An underwater target detection method and device

Abstract

The application provides an underwater target detection method and device, relates to the security technology field, and can effectively improve the underwater target detection effect and reduce the false positive rate. The method comprises the following steps: in a detection period, first echo signals of different detection directions received by an ultrasonic transducer array are acquired; an ultrasonic array noise reduction method is used to perform noise reduction processing on the first echo signals of different detection directions to obtain second echo signals of different detection directions; for any detection direction, if the determined signal strength of the second echo signal of the detection direction is greater than a first threshold value, it is determined that a target object exists in an underwater area corresponding to the detection direction of the determined second echo signal; the attribute characteristics of the target object are determined, and when the attribute characteristics meet a preset condition, the target object is determined to be an effective target object; wherein the attribute characteristics of the target object are used to represent the movement of the target object in water. The application can be used in the process of underwater perimeter security.

Description

TECHNICAL FIELD

[0001] The present application relates to the security technology field, and in particular to an underwater target detection method and device. BACKGROUND

[0002] With the improvement of technical level and security level requirements, in various scenes, security is often performed by installing cameras or radar devices in the surrounding environment. However, in some special scenes, security devices need to be deployed underwater to detect the passing of underwater target objects.

[0003] Due to the particularity of the underwater environment, the traditional camera or radar device has poor underwater target detection effect. Sonar is a device that uses the characteristics of sound wave propagation underwater to complete underwater target detection or communication purposes through signal processing. However, due to the complexity of the underwater environment and the presence of a large amount of noise, the sonar is easily disturbed by noise, resulting in poor underwater target detection effect and a high false alarm rate. SUMMARY

[0004] The present application provides an underwater target detection method, device, equipment and storage medium, which can effectively improve the effect of underwater target detection and reduce the false alarm rate.

[0005] In a first aspect, the present application provides an underwater target detection method, which comprises: in a detection period, acquiring first echo signals of different detection directions received by an ultrasonic transducer array; using an ultrasonic array noise reduction method, respectively performing denoising processing on the first echo signals of different detection directions to obtain second echo signals of different detection directions; for any detection direction, if the signal strength of the second echo signal of the detection direction is greater than a first threshold, it is determined that the underwater area corresponding to the detection direction exists a target object; determining the attribute feature of the target object, and when the attribute feature meets a preset condition, determining that the target object is an effective target object; wherein the attribute feature of the target object is used to represent the movement of the target object in water.

[0006] The underwater target detection method provided by the present application can effectively reduce the interference of noise on the target detection effect by using the transducer array noise reduction method to perform noise reduction processing on the echo signal. In addition, based on the denoised echo signal, after determining the existence of the target object, the movement of the target object in water is further determined. Only when the movement of the target object also meets the preset condition, the target object is considered to be an effective target object. Using this method not only reduces the influence of noise, but also considers the factor of movement to detect the underwater target, which has higher recognition accuracy and effectively avoids false alarms caused by noise or other irrelevant targets.

[0007] In a possible implementation manner, the attribute feature of the target object includes a size of the target object and a moving speed of the target object; and the preset condition is that the target object is determined as the valid target object when the size of the target object is greater than a second threshold value and the moving speed of the target object is greater than a third threshold value.

[0008] In another possible implementation manner, before the target object is determined as the valid target object, the method further includes: determining the size of the target object based on the second echo signals of different detection directions; and determining the moving speed of the target object based on the second echo signals with the signal strength greater than the first threshold value in adjacent detection periods.

[0009] In still another possible implementation manner, the size of the target object is determined based on the second echo signals of different detection directions, including: arranging the second echo signals of different detection directions according to the target region detected by the ultrasonic transducer array in a detection period to obtain a to-be-processed image; performing normalization processing on the to-be-processed image to obtain a planar image of the target region; and determining an area of a region with a pixel depth greater than a fourth threshold value in the planar image as the size of the target object.

[0010] In still another possible implementation manner, the speed of the target object is determined based on the second echo signals with the signal strength greater than the first threshold value in adjacent detection periods, including: determining the position of the target object in the adjacent detection periods according to the receiving time and the detection direction of the second echo signals with the signal strength greater than the first threshold value in the adjacent detection periods; and determining the speed of the target object according to the position of the target object in the adjacent detection periods and the detection period.

[0011] In still another possible implementation manner, the first echo signals include target signals and noise signals; and the ultrasonic array denoising method is used to perform denoising processing on the first echo signals of different detection directions to obtain the second echo signals of different detection directions, including: determining a filter coefficient for each first echo signal by using an estimated covariance matrix of the target signals, an estimated covariance matrix of the noise signals and the number of the ultrasonic transducer array; and performing correction on the first echo signals by using the filter coefficient to obtain the second echo signals. It can be understood that the echo signals are collected by using the ultrasonic transducer array, and the denoising processing is performed based on the information of multiple ultrasonic transducers, so that the denoising effect is better, and the noise signals in the echo signals can be removed more effectively compared with the traditional wavelet transform denoising manner.

[0012] In still another possible implementation manner, the filter coefficient is determined by using the following expression:

[0013]

[0014] where h(k, l) is a filter coefficient; Φ xx (k, l) is an estimated covariance matrix of the target signal, Φ vv (k, l) is an estimated covariance matrix of the noise signal; u1 is [1 0 … 0] T is an N-dimensional vector, N is the number of the array of the ultrasonic transducer array; tr represents taking the trace of a matrix;

[0015] The first echo signal is modified, including: the first echo signal is modified by using the following expression:

[0016] x T (k, l) = h H (k, l)y(k, l)

[0017] where x(k, l) is the second echo signal, y(k, l) is the first echo signal, and the superscript H is a conjugate transpose operation.

