Photo-electromagnetic integrated troposphere lightning detection system

Abstract

The invention discloses a troposphere lightning detection system integrating photoelectromagnetism. The troposphere lightning detection system comprises a detector, a flying platform and a ground center. The detector is provided with a three-dimensional electric field detector, a three-dimensional magnetic field detector, an image collector, a spectrophotometer, a GNSS navigation system, a six-axis sensor and the like. The GNSS receiving devices obtain azimuth angles of the two GNSS receiving devices relative to the true north by adopting carrier phase difference (RTK) through measuring the phase difference between antennas, ECEF coordinates of a detector are obtained through attitude inclination angle correction of a six-axis sensor, and an ENU coordinate system with the ground center as the original point is obtained through coordinate conversion. The image collector shoots lightning images, the spectrophotometer discriminates lightning discharge types, the three-dimensional electric field detector detects vector electric field intensity, the three-dimensional magnetic field detector detects vector magnetic field intensity, the detection system integrates optical, electric and magnetic sensors through a multi-dimensional technology, the limitation of a single sensor is broken through, and the detection precision is improved. Therefore, a troposphere lightning detection system integrated with photoelectromagnetism is formed.

Description

Technical Field

[0001] The present invention relates to the technical field of atmospheric science detection, and particularly to a tropospheric lightning detection system integrated with multiple sensors of optics, electric field, and magnetic field, which is used for real-time detection of tropospheric lightning types, positions, energies, and charge distributions. Background Art

[0002] Most traditional lightning detections adopt ground detection stations. The electric field sensor is used to detect the electric field change generated by lightning to estimate the lightning intensity; the magnetic field antenna is used to detect the transient magnetic field generated by the lightning current, and the lightning is located by magnetic orientation; a high-speed camera or an optoelectronic sensor is used to capture the optical signal of lightning and analyze the luminescence time and intensity; multi-station cooperation is carried out to achieve wide-area positioning based on the time difference of arrival (TOA) or direction finding (DF) of lightning electromagnetic waves. Under the condition of overcast thunderstorm clouds, the visible light of lightning is completely blocked by the clouds, resulting in the system relying on optical sensors being unable to directly capture lightning images or optical signals, and unable to obtain lightning morphology (such as channel branches, luminescence intensity), which restricts the analysis of discharge types and energy estimation.

[0003] In traditional ground lightning detection systems, there are significant technical limitations in the detection of horizontal electric fields (i.e., the electric field component parallel to the ground). The main reasons are as follows: The surface conductivity is high. Assuming the surface is a good conductor, the horizontal electric field is zero. Vegetation, buildings, or terrain undulations near the ground will change the local electric field distribution, generate electric field distortion, and mask the true lightning signal. Electromagnetic interference (such as 50 / 60 Hz power frequency interference) generated by artificial electromagnetic sources such as power lines and communication equipment is much stronger than the lightning horizontal electric field signal (usually a kHz-level transient pulse), resulting in too low signal-to-noise ratio (SNR). Most lightning electric field models (such as the dipole model) assume that the charge center is in the vertical direction of the cloud layer, only calculate the influence of the vertical electric field on the ground, and do not consider horizontal charge separation or in-cloud lateral discharge processes.

[0004] Using satellite remote sensing technology, through optical imaging sensors (such as lightning imagers, multispectral cameras) carried by satellites, the light radiation signals (visible light, near-infrared band) of cloud-top lightning can be captured. However, the satellite is too far from the lightning, and the imaging resolution is limited. Moreover, it is unable to detect the changes in the electric field intensity and magnetic field intensity of lightning. The cost of satellite remote sensing detection is high, which is not conducive to popularization and promotion. Summary of the Invention

[0005] The object of the present invention is to provide a tropospheric lightning detection system integrating optoelectromagnetics, including: a detector, an airborne platform, and a ground center. The detector is provided with a three-dimensional electric field detector, a three-dimensional magnetic field detector, an image collector, a spectrophotometer, a GNSS navigation system, a six-axis sensor, etc. The GNSS receiving device uses carrier phase differential (RTK) to obtain the azimuth angles of two GNSS receiving devices relative to true north by measuring the phase difference between antennas, and obtains the ECEF coordinates of the detector after attitude inclination correction by the six-axis sensor. The true north direction is determined according to the ECEF coordinates, and the ENU coordinate system with the ground center as the origin is obtained through coordinate transformation. The image collector captures lightning images, the spectrophotometer discriminates lightning discharge types, the three-dimensional electric field detector detects the vector electric field intensity, and the three-dimensional magnetic field detector detects the vector magnetic field intensity, thus forming a tropospheric lightning detection system integrating optoelectromagnetics. The lightning images, electric field intensity, magnetic field intensity, optoelectronic signals, ambient temperature, and coordinate data collected by the detector are calculated by an operation module and stored in a data storage module. The data is wirelessly transmitted back to the ground center through a data transmission module. The ground center demodulates the data marked with time stamps to obtain the tropospheric lightning detection results.

