A vehicle vibration identification device and judgment method based on multipath information fusion

Abstract

The present invention discloses a vehicle vibration identification device and judgment method with multipath information fusion. The multipath structure is adopted to form a multipath vibration signal by fusing the backward Rayleigh scattering signals of multiple sensing paths, which can reduce the probability of vibration misjudgment caused by various types of noise, random polarization, interference destructiveness, etc., and increase the accuracy of vibration identification. At the same time, the signal demodulation algorithm of the present invention integrates the conventional differential accumulation algorithm and the standard variance method, greatly weakening the dependence of the vibration detection result on the differential interval and reducing the probability of vibration misjudgment caused by it. In addition, compared with the conventional amplitude differential accumulation algorithm, the signal processing algorithm of the present invention effectively improves the signal-to-noise ratio of the vibration detection signal.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle vibration recognition, and in particular to a vehicle vibration recognition device and a judgment method for multipath information fusion. Background Art

[0002] With the rapid growth of the number of vehicles in recent years, highways are facing increasing pressure, causing serious problems such as traffic jams and traffic accidents. Therefore, highway operators are in urgent need of developing new methods to improve transportation efficiency and safety. At present, highway risk management mainly adopts two types of discrete sensors: invasive and non-invasive. The former are installed on the road surface (such as magnetic sensors, induction coils, etc.), and the latter are installed at different locations on the road (such as radar sensors, cameras, etc.). These sensor-based traffic management technologies have effectively improved road safety and reduced road congestion. However, it should be noted that by the end of 2019, the total mileage of my country's highways had reached about 150,000 kilometers, and these sensors can only perceive discretely, so they cannot match the rapid development requirements of highways.

[0003] Recent advances in distributed vibration sensing (DVS) schemes have made them a promising technology for sensitive measurements of transport vibrations. Due to its fully distributed nature, DVS can locate external dynamic disturbances at any position of the optical fiber with a spatial scale resolution of more than tens of kilometers. Using DVS technology, optical fiber can be used as an equivalent sensing array to economically achieve long-distance coverage. In addition, DVS is less affected by ambient lighting and weather changes. DVS can generally be divided into Brillouin-based DVS and Rayleigh scattering-based DVS. The former is limited to its application to low-frequency disturbances over relatively short sensing lengths due to its large amount of time spent in data acquisition and frequency scanning. In contrast, Rayleigh scattering-based DVS has shown the ability to measure higher frequency vibrations over a longer range and has therefore become a powerful tool in many important fields, including railway monitoring, pipeline safety, and intrusion detection.

[0004] Phase-sensitive optical time-domain reflectometry ( -OTDR) is the most commonly used DVS based on Rayleigh scattering because -OTDR is based on the working mechanism of optical coherence effect and has higher sensitivity to external vibration. In this technology, ultra-narrow linewidth laser pulses are emitted into the sensing fiber, and any mechanical vibration will change the coherence effect of Rayleigh scattered light on a large number of Rayleigh scattering units within the duration of a pulse. Therefore, the phase and intensity of the backscattered Rayleigh light are modulated by the vibration. After digital signal processing (DSP), the vibration information can be determined by analyzing the phase or intensity changes of the Rayleigh scattering signal. Among them, based on the relationship between signal amplitude and vibration -OTDR amplitude demodulation scheme has been widely used due to its simple structure.

[0005] at present, -OTDR systems usually adopt a single-path sensing structure, and vibration positioning methods usually adopt an amplitude differential accumulation algorithm based on amplitude demodulation. It should be pointed out that the single-path structure and the conventional amplitude differential accumulation algorithm have better sensing performance in vibration detection applications, but there are still the following shortcomings:

[0006] 1. Single path detection structure -OTDR system, due to the time domain intensity fluctuation of the detection pulse, laser phase noise, detector thermal noise, or random interference destructive effect, polarization disturbance, etc., the intensity of Rayleigh backscattered Rayleigh signal fluctuates randomly, which in turn causes vibration signal jumps and vibration positioning misjudgment.

[0007] 2. Although the conventional amplitude demodulation scheme is simple, its strong dependence on the differential interval for vibration detection makes it easy to misjudge vibration detection and is not very applicable. The main reason is that in the conventional amplitude differential accumulation algorithm, the value of the differential interval number needs to be repeatedly debugged and determined based on the frequency of the vibration signal to be measured, the repetition frequency of the detection pulse (related to the detection range), etc. The appropriateness of its value is closely related to the accuracy of vibration source positioning. The dependence of this method on the differential interval will lead to positioning failure or erroneous positioning information for inappropriate differential intervals. Summary of the invention

[0008] The present invention aims to solve the problem that the existing single-mode optical fiber -In order to solve the problem of low positioning accuracy in OTDR vehicle vibration identification, a vehicle vibration identification device and a judgment method with multipath information fusion are provided, which can effectively reduce the probability of misjudgment in system vibration monitoring.

