A remote monitoring system and monitoring method for turnout rail damage

Abstract

The invention provides a remote monitoring system for damage to a turnout rail and a monitoring method thereof. The remote monitoring system for damage to a turnout rail and a monitoring method thereof include: dividing the turnout rail to be tested into a number of monitoring intervals, arranging a sensor array in each interval in a certain order, and the array can send and receive ultrasonic signals; using a pseudo-random code orthogonal phase modulation method to generate a lamb wave ultrasonic signal to avoid the problem of time aliasing between the direct wave and the reflected wave; controlling the sensor to receive and send ultrasonic lamb wave signals to obtain data; using dispersion analysis to obtain the dispersion curve of the lamb wave in the turnout rail, and then obtaining the actual wave velocity of the lamb wave; using wavelet transform to obtain the propagation time of the lamb wave; and using an elliptic algorithm to achieve damage monitoring and positioning. The problem of time aliasing between the direct wave and the reflected wave is solved, the peak power of the reflected wave is increased, and minor damage can be monitored, improving the accuracy of damage monitoring. At the same time, remote monitoring can be achieved, saving manpower and improving monitoring efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of railway industry, and in particular to a remote monitoring system for turnout point rail damage and a monitoring method thereof. Background Art

[0002] As we all know, trains cannot actively turn when running on the railway, and can only rely on switches to turn from one track to another. With the substantial increase in train speed and axle weight, various damage phenomena on the track are becoming more and more serious, especially on heavy-duty and high-speed railways. As the weakest part of the turnout, these damages often occur on the turnout point rail, so the detection of the turnout point rail is very important.

[0003] The traditional inspection method on railways is to have maintenance workers knock on the track with a hammer and identify the sound to determine whether there is a crack. Obviously, this method is too dependent on the experience of the inspector and is too inefficient. With the rapid development of my country's railways, especially high-speed railways, the method of relying on manual knocking to identify the sound is far from meeting the actual needs. In the current monitoring of turnout point rail damage, large rail flaw detection vehicles and hand-pushed rail flaw detection vehicles are generally used. Large rail flaw detection vehicles carry out rapid periodic inspections of in-service lines, and there is a dangerous window period; its monitoring capability depends to a large extent on the alignment of the ultrasonic wheel probe during rapid operation, and because ultrasonic waves decay quickly in the air, ultrasonic signals cannot effectively enter the designated area inside the rail, and there is a possibility of missed damage. For hand-push rail flaw detection vehicles, the daily operating length is about 8 kilometers. At present, the national railway operating mileage is 146,300 kilometers, and the hand-push rail flaw detection vehicles cannot meet the large demand; taking the Beijing-Zhangjiakou High-speed Railway as an example, the lowest temperature in Zhangjiakou area in winter reaches minus 24.9 degrees Celsius, and the lowest operating temperature of the rail flaw detection vehicle is minus 20 degrees Celsius, which cannot meet the needs of the Zhangjiakou area; the coupling agent used by the hand-push flaw detection vehicle is limited by the low temperature and it is difficult to achieve the required accuracy.

[0004] In most cases, fatigue cracks are in the form of microcracks or closed cracks, which exist in the first 80% of fatigue development and are almost impossible to distinguish by human eyes alone. Among them, researchers usually refer to fatigue cracks with a width of less than 0.5 mm as fatigue microcracks.

[0005] In actual operation, rails are often subjected to large-amplitude lateral vibration. Once fatigue microcracks are formed in the rails, the huge lateral force between the wheel and rail will cause them to expand laterally, greatly increasing the possibility of rail breakage. Therefore, effective detection and timely maintenance of microcracks that initiate in the early fatigue stage of the rails to prevent them from continuing to expand into macro cracks and prevent them from entering the stage of unstable crack expansion are of great significance for preventing major production safety accidents, ensuring the safe and reliable service of rails, and maintaining the stability of the safety foundation of railway transportation.

