CN107561491B - Passive beacon device, system and measuring method for precisely positioning rail train - Google Patents
Passive beacon device, system and measuring method for precisely positioning rail train Download PDFInfo
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- CN107561491B CN107561491B CN201710731620.6A CN201710731620A CN107561491B CN 107561491 B CN107561491 B CN 107561491B CN 201710731620 A CN201710731620 A CN 201710731620A CN 107561491 B CN107561491 B CN 107561491B
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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
Technical Field
The invention relates to the field of rail transit and positioning, in particular to a passive beacon device, a passive beacon system and a passive beacon measuring method for accurately positioning a rail train.
Background
The rail train is positioned, namely the physical position of the train on the rail is accurately obtained, so that the driving safety and efficiency can be effectively improved. The existing main method for train positioning comprises the following steps: a track circuit positioning method, a ground beacon method, a cross cable loop positioning method and a speed measurement positioning method.
In the existing ground beacon method, beacons are mainly divided into an active beacon and a passive beacon. The beacon is installed in a station or along a track such as each track partition. When the train passes through, the ground beacon is aligned with the vehicle-mounted corresponding equipment, the vehicle-mounted equipment transmits the beacon corresponding signal in the form of electromagnetic waves, the beacon starts to work after receiving the signal transmitted by the vehicle-mounted equipment, the current absolute physical position information of the train is transmitted back to the train, and the vehicle-mounted equipment obtains the position information of the train.
In the existing beacon detection method, for example, a beacon detection method for train positioning (publication number: CN104554350B) disclosed in chinese patent "beacon detection method in train positioning process", a beacon is used as an RFID beacon, and a device determines whether an antenna is located in a certain beacon window by searching and determining whether a train passes through the position of the corresponding beacon, thereby obtaining position information of the train. The method can not avoid the problems of the missed reading and the misreading of the radio frequency tag, has poor anti-jamming capability, has positioning accuracy depending on an antenna directional diagram of the RFID and train speed, and is difficult to realize high accuracy.
The existing train speed measurement positioning method is to measure the running instant speed of a train and integrate the speed to obtain the running distance of the train, thereby realizing the positioning of the train. The current speed measurement method comprises wheel shaft rotation information speed measurement, Doppler radar speed measurement and GPS speed measurement. The method of using velocity measurement positioning is essentially time integration of velocity, the accuracy of which is affected by the accuracy of velocity measurement and the accumulated time. Under the condition of certain speed measurement accuracy, the positioning accuracy is reduced along with the increase of the accumulation time.
Disclosure of Invention
The invention aims to solve the technical problem that the positioning accuracy is reduced along with the increase of accumulated time in a train speed measurement positioning method, and aims to provide a passive beacon device, a system and a measurement method for accurately positioning a rail train.
The invention is realized by the following technical scheme:
a passive beacon device for precise positioning of a rail train comprises 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.
In the use of the passive beacon device in the technical scheme, in order to ensure the positioning accuracy and the real-time performance, m beacons are pre-installed at the top, the side or the bottom of a track along which a train runs, and the number k of the beacons takes the value of 1, 2, 3, … and m. The interrogator is arranged on the train and transmits a speed measurement signal, the speed measurement signal is forwarded by a beacon corresponding to the position of the train and then returns to the interrogator, and the interrogator obtains the Doppler frequency shift f of the interrogator relative to the corresponding beacon by measuring the Doppler frequency shift generated by the received signaldAnd finally, the interrogator calculates the change rule of the Doppler frequency shift of the beacon to calculate the moment when the interrogator is opposite to the beacon position, and the position of the train at the moment can be accurately determined by calculating the moment when the interrogator is opposite to the beacon position because the position of the beacon is known, so that the train can be accurately positioned.
As a further improvement of the present invention, 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 polarization of the transmitting antenna A1 and the receiving antenna A2 are orthogonal; the influence of background electromagnetic scattering of the beacon on Doppler frequency measurement can be eliminated, and the train positioning precision is improved.
As a further improvement of the invention, the interrogator further comprises an amplifier a, a band pass filter a1, a low noise amplifier a, a mixer a, a band pass filter a2, an 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. In the scheme, the interrogator adopts a non-zero intermediate frequency structure, so that the influence of channel direct current drift on Doppler frequency measurement can be effectively eliminated, and the positioning precision is improved.
