above two formulas: p is the actual distance of the shooting range corresponding to each pixel point of the infrared camera; T Δ is the minimum exposure time for the infrared camera not to have smear; v max is the maximum running speed of the train when it passes by the infrared camera.

[0024] Furthermore, the trackside acoustic-infrared coupling monitoring array structure further includes a triggering device, and the triggering device is located upstream of the microphone array and the infrared camera;

[0025] The optimization method further includes:

[0026] Step S5. Determine the minimum relative distances between the triggering device and the microphone array and the infrared camera respectively according to the triggering response times of the triggering device, the microphone array, and the infrared camera, and the running speed of the train.

[0027] Furthermore, in step S5, the minimum relative distances between the triggering device and the microphone array and the infrared camera are determined by the following calculation formulas:

[0028] l m >(t c +t m )v max

[0029] l h >(t c +t h )v max

[0030] In the above two formulas: l m is the minimum relative distance between the triggering device and the microphone array; l n is the minimum relative distance between the triggering device and the infrared camera; t c is the response time of the triggering device; t m is the triggering response time of the microphone array; t h is the triggering response time of the infrared camera; v max is the maximum speed of the train when it passes by the triggering device.

[0031] The technical solution of the embodiment of the present invention has at least the following advantages and beneficial effects:

[0032] 1. The present invention combines the basic design criteria, actual situation, beamforming simulation, and optimal parameter design criteria of the microphone array to obtain the optimal structural parameters of the microphone array. These optimal structural parameters fully consider the response between different sound sources and the microphone array, which is beneficial to avoiding interference from other sound sources to the microphone array as much as possible when using the microphone array to acquire the sound signal of the target sound source, thereby helping to improve the accuracy of the sound signal obtained by the microphone array.

[0033] 2. The present invention adds an infrared camera to cooperate with the microphone array to form a trackside acoustic-infrared coupled monitoring array structure, which can not only simultaneously acquire the sound signal and temperature information of the sound source, but also improve the quality of the thermal imaging pictures obtained by the infrared camera by optimizing the set parameters of the infrared camera.

[0034] 3. The present invention arranges a trigger device upstream of the microphone array and the infrared camera and optimizes the installation position of the trigger device, which is beneficial to the microphone array and the infrared camera to timely acquire the sound signal and thermal imaging pictures of the target sound source when the target sound source on the train passes through the microphone array and the infrared camera, thereby ensuring the fusion of the sound and temperature signals and guaranteeing the accuracy of the spatio-temporal registration of multi-source signals. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a flowchart of the optimization method for the trackside acoustic-infrared coupled monitoring array structure provided by the embodiment of the present invention;

[0036] Figure 2 is a schematic diagram of the parametric model of the trackside microphone array provided by the embodiment of the present invention;

[0037] Figure 3 is the vibration mode diagram of the wheel pair bearing at different orders; where Figure 3 (a) is the 1st-order vibration mode diagram of the wheel pair bearing, Figure 3 (b) is the 2nd-order vibration mode diagram of the wheel pair bearing, Figure 3 (c) is the 3rd-order vibration mode diagram of the wheel pair bearing, Figure 3 (d) is the 5th-order vibration mode diagram of the wheel pair bearing;

[0038] Figure 4 is a schematic diagram of the actual trackside sound source model provided by the embodiment of the present invention;

[0039] Figure 5 (a) and Figure 5 (b) are respectively the beam pattern and its pattern gain when the number of microphones is 4 and the microphone spacing increases from 0.01 m to 0.06 m;

[0040] Figure 6(a) and Figure 6 (b) are respectively the beam pattern and its pattern gain when the number of microphones is 5 and the microphone spacing increases from 0.01 m to 0.06 m.

[0041] Figure 7 (a) and Figure 7 (b) are respectively the beam pattern and its pattern gain when the number of microphones is 6 and the microphone spacing increases from 0.01 m to 0.06 m.

