Method for estimating the position of a target acoustic source from hydrophones on an underwater vehicle

Abstract

The application estimates the position of a target sound source according to a hydrophone on an underwater vehicle. The underwater vehicle is equipped with symmetrical first and second hydrophones on the left and right sides, and a third hydrophone on a trailing cable at the rear end of the underwater vehicle. During the travel of the underwater vehicle, the third hydrophone is located at the rear end of the underwater vehicle. The midpoint between the first and second hydrophones is F1, and the third hydrophone is F2. The line connecting F1 and F2 is the X axis. The midpoint between F1 and F2 is the coordinate origin. A straight line perpendicular to the X axis is the Y axis. The coordinates of F1 are (-a, 0), the coordinates of F2 are (a, 0), and the coordinates of the target sound source M are (x, y). The distances received by the three hydrophones form a hyperbola in the above coordinate system. According to the energy ratio received by the three hydrophones, a circular trajectory is drawn. The coordinates of the target sound source M are found in the coordinate system.

Description

Technical Field

[0001] This invention belongs to the field of signal detection and orientation estimation for self-propelled underwater vehicles. It enables underwater vehicles to detect active detection signals generated by adversarial targets in real time during navigation, identify the target type, and estimate the target's orientation in real time by comparing multiple signals. Background Technology

[0002] Current self-propelled countermeasures equipment follows a pre-set path. When it receives an active detection signal from a target, it only detects the signal parameters and generates a processed echo signal to simulate a real ship. Because the target's location is not estimated, the vehicle's own trajectory does not change due to the target's position, thus affecting the countermeasures effectiveness. Furthermore, past algorithms often required at least three receiver elements to determine the location of the sound source.

[0003] This invention addresses the current demand for intelligent self-propelled vehicles by proposing a real-time passive target location estimation method. Upon receiving an active detection signal from an adversarial target, based on parameters such as signal frequency, pulse width, and intensity, and an estimation of the target type, a dual-element positioning algorithm is proposed. This algorithm requires only two receiving hydrophones to provide a relatively accurate real-time estimate of the target's location. Summary of the Invention

[0004] The purpose of this invention is to provide a method for estimating the location of a target sound source based on hydrophones on an underwater vehicle. The main content is the passive signal detection of the underwater vehicle and the estimation of the target's orientation.

[0005] To achieve the purpose of this invention, the following technical solution is adopted:

[0006] This invention discloses a method for estimating the location of a target sound source based on hydrophones on an underwater vehicle. The underwater vehicle is equipped with symmetrical first and second hydrophones on its left and right sides respectively. A tow cable is attached to the rear of the underwater vehicle, and a third hydrophone is mounted on the tow cable. During the underwater vehicle's movement, the third hydrophone is located at the rear of the underwater vehicle. The first, second, and third hydrophones receive signals emitted by the target sound source, wherein:

[0007] Let F1 be the midpoint between the first and second hydrophones of the underwater vehicle, the distance between the first and second hydrophones be negligible, and the third hydrophone be F2. The line connecting F1 and F2 is the X-axis. Let the midpoint between F1 and F2 be the origin of the coordinate system, and let the line perpendicular to the X-axis be the Y-axis. The coordinates of F1 are (-a, 0), the coordinates of F2 are (a, 0), and the coordinates of the target sound source M are (x, y).

[0008] (i) The distances received by the three hydrophones are hyperbolic in the above coordinate system.

[0009] Because the propagation distances from the target sound source M to the third hydrophone and the second or first hydrophone are different, a time difference Δt occurs between the received signals of the second or first hydrophone and the third hydrophone. The speed of sound propagation is v, where v = 1500 m / s. Therefore, the distance from the target sound source M to the second or first hydrophone is:

[0010] The distance from the target sound source M to the third hydrophone is:

[0011] The distance difference between the target sound source M and the second hydrophone, or between the first and third hydrophones, is

[0012]

[0013] Multiply both sides of the formula achievable

[0014]

[0015] Squaring both sides of the formula and then adding them together, we get...

