Three-dimensional vector aerial transient electromagnetic receiving antenna structure and vector correction method

Abstract

The application discloses a three-dimensional vector aviation transient electromagnetic receiving antenna structure and a vector correction method, which comprises a three-dimensional vector receiving antenna body, an inertial navigation sensor and a data acquisition module; the three-dimensional vector receiving antenna body comprises three transient electromagnetic receiving coils with the same specifications, and the three transient electromagnetic receiving coils are arranged orthogically along XYZ three-dimensional space directions; the inertial navigation sensor is installed at the body center, the top center or the bottom center of the three-dimensional vector receiving antenna body, and comprises a three-axis magnetic field sensor, a three-axis acceleration sensor and a three-axis angular velocity sensor; the three-axis coordinate system of the inertial navigation sensor is coaxially aligned with the XYZ three-axis coordinate system of the three transient electromagnetic receiving coils; and the data acquisition module is electrically connected with the three transient electromagnetic receiving coils and the inertial navigation sensor respectively, and is used for synchronously collecting the transient electromagnetic field signals output by the three transient electromagnetic receiving coils and the full-quantity inertial navigation data output by the inertial navigation sensor.

Description

Technical Field

[0001] This invention belongs to the field of airborne transient electromagnetic detection technology, specifically relating to a three-dimensional vector airborne transient electromagnetic receiving antenna structure and a vector correction method. Background Technology

[0002] Airborne transient electromagnetic exploration (AEIA) technology is widely used in mineral resource exploration, hydrogeological surveys, and engineering geological investigations due to its high detection efficiency and wide coverage. As the core component of an AEIA system, the accuracy of the electromagnetic field signals acquired by the receiving antenna directly determines the reliability of the exploration results.

[0003] Existing transient electromagnetic receiving antennas for aviation mostly adopt single-axis or dual-axis coil structures, which makes it difficult to achieve full-dimensional acquisition of three-dimensional vector electromagnetic fields. Although some three-dimensional coil antennas have achieved XYZ three-axis arrangement, due to the continuous changes in the attitude of the aircraft during flight (pitch, roll, yaw), there is a deviation between the antenna coordinate system and the standard geographic coordinate system, resulting in significant attitude disturbance errors in the acquired electromagnetic field signals.

[0004] Current methods for correcting antenna attitude errors mostly employ Euler angle rotation, but Euler angles suffer from gimbal lock, which can easily lead to rotation calculation failures. Furthermore, existing methods suffer from asynchronous acquisition of electromagnetic field signals and attitude data, and lack timing control over the power-on / off cycles of transient electromagnetic signals, further introducing measurement errors. In addition, traditional correction algorithms have low attitude calculation accuracy, making them unsuitable for the dynamic and complex scenarios of aerial surveying.

[0005] Airborne Transient Electromagnetic (ATEM) is a highly efficient airborne geophysical exploration technique. It involves transmitting pulsed electromagnetic fields into the subsurface via an airborne transmitting system and then collecting the secondary induced electromagnetic fields generated by the subsurface medium through a receiving antenna. The electrical distribution characteristics of the subsurface medium are then obtained through inversion. ATEM is widely used in mineral resource exploration, hydrogeological surveys, environmental geological monitoring, and urban underground space exploration.

[0006] Existing transient electromagnetic technology in aviation has the following core defects: The receiving antennas mostly use single-component or dual-component coils, which cannot simultaneously acquire underground three-dimensional vector electromagnetic field information, resulting in insufficient vertical and horizontal resolution in exploration, making it difficult to achieve accurate imaging of the three-dimensional electrical structure of underground media. During flight, the receiving antenna will undergo attitude changes such as pitch, roll, and yaw as the aircraft moves, resulting in severe attitude distortion in the collected electromagnetic field data. Existing technologies mostly use post-event Euler angle rotation correction, which has a gimbal lock problem. Under large attitude angle scenarios, the correction accuracy is extremely low, and even calculation failure may occur. Existing technologies have not achieved strict synchronous acquisition of transient electromagnetic signals and attitude data, resulting in timing misalignment and mismatch between attitude data and electromagnetic field data, which further reduces the accuracy of correction. Attitude data acquisition did not avoid strong electromagnetic interference from the rising edge of TEM (Transient Electromagnetic) signal turn-on and falling edge of turn-off. The measurement data of the inertial navigation sensor is susceptible to interference from transmitted pulses, which leads to distortion of attitude calculation results and ultimately affects the reliability of exploration data. Summary of the Invention