[0006] The present invention is realized through the following technical solutions: A tropospheric lightning detection system integrating optoelectromagnetics, including: a detector 100, an airborne platform 200, and a ground center 300. The main body of the detector 100 is a spherical equipment bin 101. Six cantilevers 102 extend outward from the equipment bin 101, including two pairs horizontally and one pair vertically. The three pairs of cantilevers 102 are perpendicular to each other. A spherical probe 103 is provided at the outer end of each cantilever 102. A strip-shaped electrode 104 is provided inside the cantilever 102. One end of the electrode 104 is connected to the probe 103, and the other end is connected to a charge amplifier 105 using a shielded wire. The probe 103 and the electrode 104 form an electric field sensor. Two corresponding probes 103, electrodes 104 and the charge amplifier 105 together form an electric field detector. The electric field detectors in three directions constitute a three-dimensional electric field detector 106. Two GNSS receiving devices 107 are correspondingly provided on a pair of cantilevers 102. Four image collectors 110 are provided inside the equipment bin 101, and four groups of spectrophotometers 111 are provided. The spectrophotometer 111 is arranged below the image collector 110. Each group of spectrophotometers 111 is composed of two APD sensors 112, which are respectively connected to a photometric amplifier 113. One APD sensor 112 is equipped with a red light filter, and one APD sensor 112 is equipped with a blue-violet light filter. A three-dimensional magnetic field antenna 120 and a six-axis sensor 130 are also provided inside the equipment bin 101. The three-dimensional magnetic field antenna 120 is composed of three mutually perpendicular magnetic rod coils. The three magnetic rod coils are respectively parallel to the three pairs of cantilevers 102. The three-dimensional magnetic field antenna 120 is respectively connected to a magnetic field amplifier 121 to constitute a three-dimensional magnetic field detector 122. The six-axis sensor 130'sx The shaft and y the shaft are respectively parallel to two pairs of horizontal cantilevers 102, z and the shaft is parallel to the vertical cantilever 102.

[0007] The three-axis attitude sensor in the six-axis sensor 130 detects the attitudes of the six cantilevers 102, calculates the inclination angles of the two pairs of horizontal cantilevers 102 with respect to the horizontal plane, and the three-axis acceleration sensor measures the magnitude and direction of the acceleration during the movement of the detector 100. The two GNSS receiving devices 107 use carrier-phase differential (RTK) to obtain the azimuth angles of the two GNSS receiving devices with respect to true north by measuring the phase differences between the antennas, obtain the ECEF coordinates of the detector 100 after attitude inclination correction by the six-axis sensor 130, determine the true north direction based on the ECEF coordinates, and obtain the ENU coordinate system with the ground center 300 as the origin ( x 0, y 0, z 0).

[0008] The position of the lightning image recorded by the image collector 110 is obtained, and the azimuth angle of the lightning with respect to the detector 100 in the ENU coordinate system φ and the elevation angle θ are obtained. The electric field intensity detected by the electric field detector 106 and the magnetic field intensity detected by the magnetic field detector 122 are used to calculate the distance between the lightning and the detector 100 by using the amplitude spectrum method r , and the ENU coordinates of the lightning are obtained through the azimuth angle φ of the lightning with respect to the detector (100), θ the elevation angle r and the distance φ ′, the elevation angle θ ′ and the distance r ′ of the lightning with respect to the ground center 300 are calculated.

[0009] The viewing angle of the spectrophotometer 111 is the same as that of the image collector 110. The spectrophotometer 111 equipped with a red light filter and a blue-violet light filter detects whether the lightning recorded by the image collector 110 is corona discharge or arc discharge. The blue-violet light channel signal is significantly stronger than the red light channel corresponding to corona discharge, and the red light channel signal is significantly stronger than the blue-violet light corresponding to arc discharge, so as to analyze the lightning type in the troposphere and study the charge distribution and discharge energy.

[0010] The image collector 110 collects lightning images, the spectrophotometer 111 discriminates the lightning discharge type, the three-dimensional electric field detector 106 detects the vector electric field intensity, the three-dimensional magnetic field detector 122 detects the vector magnetic field intensity, and combines the light intensity (spectrophotometer), the electric field change rate ( dE / dt) and the magnetic field peak value ( B max), estimate the discharge energy through energy integration W , to form an integrated optical, electromagnetic tropospheric lightning detection system.

[0011] When the sum of the brightness differences between two consecutive frames of the image captured by the image collector 110, the signal intensity of the spectrophotometer 111, the electric field intensity detected by the three-dimensional electric field detector 106, and the magnetic field intensity detected by the three-dimensional magnetic field detector 122 reach the set threshold values, they can all be used as trigger signals to trigger the storage of all collected data, and mark the coordinates and time differences.

[0012] The detector 100 is provided with a data processing unit 1, including an ADC analog-to-digital converter 2, an operation module 3, a data storage module 4, a data transmission module 5, and a power supply 6. The lightning images, electric field intensity, magnetic field intensity, optoelectronic signals, ambient temperature, and coordinate data collected by the detector 100 are operated by the operation module 3 and stored in the data storage module 4. The data is wirelessly transmitted back to the ground center 300 through the data transmission module 5. The ground center 300 demodulates the data marked with time stamps to obtain the tropospheric lightning detection results.

[0013] The image collector 110 is arranged between two adjacent horizontal cantilevers 102, configured with a 150° wide-angle lens, and the included angle between the central axis of the image collector 110 and the vertical direction α is 75°, the vertical plane of the central axis forms a 45° angle with the horizontal cantilever 102, and the azimuth of the central axis of the image collector 110 is converted through the azimuth angle of the horizontal cantilever 102.