[0009] To solve the above problems, the present invention is achieved through the following technical solutions:

[0010] A vehicle vibration identification device with multipath information fusion includes a phase-sensitive optical time domain reflectometer module and a sensing optical fiber. The phase-sensitive optical time domain reflectometer module is composed of a laser, a waveform generator, a signal acquisition and processing module, and a Z-path sensing path; wherein Z ≥ 2; each sensing path is composed of an optical beam splitter, a pulse forming module, an optical circulator, an optical beam combiner, a balance detection module, and an IQ demodulation module; the input end of the optical beam splitter forms the input end of the sensing path; an output end of the optical beam splitter is connected to the first port of the optical circulator via the pulse forming module; the second port of the optical circulator forms the acquisition end of the sensing path; the third port of the optical circulator is connected to an input end of the optical beam combiner; the optical beam splitter The other output end of the optical combiner is connected to the other input end of the optical combiner; the output end of the optical combiner is connected to the input end of the IQ demodulation module via the balance detection module, and the output end of the IQ demodulation module forms the output end of the sensing path; the control end of the pulse forming module forms the synchronization control end of the sensing path; the output end of the laser is simultaneously connected to the input end of each sensing path; the output end of each sensing path is simultaneously connected to the acquisition signal input end of the signal acquisition and processing module; the output end of the waveform generator is simultaneously connected to the synchronization control end of each sensing path and the synchronization signal input end of the signal acquisition and processing module. The sensing optical fiber is laid along the highway, and the sensing optical fiber is connected to the acquisition end of each sensing path of the phase-sensitive optical time domain reflectometer module.

[0011] In the above scheme, the sensing optical fiber is a single-core optical fiber, a multi-core optical fiber or a multi-mode optical fiber; when the sensing optical fiber is a single-core optical fiber, the number of single-core optical fibers is the same as the number of sensing paths, and each single-core optical fiber is connected to the collection end of one sensing path; when the sensing optical fiber is a multi-core optical fiber, the number of cores in the multi-core optical fiber is the same as the number of sensing paths, and the multi-core optical fiber is connected to the collection end of each sensing path via a fan-in and fan-out module; when the sensing optical fiber is a multi-mode optical fiber, the number of modes of the multi-mode optical fiber is the same as the number of sensing paths, and the multi-mode optical fiber is connected to the collection end of each sensing path via a photon lantern.

[0012] The judgment method of the vehicle vibration identification device using multipath information fusion comprises the following steps:

[0013] Step 1: The continuous light generated by the laser is sent to the input end of each sensing path. In the sensing path, the optical beam splitter divides the continuous light into two paths: one path is sent to the photosynthesizer as the local oscillator light; the other path is sent to the pulse forming module. The pulse forming module modulates the continuous laser into a detection light with a specified repetition frequency and pulse width under the drive of the waveform generator, and then frequency-shifts the detection light pulse and sends it to the sensing optical fiber through the optical circulator;

[0014] Step 2: When a vehicle passes near a certain point of the sensing optical fiber buried along the highway, the vibration generated will cause the sensing optical fiber to deform slightly, and the interference intensity of the back Rayleigh scattered light of the sensing optical fiber at that position will change. The back Rayleigh scattered light is sent to the optical beam combiner via the optical circulator of the corresponding sensing path; the back Rayleigh scattered light signal contains the amplitude information of all corresponding M detection positions on each sensing optical fiber;

[0015] Step 3: In the sensing path, the photosynthesizer combines the backward Rayleigh scattered light and the local oscillator light and inputs them into the balanced detection module for photoelectric heterodyne detection, and outputs the intermediate frequency signal to the IQ demodulation module; the IQ demodulation module adopts the IQ orthogonal demodulation scheme to infer the backward Rayleigh scattered signal intensity generated by the sensing optical fiber;

[0016] Step 4: The electrical signal acquisition and processing module performs continuous signal acquisition on the backscattered Rayleigh scattering signal strength demodulated by each sensing path to obtain N time domain amplitude data, each of which contains M amplitude information;

[0017] Step 5: The electrical signal acquisition and processing module performs fusion processing on the N time domain amplitude data collected by each sensing path to obtain the final judgment result, namely:

[0018] Step 5.1, using N time-domain amplitude data of each sensing path, obtaining an amplitude difference accumulation curve and an amplitude variance accumulation curve of each sensing path;

[0019] Step 5.2: Perform pairwise cross-coordinate multiplication of the amplitude difference accumulation curve and the amplitude variance accumulation curve of each two sensing paths to obtain the vibration detection signal. Amplitude curve, where Z is the number of sensing paths;

[0020] Step 5.3: Using the vibration detection signal The amplitude curve is used to calculate the vibration signal gain curve and convert the vibration detection signal The gain curves are compared with the preset gain thresholds to obtain the vibration detection signal. digital curves;

[0021] Step 5.4: Transform the vibration detection signal The digital values ​​at the corresponding detection positions on the digital curves are logically ORed to determine whether a vehicle has passed by the sensing optical fiber at the detection position. When the digital values ​​of the same detection position on the digital curves are all false, it is judged that no vehicle has passed by the sensing optical fiber at the detection position; otherwise, it is judged that no vehicle has passed by the sensing optical fiber at the detection position;

[0022] The above M and N are both set values.

[0023] In the above step 5.1,

[0024] Amplitude difference accumulation curve S of the i-th sensing path i1 for:

[0025]

[0026] Amplitude variance accumulation curve S of the i-th sensing path i2 for:

[0027]

[0028] Where i = 1, 2, ... Z, Z represents the number of sensing paths; D i,j represents the jth time domain amplitude data of the i-th sensing path; D i,j-k represents the jkth time domain amplitude data of the i-th sensing path; D i It represents the arithmetic mean of all N time-domain amplitude data of the i-th sensing path, N represents the number of consecutively collected time-domain amplitude data; k represents the given differential curve interval.

[0029] In the above step 5.3, each amplitude curve, each gain curve and each digital curve contains the amplitude information at all M detection positions on the sensing optical fiber.

[0030] In the above step 5.3, when the gain value of the gain curve of the vibration detection signal at a certain detection position is greater than the preset gain value of the preset gain threshold, the digital value of the vibration detection signal at the detection position is true; otherwise, the digital value of the vibration detection signal at the detection position is false.

