CN107561491B - Passive beacon device, system and measurement method for accurate positioning of railroad trains - Google Patents

Abstract

The invention discloses a passive beacon device, a system and a method for accurately positioning a rail train, wherein the device comprises an interrogator and at least 1 passive beacon; the interrogator comprises a frequency synthesizer A, a digital signal processor A, a transmitting antenna A1 and a receiving antenna A2; the frequency synthesizer generates different single-frequency radio frequency signals as interrogation signals to be transmitted through a transmitting antenna A1; the passive beacon receives the inquiry signal and forwards the response signal; the center frequencies of different passive beacons are different, and the working frequency of each passive beacon at least corresponds to a single-frequency radio frequency signal; the receiving antenna a2 receives the reply signal and transmits it to the digital signal processor a to calculate the time when the interrogator is facing the beacon. The method is matched with a train speed measurement positioning method, different beacons correspondingly installed in different intervals are selected, positioning is carried out by measuring the Doppler frequency shift of beacon response signals, and timely compensation and correction are carried out on measurement data of the train speed measurement positioning method, so that high-precision positioning of the rail train is realized.

Description

Passive beacon device, system and measurement method for accurate positioning of railroad trains

technical field

The invention relates to the field of rail traffic and positioning, in particular to a passive beacon device, a system and a measurement method used for accurate positioning of rail trains.

Background technique

Rail train positioning, that is, to accurately obtain the physical position of the vehicle on the track, can more effectively improve the safety and efficiency of driving. The existing main methods of train positioning include: track circuit positioning method, ground beacon method, cross cable loop positioning method, and speed measurement positioning method.

In the existing ground beacon method, beacons are mainly divided into two types: active and passive. Beacons are installed in stations or along tracks such as each track partition. When the train passes, the ground beacon is aligned with the corresponding equipment on the vehicle, and the on-board equipment transmits the corresponding signal to the beacon in the form of electromagnetic waves. The beacon starts to work after receiving the signal transmitted by the on-board equipment, and transmits the current absolute physical position information of the train. Back to the train, the on-board equipment obtains the location information of the train.

The existing beacon detection method, such as the beacon detection method for train positioning disclosed in the Chinese patent "Beacon Detection Method in the Process of Train Positioning" (publication number: CN104554350B), uses the beacon as an RFID beacon, and the equipment passes through the beacon detection method. Search and determine whether the antenna is located in a certain beacon window to determine whether the train passes the position of the corresponding beacon, thereby obtaining the position information of the train. This method cannot avoid the problems of missed reading and misreading of the radio frequency tag, and the anti-interference ability is poor. The positioning accuracy depends on the antenna pattern of the RFID and the speed of the train, so it is difficult to achieve high precision.

The existing train speed measurement and positioning method is to measure the real-time speed of the train first, and then integrate it to obtain the distance of the train, so as to realize the positioning of the train. The current speed measurement methods include wheel shaft rotation information speed measurement, Doppler radar speed measurement, and GPS speed measurement. The method of using the speed measurement and positioning is essentially the time integration of the speed, and its accuracy is affected by the speed measurement accuracy and the accumulation time. Under the condition of a certain speed measurement accuracy, the positioning accuracy will decrease with the increase of the accumulation time.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is the problem that the positioning accuracy in the train speed measurement and positioning method decreases with the increase of the accumulated time. Cooperate with the positioning system to timely compensate the accumulated error generated by the integration, and realize the acquisition of the precise position of the train.

The present invention is achieved through the following technical solutions:

A passive beacon device for accurate positioning of railroad trains, comprising an interrogator and at least one passive beacon;

The passive beacon includes a receiving antenna B1, a band-pass filter B and a transmitting antenna B2 connected in sequence, and the center frequencies of the band-pass filters B of different passive beacons are different;

The interrogator includes a controller A, a frequency synthesizer A, a digital signal processor A, a transmitting antenna A1 and a receiving antenna A2;

The frequency synthesizer can generate different single-frequency radio frequency signals under the control of the controller A as interrogation signals and transmit them through the transmitting antenna A1, and the working frequency of each passive beacon corresponds to at least one single-frequency radio frequency signal; the receiving The antenna B1 can receive the inquiry signal transmitted by the transmitting antenna A1, and the received inquiry signal is filtered by the band-pass filter B and then transmitted as a reply signal through the transmitting antenna B2; the receiving antenna A2 is used to receive the reply signal of the passive beacon and transmit it to the digital Signal processor A; the digital signal processor A is used to calculate the speed information of the train and the time when the interrogator is facing the beacon according to the received signal.