[0042] Figure 8 is the imaging principle diagram of the infrared camera. Detailed implementation manners

[0043] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the detailed implementation manners. The same reference numerals in the drawings represent the same components. It should be noted that the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the described embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0044] Compared with the embodiments shown in the drawings, the feasible implementation manners within the scope of protection of the present invention may have fewer components, have other components not shown in the drawings, different components, differently arranged components or differently connected components, etc. In addition, two or more components in the drawings may be implemented in a single component, or a single component shown in the drawings may be implemented as multiple separate components.

[0045] The embodiments of the present invention disclose an optimization method for a trackside acoustic-infrared coupled monitoring array structure, in order to obtain the optimal structural parameters of the microphone array according to the basic design criteria, actual situation and beamforming simulation of the microphone array.

[0046] Among them, the trackside acoustic-infrared coupled monitoring array structure described in this embodiment at least includes a microphone array arranged beside the train operation track, and the microphone array further includes a plurality of microphones arranged at intervals in sequence along the running direction of the train. Among them, when a certain sound source on a running train passes by the microphone array (that is, is aligned with the microphone array), the microphone array can collect the sound signal of the sound source in real time. Among them, in this embodiment, the sound source passing by the microphone array and for which the sound signal is collected is defined as the target sound source.

[0047] It is worth noting that referring to Figure 2 and Figure 4As shown, in this embodiment, the sound source described can be the wheel pair bearings on the bogies of the train. Among them, for a known train, a single car usually includes two relatively arranged bogies, and each side of each bogie includes two wheel pair bearings. That is to say, in the case of taking the wheel pair bearings as the sound sources, there are a total of four sound sources on the same side of a single car.

[0048] Moreover, for the microphone array located on one side of the train, when using this microphone array to obtain the sound signal of the target sound source among the four sound sources on the same side of a single car, since the bogies of different cars are far apart, the interference of the sound sources on other cars to the microphone array can be ignored. That is to say, when using this microphone array to obtain the sound signal of the target sound source among the four sound sources on the same side of a single car, only the other three sound sources on the current car may interfere with the microphone array, affecting the accuracy of the sound signal obtained by the microphone array. Therefore, the optimization method disclosed in this embodiment will take the case where there are four sound sources on the same side of a single car as an example to optimize the structural parameters of the microphone array to determine the optimal structural parameters of the microphone array.

[0049] Figure 1 Fig. shows the flow chart of the optimization method for the trackside acoustic-infrared coupling monitoring array structure disclosed in this embodiment. As Figure 1 shown, the optimization method disclosed in this embodiment may include the following steps:

[0050] Step S1. Establish a parameterized model of the trackside microphone array, and based on the basic design criteria of the microphone array, obtain the initial structural parameters of the microphone array. Among them, the initial structural parameters of the microphone array may include the initial number of microphones, the initial microphone spacing, the longitudinal distance between the initial microphone array and the target sound source, and the vertical distance between the initial microphone array and the target sound source, etc.

[0051] Among them, Figure 2 Fig. shows the parameterized model of the trackside microphone array described in this embodiment. Combining Figure 2 shown, the microphone spacing described throughout this embodiment refers to: the spacing between two adjacent microphones in the microphone array.

[0052] The basic design criteria of the microphone array generally involve the Nyquist spatial sampling theorem, Morse acoustic theory, and far-field conditions, etc.

[0053] Generally speaking, the initial number of microphones in the initial structural parameters of the microphone array can be determined according to the number of sound sources. Define the initial number of microphones as m, then: m ≥ the number of sound sources. For example, in this embodiment, in the case where the sound source is the wheel pair bearing and there are a total of four wheel pair bearings as sound sources on the same side of a single car, initially determine that the initial number of microphones m ≥ 4.

[0054] Meanwhile, based on the fact that under far-field conditions, the sound waves emitted by the sound source can be approximately regarded as plane waves. Therefore, the microphone array and the target sound source can be arranged in a horizontal plane at the same height. That is, assuming that the vertical distance between the initial microphone array and the target sound source is defined as h, then: h = 0

[0055] According to the Nyquist spatial sampling theorem, the initial microphone spacing in the microphone array can be preliminarily determined. Specifically, the calculation formula for the microphone spacing is:

[0056]

[0057] In the above formula (1): d is the microphone spacing; λ min is the shortest wavelength of the sound waves emitted by the sound source, and where c is the speed of sound, generally taken as 340 m / s; f max is the maximum natural frequency of the sound waves emitted by the sound source.

