A portable non-contact track frequency-shift signal frequency detection system

Abstract

The application is a portable non-contact track frequency shift signal frequency detection system, characterized by comprising a signal sensing and signal conditioning unit (1), a signal acquisition and data processing unit (2), a data storage unit (3), a data display unit (4), the output end of the signal sensing and signal conditioning unit (1) is electrically connected with the input end of the signal acquisition and data processing unit (2), and the signal sensing and signal conditioning unit (1) sends the collected signal to the signal acquisition and data processing unit (2); the signal acquisition and data processing unit (2) comprises at least two output ends; the application adopts a non-contact sensing technology, a low-cost data acquisition and data processing hardware technology, a reliable data processing algorithm and a small-sized portable design scheme, and only needs to place the detection system on any steel rail on site, so that the carrier frequency and low-frequency signal of the track circuit frequency shift signal can be quickly measured, the on-site measurement efficiency is greatly improved, and the cost is reduced.

Description

Technical Field

[0001] This invention relates to track information detection technology, and in particular to a portable, non-contact track frequency shift signal detection system. Background Technology

[0002] This invention application is based on the priority application of patent application number 202610063844.3. Track frequency shift circuits are core equipment in railway signaling systems. They modulate carrier frequency (1700-2600Hz) signals with low-frequency signals (10.3-29Hz) to form frequency-shifted signals, achieving dual functions of track occupancy detection and train operation information transmission. The system consists of a transmitter, receiver, tuning unit, and other equipment. Electrical insulation joints are used to isolate adjacent sections, enabling safety functions such as rail breakage detection and circuit shunting protection. Track frequency shift signaling is an advanced railway signaling system that utilizes frequency modulation technology to detect train occupancy and transmit control information to trains. It distinguishes different track sections through carrier frequency and encodes train operation instructions through low-frequency modulated signals. With its high safety, high reliability, and high-efficiency information transmission capabilities, it has become a core technology for ensuring the safe and efficient operation of modern railways.

[0003] Existing track circuit frequency shift signal measurements all use contact methods, requiring the measuring probes to be connected to two rails, which is very inconvenient. The measuring equipment is bulky, costly, and difficult to transport. Frequency shift track circuits generate frequency shift signals by modulating low-frequency signals (10.3-29Hz) to carrier frequencies (1700-2600Hz). On-site measurement accuracy for both carrier and low-frequency signals must be no less than 0.1Hz. Existing technologies mainly use high-end digital signal processors for high-speed sampling and data processing, which is highly complex. Summary of the Invention

[0004] The purpose of this invention is to provide a portable non-contact track frequency shift signal detection system that features high measurement accuracy, low cost, high reliability, and convenient maintenance.

[0005] The objective of this invention is achieved by providing a portable, non-contact track frequency shift signal detection system, characterized by comprising a signal sensing and conditioning unit, a signal acquisition and data processing unit, a data storage unit, and a data display unit. The output of the signal sensing and conditioning unit is electrically connected to the input of the signal acquisition and data processing unit, transmitting the signal acquired by the signal sensing and conditioning unit to the signal acquisition and data processing unit. The signal acquisition and data processing unit includes at least two outputs: a first output is electrically connected to the data storage unit, storing the data from the signal acquisition and data processing unit into the data storage unit; and a second output is electrically connected to the data display unit, displaying the data from the signal acquisition and data processing unit on the data display unit.

[0006] The signal sensing and signal conditioning unit includes two non-contact sensing electrodes, a differential processing circuit, and a bandpass filter circuit. The two non-contact sensing electrodes are a first non-contact probe and a second non-contact probe, respectively. The first non-contact probe and the second non-contact probe are electrically connected to the input terminal of the differential processing circuit. The differential processing circuit performs differential amplification and then outputs the signal to the input terminal of the bandpass filter circuit, where it is filtered before being output.

