Passive digital tag system based on Beidou and radio frequency identification technology

Abstract

The invention provides a passive digital tag system based on Beidou and radio frequency identification technology, which comprises a radio frequency electronic tag, an RFID reader-writer module, a GPRS communication module, an embedded processor and a background server, node information is written in the radio frequency electronic tag in advance, underground pipe gallery information is stored in the radio frequency electronic tag through a built-in chip of the radio frequency electronic tag, and the embedded processor is connected with the background server. Forming an information storage database; a GPS-RTK differential positioning algorithm is operated in the Beidou positioning module, real-time dynamic positioning of the radio frequency electronic tags is realized, coordinate information of the radio frequency electronic tags is stored in a database, and an underground pipe gallery trend electronic map is established; a GIS map system is installed in the background server. The defects that a traditional label can only be identified through visible information, manual reading is achieved, and the amount of information is small can be overcome; the problems of sparse distribution, easy loss and displacement in a traditional identification mode are solved; the problem that a traditional identification method is inaccurate in buried underground pipe cable trend positioning and cannot synchronously record underground pipe cable information updating is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of underground pipeline operation and maintenance management, and in particular to a passive digital tag system based on Beidou and radio frequency identification technologies. Background Art

[0002] In recent years, in order to meet the requirements of urban construction and environmental beautification, more and more pipelines are built in underground corridors. The proportion of underground integrated corridors in energy transmission and distribution systems is increasing, and the scale is growing rapidly. However, they are often damaged by external forces during service, and hidden faults occur frequently. Moreover, the type, location, and time are difficult to predict, which seriously affects the safety and reliability of underground corridors. Therefore, protecting underground pipelines from external damage has become an urgent problem to be solved. However, the current pipeline channel path indication mostly relies on electronic piles and traditional plastic hanging tags erected on the surface for identification. They have problems such as sparse distribution, displacement, easy blur, and easy loss. It is difficult to accurately describe the real-time location of the pipeline, thereby ensuring the safety of the line. It does not have the function of storing equipment operation and maintenance information, which is contrary to the development direction of intelligent energy transportation. Traditional operation and maintenance technology cannot effectively match the growth rate of energy infrastructure, resulting in huge pressure on pipeline channel operation and maintenance work. At the same time, the ancillary equipment of underground pipelines (such as underground pipe and cable distribution boxes, ring network cabinets, etc.) are at risk of being stolen. Therefore, it is of great significance to develop a digital tag to locate the location of underground pipelines and their ancillary equipment in real time and store and read information. Domestic and foreign research institutions and enterprises have also conducted research in this area, but they still have the following shortcomings:

[0003] 1. The main problems of the radio method are that it can only identify a single material, cannot identify and analyze multiple underground cables at the same time, has a low fault tolerance rate, has strong background signal interference, and the signal cannot penetrate highly conductive materials.

[0004] 2. The principle of ground penetrating radar technology is to use an antenna to emit high-frequency pulse electromagnetic waves to the detection target. The pulse generates an echo on the interface. By analyzing the radar waveform, the location and depth of the underground cable failure can be analyzed. However, this method cannot distinguish the overlap of multiple underground cables at the same depth, and the equipment cost is high, and the professional skills of the technicians are high. Using only ground penetrating radar technology is not enough to achieve the research goal of effectively identifying the path of underground cables. Summary of the invention

[0005] The purpose of the present invention is to provide a passive digital tag system based on Beidou and radio frequency identification technology, which mainly solves the following problems: solves the defects that traditional tags can only be identified by visible information, manually read and have a small amount of information; solves the problems of sparse distribution, easy loss and displacement in traditional identification methods; solves the problems that traditional identification methods cannot accurately locate the direction of buried underground cables and cannot synchronously record the update of underground cable information.

[0006] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0007] A passive digital tag system based on Beidou and radio frequency identification technology, comprising:

[0008] Radio frequency electronic tags are installed in monitored nodes. Node information is pre-written in the radio frequency electronic tags. Radio frequency electronic tags store underground corridor locations, underground corridor operation information and other information through their built-in chips to form underground corridor information storage databases.

