Aircraft attitude measurement method based on apparent acceleration coordinate system registration

Abstract

The invention relates to an aircraft attitude measurement method based on apparent acceleration coordinate system registration, which is suitable for a sensor limited or external signal interference environment. The method comprises the following steps: firstly, acquiring an apparent acceleration point set of an aircraft under a body coordinate system and an east-north-sky coordinate system, and carrying out centroid calculation and decentration processing to obtain standardized data; obtaining an optimal rotation matrix of the two coordinate systems through covariance matrix construction and singular value decomposition; and finally, the pitch angle, the yaw angle and the rolling angle of the aircraft are solved through the rotation matrix by taking Z-Y-X as a rotation sequence. The method does not depend on an external satellite signal and a high-precision inertial device, avoids the accumulative error of a traditional inertial navigation system and the anti-interference defect of a satellite navigation system, and has the advantages of high measurement precision (the error is less than or equal to + / -1 degree), high stability, wide adaptability and good engineering realizability; the method can be widely applied to attitude measurement of various aircrafts such as unmanned aerial vehicles, satellites and missiles.

Description

Technical Field

[0001] This invention relates to the field of aerospace vehicle attitude measurement technology, specifically to a vehicle attitude measurement method based on visual acceleration coordinate system registration, which can be used for vehicle attitude calculation in environments where sensors are limited or external signal interference occurs. Background Technology

[0002] In the aerospace field, attitude measurement of aircraft is one of the key technologies for achieving precise navigation, stable flight control, and completing various missions. The accuracy and reliability of attitude angle (including pitch, yaw, and roll) measurement directly determine the flight performance and mission completion quality of the aircraft.

[0003] Currently, mainstream aircraft attitude measurement methods are mainly divided into two categories: one is the measurement method based on inertial navigation systems (INS), which measures the angular and linear motion information of the aircraft through inertial devices (such as gyroscopes and accelerometers) and then calculates the attitude angles. This method is completely autonomous, unaffected by the external environment, and has high short-term measurement accuracy, but it has inherent defects: inertial devices themselves have drift errors (such as zero drift of gyroscopes and random errors of accelerometers). As the working time accumulates, the errors will continue to amplify, leading to a significant decrease in long-term measurement accuracy. Therefore, it is necessary to rely on external equipment for periodic calibration, and the entire system is expensive, which limits its application in some low-cost aircraft.

[0004] Another type of measurement method is based on Navigation Satellite Systems (GNSS). This method obtains the aircraft's position and velocity information by receiving satellite signals, and then infers the attitude angles. This method does not have accumulated errors and has good long-term stability, but it is extremely dependent on external satellite signals. In complex environments, such as signal-blocked areas like urban canyons, mountains, and forests, or environments with signal interference such as space radiation and electromagnetic interference, satellite signals are prone to interruption or distortion, leading to a sharp decline in attitude measurement accuracy or even complete failure, seriously affecting the flight safety of the aircraft.

[0005] With the rapid development of aerospace technology, the application scenarios of aircraft are becoming increasingly complex (such as low-altitude flight, deep space exploration, and operation in highly interference environments), placing higher demands on the accuracy, stability, autonomy, and anti-interference capabilities of attitude measurement. Existing measurement methods are insufficient to simultaneously meet these requirements. Therefore, there is an urgent need to develop a new aircraft attitude measurement method to solve the attitude calculation problem under conditions of sensor limitations or external signal interference. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide an aircraft attitude measurement method based on visual acceleration coordinate system registration, which is an improvement over the above-mentioned prior art. This method enables high-precision and high-stability calculation of aircraft attitude under conditions where sensors are limited or external signal interference occurs, thereby improving the autonomy and anti-interference capability of attitude measurement.

[0007] The technical solution adopted by this invention to solve the above problems is as follows: a method for measuring the attitude of an aircraft based on the registration of the apparent acceleration coordinate system. This method obtains the apparent acceleration data in the target body coordinate system and the northeast-sky coordinate system, and then accurately registers the two coordinate systems based on the above data to obtain the rotation matrix and Euler angles of the two coordinate systems. The obtained Euler angles are the three-axis attitude angles of the aircraft. The specific technical solution includes the following steps: Step 1: Obtain the set of apparent acceleration points Obtain the apparent acceleration point sets of the target aircraft in the body coordinate system and the northeast-sky coordinate system, respectively, where: The apparent acceleration point set in the body coordinate system is denoted as , This represents the number of sampling points; This represents the apparent acceleration components of the i-th sampling point along the x, y, and z axes in the body coordinate system; the set of apparent acceleration points in the northeast-northeast coordinate system is denoted as... , This represents the apparent acceleration components of the i-th sampling point in the x (east), y (north), and z (sky) axes of the northeast-sky coordinate system.