[0006] Lamb wave is the most commonly used waveguide form for ultrasonic nondestructive testing, also known as plate wave. Lamb wave has the advantages of long propagation distance and sensitivity to both surface and internal damage of the structure. Ultrasonic detection of thin plates sometimes encounters great difficulties, while ultrasonic lamb wave is more successfully applied in nondestructive testing of thin plates and has obvious advantages in thin plate detection. Therefore, the present invention uses lamb wave as the flaw detection wave of the turnout tip flaw detection system, which conforms to the characteristic of thin thickness of the turnout tip and has excellent flaw detection effect. In addition, lamb wave is often used in health monitoring of aerospace and other material industries, and has achieved excellent results. Its mature research theory, low use cost, strong practicality and other advantages provide good theoretical support.

[0007] The disadvantages of the lambda signal waveform with five peaks are: (1) The narrower the pulse signal band, the longer the time required for the time signal, resulting in the aliasing of the echo signal, multi-modal signal and direct signal. (2) The five peaks use non-equal amplitude waves, the signal peak power is small, the reflected wave peak amplitude is small, and it is not easy to detect minor damage.

[0008] The lamb signal waveform adopts a pseudo-random code phase-modulated wave and utilizes the autocorrelation characteristics of the pseudo-random code. Under the condition of the same signal bandwidth, the transmitted pulse signal and the received signal are cross-correlated to generate a narrower pulse signal, which solves the problem of time aliasing between the direct wave and the reflected wave. The peak power of the reflected wave is increased, which can detect tiny damage and solves the problem of low peak power of the five waves that is difficult to detect.

[0009] Therefore, it is necessary to provide a remote monitoring system for turnout point rail damage and a monitoring method thereof to solve the above-mentioned technical problems. Summary of the invention

[0010] The technical problem solved by the invention is to provide a remote monitoring system for turnout point rail damage and a monitoring method thereof, which can solve the problem that the existing monitoring technology cannot monitor continuously and cannot monitor under complex conditions such as high temperature and high humidity.

[0011] In order to solve the above technical problems, the invention provides a remote monitoring system for turnout point rail damage, comprising: a layout module, the layout module is used to divide the turnout point rail to be tested into a number of monitoring intervals, and sensors are arranged in the several monitoring intervals, each sensor can send and receive signals;

[0012] A collection module, which is used to control the sensor to send and receive signals and obtain relevant data;

[0013] A pseudo-random code processing module, the pseudo-random code processing module is used to convert the lamb wave generated by the acquisition module into a pseudo-random phase modulation wave;

[0014] A sending module, which uses a 4G module to transmit the obtained data to the cloud for remote processing;

[0015] The monitoring module is responsible for monitoring whether the switch point rail is damaged. The main body is a software with three functions: dispersion analysis, wavelet transform, and ellipse positioning. Whether damage occurs is determined by whether the ellipse algorithm has a solution.

[0016] A remote monitoring method for turnout point rail damage comprises the following steps:

[0017] S101: Divide the switch point rail to be monitored into a plurality of monitoring sections, and arrange a plurality of sensors in the switch point rail monitoring section to be measured, so that the plurality of sensors are distributed near the rail waist and the rail bottom;

[0018] S102: the sensor excites lamb waves using a pseudo-random code and receives reflected lamb wave signals;

[0019] S103: The sensor transmits the collected data to a remote end for analysis;

[0020] S104: Analyze and process the obtained lamb wave signal using wavelet transform to obtain the propagation time of the lamb wave signal; the formula of wavelet transform is as follows:

[0021]

[0022] S105: using dispersion analysis on the obtained lamb wave signal to obtain the actual propagation wave velocity of the lamb wave propagating in the rail;

[0023] S106: Bring the data obtained from S104 and the parameters obtained from S105 into the ellipse positioning algorithm for solution;

[0024] S107: Calculate using ellipse algorithm;

[0025] S108: If the ellipse algorithm has a solution, it is determined that the rail contains damage;

[0026] S109: If there is no solution using the ellipse algorithm, it is determined that there is no damage inside the rail.