[0031] Compared with the prior art, the present invention has the following characteristics:

[0032] 1. Due to the different deadweights, driving speeds, road conditions, etc. of vehicles, the frequencies of vibration signals transmitted to the road surface are different. In order to accurately demodulate the vehicle vibration signal, the conventional amplitude differential accumulation algorithm needs to continuously adjust the total number of backward Rayleigh scattering curves N and the curve differential interval k value. Selecting inappropriate N and k values ​​will increase the probability of misjudgment of the system in identifying vehicle vibration. The present invention adopts a multipath structure to form a multi-path vibration signal by fusing the backward Rayleigh scattering signals of multiple sensing paths, which can reduce the probability of vibration misjudgment caused by various types of noise, random polarization, interference destructiveness, etc., and increase the accuracy of vibration identification.

[0033] 2. The signal demodulation algorithm of the present invention integrates the conventional differential accumulation algorithm and the standard variance method, which greatly reduces the dependence of the vibration detection result on the differential interval and reduces the probability of vibration misjudgment caused by it. -OTDR's conventional amplitude differential accumulation algorithm, the signal processing algorithm of the present invention effectively improves the signal-to-noise ratio of the vibration detection signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a structural schematic diagram of a vehicle vibration identification device with multipath information fusion;

[0035] Figure 2 This is a flow chart of the multipath information fusion algorithm described in Example 1 of the present invention;

[0036] Figure 3 The gain curves S′1 and S′2 of the first vibration detection signal S1 and the second vibration detection signal S2 in Example 1 of the present invention are shown in FIG. 1 , where the horizontal axis is the optical fiber length (km) and the vertical axis is the gain (dB); in the figure, when the vehicle travels to 8.57 km, there are 50 amplitude curves of the backward Rayleigh scattering signal light, and the differential curve interval k is selected to be 20;

[0037] Figure 4 The gain curves S′1 and S′2 of the first vibration detection signal S1 and the second vibration detection signal S2 in Example 1 of the present invention are shown in FIG. 1 , where the horizontal axis is the optical fiber length (km) and the vertical axis is the gain (dB); in the figure, when the vehicle travels to 8.57 km, there are 50 backscattered Rayleigh scattering signal light amplitude curves, and the differential curve interval k is selected to be 5;

[0038] Figure 5 The signal-to-noise ratio curves S′1 and S′2 of the first vibration detection signal S1 and the second vibration detection signal S2 in Example 1 of the present invention are shown in FIG. 1 , where the abscissa is the optical fiber length (km) and the ordinate is the gain (dB); in the figure, when the vehicle travels to 8.57 km, there are 50 backscattered Rayleigh scattering signal light amplitude curves, and the differential curve interval k is selected to be 1;

[0039] Figure 6 It is a structural schematic diagram of another vehicle vibration identification device with multipath information fusion;

[0040] Figure 7 The figure is a schematic diagram of the structure of another vehicle vibration identification device with multipath information fusion. DETAILED DESCRIPTION

[0041] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific examples and with reference to the accompanying drawings.

[0042] See also Figure 1 , a vehicle vibration identification device with multipath information fusion, including a phase-sensitive optical time domain reflectometer module and a sensing optical fiber.

[0043] The phase-sensitive optical time-domain reflectometer module is composed of a laser, a waveform generator, a signal acquisition and processing module, and at least two sensing paths. In the present invention, the number of sensing paths is Z, Z is a set value, and Z≥2. Each sensing path is composed of an optical beam splitter, a pulse forming module, an optical circulator, an optical beam combiner, a balanced detection module and an IQ demodulation module. The input end of the optical beam splitter forms the input end of the sensing path. An output end of the optical beam splitter is connected to the first port of the optical circulator via the pulse forming module. The second port of the optical circulator forms the acquisition end of the sensing path. The third port of the optical circulator is connected to an input end of the optical beam combiner. The other output end of the optical beam splitter is connected to the other input end of the optical beam combiner. The output end of the optical beam combiner is connected to the input end of the IQ demodulation module via the balanced detection module, and the output end of the IQ demodulation module forms the output end of the sensing path. The control end of the pulse forming module forms the synchronization control end of the sensing path. The output end of the laser is connected to the input end of each sensing path at the same time. The output end of each sensing path is connected to the acquisition signal input end of the signal acquisition and processing module at the same time. The output end of the waveform generator is connected to the synchronization control end of each sensing path and the synchronization signal input end of the signal acquisition and processing module at the same time.

[0044] Each sensing path shares the same signal acquisition and processing module, but the laser and waveform generator can be shared or non-shared. When the laser is in a non-shared form: each sensing path can be configured with a laser; or several sensing paths can share a laser, while the other paths share a laser. At this time, each laser adopts a constant current drive mode (ACC), the laser wavelength emitted by the laser is 1150.15nm, the line width is less than 3kHz, the frequency stability is 20MHz / 10min, and the polarization state is linear polarization. When the waveform generator is in a non-shared form: each sensing path can be configured with a waveform generator; several sensing paths can share a waveform generator, while the other paths share a waveform generator. At this time, each waveform generator drives the pulse forming module to provide a pulse signal; the pulse width is set to 100ns, the amplitude is 0-500mV, the bias voltage is set to 250mV; the delay is set to 0ns. In this embodiment, all sensing paths share a laser, a waveform generator, and a signal acquisition and processing module. The laser is a high-power narrow-linewidth laser, which emits continuous linear polarization, a spectral linewidth of 3kHz, a central wavelength of 1550.15nm, a maximum output power of 100mW, and a power instability of less than 1%. The continuous light emitted by the high-power narrow-linewidth laser is divided into two equal-power lasers in a ratio of 1:1 and then injected into the first sensing path and the second sensing path respectively. The waveform generator is an arbitrary waveform generator, which provides standard square wave pulses for each pulse forming module, and modulates the continuous laser input into the pulse forming module by the beam splitter into a detection pulse light. In addition, the arbitrary waveform generator controls the sampling time of the signal acquisition and processing module, and synchronously acquires the backward Rayleigh scattering signals of the first sensing path and the second sensing path. The signal acquisition and processing module implements information fusion and makes a final judgment on the vibration detection signal from the first sensing optical fiber connected to the first sensing path and the vibration detection signal from the second sensing optical fiber connected to the second sensing path.