[0058] According to the far-field conditions, the longitudinal distance between the initial microphone array and the target sound source can be preliminarily determined. Specifically, the calculation formula for the longitudinal distance between the microphone array and the target sound source is:

[0059]

[0060] In the above formula (2): l is the longitudinal distance between the microphone array and the target sound source; L a is the length of the microphone array, and L a = d(m - 1), where d is the microphone spacing and m is the number of microphones.

[0061] Combining the above formulas (1) and (2), it can be seen that only the maximum natural frequency f of the sound waves emitted by the sound source needs to be determined max , so as to calculate the shortest wavelength λ of the sound waves emitted by the sound source according to this maximum natural frequency f max , and then the initial microphone spacing and the longitudinal distance between the initial microphone array and the target sound source can be calculated. min Among them, when the sound source is a wheel pair bearing, there are at least the following two ways to determine the maximum natural frequency f of the sound source

[0062] The first is to calculate according to the bearing natural frequency calculation formula, where the bearing natural frequency calculation formula is expressed as: max The first one is to calculate according to the bearing natural frequency calculation formula, where the bearing natural frequency calculation formula is expressed as:

[0063] The first way is to calculate according to the bearing natural frequency calculation formula, in which the bearing natural frequency calculation formula is expressed as:

[0064]

[0065] In the above formula (3): fn is the natural frequency; m n is the order of the natural frequency, and n = 2, 3.....; D is the diameter of the neutral axis of the raceway cross-section; E is the modulus of elasticity; I is the moment of inertia of the raceway cross-section; g is the acceleration due to gravity; ρ is the material density; S is the cross-sectional area of the raceway.

[0066] Second, it is determined by using finite element simulation. For example, referring to Figure 3 as shown, which shows the vibration mode diagrams of the axlebox bearings in different orders obtained after finite element simulation analysis of the axlebox bearings in this embodiment. Among them, Figure 3 (a) is the 1st-order vibration mode diagram of the axlebox bearing, Figure 3 (b) is the 2nd-order vibration mode diagram of the axlebox bearing, Figure 3 (c) is the 3rd-order vibration mode diagram of the axlebox bearing, Figure 3 (d) is the 5th-order vibration mode diagram of the axlebox bearing.

[0067] From Figure 3 it can be roughly determined that the natural frequency of the axlebox bearing in the 1st - 2nd order vibration modes is about 1800 Hz, and the natural frequency in the 2nd - 5th order vibration modes is between 2000 - 3000 Hz. Therefore, it is concluded that the maximum natural frequency of the axlebox bearing is approximately 3000 Hz. On this basis, combined with formula (1), it can be known that in this microphone array, the initial microphone spacing d ≤ 0.06 m.

[0068] Step S2. On the basis of determining the initial structural parameters of the microphone array in step S1, establish an actual trackside sound source model, and based on the actual trackside sound source model, determine the angle β between the sound source adjacent to the target sound source and the longitudinal direction of the microphone array when the target sound source passes through the microphone array.

[0069] Among them, the actual trackside sound source model can be understood as the model of the actual sound source reaching the microphone array. Among them, at least the number and spatial position of the sound sources, the spacing between two adjacent sound sources, and the longitudinal distance between the actual microphone array and the target sound source and other information can be obtained from the actual trackside sound source model.

[0070] Among them, the number of the above-mentioned sound sources and the spacing between two adjacent sound sources can be confirmed according to the train structure parameters and the actual operating environment, etc.

[0071] For example, as Figure 4 shown, taking a certain train as an example, combined with the foregoing, there are a total of four axlebox bearings as sound sources on the same side of a single car body. Thus, it can be determined that the number of sound sources is 4, the spacing between two axlebox bearings in the same bogie of a single car body is 2.5 m, and the spacing between the axlebox bearings adjacent to each other in the two bogies of a single car body is 4 m.