[0007] To address the aforementioned shortcomings of existing technologies, this invention provides a three-dimensional vector aeronautical transient electromagnetic receiving antenna structure and vector correction method. On one hand, through the integrated structural design of a triaxial orthogonal coil and an inertial navigation sensor, high-precision synchronous acquisition of three-dimensional vector electromagnetic fields is achieved. On the other hand, through EKF quaternion attitude calculation, quaternion rotation vector correction, and a strict timing synchronization acquisition scheme, core issues such as gimbal lock, timing misalignment, and electromagnetic interference in attitude correction are solved, significantly improving the acquisition accuracy and correction accuracy of aeronautical transient electromagnetic three-dimensional vector data.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a three-dimensional vector airborne transient electromagnetic receiving antenna structure, including a three-dimensional vector receiving antenna body, an inertial navigation sensor, and a data acquisition module; The three-dimensional vector receiving antenna body includes three transient electromagnetic receiving coils of identical specifications, and the three receiving coils are orthogonally arranged along the XYZ axes respectively; The inertial navigation sensor integrates a three-axis magnetic field sensor, a three-axis acceleration sensor, and a three-axis angular velocity sensor. The three-axis coordinate system of the inertial navigation sensor is completely coaxially aligned with the XYZ three-axis coordinate system of the three receiving coils (the origin of the coordinate system coincides, the corresponding three axes are parallel and coaxial, and the coordinate systems are completely coincident). The inertial navigation sensor is fixedly installed at the center of the body, top center, or bottom center of the three-dimensional vector receiving antenna body; The data acquisition module is electrically connected to the three receiving coils and the inertial navigation sensor, respectively, and is used to synchronously acquire the transient electromagnetic field signals output by the three receiving coils and the full inertial navigation data output by the inertial navigation sensor. The full inertial navigation data includes three-axis magnetic field data, three-axis acceleration data, and three-axis angular velocity data.

[0009] Furthermore, the receiving coil is a circular coil, and after the three circular coils are arranged orthogonally, the outer contour of the three-dimensional vector receiving antenna body has a spherical structure; or the receiving coil is a square coil, and after the three square coils are arranged orthogonally, the outer contour of the three-dimensional vector receiving antenna body has a cubic structure.

[0010] Furthermore, the orthogonality error of the three receiving coils along the XYZ axes is ≤0.1°, the parallelism error between the corresponding axes of the inertial navigation sensor and the receiving coils is ≤0.05°, and the coincidence error of the coordinate system origin is ≤0.02mm.

[0011] Furthermore, the data acquisition module has a built-in timing control unit, which is synchronized with the timing of the aviation transient electromagnetic launch system to distinguish between the power supply cycle and the shutdown cycle of the TEM signal, thus avoiding the acquisition window of the rising edge of the turn-on and the falling edge of the shutdown.

