Urban rail signal system train positioning method based on 900M frequency wireless ASK coding

Abstract

The invention discloses an urban rail signal system train positioning method based on 900M frequency wireless ASK coding, and the method comprises the steps: transmitting a single-frequency signal through 900M radio frequency equipment, receiving the 900M signal through RFID equipment, transmitting a modulated wireless signal to 900M demodulation equipment, and carrying out ASK demodulation through the 900M demodulation equipment to obtain a most original digital baseband signal; after obtaining the original coded data, decoding the original coded data; checking whether a frame of complete data is received, and if the frame of complete data is incomplete data, discarding the whole packet of data; and the antenna equipment sets the specific IO as a high level after receiving a correct data frame, and if the correct data frame is not received, the antenna equipment sets the specific IO as a low level, and the antenna equipment enters the radio frequency field. According to the method, high-precision central point judgment is realized through multiple measures such as hardware, coding logic, verification logic and central point moment calculation.

Description

Technical Field

[0001] The present invention relates to the technical field of train positioning methods, and specifically to an urban rail signal system train positioning method based on 900M frequency wireless ASK coding. Background Technique

[0002] At present, most of the train positioning devices in the rail transit industry adopt technical specifications based on the European transponder transmission system. Its working principle is that the trackside transponder device obtains activation energy through the 27M single-frequency radio frequency signal sent by the train, and sends an FSK signal with a center frequency of 4.234M to the train. Based on the energy change of this signal, the position of the center point of the transponder is calculated. The wireless positioning unit converts the center point information into the corresponding mileage information through the center point information, speed information, and clock information sent by the vehicle-mounted host and sends it to the vehicle-mounted unit.

[0003] The above method of obtaining the center point information, speed information, and clock information, and converting the above information into the corresponding mileage information and sending it to the vehicle-mounted unit has a low conversion efficiency and low accuracy of the obtained mileage information.

[0004] Therefore, based on the above problems, another method for train positioning based on 900M frequency antenna interaction is provided. The difference between this method and other train positioning methods is that the signal frequency involved in positioning is 900M, the modulation and demodulation method of its vehicle-ground interaction data is ASK, and there is also coding code distance and check protection at the communication layer. On this basis, the position of the 900M beacon center point is judged according to the accurate area of the application data of the received data, and the relevant data of the 900M beacon is read out without obtaining the vehicle-mounted mileage information, speed information, and clock information. It is a safe, reliable, high-efficiency, and high-precision positioning method. Summary of the Invention

[0005] The purpose of the present invention is to provide an urban rail signal system train positioning method based on 900M frequency wireless ASK coding. The devices required for this method include 900M radio frequency devices, RFID devices, and 900M demodulation devices. The steps of this method include:

[0006] Step 1: Send a single-frequency signal through a 900M radio frequency device. The RFID device receives this 900M signal and sends the modulated wireless signal to the 900M demodulation device. The 900M demodulation device performs ASK demodulation to obtain the most original digital baseband signal, and the frequency of the digital baseband signal is 40kbps.

[0007] Step 2: After obtaining the original encoded data, decode the original encoded data. When decoding, it is the original 0 signal, and For the original 1 signal, the original signal frame of 00000011 is used as the header data, and the subsequent 60-bit application data is encoded in sequence. Among them, the four original code-bit signals of 0011 are represented as logical 1, and the four original code-bit signals of 1100 are represented as logical 0. In this way, there is a certain code distance between logical 1 and logical 0. If it is not these two encoding information, it is considered that there is an error in the received wireless channel, and the whole packet of data is discarded and the search for the header data starts again.

[0008] Step 3: Check whether a complete frame of data is received. If it is incomplete data, the whole packet of data is discarded. After obtaining 60 logical bit data in the original encoded data, accumulate the number of logical 1s in the frame data, and then perform a modulo operation on the value 4. The obtained remainder is compared with the last 61st and 62nd logical bits of the frame data in two bits. If the comparison is correct, a complete frame of data is received; if the comparison is incorrect, the whole packet of data is discarded.

