Mobile lightning three-dimensional positioning system and method

Abstract

The application provides a mobile lightning three-dimensional positioning system, which is composed of a vehicle-mounted ground master station, a plurality of airborne air sub-stations and a plurality of mobile air sub-stations. The vehicle-mounted ground master station and the airborne air sub-stations are provided with lightning signal collecting devices, the vehicle-mounted ground master station adopts a vehicle as a ground mobile carrier, the airborne air sub-stations and the mobile air sub-stations adopt rotary-wing unmanned aerial vehicles as air mobile carriers. The airborne air sub-stations are arranged in a staggered manner, and form a three-dimensional mobile lightning detection network of ground layer, low-altitude layer and middle-altitude layer. The arrangement form of the vehicle-mounted ground master station and the airborne air sub-stations can be changed at any time, and the system has high mobility. The airborne air sub-stations are provided with wireless signal transmitting devices, lightning signals are transmitted after being processed and modulated, the lightning signals are transmitted back to the vehicle-mounted ground master station in a wireless mode, and the vehicle-mounted ground master station solves the three-dimensional position of the lightning radiation source by using a lightning positioning algorithm.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of meteorology, atmospheric electricity and space science technology, in particular to a lightning three-dimensional positioning system and method. BACKGROUND

[0002] Lightning is one of the natural phenomena in atmospheric electromagnetic activity, and lightning disaster seriously threatens human life and property safety. Due to the great randomness of the time and space of lightning occurrence, lightning hazard is huge and disaster is rapid, which brings many difficulties to its research, prediction and prevention. Lightning positioning is of great scientific significance to the research on the charge structure, charge density distribution in thunderstorm cloud and its evolution with the development of thunderstorm process, and to the revelation of the physical mechanism of lightning occurrence and development process. There are many lightning positioning methods in the prior art, such as time difference of arrival (TDOA), which is one of the commonly used lightning positioning technologies. Generally, the time difference of arrival of four or five stations is used, and the positioning accuracy can be improved by using redundant information data fusion to solve a three-dimensional positioning estimation of lightning and then to optimize fitting.

[0003] The lightning positioning method in the prior art arranges multiple stations at a distance of several kilometers or even larger on the ground to form a lightning detection network. Although there is a certain height difference between the stations on the ground, the height difference is very small compared to the distance between the stations. The station layout of the lightning detection network can be regarded as a plane. The incident angle of the lightning radiation source far away from the station is small, and the height error in the lightning positioning result is relatively large. The detection station set on the ground receives lightning signals, and the propagation error of radio waves on complex terrain, electromagnetic noise generated by electrical equipment on the ground, etc. will affect the lightning positioning accuracy. Setting one or several stations on high-rise buildings and mountains can appropriately solve the above problems, but high-rise buildings and mountains may block the lightning radiation source and affect lightning detection. Therefore, in the research on lightning detection and positioning, the lightning detection network is generally selected in a relatively open area. Temporary iron towers are also built to set the antennas of individual stations on the towers, but the height of the tower is limited, generally 30-50m, and the construction cost and difficulty increase greatly as the height increases, so this method is not obvious. The lightning detection network in the prior art is fixed and can only passively wait for suitable lightning, and cannot adapt to changing thunderstorm weather. Therefore, it is necessary to develop a new mobile three-dimensional lightning positioning network to solve the defects in the prior art. SUMMARY

[0004] The mobile lightning three-dimensional positioning system is composed of a vehicle-mounted ground master station, a plurality of airborne air sub-stations and a plurality of mobile air sub-stations.

[0005] The technical scheme adopted by the present application is to provide a mobile lightning three-dimensional positioning system composed of a vehicle-mounted ground master station 100, a plurality of airborne air sub-stations 200 and a plurality of mobile air sub-stations 300. The vehicle-mounted ground master station 100, the airborne air sub-stations 200 and the mobile air sub-stations 300 are provided with lightning signal acquisition devices 400. The vehicle-mounted ground master station 100 uses a car as a ground mobile carrier, and the airborne air sub-stations 200 and the mobile air sub-stations 300 use a rotor unmanned aerial vehicle as an air mobile carrier.

[0006] The vehicle-mounted ground master station 100 is provided with a GNSS global satellite navigation receiving device 101, and the airborne air sub-stations 200 and the mobile air sub-stations 300 obtain GNSS global satellite navigation signals through the GNSS global satellite navigation system built in the unmanned aerial vehicle. The GNSS global satellite navigation signals are used for lightning signal timing synchronization, and the precise three-dimensional coordinates of the vehicle-mounted ground master station 100 and the airborne air sub-stations 200 are obtained through real-time dynamic carrier phase difference (RTK). The lightning signal acquisition device 400 adopts a FPGA lightning signal high-speed data acquisition system mainly composed of a FPGA logic gate circuit and an embedded ARM processor.