[0009] RFID reader / writer module, used to transmit and receive radio frequency signals corresponding to radio frequency electronic tags, so as to realize the collection and modification of radio frequency electronic tag information;

[0010] Beidou positioning module, in which the GPS-RTK differential positioning algorithm is run, to achieve real-time dynamic positioning of the radio frequency electronic tag, and to store the coordinate information of the radio frequency electronic tag in the database to establish an electronic map of the underground pipeline corridor;

[0011] GPRS communication module, which realizes real-time data communication between multiple electronic tags and between electronic tags and the background server through the MQTT protocol;

[0012] Embedded processor: The embedded processor obtains the location information of the radio frequency electronic tag through the Beidou positioning module or the GPRS communication module, and reports it to the data receiving and processing system through the communication module. The data receiving and processing system receives the location information and device information reported by the monitored node, and processes and displays the data;

[0013] A power management module, used to provide power for the entire passive digital tag system;

[0014] The backend server has a GIS map system installed in it. The coordinate information of the RFID tag is marked on the GIS map system. The GIS map system in the backend server and the underground pipe gallery information storage database can be remotely accessed by scanning the RFID tag.

[0015] According to a passive digital tag system based on Beidou and radio frequency identification technology provided by the present invention, the Beidou positioning module includes a GNSS module, an RTK differential positioning unit, a positioning antenna, a DTU-4G data transparent transmission module, a 4G antenna, and an RS232 / TTL protocol conversion module. The positioning antenna is used to receive satellite signals and transmit them to the GNSS module. After receiving the satellite signals, the GNSS module parses and obtains GNSS positioning information, speed information and heading information in real time, and sends them to the RTK differential positioning unit through a high-speed serial port and Ethernet in a redundant backup transmission mode; the RTK differential positioning unit is connected to an embedded processor, and the embedded processor is connected to the DTU-4G data transparent transmission module through the RS232 / TTL protocol conversion module, and transmits the coordinate information to a background server through the 4G antenna.

[0016] According to a passive digital tag system based on Beidou and radio frequency identification technology provided by the present invention, the following is performed in an RTK differential positioning unit:

[0017] The base station with known coordinates sends the carrier phase observation value, its own position, observation error factor and other data to the background server through the 4G network. At the same time, the mobile station obtains the error factor from the background server in real time through the DTU-4G data transmission module. The mobile station uses the received observation data and real-time error value of the base station and the GNSS observation value collected by itself to perform differential calculation to correct the carrier phase in real time, thereby obtaining the centimeter-level positioning accuracy value of the mobile station.

[0018] According to a passive digital tag system based on Beidou and radio frequency identification technology provided by the present invention, the phase difference value between satellite stations includes: the initial integer ambiguity, the integer change value from the starting time to the observation time, and the decimal part of the observed phase. The distance between satellite stations is the product of the carrier wavelength and the phase difference between the satellite stations. The real distance between the satellite stations and the pseudo-range observation value between the satellite stations can be obtained at the reference station using the known coordinates and satellite ephemeris, and the pseudo-range correction number is calculated, and the pseudo-range observation value of the user station is modified by the correction number.

[0019] According to a passive digital tag system based on Beidou and radio frequency identification technology provided by the present invention, if satellite tracking does not lose lock during the observation process, the difference in the number of initial integer cycles is a constant, and the difference in the clock errors of the two receivers, the difference in noise, and the difference in the multipath effect between the two stations between adjacent epochs are all less than the allowable error of cm-level dynamic positioning, and the carrier phase measurement difference can also be regarded as a constant during the solution process;

[0020] Therefore, once the starting integer number is determined, the mobile station can be positioned by observing the same four satellites at the base station and the mobile station at the same time, wherein the integer number is calculated by the correlation ambiguity algorithm.

[0021] According to a passive digital tag system based on Beidou and radio frequency identification technology provided by the present invention, when using an RFID reader / writer module, the propagation time of a signal emitted by the RFID reader to reach the radio frequency electronic tag and then return to the RFID reader is obtained, and the distance from the radio frequency electronic tag to the RFID reader is obtained from the propagation time, wherein at least three RFID readers are required to realize the positioning of the radio frequency electronic tag, and the distances measured by the three RFID readers to the radio frequency electronic tag are r1, r2, and r3 respectively. Three circles are drawn with each RFID reader as the center and the measured distance as the radius, and the intersection point is the electronic tag position, and the radio frequency electronic tag position information is estimated using a least squares algorithm.