[0007] The first and second non-contact probes are two copper-clad plates on a 1.6mm thick circuit board.

[0008] The first non-contact probe has a copper plating size of 1cm*6cm, the second non-contact probe has a copper plating size of 2cm*6cm, the copper thickness is 1 ounce, and the gap between the circuit board and the steel rail is about 5mm.

[0009] The copper plating is not in contact with the rail. The parasitic capacitance between the copper plating and the rail is used to sense the electrical signal on the rail. The voltage on the electrode during a certain period of time is u(t), as shown in formula (1). u(t) (1) The voltage sensed by the first non-contact probe is V1, and the voltage sensed by the second non-contact probe is V2. The first non-contact probe is connected to GND through C1 and R1, and the second non-contact probe is connected to GND through C2 and R2, forming a voltage to ground. The sensed signal is filtered once through C1 and C2. The voltages V1 and V2 are output as differential amplified voltages by differential operational amplifier U1. The output voltage VOUT = (V2 - V1) * G, where G is the amplification factor G = 1 + 50KΩ / R3. By acquiring the voltage difference between two non-contact probes of different sizes and amplifying the voltage, non-contact sensing acquisition of frequency shift signals is achieved.

[0010] Bandpass filter circuits can filter out low-frequency components below 1500Hz and high-frequency components above 3500Hz from signals. In this invention, the bandpass filter circuit effectively filters out the 50Hz power frequency signal and irrelevant high-frequency components in the field, improving the stability and reliability of measurements.

[0011] The signal acquisition and data processing unit performs data acquisition, data processing, and frequency calculation through the following steps: Step 1: The voltage signal output by the signal sensing and signal conditioning unit... Figure 2 The output real-time voltage signal VOUT is acquired by an analog signal acquisition unit.

[0012] Step 2: In order to achieve accurate data sampling, the analog quantity acquisition unit is triggered periodically by the timed sampling unit to perform sampling.

[0013] Step 3: To ensure reliable and efficient storage of the collected data, this invention uses a DMA (Direct Memory Access) data storage unit for real-time data storage.

[0014] Step 4: When the data collected by the DMA data storage unit reaches the set quantity, the timed data acquisition ends, resulting in a simulated data sequence X(n). The data windowing processing unit then multiplies all collected data points x(n) by a window function w(n) to obtain the processed data sequence X(n), where w(n) = 0.5. 0.5 cos(2 π n / (N 1)), N=4096, to implement data windowing processing. After windowing processing, the frequency resolution of the data in the frequency domain is effectively improved and the leakage of the spectrum can be reduced.

[0015] Step 5: The data FFT (Fast Fourier Transform) processing unit performs data FFT calculations, converting the data from the time domain to the frequency domain. Due to the low-cost, miniaturized design of this invention, the processor's computing power is limited. The highest frequency of the frequency-shifting signal on the railway is 2600Hz. This invention uses a sampling rate of fs=10k, with N=4096 sampling points, resulting in a frequency resolution of fs / N=10K / 4096=2.44Hz, which cannot meet the 0.1Hz accuracy requirement. Therefore, the following data processing algorithm is adopted: First, the windowed data sequence X(n) is complex modulated, that is, X(n) is multiplied by... ,in To determine the center frequency of the frequency-shifted signal being detected, the signal band to be calculated is shifted to near zero. Then, a digital low-pass filter is applied, retaining only the data within the band to be processed. The signal within the band is then resampled at a frequency of fsn = fs / d = 10K / 40 = 250Hz, where d is the frequency refinement factor, which is 40. The number of sampling points is N = 4096. After performing an FFT transformation, the final frequency resolution is fs / (d*N) = 10k / (40*4096) = 0.06Hz, which greatly improves the resolution of the frequency domain signal and meets the frequency resolution accuracy requirement of 0.1Hz.