[0016]

[0017] Simplifying formula (5) yields...

[0018]

[0019] Pick

[0020]

[0021] Substituting a1 and b1 into the formula, we can simplify the expression to obtain...

[0022]

[0023] Plot the hyperbola equation obtained from formula (8) on the above coordinate system;

[0024] (ii) Draw a circular trajectory based on the energy ratio received by the three hydrophones.

[0025] In the space between the second hydrophone or the first and third hydrophones, the relationship between the energy intensity of the sound source signal and the distance is expressed by the following formula (9):

[0026]

[0027] Where E1 and E2 represent the energy received by the second or first hydrophone and the energy received by the third hydrophone, respectively; d1 and d2 represent the distance from the sound source to the second or first hydrophone and the distance to the third hydrophone, respectively; and θ is a random variable with zero mean. According to the above formula, if θ is 0, the ratio of distances obtained in formula (10) is obtained.

[0028]

[0029] According to Apollonius's circle theorem, the locus of points in a plane whose distances to two fixed points are in the ratio of a constant (the constant ≠ 1) is a circle. Let F1(-a,0) and F2(a,0), and the coordinates of the moving point M be (x,y). The following condition is satisfied. And k is a fixed value;

[0030]

[0031]

[0032] Combining formula (11) and formula (12), we get:

[0033]

[0034] Squaring both sides of formula (13) yields:

[0035] (xa) 2 +y 2 =k 2 ((x+a) 2 +y 2 Formula (14) is expanded and rearranged to obtain the following formula (15).

[0036]

[0037] From formula (15), it can be seen that when k>0 and k≠1, the trajectory of the moving point M is a circle. The circular equation obtained by formula (15) is drawn on the above coordinate system.

[0038] (III) Locate the coordinates of the target sound source M in the coordinate system.

[0039] On the coordinate system described above, find the intersection points M1 and M2 of the hyperbola and the circle. Based on the signal received by the second hydrophone or the signal received by the first hydrophone, delete the intersection points M1 or M2. The coordinates (x, y) of M2 or M1 obtained are the positions of the target sound source M.

[0040] The present invention provides a method for estimating the location of a target sound source based on a hydrophone on an underwater vehicle, wherein: when a second hydrophone or a first hydrophone simultaneously receives a signal from a target sound source M, only one of the second hydrophone and the first hydrophone receives the signal from the target sound source M.

[0041] The present invention provides a method for estimating the location of a target sound source based on a hydrophone on an underwater vehicle, wherein the obtained coordinates (x, y) of M2 or M1 are on the same side as the signal received by the second hydrophone or the first hydrophone.

[0042] The present invention provides a method for estimating the location of a target sound source based on a hydrophone on an underwater vehicle, wherein v = 1500 m / s.

[0043] The third hydrophone is a towed receiving hydrophone, while the first and second hydrophones are installed on the left and right sides of the product. Using a time delay difference positioning algorithm, the hyperbola L is determined by the time delay between the first or second hydrophone and the third hydrophone. Using an energy ratio positioning algorithm, a circle is determined by the energy ratio of the signals received between the first or second hydrophone and the third hydrophone. The intersection of the hyperbola and the circle is the estimated coordinate point of the target's location. However, it should be noted that, generally, the hyperbola and circle determined by the algorithm will have two intersection points, M1 and M2, meaning two sound source locations can be identified. It is necessary to pre-limit the sound source locations to a certain area to eliminate target ambiguity. In this case, the directional characteristics of the left and right hydrophones can be used to naturally eliminate erroneous intersection points, thus obtaining a unique target location.

[0044] This invention includes hardware and software design. The hardware components include: left and right hydrophones, a towed hydrophone, a preamplifier circuit, and a signal processing circuit. The software components include: preamplifier and filtering software and signal processing software, both of which are FPGA embedded software written in C and Verilog languages.