[0022] According to a passive digital tag system based on Beidou and radio frequency identification technology provided by the present invention, when using Beidou positioning module and GPRS communication module to locate radio frequency electronic tags, it includes:

[0023] Configure the serial ports of related modules, configure the timer, interrupt the serial port configuration, and determine whether the serial port configuration of the first Beidou positioning module is interrupted. If so, send and receive data;

[0024] If not, determine whether the serial port configuration of the second Beidou positioning module is interrupted. If so, locate the data and obtain the UTC time, and refresh the screen;

[0025] If the serial port configuration of the second Beidou positioning module has not been interrupted, it is determined whether the serial port configuration of the GPRS communication module is interrupted. If so, data is sent and received, and a heartbeat signal is sent to the outside.

[0026] If the serial port configuration of the GPRS communication module has not been interrupted, then determine whether the first timing time has been reached, if so, then determine whether the heartbeat counter is greater than 5, if so, then disconnect and reconnect;

[0027] If the second timing time is reached, the information of the radio frequency electronic tag is read and the read information is uploaded to the background server.

[0028] According to a passive digital tag system based on Beidou and radio frequency identification technology provided by the present invention, the background server uses a B / S architecture, its port is open to the public network, a TCP / IP protocol server is created, and NIO technology is used to improve the concurrency performance of the software. The background server website can be accessed through a browser to see the location of the node; after receiving the information, the received node ID and longitude and latitude information are saved in the underground corridor information database after error checking and conversion.

[0029] According to a passive digital tag system based on Beidou and radio frequency identification technology provided by the present invention, the RFID reader-writer module includes an RFID reader, and the RFID reader includes an RFID transmitting circuit, an RFID receiving circuit and an RFID power supply circuit. The RFID transmitting circuit receives a driving signal sent by an embedded processor, drives a push-pull circuit after being shaped by a logic circuit, and sends a radio signal outward through an antenna. The RFID receiving circuit amplifies the received signal through a receiving circuit and a differential amplifier circuit, and then transmits the signal to the embedded processor for processing after amplifying the signal through an operational amplifier. The RFID power supply circuit mainly increases the 5V voltage to a voltage of positive and negative 24V through a transformer, and drives the MOS tube of the RFID transmitting circuit to transmit a radio signal.

[0030] According to a passive digital tag system based on Beidou and radio frequency identification technology provided by the present invention, when positioning a mobile station, based on the known coordinates of the reference station and the three-point circle determination principle, according to the effective measurement results of multi-point static relative positioning of the mobile station satellite navigation receiver on a preset circular trajectory, a parameter description of the absolute position of the circular trajectory is obtained;

[0031] The satellite navigation receiver of the mobile station moves along a circular trajectory at a preset speed, and the ephemeris file and the observation data file are obtained by parsing the received signal of the satellite navigation receiver of the mobile station. After the gross error and cycle slip inspection, the usable observation data are obtained;

[0032] Taking the inter-station and inter-satellite carrier phase double difference ambiguity and the sine and cosine values ​​of the yaw angle of the mobile station relative to the center of the trajectory as unknowns, according to the circular motion trajectory constraints, the inter-station and inter-satellite pseudo-range double difference equations and the inter-station and inter-satellite carrier phase double difference equations between the mobile station and the reference station are established, and the floating-point ambiguity and floating-point positioning solutions are obtained by solving them.

[0033] The floating point ambiguity is fixed to obtain an integer solution of the ambiguity, and a carrier phase double difference equation about the relative position vector from the reference station to the mobile station is established according to the integer solution of the ambiguity;

[0034] The accurate position data of the mobile station is calculated based on the effective fixed solution and circular trajectory obtained from the carrier phase double difference equation. The measurement error of the mobile station satellite navigation receiver is calculated based on the observation data of the mobile station, the corresponding accurate position data and the satellite position at the corresponding time.

[0035] It can be seen that compared with the prior art, the present invention is a passive digital tag system based on Beidou navigation technology with the function of precise positioning and identification of buried underground cables and pipes. It uses solar power supply or electric pile power to realize long-term operation of the tag, and is equipped with a wireless electronic tag reading device system to establish a virtual digital model of the underground cable line. It can realize the information and digital management and control of underground cables and form a visualization system platform, so that it has all-day, real-time supervision and monitoring capabilities, and can quickly and accurately determine the path of underground cables and pipes. At the same time, it can also reduce the technical requirements for manual path identification and improve the timeliness of anti-external force damage. It has the advantages of large transmission range, non-line-of-sight, high precision, low system cost, etc., and has extremely high practicality, feasibility, and scalability.