[0018] In another possible implementation, the estimated covariance matrix of the target signal is determined by using the following expression:

[0019] Φ xx (k, l) = y(k, l)y H (k, l) - Φ vv (k, l)

[0020] where y(k, l)y H (k, l) is a smoothed power spectrum of the first echo signal input;

[0021] The estimated covariance matrix of the noise signal is determined by using the following expression:

[0022] Φ vv (k, l) = α v (k, l)Φ vv (k, l-1) + (1-α v (k, l))y(k, l)y H (k, l)

[0023] where α v (k, l) is a constant, Φ vv is initially a unit matrix.

[0024] In a second aspect, the present application provides an underwater target detection device, comprising: an acquisition module, a processing module and a determination module; the acquisition module is configured to acquire first echo signals of different detection directions received by an ultrasonic transducer array in a detection period; the processing module is configured to perform denoising processing on the first echo signals of different detection directions respectively by using an ultrasonic array denoising method to obtain second echo signals of different detection directions; the determination module is configured to, for any detection direction, if the signal strength of the second echo signal of the detection direction is greater than a first threshold value, determine that there is a target object in the underwater area corresponding to the detection direction; the determination module is further configured to determine the attribute feature of the target object, and when the attribute feature meets a preset condition, determine that the target object is an effective target object; wherein the attribute feature of the target object is used to represent the movement of the target object in water.

[0025] In a possible implementation manner, the attribute feature of the target object comprises: a size of the target object and a moving speed of the target object; and the preset condition is that the size of the target object is greater than a second threshold value and the moving speed of the target object is greater than a third threshold value.

[0026] In another possible implementation manner, the determination module is further configured to determine the size of the target object based on the second echo signals of different detection directions; and determine the moving speed of the target object based on the second echo signals with the signal strength greater than the first threshold value in adjacent detection periods.

[0027] In yet another possible implementation manner, the determination module is specifically configured to arrange the second echo signals of different detection directions according to the target area detected by the ultrasonic transducer array in the detection period to obtain a to-be-processed image; perform normalization processing on the to-be-processed image to obtain a planar image of the target area; and determine the size of the target object as the area of a region with a pixel depth greater than a fourth threshold value in the planar image.

[0028] In yet another possible implementation manner, the determination module is specifically configured to determine the position of the target object in adjacent detection periods according to the receiving time and the detection direction of the second echo signals with the signal strength greater than the first threshold value in the adjacent detection periods; and determine the speed of the target object according to the position of the target object in the adjacent detection periods and the detection period.

[0029] In yet another possible implementation manner, the first echo signal comprises a target signal and a noise signal; and the processing module is specifically configured to, for each first echo signal, determine a filter coefficient by using an estimated covariance matrix of the target signal, an estimated covariance matrix of the noise signal and the array number of the ultrasonic transducer array; and correct the first echo signal by using the filter coefficient to obtain the second echo signal.

[0030] In yet another possible implementation form of the method, the determining comprises determining the filter coefficients using the following expression:

[0031]

[0032] where h(k, l) is the filter coefficient; Φ xx (k, l) is the estimated covariance matrix of the target signal, Φ vv (k, l) is the estimated covariance matrix of the noise signal; u1 is [1 0... 0] T is an N-dimensional vector, N is the number of the array of the ultrasonic transducer array; tr represents taking the trace of a matrix;

[0033] The first echo signal is corrected using the following expression:

[0034] x T (k, l) = h H (k, l)y(k, l)

[0035] where x(k, l) is the second echo signal, y(k, l) is the first echo signal, and the superscript H is the conjugate transpose operation.

[0036] In yet another possible implementation form of the method, the estimated covariance matrix of the target signal is determined using the following expression:

[0037] Φ xx (k, l) = y(k, l)y H (k, l) - Φ vv (k, l)

[0038] where y(k, l)y H (k, l) is the smoothed power spectrum of the first echo signal input;

[0039] The estimated covariance matrix of the noise signal is determined using the following expression:

[0040] Φ vv (k, l) = a v (k, l) Φ vv (k, l-1) + (1 - a v (k, l))y(k, l)y H (k, l)

[0041] where a v (k, l) is a constant, Φ vv is initially a unit matrix.

[0042] In a third aspect, the present application provides an underwater target detection device, comprising: a processor and a memory; the memory stores instructions executable by the processor; the processor is configured to execute the instructions, so that the underwater target detection device implements the method of the first aspect.

[0043] In a fourth aspect, the present application provides a computer readable storage medium, comprising: computer software instructions; when the computer software instructions run in an electronic device, the electronic device implements the method of the first aspect.

[0044] In a fifth aspect, the present application provides a computer program product, when the computer program product runs on a computer, the computer executes the steps of the method described in the first aspect, so as to implement the method of the first aspect.

[0045] The beneficial effects of the second aspect to the fifth aspect can refer to the corresponding description of the first aspect, and will not be repeated. BRIEF DESCRIPTION OF DRAWINGS

[0046] Figure 1 An application environment schematic diagram of an underwater target detection method provided by the present application;

[0047] Figure 2 An ultrasonic transducer array provided by the present application;

[0048] Figure 3 A flowchart of an underwater target detection method provided by the present application;

[0049] Figure 4 A schematic diagram of an echo signal waveform provided by the present application;

[0050] Figure 5 A flowchart of an ultrasonic array noise reduction method provided by the present application;

[0051] Figure 6 A flowchart of a complete scheme provided by the present application;

[0052] Figure 7 A composition schematic diagram of an underwater target detection device provided by the present application;

[0053] Figure 8 A composition schematic diagram of an underwater target detection device provided by the present application. DETAILED DESCRIPTION

[0054] With reference to the drawings and the embodiments of the present application, the technical solutions in the embodiments of the present application will be described clearly and completely. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of the present application.

[0055] It should be noted that in the embodiments of the present application, the words such as "exemplarily" or "for example" are used to represent an example, illustration or description. Any embodiment or design scheme described as "exemplarily" or "for example" in the embodiments of the present application should not be interpreted as more preferred or more advantageous than other embodiments or design schemes. Rather, the words such as "exemplarily" or "for example" are intended to present the relevant concept in a specific manner.