In the use of the passive beacon device of the above technical solution, in order to ensure the positioning accuracy and real-time performance, m beacons are pre-installed on the top, side, or bottom of the track along the train, and the beacon number k is 1, 2, 3, …, m. The interrogator is installed on the train, the interrogator transmits a speed measurement signal, and the speed measurement signal is forwarded by the beacon corresponding to the location of the train and then returned to the interrogator. The change of the target Doppler frequency shift f _d , and finally the interrogator calculates the change law of the beacon Doppler frequency shift to find the moment when the interrogator is facing the beacon position. The position of the train at the time can be accurately determined by the time of the position of the beacon, so as to realize the precise positioning of the train.

As a further improvement of the present invention, the polarizations of the transmitting antenna A1 and the receiving antenna B1 are the same, the polarizations of the transmitting antenna B2 and the receiving antenna A2 are the same, and the polarizations of the transmitting antenna B1 and the transmitting antenna B2 are orthogonal; The polarizations of the transmitting antenna A1 and the receiving antenna A2 are orthogonal; the influence of the background electromagnetic scattering of the beacon on the Doppler frequency measurement can be eliminated, and the train positioning accuracy can be improved.

As another improvement of the present invention, the interrogator further includes an amplifier A, a band-pass filter A1, a low-noise amplifier A, a mixer A, a band-pass filter A2, and an analog-to-digital converter A; the amplifier A is connected to Between the frequency synthesizer A and the transmitting antenna A1; the receiving antenna A2, the low-noise amplifier A, the mixer A, the band-pass filter A2, the analog-to-digital converter A and the digital signal processor A are connected in turn; the described The frequency synthesizer is also connected to the mixer A, and provides the local oscillator signal to the mixer A. In this scheme, the interrogator adopts a non-zero intermediate frequency structure, which can effectively eliminate the influence of the channel DC drift on the Doppler frequency measurement and improve the positioning accuracy.

Further, the center frequency of the band-pass filter A2 is f _IF , and the bandwidth is Bw, where Bw=2f _d,max , and f _d,max is the maximum value of the Doppler frequency.

Preferably, the band-pass filter B of the beacon is a passive filter, which requires no power supply and is convenient to use.

The present invention also discloses a passive beacon system used for accurate positioning of railcars, including a passive beacon device used for accurate positioning of railcars in the above technical solutions, wherein the number of the beacons is m, m is a natural number greater than 1; wherein, the interrogator is installed on the top, side or bottom of the train head, the beacon is installed on the top, side or bottom of the train track, and m beacons are respectively installed in different train running sections; when When the train passes the beacon, the transmitting antenna A1 of the interrogator can face the receiving antenna B1 of the beacon, and the receiving antenna A2 of the interrogator can face the transmitting antenna B2 of the beacon.

Further, the center frequency of the beacon is f ₀ +kΔf, and the bandwidth is less than Δf, where f ₀ is the initial frequency of the interrogation signal, k is the number of the beacon, k=0, 1, 2, 3, ..., m-1; Δf is a preset center frequency difference of the beacon; the frequency synthesizer A can generate a single-frequency radio frequency signal with a center frequency of f ₀ +kΔf.

Further, the controller can also be connected with a train dispatching system to obtain road section section information of similar vehicles.

The invention also discloses a method for accurate positioning and measurement of the railroad train, which adopts the passive beacon system in the above technical scheme to measure, including the following steps:

S1: The controller A receives the section section information from the train, and obtains the beacon number k corresponding to the current running section;

S2: The controller A controls the frequency synthesizer A to generate an interrogation signal corresponding to the beacon k, the interrogation signal is a single-frequency sine wave, and its center frequency is f ₀ +kΔf; the interrogation signal is amplified by the amplifier A and transmitted by the transmitting antenna A1;

S3: The beacon k receives the interrogation signal from the interrogator through the receiving antenna B1, the center frequency of the band-pass filter B of the beacon k is f ₀ +kΔf, and the center frequency of the interrogation signal received by the receiving antenna B1 is also f ₀ +kΔf, the interrogation signal is filtered by the band-pass filter B and forwarded back to the interrogator through the transmitting antenna B2 as a response signal;

S4: The receiving antenna B2 of the interrogator receives the reply signal from the beacon. After the reply signal is amplified by the low noise amplifier A, the frequency of the reply signal and the frequency synthesizer A generated by the mixer A is f ₀ +kΔf+f _IF The single-tone sinusoidal signal is mixed; the mixed signal is filtered by the band-pass filter A2, and the filtered signal is sampled by the analog-to-digital converter A at the sampling rate f _s and then converted into a digital signal, and then sent to the digital signal processor ;

S5: The digital signal processor calculates the speed information of the train and the time when the interrogator is facing the beacon according to the digital signal input by the analog-to-digital converter A.