[0045] In the sensing path, the functions of the pulse forming module are: first, to modulate the continuous light output by the laser into a detection light with a specified repetition frequency and pulse width; second, to frequency shift the detection light pulse and perform heterodyne detection on the backward Rayleigh scattering signal. In this embodiment, the pulse forming module is driven by an arbitrary waveform generator to generate a detection light with a repetition frequency of 4kHz and a pulse width of 100ns. At the same time, the detection pulse light generated by the pulse forming module is frequency-shifted down by 200MHz relative to the incident light. The bandwidth of the balanced detection module is 200MHz, and the detection response is 0.9A / W. The gain of the RF amplifier of the IQ demodulation module is 32dB, the passband is 35MHz, and the frequency response range is 200MHz.

[0046] In the sensing path, the laser light generated by the laser is input to one input end of the optical beam splitter. The optical beam splitter divides the laser light into two paths, one of which is injected into the sensing optical fiber through the pulse forming module and the circulator. The backward Rayleigh scattering signal generated by the sensing optical fiber is input to one input end of the optical beam combiner through the optical circulator. The local oscillator laser output by the optical beam splitter is input to the other input end of the optical beam combiner. The backward Rayleigh scattering signal and the local oscillator laser generated by the combined sensing optical fiber are input to the balanced detection module for photoelectric heterodyne detection. The intermediate frequency signal output by the balanced detection module is input to the IQ demodulation module, which performs IQ demodulation on the intermediate frequency signal and then sends it to the signal acquisition and processing module. The signal acquisition and processing module performs data sampling and digital signal processing on the demodulated signal to form a vibration detection signal originating from the sensing optical fiber.

[0047] The sensing optical fiber is laid along the highway, and the sensing optical fiber is connected to the collection end of each sensing path of the phase-sensitive optical time-domain reflectometer module. In the present embodiment, the sensing optical fiber is a single-core optical fiber, and the number of single-core optical fibers is the same as the number of sensing paths. At this time, each single-core optical fiber is connected to the collection end of one sensing path. Each sensing optical fiber originates from being laid along the edge of the highway. The buried depth of the sensing optical fiber is 0.2m-0.5m, and the horizontal distance from the highway is 0.8-1.0m. M detection positions are set on the sensing optical fiber, which correspond to the positions of the optical fiber sampling points. In order to have a better description of the data, the data is now defined as follows: suppose that the Rayleigh scattering signal of a light wave mode returned by a single detection pulse collected by the signal acquisition and processing module is a backward Rayleigh scattering amplitude data, and the number of sampling points in a backward Rayleigh scattering amplitude data is determined by the length of the optical fiber. The longer the optical fiber length, the more detection positions, i.e., the number of sampling points. In the present embodiment, the sensing optical fiber is a single-core single-mode optical fiber, which only supports LP 01 The total length of the light wave transmission mode is 22 km, and the sampling period of the signal acquisition and processing module is set to LP 01 The time it takes for the mode light wave to propagate 1 meter in the sensing fiber, LP 01 The effective refractive index of the LP mode in the sensing fiber is 1.4498, so 01 The propagation time of the mode in the optical fiber for 1m is 4.836ns, so the acquisition frequency of the signal acquisition and processing module is set to 100MHz, and the corresponding optical fiber spatial resolution is 1m (that is, one point is collected every 1m). The length of the sensing optical fiber is 2km, so a backward Rayleigh scattering amplitude data includes the amplitude data of 2000 sampling points. That is, the signal acquisition and processing module collects the amplitude of 2000 positions once, and each position is 1m apart. Among them, M represents the sampling concept at the optical fiber position, M is the set value, and it meets the corresponding spatial resolution of the optical fiber.

[0048] When a vehicle passes near a certain point of the sensing optical fiber buried along the road, the vibration generated will cause the sensing optical fiber to deform slightly, thereby changing the effective refractive index of the sensing optical fiber at that point. The change in the effective refractive index will cause the amplitude of the backscattered Rayleigh light at this point to change accordingly. Since vibration will change the amplitude of the backscattered Rayleigh signal at this point, the vehicle vibration signal can be determined by collecting the backscattered Rayleigh light.

[0049] Taking two sensing paths as an example, the judgment method implemented by the above-mentioned vehicle vibration identification device with multipath information fusion includes the following specific steps:

[0050] Step 1. The continuous laser generated by the laser is sent to the input end of each sensing path. In the sensing path, the optical beam splitter divides the continuous laser into two paths: one is sent to the photosynthesizer as the local oscillator light; the other is sent to the pulse forming module. Driven by the waveform generator, the pulse forming module modulates the continuous laser into a detection light with a specified repetition frequency and pulse width, and sends the detection light pulse to the sensing optical fiber through the optical circulator after frequency shifting.