Further, the center frequency of the band-pass filter A2 is fIFThe bandwidth is Bw, wherein Bw is 2fd,max，fd,maxIs the maximum value of the doppler frequency.
Preferably, the band-pass filter B of the beacon is a passive filter, power supply is not needed, and the use is convenient.
The invention also discloses a passive beacon system for accurately positioning the rail train, which comprises the passive beacon device for accurately positioning the rail train in the technical scheme, wherein the number of the beacons is m, and m is a natural number more 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.
Further, the center frequency of the beacon is 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.
Further, the controller can be connected with a train dispatching system to acquire the section and section information of the similar train.
The invention also discloses a precise positioning and measuring method for the rail train, which adopts the passive beacon system in the technical scheme to carry out measurement and comprises the following steps:
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 beacon, the response signal is amplified by the low noise amplifier A, and the frequency f generated by the mixer A and the frequency synthesizer A is obtained0+kΔf+fIFMixing 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 fsSampling, converting into digital signals, and sending the digital signals to a digital signal processor;
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.
Further, step S5 specifically includes the following steps:
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 fIF/fsConverting to 0 to obtain a baseband measurement signal;
s52: fast Fourier transform is carried out on the baseband measurement signal to obtain the frequency spectrum of the data section, and then whether the baseband measurement signal is a valid response signal or not is judged through CFARAfter the digital signal processor judges the effective response signal, the frequency value corresponding to the spectrum peak is obtained from the frequency spectrum, and t is obtained and storediDoppler frequency f of the time intervaldiWhere i is 1, 2, 3, …, until a valid reply signal cannot be received, then equation V is reuseddi＝cfdi/[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,Vi) 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.
Preferably, when data fitting is performed in step S53, a least squares method is used as the data fitting method.
Compared with the prior art, the invention has the following advantages and beneficial effects:
1. the invention provides a passive beacon device, a system and a measurement method for accurately positioning a rail train by matching with a train speed measurement positioning method, wherein different beacons correspondingly installed in different intervals are selected for communication based on rough train running interval information obtained by other train positioning methods, and positioning is carried out by measuring Doppler frequency shift of beacon response signals, so that measurement data of the existing train speed measurement positioning method can be compensated and corrected timely, and high-precision positioning of the rail train is realized;
2. the invention relates to a passive beacon device, a system and a measuring method for accurately positioning a rail train, wherein a passive band-pass filter is adopted for realizing frequency division multiple access of beacons, so that beacons in different running intervals can be effectively distinguished;
3. according to the passive beacon device and the passive beacon system for accurately positioning the rail train, the interrogator and the beacon adopt the polarized orthogonal antenna, so that the influence of background electromagnetic scattering of the beacon on Doppler frequency measurement can be eliminated;
4. in the passive beacon device and the passive beacon system for accurately positioning the rail train, the interrogator adopts a non-zero intermediate frequency structure, so that the influence of channel direct current drift on Doppler frequency measurement can be effectively eliminated;
5. the passive beacon device, the passive beacon system and the passive beacon method for accurately positioning the rail train judge the moment when the interrogator on the train is over against the beacon position by using the Doppler frequency change rule, are not influenced by the distance between the interrogator and the beacon, and are more convenient to install;
6. the passive beacon device and the passive beacon system for accurately positioning the rail train adopt the passive beacon, do not need power supply and are convenient to use.
Drawings
The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention. In the drawings:
FIG. 1 is a constitutional structural view of an interrogator according to embodiment 1 of the invention;
fig. 2 is a constitutional structure diagram of a beacon of embodiment 1 of the present invention;
FIG. 3 is a flowchart of the algorithm of the method of embodiment 2 of the present invention;
fig. 4 is a schematic view of an application scenario of embodiment 2 of the present invention;
FIG. 5 is a velocity profile before and after fitting in example 3 of the present invention;
fig. 6 is a schematic structural diagram of a passive beacon system for accurately positioning a rail train according to embodiment 2 of the present invention.