[0014] The cantilever 102 is made of a fiberglass hollow tube and is vertically fixed on the outer wall of the equipment compartment 101. The probe 103 is fixed at the outer end of the cantilever 102 by a Teflon support. The electrode 104 is arranged inside the cantilever 102, and Teflon brackets are arranged at intervals inside the hollow tube to support the electrode 104.

[0015] The equipment compartment 101 is made of polystyrene foam and is wrapped with high-density polyethylene HDPE inside and outside. The inside of the equipment compartment 101 is provided with a platform or bracket for installing equipment.

[0016] The coordinate conversion is carried out according to the following steps: The Beidou coordinates ( E , L , H ) are converted into ECEF geocentric coordinates ( x , y , z ): , Among them, E is the latitude, L is the longitude,H is the elevation, N is the radius of curvature of the prime vertical, calculated by the formula where a is the semi-major axis of the Earth ellipsoid (6,378,137 m), e 2 is the square of the first eccentricity of the ellipsoid (0.00669438002290). ECEF coordinate difference calculation: , where, ( x 0, y 0, z 0) is the coordinate of the ground center 300, and ( x , y , z ) is the coordinate of the detector 100 at the time of lightning strike; Rotation matrix (ECEF→ENU): , After coordinate transformation, the ENU coordinate system with the ground center 300 as the origin is obtained: , E , N , U represents the coordinate components of the lightning in the local-level north-east-up (ENU) coordinate system centered at the ground center 300. Among them, E is the eastward coordinate (East), N is the northward coordinate (North), U is the up coordinate (Up), R is the rotation matrix, which projects the coordinate difference in the Earth-centered Earth-fixed (ECEF) coordinate system onto the ENU coordinate system, Δ x , Δ y , Δ z is the coordinate difference between the detector 100 and the ground center 300 in the ECEF coordinate system at the time of lightning strike.

[0017] The azimuth angle φ ′, elevation angle θ ′ and distance r ′ of the lightning relative to the ground center 300 are calculated based on the azimuth angle φ and elevation angle θ measured by the detector 100. The unit vector of the lightning direction in the detector coordinate system is: , The coordinate of the ground center 300 is ( x 0, y 0, z 0), and the coordinate of the detector 100 is (x , y , z ), then the position vector of the detector 100 relative to the ground center 300 is: , The distance from the lightning to the detector 100 is r , then the position vector of the lightning in the coordinate system of the ground center 300 is: , The eastward (E) component of the lightning at the ground center 300 is: , The northward (N) component is: , The vertical (U) component is: , The atan2 function of the four quadrants is used to calculate the azimuth angle of the lightning relative to the ground center φ ': , The distance from the lightning in the three-dimensional Euclidean space to the ground center 300 is calculated r ': , The elevation angle of the lightning relative to the ground center is calculated based on the ratio of the vertical component to the total distance θ ': .

[0018] The sum of the brightness differences mentioned above is obtained by comparing the brightness differences of adjacent two frames pixel by pixel and accumulating these difference values. Its mathematical expression is: , Where: Y j ( m , n ) represents the brightness value of the j th frame image at the row and column ([[]] m , n ), Ri represents the preset i th calculation area, k is the total number of preset areas. The image collector 110 mentioned above uses a black and white pixel sensor, and the 8 / 10 / 12-bit data of each pixel is the brightness value Y .

[0019] The beneficial effects of the present invention are as follows: Through multi-dimensional technology, the detection system integrates three types of sensors: light (image + spectrophotometry), electricity (three-axis electric field vector), and magnetism (three-dimensional magnetic field), breaking through the limitations of a single sensor. It can simultaneously obtain the spatial form of lightning (a wide-angle lens captures the bifurcation and direction of the lightning channel), the discharge type (the intensity ratio of red light / violet light distinguishes corona discharge from arc discharge), and the dynamic electromagnetic field (the electric field intensity gradient reflects the charge migration rate, and the magnetic field direction calibrates the current path). Through the synchronous measurement of the vector electric field ( Ex , Ey , Ez )and the vector magnetic field ( Bx , By , Bz ), the charge polarity and density distribution of thunderstorm clouds are inverted, providing direct data support for thunderstorm electricity research. The attitude of the platform is calibrated in real time through GNSS-RTK and the six-axis sensor, improving the accuracy of the electric field vector direction. Using the spectral feature differences of different discharge types, a spectrophotometer is used to identify the lightning discharge type. The multi-sensor (light, electricity, magnetism) joint threshold trigger avoids missed detection of a single signal. It makes up for the defects of traditional ground lightning detection systems that cannot detect horizontal electric fields and cannot obtain the spatial form of lightning above the cloud. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the system of the present invention; Figure 2 Isometric view of the detector; Figure 3 Vertical cross-sectional view of the detector; Figure 4 Horizontal cross-sectional view of the detector; Figure 5 Electrical principle block diagram of the present invention.