Further, step S5 specifically includes the following steps:

S51: The digital signal processor firstly intercepts the digital signal in segments, and then uses digital down-conversion technology to normalize the signal, and the center frequency of the signal is converted from 2πf _IF /f _s to 0 to obtain a baseband measurement signal;

S52: Use fast Fourier transform on the baseband measurement signal to obtain the spectrum of the data segment, and then determine whether it is a valid response signal through CFAR. When the digital signal processor determines a valid response signal, obtain the spectrum from the spectrum. The frequency value corresponding to the peak, obtain and store the Doppler frequency f _di of the _ti period, where _i =1, 2, 3, _. /[2(f ₀ +kΔf)] to obtain the radial velocity variation curve of the interrogator approaching and moving away from the passive beacon, where c is the speed of light;

S53: The digital signal processor performs data fitting on the measured Doppler frequency variation values (t _i , V _i ), then obtains the corresponding time t ₀ at zero radial velocity, and uses t ₀ as the positive value of the interrogator Time output for the beacon position.

Preferably, when performing data fitting in step S53, the least squares method is used as the data fitting method.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

1. The present invention provides a passive beacon device, system and measurement method for accurate positioning of railroad trains in conjunction with the train speed measurement and positioning method. Based on the rough train running section information obtained by other train positioning methods, different sections are selected. Corresponding to different installed beacons for communication, and positioning by measuring the Doppler frequency shift of the beacon response signal, the measurement data of the existing train speed measurement and positioning method can be timely compensated and corrected to achieve high-precision positioning of rail trains ;

2. The passive beacon device, system and measurement method for accurate positioning of railroad trains of the present invention, the beacon adopts passive band-pass filter to realize frequency division multiple access, and can effectively distinguish beacons in different operating intervals;

3. The passive beacon device and system for accurate positioning of the railroad train of the present invention, the interrogator and the beacon adopt polarized orthogonal antennas, which can eliminate the influence of the background electromagnetic scattering of the beacon on the Doppler frequency measurement;

4. In the passive beacon device and system for accurate positioning of railroad trains of the present invention, the interrogator adopts a non-zero intermediate frequency structure, which can effectively eliminate the influence of channel DC drift on Doppler frequency measurement;

5. The passive beacon device, system and method for accurate positioning of railroad trains of the present invention use the Doppler frequency variation law to determine the moment when the interrogator on the train is facing the position of the beacon, and is not affected by the difference between the interrogator and the beacon. Influenced by the distance, the installation of the interrogator is more convenient;

6. The passive beacon device and system for accurate positioning of the railroad train of the present invention use passive beacons, which do not require power supply and are easy to use.

Description of drawings

The accompanying drawings described herein are used to provide further understanding of the embodiments of the present invention, and constitute a part of the present application, and do not constitute limitations to the embodiments of the present invention. In the attached image:

Fig. 1 is the composition structure diagram of the interrogator of embodiment 1 of the present invention;

Fig. 2 is the composition structure diagram of the beacon according to Embodiment 1 of the present invention;

3 is a flowchart of the method algorithm of Embodiment 2 of the present invention;

4 is a schematic diagram of an application scenario of Embodiment 2 of the present invention;

Fig. 5 is the speed change curve before and after fitting in embodiment 3 of the present invention;

FIG. 6 is a schematic structural diagram of a passive beacon system for accurate positioning of a railroad train according to Embodiment 2 of the present invention.

Detailed ways

The existing beacon detection method uses beacons as RFID beacons, which cannot avoid the problems of missed reading and misreading of radio frequency tags, and has poor anti-interference ability. The positioning accuracy depends on the antenna pattern of the RFID and the speed of the train, so it is difficult to achieve high precision. . The existing train speed measurement and positioning method is essentially the time integration of the speed, and its accuracy is affected by the speed measurement accuracy and accumulation time. Under the condition of a certain speed measurement accuracy, the positioning accuracy will decrease with the increase of the accumulation time. Therefore, the positioning system needs to cooperate with the ground beacon to timely compensate the accumulated error generated by the integration.

The present invention provides a passive beacon device, system and method for accurate positioning of rail trains in conjunction with the train speed measurement and positioning method to address the above technical problems. Based on the rough train running interval information obtained by other train positioning methods, the present invention selects different beacons installed corresponding to different intervals for communication, and presets the start and end measurement areas. The invention performs positioning by measuring the Doppler frequency shift of the beacon response signal, and can timely compensate and correct the measurement data of the existing train speed measurement and positioning method, so as to realize the high-precision positioning of the railroad train.