Detailed Description
The existing beacon detection method adopts the beacon as the RFID beacon, can not avoid the problems of the missed reading and the misreading of the radio frequency label, has poor anti-jamming capability, has positioning accuracy depending on the antenna directional diagram of the RFID and the train speed, and is difficult to realize high accuracy. The existing train speed measurement positioning method is essentially time integration of speed, and the precision of the method is influenced by speed measurement precision and accumulated time. Under the condition of certain speed measurement precision, the positioning precision is reduced along with the increase of the accumulation time, and therefore the positioning system needs to be matched with a ground beacon to timely compensate the accumulation error generated by integration.
The invention provides a passive beacon device, a system and a method for accurately positioning a rail train by matching with a train speed measurement positioning method aiming at the technical problems. According to the invention, based on rough train operation interval information obtained by other train positioning methods, different beacons correspondingly installed in different intervals are selected for communication, and measurement starting areas and measurement ending areas are preset. The method carries out positioning by measuring the Doppler frequency shift of the beacon response signal, and can carry out timely compensation and correction on the measured data of the conventional train speed measurement positioning method so as to realize high-precision positioning of the rail train.
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to examples and accompanying drawings, and the exemplary embodiments and descriptions thereof are only used for explaining the present invention and are not meant to limit the present invention.
[ example 1 ]
A passive beacon device for accurately positioning a rail train comprises an interrogator and m passive beacons, wherein the interrogator with m being a natural number larger than 1 is used for sending an interrogation signal to the beacons and receiving response signals forwarded by the beacons; the beacon is mainly used for receiving and processing an inquiry signal of the interrogator and then transmitting the inquiry signal 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 an interrogation signal transmitted by the transmitting antenna a1, and the received interrogation signal is filtered by the band-pass filter B and then 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 the passive beacons are also different. Specifically, the center frequency of the bandpass filter of the kth beacon is f0+ k Δ f, bandwidth less than Δ f, where f0For the initial frequency of the query signal, k is the beacon number, k is 0, 1, …, and m-1, and k is different in value for different beacons to distinguish the different beacons. Generally, one beacon is set for each train operating interval.
As shown in fig. 1, the interrogator includes a controller a, a frequency synthesizer a, an amplifier a, 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 comprises a receiving antenna A2, a band-pass filter A1, a low noise amplifier A (low noise amplifier A for short), a mixer A, a band-pass filter A2, an analog-to-digital converter A and a digital signal processor A which form a receiving and processing channel. 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 time sequence of the digital signal processor A. The frequency synthesizer A outputs two paths of signals with different frequencies, one path is connected with the amplifier A and used as a transmitted radio frequency signal, and the other path is connected with the frequency mixer A and used as a local oscillation signal of the frequency mixer A. Amplifier a is connected to transmit antenna a1 for transmitting the interrogation signal. The receiving antenna a2 receives the reply signal from the beacon, and is connected to the low noise amplifier a to amplify the reply signal, the low noise amplifier a is connected to the band pass filter a1 to filter out the reply signal, the band pass filter a1 is connected to the mixer a to implement superheterodyne reception, the mixer a is connected to the band pass filter a2 to filter out the intermediate frequency signal, and the band pass filter a2 is connected to the analog-to-digital converter to convert the analog intermediate frequency signal into a digital intermediate frequency signal to be sent to the digital signal processor a for digital signal processing. That is, the receiving antenna a2 is used for receiving 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 then transmitted 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. The center frequency of the band-pass filter A2 is fIF,fIFThe value can be selected according to the center frequency and the bandwidth of the commercial intermediate frequency filter to reduce the implementation cost of the band-pass filter, and the bandwidth is Bw, wherein Bw is 2fd,max，fd,maxIs the maximum value of the doppler frequency.
In this embodiment, the frequency synthesizer a can generate different single-frequency radio frequency signals as an interrogation signal under the control of the controller a, and the interrogation signal is amplified by the amplifier a and then transmitted through the transmitting antenna a 1. The operating frequency of each passive beacon corresponds to at least one single frequency radio frequency signal. When the train runs to the corresponding passive beacon, the train can transmit an inquiry signal corresponding to the working frequency of the passive beacon and receive a corresponding response signal, and meanwhile, the design also realizes frequency division multiple access through the passive band-pass filter B, so that beacons in different running intervals can be effectively distinguished, and subsequent processing and calculation are facilitated.