[0056] In order to clearly describe the technical solutions of the embodiments of the present application, in the embodiments of the present application, the words "first", "second", etc. are used to distinguish the same items or similar items with basically the same functions and effects. Those skilled in the art can understand that the words "first", "second", etc. are not used to limit the quantity and execution order.

[0057] In order to facilitate the understanding of the present scheme, first, the related technical terms involved in the present scheme are explained and described.

[0058] 1, ultrasonic transducer array: through a plurality of ultrasonic transducers, an array with different topological structures is formed. The ultrasonic transducer can also be called a sonar, which transmits ultrasonic waves and receives and processes the echo signals of the ultrasonic waves.

[0059] 2, ultrasonic wave: a sound signal with a frequency of more than 20k, which cannot be recognized by the human ear and belongs to the inaudible sound range.

[0060] As described in the background, in some scenarios with high security level requirements, for example, some factories installed beside rivers. In order to ensure high security level, various security devices such as cameras or radars are often used to detect targets on the ground, and timely alarm can be given when effective targets are detected.

[0061] However, in this scenario, there may be some specific target objects that intrude into the security area of the factory from underwater by swimming or the like. For the security of underwater scenes, the security effect of cameras and radars is poor. For the camera, the underwater visibility effect is poor, and the camera can detect a short distance, which is not good. For the radar, the radar detects the target object by emitting electromagnetic waves and receiving the reflection signals of the electromagnetic waves. However, it is found in actual experiments that the attenuation rate of electromagnetic waves in water is very high, which cannot be used as a signal source for detection.

[0062] Therefore, in the underwater detection work, sonar is often used for detection. Sonar is a device for detecting by ultrasonic wave. Because of the good directivity and strong penetration of ultrasonic wave, the ultrasonic wave can propagate far in water, so for underwater environment, sonar is often used to detect underwater targets. However, due to the complexity of underwater environment and various noises, sonar is easily affected by various noises in the detection process, resulting in poor underwater target detection effect and easy triggering of false alarm, causing unnecessary trouble.

[0063] In summary, how to accurately and effectively detect underwater targets is a problem to be solved.

[0064] Based on this, the embodiment of the present application provides a kind of underwater target detection method, this method uses transducer array noise reduction method to carry out noise reduction processing to echo signal, to reduce the interference of noise to target detection effect.Further, through the echo signal after noise reduction, the attribute characteristics of target object are analyzed, only the attribute characteristics meet the preset condition, the target object is considered effective target object.Using this method can reduce the influence of noise, higher accuracy, effectively avoid false alarm caused by interference.

[0065] The underwater target detection method provided by the present application can be applied to the application environment as shown in Figure 1 As shown in Figure 1 The application environment can include: underwater target detection device 101 (or simply detection device) and ultrasonic transducer array 102. The underwater target detection device 101 and the ultrasonic transducer array 102 are connected to each other.

[0066] Among them, the underwater target detection device 101 can be applied to the server. Wherein, the server mentioned here can be a server cluster composed of multiple servers, or a single server, or a computer. The underwater target detection device 101 can be a processor or a processing chip in the server, etc. The embodiment of the present application does not limit the specific device form of the above-mentioned server. Figure 1 The underwater target detection device 101 is applied to a single server as an example. The underwater target detection device 101 can acquire echo signal for processing, and then realize the determination of effective target object.

[0067] The ultrasonic transducer array 102 is used to emit ultrasonic wave signal (or sonar signal), and receive echo signal reflected by target object to ultrasonic wave signal. The ultrasonic transducer array is composed of multiple independent ultrasonic transducers according to certain topological structure, and multiple ultrasonic transducers work cooperatively, with wide detection range and good detection effect.

[0068] Figure 2 A schematic diagram of the ultrasonic transducer array provided by the embodiment of the present application is shown in Figure 2As shown in the figure, each rectangle represents an ultrasonic transducer. Each ultrasonic transducer is arranged according to a certain topology ( Figure 2 (Taking a rectangular structure as an example) The array is arranged on an arc surface. Using the dotted line in the diagram as a boundary, the upper four rows of ultrasonic transducers can be transmitting elements, used to transmit ultrasonic signals. The lower four rows of ultrasonic transducers can be receiving elements, used to receive echo signals. This ultrasonic transducer array is set underwater. It can be seen that the ultrasonic transducers do not require mechanical oscillation; through the coordinated work of multiple ultrasonic transducers, following a phased array scanning method, a 180-degree omnidirectional scan can be achieved, allowing real-time scanning from different directions for any intrusive targets.

[0069] In some embodiments, before underwater target detection is required, the ultrasonic transducer array 102 can be installed underwater (e.g., on a riverbank). After installation, the underwater target detection device 101 first calibrates against reflections from the riverbed, the opposite bank, and objects with strong reflections at certain fixed distances to filter out irrelevant targets and reduce the false alarm rate. After calibration, the ultrasonic transducer array 102 can transmit ultrasonic waves to detect the surrounding environment and receive echo signals. The underwater target detection device can acquire the received echo signals from the ultrasonic transducer array 102. After noise reduction processing, the signal is analyzed to determine whether a target object has been detected, and then its size and speed are used to determine whether it is a valid target object.

[0070] It should be noted that the above embodiments use the underwater target detection device 101 and the ultrasonic transducer array 102 as two separate devices for illustration. In other embodiments, the two devices may be the same device, such as being collectively referred to as the underwater target detection device, which can simultaneously perform ultrasonic wave transmission and reception functions as well as subsequent signal processing functions. This application does not impose specific limitations on this aspect.

[0071] Figure 3 This is a schematic flowchart illustrating an underwater target detection method provided in an embodiment of this application. For example, the underwater target detection method provided in this application can be applied to... Figure 1 The application environment shown.