[0016] Step 6: Shift the frequency band signal calculated in Step 5 back to the actual spectrum lines, that is, add frequency band signal... Within the frequency range of 1500Hz to 3000Hz, find the maximum signal amplitude to calculate the maximum frequency of the main lobe, which is the carrier frequency Fz of the frequency-shifted signal. Then, find the other two maximum signal amplitudes within the frequency ranges of (Fz-40Hz, Fz-5Hz) and (Fz+5Hz, Fz+40Hz), which are the two sidelobe signals closest to the main lobe. The two frequency points where the maximum sidelobe signal is found are f1 and f2, and (f2-f1) / 2 is the low-frequency signal to be collected.

[0017] The advantages of this invention are: it adopts non-contact sensing technology, low-cost data acquisition and data processing hardware technology, reliable data processing algorithms, and a miniaturized and portable design. On-site, the detection system only needs to be placed on any rail to quickly measure the carrier frequency and low-frequency signal of the frequency shift signal of the track circuit, which greatly improves the efficiency of on-site measurement, reduces user costs, and the frequency measurement accuracy reaches 0.06Hz, which is sufficient to meet the on-site requirement that the measurement accuracy of carrier frequency and low-frequency signal is not less than 0.1Hz.

[0018] The present invention will be further described below with reference to the embodiments and accompanying drawings. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the system framework of an embodiment of the present invention; Figure 2 This is the circuit schematic of the signal sensing and signal conditioning unit; Figure 3 This is a block diagram of the signal acquisition and data processing unit circuit.

[0020] In the diagram, 1. Signal sensing and signal conditioning unit; 2. Signal acquisition and data processing unit; 3. Data storage unit; 4. Data display unit; 11. Two non-contact sensing electrodes; 12. Differential processing circuit; 13. Bandpass filter circuit; 111. First non-contact probe; 112. Second non-contact probe; 21. Analog signal acquisition unit; 22. Timing sampling unit; 23. DMA data storage unit; 24. Data windowing processing unit; 25. Data FFT processing unit; 26. Frequency calculation unit. Detailed Implementation

[0021] The following detailed description, in conjunction with the accompanying drawings and embodiments, illustrates the implementation of the present invention, providing a thorough understanding of how the invention uses technical means to solve technical problems and achieve technical effects, and facilitating its implementation. It should be noted that, as long as no conflict exists, the various embodiments and features within them can be combined with each other, and the resulting technical solutions are all within the protection scope of the present invention. Furthermore, numerous specific details are set forth in the following description for illustrative purposes, providing a thorough understanding of the embodiments of the present invention. However, it will be apparent to those skilled in the art that the present invention can be implemented without the specific details or the particular methods described herein.

[0022] like Figure 1 As shown, this invention relates to a portable non-contact track frequency shift signal detection system, comprising a signal sensing and conditioning unit 1, a signal acquisition and data processing unit 2, a data storage unit 3, and a data display unit 4. The output terminal of the signal sensing and conditioning unit 1 is electrically connected to the input terminal of the signal acquisition and data processing unit 2, transmitting the signal acquired by the signal sensing and conditioning unit 1 to the signal acquisition and data processing unit 2. The signal acquisition and data processing unit 2 includes at least two output terminals. The first output terminal is electrically connected to the data storage unit 3, storing the acquired and processed data into the data storage unit 3. The second output terminal is electrically connected to the data display unit 4, displaying the acquired and processed data on the data display unit 4.

[0023] like Figure 2 As shown, the signal sensing and signal conditioning unit 1 includes two non-contact sensing electrodes 11, a differential processing circuit 12, and a bandpass filter circuit 13. The two non-contact sensing electrodes 11 are a first non-contact probe 111 and a second non-contact probe 112, respectively. The first non-contact probe 111 and the second non-contact probe 112 are electrically connected to the input terminal of the differential processing circuit 12, and are differentially amplified by the differential processing circuit 12, and then output to the input terminal of the bandpass filter circuit 13, and then filtered by the bandpass filter circuit 13 before being output.