[0007] The vehicle-mounted ground master station 100 is provided with a GNSS global satellite navigation receiving device 101, and the airborne air sub-stations 200 and the mobile air sub-stations 300 obtain GNSS global satellite navigation signals through the GNSS global satellite navigation system built in the unmanned aerial vehicle. The GNSS global satellite navigation signals are used for lightning signal timing synchronization, and the precise three-dimensional coordinates of the vehicle-mounted ground master station 100 and the airborne air sub-stations 200 are obtained through real-time dynamic carrier phase difference (RTK). The lightning signal acquisition device 400 adopts a FPGA lightning signal high-speed data acquisition system mainly composed of a FPGA logic gate circuit and an embedded ARM processor.

[0008] The airborne aerial substations 200 are at least four, but not limited to four, and acquire positioning data and redundant data to remove ambiguities. The airborne aerial substations 200 are arranged at varying heights, forming a three-dimensional mobile lightning detection network with ground, low-altitude, and mid-altitude layers. This network can be adjusted based on the location of the lightning by varying the layout of the mobile ground master stations 100 and the airborne aerial substations 200. This network can then establish an optimal spatial triangulation relationship with the lightning location, improving lightning location accuracy.

[0009] The mobile aerial substation 300 has the same configuration as the airborne aerial substation 200, and is at least one but not limited to one, and is used to replace the working airborne aerial substation 200 to achieve continuous operation of the airborne aerial substation 200. The replaced airborne aerial substation 200 is used as a new mobile aerial substation 300 after replacing the battery.

[0010] The airborne aerial substation 200 is equipped with a wireless signal transmitting device 201. The lightning signal collected by the lightning signal collecting device 400 is processed and modulated. Each airborne aerial substation 200 transmits at a different frequency. The vehicle-mounted ground master station 100 is equipped with a wireless signal receiving device 102. The lightning signal collected by the airborne aerial substation 200 is transmitted back to the vehicle-mounted ground master station 100 via wireless means. The signal received by the wireless signal receiving device 102 is demodulated by the FSK demodulation module 103 to demodulate the signal of different frequencies and stored in the data storage device 104 of the vehicle-mounted ground master station 100.

[0011] The vehicle-mounted ground master station 100 is equipped with a data processing and computing unit 105. Through the lightning signals collected by the vehicle-mounted ground master station 100 and the lightning signals returned by the airborne aerial substation 200, the data processing and computing unit 105 uses a lightning positioning algorithm to calculate the three-dimensional position of the lightning radiation source.

[0012] The lightning signal acquisition device 400 adopts an FPGA-based lightning signal high-speed data acquisition system, which is mainly composed of an FPGA logic gate circuit and an embedded ARM processor. The FPGA logic gate circuit realizes analog-to-digital conversion control, lightning data acquisition, timestamp acquisition, pre-trigger and trigger control, peak acquisition, and output control. The FPGA logic gate circuit filters the collected signal, oversamples, calculates the signal amplitude through Hilbert transform, and extracts the trigger judgment peak value. The processed data is temporarily stored in the DDR data storage unit using DMA. After the ARM processes the data, the corresponding data is extracted from the DDR data storage unit cache and stored locally. The airborne aerial substation 200 will transmit the data back to the vehicle-mounted ground master station 100 via wireless after modulation.

[0013] The vehicle-mounted ground master station 100 is equipped with a drone cluster control system 106, which can automatically control the deployment of the airborne aerial substation 200 according to the set position, and can automatically control the mobile aerial substation 300 to replace the airborne aerial substation 200 according to the set remaining power of the drone.

[0014] The lightning signal acquisition device 400 includes a high-speed A / D conversion module 1, a GNSS signal processing unit 2, a data processing unit 3, a DDR data storage unit 4, and an ARM processing unit 5. The high-speed A / D conversion module 1 converts the analog signal output by the lightning detection sensor into a digital signal. The GNSS signal processing unit 2 outputs a high-precision clock frequency as the sampling reference clock of the high-speed A / D conversion module 1 to ensure the accuracy of the signal conversion time. The output high-precision full-second clock signal 1PPS and NMEA0183 data with time information are used in conjunction with the sampling reference clock to timestamp the collected lightning signal. The GNSS signal processing unit 2 outputs RTK coordinates, and the coordinate acquisition module timestamps the coordinates and outputs the timestamp-marked coordinates. The FPGA logic gate circuit is programmed to form the data processing unit 3 to implement analog-to-digital conversion control, lightning detection data acquisition, timestamp acquisition, coordinate calibration, pre-trigger and trigger control, peak acquisition, and output control. The FPGA logic gate circuit filters the timestamp-marked signal, oversamples it, calculates the signal amplitude using the Hilbert transform, and extracts the trigger judgment peak. The lightning signal and the timestamp-marked coordinates are combined and output. The processed data is temporarily stored in the DDR data storage unit 4 using DMA, and the ARM processing unit 5 is notified to process the data. The ARM processing unit 5 embedded operating system extracts the peak data and the corresponding time information and coordinates after receiving the notification of data collection. The lightning signal collection device 400 of the vehicle-mounted ground master station 100 extracts the corresponding data and stores it in the data storage 104. The lightning signal collection device 400 of the airborne aerial substation 200 extracts the corresponding data and stores it in the file storage unit 202, and sends it wirelessly to the vehicle-mounted ground master station 100 through the wireless signal transmitting device 201.