[0072] The longitudinal distance between the actual microphone array and the target sound source is determined based on the longitudinal distance between the initial microphone array and the target sound source initially calculated in step S1, and can be reasonably arranged in combination with the on-site environment. For example, in this embodiment, the longitudinal distance between the actual microphone array and the target sound source is set to 1.5 m.

[0073] Meanwhile, Figure 4 The shown actual trackside sound source model also shows the positions of the microphone array relative to the sound source at different times. For example, in the running direction of the train, the four wheel pair bearings on the same side of a single car as the sound sources are defined as the first sound source, the second sound source, the third sound source, and the fourth sound source respectively. Then, the first sound source, the second sound source, the third sound source, and the fourth sound source will pass by the microphone array at times t1, t2, t3, and t4 respectively.

[0074] Furthermore, at time t1, the first sound source passes by the microphone array. At this time, the first sound source is used as the target sound source, and the second sound source is adjacent to this target sound source. After calculation, the angle between the second sound source and the length direction of the microphone array is 149°; correspondingly, at time t2, the second sound source passes by the microphone array. At this time, the second sound source is used as the target sound source, and the first sound source and the third sound source are adjacent to this target sound source. After calculation, the angle between the first sound source and the length direction of the microphone array is 31°, and the angle between the third sound source and the length direction of the microphone array is 159°; and so on. Only by obtaining the distance between two adjacent sound sources and the longitudinal distance between the actual microphone array and the target sound source, the angle β between the sound source adjacent to the target sound source and the length direction of the microphone array can be calculated when the target sound source passes by the microphone array.

[0075] Step S3. Based on beamforming simulation, and the initial number of microphones and the initial microphone spacing initially determined in step S1, starting from the smallest initial number of microphones, beamforming diagrams are successively drawn when the number of microphones increases from small to large and the microphone spacing increases from the smallest to the largest. And according to the beamforming diagrams, the angle β between the sound source adjacent to the target sound source and the length direction of the microphone array, and the optimal parameter design criterion, the optimal structural parameters of the microphone array are determined; wherein, the optimal structural parameters include the optimal number of microphones and the optimal microphone spacing.

[0076] It should be noted that in actual operation, when the beamforming diagram that can obtain the optimal structural parameters is drawn, the drawing of the beamforming diagram can be stopped, that is, the determination of the optimal structural parameters can be stopped.

[0077] In this embodiment, the beamforming diagram can further include the beam direction diagram and its directional diagram gain.

[0078] Among them, the beam pattern and its pattern gain can be plotted based on the microphone array response vector and the beam weighting vector.

[0079] Furthermore, the microphone array response vector is expressed as:

[0080]

[0081] The beam weighting vector is expressed as:

[0082]

[0083] In the above equations (4) and (5): f max is the maximum natural frequency of the sound wave emitted by the sound source; m is the number of microphones, M is the maximum number of microphones; d is the microphone spacing; θ is the microphone array response angle, and θ ranges from 0 to 180°, which is self-matched and searched by the microphone array; c is the speed of sound; θ 0 is the incident angle of the sound wave emitted by the target sound source incident on the microphone array. Generally, θ 0 = 90°; T represents the transpose operation.

[0084] Furthermore, the optimal parameter design criteria in this embodiment specifically include: 1. In the beamforming pattern, the half-power main lobe width is as narrow as possible to ensure the highest possible beam angle resolution; 2. In the beamforming pattern, the sidelobe level is as low as possible; 3. In the beamforming pattern, the null position is as close as possible to the other strong interfering sound sources (i.e., the sound sources adjacent to the target sound source), that is, the null position is as close as possible to the included angle β obtained in the previous step S2.

[0085] Among them, the half-power main lobe width refers to the main lobe range where the gain is above -3dB; the sidelobe level is based on the first sidelobe level; the null position refers to the node between two lobes, and the signal gain at the null position is very low.