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, and the X polarization and the Y polarization are orthogonal. The interrogator and the beacon adopt a polarized orthogonal antenna, and the influence of background electromagnetic scattering of the beacon on Doppler frequency measurement can be eliminated.
Before the passive beacon device is used, different beacons correspondingly installed in different intervals can be selected for communication based on rough train running interval information obtained by other train positioning methods, a measurement starting area and a measurement ending area are preset, and the beacons are installed at the top, the side or the bottom of a train track in the measurement area.
When the train passes through the corresponding beacon, the center of the interrogator transmitting and receiving antenna on the train can be opposite to the center of the corresponding beacon transmitting and receiving antenna on the track, namely when the train passes through the beacon, the transmitting antenna A1 of the interrogator can be opposite to the receiving antenna B1 of the beacon, and the receiving antenna A2 of the interrogator can be opposite to the transmitting antenna B2 of the beacon; enabling the interrogator to send an interrogation signal to the beacon and receive a reply signal forwarded back by the beacon; the beacon can receive and process the inquiry signal of the interrogator and then transmit the processed inquiry signal back to the interrogator as a response signal.
Specifically, the controller A receives interval information from a train dispatching system, and then the controller A controls the frequency synthesizer A to output a single frequency corresponding to the working frequency of the passive beacon in the corresponding intervalThe single-frequency radio frequency signal is subjected to power amplification through an amplifier A, and then an X-polarized electromagnetic wave is emitted to the beacon through a transmitting antenna A1. The passive beacon receives the inquiry signal from the interrogator through the receiving antenna B1 with X polarization, and then the response signal is retransmitted by the transmitting antenna B2 with Y polarization after the frequency of the signal is selected through the band-pass filter B. Because of the relative movement in radial direction between the beacon and the interrogator when the train runs to the area near the beacon, the response signal forwarded by the beacon has Doppler frequency shift fd. The receiving antenna A2 receives Y-polarized electromagnetic waves forwarded by the beacon, the Y-polarized electromagnetic waves are subjected to frequency selection filtering by the band-pass filter A1 and amplification by the low-noise amplifier A, then enter the mixer A, are subjected to difference frequency with another signal from the frequency synthesizer A to complete non-zero intermediate frequency superheterodyne receiving, are subjected to intermediate frequency filtering by the band-pass filter A2, are converted into digital signals by the analog-to-digital converter A, and are sent to the digital signal processor A to be subjected to signal processing so as to obtain speed information of the train.
In the embodiment, the passive beacon device is matched with a train speed measurement positioning method for timely and accurately correcting, specifically, the passive beacon device updates train operation interval information and a beacon position of a corresponding interval by using train rough position information obtained by other train positioning methods, then obtains the relative speed of a beacon and a vehicle by measuring the Doppler frequency shift of electromagnetic waves forwarded by a ground beacon, calculates and fits a speed-time curve of the vehicle relative to the movement of the beacon, and finally solves the accurate moment when the vehicle reaches the beacon position, so that the accurate correction of the position of the vehicle is realized, and the accurate position of the rail train is obtained. The beacon used in the embodiment is a passive beacon to be used as a transponder matched with the interrogator, power supply is not needed, and the use is convenient.
In another embodiment, the value of m may also be 1, that is, only 1 passive beacon is adopted, which is suitable for the case where the precise position of the train is obtained only from a certain fixed position in a certain train operation interval, and if precise correction and positioning are required to be performed simultaneously in multiple operation intervals along the train, multiple passive beacons need to be arranged.
[ example 2 ]
The present embodiment provides a passive beacon system for precise positioning of a rail train. As shown in fig. 6, the passive beacon system includes a passive beacon device for precise positioning of a rail train in embodiment 1; an application scenario of the passive beacon system in this embodiment is shown in fig. 4, where the interrogator is installed at the top, side, or bottom of the train head, the beacons are installed at the top, side, or bottom of the train track, and the m beacons are respectively installed in different train running intervals; when a train passes through the corresponding beacon, the interrogator's transmitting antenna a1 can be aligned with the beacon's receiving antenna B1, and the interrogator's receiving antenna a2 can be aligned with the beacon's transmitting antenna B2.
The center frequency of the beacon is 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.