[0015] The present invention provides a mobile three-dimensional lightning positioning method, comprising the following steps:

[0016] S1. Deploy a lightning detection network in the lightning location area, and control the drones of the airborne substation 200 to position themselves according to the set plane position and elevation through the drone cluster control system 106 of the vehicle-mounted ground master station 100;

[0017] S2, the vehicle-mounted ground master station 100 and the airborne aerial substation 200 collect lightning signals;

[0018] S3. Setting a low-battery return-to-home threshold for the airborne aerial substation 200. When the power level of any airborne aerial substation 200 is lower than the return-to-home threshold, the airborne aerial substation 300 is activated to replace the airborne aerial substation 200.

[0019] S4. The data processing and calculation unit 105 of the vehicle-mounted ground master station 100 obtains several lightning arrival locations through spatial analysis using the time difference (TDOA) of the lightning signal arriving at each measuring station, and uses the weighted least squares method to obtain an initial solution. The obtained initial solution and the constraint variables are then used to perform a second weighted least squares estimation to finally obtain an improved position estimate.

[0020] In step S1, the vehicle-mounted ground master station 100 and the airborne aerial substation 200 are arranged to avoid mountains and high-rise buildings. The distance between the airborne aerial substations 200 is 5-10 km, the low-altitude layer height is 300-1000 m, and the middle-altitude layer height is 1000-2000 m. During a continuous lightning event, the positions of the vehicle-mounted ground master station 100 and the airborne aerial substation 200 are fixed. The vehicle-mounted ground master station 100 can move the vehicle-mounted ground master station 100 and control the airborne aerial substation 200 to change the spatial layout according to the direction of the lightning, forming an optimal spatial triangulated geometric position relationship with the lightning occurrence location, thereby improving the accuracy of the lightning positioning solution.

[0021] In step S3, the return power threshold is set to 40% to 50% of the full power of the power supply. The drone cluster control system 106 controls the mobile aerial substation 300 to fly to the drone airspace below the return power threshold, replace the airborne aerial substation 200, and replace the battery of the replaced airborne aerial substation 200 as a new mobile aerial substation 300. The airborne aerial substation 200 with the lowest voltage is replaced, and all airborne aerial substations 200 are gradually replaced. After completing a round of replacement, the mobile aerial substation 300 waits for the next drone power supply to fall below the return power threshold, and then executes the replacement of the airborne aerial substation 200.

[0022] The step S4, the time difference of arrival (TDOA) positioning, is based on the known spatial position of the master station S0 ( x 0 , y 0 ,z 0) and substation S i The spatial position of x i ,y i ,z i ), with the spatial coordinates of the lightning radiation source P ( x, y, z ) is a variable, and the electromagnetic waves radiated by the lightning radiation source reach each substation Si The time difference to the master station S0 is Δ τ i , establish the system of equations and solve it:

[0023] ,

[0024] Where: Δ τ i =( τ 0 - τ i ), c is the propagation speed of electromagnetic waves, τ 0 is the time it takes for the electromagnetic wave radiated by the lightning radiation source to reach the main station, τ i It is the time it takes for the electromagnetic wave radiated by the lightning radiation source to reach the substation. i =1,2,3…… n , n The initial solution of the equations is obtained, and the weighted least squares method is used to estimate the lightning location using the initial solution and the constraint variables.

[0025] The beneficial effects of the present invention are: based on weather forecasts and thunderstorm cloud electric field detection, the detection instrument can be transported to the area where lightning is about to occur using a ground vehicle. The drone cluster control system of the vehicle-mounted ground master station controls the drones of the airborne aerial substation to be in position according to the set plane position and elevation, and the system has strong mobility. It is possible to change the layout of the mobile vehicle-mounted ground master station and the airborne aerial substation, and adjust the spatial form between the lightning detection network and the lightning, which is conducive to the calculation of the lightning position. The system uses RTK real-time dynamic carrier phase difference to determine the station position. The station position accuracy can reach the centimeter level, greatly improving the accuracy of lightning positioning. The mobile aerial substation is used to rotate and replace the airborne aerial substation to achieve continuous operation of the airborne aerial substation. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the lightning locating system of the present invention;

[0027] Figure 2 This is a working principle diagram of the present invention;

[0028] Figure 3 This is the lightning signal collection principle diagram of the vehicle-mounted ground master station;

[0029] Figure 4 This is the schematic diagram of the lightning signal collection principle of the airborne aerial substation.

[0030] In the figure: 100-vehicle-mounted ground master station, 200-aircraft-mounted aerial substation, 300-dynamic aerial substation, 400-lightning signal acquisition device, 101-GNSS global satellite navigation receiving device, 102-wireless signal receiving device, 103-FSK demodulation module, 104-data storage device, 105-data processing and calculation unit, 106-UAV cluster control system, 201-wireless signal transmitting device, 202-file storage unit, 1-high-speed A / D conversion module, 2-GNSS signal processing unit, 3-data processing unit, 4-DDR data storage unit, 5-ARM processing unit. DETAILED DESCRIPTION

[0031] In order for those skilled in the art to better understand the present invention, Figures 1 to 4 The present invention is further described, and the contents mentioned in the embodiment are not intended to limit the present invention.