[0051] Step 2: When a vehicle passes near a certain point of the sensor optical fiber buried along the highway, the vibration generated will cause the sensor optical fiber to deform slightly and generate corresponding backward Rayleigh scattered light. The backward Rayleigh scattered light is sent to the photosynthesizer via the optical circulator of the corresponding sensing path.

[0052] Step 3: In the sensing path, the photosynthesizer combines the backward Rayleigh scattered light and the local oscillator light and inputs them into the balanced detection module for photoelectric heterodyne detection, and outputs the intermediate frequency signal to the IQ demodulation module; the IQ demodulation module adopts the IQ orthogonal demodulation scheme to infer the backward Rayleigh scattered signal intensity generated by the sensing optical fiber.

[0053] The backward Rayleigh scattered signal generated by the first sensing optical fiber is combined with the local oscillator light separated by the first optical beam splitter through the first optical combiner and then input into the first balanced detection module for photoelectric heterodyne detection, and outputs a 200MHz intermediate frequency signal ΔI1. The IQ demodulation module uses an IQ orthogonal demodulation scheme for the intermediate frequency signal ΔI1 to infer the backward Rayleigh scattered signal intensity A1 generated by the first sensing optical fiber.

[0054] The backward Rayleigh scattered signal generated by the second sensing optical fiber is combined with the local oscillator light separated by the second optical beam splitter through the second optical combiner and input into the second balanced detection module for photoelectric heterodyne detection, and outputs a 200MHz intermediate frequency signal ΔI2. The IQ demodulation module uses an IQ orthogonal demodulation scheme for the intermediate frequency signal ΔI2 to infer the backward Rayleigh scattered signal intensity A2 generated by the second sensing optical fiber.

[0055] Step 4: The electrical signal acquisition and processing module performs continuous signal acquisition on the intensity of the backscattered Rayleigh signal demodulated by each sensing path to obtain N time-domain amplitude data, ensuring that two adjacent backscattered Rayleigh amplitude data are the amplitude information of the backscattered Rayleigh signal generated by adjacent detection pulses, and each time-domain amplitude data contains M amplitude information, and finally obtains the total backscattered Rayleigh amplitude data of all sensing paths. Where N represents the sampling concept in the time period, and N is the set value, which is related to the vehicle vibration frequency and the detection pulse frequency.

[0056] The acquisition cycle of the backscattered Rayleigh scattering signal intensities A1 and A2 generated by the two sensing optical fibers is designed as follows:

[0057] T m =n m / c

[0058] In the above formula, m=1 or 2, indicating the first sensing optical fiber or the second sensing optical fiber; n1 indicates the core refractive index of the first sensing optical fiber; n2 indicates the core refractive index of the first sensing optical fiber; and c indicates the vacuum light speed.

[0059] The Rayleigh scattering signal collected from a single detection pulse is the backward Rayleigh scattering amplitude data of the entire optical fiber, which actually contains the amplitude information at M detection positions. The vehicle speed is between 80-100km / h, and the main energy of the vibration frequency to the ground is concentrated in the frequency range around 40Hz, that is, the vibration signal period generated by the vehicle is 25ms. The detection pulse repetition frequency of the first sensing path and the second sensing path of this embodiment is 4kHz, that is, the repetition period of the detection pulse is 250μs.

[0060] The number of consecutive data collections of the Rayleigh scattering signals A1 and A2 of the first sensing path and the second sensing path by the electrical signal acquisition and signal processing module is designed to be: N = 0.5 × 25ms / 250μs = 50, that is, 50 time domain amplitude data are collected for each of the first sensing path and the second sensing path, and each time domain amplitude data contains amplitude information at M detection positions. Then, the collected two-way data is processed to extract the vibration signal caused by the vehicle.

[0061] The 50 time domain amplitude data collected by the first sensing path are expressed as:

[0062] D1=[D 1,1 ,D 1,2 ,D 1,3 ,…D 1,j ,…,D 1,50 ] T

[0063] In the above formula, D 1，jis a row vector containing the amplitudes of M positions. The spatial interval between two adjacent points is 1m, which represents the jth Rayleigh scattering signal returned by the jth detection pulse through the sensing optical fiber 1. Its data length is determined by the length of the sensing optical fiber 1.

[0064] The 50 time domain amplitude data collected by the second sensing path are expressed as:

[0065] D2=[D 2,1 ,D 2,2 ,D 2,3 ,…D 2,j ,…,D 2,50 ] T

[0066] In the above formula, D 2，j is a row vector containing the amplitudes of M positions. The spatial interval between two adjacent points is 1m, which represents the jth Rayleigh scattering signal returned by the jth detection pulse through the sensing optical fiber 2. Its data length is determined by the length of the sensing optical fiber 2.

[0067] Step 5: The electrical signal acquisition and processing module performs fusion processing on the time domain amplitude data collected by each sensing path to obtain the final judgment result.

[0068] like Figure 2 As shown, the specific dual-path data fusion method is as follows:

[0069] Step 5.1: Calculate the amplitude difference accumulation curve and the amplitude variance accumulation curve based on the time domain amplitude data of each sensing path.

[0070] Amplitude difference accumulation curve S of the i-th sensing path i1 for:

[0071]

[0072] Amplitude variance accumulation curve S of the i-th sensing path i2 for:

[0073]

[0074] Where i = 1, 2, ... Z, Z represents the number of sensing paths; D i,j represents the jth time domain amplitude data of the i-th sensing path; D i,j-k represents the jkth time domain amplitude data of the i-th sensing path; It represents the arithmetic mean of all N time-domain amplitude data of the i-th sensing path, N represents the number of consecutively collected time-domain amplitude data; k represents the given differential curve interval.