[0086] Exemplarily, in combination with the foregoing, in an application scenario with a total of four sound sources on the same side of a single carriage, the following parameters are determined through steps S1 and S2 in the optimization method disclosed in this embodiment:

[0087] The maximum natural frequency f of the sound wave emitted by the sound source max = 3000Hz; the initial number of microphones m ≥ 4; the initial microphone spacing d ≤ 0.06m.

[0088] In this embodiment, it is assumed that the minimum microphone spacing is 0.01m, and the microphone spacing increases from 0.01m, 0.02m, 0.03m, 0.04m, 0.05m to 0.06m in sequence. At the same time, it is assumed that the incident angle θ of the sound wave emitted by the target sound source incident on the microphone array 0= 90°; the speed of sound c = 340 m / s.

[0089] Based on the beamforming simulation, part of the beamforming diagrams obtained by plotting are as Figures 5 to 7 shown. Among them, Figure 5 (a) and Figure 5 (b) respectively show the beam direction diagrams and their pattern gains when the number of microphones is 4 and the microphone spacing increases from 0.01 m to 0.06 m. Figure 6 (a) and Figure 6 (b) respectively show the beam direction diagrams and their pattern gains when the number of microphones is 5 and the microphone spacing increases from 0.01 m to 0.06 m. Figure 7 (a) and Figure 7 (b) respectively show the beam direction diagrams and their pattern gains when the number of microphones is 6 and the microphone spacing increases from 0.01 m to 0.06 m.

[0090] From the Figures 5 to 7 shown beamforming diagrams, it can be seen that the half-power main lobe width becomes narrower as the number of microphones and the microphone spacing increase. The sidelobe level is around -20 dB, but when the number of microphones is 5 and the microphone spacing is 0.05 m, the sidelobe level has the lowest value, and the zero positions at this time are closer to 31°, 149°, and 159°. Therefore, combining the aforementioned optimal parameter design criteria, it can be concluded that the optimal structural parameters of the microphone array are: the number of microphones is 5, and the microphone spacing is 0.05 m.

[0091] It can be seen that the optimization method disclosed in this embodiment combines the basic design criteria, actual situation, beamforming simulation, and optimal parameter design criteria of the microphone array to obtain the optimal structural parameters of the microphone array. These optimal structural parameters fully consider the response between different sound sources and the microphone array, so it is beneficial to avoid interference from other sound sources to the microphone array as much as possible when using the microphone array to acquire the sound signal of the target sound source, thereby helping to improve the accuracy of the sound signal acquired by the microphone array.

[0092] It is worth mentioning that during the actual operation of the train, for sound sources such as wheel sets and bearings, under the excitation of high-speed rotation and wheel-rail interaction, the internal vibration, sound, and temperature coupling effects of the sound source lead to the mutual correlation of temperature-vibration-sound information. Therefore, in addition to accurately acquiring the sound signal of the sound source to ensure the completeness of the sound, there is also a need to acquire the temperature information of the sound source. However, there is no technology in the existing art that can synchronously collect the sound and temperature of the sound source.

[0093] To this end, the trackside acoustic-infrared coupled monitoring array structure described in this embodiment further includes an infrared camera, which is disposed at the microphone array. When a sound source passes by the microphone array and the microphone array acquires the sound signal of the target sound source, the infrared camera can synchronously acquire the thermal imaging picture of the target sound source, and thereby obtain the temperature information of the target sound source.

[0094] Among them, in order to ensure the quality of the thermal imaging pictures obtained by the infrared camera, the optimization method disclosed in this embodiment further includes:

[0095] Step S4. Determine the optimal setting parameters of the infrared camera according to the imaging principle of the infrared camera and the response characteristics of the infrared camera; among them, the optimal setting parameters of the infrared camera include the longitudinal distance from the infrared camera to the target sound source, and the minimum exposure time when the infrared camera does not have smear.