In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and the accompanying drawings. as a limitation of the present invention.

[Example 1]

A passive beacon device used for accurate positioning of railroad trains, comprising an interrogator and m passive beacons, where m is a natural number greater than 1. The interrogator is used to send an inquiry signal to the beacon and receive a response signal forwarded by the beacon; The beacon mainly accepts the interrogation signal of the interrogator for processing and then forwards it back to the interrogator as a response signal.

As shown in FIG. 2 , the passive beacon includes a receiving antenna B1, a band-pass filter B and a transmitting antenna B2 connected in sequence. The receiving antenna B1 can receive the interrogation signal transmitted by the transmitting antenna A1, and the received interrogation signal passes through the band-pass filter B1. After being filtered by the filter B, it is transmitted as a response signal through the transmitting antenna B2. The band-pass filter B of the beacon is a passive filter, and the center frequencies of the band-pass filters B of different passive beacons are different, so that the working frequencies of each passive beacon are also different. Specifically, the center frequency of the band-pass filter of the k-th beacon is f ₀ +kΔf, and the bandwidth is less than Δf, where f ₀ is the initial frequency of the query signal, k is the beacon number, k=0, 1, ..., m -1, the value of k for different beacons is different to distinguish different beacons. Generally speaking, one beacon is set for each train running section.

As shown in Figure 1, the interrogator includes a controller A, a frequency synthesizer A, an amplifier A, and a transmitting antenna A1 connected in sequence, wherein: the frequency synthesizer A, the amplifier A, and the transmitting antenna A1 form a transmitting channel; the interrogator also Including receiving antenna A2, band-pass filter A1, low-noise amplifier A (referred to as low-noise amplifier A), mixer A, band-pass filter A2, analog-to-digital converter A, digital signal processor A. The controller A receives the interval information from the train dispatching system, is connected with the frequency synthesizer A and the digital signal processor A, and controls the output frequency of the frequency synthesizer A and the working sequence of the digital signal processing A. The frequency synthesizer A outputs two signals with different frequencies, one is connected to the amplifier A as the transmitted radio frequency signal, and the other is connected to the mixer A as the local oscillator signal of the mixer A. Amplifier A is connected to transmit antenna A1 to transmit interrogation signals. The receiving antenna A2 receives the response signal from the beacon, and is connected to the low-noise amplifier A to amplify the response signal. The low-noise amplifier A is connected to the band-pass filter A1 to filter out the response signal. The band-pass filter A1 is connected to the mixer A. In order to realize superheterodyne reception, mixer A is connected with the band-pass filter A2 to filter out the intermediate frequency signal, and the band-pass filter A2 is connected with the analog-to-digital converter to convert the analog intermediate frequency signal into a digital intermediate frequency signal for sending. into the digital signal processor A for digital signal processing. That is, the receiving antenna A2 is used to receive the response signal of the passive beacon, and the response signal is processed by the band-pass filter A1, the low-noise amplifier A, the mixer A, the band-pass filter A2 and the analog-to-digital converter A and transmitted. To the digital signal processor A; the digital signal processor A is used to calculate the speed information of the train and the time when the interrogator is facing the beacon according to the received signal. The center frequency of the band-pass filter A2 is f _IF , and the value of f _IF can be selected according to the center frequency and the bandwidth of the commercial intermediate frequency filter to reduce the realization cost of the band-pass filter, and the bandwidth is Bw, wherein Bw= 2f _d,max , where f _d,max is the maximum value of the Doppler frequency.

In this embodiment, the frequency synthesizer A can generate different single-frequency radio frequency signals as interrogation signals under the control of the controller A, and the interrogation signals are amplified by the amplifier A and then transmitted through the transmitting antenna A1. The operating frequency of each passive beacon corresponds to at least one single-frequency radio frequency signal. When the train travels to the corresponding passive beacon, it can transmit the inquiry signal corresponding to the working frequency of the passive beacon and receive the corresponding response signal. Division multiple access can effectively distinguish beacons in different operating intervals, which is convenient for subsequent processing and calculation.

In this embodiment, the transmitting antenna A1 of the interrogator adopts X polarization, the receiving antenna A2 adopts Y polarization, the receiving antenna B1 of the passive beacon adopts X polarization, and the transmitting antenna B2 adopts Y polarization, X polarization and Y polarization Orthogonal. The interrogator and beacon use polarized orthogonal antennas, which can eliminate the influence of the background electromagnetic scattering of the beacon on the Doppler frequency measurement.

In the application of a passive beacon device used for accurate positioning of railroad trains, before use, based on the rough train running interval information obtained by other train positioning methods, different beacons installed corresponding to different intervals can be selected for communication, and The start and end measurement areas are preset, and the beacons are installed on the top, side, or bottom of the train track in the measurement area.