[0075] Take two sensing paths as an example:

[0076] Based on the time domain amplitude data D of the first sensing path 1，j Calculate the amplitude difference accumulation curve S 11 Sum amplitude variance accumulation curve S 12 , which are respectively expressed as:

[0077]

[0078]

[0079] In the above formula, S 11 and S 12 The first subscript "1" represents the first sensing path, and the second subscripts "1" and "2" represent the amplitude difference accumulation algorithm and the standard variance method respectively adopted for the backscattered Rayleigh signal of the first sensing path; is the arithmetic mean of the N backward Rayleigh scattered signal light amplitude curves of the first sensing path; k represents the difference curve interval in the amplitude difference accumulation algorithm.

[0080] Based on the time domain amplitude data D of the second sensing path 2，j Calculate the amplitude difference accumulation curve S 21 Sum amplitude variance accumulation curve S 22 , which are respectively expressed as:

[0081]

[0082]

[0083] In the above formula, S 21 and S 22 The first subscript "2" represents the second sensing path, and the second subscripts "1" and "2" represent the amplitude difference accumulation algorithm and the standard deviation method respectively for the backscattered Rayleigh signal of the second sensing path; is the arithmetic mean of the N backward Rayleigh scattered signal light amplitude curves of the second sensing path; k represents the difference curve interval in the amplitude difference accumulation algorithm.

[0084] Step 5.2: Cross-fuse the amplitude difference accumulation curves and amplitude variance accumulation curves of all sensing paths in pairs to obtain the detection signal There are amplitude curves, where Z represents the number of sensing paths. Each amplitude curve includes the amplitudes of M detection positions.

[0085] Taking two sensing paths as an example, the amplitude difference accumulation curve S of the first sensing path is 11 Sum amplitude variance accumulation curve S 12 The amplitude difference accumulation curve S of the second sensing path 21 Sum amplitude variance accumulation curve S 22Information is cross-fused: the amplitude difference accumulation curve of one sensing path is multiplied with the amplitude variance accumulation curve of another sensing path to obtain an amplitude curve S1 of the vibration detection signal whose amplitude changes with the optical fiber distance; the amplitude variance accumulation curve of one sensing path is multiplied with the amplitude difference accumulation curve of another sensing path to obtain another amplitude curve S2 of the vibration detection signal whose amplitude changes with the optical fiber distance. The specific method is as follows:

[0086] S1=S 11 ×S 22

[0087] S2=S 12 ×S 21

[0088] In the above formula, S1 is the first amplitude curve, which represents the differential accumulation signal S of the first sensing path. 11 The variance accumulation signal S of the second sensing path 22 S2 is the second amplitude curve, indicating the first sensing path variance accumulation signal S 12 The differential accumulation signal S of the second sensing path 21 The product of .

[0089] The so-called co-location product refers to multiplying the amplitudes of the amplitude difference accumulation curve and the amplitude variance accumulation curve at the same detection position on the optical fiber to obtain the amplitude of the vibration detection signal at the detection position.

[0090] Step 5.3: For all amplitude curves S of the same vibration detection signal i , calculate the corresponding gain curve S i ′, where each gain curve includes gain values ​​of M detection positions, and the digital curve S of the vibration detection signal is obtained by comparing the gain value at each detection position on each gain curve with the preset gain threshold. i ″, wherein each digital curve includes digital values ​​of M detection positions.

[0091] Through the amplitude curve S i Calculate the gain curve S of the vibration detection signal i The formula of ′ is as follows:

[0092] S i ′=10×lg[S i / max(S i )]

[0093] In the above formula, S i is the i-th amplitude curve of the vibration detection signal, S i′ is the gain curve of the i-th vibration detection signal, in decibels (dB).

[0094] In this embodiment, the preset gain threshold is 1.0 dB. Since each gain curve includes the gain values ​​of M detection positions, the gain values ​​at the M detection positions are compared with the preset gain value, and the digital values ​​at the M detection positions can be obtained. At a certain detection position, if its gain value is greater than 1.0 dB, the digital value at the detection position is represented as "1"; otherwise, the digital value at the detection position is represented as "0".

[0095] Step 5.4, after performing a logical OR operation on the digital values ​​at the same detection position on all the digital curves of the vibration detection signal, it can be determined whether there is a vehicle passing by the detection position. That is, when the digital values ​​of all the digital curves of the vibration detection signal at the same detection position are all false, it indicates that no vehicle has passed by the sensing optical fiber at the detection position; otherwise, it is determined that a vehicle has passed by the sensing optical fiber at the detection position.

[0096] The vibration judgment signal S for determining the passing of a vehicle at a certain detection position of the sensing optical fiber is defined as follows:

[0097]

[0098] Taking two sensing paths as an example, the specific judgment rules are shown in Table 1:

[0099] Table 1 Multipath information fusion -OTDR vehicle vibration identification and judgment

[0100]

[0101] The effectiveness of the present invention is described below:

[0102] Figure 3 In the figure, when the vehicle travels to 8.57km and the differential curve interval k is selected as 20, the gains of the gain curves S1′ and S2′ of the first vibration detection signal S1 and the second vibration detection signal S2 at 8.57km are both greater than 2.0dB. Therefore, the digital values ​​of the first numerical curve S″1 and the second numerical curve S″2 at 8.57km are both "1". At this time, the vibration judgment signal S is "1" at this position and "0" at other positions, which can effectively locate the vehicle vibration.