[0032] The mobile three-dimensional lightning positioning system of the present invention is composed of a vehicle-mounted ground master station 100, several airborne aerial substations 200, and several mobile aerial substations 300. The schematic diagram of the lightning positioning system of the present invention is shown in FIG. Figure 1 , Figure 1 The number of four airborne substations 200 is for illustrative purposes only. The vehicle-mounted ground master station 100, airborne substations 200, and mobile substations 300 are equipped with lightning signal acquisition devices 400. Each airborne substation 200 is equipped with a wireless signal transmitter 201. The lightning signals collected by the lightning signal acquisition device 400 are processed and modulated, and each airborne substation 200 transmits them at a different frequency. The vehicle-mounted ground master station 100 is equipped with a wireless signal receiver 102. The lightning signals collected by the airborne substations 200 are wirelessly transmitted to the vehicle-mounted ground master station 100 via the wireless signal transmitter 201. The signals received by the wireless signal receiver 102 are demodulated by the FSK demodulation module 103 to obtain signals of different frequencies, and then stored in the data memory 104 of the vehicle-mounted ground master station 100. The vehicle-mounted ground master station 100 is equipped with a data processing and computing unit 105. The data processing and computing unit 105 uses a lightning positioning algorithm to calculate the three-dimensional position of the lightning radiation source through the lightning signal collected by the vehicle-mounted ground master station 100 and the lightning signal returned by the airborne aerial substation 200. The working principle diagram of the present invention is shown in FIG. Figure 2 .

[0033] The vehicle-mounted ground master station 100 uses a vehicle as a mobile ground vehicle, while the airborne substation 200 and mobile substation 300 use rotary-wing drones as mobile aerial vehicles. The vehicle-mounted ground master station 100 is equipped with a drone swarm control system 106, which automatically controls the deployment of the airborne substation 200 according to a set location and automatically controls the replacement of the mobile substation 300 with the airborne substation 200 based on the remaining battery level of the drone. The control range of rotary-wing drones varies depending on the type and application scenario. Consumer drones typically use a handheld remote control with a range of around 1 kilometer. Industrial drones are equipped with measurement and control equipment, with an effective control range of several to tens of kilometers. High-end drones can reach a remote control range of up to 100 kilometers. Typical consumer rotary-wing drones have quadrotors, with a flight altitude limit of no more than 500 meters. Industrial rotary-wing drones, in addition to quadrotors, also have hexacopter and octacopter rotors, and can reach altitudes of nearly 2000 meters. The mobile three-dimensional lightning positioning system of the present invention uses a vehicle-mounted ground main station 100 to transport the airborne aerial substation 200 and the mobile aerial substation 300 to a predetermined area, and a separate transport vehicle may also be configured. The distance between the stations of the lightning detection network is generally no more than 20 kilometers, and an industrial-grade drone with a wingspan of 1 to 2 meters can be used. The endurance of a rotary-wing drone mainly depends on the battery. The endurance of a general drone is 0.5 to 1 hour, and it can reach 2 hours by increasing the battery. However, a lightning process often lasts for several hours. In order to ensure the continuous operation of the airborne aerial substation 200, the present invention adopts a method of replacing the airborne aerial substation 200 with the mobile aerial substation 300. The configuration of the mobile aerial substation 300 and the airborne aerial substation 200 is the same. When the power level of the drone power supply of a certain airborne substation 200 falls below the return power threshold, the mobile airborne substation 300 flies to the airspace of the airborne substation 200 to be replaced and switches the lightning detection device during the interval of lightning to ensure continuous operation of the airborne substation 200. The return position of the replaced airborne substation 200 is determined by the control system of the vehicle-mounted ground master station 100, and the replaced airborne substation 200 lands next to the vehicle-mounted ground master station 100 or the transport vehicle. After the battery is replaced, it serves as a new mobile airborne substation 300. The present invention has at least one mobile airborne substation 300, but is not limited to one. The number is determined based on the number of airborne airborne substations 200. Generally, if there are less than five airborne airborne substations 200, one mobile airborne substation 300 is configured. If there are more than five airborne airborne substations 200, two or more mobile airborne substations 300 can be configured.