[0021] In the figure: 1 - data processing unit, 2 - ADC analog-to-digital converter, 3 - operation module, 4 - data storage module, 5 - data transmission module, 6 - power supply, 100 - detector, 101 - equipment bin, 102 - cantilever, 103 - probe, 104 - electrode, 105 - charge amplifier, 106 - electric field detector, 107 - GNSS antenna, 110 - image collector, 111 - spectrophotometer, 112 - APD sensor, 113 - photometric amplifier, 120 - three-dimensional magnetic field antenna, 121 - magnetic field amplifier, 122 - magnetic field detector, 130 - six-axis sensor, 140 - temperature sensor, 200 - flight platform, 201 - suspension rod, 300 - ground receiving system. DETAILED DESCRIPTION OF THE INVENTION

[0022] For those skilled in the art to better understand the present invention, in combination with Figures 1 to 5To further explain this application, in the description of this specification, the orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship commonly understood by those skilled in the art. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the components or parts referred to must have a specific orientation, be constructed and operated in a specific orientation. The content mentioned in the embodiments does not limit the present invention.

[0023] The integrated optoelectromagnetic tropospheric lightning detection system of the present invention includes: a detector 100, an airborne platform 200, and a ground center 300, as shown in Figure 1 . The main body of the detector 100 is a spherical equipment compartment 101, which is made of polystyrene foam and wrapped with high-density polyethylene HDPE inside and outside. The inner diameter of the equipment compartment 101 is 500 - 800 mm, and the wall thickness is 50 - 150 mm. Six cantilevers 102 extend outward from the equipment compartment 101. The length of the cantilevers 102 extending out of the equipment compartment 101 is 1 - 1.5 m. The six fiberglass cantilevers 102 are distributed in three pairs of orthogonal directions, with two pairs in the horizontal direction and one pair in the vertical direction. The three pairs of cantilevers 102 are perpendicular to each other, as shown in Figure 2 , Figure 3 , Figure 4 . The so-called "horizontal direction" and "vertical direction" refer to the directions when the detector 100 is in a stationary state. A spherical probe 103 is provided at the outer end of each cantilever 102. A strip-shaped electrode 104 is arranged inside the cantilever 102. One end of the electrode 104 is connected to the probe 103, and the other end is connected to a differential charge amplifier 105 using a shielded wire. The probe 103 and the electrode 104 form an electric field sensor. Two corresponding probes 103, electrodes 104 and the charge amplifier 105 together form an electric field detector. The electric field detectors in three directions constitute a three-dimensional electric field detector 106 for detecting the three-dimensional vector electric field intensity. The probe 103 is a hollow sphere made of high-purity copper, and the outer diameter of the sphere is slightly larger than the outer diameter of the cantilever 102. The electrode 104 is made of a high-purity copper strip with a diameter of 3 - 5 mm. The cantilever 102 is made of a fiberglass hollow tube and is vertically fixed on the outer wall of the equipment compartment 101. The probe 103 is fixed at the outer end of the cantilever 102 using a Teflon support. The electrode 104 is arranged inside the cantilever 102, and Teflon brackets are arranged at intervals inside the hollow tube to support the electrode 104. Both the fiberglass hollow tube and the Teflon material have the characteristics of light weight and high insulation, avoiding leakage current interference with the electric field signal from the probe 103 and the electrode 104.

[0024] The detector 100 is equipped with a GNSS global satellite navigation system, and two GNSS receiving devices 107 are correspondingly arranged on a pair of cantilevers 102. A six-axis sensor 130 is arranged inside the equipment compartment 101. The x axis and y axis of the six-axis sensor 130 are respectively parallel to the two pairs of horizontal cantilevers 102,z The axis is parallel to the vertical cantilever 102. The three-axis attitude sensor in the six-axis sensor 130 detects the attitudes of the six cantilevers 102, calculates the inclination angles of the two pairs of horizontal cantilevers 102 with respect to the horizontal plane, and is used to correct the attitude during the movement of the detector 100 when calculating the azimuth and elevation angles. The three-axis acceleration sensor measures the magnitude and direction of the acceleration during the movement of the detector 100. The corresponding two GNSS receiving devices 107 use carrier phase differential (RTK) to obtain the azimuth angles of the two GNSS receiving devices relative to true north by measuring the phase difference between the antennas, and obtain the ECEF coordinates of the detector 100 after correcting with the attitude inclination angle of the six-axis sensor 130, and determine the true north direction according to the ECEF coordinates. The ground center 300 is also provided with a GNSS global satellite navigation system, and an ENU coordinate system with the ground center 300 as the origin ( x 0, y 0, z 0) is obtained through coordinate transformation. The GNSS global satellite navigation system can use China's Beidou satellite navigation system BDS, or use the US satellite navigation system GPS, the Russian satellite navigation system GLONASS, and the EU satellite navigation system GALILEO. BDS or GPS is preferred.

[0025] A three-dimensional magnetic field antenna 120 is provided in the equipment compartment 101, which consists of three mutually perpendicular magnetic rod coils. The three magnetic rod coils are respectively parallel to the three pairs of cantilevers 102. The three-dimensional magnetic field antenna 120 is respectively connected to a magnetic field amplifier 121 to form a three-dimensional magnetic field detector 122 for detecting the three-dimensional vector magnetic field intensity.