[0103] Figure 4In the figure, when the vehicle travels to 8.57km and the differential curve interval k is selected as 5, the gain of the gain curve S′1 of the first vibration detection signal S1 at 8.57km is greater than 2.0dB, so the digital value of the first numerical curve S″1 at this position is "1"; the gain of the gain curve S″2 of the second vibration detection signal S2 at 8.57km is less than 1.0dB, so the digital value of the second numerical curve S″1 at 8.57km is "0". Therefore, the digital value of the vibration judgment signal S at 8.57km is "1", which can effectively locate the vehicle vibration at the detection position, i.e., 8.57km.

[0104] Figure 5 In the figure, when the vehicle travels to 8.57km and the differential curve interval k is selected as 1, the gain curve S′1 of the first vibration detection signal S1 is less than 1.0dB at 8.57km, so the digital value of the first numerical curve S″1 at this position is "0"; the gain curve S″2 of the second vibration detection signal S2 has a gain greater than 1.0dB at 8.57km, so the digital value of the second numerical curve S″1 at 8.57km is "1". Therefore, the digital value of the vibration judgment signal S at 8.57km is "1", which can effectively locate the vehicle vibration at the detection position, i.e., 8.57km.

[0105] Depend on Figure 3-Figure 5 It can be seen that the selection of the differential curve interval k will not lead to misjudgment. In the conventional differential accumulation algorithm, the value of k needs to be repeatedly debugged and determined based on the frequency of the vibration signal to be measured, the repetition frequency of the detection pulse (related to the detection range), etc. The appropriateness of its value is closely related to the accuracy of vibration source positioning. Generally, the higher (lower) the frequency of the vibration source signal, the smaller (larger) the k value; the longer (shorter) the detection distance, the smaller (larger) the k value. Figure 3-Figure 5 It can be seen that the present invention presents the following advantages: First, the vibration signal detection is independent of the k value selection (even when k=1, the gain curve S′2 obtained by the algorithm has a gain greater than 1.0dB at the vibration position and a gain less than 1.0dB at the non-vibration position, which can accurately locate the vibration position; the conventional differential accumulation algorithm cannot detect the vibration signal at this time. If the vibration signal is to be detected, the differential interval k should be greater than 5); second, the gain curve is significantly improved; if the differential interval k is too small, the vibration signal gain curve determined by the conventional differential accumulation algorithm will show strong fluctuations and instability. When the curve differential interval k is 20, the gain curve obtained by the present invention is 2.0dB better than the conventional differential accumulation algorithm.

[0106] We studied the vehicle vibration identification and judgment based on multipath information fusion φ-OTDR, in which the backscattered Rayleigh light of the optical fiber of the two sensing paths is detected independently, and the curve of amplitude variation with optical fiber distance is obtained. The amplitude signals from different sensing paths are cross-fused to identify whether they are caused by vehicle vibration. After judging according to the gain curve of the fused detection signal, the possibility of incorrect positioning can be reduced. The improved signal processing algorithm improves the gain of the vibration detection signal and reduces the strong dependence of the conventional differential accumulation method on the differential interval k.

[0107] Embodiment 2:

[0108] See also Figure 6 , another vehicle vibration identification device with multipath information fusion includes a phase-sensitive optical time domain reflectometer module and a sensing optical fiber. In this embodiment, the structure of the phase-sensitive optical time domain reflectometer module is the same as that of Example 1, except that a multi-core optical fiber (a multi-core optical fiber with more than two cores) is used instead of the single-core single-mode optical fiber in Example 1. The sensing optical fiber is a multi-core optical fiber, and the number of cores in the multi-core optical fiber is the same as the number of sensing paths. At this time, the multi-core optical fiber is connected to the collection end of each sensing path via a fan-in fan-out module, and the detection pulse is injected into each core of the multi-core optical fiber by the fan-in fan-out module.

[0109] In this embodiment, the refractive index of light propagation in different cores of the multi-core optical fiber is first calculated, and different data sampling rates are set to obtain the time domain amplitude data D of the backscattered signal light of the light waves in different cores. i (i=1,2…n), n represents the number of cores in the multi-core optical fiber used to construct the sensing path; secondly, according to D i Calculate the corresponding amplitude difference accumulation curve S i1 Sum amplitude variance accumulation curve S i2 The subsequent signal fusion rules and vibration signal judgment method are the same as those in Example 1.

[0110] Embodiment 3:

[0111] See also Figure 7 , another vehicle vibration identification device with multipath information fusion includes a phase-sensitive optical time domain reflectometer module and a sensing optical fiber. In this embodiment, the structure of the phase-sensitive optical time domain reflectometer module is the same as that of embodiment 1, except that a multimode optical fiber (multimode optical fiber with more than two modes) is used instead of the single-core single-mode optical fiber in embodiment 1. The sensing optical fiber is a multimode optical fiber, and the number of modes of the multimode optical fiber is the same as the number of sensing paths. At this time, the multimode optical fiber is connected to the collection end of each sensing path via a photon lantern, and its detection pulse is injected into the multimode optical fiber via the corresponding spatial mode input end of the photon lantern.

[0112] In this embodiment, the refractive index of different spatial mode lights propagating in the multimode optical fiber is first calculated, and different data sampling rates are set accordingly to obtain the time domain amplitude data D of the backscattered Rayleigh signal lights of different spatial mode lights. i (i=1,2…n), n represents the number of spatial modes that a multimode fiber can support; secondly, according to D i Calculate the corresponding amplitude difference accumulation curve S i1 Sum amplitude variance accumulation curve S i2 The subsequent signal fusion rules and vibration signal judgment method are the same as those in Example 1.

[0113] It should be noted that although the embodiments of the present invention described above are illustrative, they are not intended to limit the present invention, and therefore the present invention is not limited to the above specific embodiments. Without departing from the principles of the present invention, any other embodiments obtained by those skilled in the art under the guidance of the present invention are deemed to be within the protection of the present invention.