[0072] like Figure 3 As shown, the underwater target detection method provided in this application may specifically include the following steps:

[0073] S301. During the detection period, the underwater target detection device acquires the first echo signals received by the ultrasonic transducer array from different detection directions.

[0074] In this process, the ultrasonic transducer array sequentially scans the target area from different directions, completing one scan cycle. For example, as... Figure 1As shown, the ultrasonic transducer array scans from direction a to direction b, which completes one detection cycle.

[0075] In some embodiments, when underwater target detection is required, the ultrasonic transducer array can transmit ultrasonic signals (or sonar signals) multiple times in different detection directions of the underwater surrounding environment during each detection cycle. Furthermore, the ultrasonic transducer array can receive the first echo signals reflected by certain objects in different detection directions of the underwater surrounding environment. These objects can be valid targets, such as specific intruders, or noise generated by interfering objects. The underwater target detection device can periodically acquire the first echo signals from different detection directions from the ultrasonic transducer array.

[0076] like Figure 4 As shown in Figure a, the ultrasonic transducer array emits ultrasonic signals that return as echoes after detecting foreign objects, and also returns as echoes after detecting the opposite bank. Figure 4 As shown in Figure b, on the time axis, the emitted wave is closer to the left, and the foreign object is closer to the ultrasonic transducer array. Therefore, the reflected wave (i.e., echo) of the foreign object is earlier than the reflected wave from the opposite bank, but the amplitude of the reflected wave of the foreign object is smaller than that of the reflected wave from the opposite bank.

[0077] It should be noted that, since the first echo signal carries a lot of noise and has a low signal-to-noise ratio, directly analyzing and processing the first echo signal can easily affect the actual target detection effect. Therefore, this embodiment of the application performs noise reduction processing on the first echo signal, specifically executing the following S302.

[0078] S302. The underwater target detection device uses an ultrasonic array noise reduction method to denoise the first echo signals from different detection directions to obtain the second echo signals from different detection directions.

[0079] In the field of ultrasound, traditional detection methods typically use only information from a single ultrasonic echo signal and employ wavelet transform-based noise reduction, which has limited noise reduction effectiveness. Therefore, in this embodiment, an ultrasonic transducer array is used to acquire the echo signal, allowing for simultaneous processing of signals from multiple ultrasonic transducers. This results in better noise suppression and better preservation of the echo signal reflected from the target object.

[0080] Therefore, in some embodiments, after acquiring the first echo signal received by the ultrasonic transducer array, the underwater target detection device can use the ultrasonic array noise reduction method to denoise the first echo signal from different detection directions to obtain a second echo signal with a high signal-to-noise ratio, which facilitates subsequent target detection work.

[0081] Specifically, such as Figure 5As shown, for each first echo signal of different detection direction, the ultrasound array denoising method is adopted to perform denoising processing on the first echo signal to obtain a second echo signal, including S302a-S302b:

[0082] S302a, the underwater target detection device determines the filter coefficient based on the estimated covariance matrix of the target signal, the estimated covariance matrix of the noise signal, and the array number of the ultrasonic transducer array.

[0083] As described above, the first echo signal has a high signal-to-noise ratio and is a noisy signal. The first echo signal includes a target signal and a noise signal, for example, the expression of the first echo signal is as follows:

[0084] y(k, l) = x(k, l) + v(k, l)

[0085] Wherein, y(k, l) is the noisy signal (i.e. the first echo signal) received by the ultrasonic transducer array, x(k, l) is the target signal, and v(k, l) is the noise signal. Wherein, k is the time, l represents the frequency point of the signal, y, x, and v are all vectors.

[0086] In some embodiments, the underwater target detection device can process the noisy signal by using a correlation algorithm to obtain the estimated covariance matrix of the target signal and the noise signal. Further, the underwater target detection device can determine the filter coefficient based on the estimated covariance matrix of the target signal, the estimated covariance matrix of the noise signal, and the array number of the ultrasonic transducer array. Exemplarily, the filter coefficient can be represented as h = [ω1, …, ω M ] T .

[0087] Specifically, the estimated covariance matrix of the target signal and the estimated covariance matrix of the noise signal are determined by the smoothing power spectrum of the first echo signal, which can be represented as y(k, l)y H (k, l). The underwater target detection device can determine the filter coefficient by using the following expression.

[0088]

[0089] In the above expression, Φ xx (k, l) is the estimated covariance matrix of the target signal, and Φ vv (k, l) is the estimated covariance matrix of the noise signal. The superscript -1 represents taking the inverse matrix, and tr represents taking the trace of the matrix (i.e. the sum of the elements on the main diagonal of the matrix). u1 = [1 0 … 0] T is an N-dimensional vector, and N is the array number of the ultrasonic transducer array (i.e. the number of transducers).

[0090] wherein the estimated covariance matrix of the target signal, i.e. Φ xx (k, l) can be determined using the following expression.

[0091] Φ xx (k, l) = Φ yy (k, l) - Φ vv (k, l)

[0092] In the above expression, Φ yy (k, l) is the smoothed power spectrum of the first echo signal input, which can be represented as y(k, l)y H (k, l).

[0093] wherein the estimated covariance matrix of the noise signal, i.e. Φ vv (k, l) can be determined using the following expression.

[0094] Φ vv (k, l) = a v (k, l) Φ vv (k, l - 1) + (1 - a v (k, l))y(k, l)y H (k, l)

[0095] In the above expression, a v (k, l) is a constant, Φ vv is initially a unit matrix, and the superscript H represents the conjugate transpose operation.

[0096] S302b, the underwater target detection device modifies the first echo signal using the filter coefficient to obtain a second echo signal.

[0097] In some embodiments, after determining the filter coefficient, the underwater target detection device can modify the first echo signal using the filter coefficient to achieve denoising processing of the first filtered signal to obtain a second echo signal.