[0008] The apparent acceleration data is obtained by measuring the three-axis accelerometer on the aircraft. The sampling frequency is set according to the aircraft's flight speed and attitude change rate to ensure that the point set can completely reflect the aircraft's motion state.

[0009] Step 2: Centroid Calculation and Decentralization To eliminate the impact of coordinate system origin offset on registration accuracy, centroid calculation and centering were performed on the two sets of apparent acceleration point sets respectively: 1. Calculate the centroid of the apparent acceleration point set in the northeast-northeast coordinate system. : ; 2. Calculate the centroid of the apparent acceleration point set in the body coordinate system. : ; 3. Decentralize the point set of the northeast-central coordinate system to obtain... : ; 4. Decentralize the point set of the body coordinate system to obtain... : .

[0010] Step 3: Calculate the covariance matrix H Based on the decentralized view acceleration point set Calculate the covariance matrix H between the two coordinate systems to characterize the correlation between the two sets of data: ; in, express The transpose of .

[0011] Step 4: Singular Value Decomposition (SVD) Singular value decomposition is performed on the covariance matrix H, and the decomposition form is as follows: ; Where U and V are orthogonal matrices. It is a singular value diagonal matrix. and It is an orthogonal matrix whose diagonal elements are singular values ​​of the covariance matrix H, and satisfy the following conditions: .

[0012] Step 5: Construct the optimal rotation matrix R Based on the singular value decomposition results, the optimal rotation matrix R between the body coordinate system and the northeast coordinate system is constructed to achieve accurate registration of the two coordinate systems: ; in, Representation matrix The determinant of the matrix R is used to ensure the orthogonality of the rotation matrix R and the consistency of the right-hand rule; its value is ±1. The transpose of .

[0013] Step 6: Calculate the aircraft's attitude angles by To determine the rotation sequence (yaw around the Z-axis, pitch around the Y-axis, and roll around the X-axis), Euler angles are calculated using the rotation matrix R. These Euler angles represent the aircraft's three-axis attitude angles. 1. Pitch angle : ; 2. Yaw angle : ; 3. Roll angle : ; in, This represents the element in the i-th row and j-th column of the rotation matrix R.

[0014] Compared with the prior art, the present invention has the following beneficial effects: This invention performs coordinate system registration on the target's apparent acceleration in the northeast-northeast coordinate system and the body coordinate system, calculates the rotation matrix of the two coordinate systems, and then calculates the Euler angles, that is, the target attitude angles.

[0015] The apparent acceleration-based measurement method proposed in this invention has significant theoretical advantages in terms of accuracy, stability, and anti-interference capabilities. Regarding accuracy, traditional inertial navigation systems suffer from inherent errors in inertial devices, such as gyroscope drift errors, which accumulate over time, leading to a continuous increase in attitude measurement errors. The apparent acceleration-based method, through precise analysis and processing of Earth's gravitational acceleration and the actual acceleration of the aircraft, effectively reduces the impact of these accumulated errors, improving the accuracy of attitude measurement. Regarding stability, satellite navigation systems are susceptible to signal blockage and interference, leading to interruptions or decreased accuracy in attitude measurement. The apparent acceleration-based method, however, does not rely on external satellite signals, exhibiting greater autonomy and stability. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the apparent acceleration data of the target in the northeast-central coordinate system.

[0017] Figure 2 This is a schematic diagram of the apparent acceleration data of the target in the body coordinate system.

[0018] Figure 3 This diagram illustrates the consistency between the target's apparent acceleration body coordinate system data and the calculated attitude data after transformation. Detailed Implementation

[0019] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0020] This invention provides a method for measuring the attitude of an aircraft based on visual acceleration coordinate system registration, comprising the following steps: (1) Obtain the apparent acceleration data of the aircraft in the northeast-sky coordinate system. Obtain the apparent acceleration data of the target's body coordinate system. .