[0096] In step S4, the optimal setting parameters of the infrared camera can be determined through the following process:

[0097] Let the resolution of the infrared camera be W×H, the focal length be F, and the width of the imaging range be w; at the same time, let the longitudinal distance from the infrared camera to the target sound source be l c ;

[0098] According to the infrared camera imaging principle diagram as Figure 8 shown, it can be obtained that:

[0099]

[0100] At the same time, the response characteristics of the infrared camera and the longitudinal distance l from the infrared camera to the target sound source c have the following relationship:

[0101]

[0102] In the above formulas (7) and (8): p is the actual distance of the shooting range corresponding to each pixel point of the infrared camera; T Δ is the minimum exposure time when the infrared camera does not have smear; v max is the maximum running speed of the train when passing by the infrared camera.

[0103] It can be seen that by combining formulas (6), (7) and (8), based on the known resolution, focal length, width of the imaging range of the infrared camera, and the maximum running speed of the train when passing by the infrared camera, the longitudinal distance from the infrared camera to the target sound source and the minimum exposure time when the infrared camera does not have smear can be calculated, which is conducive to the infrared camera to obtain high-quality thermal imaging pictures of the target sound source.

[0104] It should be noted that in this embodiment, by adding an infrared camera to cooperate with the microphone array to form a trackside acoustic-infrared coupled monitoring array structure, it is not only possible to simultaneously obtain the sound signal and temperature information of the sound source, but also by optimizing the setting parameters of the infrared camera, it is beneficial to improve the quality of the thermal imaging pictures obtained by the infrared camera.

[0105] On the other hand, in order to facilitate the microphone array and the infrared camera at the microphone array to timely obtain the sound signal and thermal imaging picture of the target sound source when the target sound source on the train passes by the microphone array and the infrared camera at the microphone array, the trackside acoustic-infrared coupled monitoring array structure described in this embodiment may further include a trigger device. Among them, the trigger device is arranged beside the track where the train runs and is located upstream of the microphone array and the infrared camera.

[0106] That is to say, during the actual operation of the train, the target sound source on the train will first pass through the trigger device and then pass through the microphone array and the corresponding infrared camera. Among them, when the target sound source passes through the trigger device, the trigger device can send a trigger signal to the corresponding microphone array and infrared camera to prompt the corresponding microphone array and infrared camera to be ready to obtain the sound signal and thermal imaging picture of the target sound source, so as to facilitate the microphone array and the infrared camera to timely obtain the sound signal and thermal imaging picture of the target sound source when the target sound source on the train passes through the corresponding microphone array and infrared camera.

[0107] Among them, the trigger device can be but is not limited to a magnetic steel trigger, a laser trigger, etc.

[0108] In order to achieve the above functions, the setting position of the trigger device is particularly important. For this reason, the optimization method disclosed in this embodiment further includes:

[0109] Step S5. Determine the minimum relative distances between the trigger device and the microphone array and the infrared camera respectively according to the trigger response times of the trigger device, the microphone array, and the infrared camera, and the running speed of the train.

[0110] In step S5, the minimum relative distances between the trigger device and the microphone array and the infrared camera respectively can be determined by the following calculation formulas:

[0111] l m >(t c +t m )v max Equation (9)

[0112] l h >(t c +t h )v max Equation (10)

[0113] In the above formulas (9) and (10): l m is the minimum relative distance between the triggering device and the microphone array; l n is the minimum relative distance between the triggering device and the infrared camera; t c is the reaction time of the triggering device; t m is the triggering reaction time of the microphone array; t h is the triggering reaction time of the infrared camera; v max is the maximum speed of the train when passing the triggering device.

[0114] It should be noted that in this embodiment, by arranging the triggering device upstream of the microphone array and the infrared camera and optimizing the installation position of the triggering device, when the target sound source on the train passes by the microphone array and the infrared camera, the microphone array and the infrared camera can timely acquire the sound signal and the thermal imaging picture of the target sound source, thereby ensuring the fusion of the sound and temperature signals and guaranteeing the accuracy of the spatio-temporal registration of the multi-source signals.