[0045] This invention receives the active detection signal emitted by the target via left, right, and towed hydrophones. The signal is then processed through preamplifier and filter circuits, undergoing preamplification, frequency equalization, and analog-to-digital conversion to become three digital signals, which are then sent to the signal processing circuit. The signal processing software detects the received three signals, determines whether the target is located on the left or right side of the product, and then uses a dual-element array composed of the available hydrophones on the left, right, and center sides, along with the towed hydrophone, to estimate the target's location using a dual-element positioning algorithm. Attached Figure Description

[0046] Figure 1 A schematic diagram showing the installation positions of each hydrophone on the vehicle and the target orientation;

[0047] Figure 2This is a schematic diagram illustrating the method of the present invention for estimating the location of a target sound source.

[0048] Figure 1 and Figure 2 These are all illustrative images; for clarity, they are not drawn to scale.

[0049] exist Figure 1 In the diagram, 1 represents the underwater vehicle; 2 represents the first hydrophone; 3 represents the second hydrophone; 4 represents the towing cable; 5 represents the third hydrophone; and 6 represents the target sound source. Detailed Implementation

[0050] like Figure 1 and Figure 2 As shown, the signals from the first hydrophone 2, the second hydrophone 3, and the third hydrophone 5 enter the preamplifier and filter circuit through the left, right, and drag hydrophones. The circuit performs signal amplification, filtering, analog-to-digital conversion, and frequency equalization. The preamplifier and filter software stores the equalization parameters calibrated for each hydrophone according to the uniform incident sound source level requirements. Therefore, the differences in individual receiving sensitivity of the hydrophones and the errors in the sound source level of the same hydrophone at different frequency points are corrected after the three signals are processed, ensuring the accuracy of the amplitude comparison of each signal during signal processing.

[0051] The underwater vehicle 1 is equipped with a first hydrophone 2 and a second hydrophone 3 on each of its left and right sides. A tow cable 4 is installed at the rear end of the underwater vehicle 1, and a third hydrophone 5 is installed on the tow cable 4. During the movement of the underwater vehicle 1, the third hydrophone 5 is located at the rear end of the underwater vehicle 1. The first hydrophone 2, the second hydrophone 3 and the third hydrophone 5 receive the signal emitted by the target sound source 6.

[0052] The method of estimating the location of a target sound source based on hydrophones on an underwater vehicle according to the present invention includes:

[0053] Let F1 be the midpoint between the first hydrophone 2 and the second hydrophone 3 of the underwater vehicle 1, the distance between the first hydrophone 2 and the second hydrophone 3 be negligible, the third hydrophone 5 be F2, the line connecting F1 and F2 be the X-axis, the midpoint between F1 and F2 be the origin of the coordinate system, and the line perpendicular to the X-axis be the Y-axis, and establish the coordinate system. The coordinates of F1 are (-a, 0), the coordinates of F2 are (a, 0), and the coordinates of the target sound source M6 are (x, y).

[0054] (i) The distances received by the three hydrophones are hyperbolic in the above coordinate system.

[0055] When the second hydrophone 3 or the first hydrophone 2 simultaneously receives the signal from the target sound source M6, only one of the two hydrophones receives the signal from the target sound source M6. Because the propagation distance from the target sound source M6 to the third hydrophone 5 and the second hydrophone 3 or the first hydrophone 2 is different, a time difference Δt occurs between the signal received by the second hydrophone 3 or the first hydrophone 2 and the third hydrophone 5. The speed of sound propagation is v, where v = 1500 m / s. Therefore, the distance from the target sound source M6 to the second hydrophone 3 or the first hydrophone 1 is:

[0056] The distance from the target sound source M6 to the third hydrophone 5 is:

[0057] The distance difference between the target sound source M6 and the second hydrophone 3, or between the first hydrophone 1 and the third hydrophone 5, is

[0058]

[0059] Multiply both sides of formula 3 achievable

[0060]

[0061] Squaring both sides of formulas 4 and 3 respectively, and then adding them together, we get...

[0062]

[0063] Simplifying formula (5) yields...

[0064]

[0065] Pick

[0066]

[0067] Substituting a1 and b1 into formula (6), the simplified expression is:

[0068]

[0069] Plot the hyperbola equation obtained from formula (8) on the above coordinate system;

[0070] (ii) Draw a circular trajectory based on the energy ratio received by the three hydrophones.