When in use, the interrogator is installed on the top, side, or bottom of the running train. When the train passes the corresponding beacon, the center of the interrogator transceiver antenna on the train is the same as the center of the corresponding beacon transceiver antenna on the track. Can be directly facing, that is, when the train passes the beacon, the transmitting antenna A1 of the interrogator can be facing the receiving antenna B1 of the beacon, and the receiving antenna A2 of the interrogator can be facing the transmitting antenna B2 of the beacon; Send an interrogation signal and receive a reply signal forwarded by the beacon; the beacon can receive the interrogator's interrogation signal for processing and then forward it back to the interrogator as a reply signal.

Specifically, the controller A receives the interval information from the train dispatching system, and then controls the frequency synthesizer A through the controller A to output a single-frequency radio frequency signal whose frequency corresponds to the operating frequency of the passive beacon in the corresponding interval. The single-frequency radio frequency signal passes through the amplifier A. After power amplification, the X-polarized electromagnetic wave is emitted to the beacon through the transmitting antenna A1. The passive beacon receives the inquiry signal from the interrogator through the X-polarized receiving antenna B1, and then transmits the response signal through the Y-polarized transmitting antenna B2 after the signal is frequency-selected through the band-pass filter B. When the train runs to the area near the beacon, there is a relative radial motion between the beacon and the interrogator, so the response signal transmitted by the beacon has a Doppler frequency shift f _d . The receiving antenna A2 receives the Y-polarized electromagnetic wave forwarded from the beacon, which is filtered by the band-pass filter A1 and amplified by the low-noise amplifier A, and then enters the mixer A, where it differs from another signal from the frequency synthesizer A. After the intermediate frequency is filtered by the band-pass filter A2, it is converted into a digital signal by the analog-to-digital converter A, and sent to the digital signal processor A for signal processing to obtain the speed of the train. information.

In this embodiment, the passive beacon device cooperates with the train speed measurement and positioning method to perform timely and accurate correction. Specifically, the passive beacon device uses the rough position information of the train obtained by other train positioning methods to update the train running interval information and the beacon of the corresponding interval. position, and then obtain the relative speed between the beacon and the vehicle by measuring the Doppler frequency shift of the electromagnetic wave transmitted by the ground beacon, then calculate and fit the speed-time curve of the vehicle relative to the beacon motion, and finally solve the time when the vehicle reaches the beacon position. Accurate time, to achieve accurate correction of the position of the vehicle, to achieve the acquisition of the precise position of the railroad train. The beacon used in this embodiment is a passive beacon, which is used as a transponder matched with the interrogator, does not require power supply, and is convenient to use.

In another implementation manner, the value of m may also be 1, that is, only one passive beacon is used, which is applicable to the acquisition of the precise position of the train only for a certain fixed position in a certain train running section. In some cases, if accurate correction and positioning are required at the same time in multiple running sections along the train, multiple passive beacons need to be arranged.

[Example 2]

In this embodiment, a passive beacon system for accurate positioning of railroad trains is provided. As shown in FIG. 6 , the passive beacon system includes a passive beacon device used for accurate positioning of railroad trains in Embodiment 1; the application scenario of the passive beacon system in this embodiment is shown in FIG. 4 , wherein , the interrogator is installed on the top, side or bottom of the train head, the beacon is installed on the top, side or bottom of the train track, and m beacons are installed in different train running sections; when the train passes the corresponding beacon, The transmit antenna A1 of the interrogator can face the receive antenna B1 of the beacon, and the receive antenna A2 of the interrogator can face the transmit antenna B2 of the beacon.

The center frequency of the beacon is f ₀ +kΔf, and the bandwidth is less than Δf, where f ₀ is the initial frequency of the interrogation signal, k is the number of the beacon, k=0, 1, 2, 3, ..., m-1; Δf is The center frequency difference of the preset beacon; the frequency synthesizer A can generate a single-frequency radio frequency signal with a center frequency of f ₀ +kΔf.