Claims

1. A judgment method for a vehicle vibration identification device with multipath information fusion, wherein the device comprises a phase-sensitive optical time domain reflectometer module and a sensing optical fiber; the phase-sensitive optical time domain reflectometer module is composed of a laser, a waveform generator, a signal acquisition and processing module, and Z sensing paths; wherein Z≥2; each sensing path is composed of an optical beam splitter, a pulse forming module, an optical circulator, an optical beam combiner, a balance detection module and an IQ demodulation module; the input end of the optical beam splitter forms the input end of the sensing path; an output end of the optical beam splitter is connected to the first port of the optical circulator via the pulse forming module; the second port of the optical circulator forms the acquisition end of the sensing path; the third port of the optical circulator is connected to an input end of the optical beam combiner; The other output end of the beam splitter is connected to the other input end of the photosynthesizer; the output end of the photosynthesizer is connected to the input end of the IQ demodulation module via the balance detection module, and the output end of the IQ demodulation module forms the output end of the sensing path; the control end of the pulse forming module forms the synchronization control end of the sensing path; the output end of the laser is simultaneously connected to the input end of each sensing path; the output end of each sensing path is simultaneously connected to the acquisition signal input end of the signal acquisition and processing module; the output end of the waveform generator is simultaneously connected to the synchronization control end of each sensing path and the synchronization signal input end of the signal acquisition and processing module; the sensing optical fiber is laid along the highway, and the sensing optical fiber is connected to the acquisition end of each sensing path of the phase-sensitive optical time domain reflectometer module; Its characteristics are: The steps include: Step 1: The continuous light generated by the laser is sent to the input end of each sensing path. In the sensing path, the optical beam splitter divides the continuous light into two paths: one path is sent to the photosynthesizer as the local oscillator light; All the way to the pulse forming module, the pulse forming module modulates the continuous laser into a detection light of a specified repetition frequency and pulse width under the drive of the waveform generator, and then frequency-shifts the detection light pulse and sends it to the sensing optical fiber through the optical circulator; Step 2: When a vehicle passes near a certain point of the sensing optical fiber buried along the highway, the vibration generated will cause the sensing optical fiber to deform slightly, and the interference intensity of the back Rayleigh scattered light of the sensing optical fiber at that position will change. The back Rayleigh scattered light is sent to the optical beam combiner via the optical circulator of the corresponding sensing path; the back Rayleigh scattered light signal contains the amplitude information of all corresponding M detection positions on each sensing optical fiber; Step 3: In the sensing path, the photosynthesizer combines the backward Rayleigh scattered light and the local oscillator light and inputs them into the balanced detection module for photoelectric heterodyne detection, and outputs the intermediate frequency signal to the IQ demodulation module; The IQ demodulation module adopts the IQ orthogonal demodulation scheme to infer the intensity of the backward Rayleigh scattering signal generated by the sensing fiber; Step 4: The electrical signal acquisition and processing module performs continuous signal acquisition on the backscattered Rayleigh scattering signal strength demodulated by each sensing path to obtain N time domain amplitude data, each of which contains M amplitude information; Step 5: The electrical signal acquisition and processing module performs fusion processing on the N time domain amplitude data collected by each sensing path to obtain the final judgment result, namely: Step 5.1, using N time-domain amplitude data of each sensing path, obtaining an amplitude difference accumulation curve and an amplitude variance accumulation curve of each sensing path; Step 5.2: Perform pairwise cross-coordinate multiplication of the amplitude difference accumulation curve and the amplitude variance accumulation curve of each two sensing paths to obtain the vibration detection signal. Amplitude curve, where Z is the number of sensing paths; Step 5.3: Using the vibration detection signal The amplitude curve is used to calculate the vibration signal gain curve and convert the vibration detection signal The gain curves are compared with the preset gain thresholds to obtain the vibration detection signal. digital curves; Step 5.4: Transform the vibration detection signal The digital values ​​at the corresponding detection positions on the digital curves are logically ORed to determine whether a vehicle has passed by the sensing optical fiber at the detection position. When the digital values ​​of the same detection position on the digital curves are all false, it is judged that no vehicle has passed by the sensing optical fiber at the detection position; otherwise, it is judged that no vehicle has passed by the sensing optical fiber at the detection position; The above M and N are both set values.

2. The judgment method of the vehicle vibration identification device of multipath information fusion according to claim 1, characterized in that: In step 5.1, Amplitude difference accumulation curve S of the i-th sensing path i1 for: Amplitude variance accumulation curve S of the i-th sensing path i2 for: Where i = 1, 2, ... Z, Z represents the number of sensing paths; D i,j represents the jth time domain amplitude data of the i-th sensing path; D i,j-k represents the jkth time domain amplitude data of the i-th sensing path; It represents the arithmetic mean of all N time-domain amplitude data of the i-th sensing path, N represents the number of consecutively collected time-domain amplitude data; k represents the given differential curve interval.

3. The judgment method of the vehicle vibration identification device of multipath information fusion according to claim 1, characterized in that: In step 5.3, each amplitude curve, each gain curve and each digital curve contains the amplitude information at all M detection positions on the sensing optical fiber.

4. The judgment method of the vehicle vibration identification device of multipath information fusion according to claim 1, characterized in that: In step 5.3, when the gain value of the gain curve of the vibration detection signal at a certain detection position is greater than the preset gain value of the preset gain threshold, the digital value of the vibration detection signal at the detection position is true; otherwise, the digital value of the vibration detection signal at the detection position is false.

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