[0012] Secondly, this invention provides a three-dimensional vector aeronautical transient electromagnetic vector correction method, implemented based on the above-mentioned receiving antenna structure, comprising the following steps: S1. System initialization and parameter calibration: Complete the installation accuracy calibration of antenna and sensor, static calibration of sensor parameters, initialization of EKF algorithm parameters, and setting of standard reference coordinate system; S2. Synchronous data acquisition: Through timing control, the full inertial navigation data during the TEM signal power-on cycle and the power-off cycle are acquired synchronously, as well as the XYZ three-axis transient electromagnetic field intensity data of the three receiving coils during the TEM signal power-off cycle. The acquisition process avoids the rising edge of the TEM signal during conduction and the falling edge of the TEM signal during power-off. S3. Real-time attitude calculation based on EKF algorithm: Using quaternions and gyroscope deviation as state vectors and accelerometer and magnetometer measurements as observation vectors, the optimal attitude quaternion of the antenna at the current moment is calculated in real time through the prediction and update steps of the EKF algorithm. S4. Electromagnetic field strength vector rotation correction: The transient electromagnetic field strength collected in the antenna's own coordinate system is converted into a quaternion expression. Based on the attitude quaternion obtained in step S3, a rotation matrix is ​​constructed. The electromagnetic field strength is transformed to the standard reference coordinate system through coordinate system rotation to obtain the corrected standard electromagnetic field strength data. S5. Verification and Output of Corrected Data: Verify the validity of the corrected electromagnetic field strength data, mark abnormal data, output the corrected data in real time, and store the original acquired data and the corrected data.

[0013] Compared with the prior art, the present invention has the following significant advantages: This invention, through the integrated structural design of triaxial orthogonal coils, can simultaneously acquire three-dimensional vector electromagnetic field information in the XYZ directions, significantly improving the vertical and horizontal resolution of airborne transient electromagnetic exploration, and providing high-quality raw data for precise imaging of the three-dimensional electrical structure of underground media. This invention achieves synchronous acquisition of transient electromagnetic signals and attitude data at the same frequency and in the same phase by coaxially and with high precision mounting of the inertial navigation sensor and the receiving coil, combined with a strict timing synchronization acquisition scheme. At the same time, it avoids strong electromagnetic interference from the rising edge of the TEM signal on and the falling edge of the TEM signal off, thus ensuring the timing matching and measurement accuracy of the correction data from the source. This invention employs the EKF algorithm based on quaternions for attitude calculation, effectively avoiding the gimbal lock problem of traditional Euler angle calculation. It can calculate antenna attitude in real time and with high precision in all attitude angle scenarios, while simultaneously compensating for gyroscope deviations online, thus significantly improving the attitude calculation accuracy in dynamic aviation environments. This invention achieves coordinate system transformation of electromagnetic field intensity through a quaternion rotation matrix, and completes synchronous vector correction in conjunction with the attitude results calculated in real time. This completely eliminates the distortion effect of antenna attitude changes on electromagnetic field data during flight. The corrected data is unified to the true north horizontal reference coordinate system, improving data consistency and reliability, and reducing the relative error of the corrected data. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the three-dimensional vector aerospace transient electromagnetic receiving antenna structure with a circular coil sphere structure according to the present invention. Figure 2 This is a schematic diagram of the three-dimensional vector aerospace transient electromagnetic receiving antenna structure with a square coil and a cubic structure according to the present invention. Figure 3 This is a schematic diagram of the transient process and timing acquisition window for the transient electromagnetic method.

[0015] Reference numerals: 1. Transient electromagnetic receiving coil; 2. Inertial navigation sensor. Detailed Implementation

[0016] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0017] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," "outer," "front end," "rear end," "both ends," "one end," and "the other end," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0018] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed," "equipped with," "connected," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] refer to Figure 1 and Figure 2 The three-dimensional vector airborne transient electromagnetic receiving antenna structure provided in this embodiment includes a three-dimensional vector receiving antenna body, an inertial navigation sensor, and a data acquisition module. The three-dimensional vector receiving antenna body includes three transient electromagnetic receiving coils 1 of identical specifications, which are orthogonally arranged along the XYZ three-dimensional spatial directions. The inertial navigation sensor 2 is mounted at the center, top center, or bottom center of the three-dimensional vector receiving antenna. The three-axis coordinate system of the inertial navigation sensor 2 is coaxially aligned with the XYZ three-axis coordinate system of the three transient electromagnetic receiving coils. The inertial navigation sensor 2 employs a high-precision MEMS integrated navigation module, integrating a three-axis magnetic field sensor, a three-axis accelerometer, and a three-axis angular velocity sensor. The measurement accuracy of the three-axis magnetic field sensor is ≤1nT, the resolution of the three-axis accelerometer is ≤50μg, and the zero-bias stability of the three-axis angular velocity sensor is ≤5° / h. The parallelism error between the three-axis coordinate system of the inertial navigation sensor 2 and the corresponding axes of the three receiving coils is ≤0.05°, and the coincidence error of the coordinate system origin is ≤0.02mm. The XYZ three-axis coordinate systems are completely coaxially aligned with a coaxiality error of ≤0.05°. After installation, epoxy resin is used for potting and fixation to prevent coaxiality deviation caused by loosening during flight.