This embodiment also provides a method for measuring precise positioning of a railroad train, which uses the passive beacon system in this embodiment for measurement. The process is shown in FIG. 3 and includes the following steps:

S1: The controller A receives the section section information from the train from the train dispatching system, and obtains the beacon number k corresponding to the current running section;

S2: The controller A controls the frequency synthesizer A to generate an interrogation signal corresponding to the beacon k, the interrogation signal is a single-frequency sine wave, and its center frequency is f ₀ +kΔf; the interrogation signal is amplified by the amplifier A and transmitted by the transmitting antenna A1;

S3: The beacon k receives the inquiry signal from the interrogator through the X-polarized receiving antenna B1, and the beacon installed in this road section is the k-th beacon, then if the interval information is correct, the beacon k’s The center frequency of the band-pass filter B is f ₀ +kΔf, and the center frequency of the interrogation signal received by the receiving antenna B1 is also f ₀ +kΔf. Y-polarization is forwarded back to the interrogator;

S4: The Y-polarized receiving antenna B2 of the interrogator receives the response signal from the beacon. After the response signal is amplified by the low noise amplifier A, the frequency generated by the mixer A and the frequency synthesizer A is f ₀ +kΔf+ The single-tone sine signal of f _IF is mixed; the mixed signal is filtered by the band-pass filter A2, the center frequency of the mixed signal is f _IF , and after the band-pass filter A2 (its center frequency is f _IF , the bandwidth is f IF ) B _w , where B _w =2f _d,max , where f _d,max is the maximum value of the Doppler frequency) filtering to eliminate the influence of DC drift on the Doppler frequency measurement. The filtered signal is sampled by the analog-to-digital converter A at the sampling rate f _s and converted into a digital signal, and then sent to the digital signal processor;

S5: The digital signal processor calculates the speed information of the train and the time when the interrogator is facing the beacon according to the digital signal input by the analog-to-digital converter A, which specifically includes the following steps:

S51: The digital signal processor first performs data segment interception on the digital signal, and then uses digital down-conversion (DDC) technology to normalize the signal, and the center frequency of the signal is converted from 2πf _IF /f _s to 0 to obtain a baseband measurement signal;

S52: Use fast Fourier transform (FFT) on the baseband measurement signal to obtain the spectrum of the data segment, and then determine whether it is a valid response signal through CFAR. Take the frequency value corresponding to its spectral peak, obtain and store the Doppler frequency f _di in the ti period, where _i = 1, 2, 3, ..., until the effective response signal cannot be received, and then use the formula V _di =cf _di /[2(f ₀ +kΔf)] to obtain the radial velocity variation curve of the interrogator approaching and moving away from the passive beacon, where c is the speed of light;

S53: The digital signal processor uses the least squares method to perform data fitting on the measured Doppler frequency change values (t _i , V _i ), and then obtains the corresponding moment at zero radial velocity (ie V _di =0) t ₀ , and output t ₀ as the moment when the interrogator is facing the position of the beacon.

Algorithms such as data segment interception, digital down-conversion, fast Fourier transform, CFAR judgment, frequency values corresponding to spectral peaks in the frequency spectrum, Doppler frequency shift for target positioning, and least squares method used in this embodiment These are all calculation methods well known in the art, and the specific algorithms thereof will not be repeated in this embodiment.

[Example 3]

In order to further illustrate the parameters and signal processing process of the present invention, the following specific examples of methods for bringing in numerical values are given:

As shown in Figure 1, the controller A receives the travel section information from the train, and obtains the beacon number k=0 of this section; the controller A configures the frequency synthesizer A according to the section information of the train running at this time; the frequency synthesizer A The query signal corresponding to the interval beacon is generated, and the signal frequency is f ₀ +kΔf. In this embodiment, the initial frequency f ₀ =8GHz, and the frequency interval Δf = 10MHz, so the frequency of the query signal is 8GHz. Transmitting antenna A1 transmits. The transmitting antenna A adopts horizontal polarization, that is, X polarization.

As shown in Figure 2, the beacon installed in this section of the train is the No. 0 beacon, the center frequency of the band-pass filter is 8GHz, and the bandwidth is 5MHz. After the inquiry signal is received by the beacon receiving antenna B1, it is filtered by the band-pass filter B, and the response signal is forwarded by the transmitting antenna B2. The beacon receiving antenna B1 adopts horizontal polarization, and the beacon transmitting antenna B2 adopts vertical polarization, that is, Y polarization. Assuming that the maximum speed of the train is 60m/s, the corresponding maximum Doppler frequency shift is 1600Hz, all of which fall within the passband of the bandpass filter B.

The reply signal is received by the receiving antenna A2, and the receiving antenna A2 adopts vertical polarization. The signal output by the receiving antenna A2 is amplified by the low-noise amplifier A, filtered by the band-pass filter A1, and then output to the mixer A. The mixer A mixes the received signal with the local oscillator signal generated by the frequency synthesizer A. The frequency of the local oscillator signal is 8.006GHz, and the frequency of the output intermediate frequency signal is f _IF =6MHz, which is filtered by the band-pass filter A2. Bandpass filter A2 has a center frequency of 6MHz and a bandwidth of 1MHz, which is greater than the maximum Doppler frequency offset of the beacon device. The signal output by the band-pass filter A2 is sampled by the analog-to-digital converter A with a sampling rate of 15MHz, and the digital intermediate frequency signal after sampling and conversion is output to the digital signal processor A for processing.