[0024] The first non-contact probe 111 and the second non-contact probe 112 are two copper-clad plates on a circuit board with a thickness of 1.6mm. The copper-clad plate of the first non-contact probe 111 is 1cm*6cm in size, and the copper-clad plate of the second non-contact probe 112 is 2cm*6cm in size. The copper thickness is 1 ounce. The gap between the circuit board and the rail is about 5mm. The two copper-clad plates are not in contact with the rail. The parasitic capacitance between the copper-clad plates and the rail is used to sense the electrical signal on the rail. The voltage on the point pole is u(t) during a certain period of time, as shown in formula (1). u(t) (1) The first non-contact probe 111 senses a voltage V1, and the second non-contact probe 112 senses a voltage V2. The first non-contact probe 111 is connected to GND through C1 and R1, and the second non-contact probe 112 is connected to GND through C2 and R2, forming a voltage to ground. The sensed signal is filtered once through C1 and C2. Voltages V1 and V2 are output as a differential amplified voltage by differential operational amplifier U1, with the output voltage VOUT = (V2 - V1) * G, where G is the amplification factor G = 1 + 50KΩ / R3. By acquiring the voltage difference between two non-contact probes of different sizes and amplifying the voltage, non-contact sensing acquisition of frequency-shifted signals is achieved. The circuit uses a differential circuit to acquire the frequency-shifted signal, effectively suppressing interference signals in the signal.

[0025] The bandpass filter circuit 13 filters out low-frequency components below 1500Hz and high-frequency components above 3500Hz from the signal. The bandpass filter circuit 13 effectively filters out the 50Hz power frequency signal and irrelevant high-frequency components in the field, improving the stability and reliability of the measurement.

[0026] like Figure 3 As shown, the signal acquisition and data processing unit 2 includes an analog signal acquisition unit 21, a timing sampling unit 22, a DMA data storage unit 23, a data windowing processing unit 24, a data FFT processing unit 25, and a frequency calculation unit 26. The input terminal of the analog signal acquisition unit 21 is electrically connected to the output terminal of the signal sensing and signal conditioning unit 1, and acquires the analog signal from the signal sensing and signal conditioning unit 1, and puts the converted digital information into the DMA data storage unit 23. The data windowing processing unit 24 reads the digital value from the DMA data storage unit 23, performs encryption processing, and then the data FFT processing unit 25 performs Fourier transform processing to calculate the final frequency information.

[0027] Signal acquisition and data processing unit 2 performs data acquisition, data processing, and frequency calculation through the following steps: Step 1: The voltage signal output by the signal sensing and signal conditioning unit 1 is... Figure 2 The output real-time voltage signal VOUT is acquired by an analog signal acquisition unit.

[0028] Step 2: In order to achieve accurate data sampling, the analog quantity acquisition unit is triggered periodically by the timed sampling unit to perform sampling.

[0029] Step 3: To ensure reliable and efficient storage of the collected data, this invention uses a DMA data storage unit for real-time data storage.

[0030] Step 4: When the data collected by the DMA data storage unit reaches the set quantity, the timed data acquisition ends, resulting in a simulated data sequence X(n). The data windowing processing unit multiplies all collected data points x(n) by a window function w(n) to obtain the processed data sequence X(n). Where w(n) = 0.5 0.5 cos(2 π n / (N 1)), N=4096, to implement data windowing processing. After windowing processing, the frequency resolution of the data in the frequency domain is effectively improved and the leakage of the spectrum is reduced.