[0026] Four image collectors 110 are provided in the equipment compartment 101. The image collectors 110 use black and white pixel sensors and use global shutter CMOS cameras. The global shutter CMOS camera is an imaging device that uses synchronous exposure technology. Each pixel of the global shutter CMOS camera is equipped with an independent storage unit. Its core feature is that all pixels start and end exposure at the same time, and transfer the charge to the storage area after the exposure ends, and then read out the signal line by line, effectively solving the problem of image deformation of traditional rolling shutters when shooting high-speed moving objects, avoiding motion blur, and supporting high frame rates. The global shutter CMOS camera preferably selects Sony IMX925, and its high frame rate and low noise characteristics can accurately capture the lightning track. The image collectors 110 are configured with a 150° wide-angle lens. The image collectors 110 are arranged between two adjacent horizontal cantilevers 102, see Figure 4, to avoid the cantilever 102 from blocking, there will be overlapping in the lightning images captured by the image collector 110. If the lightning image captured by one image collector 110 is exactly blocked by a cantilever 102, the adjacent image collector 110 can capture a complete lightning image. The vertical plane of the central axis of the image collector 110 forms a 45° angle with the horizontal cantilever 102, and the azimuth of the central axis of the image collector 110 is converted through the azimuth angle of the horizontal cantilever 102. See Figure 4 . The angle α between the central axis of the image collector 110 and the vertical direction is 75°, see Figure 3 , Figure 3 . In , the image collector 110 is not directly below the cantilever 102, but forms a 45° angle. The image collector 110 cannot be cut in the vertical sectional view. In order to facilitate the display of the angle α with the vertical direction, it is drawn. The four image collectors 110 cover 360° horizontally and are docked vertically at the bottom. The upper part of the picture is 60° higher than the horizontal plane. The upper part of the detector 100 is blocked by the flight platform 200 within a 60° range and is not considered.

[0027] Four groups of spectrophotometers 111 are provided in the equipment compartment 101. The spectrophotometers 111 are arranged below the image collectors 110. The spectrophotometers 111 are configured with a 150° wide-angle lens, and the viewing angle is the same as that of the image collectors 110. Each group of spectrophotometers 111 consists of two APD sensors 112. The APD sensors 112 use avalanche diodes and have a fast response time. Their optoelectronic response speed can reach dozens of gigahertz and can quickly convert optical signals into electrical signals. The APD sensors 112 are respectively connected to the photometric amplifiers 113. One APD sensor 112 is equipped with a red light filter, and one APD sensor 112 is equipped with a blue-violet light filter. The spectrophotometers 111 equipped with red light filters and blue-violet light filters are used to detect whether the lightning recorded by the image collectors 110 is corona discharge or arc discharge. The signal of the blue-violet light channel is significantly stronger than that of the red light channel corresponding to corona discharge, and the signal of the red light channel is significantly stronger than that of the blue-violet light corresponding to arc discharge, which is used to analyze the lightning type in the troposphere and study the charge distribution and discharge energy.

[0028] A temperature sensor 140 is also provided in the equipment compartment 101. The performance of the optical, electrical, and magnetic sensors in the lightning detection system is easily affected by temperature drift. The temperature sensor monitors the ambient temperature in real time and compensates for the thermal expansion effect of the optical device and the baseline shift of the electrical / magnetic sensor through an algorithm. Extreme temperature changes (such as strong turbulence in the troposphere) will introduce electromagnetic signal noise. The temperature sensor is synchronously measured with the electric field vector ( Ex , Ey , Ez ), which can distinguish real lightning signals from thermal noise interference.

[0029] The detector 100 is provided with a data processing unit 1, including an ADC analog-to-digital converter 2, an operation module 3, a data storage module 4, a data transmission module 5, and a power supply 6, as shown in Figure 5 . The data transmission module 5 uses frequency-shift keying (FSK) modulation to modulate the signal, converts binary data into an FSK signal, and the modulated signal is transmitted by the transmitter. The dedicated meteorological radiosonde frequency band of 403 MHz is used for wireless communication to transmit detection data in real time. After the ground center 300 receives it, it demodulates the received FSK signal back into binary data. The data transmission module 5 stores the lightning images, electric field intensity, magnetic field intensity, optoelectronic signals, ambient temperature, and coordinate data collected by the detector 100 in the data storage module 4 after being calculated by the operation module 3. The data is wirelessly transmitted back to the ground center 300 through the data transmission module 5. The ground center 300 demodulates the data marked with a timestamp to obtain the tropospheric lightning detection result.

[0030] The charge amplifier 105, the photometric amplifier 113, and the magnetic field amplifier 121 use the ADA4530-1 amplifier chip, which supports dual input modes of current and voltage, with a gain range of 0.01 to 1000 mV / pC, built-in adjustable high-pass (0.3 to 100 Hz) and low-pass (0.3 to 100 kHz) filters to optimize the signal-to-noise ratio, and low noise (≤5 μV), suitable for amplifying weak signals. The ADC analog-to-digital converter 2 can use the AD7606C conversion chip, which has 8 analog input channels, 16-bit resolution, and a sampling rate of 1 MSPS, with good performance. In this application, two AD7606C conversion chips can be combined to quickly sample and convert multiple-channel signals in sequence to achieve synchronous sampling of multiple channels. The components of all units and modules are installed on the PCB board according to their functions and are waterproof encapsulated in the device box. The interior of the equipment compartment 101 is provided with a platform or bracket for installing equipment. The spherical equipment compartment 101 is divided into upper and lower parts. The lower part accounts for 60 to 70% of the diameter to ensure that the cantilever 102 can be stably installed with the equipment compartment 101. The upper part is equivalent to the hatch cover. Opening the hatch cover facilitates the installation of internal devices. The upper and lower parts are provided with connection and fixing devices, and there is a sealing device at the connection. The protection level of the equipment compartment 101 is IP68.