[0021] The data acquisition module is electrically connected to the three transient electromagnetic receiving coils 1 and the inertial navigation sensor 2, respectively, to synchronously acquire the transient electromagnetic field signals output by the three transient electromagnetic receiving coils 1 and the full inertial navigation data output by the inertial navigation sensor 2. The data acquisition module has a built-in timing control unit, which is synchronized with the timing of the aerospace transient electromagnetic launch system to distinguish the power-on and power-off cycles of the TEM signal, avoiding acquisition windows at the rising edge of conduction and the falling edge of power-off. The data acquisition module uses an 8-channel synchronous acquisition card, electrically connected to the three transient electromagnetic receiving coils 1 and the inertial navigation sensor 2, respectively. The acquisition card has a built-in 24-bit ADC, with a maximum single-channel sampling rate of 2MHz, meeting the high-speed acquisition requirements of weak transient electromagnetic signals. The data acquisition module also has a built-in FPGA timing control unit, which is connected to the main control unit of the aerospace transient electromagnetic launch system through a synchronous trigger interface, achieving complete timing synchronization with the launch system and accurately distinguishing the power-on and power-off cycles of the TEM signal. Figure 3 As shown, a shielding window of 50-100μs is set for the rising edge of conduction and the falling edge of shutdown to avoid data acquisition during periods of strong electromagnetic interference. The electromagnetic field strength data and the attitude data of the inertial navigation sensor are acquired at the same frequency and with synchronized start phase, and the time synchronization accuracy is ≤1μs. The FPGA timing control unit outputs a source trigger signal to synchronously trigger the ADC acquisition and IMU data output, ensuring a one-to-one correspondence between timestamps.

[0022] like Figure 1 As shown, the transient electromagnetic receiving coil 1 is a circular coil with a diameter of 60cm and 50 turns. After the three circular coils are arranged orthogonally, the antenna body has an overall spherical structure.

[0023] like Figure 2As shown, the transient electromagnetic receiving coil 1 is square with a side length of 60cm and 50 turns. It is wound with 0.1mm multi-strand enameled wire. The three receiving coils are orthogonally arranged along the XYZ axes, and the planes of each pair of coils are perpendicular to each other. The orthogonality accuracy error is ≤0.1°. After the three square coils are orthogonally arranged, the antenna body has a cubic structure.

[0024] This invention also discloses a three-dimensional vector aeronautical transient electromagnetic vector correction method, based on a three-dimensional vector aeronautical transient electromagnetic receiving antenna structure, specifically including the following steps: S1. System Initialization and Parameter Calibration This step is completed before each aerial reconnaissance flight and specifically includes: Antenna and sensor installation and calibration: The orthogonality accuracy of the three receiving coils is calibrated using a theodolite to ensure that the three-axis orthogonality error is ≤0.1°; the coaxiality of the inertial navigation sensor and the coils is calibrated using a hexahedral non-magnetic calibration fixture to ensure that the coaxiality error is ≤0.05°, and the installation is confirmed to be firm and without looseness.

[0025] Sensor parameter static calibration: The antenna body was placed in a horizontal, non-magnetic interference environment, and static data acquisition was performed for 10 minutes to calculate the initial deviation of the gyroscope's three axes. Accelerometer zero bias, magnetometer zero bias and scale coefficient; calibrate the azimuth deviation of the magnetometer in a standard magnetic field environment to ensure that the geomagnetic field measurement accuracy is ≤1nT, and enter all calibration parameters into the processing unit of the data acquisition module.