[0034] The lightning positioning adopts a system of one master station plus several sub-stations, in order to obtain redundant data to remove ambiguous solutions, the number of sub-stations is at least four to solve the ambiguous solution, the number of sub-stations increases, the redundant positioning data increases, and the result accuracy obtained by the least square method will also be improved. The number of airborne air sub-stations 200 is at least 4 but not limited to 4, the positioning data and redundant data are obtained to remove the ambiguous solution. The number of sub-stations increases, the investment of the system increases, therefore, the number of sub-stations is 4-10. The airborne air sub-stations 200 are arranged in a staggered manner, the vehicle-mounted ground master station 100 is preferably arranged in the middle of the lightning detection network, the airborne air sub-stations 200 are slightly lower near the lightning radiation source P and slightly higher away from the lightning radiation source P, the airborne air sub-stations 200 and the vehicle-mounted ground master station 100 form a three-dimensional mobile lightning detection network of ground layer, low-altitude layer and middle layer, according to the position of lightning occurrence, the arrangement form is changed by moving the vehicle-mounted ground master station 100 and the airborne air sub-stations 200, the spatial form between the lightning detection network and the lightning is adjusted, the best spatial triangular geometric position relationship with the lightning occurrence position is formed, which is beneficial to improve the lightning positioning accuracy. In the actual implementation of the present application, in addition to the airborne air sub-stations 200, 1-2 vehicle-mounted mobile sub-stations can also be arranged, which can move a farther distance and form a larger lightning detection network, and are not limited by the control distance and endurance of the unmanned aerial vehicle. The vehicle-mounted mobile sub-stations and the vehicle-mounted ground master station 100 are connected by a wide area network.

[0035] The system adopts global satellite positioning system GNSS timing to obtain unified coordinate position and absolute time of lightning signal. The GNSS global satellite navigation system can adopt Chinese Beidou satellite navigation system BDS, or American satellite navigation system GPS, Russian satellite navigation system GLONASS, European satellite navigation system GALILEO, preferably BDS or GPS. The vehicle-mounted ground master station 100 is provided with a GNSS global satellite navigation receiving device 101, including a GNSS antenna and a GNSS signal receiver, see Figure 3 The vehicle-mounted ground master station lightning signal collection schematic diagram. The airborne air sub-stations 200 and the mobile air sub-stations 300 obtain GNSS global satellite navigation signals through the GNSS global satellite navigation system built in the unmanned aerial vehicle, see Figure 4The schematic diagram of lightning signal collection of airborne air substation. The vehicle ground master station 100, the airborne air substation 200 and the mobile air substation 300 should adopt the same global satellite positioning system. The GNSS global satellite navigation signal is used for lightning signal timing synchronization, and the precise three-dimensional coordinates of the vehicle ground master station 100 and the airborne air substation 200 are obtained through real-time dynamic carrier phase difference (RTK), which can mark the time stamp of the collected lightning signal and record the coordinates of the station at the moment of lightning occurrence. RTK (Real-time kinematic) is a real-time processing of two measurement station carrier phase observation difference method. The carrier phase collected by the reference station is sent to the user receiver for difference calculation. The vehicle ground master station 100 of the application is used as the reference station, and the airborne air substation 200 is used as the user receiver. The coordinates of each airborne air substation 200 are calculated through the coordinates of the vehicle ground master station 100. The coordinates of the vehicle ground master station 100 are obtained through the GNSS global satellite navigation system, although the accuracy is only meter level, which has met the lightning positioning accuracy requirement, but the coordinate accuracy of the airborne air substation 200 relative to the vehicle ground master station 100 can reach centimeter level through RTK calculation, which can greatly improve the accuracy of lightning positioning calculation.

[0036] The lightning signal acquisition device 400 of this application utilizes an FPGA lightning signal high-speed data acquisition system, primarily composed of FPGA logic gate circuits and an embedded ARM processor. It is implemented using a combination of hardware and software, using the FPGA as hardware and the embedded processor as software. The hardware and software are designed as an organic whole, achieving an optimal combination of hardware and software. An FPGA, or Field Programmable Gate Array, is a chip whose internal structure can be modified through programming. Its full name is Field Programmable Gate Array (FPGA). It is a digital integrated circuit whose internal hardware resources include configurable basic logic units and configurable hardware connections. The FPGA's internal structure can be modified and configured through software to achieve specific design functions. The FPGA design and development process involves programming using a hardware description language, followed by compilation, synthesis, and layout and routing using EDA tools. This is ultimately converted into a burnable file that is loaded into the FPGA device, thereby modifying its internal connections and implementing the desired functionality. The FPGA logic gates implement analog-to-digital conversion control, lightning data acquisition, timestamp acquisition, pre-trigger and trigger control, peak acquisition, and output control. The FPGA logic gates filter the acquired signal, oversample it, calculate the signal amplitude using the Hilbert transform, and extract the trigger peak. The processed data is then temporarily stored in the DDR data storage unit using DMA. After data processing, the lightning signal is output from the FPGA as 16-bit data at 80 MHz, with a data volume of 160 MB / s. However, the maximum data writing rate to the file storage unit via the FATFS file system is 1 MB / s, and file creation time must also be taken into account. Therefore, the lightning signal acquisition speed is much faster than the file writing speed. Using DDR as a cache effectively solves this problem. The DDR data storage unit is an FPGA peripheral device that caches lightning data from the FPGA logic gates to the ARM processing unit. Lightning waveform data, peak data, and time data output by the data processing unit are temporarily transferred to the DDR data storage unit for storage. The ARM processing unit then reads all data from the DDR data storage unit and writes it to the file storage unit, bridging the speed gap between lightning signal acquisition and file writing.