[0027] Preferably, a pseudo-random code phase-modulated wave is used to generate a narrow pulse signal to replace the traditional five-peak signal; the lamb waveform uses a random code phase-modulated wave, and utilizes the autocorrelation characteristics of the random code. Under the same signal bandwidth conditions, the transmitted pulse signal and the received signal are cross-correlated to generate a narrower pulse signal.

[0028] Preferably, a 4G module is used for data transmission, and the 4G module is a module for wireless transmission based on a 4G network.

[0029] Preferably, the sensors are piezoelectric sensors, and any three non-collinear sensors can cooperate with each other to generate a lamb wave propagation path.

[0030] Preferably, the ellipse algorithm uses a method of solving the intersection of two ellipses to obtain the damage location, each ellipse uses the distance between two sensors as the focal length, and the actual distance traveled by the lamb wave in the turnout point rail after reflection is obtained.

[0031] Compared with the related technologies, the remote monitoring system for turnout point rail damage and the monitoring method thereof provided by the invention have the following beneficial effects: the time aliasing problem of direct waves and reflected waves is solved, the peak power of reflected waves is increased, minor damages can be monitored, and the accuracy of damage monitoring can be improved. At the same time, remote monitoring can be achieved, manpower can be saved, and monitoring efficiency can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A schematic flow chart of a method for remote damage monitoring of a turnout point rail based on ultrasonic lamb waves provided by an example of the present invention;

[0033] Figure 2 The principle of pseudo-random code phase modulation of the present invention;

[0034] Figure 3 This is a diagram of the phase-modulated continuous wave forming process of the present invention;

[0035] Figure 4 is a schematic diagram of a dispersion analysis curve of the present invention;

[0036] Figure 5 It is the principle diagram of the ellipse positioning of the present invention;

[0037] Figure 6 This is a schematic diagram of the principle of using an ellipse to locate damage coordinates in the present invention. DETAILED DESCRIPTION

[0038] The invention will be further described below in conjunction with the accompanying drawings and implementation modes.

[0039] like Figure 1-6As shown, a remote monitoring system for damage to a turnout point rail comprises: a layout module, the layout module is used to divide the turnout point rail to be tested into a number of monitoring intervals, and sensors are arranged in the several monitoring intervals, and each sensor can send and receive signals; an acquisition module, the acquisition module is used to control the sensor to send and receive signals to obtain relevant data; a pseudo-random code processing module, the pseudo-random code processing module is used to convert the lamb wave generated by the acquisition module into a pseudo-random phase-modulated wave; a sending module, the sending module uses a 4G module to transmit the obtained data to the cloud, which is convenient for remote processing; a monitoring module, the monitoring module is responsible for monitoring whether the turnout point rail is damaged, and the main body is a software with three functions of dispersion analysis, wavelet transform, and ellipse positioning, and whether the damage occurs is determined by whether the ellipse algorithm has a solution.

[0040] A remote monitoring method for turnout rail damage comprises the following steps:

[0041] S101: Divide the switch point rail to be monitored into a plurality of monitoring sections, and arrange a plurality of sensors in the switch point rail monitoring section to be measured, so that the plurality of sensors are distributed near the rail waist and the rail bottom;

[0042] An ultrasonic excitation sensor is used to apply an ultrasonic lamb signal into the rail to be tested. The signal is a high-frequency ultrasonic signal.

[0043] For example, a high-frequency ultrasonic lamb wave excitation sensor is used to excite a single ultrasonic lamb wave signal with a frequency of 300kHz into the rail to be tested. The reason for selecting a frequency of 300kHz is that the rail is pre-scanned in the high-frequency band of 100kHz to 400kHz, the frequency dispersion of 300kHz is low, and the detection accuracy is controlled at 5mm, so the detection effect is guaranteed.