[0098] Specifically, in combination with the above embodiments, after obtaining the filter coefficient, the underwater target detection device can perform a conjugate transpose operation on the filter coefficient and multiply it by a vector representing the first echo signal to obtain a second echo signal after denoising.

[0099] For example, the first echo signal can be modified using the following expression to obtain a second echo signal.

[0100] x T (k, l) = h H (k, l)y(k, l)

[0101] wherein h H(k, l) represents a conjugate transpose operation on the filter coefficients, x T (k, l) is the second echo signal after denoising.

[0102] S303, for any detection direction, if the signal strength of the second echo signal of the detection direction is greater than the first threshold value, the underwater target detection device determines that the underwater area corresponding to the detection direction exists target object.

[0103] Generally speaking, when the signal strength of the echo signal is large enough, it means that the target object is detected in the current detection period. Therefore, in some embodiments, when the signal strength of the second echo signal in a certain detection direction is greater than the first threshold value, the underwater target detection device determines that the target object is detected in the current detection direction at this time, and the second echo signal in the detection direction is the reflection signal formed by the reflection of the ultrasonic signal by the target object. The first threshold value is the intensity threshold value of the signal reflected by the target object, which can be determined according to the actual scene.

[0104] S304, the underwater target detection device determines the attribute characteristics of the target object, and when the attribute characteristics meet the preset condition, determines that the target object is an effective target object.

[0105] Among them, the attribute characteristics of the target object are used to represent the movement of the target object in the water.

[0106] In some embodiments, after determining the existence of the target object, the underwater target detection device can further determine the attribute characteristics of the target object. When the attribute characteristics of the target object meet the preset condition, it can be considered that the target object is an effective target object, for example, it can be determined that a certain specific person has invaded the security area, and an alarm prompt can be performed. In addition, a camera can also be combined for shooting, so that the user can more intuitively determine the characteristic information of the intruder.

[0107] For example, the attribute characteristics of the target object include the size of the target object and the moving speed of the target object. The preset condition is that the size of the target object is greater than the second threshold value, and the moving speed of the target object is greater than the third threshold value. That is, when the size of the object meets the second threshold value, and the moving speed of the target object is greater than the third threshold value, the underwater target detection device determines that the target object is an effective target object.

[0108] Specifically, the underwater target detection device can determine the size of the target object based on the second echo signal of different detection directions. In addition, in adjacent detection periods, the underwater target detection device also determines the speed of the target object based on the second echo signal with a signal strength greater than the first threshold value.

[0109] The method for determining the size of the target object will be described in detail below in combination with specific embodiments. Specifically, the size of the target object is determined based on the second echo signals of different detection directions, and includes the following steps:

[0110] a. In a detection period, the second echo signals of different detection directions are arranged according to a target region detected by the ultrasonic transducer array to obtain a to-be-processed image.

[0111] In some embodiments, after the echo intensity is greater than a certain degree, i.e., it is determined that the target object exists, the underwater target detection device further performs rough morphology imaging on the target object. As mentioned above, the ultrasonic transducer array can scan the surrounding environment. Compared with the traditional single ultrasonic transducer which can only analyze the characteristics through the signal waveform, the ultrasonic transducer array can generate an image based on the echo signal, and the display effect is more intuitive. Specifically, in a detection period, the second echo signals of different detection directions are arranged according to a target region detected by the ultrasonic transducer array to obtain a to-be-processed image. The to-be-processed image is a planar image obtained by the ultrasonic transducer array at an angle facing the target region. The pixel value of each pixel point in the to-be-processed image reflects the amplitude of the echo signal corresponding to the pixel point (or the signal intensity).

[0112] b. The underwater target detection device performs normalization processing on the to-be-processed image to obtain a planar image of the target region.

[0113] Because there is a certain degree of attenuation in signal transmission, the echo signal of a shorter distance has a higher signal intensity, and the echo signal of a longer distance has a lower signal intensity. Because the to-be-processed image is generally composed of echo signals of different distances, it is necessary to perform normalization processing on the to-be-processed image to eliminate the error caused by signal attenuation. Therefore, the to-be-processed image is normalized and converted into a sound pressure graph (i.e., the above-mentioned planar graph), so that the size of the target object can be determined based on the sound pressure graph, and the properties of the target object can be more accurately obtained.

[0114] Specifically, the normalization expression is as follows:

[0115]

[0116] wherein image refers to the to-be-processed graph, image dB refers to the planar image after the sound pressure graph is converted, and max is a maximum value function.

[0117] c. The underwater target detection device determines the area of a region with a pixel depth greater than a fourth threshold value in the planar image as the size of the target object.

[0118] In some embodiments, after obtaining the planar image, the underwater target detection device can determine that the region with a pixel depth greater than the fourth threshold value in the planar image is a region where the target object is located, and then determine the size of the target object through area calculation.

[0119] It should be noted that there can be multiple target objects determined in the same planar image. Considering that the target object of intrusion can be a human body, the area of the target object is relatively large. Therefore, the largest image can be taken as the image of the target object. Alternatively, the image with an area greater than a preset threshold value can be taken as the image of the target object. The specific case can be determined according to the actual situation, and is not specifically limited here.

[0120] The method for determining the speed of the target object will be described in detail below in combination with specific embodiments. Specifically, the method for determining the speed of the target object includes the following steps:

[0121] a. In the adjacent detection periods, the underwater target detection device determines the position of the target object in the adjacent detection periods according to the receiving time of the second echo signal with a signal strength greater than the first threshold value and the detection direction of the second echo signal.

[0122] In some embodiments, after determining the target object, the underwater target detection device can update the position of the target object in real time. Therefore, in the adjacent detection periods, the underwater target detection device can determine the position of the target object in the adjacent detection periods according to the receiving time of the second echo signal with a signal strength greater than the first threshold value and the detection direction of the second echo signal.

