Target direction finding error calculation method based on near-seabed horizontal array look-up detection

Abstract

The invention relates to a target direction finding error calculation method based on near-seabed horizontal array look-up detection, and the method comprises the following steps: 1, calculating the relation between a pitch angle and an azimuth angle of a target; 2, calculating the mean square error of the pitch angle and the space arrival angle; and step 3, calculating the mean square error of the horizontal chord angle. For the quantization problem of the precision of the look-up detection direction, the measurement precision of the horizontal chord angle is calculated by using the existing measurable precision of the pitch angle and the azimuth arrival angle on the basis of the error transfer theory, so that the precision of the look-up detection direction is obtained, the accuracy of target detection is actually improved, and the method has remarkable engineering implementation value.

Description

Technical field:

[0001] The invention belongs to the technical field of underwater acoustic engineering, and in particular relates to a method for calculating target direction finding errors based on upward-looking detection by a near-seabed horizontal array. Background technology:

[0002] The advantage of vertical line array (VLA) as a receiving array is that VLA can collect more sound propagation information at depth, and locate the target by measuring the pitch angle of the target and the multipath delay caused by the channel. Its disadvantage is that vertical line array is easily affected by the environment such as ocean currents and internal waves, and inherent characteristics such as array tilt limit its performance and application. Horizontal line array can obtain information on the marine environment parameters around the array through long-term marine environment surveys, and continuously optimize parameters, thereby avoiding errors caused by environmental mismatch to a certain extent. At the same time, since the fixed horizontal array on the seabed can estimate the direction of the target in the horizontal space, the combination of algorithms can effectively achieve the positioning of the target.

[0003] At present, the mainstream acoustic measurement arrays in China generally only use horizontal arrays or vertical arrays, and there are more positioning studies based on vertical arrays, while there are still fewer positioning technologies based on horizontal arrays. In 1972, Hinich matched the data measured by the vertical array with the data calculated by the simple normal wave model, and derived the Cramer-Rao bound to estimate the distance. Based on Hinich's research, Bucker developed the Bartlett matching processor and quadratic detection estimator, which are currently widely used and have simple algorithms and fast operation speed. He matched the data measured by the vertical array with the copy field data obtained by model simulation, constructed a correlation function, and used the square of the amplitude of the correlation function to estimate the distance and depth of the sound source, and constructed a fuzzy surface map. Booth analyzed the data results of vertical arrays, inclined arrays and seabed horizontal arrays in the SWellEX series of experiments, and proposed an adiabatic simple normal wave model. After comparing it with the actual matching field results, it was found that the consistency was very high. As far as China is concerned, Li Fenghua and others have preliminarily studied the horizontal array matching field positioning method, and analyzed the influence of parameters such as horizontal array length and array element spacing on the positioning effect. Chen Yu et al. found that large-aperture horizontal time-reversal arrays have better focusing performance, and narrowband signals can improve time-reversal focusing performance. Wang Qi et al. proposed a fast matching field passive positioning algorithm, and verified the effectiveness of the algorithm through simulation experiments, and it has the advantage of small computational complexity. Then, two optimized feature extraction matching field processors were constructed to achieve the positioning of fixed sound sources and moving sound sources.

[0004] The upward-looking detection array consists of a horizontal array and a vertical array, which can locate the target more accurately. At the same time, it also brings up the problem that the measurement azimuth accuracy is affected by the pitch angle accuracy and azimuth arrival angle accuracy of the two arrays. Summary of the invention:

[0005] The technical problem to be solved by the present invention is to provide a method for calculating target direction finding error based on upward-looking detection by a near-seabed horizontal array. The method is based on the error transfer theory and utilizes the measurable accuracy of the existing pitch angle and azimuth arrival angle to calculate the measurement accuracy of the horizontal chord angle, thereby obtaining the upward-looking detection direction accuracy, thereby actually improving the accuracy of target detection and having significant engineering realization value.