[0036] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic diagram of an embodiment of a passive digital tag system based on Beidou and radio frequency identification technology of the present invention.

[0038] Figure 2 It is a schematic diagram of an RFID reader-writer module in an embodiment of a passive digital tag system based on Beidou and radio frequency identification technology of the present invention.

[0039] Figure 3 It is a flow diagram of a GPS-RTK differential positioning algorithm in an embodiment of a passive digital tag system based on Beidou and radio frequency identification technology of the present invention.

[0040] Figure 4 It is a flow diagram of the interruption and precise timing of rapid response during data reporting in an embodiment of a passive digital tag system based on Beidou and radio frequency identification technology of the present invention. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] This embodiment is a passive digital tag system based on Beidou + radio frequency identification technology (RFID). By installing digital tags on important nodes of underground pipelines, the long-term operation of the tags is achieved by using solar power supply or electric charging piles. In combination with Beidou coordinate positioning technology, outdoor positioning is achieved. GPS-RTK differential positioning technology is used, combined with the measured buried depth of the pipeline corridor during installation (the approximate depth is 0.7M to 1M), to obtain the three-dimensional coordinate information of important nodes of the underground pipeline corridor, and establish a virtual electronic map showing the direction of the underground pipeline corridor line.

[0043] The underground pipes and cables of this embodiment can be electrical cables, optical fibers, communication cables, pipelines (gas pipelines, recycled water pipes and heating pipelines, etc.), including but not limited to underground pipelines such as electricity, communications, radio and television, water supply, drainage, heat, and gas.

[0044] like Figure 1 As shown, the present invention provides a passive digital tag system based on Beidou and radio frequency identification technology, including:

[0045] Radio frequency electronic tags are installed in monitored nodes. Node information is pre-written in the radio frequency electronic tags. Radio frequency electronic tags store underground corridor locations, underground corridor operation information and other information through their built-in chips to form underground corridor information storage databases.

[0046] RFID reader / writer module, used to transmit and receive radio frequency signals corresponding to radio frequency electronic tags, so as to realize the collection and modification of radio frequency electronic tag information;

[0047] Beidou positioning module, in which the GPS-RTK differential positioning algorithm is run, to achieve real-time dynamic positioning of the radio frequency electronic tag, and to store the coordinate information of the radio frequency electronic tag in the database to establish an electronic map of the underground pipeline corridor;

[0048] The GPRS communication module uses the MQTT protocol to achieve real-time data communication between multiple electronic tags and between electronic tags and the backend server, while ensuring that data can be transmitted stably;

[0049] Embedded processor: The embedded processor obtains the location information of the radio frequency electronic tag through the Beidou positioning module or the GPRS communication module, and reports it to the data receiving and processing system through the communication module. The data receiving and processing system receives the location information and device information reported by the monitored node, and processes and displays the data;

[0050] The power management module is used to provide power for the entire passive digital tag system; wherein the power module is powered by a large-capacity and high-power lithium battery.

[0051] The backend server has a GIS map system installed in it. The coordinate information of the RFID tag is marked on the GIS map system. The GIS map system in the backend server and the underground pipe gallery information storage database can be remotely accessed by scanning the RFID tag.

[0052] In this embodiment, the Beidou positioning module includes a GNSS module, an RTK differential positioning unit, a positioning antenna, a DTU-4G data transparent transmission module, a 4G antenna, and an RS232 / TTL protocol conversion module. The positioning antenna is used to receive satellite signals and transmit them to the GNSS module. After receiving the satellite signals, the GNSS module parses and obtains GNSS positioning information, speed information and heading information in real time, and sends them to the RTK differential positioning unit through the high-speed serial port and Ethernet in a redundant backup transmission mode; the RTK differential positioning unit is connected to the embedded processor, and the embedded processor is connected to the DTU-4G data transparent transmission module through the RS232 / TTL protocol conversion module, and transmits the coordinate information to the background server through the 4G antenna.

[0053] It can be seen that this system uses STM32F103RCT6 as the main control chip, obtains the coordinate information of the observation point through the Zhongke Microelectronics GNSS module and the positioning antenna, and after processing by the main control chip, it is connected to the DTU4G transparent transmission module through the RS232 / TTL protocol conversion module, and finally the coordinate information is transparently transmitted to the public network through the 4G antenna.