[0026] EKF (Extended Kalman Filter) algorithm parameter initialization: Set the initial value of the state vector Typically, the initial attitude is horizontal due north, therefore The initial deviation of the gyroscope's three axes uses the static calibration value; Initialize the covariance matrix ; Set the process noise covariance matrix and observation noise covariance matrix .

[0027] Reference coordinate system settings: The default reference coordinate system is a true north horizontal standard reference coordinate system, with the X-axis pointing to geographic true north, the Y-axis pointing to geographic true east, and the Z-axis perpendicular to the ground downwards. This embodiment does not require a custom reference and uses the default coordinate system. If users have special requirements, they should enter the rotation angle parameters of the custom reference in advance to ensure flexible switching later.

[0028] S2. Synchronous Data Acquisition: During flight exploration, the data acquisition module maintains strict synchronization with the launch system through the timing control unit, executing the following acquisition strategy: 1. Timing window settings: Strictly distinguish between the power supply cycle and the shutdown cycle of the TEM signal, avoiding the periods of the rising edge of conduction (the instant of power supply start-up) and the falling edge of shutdown (the instant of power supply stop-up) (usually avoiding 50-100μs each, adjusted according to the shutdown speed of the transmission current). Specifically, the period of the TEM transmission signal is 25ms, of which the power supply cycle is 12.5ms and the shutdown cycle is 12.5ms; set a shielding window of 100μs for the rising edge of conduction and the falling edge of shutdown, and only collect data during the stable field establishment period of the power supply cycle and the secondary field recording period of the shutdown cycle; 2. Synchronous Acquisition Rules: Throughout the entire TEM (Transient Electromagnetic) signal power-on cycle, the inertial navigation sensor continuously acquires all data, including three-axis magnetic field, three-axis acceleration, and three-axis angular velocity data, at a frequency of 2MHz. After the shielding window of the TEM signal off cycle ends, the transient electromagnetic field intensity data of the three receiving coils XYZ and the inertial navigation full data are acquired synchronously, at a frequency of 2MHz and a resolution of 24bit, ensuring that the electromagnetic field data and the inertial navigation data acquisition start phase are completely synchronized and the timestamps correspond one-to-one.

[0029] S3. Antenna attitude calculation based on EKF (Extended Kalman Filter, EKF) algorithm: Using quaternions and gyroscope deviation as state vectors and accelerometer and magnetometer measurements as observation vectors, the optimal attitude quaternion of the antenna at the current moment is calculated in real time through the prediction and update steps of the EKF algorithm. For each set of synchronously acquired inertial navigation data, EKF attitude calculation is performed in real time. The calculation step size is consistent with the inertial navigation data acquisition period, which is 100μs. The specific steps are as follows: Define a state vector and an observation vector, with the quaternion and gyroscope bias as the state vector, and the measurements from the accelerometer and magnetometer as the observation vector: The state vector is ,in, Quaternion components are used to describe the antenna's attitude (quaternions can avoid the gimbaling problem of Euler angles and improve the accuracy of attitude calculation), among which... Real part, This is the imaginary component, corresponding to the XYZ axes; This is the deviation of the gyroscope in the XYZ directions, used to compensate for gyroscope measurement errors and improve the accuracy of attitude estimation; The observation vector is ;in, These are the measurements taken by the accelerometer in the X, Y, and Z directions, typically in units of 1. It is used to assist in attitude calculation (such as combining the gravity vector to determine the horizontal attitude). These are the measurements taken by the magnetometer (a triaxial magnetic field sensor) in the XYZ directions, usually in nT, and are used to help determine the azimuth of the antenna (such as determining true north by combining the geomagnetic field vector).