[0006] The technical solution of the present invention is to provide a method for calculating target direction finding error based on near-seabed horizontal array upward detection, comprising the following steps:

[0007] Step 1, calculate the relationship between the pitch angle and azimuth angle of the target;

[0008] Step 2, calculate the mean square error of the pitch angle and the spatial arrival angle;

[0009] Step 3: Calculate the mean square error of the horizontal chord angle; where:

[0010] In step 1, the relationship between the target's elevation angle and azimuth angle can be expressed as:

[0011]

[0012] in is the true pitch angle measured by the vertical array, θ is the horizontal chord angle, and α is the spatial arrival angle measured by the horizontal array;

[0013] In step 2, set the -3dB beamwidth,

[0014]

[0015] Where, c is the reference sound velocity, f0 is the center frequency, and L is the array length;

[0016] Direction finding standard deviation

[0017] The specific operation of step 3 is as follows:

[0018] θ=arccos(x) (4)

[0019] According to the transmission error, we have

[0020]

[0021] Will Substitute into equation (5) and simplify, and we get

[0022]

[0023] Except In addition to being related to the target, it is also related to the azimuth and elevation angle of the target. When smaller, obviously larger; when When smaller, obviously Smaller.

[0024] Preferably, in step 2, with a horizontal aperture of 6 m, a -3dB beam width of 2.1 degrees, and stable tracking conditions, the output signal-to-noise ratio of the horizontal receiving array and the vertical receiving array is 3dB, the mean square error of the elevation angle measurement is 1.5 degrees, and the mean square error of the spatial angle measurement is 1.5 degrees.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] The present invention proposes a method for calculating target direction-finding error based on near-seabed horizontal array upward detection. When the upward detection array (composed of a horizontal array and a vertical array) is used to locate the target, the horizontal chord angle is obtained by measuring the pitch angle and azimuth arrival angle of the bottom-mounted upward detection array. Any device has measurement errors, so lateral errors caused by sensor accuracy are inevitable. For the quantification of the upward detection direction accuracy, the present invention, based on the error transfer theory, uses the existing measurable accuracy of the pitch angle and azimuth arrival angle to calculate the measurement accuracy of the horizontal chord angle, and then obtains the upward detection direction accuracy, which actually improves the accuracy of target detection and has significant engineering implementation value. Description of the drawings:

[0027] Figure 1 A calculation flow chart of a target direction finding error calculation method based on upward-looking detection by a near-seabed horizontal array is given.

[0028] Figure 2 Schematic diagram of the relationship between pitch angle, spatial arrival angle and horizontal chord angle.

[0029] Figure 3 The influence of the pitch angle and the spatial arrival angle on the mean square error of the horizontal chord angle is given.

[0030] Figure 4 The influence of the pitch angle on the mean square error of the horizontal chord angle is given when the spatial arrival angles are 15°, 30°, 45°, 60°, 75° and 90° respectively.

[0031] Figure 5 The influence of the pitch angle azimuth arrival angle on the mean square error of the horizontal chord angle is given when the pitch angles are 15°, 30°, 45°, 60°, 75° and 90° respectively. Specific implementation method:

[0032] The present invention will be further described below with reference to the accompanying drawings:

[0033] A target direction finding error calculation method based on near-seabed horizontal array upward detection, such as Figure 1 , including the following steps,

[0034] (1) Calculate the relationship between the target's pitch angle and azimuth angle

[0035] The pitch angle of arrival of the acoustic signal is determined by the time delay difference between the two and the channel fluctuation. The channel fluctuation and time delay difference measurement accuracy determines the true pitch angle accuracy. Therefore, the accuracy of the target's chord angle is jointly determined by the spatial arrival angle α measurement accuracy, the pitch angle measurement accuracy and the channel fluctuation.

[0036] The relationship between the target's elevation angle and azimuth angle can be expressed as:

[0037]

[0038] in is the true pitch angle measured by the vertical array, θ is the horizontal chord angle, and α is the spatial arrival angle measured by the horizontal array.

[0039] (2) Calculate the mean square error of the pitch angle and the spatial arrival angle

[0040] Assume -3dB beam width,

[0041]

[0042] Where c is the reference sound velocity, f0 is the center frequency, and L is the array length. When the horizontal aperture is 6m, the -3dB beamwidth is 2.1 degrees.