[0009] Step 4: After receiving a correct data frame, the antenna device sets a specific IO to high level. Since it takes 6.5 ms to receive a complete frame of data, if no correct data frame is received within 10 ms, the antenna device sets the specific IO to low level. When the antenna device enters the radio frequency field, when the IO is at high level, it is considered to enter the effective radio frequency field of the 900M beacon; when the IO becomes low level, it is considered to leave the effective radio frequency field of the 900M beacon. The vehicle-mounted device calculates the center point of the output high level of the specific IO according to its own clock, and then considers it as the center point of the 900M radio frequency device. The vehicle-mounted device thus calculates the center point position of the magnetic field area of the 900M radio frequency device for train positioning.

[0010] Compared with the prior art, the beneficial effects of the present invention are as follows: The judgment of the center point position of the 900M beacon in the present invention not only depends on the hardware radio frequency ASK demodulation circuit, but also judges the original encoding during the reception process. There is a certain code distance between logical code bit 1 and logical code bit 0, and then a complete and valid message data is obtained through the judgment of the data frame check code. The magnetic field action range is judged based on the correct reception message time, and high-precision center point judgment is achieved through multiple measures such as hardware, encoding logic, check logic, and center point time calculation. Brief Description of the Drawings

[0011] Figure 1 is a schematic diagram of the device connection structure of the present invention;

[0012] Figure 2 is a schematic diagram of the digital baseband signal of the present invention;

[0013] Figure 3 is a schematic diagram of the judgment of high level and low level of the present invention. Detailed Embodiment

[0014] Next, in combination with the accompanying drawings in the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

[0015] A train positioning method for an urban rail signal system based on 900M frequency wireless ASK coding provided by the present invention. The devices required for this method include 900M radio frequency devices, RFID devices, and 900M demodulation devices. The steps of this method are as follows:

[0016] Step 1: As shown in the attached Figure 1 figure, a single-frequency signal is sent through a 900M radio frequency device. The RFID device receives this 900M signal and sends the modulated wireless signal to the 900M demodulation device. The 900M demodulation device performs ASK demodulation to obtain the most original digital baseband signal, and the frequency of the digital baseband signal is 40 kbps.

[0017] Step 2: As shown in the attached Figure 2 figure, after obtaining the original encoded data, the original encoded data is decoded. When decoding, is the original 0 signal, and is the original 1 signal. The original signal frame of 00000011 is used as the header data, and the subsequent 60-bit application data is encoded in sequence. Among them, the four original code bit signals of 0011 represent logic 1, and the four original code bit signals of 1100 represent logic 0. In this way, there is a certain code distance between logic 1 and logic 0. If it is not these two encoding information, it is considered that there is an error in the received wireless channel, and the entire packet of data is discarded and the search for the header data starts again.

[0018] Step 3: Check whether a complete frame of data is received. If it is incomplete data, the entire packet of data is discarded. After obtaining 60 logical bit data in the original encoded data, the number of logical 1s in the frame data is accumulated, and then a modulo operation is performed on the value 4. The obtained remainder is compared with the last 61st and 62nd logical bits of the frame data in two bits. If the comparison is correct, a complete frame of data is received; if the comparison is incorrect, the entire packet of data is discarded.

[0019] Step 4: As shown in the attached Figure 3As shown, after receiving a correct data frame, the antenna device sets a specific IO to high level. Since it takes 6.5 ms to receive a complete frame of data, if no correct data frame is received within 10 ms, the antenna device sets the specific IO to low level. When the antenna device enters the radio frequency field, when the IO is at high level, it is considered to have entered the effective radio frequency field of the 900M beacon, and when the IO becomes low level, it is considered to have left the effective radio frequency field of the 900M beacon. The vehicle-mounted device calculates the center point of the output high level of the specific IO based on its own clock, which is considered the center point of the 900M radio frequency device. The vehicle-mounted device then calculates the center point position of the magnetic field area of the 900M radio frequency device for train positioning.

[0020] Embodiment 1:

[0021] is the original encoded data "0" signal, and is the original encoded data "1" signal.