[0115] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for optimizing the structure of a trackside acoustic-infrared coupling monitoring array, characterized in that: The trackside acoustic-infrared coupling monitoring array structure includes a microphone array, and the microphone array includes a plurality of microphones arranged in sequence and at intervals along the running direction of the train; The optimization method comprises the following steps: Step S1. Based on the basic design criteria of the microphone array, obtaining initial structural parameters of the microphone array; the initial structural parameters include the initial number of microphones and the initial microphone spacing; Step S2. Establishing an actual trackside sound source model, and based on the actual trackside sound source model, determining an angle β between a sound source adjacent to the target sound source and the length direction of the microphone array when the target sound source passes through the microphone array; Step S3. Based on the beamforming simulation, the initial number of microphones and the initial microphone spacing, starting from the smallest initial number of microphones, the beamforming diagrams are sequentially drawn when the number of microphones increases from small to large and the microphone spacing increases from minimum to maximum, and the optimal structural parameters of the microphone array are determined according to the beamforming diagram, the angle β, and the optimal parameter design criteria; wherein the optimal structural parameters include the optimal number of microphones and the optimal microphone spacing.

2. The method for optimizing the trackside acoustic-infrared coupling monitoring array structure according to claim 1, characterized in that: The optimal parameter design criteria include: in the beamforming diagram, the half-power main lobe width is as narrow as possible, the side lobe level is as low as possible, and the zero point position is as close to the angle β as possible.

3. The method for optimizing the trackside acoustic-infrared coupling monitoring array structure according to claim 1, characterized in that: In step S2, the angle β is calculated based on the distance between two adjacent sound sources and the longitudinal distance between the actual microphone array and the target sound source.

4. The method for optimizing the trackside acoustic-infrared coupling monitoring array structure according to claim 1, characterized in that: The beamforming diagram includes a beam pattern and a pattern gain thereof, and the beam pattern and the pattern gain thereof are drawn based on a microphone array response vector and a beam weighting vector.

5. The method for optimizing the trackside acoustic-infrared coupling monitoring array structure according to claim 1, characterized in that: The trackside acoustic-infrared coupling monitoring array structure further includes an infrared camera, which is arranged at the microphone array; The optimization method further comprises: Step S4. Determine the optimal setting parameters of the infrared camera according to the imaging principle of the infrared camera and the response characteristics of the infrared camera; wherein the optimal setting parameters include the longitudinal distance from the infrared camera to the target sound source, and the minimum exposure time of the infrared camera without ghosting.

6. The method for optimizing the trackside acoustic-infrared coupling monitoring array structure according to claim 4 is characterized in that: In step S4, the optimal setting parameters of the infrared camera are determined by the following process: Assume that the resolution of the infrared camera is W×H, the focal length is F, and the width of the imaging range is w; Assume that the longitudinal distance from the infrared camera to the target sound source is l c ; we can get: At the same time, the response characteristics of the infrared camera are related to the longitudinal distance l from the infrared camera to the target sound source. c The relationship is as follows: In the above two formulas: p is the actual distance of the shooting range corresponding to each pixel of the infrared camera; T Δ v is the minimum exposure time for the infrared camera to avoid smearing; max It is the maximum running speed of the train when passing the infrared camera.

7. The method for optimizing the trackside acoustic-infrared coupling monitoring array structure according to claim 5, characterized in that: The trackside acoustic-infrared coupling monitoring array structure also includes a trigger device, which is located upstream of the microphone array and the infrared camera; The optimization method further comprises: Step S5. Determine the minimum relative distances between the trigger device and the microphone array and the infrared camera, respectively, based on the trigger reaction times of the trigger device, the microphone array, and the infrared camera, as well as the running speed of the train.

8. The method for optimizing the trackside acoustic-infrared coupling monitoring array structure according to claim 7 is characterized in that: In step S5, the minimum relative distances between the trigger device and the microphone array and the infrared camera are determined by the following calculation formula: l m >(t c +t m )v max l h >(t c +t h )v max In the above two formulas: m is the minimum relative distance between the trigger device and the microphone array; l n is the minimum relative distance between the trigger device and the infrared camera; t c is the reaction time of the trigger device; t m is the trigger reaction time of the microphone array; t h is the trigger reaction time of the infrared camera; v max It is the maximum speed of the train when it passes the trigger device.

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