[0043] Under stable tracking conditions, the output signal-to-noise ratio of the horizontal receiving array and the vertical receiving array is 3dB, the mean square error of the pitch angle measurement is 1.5 degrees, and the mean square error of the spatial angle measurement is 1.5 degrees.

[0044] (3) Calculate the mean square error of the horizontal chord angle

[0045] make

[0046] θ=arccos(x) (4)

[0047] According to the transmission error, we have

[0048]

[0049] Will Substitute into the above formula and simplify, we get

[0050]

[0051] Except In addition to being related to the target, it is also related to the azimuth and elevation angle of the target. When smaller, obviously larger; when When smaller, obviously Smaller.

[0052] Figure 2 It is a schematic diagram of the relationship between the pitch angle, the spatial arrival angle and the horizontal chord angle. According to the trigonometric relationship shown in the figure, it can be obtained that the cosine value of the horizontal chord angle = the cosine value of the pitch angle × the cosine value of the spatial arrival angle.

[0053] Figure 3 The influence of the pitch angle and the spatial arrival angle on the mean square error of the horizontal chord angle is given, where the horizontal axis represents the change of the horizontal chord angle accuracy with the mean square error of the spatial arrival angle, and the vertical axis represents the change of the horizontal chord angle accuracy with the mean square error of the pitch angle. It can be clearly seen in the figure that for the horizontal chord angle accuracy, the measurement error in the horizontal direction of the horizontal array is the largest, and the measurement error in the direction perpendicular to the horizontal array is the smallest.

[0054] Figure 4 The influence of the pitch angle on the mean square error of the horizontal chord angle when the spatial arrival angle of this embodiment is 15°, 30°, 45°, 60°, 75°, and 90° respectively is given. It can be clearly seen from the figure that for the horizontal chord angle accuracy, the larger the angle between the target direction and the horizontal array, the slower the direction finding error increases with the increase of the pitch angle. At the same time, Figure 5 The influence of the pitch angle azimuth arrival angle on the mean square error of the horizontal chord angle is given when the pitch angles are 15°, 30°, 45°, 60°, 75°, and 90°. For the accuracy of the horizontal chord angle, the smaller the pitch angle, that is, the closer the target is to the array, the smaller the error.

[0055] Regarding the quantification problem of the upward-looking detection direction accuracy, the present invention is based on the error propagation theory and utilizes the existing measurable accuracy of the pitch angle and azimuth arrival angle to calculate the measurement accuracy of the horizontal chord angle, and then obtains the upward-looking detection direction accuracy, which actually improves the accuracy of target detection and has significant engineering implementation value.

[0056] The above is only an explanation of the preferred embodiments of the present invention, which should not be construed as a limitation on the claims. Any equivalent process changes made using the present invention specification are included in the patent protection scope of the present invention.

Claims

1. A method for calculating target direction finding error based on near-seabed horizontal array upward detection, characterized in that: The following steps are included: Step 1, calculate the relationship between the pitch angle and azimuth angle of the target; Step 2, calculate the mean square error of the pitch angle and the spatial arrival angle; Step 3: Calculate the mean square error of the horizontal chord angle; where: In step 1, the relationship between the target's elevation angle and azimuth angle can be expressed as: in is the true pitch angle measured by the vertical array, θ is the horizontal chord angle, and α is the spatial arrival angle measured by the horizontal array; In step 2, set the -3dB beam width, Where, c is the reference sound velocity, f0 is the center frequency, and L is the array length; Direction finding standard deviation The specific operation of step 3 is as follows: θ=arccos(x) (4) According to the transmission error, we have Will Substitute into equation (5) and simplify, and we get 2. The target direction finding error calculation method based on near-seabed horizontal array upward detection according to claim 1 is characterized in that: In step 2, with a horizontal aperture of 6m, a -3dB beamwidth of 2.1 degrees, and stable tracking conditions, the output signal-to-noise ratio of the horizontal receiving array and the vertical receiving array is 3dB, the mean square error of the elevation angle measurement is 1.5 degrees, and the mean square error of the spatial angle measurement is 1.5 degrees.

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