[0037] The lightning signal acquisition device 400 includes a high-speed A / D conversion module 1, a GNSS signal processing unit 2, a data processing unit 3, a DDR data storage unit 4, and an ARM processing unit 5. The high-speed A / D conversion module 1 converts the analog signal output by the lightning detection sensor into a digital signal. The GNSS signal processing unit 2 outputs a high-precision clock frequency as a sampling reference clock for the high-speed A / D conversion module 1, ensuring the accuracy of signal conversion time. The output high-precision full-second clock signal 1PS and NMEA0183 data containing time information are used in conjunction with the sampling reference clock to timestamp the collected lightning signals. The coordinate acquisition module timestamps the RTK coordinates output by the GNSS signal processing unit 2 and outputs the timestamped coordinates. The FPGA logic gate circuits are programmed to form the data processing unit 3, which implements analog-to-digital conversion control, lightning detection data acquisition, timestamp acquisition, coordinate calibration, pre-trigger and trigger control, peak acquisition, and output control. The FPGA logic gate circuits filter, oversample, and Hilbert transform the timestamp-marked signal to calculate the signal amplitude, extract the trigger-determined peak value, and combine the lightning signal with the timestamp-marked coordinates for output. The processed data is temporarily stored in the DDR data storage unit 4 using DMA, and the ARM processing unit 5 is notified to process the data. Upon receiving notification of collected data, the ARM processing unit 5, which has an embedded operating system, extracts the corresponding data from the DDR data storage unit 4 cache. The extracted data includes peak data, corresponding time information, and coordinates.

[0038] The lightning signal acquisition device 400 of the vehicle-mounted ground master station 100 of the present invention is basically the same as that of the airborne aerial substation 200. The difference is that the lightning signal acquisition device 400 of the vehicle-mounted ground master station 100 processes the data through the ARM, extracts the corresponding data from the DDR data storage unit cache, and directly outputs the data to the data memory 104 of the vehicle-mounted ground master station 100 through the file storage module. Figure 3 The lightning signal acquisition device 400 of the airborne substation 200 processes the data through ARM, extracts the corresponding data from the DDR data storage unit cache, and then modulates it through the file storage module and the data modulation module, and then sends it wirelessly to the vehicle-mounted ground master station 100 through the wireless signal transmitting device 201. At the same time, the extracted data is stored in the file storage unit 202 through the file storage module. Figure 4 File storage unit 202 is the local storage of airborne substation 200 and can use either an SD card or a solid-state drive as the storage medium. The data stored in file storage unit 202 serves as a backup for wirelessly transmitted data. After airborne substation 200 returns, the substation number is determined based on the timestamp and coordinates, and the data is copied to data storage 104 of vehicle-mounted ground master station 100.

[0039] The mobile three-dimensional lightning positioning method of the present invention comprises the following steps:

[0040] Step 1: Establish a lightning detection network. Based on weather forecasts and thunderstorm cloud electric field detection, estimate the lightning-prone area. Use the vehicle-mounted ground master station 100 to transport the airborne substation 200 and the mobile airborne substation 300 to the designated area. Alternatively, a separate transport vehicle can be deployed. The vehicle-mounted ground master station 100 or transport vehicle is equipped with a small generator and backup batteries and charging devices for the drones. A lightning detection network is deployed in the lightning-targeted area. The drone swarm control system 106 of the vehicle-mounted ground master station 100 controls the drones of the airborne substation 200 to their designated positions and elevations. The vehicle-mounted ground master station 100 and the airborne substation 200 should be positioned away from mountains and high-rise buildings. The airborne substations 200 should be spaced 5-10 km apart, with a low-altitude layer height of 300-1000 meters and a mid-altitude layer height of 1000-2000 meters. During a continuous lightning event, the positions of the vehicle-mounted ground master station 100 and the airborne aerial substation 200 are fixed. The vehicle-mounted ground master station 100 can move the vehicle-mounted ground master station 100 and control the airborne aerial substation 200 to change the spatial layout according to the direction of the lightning, forming the best spatial triangular geometric position relationship with the lightning location, thereby improving the accuracy of lightning positioning solution.

[0041] Step 2: Lightning signal collection. The vehicle-mounted ground master station 100 and the airborne substation 200 collect lightning signals. The lightning signals collected by the vehicle-mounted ground master station 100 are stored in the local data storage 104. The lightning signals collected by the airborne substation 200 are wirelessly transmitted to the vehicle-mounted ground master station 100 and stored in the data storage 104 of the vehicle-mounted ground master station 100.

[0042] Step 3: Replace the airborne substation 200. The UAV swarm control system 106 of the vehicle-mounted ground master station 100 sets a low-battery return-to-home threshold for each airborne substation 200. The return-to-home threshold is set between 40% and 50% of the full battery level. When the battery level of any airborne substation 200 falls below the return-to-home threshold, the mobile substation 300 begins replacing the airborne substation 200. The UAV swarm control system 106 controls the mobile substation 300 to fly to the airspace of a UAV below the return-to-home threshold and replace the UAV 200. The replaced airborne substation 200 then replaces the battery of the replaced airborne substation 200, replacing the airborne substation 200 with the one with the lowest battery level. This process continues until all airborne substations 200 are replaced. After a round of replacement, the mobile substation 300 waits for the next UAV to fall below the return-to-home threshold before replacing the next airborne substation 200.