[0031] Step 5: The data FFT processing unit performs data FFT calculations, converting the data from the time domain to the frequency domain. Due to the low-cost, miniaturized design of this invention, the processor's computing power is limited. The highest frequency of the frequency-shifting signal on the railway is 2600Hz. This invention uses a sampling rate of fs=10k, with N=4096 sampling points, resulting in a frequency resolution of fs / N=10K / 4096=2.44Hz, which cannot meet the 0.1Hz accuracy requirement. The data processing algorithm is as follows: First, the windowed data sequence X(n) is complex modulated, that is, X(n) is multiplied by... ,in To determine the center frequency of the frequency-shifted signal being detected, the signal band to be calculated is shifted to near zero. Then, a digital low-pass filter is applied, retaining only the data within the band to be processed. The signal within the band is then resampled at a frequency of fsn = fs / d = 10K / 40 = 250Hz, where d is the frequency refinement factor, which is 40. The number of sampling points is N = 4096. After performing an FFT transformation, the final frequency resolution is fs / (d*N) = 10k / (40*4096) = 0.06Hz, which greatly improves the resolution of the frequency domain signal to meet the 0.1Hz frequency resolution requirement.

[0032] Step 6: Shift the frequency band signal calculated in Step 5 back to the actual spectrum lines, that is, add frequency band signal... Within the frequency range of 1500Hz to 3000Hz, find the maximum signal amplitude to calculate the maximum frequency of the main lobe, which is the carrier frequency signal Fz of the frequency shift signal. Then, find the other two maximum signal amplitudes in the frequency ranges of (Fz-40Hz, Fz-5Hz) and (Fz+5Hz, Fz+40Hz), which are the two side lobe signals closest to the main lobe. The two frequency points where the maximum side lobe signal is found are f1 and f2, respectively. (f2-f1) / 2 is the low-frequency signal to be collected.

[0033] In this invention, the data storage unit stores the data collected on-site in real time.

[0034] The data display unit displays the on-site measurement data in real time.

[0035] The above description is merely an illustrative embodiment of the present invention and is not intended to limit the scope of the invention. Any equivalent changes and modifications made by those skilled in the art without departing from the concept and principles of the present invention, as well as applications to fields not mentioned in the present invention, should fall within the scope of protection of the present invention.

Claims

1. A portable, non-contact system for detecting the frequency of a track frequency shift signal, characterized in that: The system includes a signal sensing and signal conditioning unit (1), a signal acquisition and data processing unit (2), a data storage unit (3), and a data display unit (4). The output of the signal sensing and signal conditioning unit (1) is electrically connected to the input of the signal acquisition and data processing unit (2) to send the signal acquired by the signal sensing and signal conditioning unit (1) to the signal acquisition and data processing unit (2). The signal acquisition and data processing unit (2) includes at least two outputs. The first output is electrically connected to the data storage unit (3) to store the data acquired and processed by the signal into the data storage unit (3). The second output is electrically connected to the data display unit (4) to display the data acquired and processed by the signal on the data display unit (4). The signal acquisition and data processing unit (2) performs data acquisition, data processing, and frequency calculation through the following steps: Step 1: The voltage signal output by the signal sensing and signal conditioning unit 1), i.e., the real-time voltage signal VOUT output in Figure 2, is acquired by the analog signal acquisition unit. Step 2: In order to achieve accurate data sampling, the analog quantity acquisition unit is triggered periodically by the timed sampling unit to perform sampling; Step 3: To ensure reliable and efficient storage of the collected data, real-time data storage is performed using a DMA data storage unit; Step 4: When the data collected by the DMA data storage unit reaches the set quantity, the timed data acquisition ends, resulting in a simulated data sequence X(n). The data windowing processing unit multiplies all acquired data points x(n) by a window function w(n) to obtain the processed data sequence X(n); where w(n) = 0.