[0071] In the space between the second hydrophone 3 or the first hydrophone 2 and the third hydrophone 5, the relationship between the energy intensity of the sound source signal and the distance is expressed by the following formula (9):

[0072]

[0073] Where E1 and E2 represent the energy received by the second hydrophone 3 or the first hydrophone 2 and the energy received by the third hydrophone 5, respectively; d1 and d2 represent the distance from the sound source to the second hydrophone 3 or the first hydrophone 2 and the distance to the third hydrophone 5, respectively; and θ is a random variable with zero mean. According to the above formula, if θ is 0, the ratio of distances obtained in formula (10) is obtained.

[0074]

[0075] According to Apollonius's circle theorem, the locus of points in a plane whose distances to two fixed points are in the ratio of a constant (the constant ≠ 1) is a circle. Let F1(-a,0) and F2(a,0), and the coordinates of the moving point M be (x,y). The following condition is satisfied. And k is a fixed value;

[0076]

[0077]

[0078] Combining formula (11) and formula (12), we get:

[0079]

[0080] Squaring both sides of formula (13) yields:

[0081] (xa) 2 +y 2 =k 2 ((x+a) 2 +y 2 )---Formula (14)

[0082] Expanding and rearranging formula (14) yields the following formula (15).

[0083]

[0084] From formula (15), it can be seen that when k>0 and k≠1, the trajectory of the moving point M is a circle. The circular equation obtained by formula (15) is drawn on the above coordinate system.

[0085] (III) Locate the coordinates of the target sound source M6 on the coordinate system.

[0086] On the coordinate system described above, find the intersection points M1 and M2 of the hyperbola and the circle. Based on the signal received by the second hydrophone 3 or the signal received by the first hydrophone 2, delete the intersection points M1 or M2. The coordinates (x, y) of the obtained M2 or M1 are on the same side as the signal received by the second hydrophone 3 or the first hydrophone 2, which is the position of the target sound source M6.

[0087] The three digital signals output from the preamplifier and filter circuit are sent to the signal processing circuit. In this invention, the signal processing circuit software is the core of signal detection and orientation estimation, and mainly includes the following parts:

[0088] 1. Convert the input serial signal into a parallel signal that is easier for subsequent calculations, and perform preprocessing such as filtering and noise reduction;

[0089] 2. Utilizing the parallel computing capabilities of FPGA, three signals are detected simultaneously. Signal processing algorithms such as FFT are used to determine the frequency, pulse width, and amplitude of the signals, and the target type is estimated based on the signal frequency range.

[0090] 3. By comparing the detection results of the three signals, if two or more signals simultaneously meet the frequency and sound source level thresholds within the same signal cycle, target azimuth estimation can be performed. First, compare the left and right transducers to determine which side of the product the target is located on, and select one of the left or right transducers on the same side as the product for target azimuth estimation. Second, calculate the time delay difference between the signals from the left / right hydrophone and the towed hydrophone, and plot a hyperbola for target estimation. Then, calculate the energy ratio of the two signals and plot an energy ratio pie chart. Finally, find the intersection of the hyperbola and the pie chart, eliminate erroneous points, and estimate the target's azimuth. After completing the detection and azimuth estimation of one cycle of signals, the software will upload the signal detection information and azimuth estimation information to the vehicle control system via the CAN bus, which will then use them as criteria for autonomous navigation to adjust the navigation direction.