[0123] Specifically, according to the time between the emission of the ultrasonic signal and the reception of the echo signal, the approximate distance of the target object can be determined. The expression for determining the distance is as follows: D = cT / 2. Wherein, D represents the distance of the target object from the ultrasonic transducer array. C represents the propagation speed of sound in water. T is the receiving time from the emission of the ultrasonic signal to the reception of the echo signal. In addition, the underwater target detection device can also determine the angle of the target object relative to the ultrasonic transducer array based on the detection direction corresponding to the echo signal. Therefore, according to the angle and distance of the target object, a three-dimensional coordinate system (for example, a polar coordinate system) can be constructed to determine the position of the target object in the three-dimensional coordinate system.

[0124] b. The underwater target detection device determines the speed of the target object according to the position of the target object in the adjacent detection periods and the detection periods.

[0125] In some embodiments, the underwater target detection device can determine the speed of the target object by performing a ratio operation on the distance moved by the target object in the adjacent detection periods and the detection periods after determining the position of the target object in each detection period in the adjacent detection periods.

[0126] For example, the expression of determining the speed is as follows:

[0127]

[0128] Wherein, V represents the speed of the target object. D m For the position of the target object detected in the detection period T m , D l is the position of the target object detected in the detection period T l , T m > T l . ΔT represents the interval of the adjacent two detection periods, that is, the time length of one detection period. Wherein, |D m -D l | represents the moving distance of the target object in the adjacent two detection periods, which can be determined by the method of three-dimensional coordinate operation, and the specific implementation manner can be referred to the related technical documents, which will not be described in detail here.

[0129] It should be noted that the above process of determining the speed of the target object can be performed after the process of determining the size of the target object. After determining the size of the target object, if the size is less than the second threshold value, it is not an effective target object, and the detection continues. If the size is greater than the second threshold value, it is possible to be an effective target object, and the moving speed is further determined. In this way, the calculation amount can be reduced, and the operation burden of the underwater target detection device can be reduced.

[0130] As Figure 6 provides a whole scheme flow chart. As Figure 6 shown, first, pre-calibration is performed to avoid false alarm caused by objects such as river embankments. Then, the sonar signal is emitted to detect whether there is a strong echo signal (i.e. the above step S302) to coarsely detect whether there is a human body. If not, the detection continues. If yes, the position of the object is estimated, and the sonar array imaging is performed. It is further determined whether it is a human body (i.e. the size of the target object is used to judge in the foregoing embodiment). If not, the detection continues. If yes, the object position is updated, and the object speed is calculated to determine whether the speed is greater than the threshold value (i.e. the third threshold value in the foregoing embodiment), if yes, it is confirmed as an effective target object, and the alarm can be output.

[0131] The technical solutions provided in the above embodiments offer at least the following beneficial effects: The underwater target detection method provided in this application, by employing a transducer array noise reduction method to denoise the echo signal, can effectively reduce the interference of noise on the target detection effect. Furthermore, based on the denoised echo signal, after determining the existence of the target object, the underwater movement of the target object is further determined. Only when the movement of the target object also meets the conditions is the target object considered a valid target object. This method not only reduces the impact of noise but also considers the movement factor in underwater target detection, resulting in higher accuracy and effectively avoiding false alarms caused by noise or interference from other irrelevant targets.

[0132] Furthermore, this application employs an ultrasonic transducer array to acquire echo signals and performs noise reduction processing based on information from multiple ultrasonic transducers. Compared to traditional wavelet transform noise reduction methods, this approach offers better noise reduction performance and can more effectively remove noise signals from the echo signals. Additionally, this application combines sonar imaging technology to further verify whether a target object is a valid target object by considering factors such as the size and movement speed of the target object, significantly reducing the false alarm rate and improving security effectiveness. Moreover, this solution can be fully automated, requiring minimal manual intervention, and is highly intelligent, making it applicable to most security scenarios.

[0133] As can be seen, the above mainly describes the solutions provided by the embodiments of this application from a methodological perspective. To achieve the above functions, the embodiments of this application provide corresponding hardware structures and / or software modules for executing each function. Those skilled in the art should readily recognize that, in conjunction with the modules and algorithm steps of the various examples described in the embodiments disclosed herein, the embodiments of this application can be implemented in hardware or a combination of hardware and computer software. Whether a function is executed in hardware or by computer software driving hardware depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0134] In an exemplary embodiment, this application also provides an underwater target detection device. This underwater target detection device may include one or more functional modules for implementing the underwater target detection method described in the above embodiments.

[0135] For example, Figure 7 This is a schematic diagram illustrating the composition of an underwater target detection device provided in an embodiment of this application. Figure 7 As shown, the underwater target detection device includes an acquisition module 701, a processing module 702, and a determination module 703. The acquisition module 701, processing module 702, and determination module 703 are interconnected.

[0136] The acquisition module 701 is configured to acquire, in a detection period, first echo signals of different detection directions received by the ultrasonic transducer array.

[0137] The processing module 702 is configured to perform denoising processing on the first echo signals of different detection directions respectively by using an ultrasonic array denoising method, to obtain second echo signals of different detection directions.

[0138] The determination module 703 is configured to, for any detection direction, if a signal strength of the second echo signal of the detection direction is greater than a first threshold value, determine that an underwater region corresponding to the detection direction exists a target object.

[0139] The determination module 703 is further configured to determine an attribute feature of the target object, and determine that the target object is an effective target object when the attribute feature meets a preset condition; wherein the attribute feature of the target object is used to represent a movement of the target object under water.

[0140] In some embodiments, the attribute feature of the target object includes a size of the target object and a moving speed of the target object; and the preset condition is that the size of the target object is greater than a second threshold value and the moving speed of the target object is greater than a third threshold value.

[0141] In some embodiments, the determination module 703 is further configured to determine the size of the target object based on the second echo signals of different detection directions; and determine the speed of the target object based on the second echo signals with the signal strength greater than the first threshold value in adjacent detection periods.