The signal processing flow in the digital signal processor A of the present invention is shown in FIG. 3 . In the following, it is assumed that the train has run into the antenna beam range of the preset No. 0 beacon, and the position of the beacon is taken as the coordinate origin, and the direction of the train is the positive direction of the Y-axis to establish a two-dimensional Cartesian coordinate system, that is, approaching the beacon. When it is on the negative half-axis of the Y-axis, when it is far from the beacon, it is on the positive half-axis of the Y-axis. The parameter information of the train operation at this time is as follows: the speed of the train relative to the ground is 50m/ _s , and the corresponding L ₀ = -25m, the minus sign indicates that the interrogator is located at the negative half-axis of the Y-axis at this time, h ₀ =3m, as shown in FIG. 4 .

The digital signal processor takes the data of m=150000 sampling points (ie 10ms) starting sampling at time t _i , as the data segment of a speed measurement, i=1, 2, 3...N, that is, N=50 data in total. data segment. Assuming that the first acquisition time t ₁ =0, the starting time t _i =0.01*(i-1) seconds of each measurement.

The digital signal processor performs digital down-conversion on the sampled data of 150,000 points, and decimates it by 750 times to obtain a baseband signal with a sampling rate of f=20kHz. The length of the signal data obtained after decimation is 200, and 1024-point FFT is performed after filling 0 to obtain the spectrum corresponding to the baseband signal.

The spectral peaks of the spectrum are searched between the 1st point and the 512th point of the FFT result to find the Doppler shift _fdi . Assuming that the spectral peak is at the position of the kth point, f _di =k/(1024*20000).

The digital signal processor calculates the relative velocity V _di of the interrogator and the beacon at time ti according to _{V di} =cf _d /[2(f ₀ +kΔf)]. In this embodiment, the frequency of the transmitted signal is 8 GHz.

The digital signal processor performs data fitting on the relative motion speed V _di obtained by each measurement combined with the sampling time t _i , as shown in Figure 4, the mathematical model of the speed change is V _di =Vsin{arctan[(L ₀ + Vt _i )/h]}, in this embodiment, the least squares method is used to estimate the parameters V, L ₀ , and h to obtain the fitted V _di , as shown in FIG. 5 .

Fig. 5 is the velocity change curve before and after fitting, the solid line in Fig. 5 is the _{V di} -ti curve with noise, and the dashed line is the _{V di} -ti curve after fitting. It can be seen from Fig. 5 that if the measured V _di -t _i with noise is used to directly solve t ₀ , the obtained result obviously has a large error. The point closest to V _di =0 after fitting corresponds to t _i =0.48s, that is, t ₀ =0.48s.

The specific embodiments described above further describe the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention, and are not intended to limit the scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. The passive beacon device for precisely positioning the rail train is characterized by comprising an interrogator and at least 1 passive beacon;

the passive beacons comprise a receiving antenna B1, a band-pass filter B and a transmitting antenna B2 which are connected in sequence, and the center frequencies of the band-pass filters B of different passive beacons are different;

the interrogator comprises a controller A, a frequency synthesizer A, a digital signal processor A, a transmitting antenna A1 and a receiving antenna A2;

the frequency synthesizer can generate different single-frequency radio-frequency signals as an inquiry signal under the control of the controller A and transmits the inquiry signal through a transmitting antenna A1, and the working frequency of each passive beacon at least corresponds to one single-frequency radio-frequency signal; the receiving antenna B1 can receive the inquiry signal transmitted by the transmitting antenna A1, and the received inquiry signal is filtered by the band-pass filter B and then transmitted as a response signal through the transmitting antenna B2; the receiving antenna A2 is used for receiving the response signal of the passive beacon and transmitting the response signal to the digital signal processor A; the digital signal processor A is used for calculating the speed information of the train and the time when the interrogator faces the beacon according to the received signals.

2. The passive beacon device for precise positioning of rail trains of claim 1, wherein the polarization of the transmitting antenna a1 and the receiving antenna B1 are the same, the polarization of the transmitting antenna B2 and the receiving antenna a2 are the same, and the polarization of the transmitting antenna B1 and the polarization of the transmitting antenna B2 are orthogonal; the polarizations of the transmit antenna a1 and the receive antenna a2 are orthogonal.