[0031] The ground cannot directly observe the direction of lightning above the cloud. To facilitate the ground center 300 to judge the position of lightning above the cloud, the longitude and latitude coordinates of the GNSS satellite navigation system of the detector 100 in this application are converted into an ENU (East-North-Up) coordinate system with the ground center 300 as the origin. The coordinate conversion is carried out according to the following steps: Beidou coordinates ( E , L , H ) are converted into ECEF geocentric coordinates ( x ,y , z ): , wherein, E is the latitude, L is the longitude, H is the elevation, N is the radius of curvature of the prime vertical, calculated by the formula ; a is the semi-major axis of the Earth ellipsoid (6,378,137 m), e 2 is the square of the first eccentricity of the ellipsoid (0.00669438002290); ECEF coordinate difference calculation: , wherein, ( x 0, y 0, z 0) is the coordinate of the ground center 300, ( x , y , z ) is the coordinate of the detector 100 at the time of lightning strike; Rotation matrix (ECEF→ENU): , After coordinate transformation, the ENU coordinate system with the ground center 300 as the origin is obtained: , E , N , U represents the coordinate components of the lightning in the northeast - up coordinate system (ENU) centered on the ground center 300. Among them, E is the east - ward coordinate (East), N is the north - ward coordinate (North), U is the up - ward coordinate (Up), R is the rotation matrix, which projects the coordinate difference of the Earth - centered Earth - fixed coordinate system (ECEF) onto the ENU coordinate system, Δ x , Δ y , Δ z is the coordinate difference between the detector 100 and the ground center 300 in the ECEF coordinate system at the time of lightning strike.

[0032] The position of the lightning image recorded by the image collector 110 is used to obtain the azimuth angle φ and the elevation angle θ of the lightning relative to the detector 100 in the ENU coordinate system. The electric field strength detected by the electric field detector 106 and the magnetic field strength detected by the magnetic field detector 122 are used to calculate the distance r, the ENU coordinates of lightning are obtained by the azimuth φ , elevation θ and distance r of lightning relative to the detector 100, and the azimuth φ ′, elevation θ ′ and distance r ′ of lightning relative to the ground center 300 are calculated. Based on the azimuth φ and elevation θ measured by the detector 100, the unit vector of the lightning direction in the detector coordinate system is: , The coordinates of the ground center 300 are ( x 0, y 0, z 0), and the coordinates of the detector 100 are ( x , y , z ). Then the position vector of the detector 100 relative to the ground center 300 is: , The distance from lightning to the detector 100 is r . Then the position vector of lightning in the coordinate system of the ground center 300 is: , The eastward (E) component of lightning at the ground center 300 is: , The northward (N) component is: , The vertical (U) component is: , The azimuth φ ′ of lightning relative to the ground center is calculated using the four-quadrant arctangent function atan2: , The distance r ′ from lightning to the ground center 300 in three-dimensional Euclidean space is obtained: , The elevation θ ′ of lightning relative to the ground center is calculated based on the ratio of the vertical component to the total distance: .

[0033] When the sum of the brightness differences between two consecutive frames of the images captured by the image collector 110, the signal intensity of the spectrophotometer 111, the electric field intensity detected by the three-dimensional electric field detector 106, and the magnetic field intensity detected by the three-dimensional magnetic field detector 122 reach the set threshold values, they can all be used as trigger signals to trigger the storage of all the collected data, and mark the coordinates and time differences. The multi-sensor (light, electricity, magnetism) combined threshold trigger can avoid missing detections of single signals. The image collector 110 collects lightning images, the spectrophotometer 111 discriminates the types of lightning discharges, the three-dimensional electric field detector 106 detects the vector electric field intensity, and the three-dimensional magnetic field detector 122 detects the vector magnetic field intensity. By combining the light intensity (spectrophotometer), the electric field change rate ( dE / dt ) and the magnetic field peak value ( B max), the discharge energy is estimated through energy integration W , forming an integrated optical, electromagnetic tropospheric lightning detection system.

[0034] The sum of the brightness differences is obtained by comparing the brightness differences of adjacent two frames pixel by pixel and accumulating these difference values to obtain the total brightness change amount. Its mathematical expression is: , where: Y j ( m , n ) represents the brightness value of the j -th frame image at the row and column ( m , n ), Ri represents the preset i -th calculation area, k is the total number of preset areas; the image collector 110 uses a black and white pixel sensor, and the 8 / 10 / 12-bit data of each pixel is the brightness value Y .

[0035] The detector 100 is suspended below the flight platform 200 by the boom 201. The flight platform 200 can be a controllable balloon, a fixed-wing unmanned aerial vehicle, a rocket, etc., and a controllable balloon is preferably selected. The controllable balloon realizes precise regulation of height, position and function through the integration of advanced materials, intelligent control algorithms and innovative structural designs, and is suitable for tropospheric lightning detection.