[0054] For the visualization, informationization and digital management and control of underground pipelines, this embodiment realizes the integration of the digital label system and the GIS geographic information system, integrating the functions of the two systems. The GIS system can display the real-time location information of underground pipes and cables obtained by the Beidou module in the form of an electronic map, and integrate it into the RFID tag information database to create digital labels for underground pipes and cables, thereby realizing the visualization, informationization and digital management and control of the location of underground pipe and cable equipment.

[0055] The algorithm part of this embodiment includes a ranging RFID positioning algorithm, a Beidou high-precision positioning-static relative positioning algorithm, and is optimized using GPS-RTK differential technology.

[0056] Since static relative positioning requires long-term static observation, the application of this method in dynamic positioning is limited. RTK real-time dynamic positioning technology is used in the Beidou positioning module. Therefore, the following is executed in the RTK differential positioning unit:

[0057] The time and space benchmarks are unified through GPS / BD multi-frequency data reception, and the base station with known coordinates sends the carrier phase observation value, its own position, observation error factor and other data to the background server through the 4G network. At the same time, the mobile station obtains the error factor from the background server in real time through the DTU-4G data transmission module. The mobile station uses the received observation data and real-time error value of the base station and the GNSS observation value collected by itself to perform differential calculation to correct the carrier phase in real time, thereby obtaining the centimeter-level positioning accuracy value of the mobile station.

[0058] The specific method is as follows: the phase difference between satellite stations includes: the initial integer ambiguity, the integer change value from the starting time to the observation time, and the fractional part of the observed phase. The distance between satellite stations is the product of the carrier wavelength and the phase difference between the satellite stations. The true distance between satellite stations and the pseudo-range observation value between satellite stations can be obtained at the reference station using known coordinates and satellite ephemeris, and the pseudo-range correction number can be calculated, and the pseudo-range observation value of the user station can be modified with this correction number.

[0059] If the satellite tracking does not lose lock during the observation process, the difference in the initial integer cycle number is a constant, and the difference in the clock errors of the two receivers, the difference in noise, and the difference in the multipath effect between the two stations between adjacent epochs are all less than the allowable error of cm-level dynamic positioning. In the solution process, the carrier phase measurement difference can also be regarded as a constant;

[0060] Therefore, once the starting integer number is determined, the mobile station can be positioned by observing the same four satellites at the base station and the mobile station at the same time, wherein the integer number is calculated by the correlation ambiguity algorithm.

[0061] It can be seen that the RTK differential positioning algorithm takes a short time and can provide the coordinates of the observation points in real time, effectively improving the accuracy of underground cable identification. Its flow chart is as follows: Figure 3 As shown:

[0062] The TOA positioning algorithm of this embodiment is based on the TOA circle equation. Different positioning equations are constructed through different combinations of intersection lines between circles. When using the RFID reader / writer module, the propagation time of the signal emitted by the RFID reader to the radio frequency electronic tag and then returning to the RFID reader is obtained, and the distance from the radio frequency electronic tag to the RFID reader is obtained from the propagation time. Among them, at least three RFID readers are required to realize the positioning of the radio frequency electronic tag. The distances measured by the three RFID readers to the radio frequency electronic tag are r1, r2, and r3 respectively. Three circles are drawn with each RFID reader as the center and the measured distance as the radius. The intersection point is the electronic tag position, and the least squares (LS) algorithm is used to estimate the radio frequency electronic tag position information.

[0063] When the location information and its own device identification collected by the digital tag system are uploaded to the server through GPRS and Beidou, the server (computer) will process the received information comprehensively. The server program adopts the MVC design mode, the program runs stably, and provides an extensible interface for other users.

[0064] The data reporting software design makes full use of the embedded CPU and USART communication interface, fast response interrupts and accurate timers. Figure 4 As shown in the figure, when using Beidou positioning module and GPRS communication module for radio frequency electronic tag positioning, it includes:

[0065] Configure the serial ports of related modules, configure the timer, interrupt the serial port configuration, and determine whether the serial port configuration of the first Beidou positioning module is interrupted. If so, send and receive data;

[0066] If not, determine whether the serial port configuration of the second Beidou positioning module is interrupted. If so, locate the data and obtain the UTC time, and refresh the screen;

[0067] If the serial port configuration of the second Beidou positioning module has not been interrupted, it is determined whether the serial port configuration of the GPRS communication module is interrupted. If so, data is sent and received, and a heartbeat signal is sent to the outside.