[0021] (2) Calculate the centroids of the point sets of apparent acceleration data in the northeast-sky coordinate system and apparent acceleration data in the body coordinate system respectively, and then perform decentering processing: ; (3) Calculate the covariance matrix H: ; (4) Perform singular value decomposition on the covariance matrix: ; Where U and V are orthogonal matrices. It is a singular value diagonal matrix.

[0022] (5) Solve for the rotation matrix, i.e., construct the optimal rotation matrix R using the singular value decomposition results: ; (6) By rotation matrix Calculate Euler angles ( (Rotation sequence), also known as the target flight attitude angles: pitch angle Yaw angle Roll angle .

[0023] To better demonstrate the implementation steps of this invention, we have selected a section of measured data from an aircraft as an example. Figure 1 The image shows the downward-looking acceleration data in the northeast-sky coordinate system. Figure 2 The apparent acceleration data in the target body coordinate system is shown in Table 1.

[0024] Table 1 Test Data

[0025] According to the method described in this invention, coordinate system registration is performed on the two sets of apparent acceleration parameters, and after decentering, the covariance matrix H is obtained: ; After performing singular value decomposition, the rotation matrix R is obtained: ; By rotation matrix Calculate Euler angles ( (Rotation sequence), also known as the target flight attitude angles: pitch angle Yaw angle Roll angle To further verify this, the axial, normal, and lateral components of the apparent acceleration were transformed to the northeast-sky coordinate system according to the calculated attitude. The transformation results are shown below. Figure 3 It can be seen that the results of attitude transformation are consistent with the data directly transmitted by telemetry, and the two sets of data curves are completely consistent in detail, thus proving that the attitude parameter calculation and analysis are correct.

[0026] In addition to the above embodiments, the present invention also includes other embodiments. All technical solutions formed by equivalent transformation or equivalent substitution should fall within the protection scope of the claims of the present invention.

Claims

1. A method for measuring the attitude of an aircraft based on registration with an apparent acceleration coordinate system, characterized in that, The method includes the following steps: Step 1: Obtain the apparent acceleration point sets of the aircraft in the body coordinate system and the northeast-sky coordinate system, respectively, denoted as: The apparent acceleration point set in the body coordinate system is denoted as The apparent acceleration point set in the northeast-sky coordinate system is denoted as , which indicates , These are the apparent acceleration components at the i-th sampling time in the two coordinate systems, respectively. The number of sampling points and ; Step 2: Calculate the centroids of the two point sets and perform centering: ； ； in , Let be the centroid vectors of the apparent acceleration point sets in the two coordinate systems, respectively. , These are the decentralized view acceleration vectors; Step 3: Calculate the covariance matrix of the apparent acceleration point sets in the two coordinate systems. ,in express The transpose of the matrix; Step 4: Adjust the covariance matrix Perform singular value decomposition, the decomposition form is: ； in , It is an orthogonal matrix. It is a singular value diagonal matrix; Step 5: Construct the optimal rotation matrix based on the singular value decomposition results: ； in, Representation matrix The determinant of is The transpose of the matrix; Step 6: with To determine the rotation order, Euler angles are calculated using the rotation matrix R. These Euler angles represent the three-axis attitude angles of the aircraft. Pitch angle Yaw angle Roll angle , in, This represents the element in the i-th row and j-th column of the rotation matrix R.

2. The method for measuring aircraft attitude based on visual acceleration coordinate system registration according to claim 1, characterized in that, The apparent acceleration data mentioned in step 1 is acquired through an accelerometer, which is a triaxial accelerometer, a piezoelectric accelerometer, or a fiber optic accelerometer.

3. The aircraft attitude measurement method based on visual acceleration coordinate system registration according to claim 1, characterized in that, In step 1 This is to improve the accuracy of coordinate system registration.

4. The method for measuring aircraft attitude based on visual acceleration coordinate system registration according to claim 1, characterized in that, The process includes attitude angle calibration steps: comparing the attitude angles obtained in step 6 with the reference attitude data, calculating the error correction coefficients, and calibrating the pitch angle, yaw angle, and roll angle.

5. The method for measuring aircraft attitude based on visual acceleration coordinate system registration according to claim 1, characterized in that, The aircraft can be a drone, satellite, rocket, or manned aircraft.

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