[0036] The power supply 6 is powered by a lithium battery and is set at the center of the bottom of the equipment compartment 101 to maintain the balance of the equipment compartment 101. The equipment compartment 101 has a polystyrene foam insulation layer, and the heat generated by the battery maintains the temperature inside the compartment. If the temperature inside the compartment cannot meet the working requirements of the electronic devices, a heating agent can be placed in the equipment compartment 101 before the detector 100 takes off. The simplest method is to place the commonly used warm baby in daily life.

[0037] Before conducting tropospheric lightning detection, debug the communication between the detector 100 and the ground center 300, select an appropriate window period to lift the airborne platform 200, and the detector 100 then enters the troposphere to detect lightning images, electric field strength, magnetic field strength, discharge types, ambient temperature, the ENU coordinates of the detector 100 and the lightning relative to the ground center 300, as well as the azimuth angle of the detector 100 relative to the ground center 300 φ , elevation angle θ and distance r , the azimuth angle of the lightning relative to the ground center 300 φ ′, elevation angle θ ′ and distance r ′, and implement the transmission back to the ground center 300

[0038] The description and drawings of this application are only a specific embodiment and not restrictive. Those skilled in the art, under the inspiration of this application and without departing from the purpose of this application and the scope protected by the claims, can also make many forms, all of which are within the protection scope of this application

Claims

1. An integrated optoelectromagnetic tropospheric lightning detection system, characterized in that: Including: Detector (100), flight platform (200), ground center (300); The main body of the detector (100) is a spherical equipment bin (101). Six cantilevers (102) extend outward from the equipment bin (101), including two pairs horizontally and one pair vertically. The three pairs of cantilevers (102) are perpendicular to each other. A spherical probe (103) is provided at the outer end of each cantilever (102). A strip-shaped electrode (104) is provided inside the cantilever (102). One end of the electrode (104) is connected to the probe (103), and the other end is connected to a charge amplifier (105) using a shielded wire. The probe (103) and the electrode (104) form an electric field sensor. Two corresponding probes (103), electrodes (104), and the charge amplifier (105) together form an electric field detector. The electric field detectors in three directions constitute a three-dimensional electric field detector (106); Two GNSS receiving devices (107) are correspondingly provided on a pair of cantilevers (102); Four image collectors (110) are provided inside the equipment bin (101), and four sets of spectrophotometers (111) are provided. The spectrophotometers (111) are arranged below the image collectors (110). Each set of spectrophotometers (111) consists of two APD sensors (112), which are respectively connected to a photometric amplifier (113). One APD sensor (112) is equipped with a red light filter, and one APD sensor (112) is equipped with a blue-violet light filter; A three-dimensional magnetic field antenna (120), a six-axis sensor (130), and a temperature sensor (140) are also provided inside the equipment bin (101); The three-dimensional magnetic field antenna (120) is composed of three mutually perpendicular magnetic rod coils. The three magnetic rod coils are respectively parallel to the three pairs of cantilevers (102). The three-dimensional magnetic field antenna (120) is respectively connected to a magnetic field amplifier (121) to form a three-dimensional magnetic field detector (122); The x axis and y axis of the six-axis sensor (130) are respectively parallel to the two pairs of horizontal cantilevers (102), and the z-axis is parallel to the vertical cantilever (102); The three-axis attitude sensor in the six-axis sensor (130) detects the attitudes of the six cantilevers (102), calculates the angles of inclination of the two pairs of horizontal cantilevers (102) with respect to the horizontal plane, and the three-axis acceleration sensor measures the magnitude and direction of the acceleration during the movement of the detector (100); the two GNSS receiving devices (107) use carrier-phase differential (RTK) to obtain the azimuth angles of the two GNSS receiving devices relative to true north by measuring the phase difference between the antennas, obtain the ECEF coordinates of the detector (100) after attitude inclination correction by the six-axis sensor (130), determine the true north direction based on the ECEF coordinates, and obtain the ENU coordinate system with the ground center (300) as the origin ( x 0, y 0, z 0). The position of the lightning image recorded by the image collector (110) is used to obtain the azimuth angle of the lightning relative to the detector (100) in the ENU coordinate system φ and the elevation angle θ ; The electric field intensity detected by the electric field detector (106) and the magnetic field intensity detected by the magnetic field detector (122) are used to calculate the distance between the lightning and the detector (100) by using the amplitude spectrum method r , and through the azimuth angle of the lightning relative to the detector (100) φ , the elevation angle θ and the distance r the ENU coordinates of the lightning are obtained, and the azimuth angle φ ′, the elevation angle θ ′ and the distance r ′ of the lightning relative to the ground center (300) are calculated The viewing angle of the spectrophotometer (111) is the same as that of the image collector (110). The spectrophotometer (111) equipped with a red light filter and a blue-violet light filter is used to detect whether the lightning recorded by the image collector (110) is corona discharge or arc discharge. For corona discharge, the signal of the blue-violet light channel is significantly stronger than that of the red light channel; for arc discharge, the signal of the red light channel is significantly stronger than that of the blue-violet light. Analyze the types of tropospheric lightning and study the charge distribution and discharge energy; The described image collector (110) collects lightning images, the spectrophotometer (111) discriminates lightning discharge types, the three-dimensional electric field detector (106) detects vector electric field intensity, the three-dimensional magnetic field detector (122) detects vector magnetic field intensity, and by combining light intensity (spectrophotometer), electric field change rate ( dE / dt ), and magnetic field peak value ( B max), the discharge energy is estimated through energy integration W , thus forming an integrated optical, electromagnetic tropospheric lightning detection system; When the sum of the brightness differences between two consecutive frames of the image taken by the image collector (110), the signal intensity of the spectrophotometer (111), the electric field intensity detected by the three-dimensional electric field detector (106), and the magnetic field intensity detected by the three-dimensional magnetic field detector (122) reach the set threshold values, they can all be used as trigger signals to trigger the storage of all collected data, and mark the coordinates and time differences; The detector (100) is provided with a data processing unit (1), including an ACD analog-to-digital converter (2), an operation module (3), a data storage module (4), a data transmission module (5), and a power supply (6). The lightning images, electric field intensity, magnetic field intensity, optoelectronic signals, ambient temperature, and coordinate data collected by the detector (100) are operated by the operation module (3) and stored in the data storage module (4). The data is wirelessly transmitted back to the ground center (300) through the data transmission module (5). The ground center (300) demodulates the data marked with time stamps to obtain the tropospheric lightning detection results.