[0068] If the serial port configuration of the GPRS communication module has not been interrupted, then determine whether the first timing time has been reached, if so, then determine whether the heartbeat counter is greater than 5, if so, then disconnect and reconnect;

[0069] If the second timing time is reached, the information of the radio frequency electronic tag is read and the read information is uploaded to the background server.

[0070] In this embodiment, the background server uses a B / S architecture, its port is open to the public network, a TCP / IP protocol server is created, and NIO technology is used to improve the concurrent performance of the software. The background server URL can be accessed through a browser to see the location of the node; after receiving the information, the received node ID and longitude and latitude information are saved in the underground corridor information database after error checking and conversion.

[0071] like Figure 2As shown, the RFID reader-writer module includes an RFID reader, middleware, and an application system. The RFID reader includes an RFID transmitting circuit, an RFID receiving circuit, and an RFID power supply circuit. The RFID transmitting circuit receives the driving signal sent by the embedded processor, drives the push-pull circuit after being shaped by the logic circuit, and sends a radio signal outward through the antenna. The RFID receiving circuit amplifies the received signal through the receiving circuit and the differential amplifier circuit, and then amplifies the signal through the operational amplifier and transmits it to the embedded processor for processing. The RFID power supply circuit mainly increases the 5V voltage to a voltage of positive and negative 24V through a transformer, and drives the MOS tube of the RFID transmitting circuit to transmit a radio signal.

[0072] In this embodiment, static relative positioning generally uses carrier phase observation values ​​as the basic observation value, and accurately measures baselines of various lengths. The steps of static relative positioning mainly include: establishing a double-difference carrier phase observation equation, adjusting the double-difference observation equation, solving the integer ambiguity floating-point solution using the least squares method, fixing the integer ambiguity using the LAMBDA algorithm, solving the baseline and completing the positioning calculation.

[0073] Specifically, when positioning the mobile station, based on the known coordinates of the reference station and the three-point circle determination principle, the parameter description of the absolute position of the circular trajectory is obtained according to the effective measurement results of the multi-point static relative positioning of the mobile station satellite navigation receiver on the preset circular trajectory;

[0074] The satellite navigation receiver of the mobile station moves along a circular trajectory at a preset speed, and the ephemeris file and the observation data file are obtained by parsing the received signal of the satellite navigation receiver of the mobile station. After the gross error and cycle slip inspection, the usable observation data are obtained;

[0075] Taking the inter-station and inter-satellite carrier phase double difference ambiguity and the sine and cosine values ​​of the yaw angle of the mobile station relative to the center of the trajectory as unknowns, according to the circular motion trajectory constraints, the inter-station and inter-satellite pseudo-range double difference equations and the inter-station and inter-satellite carrier phase double difference equations between the mobile station and the reference station are established, and the floating-point ambiguity and floating-point positioning solutions are obtained by solving them.

[0076] The floating point ambiguity is fixed to obtain an integer solution of the ambiguity, and a carrier phase double difference equation about the relative position vector from the reference station to the mobile station is established according to the integer solution of the ambiguity;

[0077] According to the effective fixed solution and circular trajectory obtained by the carrier phase double difference equation, the accurate position data of the mobile station is calculated, and the measurement error of the satellite navigation receiver of the mobile station is calculated according to the observation data of the mobile station, the corresponding accurate position data and the satellite position at the corresponding time. It can be seen that this embodiment improves the success rate and accuracy of solving the ambiguity floating point solution through the above algorithm, optimizes the floating point solution covariance matrix to make it easier to be correctly fixed; the circular motion trajectory constraint allows the positioning error to be measured, and the moment when a part of the effective fixed solution is missing can be calculated by the interpolation method, so that the error measurement result is more comprehensive and reliable.

[0078] To sum up, this embodiment is a passive digital tag system with the function of accurate positioning and identification of buried underground cables based on Beidou navigation technology. It uses solar power supply or electric pile power to realize long-term operation of the tag, configures a wireless electronic tag reading device system, and establishes a virtual digital model of the underground cable line. It can realize the information and digital management and control of underground cables, and form a visualization system platform, so that it has all-day, real-time supervision and monitoring capabilities, can quickly and accurately determine the path of underground cables, and at the same time can reduce the technical requirements for manual path identification and improve the timeliness of anti-external force damage. It has the advantages of large transmission range, non-line-of-sight, high precision, low system cost, etc., and has extremely high practicality, feasibility, and scalability.