[0030] The prediction steps of the EKF algorithm include : S311. Calculate the actual angular velocity: ;in, It is the original measurement value of the gyroscope at time k; It is the gyroscope bias estimated at time k-1; subtract the gyroscope bias estimated at the previous time to compensate for the gyroscope error; S312, State Prediction: Through the state transition function Based on the state estimate at time k-1 and current actual angular velocity Calculate the state prediction value at time k. : Update quaternions: via state transition function (Using the Runge-Kutta integration method, with the integration step size consistent with the acquisition period), predict the current quaternion based on the quaternion from the previous moment and the current actual angular velocity. ; S313, Covariance Prediction: Calculate the predicted covariance value at time k. : ;in, It is the state transition matrix at time k. It is the state covariance matrix at time k-1; the uncertainty of updating the state estimate.

[0031] The update steps of the EKF algorithm include: S321. Calculate theoretical observations: using the observation function. Based on the predicted state vector Calculate the theoretical observations of the accelerometer and magnetometer. ; ; S322, Calculate measurement residuals Compare the deviations between actual and theoretical observations; therefore, ;in, It is the observation vector at time k; It is the observation function; S323. Calculate the observation Jacobian matrix. : ; S324, Calculate the innovation covariance matrix : ; S325, Calculate Kalman gain : ; S326, Update the covariance matrix : ,in It is the identity matrix; S327, Update the state estimation matrix : ; Obtain the optimal pose quaternion at the current moment. and gyroscope deviation ; Attitude calculation: Quaternions are converted into Euler angles (pitch, roll, azimuth) to visually represent the antenna attitude. The conversion formula is as follows: .

[0032] S4. Electromagnetic field strength rotation correction: After normalizing the electromagnetic field strength of the antenna's own coordinate system, it is converted into a quaternion expression. Based on the attitude quaternion obtained in step S3, a rotation matrix is ​​constructed. The electromagnetic field strength is transformed to the standard reference coordinate system through coordinate system rotation to obtain the corrected standard electromagnetic field strength data. S41. Let the scalar value of the triaxial transient electromagnetic field intensity collected in the XYZ rectangular coordinate system be... The unit is usually V / m or nT; its corresponding quaternion expression is: ; These are the real and imaginary parts of the electromagnetic field quaternion; they are proportional to the scalar value of the electromagnetic field strength, and rotational accuracy is ensured through normalization. Data collected during the shutdown cycle Normalization is performed to ensure that the amplitude of the electromagnetic field intensity remains unchanged after rotation; the electromagnetic field quaternion is calculated. The components: ; quaternion modulus: ; After quaternion rotation, the components of the electromagnetic field on the standard coordinate axis (north horizontal reference) are:

[0033] This represents the electromagnetic field strength components after transformation to the true north horizontal reference coordinate system, i.e., the corrected standard electromagnetic field strength values; This represents the imaginary component of the quaternion after attitude rotation (linked to the antenna attitude quaternion and determined by the attitude quaternion output by the EKF algorithm).

[0034] S42. Construction of the attitude rotation matrix: Based on the attitude quaternions output by the EKF algorithm. Construct rotation matrix (Used to transform the antenna's own coordinate system to the true north horizontal reference coordinate system): ; S43. Electromagnetic field strength correction: Correcting the electromagnetic field strength vector in the antenna's own coordinate system. With rotation matrix Multiplying them yields the corrected electromagnetic field strength in the standard reference coordinate system. : .

[0035] S5. Verification and Output of Corrected Data: Verify the validity of the corrected electromagnetic field strength data, mark abnormal data, output the corrected data in real time, and store the original acquired data and the corrected data.

[0036] Data verification: Verify the validity of the corrected electromagnetic field strength data and calculate the deviation before and after correction (if the attitude change is large, the corrected data should tend to be stable); if the deviation exceeds the preset threshold (e.g., ≥5%), it is marked as abnormal data, and problems with sensor installation, data acquisition or algorithm parameters are investigated.

[0037] Data output: Real-time output of corrected electromagnetic field strength data (north-oriented horizontal reference or custom reference), while storing the original data and corrected data for subsequent error analysis, algorithm optimization and result backtracking.