[0142] In some embodiments, the determination module 703 is specifically configured to arrange the second echo signals of different detection directions according to a target region detected by the ultrasonic transducer array in the detection period, to obtain a to-be-processed image; perform normalization processing on the to-be-processed image, to obtain a planar image of the target region; and determine an area of a region with a pixel depth greater than a fourth threshold value in the planar image as the size of the target object.

[0143] In some embodiments, the determination module 703 is specifically configured to determine a position of the target object in adjacent detection periods according to a receiving time of the second echo signal with the signal strength greater than the first threshold value and the detection direction in the adjacent detection periods; and determine the speed of the target object according to the position of the target object in the adjacent detection periods and the detection period.

[0144] In some embodiments, the first echo signal includes a target signal and a noise signal.

[0145] The processing module 702 is specifically configured to: for each first echo signal, determine a filter coefficient by using an estimated covariance matrix of a target signal, an estimated covariance matrix of a noise signal, and an array number of an ultrasonic transducer array; and correct the first echo signal by using the filter coefficient to obtain a second echo signal.

[0146] In some embodiments, the determining module is specifically configured to determine the filter coefficient by using the following expression:

[0147]

[0148] wherein h(k, l) is the filter coefficient; Φ xx (k, l) is the estimated covariance matrix of the target signal, Φ vv (k, l) is the estimated covariance matrix of the noise signal; u1 is [1 0 … 0] T is an N-dimensional vector, N is the array number of the ultrasonic transducer array; and tr represents taking a trace of a matrix.

[0149] The first echo signal is corrected by using the following expression:

[0150] x T (k, l) = h H (k, l)y(k, l)

[0151] wherein x(k, l) is the second echo signal, y(k, l) is the first echo signal, and the superscript H is a conjugate transpose operation.

[0152] In some embodiments,

[0153] The estimated covariance matrix of the target signal is determined by using the following expression:

[0154] Φ xx (k, l) = y(k, l)y H (k, l) - Φ vv (k, l)

[0155] wherein y(k, l)y H (k, l) is a smoothed power spectrum of the first echo signal input;

[0156] The estimated covariance matrix of the noise signal is determined by using the following expression:

[0157] Φ vv (k, l) = α v (k, l)Φ vv (k, l-1) + (1-α v (k, l))y(k, l)y H (k, l)

[0158] wherein αv (k, l) is a constant, Φ vv Initially, it is an identity matrix.

[0159] In the case of implementing the functions of the above-mentioned integrated modules in the form of hardware, the embodiment of the present application provides a composition diagram of an underwater target detection device, which can be the above-mentioned underwater target detection apparatus. As shown in the figure, the underwater target detection device 800 includes a processor 802, a communication interface 803, and a bus 804. Optionally, the target detection device can further include a memory 801. Figure 8

[0160] The processor 802 can be various exemplary logical blocks, modules and circuits described in combination with the disclosure of the present application. The processor 802 can be a central processing unit, a general-purpose processor, a digital signal processor, an application-specific integrated circuit, a field programmable gate array or other programmable logic device, transistor logic device, hardware component or any combination thereof. It can implement or execute various exemplary logical blocks, modules and circuits described in combination with the disclosure of the present application. The processor 802 can also be a combination of computing functions, such as a combination of one or more microprocessors, a combination of DSP and microprocessor, etc.

[0161] The communication interface 803 is used to connect with other devices through a communication network. The communication network can be an Ethernet, a wireless access network, a wireless local area network (WLAN) and the like.

[0162] The memory 801 can be a read-only memory (ROM) or other type of static storage device that can store static information and instructions, a random access memory (RAM) or other type of dynamic storage device that can store information and instructions, an electrically erasable programmable read-only memory (EEPROM), a magnetic disk storage medium or other magnetic storage device, or any other medium that can be used to carry or store desired program codes in the form of instructions or data structures and can be accessed by a computer, but is not limited thereto.

[0163] As a possible implementation manner, the memory 801 can exist independently of the processor 802, and the memory 801 can be connected with the processor 802 through the bus 804, for storing instructions or program codes. When the processor 802 invokes and executes the instructions or program codes stored in the memory 801, the underwater target detection method provided by the embodiment of the present application can be implemented.​

[0164] In another possible implementation, the memory 801 can also be integrated with the processor 802.

[0165] The bus 804 can be an extended industry standard architecture (EISA) bus, etc. The bus 804 can be divided into an address bus, a data bus, a control bus, etc. For ease of representation, Figure 8 In the figure, only one thick line is used to represent the bus, but this does not mean that there is only one bus or only one type of bus.

[0166] Through the description of the above embodiments, those skilled in the art can clearly understand that, for the convenience and brevity of description, only the above division of functional modules is taken as an example, and in actual application, the above functions can be completed by different functional modules according to needs, that is, the internal structure of the underwater target detection device is divided into different functional modules to complete all or part of the functions described above.

[0167] The embodiment of the present application further provides a computer readable storage medium. All or part of the processes in the above method embodiments can be instructed by computer instructions to complete related hardware, and the program can be stored in the computer readable storage medium. When the program is executed, the processes of the above method embodiments can be included. The computer readable storage medium can be the memory of any of the preceding embodiments. The computer readable storage medium can also be an external storage device of the underwater target detection device, such as a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, etc. Further, the computer readable storage medium can include both the internal storage unit of the underwater target detection device and the external storage device. The computer readable storage medium is used to store the computer program and other programs and data required by the underwater target detection device. The computer readable storage medium can also be used to temporarily store data that has been output or will be output.

[0168] The embodiment of the present application further provides a computer program product, which contains a computer program, and when the computer program product runs on a computer, the computer executes any one of the underwater target detection methods provided in the above embodiments.

[0169] Although this application has been described herein in conjunction with various embodiments, those skilled in the art, by reviewing the accompanying drawings, disclosure, and appended claims, will understand and implement other variations of the disclosed embodiments in carrying out the claimed application. In the claims, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude multiple components. A single processor or other unit can implement several functions listed in the claims. While different dependent claims may recite certain measures, this does not mean that these measures cannot be combined to produce good results.