[0044] Here, a circular thin-sheet piezoelectric ceramic sensor (PZT) is used. It is an artificial ferroelectric with electric domains inside after polarization treatment and has piezoelectric properties. The positive piezoelectric effect refers to the deformation of piezoelectric ceramics when subjected to external loads in the polarization direction. This deformation will change the position of the electric domains and cause internal electric polarization. At this time, charges with opposite signs will be generated on both sides of the polarization direction of the piezoelectric ceramic, that is, a potential difference will be formed on the two sides; when the external load disappears, the deformation will also disappear, and the potential difference between the two sides of the piezoelectric ceramic will also disappear, returning to the original zero potential state: when the external load changes, that is, the deformation changes, the electric polarization phenomenon will also change, and the potential difference on the two sides of the piezoelectric ceramic will also change. This change is reflected in the change in the output signal voltage amplitude, and the amplitude change is proportional to the change in the external load. This positive piezoelectric effect can make piezoelectric ceramics as signal receivers. The inverse piezoelectric effect is when different voltages are applied to the positive and negative electrodes of a piezoelectric ceramic, that is, the piezoelectric ceramic is subjected to an electric field, the electric domain position changes, and the piezoelectric ceramic is deformed from a macroscopic perspective: when the applied voltage value is different, that is, when the electric field is different, the degree of deformation of the piezoelectric ceramic is different, and the deformation size is proportional to the voltage; when the voltage disappears, the electric field effect disappears immediately, and the piezoelectric ceramic returns to its original deformation state. This inverse piezoelectric effect can make piezoelectric ceramics act as an exciter of stress wave signals, thus reflecting that piezoelectric ceramics can convert electrical energy into mechanical energy.

[0045] S102: The sensor uses a pseudo-random code to excite the lamb wave and receives the reflected lamb wave signal; the lamb signal waveform adopts a pseudo-random code phase-modulated wave, and utilizes the autocorrelation characteristics of the pseudo-random code. Under the condition of the same signal bandwidth, the transmitted pulse signal and the received signal are cross-correlated to generate a narrower pulse signal, which solves the problem of time aliasing between the direct wave and the reflected wave, and the peak power of the reflected wave is increased, which can detect tiny damage and solve the problem of low power of the five-wave peak that is difficult to detect.

[0046] The implementation principle of the pseudo-random code phase modulation wave signal is as follows

[0047] If the pseudo code sequence is, the carrier frequency is, and is the signal amplitude, the two-phase coded signal can be expressed as:

[0048] y(t)=Acos[2πf c t+π·m(t)]

[0049] When m(t) = 0, y(t) = -Acos(2πf c t); when m(t)=1, y(t)=Acos(2πf c t), and in the pseudo code sequence, (0, 1) and (1, -1) have the same structure, so the two-phase coded signal can be expressed as follows:

[0050] y(t)=Am(t)cos(2πf c t)

[0051] Wherein, m(t) is a pseudo code sequence represented by "+1" and "-1".

[0052] The principle of generating pseudo-code phase-modulated continuous wave signal is as follows Figure 2 As shown, the code element modulates the carrier through the phase modulator. As the code element changes from +1 to -1, the phase of the carrier changes alternately between 0 and π.

[0053] The two-phase coding signal formation process is as follows Figure 3 As shown, the code element jumps once and the phase of the carrier signal flips 180°, thereby including the information of the baseband signal in the carrier phase.

[0054] S103: The sensor transmits the collected data to a remote end for analysis; the sensor is responsible for receiving the signal after being reflected from the inside of the rail. A circular thin-sheet piezoelectric ceramic sensor (PZT) can be used here. This is an artificial ferroelectric that has been polarized and has electric domains inside and has piezoelectric properties. Due to the limited surface area of ​​the rail, in order to save space, the PZT sensor used can both send and receive signals to improve the utilization efficiency of the rail surface.