The embodiment also provides a precise positioning and measuring method for a rail train, which uses the passive beacon system in the embodiment to perform measurement, and the flow of the method is shown in fig. 3, and includes the following steps:
s1: the method comprises the steps that a controller A receives section interval information from a train scheduling system, 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: if beacon k receives an interrogation signal from an interrogator via X-polarized receiving antenna B1 and the beacon installed in the section of the link is kth beacon, the center frequency of bandpass filter B of beacon k is f when the section information is correct0+ 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 then transmitted as a response signal back to the interrogator through the transmitting antenna B2 in the Y polarization mode;
s4: the Y-polarization receiving antenna B2 of the interrogator receives the response signal from the beacon, the response signal is amplified by the low noise amplifier A, and the frequency f generated by the frequency synthesizer A is the response signal and the frequency mixer A0+kΔf+fIFMixing the single-tone sinusoidal signals; the mixed signal is filtered by a band-pass filter A2, and the center frequency of the mixed signal is fIFThrough a band-pass filter A2 (centered at a frequency f)IFBandwidth of BwIn which B isw＝2fd,max，fd,maxThe maximum value of the doppler frequency) to remove the effect of the dc drift on the doppler frequency measurement. The filtered signal is passed through an analog-to-digital converter A at a sampling rate fsSampling, converting into digital signals, and sending the digital signals to a digital signal processor;
s5: the digital signal processor calculates the speed information of the train and the time when the interrogator is facing to the beacon according to the digital signal input by the analog-to-digital converter A, and the method specifically comprises the following steps:
s51: the digital signal processor firstly intercepts digital signals in a data segmentation way, then normalizes the signals by adopting a digital down-conversion (DDC) technology, and the central frequency of the signals is 2 pi fIF/fsConverting to 0 to obtain a baseband measurement signal;
s52: fast Fourier Transform (FFT) is adopted for the baseband measurement signal to obtain the frequency spectrum of the data section, then whether the baseband measurement signal is an effective response signal or not is judged through CFAR, after the digital signal processor judges the effective response signal, the frequency value corresponding to the spectrum peak is obtained from the frequency spectrum, and t is obtained and storediDoppler frequency f of the time intervaldiWhere i is 1, 2, 3, …, until a valid reply signal cannot be received, then equation V is reuseddi＝cfdi/[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: the digital signal processor uses least square method to measure the Doppler frequency variation value (t)i,Vi) Fitting the data and then finding the zero radial velocity (i.e., V)di0) corresponding time t0And will t0Output as the moment the interrogator is facing the beacon location.
Algorithms such as data segmentation interception, digital down conversion, fast fourier transform, CFAR decision, frequency value corresponding to a spectral peak in a frequency spectrum, doppler shift for target positioning, least square method, and the like used in this embodiment are well-known calculation methods in the art, and detailed description of the algorithms is omitted in this embodiment.
[ example 3 ]
To further illustrate the parameters and the signal processing procedures of the present invention, the following specific examples of methods for introducing numerical values are given:
as shown in fig. 1, the controller a receives travel section information from a train, and obtains a beacon number k of the section as 0; the controller A is used for configuring a frequency synthesizer A according to the section information of the train running at the moment; the frequency synthesizer A generates a query signal corresponding to the interval beacon, the signal frequency is f0+ k Δ f, in this embodiment, the initial frequency f0Since the frequency interval Δ f is 10MHz at 8GHz, the interrogation signal frequency is 8GHz, amplified by the amplifier a, and transmitted by the transmitting antenna a 1. The transmitting antenna a employs horizontal polarization, i.e., X polarization.
As shown in fig. 2, the beacon installed in the interval of train operation is beacon No. 0, the center frequency of the band-pass filter is 8GHz, and the bandwidth is 5 MHz. After being received by the beacon receiving antenna B1, the inquiry signal is filtered by the band-pass filter B and is forwarded out of the response signal by the transmitting antenna B2. Beacon receive antenna B1 employs horizontal polarization and beacon transmit antenna B2 employs vertical polarization, i.e., Y polarization. Assuming a maximum speed of 60m/s of train operation, the corresponding maximum doppler frequency shift is 1600Hz, all falling within the pass band of the band pass filter B.