[0079] Furthermore, an intelligent location service terminal is used to integrate the RFID electronic tag and the Beidou positioning module, and the GPS-RTK carrier phase differential positioning technology is used for solution. The carrier phase is corrected in real time to obtain centimeter-level positioning accuracy. Beidou high-precision positioning - static relative positioning technology is used to improve the accuracy of the integer ambiguity solution, while eliminating the influence of observation noise, realizing the integration of indoor positioning and outdoor positioning, and realizing the precise positioning of the tag position.

[0080] Furthermore, the entire application system is constructed through middleware and application software. At the same time, the application system can provide a business logic processing interface for the digital tag, and realize the interaction between man-machine or system and the digital tag according to the device information read by the reader.

[0081] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0082] The above-mentioned embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by technicians in this field on the basis of the present invention shall fall within the scope of protection required by the present invention.

Claims

1. A passive digital tag system based on Beidou and radio frequency identification technology, characterized in that: include: Radio frequency electronic tags are installed in monitored nodes. Node information is pre-written in the radio frequency electronic tags. Radio frequency electronic tags store underground corridor locations, underground corridor operation information and other information through their built-in chips to form underground corridor information storage databases. RFID reader / writer module, used to transmit and receive radio frequency signals corresponding to radio frequency electronic tags, so as to realize the collection and modification of radio frequency electronic tag information; Beidou positioning module, in which the GPS-RTK differential positioning algorithm is run, to achieve real-time dynamic positioning of the radio frequency electronic tag, and to store the coordinate information of the radio frequency electronic tag in the database to establish an electronic map of the underground pipeline corridor; GPRS communication module, which realizes real-time data communication between multiple electronic tags and between electronic tags and the backend server through the MQTT protocol; Embedded processor: The embedded processor obtains the location information of the radio frequency electronic tag through the Beidou positioning module or the GPRS communication module, and reports it to the data receiving and processing system through the communication module. The data receiving and processing system receives the location information and device information reported by the monitored node, and processes and displays the data; A power management module, used to provide power for the entire passive digital tag system; The backend server has a GIS map system installed in it. The coordinate information of the RFID tag is marked on the GIS map system. The GIS map system in the backend server and the underground pipe gallery information storage database can be remotely accessed by scanning the RFID tag.

2. The method according to claim 1, characterized in that: The Beidou positioning module includes a GNSS module, an RTK differential positioning unit, a positioning antenna, a DTU-4G data transparent transmission module, a 4G antenna, and an RS232 / TTL protocol conversion module. The positioning antenna is used to receive satellite signals and transmit them to the GNSS module. After receiving the satellite signals, the GNSS module parses and obtains GNSS positioning information, speed information, and heading information in real time, and sends them to the RTK differential positioning unit via a high-speed serial port and Ethernet in a redundant backup transmission mode; the RTK differential positioning unit is connected to the embedded processor, and the embedded processor is connected to the DTU-4G data transparent transmission module via the RS232 / TTL protocol conversion module, and transmits the coordinate information to the background server via the 4G antenna.

3. The method according to claim 2, characterized in that: Execute in the RTK differential positioning unit: The base station with known coordinates sends the carrier phase observation value, its own position, observation error factor and other data to the background server through the 4G network. At the same time, the mobile station obtains the error factor from the background server in real time through the DTU-4G data transmission module. The mobile station uses the received observation data and real-time error value of the base station and the GNSS observation value collected by itself to perform differential calculation to correct the carrier phase in real time, thereby obtaining the centimeter-level positioning accuracy value of the mobile station.

4. The method according to claim 3, characterized in that: The phase difference between satellite stations includes: the initial integer ambiguity, the integer change value from the starting time to the observation time, and the fractional part of the observed phase. The distance between satellite stations is the product of the carrier wavelength and the phase difference between the satellite stations. The true distance between satellite stations and the pseudorange observation value between satellite stations can be obtained at the reference station using known coordinates and satellite ephemeris, and the pseudorange correction number can be calculated, and the pseudorange observation value of the user station can be modified with this correction number.

5. The method according to claim 4, characterized in that: If the satellite tracking does not lose lock during the observation process, the difference in the initial integer cycle number is a constant, and the difference in the clock errors of the two receivers, the difference in noise, and the difference in the multipath effect between the two stations between adjacent epochs are all less than the allowable error of cm-level dynamic positioning. In the solution process, the carrier phase measurement difference can also be regarded as a constant; Therefore, once the starting integer number is determined, the mobile station can be positioned by observing the same four satellites at the base station and the mobile station at the same time, wherein the integer number is calculated by the correlation ambiguity algorithm.