3. The passive beacon device for precise location of a railcar according to claim 1, wherein said interrogator further comprises amplifier a, band pass filter a1, low noise amplifier a, mixer a, band pass filter a2, analog to digital converter a; the amplifier A is connected between the frequency synthesizer A and a transmitting antenna A1; the receiving antenna A2, the low noise amplifier A, the mixer A, the band-pass filter A2, the analog-to-digital converter A and the digital signal processor A are connected in sequence; the frequency synthesizer is also connected with the frequency mixer A and provides a local oscillation signal for the frequency mixer A.

4. A passive beacon device for precise location of a railcar according to any one of claims 1 to 3, wherein the band pass filter B of the beacon is a passive filter.

5. A passive beacon system for precise positioning of a rail train, comprising the passive beacon device for precise positioning of a rail train of claim 3, wherein the number of beacons is m, and m is a natural number greater than 1; the interrogator is arranged at the top, the side or the bottom of the train head, the beacons are arranged at the top, the side or the bottom of the train track, and the m beacons are respectively arranged in different train running areas; when the train passes the beacon, the interrogator's transmitting antenna a1 can be directly opposite the beacon's receiving antenna B1 and the interrogator's receiving antenna a2 can be directly opposite the beacon's transmitting antenna B2.

6. The passive beacon system for precise location of a railcar according to claim 5, wherein said beacon has a center frequency f₀+ k Δ f, bandwidth less than Δ f, where f₀K is the number of the beacon, and k is 0, 1, 2, 3, …, m-1; Δ f is a preset central frequency difference of the beacon; the frequency synthesizer A can generate a center frequency f₀A single frequency radio frequency signal of + k Δ f.

7. The passive beacon system for precise location of a railcar according to claim 6, wherein the controller is further capable of interfacing with a train dispatching system to obtain railcar-like road segment interval information.

8. A method for accurate positioning measurement of a railway train, using the passive beacon system of claim 7, comprising the steps of:

s1: the method comprises the steps that a controller A receives section interval information from a train and obtains a beacon number k corresponding to a current running section;

s2: the controller A controls the frequency synthesizer A to generate an interrogation signal corresponding to the beacon k, wherein the interrogation signal is a single-frequency sine wave with the center frequency f₀+ k Δ f; the interrogation signal is amplified by amplifier A and transmitted by transmitting antenna A1;

s3: beacon k receives an interrogation signal from an interrogator via a receiving antenna B1, with a bandpass filter B of beacon k having a center frequency f₀+ k Δ f, the center frequency of the interrogation signal received by receiving antenna B1 is also f₀+ k Δ f, the interrogation signal is filtered by the band-pass filter B and forwarded as a response signal via the transmitting antenna B2 back to the interrogator;

s4: the receiving antenna B2 of the interrogator receives the response signal from the beaconAfter being amplified by the low noise amplifier A, the frequency f generated by the mixer A and the response signal and the frequency synthesizer A₀+kΔf+f_IFMixing the single-tone sinusoidal signals; the mixed signal is filtered by a band-pass filter A2, and the filtered signal is processed by an analog-to-digital converter A at a sampling rate f_sAfter sampling, converting the signal into a digital signal, and sending the digital signal to a digital signal processor, wherein f_IFIs the center frequency of bandpass filter a 2;

s5: the digital signal processor calculates the speed information of the train and the time when the interrogator faces the beacon according to the digital signal input by the analog-to-digital converter A.

9. The precise positioning and measuring method for a rail train according to claim 8, wherein the step S5 specifically includes the steps of:

s51: the digital signal processor firstly carries out data segmentation interception on the digital signal, then normalizes the signal by adopting a digital down-conversion technology, and the central frequency of the signal is 2 pi f_IF/f_sConverting to 0 to obtain a baseband measurement signal;

s52: obtaining the frequency spectrum of the data section by adopting fast Fourier transform to the baseband measurement signal, then judging whether the signal is an effective response signal or not through CFAR, and after the digital signal processor judges the effective response signal, obtaining the frequency value corresponding to the spectrum peak from the frequency spectrum, obtaining and storing t_iDoppler frequency f of the time interval_diWhere i is 1, 2, 3, …, until a valid reply signal cannot be received, then equation V is reused_di＝cf_di/[2(f₀+kΔf)]Obtaining a radial velocity profile of the interrogator approaching and departing the passive beacon, wherein c is the speed of light;

s53: digital signal processor measures Doppler frequency variation value (t)_i,V_i) Fitting the data and then finding the corresponding time t at zero radial velocity₀And will t₀Output as the moment the interrogator is facing the beacon location.

10. The precise positioning and measuring method for the rail train according to claim 9, wherein the least square method is adopted as the data fitting method when the data fitting is performed in step S53.

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