[0038] The method in this embodiment avoids the gimbal lock problem by using quaternion EKF attitude calculation. Combined with strict synchronous acquisition and timing shielding, it effectively avoids electromagnetic interference from the transmission system, eliminates electromagnetic field data distortion caused by antenna attitude changes, reduces the relative error of the corrected data, and significantly improves the data accuracy and imaging effect of airborne transient electromagnetic 3D exploration.

[0039] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific structures and characteristics of the solutions is not described in detail here. It will be apparent to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the present invention is defined by the appended claims rather than the foregoing description. Therefore, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A three-dimensional vector airborne transient electromagnetic receiving antenna structure, characterized in that, It includes a three-dimensional vector receiving antenna body, an inertial navigation sensor (2) and a data acquisition module; the three-dimensional vector receiving antenna body includes three transient electromagnetic receiving coils (1) of the same specifications, and the three transient electromagnetic receiving coils (1) are arranged orthogonally along the XYZ three-dimensional spatial direction respectively; The inertial navigation sensor (2) is installed at the body center, top center or bottom center of the three-dimensional vector receiving antenna body. The inertial navigation sensor (2) includes a three-axis magnetic field sensor, a three-axis acceleration sensor and a three-axis angular velocity sensor. The three-axis coordinate system of the inertial navigation sensor is coaxially aligned with the XYZ three-axis coordinate system of the three transient electromagnetic receiving coils. The data acquisition module is electrically connected to the three transient electromagnetic receiving coils (1) and the inertial navigation sensor (2) respectively, and is used to synchronously acquire the transient electromagnetic field signals output by the three transient electromagnetic receiving coils (1) and the full amount of inertial navigation data output by the inertial navigation sensor (2).

2. The three-dimensional vector airborne transient electromagnetic receiving antenna structure according to claim 1, characterized in that, The transient electromagnetic receiving coil (1) is a circular coil. After the three circular coils are arranged orthogonally, the outer contour of the three-dimensional vector receiving antenna body is spherical.

3. The three-dimensional vector airborne transient electromagnetic receiving antenna structure according to claim 1, characterized in that, The transient electromagnetic receiving coil (1) is a square coil. After the three square coils are arranged orthogonally, the outer contour of the three-dimensional vector receiving antenna body is a cubic structure.

4. The three-dimensional vector airborne transient electromagnetic receiving antenna structure according to claim 2 or 3, characterized in that, The orthogonality error of the XYZ axes of the receiving coil is ≤0.1°, the parallelism error between the corresponding axes of the inertial navigation sensor and the receiving coil is ≤0.05°, and the coincidence error of the coordinate system origin is ≤0.02mm.

5. The three-dimensional vector airborne transient electromagnetic receiving antenna structure according to claim 4, characterized in that, The data acquisition module has a built-in timing control unit, which is synchronized with the timing of the aviation transient electromagnetic launch system. It is used to distinguish between the power supply cycle and the shutdown cycle of the TEM signal and avoid the acquisition window of the rising edge of the turn-on and the falling edge of the shutdown.

6. A three-dimensional vector aeronautical transient electromagnetic vector correction method, based on the three-dimensional vector aeronautical transient electromagnetic receiving antenna structure of claim 5, characterized in that, Includes the following steps: S1. System initialization and parameter calibration: Complete the installation and calibration of the antenna and sensor, static calibration of the inertial navigation sensor, initialization of EKF algorithm parameters and setting of the reference coordinate system; S2. Synchronous Data Acquisition: Through timing control, during the stable phases of the power supply and shutdown cycles of the aviation transient electromagnetic signal, the electromagnetic field strength data of the three-axis orthogonal coil and the full attitude data of the inertial navigation sensor are synchronously acquired. The acquisition process shields the strong interference periods during the rising edge of conduction and the falling edge of shutdown, and no acquisition window is set during these periods. S3. Antenna attitude calculation based on EKF algorithm: Using quaternions and gyroscope deviation as state vectors and accelerometer and magnetometer measurements as observation vectors, the optimal attitude quaternion of the antenna at the current moment is calculated in real time through the prediction and update steps of the EKF algorithm. S4. Electromagnetic field strength rotation correction: After normalizing the electromagnetic field strength of the antenna's own coordinate system, it is converted into a quaternion expression. Based on the attitude quaternion obtained in step S3, a rotation matrix is ​​constructed. The electromagnetic field strength is transformed to the standard reference coordinate system through coordinate system rotation to obtain the corrected standard electromagnetic field strength data. S5. Verification and Output of Corrected Data: Verify the validity of the corrected electromagnetic field strength data, mark abnormal data, output the corrected data in real time, and store the original acquired data and the corrected data.