[0091] The above description is merely an example for verifying the implementation of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for estimating the location of a target sound source based on hydrophones on an underwater vehicle, wherein a first hydrophone (2) and a second hydrophone (3) are symmetrically mounted on the left and right sides of the underwater vehicle (1), a tow cable (4) is mounted at the rear end of the underwater vehicle (1), and a third hydrophone (5) is mounted on the tow cable (4). During the movement of the underwater vehicle (1), the third hydrophone (5) is located at the rear end of the underwater vehicle (1), and the first hydrophone (2), the second hydrophone (3), and the third hydrophone (5) receive signals emitted by a target sound source (6), characterized in that: The midpoint between the first hydrophone (2) and the second hydrophone (3) of the underwater vehicle (1) is F1, the distance between the first hydrophone (2) and the second hydrophone (3) is negligible, the third hydrophone (5) is F2, the line connecting F1 and F2 is the X-axis, the midpoint between F1 and F2 is the origin of the coordinate system, and a straight line perpendicular to the X-axis is drawn from the origin of the coordinate system as the Y-axis. The coordinates of F1 are (-a,0), the coordinates of F2 are (a,0), and the coordinates of the target sound source M (6) are (x,y). (i) The distances received by the three hydrophones are hyperbolic in the above coordinate system. Because the propagation distances from the target sound source M(6) to the third hydrophone (5) and the second hydrophone (3) or the first hydrophone (2) are different, a time difference Δt occurs between the received signals of the second hydrophone (3) or the first hydrophone (2) and the third hydrophone (5). The speed of sound propagation is v. Therefore, the distance from the target sound source M(6) to the second hydrophone (3) or the first hydrophone (1) is: The distance from the target sound source M(6) to the third hydrophone (5) is: The distance difference between the target sound source M(6) and the second hydrophone (3) or between the first hydrophone (1) and the third hydrophone (5) is: Multiply both sides of formula (3) achievable Squaring both sides of formulas (4) and (3) and then adding them together, we get... Simplifying formula (5) yields... Pick Substituting a1 and b1 into formula (6), the simplified expression is: Plot the hyperbola equation obtained from formula (8) on the above coordinate system; (ii) Draw a circular trajectory based on the energy ratio received by the three hydrophones. In the space between the second hydrophone (3) or the first hydrophone (2) and the third hydrophone (5), the relationship between the energy intensity of the sound source signal and the distance is expressed by the following formula (9): Where E1 and E2 represent the energy received by the second hydrophone (3) or the first hydrophone (2) and the energy received by the third hydrophone (5), respectively; d1 and d2 represent the distance from the sound source to the second hydrophone (3) or the first hydrophone (2) and the distance to the third hydrophone (5), respectively; and θ is a random variable with zero mean. According to the above formula, if θ is 0, the ratio of distances obtained in formula (10) is obtained. According to Apollonius's circle theorem, the locus of points in a plane whose distances to two fixed points are in the ratio of a constant (the constant ≠ 1) is a circle. Let F1(-a,0) and F2(a,0), and the coordinates of the moving point M be (x,y). The following condition is satisfied. And k is a fixed value; Combining formula (11) and formula (12), we get: Squaring both sides of formula (13) yields: (x - a) 2 + y 2 = k 2 ((x + a) 2 + y 2 )---Formula (14) Expanding and rearranging formula (14) yields the following formula (15). From formula (15), it can be seen that when k>0 and k≠1, the trajectory of the moving point M is a circle. The circular equation obtained by formula (15) is drawn on the above coordinate system. (III) Locate the coordinates of the target sound source M(6) on the coordinate system. On the above coordinate system, find the intersection points M1 and M2 of the hyperbola and the circle. Based on the signal received by the second hydrophone (3) or the signal received by the first hydrophone (2), delete the above intersection points M1 or M2. The coordinates (x, y) of M2 or M1 are the position of the target sound source M (6).

2. The method for estimating the location of a target sound source based on hydrophones on an underwater vehicle as described in claim 1, characterized in that: When the second hydrophone (3) or the first hydrophone (2) simultaneously receives the signal from the target sound source M (6), only one of the second hydrophone (3) and the first hydrophone (2) receives the signal from the target sound source M (6).

3. The method for estimating the location of a target sound source based on hydrophones on an underwater vehicle as described in claim 2, characterized in that: The obtained coordinates (x, y) of M2 or M1 are on the same side as the signal received by the second hydrophone (3) or the first hydrophone (2).

4. The method for estimating the location of a target sound source based on hydrophones on an underwater vehicle as described in claim 3, characterized in that: The value of v is 1500 m / s.

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