[0055] S104: Analyze and process the obtained lamb wave signal using wavelet transform to obtain the propagation time of the lamb wave signal; the formula of wavelet transform is as follows:

[0056]

[0057] In recent years, a mathematical theory and method called wavelet has attracted extensive attention internationally and has become one of the rapidly developing frontier disciplines. It has continuously achieved important results with scientific significance and application value in many scientific and technological fields such as speech synthesis, image processing, pattern recognition, computer vision, CI' imaging, analysis of atmospheric and oceanic waves, celestial mechanics and signal analysis. The reason for this is mainly because it has excellent characteristics that many other processing methods do not have, such as: it is a local transformation of time and frequency, which can effectively extract transient mutation information from the signal; through operations such as scaling and translation, it can perform multi-scale (or multi-resolution) refinement analysis of the signal; good directional selectivity, etc.

[0058] Assume that the transient signal and the wavelet basis function are square-integrable real functions, and the Fourier transform of satisfies the admissibility condition. The wavelet basis is obtained by scaling and translating, denoted as

[0059]

[0060] In the formula: a is the scale factor, a>0; b is the translation factor.

[0061] The wavelet transform expression of transient signal is:

[0062]

[0063] S105: The obtained lamb wave signal is subjected to dispersion analysis to obtain the actual propagation velocity of the lamb wave in the rail; when the lamb wave propagates in the rail, the velocity of the wave will also change with the change of the wave frequency, and this phenomenon is called dispersion. Obviously, only by understanding the dispersion law of lamb in the rail, that is, the dispersion equation, can the velocity of the lamb wave in the rail be truly known.

[0064] For a linear, elastic, isotropic plate with a thickness of 2h, the phase velocity dispersion curve is obtained by solving the dispersion equation:

[0065]

[0066] The above two equations give the phase velocity dispersion curves of the symmetric mode and the antisymmetric mode respectively.

[0067]

[0068] in

[0069] is the lamb wave velocity (phase velocity)

[0070] is the p-wave velocity

[0071] is the shear wave velocity of the plate material

[0072] is the angular frequency of the propagating wave (rad / sec, ω=2πf)

[0073] For rails, by substituting the corresponding parameters into the formula, the lamb wave dispersion curves under symmetric and antisymmetric modes can be obtained, such as Figure 4 Shown are the dispersion curves of the symmetric mode and the antisymmetric mode under certain circumstances, and then the lamb wave velocity under the corresponding frequency (frequency-thickness product) is obtained.

[0074] S106: Bring the data obtained from S104 and the parameters obtained from S105 into the ellipse positioning algorithm for solution;

[0075] S107: Calculate using ellipse algorithm;

[0076] S108: If the ellipse algorithm has a solution, it is determined that the rail contains damage;

[0077] S109: If there is no solution for the ellipse algorithm, it is determined that the rail contains no damage;

[0078] Steps S106, S107, S108, and S109: Substitute the obtained parameters into the ellipse algorithm for solution, and determine whether the ellipse algorithm has a solution. If there is a solution, it is determined that there is damage inside the rail. If there is no solution, it is determined that there is no damage inside the rail, and return to S101.

[0079] The so-called ellipse algorithm is a positioning algorithm. The principle is to use multiple ellipses formed by a sensor array composed of at least three sensors to solve the equation. If the equation has a solution, there is damage, otherwise there is no damage. The distance that the lamb wave travels from one sensor to another constitutes 2a of the ellipse, and the distance between sensors is 2c of the ellipse. The distance that lamb travels in the rail can be written as the product of wave speed and time, which is obtained by dispersion analysis and wavelet transform respectively, and finally the travel distance is obtained. Figure 6 It is the basic principle of ellipse positioning.

[0080] Pseudo-random code phase-modulated wave is used to generate narrow pulse signal to replace the traditional five-peak signal; lambda waveform adopts random code phase-modulated wave and utilizes the autocorrelation characteristics of random code. Under the condition of the same signal bandwidth, the transmitted pulse signal and the received signal are cross-correlated to generate a narrower pulse signal.

[0081] In the above-mentioned remote monitoring method for turnout point rail damage, a 4G module is used for data transmission. The 4G module is a module for wireless transmission based on the 4G network. It communicates through the 4G LTE network and is very suitable for long-distance transmission. Through the 4G network, remote communication can be carried out regardless of the distance between them. Based on the LTE communication protocol, the fastest transmission speed can reach 100Mbps, which can meet most data transmission applications.