7. The vector correction method according to claim 6, characterized in that, The initialization of the EKF algorithm parameters includes: S11, Set the initial value of the state vector : ;in, When the initial components of the quaternion are horizontal true north, the initial orientation is horizontal. The initial triaxial deviation of the triaxial angular velocity sensor; S12. Initialize the covariance matrix : ;in, Let be the initial variance of the quaternion components. This represents the initial variance of the gyroscope bias. S13. Set the process noise covariance matrix and the observation noise covariance matrix.

8. The vector correction method according to claim 6, characterized in that, In step S2, the strong interference period is 50-100μs for both the rising edge of conduction and the falling edge of turn-off; the electromagnetic field strength data during the turn-off period is acquired using a high-speed acquisition circuit with an acquisition frequency ≥1MHz and a resolution ≥24bit. The electromagnetic field strength data is acquired at the same frequency as the attitude data of the inertial navigation sensor, and the acquisition start phase is synchronized with the time synchronization accuracy ≤1μs.

9. The vector correction method according to claim 6, characterized in that, In step S3, the prediction step of the EKF algorithm includes: S311, Calculate the actual angular velocity : ;in, It is the original measurement value of the gyroscope at time k; It is the gyroscope bias estimated at time k-1; S312, State Prediction: Through the state transition function Based on the state estimate at time k-1 and current actual angular velocity Calculate the state prediction value at time k. : ； S313, Covariance Prediction: Calculate the predicted covariance value at time k. : ;in, It is the state transition matrix at time k. It is the state covariance matrix at time k-1; The update steps of the EKF algorithm include: S321. Calculate theoretical observations: using the observation function. Based on the predicted state vector Calculate the theoretical observations of the accelerometer and magnetometer. ; ; S322. Calculate the measurement residuals: ;in, It is the observation vector at time k; It is the observation function; comparing the deviation between the actual observed values ​​and the theoretical observed values; S323. Calculate the observation Jacobian matrix. : ; S324, Calculate the innovation covariance matrix : ; S325, Calculate Kalman gain : ; S326, Update the covariance matrix : ,in It is the identity matrix; S327, Update the state estimation matrix : ; Obtain the optimal pose quaternion at the current moment. and gyroscope deviation .

10. The vector correction method according to claim 6, characterized in that, Step S4 specifically includes: S41. Let the scalar value of the triaxial transient electromagnetic field intensity collected in the XYZ rectangular coordinate system be... Its corresponding quaternion expression is: ; These are the real and imaginary parts of the electromagnetic quaternion; data collected during the turn-off period. Normalization is performed to calculate the electromagnetic quaternion. The components: ； quaternion modulus: ; After quaternion rotation, the components of the electromagnetic field on the standard coordinate axes are: ； This represents the electromagnetic field strength components after transformation to the true north horizontal reference coordinate system, i.e., the corrected standard electromagnetic field strength value. Represents the imaginary part of the quaternion after attitude rotation; S42. Construction of the attitude rotation matrix: Based on the attitude quaternions output by the EKF algorithm. Construct rotation matrix : ； S43. Electromagnetic field strength correction: Correcting the electromagnetic field strength vector in the antenna's own coordinate system. With rotation matrix Multiplying them yields the corrected electromagnetic field strength in the standard reference coordinate system. ;Right now: .

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