6. The method according to claim 1, characterized in that: When using the RFID reader / writer module, the propagation time of the signal emitted by the RFID reader to the radio frequency electronic tag and then back to the RFID reader is obtained, and the distance from the radio frequency electronic tag to the RFID reader is obtained from the propagation time. Among them, at least three RFID readers are required to realize the positioning of the radio frequency electronic tag. The distances measured by the three RFID readers to the radio frequency electronic tag are r1, r2, and r3 respectively. Three circles are drawn with each RFID reader as the center and the measured distance as the radius. The intersection of the circles is the electronic tag position, and the least squares algorithm is used to estimate the radio frequency electronic tag position information.

7. The method according to claim 1, characterized in that: When using Beidou positioning module and GPRS communication module for radio frequency electronic tag positioning, it includes: Configure the serial ports of related modules, configure the timer, interrupt the serial port configuration, and determine whether the serial port configuration of the first Beidou positioning module is interrupted. If so, send and receive data; If not, determine whether the serial port configuration of the second Beidou positioning module is interrupted. If so, locate the data and obtain the UTC time, and refresh the screen; If the serial port configuration of the second Beidou positioning module has not been interrupted, it is determined whether the serial port configuration of the GPRS communication module is interrupted. If so, data is sent and received, and a heartbeat signal is sent to the outside. If the serial port configuration of the GPRS communication module has not been interrupted, then determine whether the first timing time has been reached, if so, then determine whether the heartbeat counter is greater than 5, if so, then disconnect and reconnect; If the second timing time is reached, the information of the radio frequency electronic tag is read and the read information is uploaded to the background server.

8. The method according to claim 1, characterized in that: The backend server uses a B / S architecture, with its port open to the public network, creates a TCP / IP protocol server, and uses NIO technology to improve the concurrent performance of the software. The backend server URL can be accessed through a browser to see the location of the node; After receiving the information, the received node ID and longitude and latitude information will be saved in the underground pipeline corridor information database after error correction and conversion.

9. The method according to claim 6, characterized in that: The RFID reader-writer module includes an RFID reader, which includes an RFID transmitting circuit, an RFID receiving circuit and an RFID power supply circuit. The RFID transmitting circuit receives the driving signal sent by the embedded processor, drives the push-pull circuit after being shaped by the logic circuit, and sends a radio signal outward through the antenna. The RFID receiving circuit amplifies the received signal through the receiving circuit and the differential amplifier circuit, and then amplifies the signal through the operational amplifier and transmits it to the embedded processor for processing. The RFID power supply circuit mainly increases the 5V voltage to a voltage of positive and negative 24V through a transformer, and drives the MOS tube of the RFID transmitting circuit to transmit a radio signal.

10. The method according to claim 5, characterized in that: When positioning the mobile station, based on the known coordinates of the reference station and the principle of three-point circle positioning, the parameter description of the absolute position of the circular trajectory is obtained according to the effective measurement results of the mobile station satellite navigation receiver's multi-point static relative positioning on the preset circular trajectory; The satellite navigation receiver of the mobile station moves along a circular trajectory at a preset speed, and the ephemeris file and the observation data file are obtained by parsing the received signal of the satellite navigation receiver of the mobile station. After the gross error and cycle slip inspection, the usable observation data are obtained; Taking the inter-station and inter-satellite carrier phase double difference ambiguity and the sine and cosine values ​​of the yaw angle of the mobile station relative to the center of the trajectory as unknowns, according to the circular motion trajectory constraints, the inter-station and inter-satellite pseudo-range double difference equations and the inter-station and inter-satellite carrier phase double difference equations between the mobile station and the reference station are established, and the floating-point ambiguity and floating-point positioning solutions are obtained by solving them. The floating point ambiguity is fixed to obtain an integer solution of the ambiguity, and a carrier phase double difference equation about the relative position vector from the reference station to the mobile station is established according to the integer solution of the ambiguity; The accurate position data of the mobile station is calculated based on the effective fixed solution and circular trajectory obtained from the carrier phase double difference equation. The measurement error of the mobile station satellite navigation receiver is calculated based on the observation data of the mobile station, the corresponding accurate position data and the satellite position at the corresponding time.

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