5. 0.5 cos(2 π n / (N 1)), N=4096, to implement data windowing processing. After windowing processing, the frequency resolution of the data in the frequency domain is effectively improved and the leakage of the spectrum is reduced. Step 5: The data FFT processing unit performs data FFT calculations, converting the data from the time domain to the frequency domain; Step 6: Shift the frequency band signal calculated in Step 5 back to the actual spectrum lines, that is, add frequency band signal... Within the frequency range of 1500Hz to 3000Hz, find the maximum signal amplitude to calculate the maximum frequency of the main lobe, which is the carrier frequency signal Fz of the frequency shift signal. Then, find the other two maximum signal amplitudes within the frequency ranges of (Fz-40Hz, Fz-5Hz) and (Fz+5Hz, Fz+40Hz), which are the two side lobe signals closest to the main lobe. The two frequency points where the maximum side lobe signal is found are f1 and f2, respectively. (f2-f1) / 2 is the low-frequency signal to be collected.

2. The portable non-contact track frequency shift signal detection system according to claim 1, characterized in that: The signal sensing and signal conditioning unit (1) includes two non-contact sensing electrodes (11), a differential processing circuit (12), and a bandpass filter circuit (13). The two non-contact sensing electrodes (11) are a first non-contact probe (111) and a second non-contact probe (112), respectively. The first non-contact probe (111) and the second non-contact probe (112) are electrically connected to the input terminal of the differential processing circuit (12), respectively. The differential amplification is performed by the differential processing circuit (12), and then the output is sent to the input terminal of the bandpass filter circuit (13), and then filtered by the bandpass filter circuit (13) before being output.

3. The portable non-contact track frequency shift signal detection system according to claim 2, characterized in that: The first non-contact probe (111) and the second non-contact probe (112) are two copper-clad plates on a circuit board with a thickness of 1.6 mm.

4. The portable non-contact track frequency shift signal detection system according to claim 2, characterized in that: The first non-contact probe (111) has a copper plating size of 1cm*6cm, the second non-contact probe (112) has a copper plating size of 2cm*6cm, the copper thickness is 1 ounce, and the gap between the circuit board and the rail is about 5mm.

5. A portable non-contact track frequency shift signal detection system according to claim 2, characterized in that: Two copper-clad plates are not in contact with the rail. The parasitic capacitance between the copper-clad plates and the rail is used to sense the electrical signal on the rail. The voltage on the pole is u(t) during a certain period of time, as shown in formula (1). u(t) (1) The voltage sensed by the first non-contact probe 111 is V1, and the voltage sensed by the second non-contact probe 112 is V2. The first non-contact probe 111 is connected to GND through C1 and R1, and the second non-contact probe 112 is connected to GND through C2 and R2, forming a voltage to ground. The sensed signal is filtered once through C1 and C2. The voltages V1 and V2 are output as a differential amplified voltage by the differential operational amplifier U1. The output voltage VOUT = (V2 - V1) * G, where G is the amplification factor G = 1 + 50KΩ / R3. By acquiring the voltage difference between two non-contact probes of different sizes and amplifying the voltage, non-contact sensing acquisition of frequency shift signals is achieved.

6. A portable non-contact track frequency shift signal detection system according to claim 2, characterized in that: The bandpass filter circuit (13) filters out the low frequency part below 1500Hz and the high frequency part above 3500Hz in the signal. The bandpass filter circuit (13) effectively filters out the 50Hz power frequency signal and the incoherent high frequency part in the field, thereby improving the stability and reliability of the measurement.

7. The portable non-contact track frequency shift signal detection system according to claim 1, characterized in that: Step 5: The data FFT processing unit performs data FFT calculations using the following algorithm: First, the windowed data sequence X(n) is complex-modulated, i.e., X(n) is multiplied by... ,in To determine the center frequency of the frequency-shifted signal being detected, the signal band to be calculated is shifted to near zero. Then, a digital low-pass filter is applied to retain only the data within the frequency band to be processed. The signal within the frequency band is then resampled at a sampling frequency of fsn = fs / d = 10K / 40 = 250Hz, where d is the frequency refinement factor, which is 40. The number of sampling points is N = 4096. Finally, an FFT transformation is performed, and the final frequency resolution is fs / (d*N) = 10k / (40*4096) = 0.06Hz.

Images