[0082] The sensors are piezoelectric sensors, and any three non-collinear sensors can cooperate with each other to generate a lamb wave propagation path.

[0083] The ellipse algorithm uses the method of solving the intersection of two ellipses to obtain the damage location. Each ellipse uses the distance between two sensors as the focal length, and the actual distance traveled by the lamb wave after reflection in the turnout point rail is obtained.

[0084] The above descriptions are merely embodiments of the invention and are not intended to limit the patent scope of the invention. Any equivalent structure or equivalent process transformation made using the contents of the invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the invention.

Claims

1. A remote monitoring system for switch point rails, characterized in that: include: An arrangement module, the arrangement module is used to divide the switch point rail to be measured into a number of monitoring sections, and arrange sensors in the monitoring sections, each sensor being capable of sending and receiving signals; A collection module, which is used to control the sensor to send and receive signals and obtain relevant data; A pseudo-random code processing module, the pseudo-random code processing module is used to convert the lamb wave generated by the acquisition module into a pseudo-random phase modulation wave; Pseudo-random code phase modulation wave is used to generate narrow pulse signal to replace the traditional five-peak signal; lambda waveform uses random code phase modulation wave and uses the autocorrelation characteristics of random code. Under the same signal bandwidth conditions, the transmitted pulse signal and the received signal are cross-correlated to generate a narrower pulse signal; A sending module, which uses a 4G module to transmit the obtained data to the cloud for remote processing; The monitoring module is responsible for monitoring whether the switch point rail is damaged. The main body is a software with three functions: dispersion analysis, wavelet transform, and ellipse positioning. Whether damage occurs is determined by whether the ellipse algorithm has a solution.

2. A method for remote monitoring of turnout rail damage, applied to the remote monitoring system for turnout rails according to claim 1, comprising the following steps: S101: Divide the switch point rail to be monitored into a plurality of monitoring sections, and arrange a plurality of sensors in the switch point rail monitoring section to be measured, so that the plurality of sensors are distributed near the rail waist and the rail bottom; S102: the sensor excites lamb waves using a pseudo-random code and receives reflected lamb wave signals; Pseudo-random code phase modulation wave is used to generate narrow pulse signal to replace the traditional five-peak signal; lambda waveform uses random code phase modulation wave and uses the autocorrelation characteristics of random code. Under the same signal bandwidth conditions, the transmitted pulse signal and the received signal are cross-correlated to generate a narrower pulse signal; S103: The sensor transmits the collected data to a remote end for analysis; S104: Analyze and process the obtained lamb wave signal using wavelet transform to obtain the propagation time of the lamb wave signal; the formula of wavelet transform is as follows: S105: using dispersion analysis on the obtained lamb wave signal to obtain the actual propagation wave velocity of the lamb wave propagating in the rail; S106: Bring the data obtained from S104 and the parameters obtained from S105 into the ellipse positioning algorithm for solution; S107: Calculate using ellipse algorithm; S108: If the ellipse algorithm has a solution, it is determined that the rail contains damage; S109: If there is no solution using the ellipse algorithm, it is determined that there is no damage inside the rail.

3. The remote monitoring method for turnout rail damage according to claim 2, characterized in that: The 4G module is used for data transmission. The 4G module is a module for wireless transmission based on the 4G network.

4. The remote monitoring method for turnout point rail damage according to claim 2, characterized in that: The sensors are piezoelectric sensors, and any three non-collinear sensors can cooperate with each other to generate a lamb wave propagation path.

5. The remote monitoring method for turnout point rail damage according to claim 2, characterized in that: The ellipse algorithm uses the method of solving the intersection of two ellipses to obtain the damage location. Each ellipse uses the distance between two sensors as the focal length, and the actual distance traveled by the lamb wave after reflection in the turnout point rail is obtained.

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