[0043] Step 4: Lightning location calculation. The data processing and calculation unit 105 of the vehicle-mounted ground master station 100 uses the time difference (TDOA) of the lightning signal arriving at each measuring station, and according to the known spatial position of the master station S0 ( x 0 ,y 0 ,z 0) and substation S i The spatial position of x i ,y i ,z i ), with the spatial coordinates of the lightning radiation source P ( x, y, z ) is a variable, the electromagnetic waves radiated by the lightning radiation source P reach each substation S i The time difference to the master station S0 is Δ τ i , establish the system of equations and solve it:

[0044] ,

[0045] Where: Δ τ i =( τ 0 - τ i ), c is the propagation speed of electromagnetic waves, τ 0 is the time it takes for the electromagnetic wave radiated by the lightning radiation source to reach the main station, τ i It is the time it takes for the electromagnetic wave radiated by the lightning radiation source to reach the substation. i =1,2,3…… n , n The system of equations is solved using the weighted least squares method to obtain an initial solution. Several lightning arrival locations are obtained by spatial analysis. The initial solution and the constraint variables are used to perform a second weighted least squares estimation, and finally an improved location estimate is obtained.

[0046] This invention can be implemented in collaboration with drone manufacturers to obtain time and coordinate information from the drone's built-in GNSS global satellite navigation system, and even use the drone's image return system to transmit lightning signals. When implementing lightning location, relevant departments should be reported and relevant regulations must be strictly adhered to to ensure flight safety.

[0047] The description and drawings of this application are only a specific implementation method and are not restrictive. Under the guidance of this application, those skilled in the art can make many forms without departing from the purpose of this application and the scope of protection of the claims, all of which are within the scope of protection of this application.

Claims

1. A mobile three-dimensional lightning positioning system, characterized by: The positioning system is composed of a vehicle-mounted ground master station (100), a plurality of airborne aerial substations (200), and a plurality of mobile aerial substations (300). The vehicle-mounted ground master station (100), the airborne aerial substation (200), and the mobile aerial substation (300) are equipped with a lightning signal acquisition device (400). The vehicle-mounted ground master station (100) uses a car as a ground mobile vehicle, and the airborne aerial substation (200) and the mobile aerial substation (300) use a rotary-wing unmanned aerial vehicle as an aerial mobile vehicle. The vehicle-mounted ground master station (100) is equipped with a GNSS global satellite navigation receiving device (101), and the airborne aerial substation (200) and the mobile aerial substation (300) obtain GNSS global satellite navigation signals through the GNSS global satellite navigation system built into the unmanned aerial vehicle. The GNSS global satellite navigation signals are used for lightning signal timing synchronization, and the precise three-dimensional coordinates of the vehicle-mounted ground master station (100) and the airborne aerial substation (200) are obtained through real-time dynamic carrier phase differential (RTK); The number of the airborne aerial substations (200) is at least four, and they obtain positioning data and redundant data to remove ambiguity solutions. The airborne aerial substations (200) are spaced 5 to 10 km apart and arranged at different heights. Together with the vehicle-mounted ground master station (100), they form a three-dimensional mobile lightning detection network that integrates the ground layer, the low-altitude layer, and the mid-altitude layer. The spatial form between the lightning detection network and the lightning can be adjusted according to the location of the lightning by changing the arrangement of the vehicle-mounted ground master station (100) and the airborne aerial substation (200). The vehicle-mounted ground master station (100) is equipped with a drone cluster control system (106), which can automatically control the deployment of the airborne aerial substation (200) according to a set location; and can automatically control the mobile aerial substation (300) to replace the airborne aerial substation (200) according to the set remaining power of the drone; The lightning signal collected by the airborne aerial substation (200) is transmitted back to the vehicle-mounted ground master station (100) via wireless means; the vehicle-mounted ground master station (100) is equipped with a data processing and calculation unit (105), and the data processing and calculation unit (105) uses a lightning positioning algorithm to calculate the three-dimensional position of the lightning radiation source based on the lightning signal collected by the vehicle-mounted ground master station (100) and the lightning signal transmitted back by the airborne aerial substation (200).