2. The integrated optoelectromagnetic tropospheric lightning detection system according to claim 1, wherein: The described image collector (110) is arranged between two adjacent horizontal cantilevers (102), equipped with a 150° wide-angle lens. The central axis of the image collector (110) forms an angle of α 75° with the vertical direction, and the vertical plane of the central axis forms a 45° angle with the horizontal cantilever (102). The orientation of the central axis of the image collector (110) is converted through the orientation of the horizontal cantilever (102).

3. The integrated optoelectromagnetic tropospheric lightning detection system according to claim 1, characterized in that: The cantilever (102) is made of a fiberglass hollow tube and is vertically fixed on the outer wall of the equipment compartment (101). The probe (103) is fixed to the outer end of the cantilever (102) by a Teflon support. The electrode (104) is arranged inside the cantilever (102), and Teflon brackets are arranged at intervals inside the hollow tube to support the electrode (104).

4. The integrated optoelectromagnetic tropospheric lightning detection system according to claim 1, characterized in that: The equipment compartment (101) is made of polystyrene foam and is wrapped with high-density polyethylene HDPE on the inner and outer layers. The inside of the equipment compartment (101) is provided with a platform or bracket for installing equipment.

5. The integrated optoelectromagnetic tropospheric lightning detection system according to claim 1, wherein: The coordinate transformation is carried out according to the following steps: The Beidou coordinates ( E , L , H ) are converted to the ECEF geocentric coordinates ( x , y , z ): ， Wherein: E is the latitude, L is the longitude, H is the elevation, N is the radius of curvature of the prime vertical, calculated by the formula ; a is the semi-major axis of the Earth ellipsoid (6,378,137 m), e 2 is the square of the first eccentricity of the ellipsoid (0.00669438002290); Calculation of ECEF coordinate difference: ， Wherein: ( x 0, y 0, z 0) are the coordinates of the ground center (300), ( x , y , z ) are the coordinates of the detector (100) when lightning occurs; Rotation matrix (ECEF→ENU): ， After coordinate transformation, the ENU coordinate system with the ground center (300) as the origin is obtained: ， E , N , U represent the coordinate components of lightning in the northeast celestial coordinate system (ENU) centered on the ground center (300), where, E is the eastward coordinate (East), N is the northward coordinate (North), U is the zenith direction coordinate (Up), R is the rotation matrix that projects the coordinate difference of the Earth-centered Earth-fixed coordinate system (ECEF) onto the ENU coordinate system, Δ x , Δ y , Δ z is the coordinate difference between the detector (100) and the ground center (300) in the ECEF coordinate system when lightning occurs.

6. The integrated optoelectromagnetic tropospheric lightning detection system according to claim 1, characterized in that: The azimuth angle of the lightning relative to the ground center (300) φ ′, elevation angle θ ′ and distance r ′ are calculated based on the azimuth angle φ and elevation angle θ measured by the detector (100). The unit vector of the lightning direction in the detector coordinate system is: ， The coordinates of the ground center (300) are ( x 0, y 0, z 0), and the coordinates of the detector (100) are ( x , y , z ). Then the position vector of the detector (100) relative to the ground center (300) is: ， The distance from the lightning to the detector (100) is r , then the position vector of the lightning in the coordinate system of the ground center (300) is: ， The eastward (E) component of the lightning at the ground center (300) is: ， The northward (N) component is: ， The vertical (U) component is: ， Use the four-quadrant arctangent function atan2 to calculate the azimuth angle of lightning relative to the ground center φ ′: ， Determine the distance from a three-dimensional Euclidean space lightning to the ground center (300) r ′: ， Calculating the elevation and depression angles of lightning relative to the ground center based on the ratio of the vertical component to the total distance θ ′: 。 7. The integrated optoelectromagnetic tropospheric lightning detection system according to claim 1, characterized in that: The sum of the brightness differences is obtained by comparing the brightness differences of adjacent two frames pixel by pixel and accumulating these difference values. Its mathematical expression is: ， Wherein: Y j ( m , n ) represents the luminance value of the j th frame image at the row and column ( m , n ), Ri represents the i th preset calculation area, k is the total number of preset areas; the image collector (110) uses a black-and-white pixel sensor, and the 8 / 10 / 12-bit data of each pixel is the luminance value Y .

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