The reply signal is received via a receive antenna a2, which employs vertical polarization for receive antenna a 2. The signal output by the receiving antenna a2 is amplified by the low noise amplifier a, filtered by the band pass filter a1 and output to the mixer a. The frequency mixer A mixes the received signal with a 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 fIF6MHz, filtered by a band pass filter a 2. Band-pass filterThe center frequency of the filter a2 is 6MHz, the bandwidth is 1MHz, and is greater than the maximum doppler frequency shift of the beacon device. The signal output by the band-pass filter A2 is sampled by an analog-to-digital converter A, the sampling rate is 15MHz, and the digital intermediate frequency signal after sampling conversion is output to a 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. The following assumes that the train has moved to the antenna beam range of the preset beacon No. 0, the position of the beacon is taken as the origin of coordinates, the train moving direction is taken as the positive direction of the Y axis, a two-dimensional rectangular coordinate system is established, that is, the negative half shaft of the Y axis is when the train approaches the beacon, and the positive half shaft of the Y axis is when the train leaves the beacon, and the parameter information of the train operation is as follows: the speed of the train running relative to the ground is 50m/s, t1Corresponding L0Negative sign-25 m, representing the interrogator now being located on the negative half-axis of the Y-axis, h03m as shown in fig. 4.
Digital signal processor fetch tiThe data (i.e., 10ms) of 150000 sampling points at the beginning of sampling is the data segment of one speed measurement, i is 1, 2, 3 … … N, i.e., N is 50 data segments in total. Let the time t of the first acquisition 10, the starting time t of each measurementi0.01 × (i-1) sec.
The digital signal processor performs digital down-conversion on the sampled data of 150000 points, and performs extraction by 750 times to obtain a baseband signal with a sampling rate f being 20 kHz. The length of the signal data obtained after extraction is 200, and after 0 is supplemented, 1024-point FFT is carried out to obtain the frequency spectrum corresponding to the baseband signal.
Searching the spectrum peak between the 1 st point and the 512 th point of the FFT result to obtain the Doppler frequency shift fdi. Assuming the position of the spectral peak at the k-th point, fdi＝k/(1024*20000)。
Digital signal processor according to Vdi＝cfd/[2(f0+kΔf)]Solution of tiRelative movement velocity V of time interrogator and beacondiIn this embodiment, the frequency of the transmission signal is 8 GHz.
The digital signal processor obtains the phase of each measurementFor the velocity V of movementdiCombined with the sampling instant tiFitting the data, as shown in FIG. 4, with a mathematical model of the velocity change of Vdi＝Vsin{arctan[(L0+Vti)/h]In this embodiment, least squares are used for the parameter V, L0H, estimating to obtain the fitted VdiAs shown in fig. 5.
FIG. 5 is a velocity profile before and after fitting, and the solid line in FIG. 5 is V with noisedi-tiCurve, dotted line is fitted Vdi-tiCurve line. As can be seen from FIG. 5, the noisy V is obtained directly from the measurementdi-tiGo directly to solve for t0The results obtained are clearly subject to large errors. Closest to V after fittingdi Point corresponding t 0i0.48s, i.e. t0＝0.48s。
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are merely exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the 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+fIFMixing 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 fsAfter sampling, converting the signal into a digital signal, and sending the digital signal to a digital signal processor, wherein fIFIs 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 fIF/fsConverting 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 tiDoppler frequency f of the time intervaldiWhere i is 1, 2, 3, …, until a valid reply signal cannot be received, then equation V is reuseddi＝cfdi/[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,Vi) 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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| CN110346295B (en) * | 2019-07-15 | 2022-03-04 | 北京神州同正科技有限公司 | Defect composite positioning method and device, equipment and storage medium |
| CN111929670B (en) * | 2020-07-28 | 2023-12-29 | 胡运成 | Rail transit train speed measurement method and system |
| CN114435430B (en) * | 2020-11-02 | 2023-07-14 | 比亚迪股份有限公司 | Method, system, equipment and medium for compensating and correcting positioning error of transponder |
| CN114866104B (en) * | 2020-12-31 | 2024-04-05 | 福建星海通信科技有限公司 | Communication method and storage medium of non-directional beacon device |
| CN113562031B (en) * | 2021-08-04 | 2022-10-11 | 电子科技大学 | System and method for positioning rail train tunnel by using communication signal |
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