2. The mobile three-dimensional lightning positioning system according to claim 1, characterized in that: The lightning signal acquisition device (400) comprises a high-speed A / D conversion module (1), a GNSS signal processing unit (2), a data processing unit (3), a DDR data storage unit (4), and an ARM processing unit (5); the high-speed A / D conversion module (1) converts the analog signal output by the lightning detection sensor into a digital signal; the GNSS signal processing unit (2) outputs a high-precision clock frequency as a sampling reference clock of the high-speed A / D conversion module (1) to ensure the accuracy of the signal conversion time, and the output high-precision full-second clock signal 1PPS and NMEA0183 data with time information are used in conjunction with the sampling reference clock to mark the timestamp of the collected lightning signal; the GNSS signal processing unit (2) outputs RTK coordinates, and the coordinate acquisition module marks the timestamp for the coordinates and outputs the coordinates marked with the timestamp; the lightning signal acquisition device (400) adopts an FPGA lightning signal high-speed data acquisition system, which is mainly composed of an FPGA logic gate circuit and an embedded ARM processor, and the FPGA logic gate circuit is programmed to form a data processing unit. The processing unit (3) realizes analog-to-digital conversion control, lightning data acquisition, timestamp acquisition, pre-trigger and trigger control, peak acquisition, and output control. The FPGA logic gate circuit filters the collected signal, oversamples, calculates the signal amplitude through Hilbert transform, and triggers the peak value extraction function. The lightning signal and the coordinates of the marked timestamp are combined and output. The processed data is temporarily stored in the DDR data storage unit (4) using DMA, and the ARM processing unit (5) is notified to process the data. The ARM processing unit (5) is an embedded operating system. After receiving the notification of the collected data, the peak data and the corresponding time information and coordinates are extracted. The lightning signal collection device (400) of the vehicle-mounted ground main station (100) extracts the corresponding data and stores it in the data storage (104). The lightning signal collection device (400) of the airborne aerial substation (200) extracts the corresponding data and stores it in the file storage unit (202). The airborne aerial substation (200) transmits the modulated signal to the vehicle-mounted ground main station (100) in a wireless manner through the wireless signal transmitting device (201).

3. A mobile three-dimensional lightning positioning method implemented using the mobile three-dimensional lightning positioning system according to any one of claims 1 to 2, characterized in that: The method comprises the following steps: S1. Deploy a lightning detection network in the lightning location area, and control the drones of the airborne aerial substation (200) to be positioned according to the set plane position and elevation through the drone cluster control system (106) of the vehicle-mounted ground master station (100); S2, the vehicle-mounted ground master station (100) and the airborne aerial substation (200) collect lightning signals; S3, setting the low-power return power threshold of the airborne aerial substation (200), when the power of the drone of any airborne aerial substation (200) is lower than the return power threshold, starting the action of replacing the airborne aerial substation (200) with the mobile aerial substation (300); S4. The data processing and calculation unit (105) of the vehicle-mounted ground master station (100) obtains several lightning arrival locations through spatial analysis using the time difference (TDOA) of the lightning signal arriving at each measuring station, obtains an initial solution using the weighted least squares method, and then uses the obtained initial solution and the constraint variables to perform a second weighted least squares estimation to finally obtain an improved position estimate.

4. The mobile three-dimensional lightning positioning method according to claim 3, characterized in that: In the step S1, the vehicle-mounted ground master station (100) and the airborne aerial substation (200) are arranged to avoid mountains and high-rise buildings, the distance between the airborne aerial substations (200) is 5-10 km, the low-altitude layer height is 300-1000 m, and the middle-altitude layer height is 1000-2000 m. During a continuous lightning event, the positions of the vehicle-mounted ground master station (100) and the airborne aerial substation (200) are fixed; during the entire lightning event, the vehicle-mounted ground master station (100) can be moved according to the direction of the lightning occurrence, and the airborne aerial substation (200) can be controlled to change the spatial layout, thereby forming an optimal spatial triangulated geometric position relationship with the lightning occurrence position, thereby improving the lightning location solution accuracy.

5. The mobile three-dimensional lightning positioning method according to claim 3, characterized in that: In the step S3, the return power threshold is set to 40% to 50% of the full power of the power supply. The UAV cluster control system (106) controls the mobile aerial substation (300) to fly to the UAV airspace below the return power threshold, and replaces the airborne aerial substation (200). The replaced airborne aerial substation (200) is replaced with a battery and serves as a new mobile aerial substation (300). The airborne aerial substation (200) with the lowest voltage is replaced, and all airborne aerial substations (200) are gradually replaced. After completing a round of replacement, the mobile aerial substation (300) waits for the next UAV power supply to be lower than the return power threshold, and then performs the replacement of the airborne aerial substation (200).

6. The mobile three-dimensional lightning positioning method according to claim 3, characterized in that: The step S4 adopts the time difference of arrival (TDOA) positioning, based on the known spatial position of the vehicle-mounted ground master station (100) S0 ( x 0 ,y 0 ,z 0) and airborne aerial substation (200)S i The spatial position of x i ,y i ,z i ), with the spatial coordinates of the lightning radiation source P ( x, y, z ) is a variable, the electromagnetic waves radiated by the lightning radiation source reach each airborne aerial substation (200)S i The time difference from the vehicle-mounted ground master station (100) S0 is Δ τ i , establish the equation system and solve it: ， Where: Δ τ i =( τ 0 - τ i ), c is the propagation speed of electromagnetic waves, τ 0 is the time it takes for the electromagnetic wave radiated by the lightning radiation source to reach the vehicle-mounted ground master station (100), τ i is the time it takes for the electromagnetic wave radiated by the lightning radiation source to reach the airborne aerial substation (200), i =1,2,3…… n , n is the number of substations; the weighted least squares method is used to obtain the initial solution of the equation group, and then the second weighted least squares method estimation is performed using the initial solution and the constraint variables to finally obtain the lightning position.

Images