[0022] The original "00000011, 0011, 0011, 0011, 0011, 0011, 0011, 0011, 0011, 0011, 0011, 0011, 0011, 0011, 0011, 0011, 0011, 0011, 0011, 0011, 0011, 0011, 0011, 0011, 0011, 0011, 0011, 1100, 1100, 1100, 1100, 1100, 1100, 1100, 1100, 1100, 1100, 1100, 1100, 1100, 1100, 1100, 1100, 1100, 1100, 1100, 1100, 1100, 1100, 1100, 1100, 1100, 1100, 0011, 0011" is obtained

[0023] After verifying that the packet header is correct, decoding is performed. Among them, the original data 0011 is the logical bit 1, and the original data 1100 is the logical bit "0". So the obtained data block is:

[0024] "1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0"

[0025] It can be seen that among the 60 logical bit data, there are 30 logical 1s and 30 logical 0s. According to the checksum algorithm, taking the modulo operation with a value of 4 for the 30 logical 1s, the obtained checksum is "2", that is, "1,0".

[0026] When the antenna receives a correct message, it is considered that the current field strength is strong enough, and it can be considered that the train has entered the effective beacon magnetic field area. The antenna device will set a specific IO level high. Subsequently, a correct message will be received every 6.5 ms. Therefore, the high level of the IO will be maintained continuously. When no correct message is received for more than 10 ms, it indicates that the current field strength is not sufficient to receive a correct message, and it is considered that the train has left the effective beacon magnetic field area. The antenna device will set the specific IO level low, and the center point of the 900M beacon magnetic field area can be determined by calculating the center point of this pulse width.

[0027] Using the technical solution described in the present invention, or a person skilled in the art designing a similar technical solution inspired by the technical solution of the present invention and achieving the above technical effects shall fall within the protection scope of the present invention.

Claims

1. A train positioning method for an urban rail signal system based on 900M frequency wireless ASK coding, characterized in that: The devices required for this method include 900M radio frequency equipment, RFID equipment and 900M demodulation equipment. The steps of this method include: Step 1: Send a single-frequency signal through a 900M radio frequency device. The RFID device receives the 900M signal and sends the modulated wireless signal to a 900M demodulation device, which performs ASK demodulation to obtain the original digital baseband signal. Step 2: After obtaining the original coded data, decode the original coded data; Step 3: Check whether a complete frame of data is received. If it is incomplete, discard the entire packet of data; Step 4: After receiving a correct data frame, the antenna device sets the specific IO to a high level. If the correct data frame is not received, the antenna device sets the specific IO to a low level. When the antenna device enters the RF field, when the IO is high, it is considered to have entered the RF field where the 900M beacon is valid. When the IO becomes low, it is considered to have left the RF field where the 900M beacon is valid. The on-board device calculates the center point of the output high level of the specific IO based on its own clock, and it is considered to be the center point of the 900M RF device. The on-board device thus calculates the center point of the magnetic field area of ​​the 900M RF device for train positioning.

2. According to claim 1, a method for locating a train in an urban rail signal system based on 900M frequency wireless ASK coding, characterized in that: The frequency of the digital baseband signal in step 1 is 40 kbps.

3. The train positioning method of an urban rail signal system based on 900M frequency wireless ASK coding according to claim 1 is characterized in that: When decoding in step 2 is the original 0 signal, and The original 1 signal is used, and the original signal frame of 00000011 is used as the packet header data. The subsequent 60 bits of application data are encoded in sequence, where the four original code bit signals of 0011 represent logic 1, and the four original code bit signals of 1100 represent logic 0. In this way, there is a certain code distance between logic 1 and logic 0. If it is not these two types of encoded information, it is considered that there is a bit error in the receiving wireless channel, and the entire packet data is discarded and the search for the packet header data begins again.

4. The train positioning method of an urban rail signal system based on 900M frequency wireless ASK coding according to claim 1 is characterized in that: After obtaining the 60 logical bits of data in the original encoded data in the step three, the number of logical 1s in the frame data is accumulated, and then the value 4 is modulo operation is performed, and the remainder obtained is compared with the last 61 and 62 logical bits of the frame data by two bits. If the comparison is correct, a complete frame of data is received. If the comparison is wrong, the entire packet of data is discarded.

5. The train positioning method of the urban rail signal system based on 900M frequency wireless ASK coding according to claim 1 is characterized in that: The judgment of the high level and the low level in the step 4 is determined by whether the correct data frame is received within 10ms. If the correct data frame is received within 10ms, it is set to a high level. If the correct data frame is not received within 10ms, it is set to a low level.

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