[0170] Although this application has been described in conjunction with specific features and embodiments, it is obvious that various modifications and combinations can be made thereto without departing from the spirit and scope of this application. Accordingly, this specification and drawings are merely exemplary illustrations of this application as defined by the appended claims, and are considered to cover any and all modifications, variations, combinations, or equivalents within the scope of this application. Clearly, those skilled in the art can make various alterations and modifications to this application without departing from the spirit and scope of this application. Thus, if such modifications and modifications of this application fall within the scope of the claims of this application and their equivalents, this application is also intended to include such modifications and modifications.

[0171] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for detecting underwater targets, characterized in that, The method includes: During the detection period, the first echo signals received by the ultrasonic transducer array in different detection directions are acquired. An ultrasonic array noise reduction method is used to denoise the first echo signals from different detection directions to obtain the second echo signals from different detection directions. For any detection direction, if the signal strength of the second echo signal in the detection direction is greater than the first threshold, then it is determined that there is a target object in the underwater area corresponding to the detection direction. The attribute characteristics of the target object are determined, and when the attribute characteristics meet preset conditions, the target object is determined to be a valid target object; wherein the attribute characteristics of the target object are used to characterize the movement of the target object underwater; The first echo signal includes the target signal and the noise signal; The ultrasonic array noise reduction method is used to denoise the first echo signals from different detection directions to obtain second echo signals from different detection directions, including: For each of the first echo signals, the estimated covariance matrix of the target signal, the estimated covariance matrix of the noise signal, and the number of arrays of the ultrasonic transducer array are used to determine the filtering coefficients. The first echo signal is corrected using the filtering coefficients to obtain the second echo signal.

2. The method according to claim 1, characterized in that, The target object's attributes include: the size of the target object and the target object's movement speed; The preset conditions are that the size of the target object is greater than a second threshold and the moving speed of the target object is greater than a third threshold.

3. The method according to claim 2, characterized in that, Determining the attribute characteristics of the target object includes: The size of the target object is determined based on the second echo signals from different detection directions; Within adjacent detection cycles, the moving speed of the target object is determined based on the second echo signal whose signal strength is greater than the first threshold.

4. The method according to claim 3, characterized in that, Determining the size of the target object based on the second echo signal from different detection directions includes: Within the detection period, the second echo signals in different detection directions are arranged according to the target area detected by the ultrasonic transducer array to obtain the image to be processed; The image to be processed is normalized to obtain a planar image of the target region; The area of ​​the region in the planar image whose pixel depth is greater than a fourth threshold is determined as the size of the target object.

5. The method according to claim 3, characterized in that, Determining the moving speed of the target object based on the second echo signal with a signal strength greater than a first threshold within adjacent detection periods includes: Within adjacent detection cycles, the position of the target object within the adjacent detection cycle is determined based on the reception time of the second echo signal with a signal strength greater than the first threshold and the detection direction. The moving speed of the target object is determined based on its position in adjacent detection cycles and the detection cycle itself.

6. The method according to claim 1, characterized in that, Determining the filter coefficients includes: using the following expression to determine the filter coefficients: Where h(k,l) are the filter coefficients; Φ xx (k,l) is the estimated covariance matrix of the target signal, Φ vv (k,l) is the estimated covariance matrix of the noise signal; u1 is [1 0…0] T , is an N-dimensional vector, where N is the number of arrays of the ultrasonic transducer array; tr represents the trace of the matrix; The correction of the first echo signal includes: correcting the first echo signal using the following expression: x T (k,l)=h H (k,l)y(k,l) Where x(k,l) is the second echo signal, y(k,l) is the first echo signal, and the superscript H represents the conjugate transpose operation.

7. The method according to claim 6, characterized in that, The estimated covariance matrix of the target signal is determined using the following expression: Φ xx (k,l)=y(k,l)y H (k,l)-Φ vv (k,l) Where y(k,l)y H (k,l) represents the smoothed power spectrum of the first echo signal input; The estimated covariance matrix of the noise signal is determined using the following expression: F vv (k,l)=a v (k,l)Φ vv (k,l-1)+(1-a v (k,l))y(k,l)y H (k,l) Where, α v (k,l) are constants, Φ vv It is initially an identity matrix.

8. An underwater target detection device, characterized in that, The device includes: an acquisition module, a processing module, and a determination module; The acquisition module is used to acquire the first echo signals received by the ultrasonic transducer array in different detection directions within the detection period. The processing module is used to perform noise reduction processing on the first echo signals in different detection directions using an ultrasonic array noise reduction method to obtain second echo signals in different detection directions. The determining module is used to determine that, for any detection direction, if the signal strength of the second echo signal in the detection direction is greater than a first threshold, the underwater area corresponding to the detection direction contains a target object. The determining module is further configured to determine the attribute characteristics of the target object, and when the attribute characteristics meet preset conditions, determine the target object as a valid target object; wherein the attribute characteristics of the target object are used to characterize the movement of the target object underwater; The first echo signal includes a target signal and a noise signal; the processing module is specifically used to determine the filtering coefficients for each first echo signal using the estimated covariance matrix of the target signal, the estimated covariance matrix of the noise signal, and the number of arrays of the ultrasonic transducer array; and to correct the first echo signal using the filtering coefficients to obtain the second echo signal.

9. The apparatus according to claim 8, characterized in that, The attribute characteristics of the target object include: the size of the target object and the movement speed of the target object; the preset condition is that the size of the target object is greater than a second threshold and the movement speed of the target object is greater than a third threshold. The determining module is specifically used to: determine the size of the target object based on the second echo signal from different detection directions; and determine the moving speed of the target object based on the second echo signal with a signal strength greater than a first threshold within adjacent detection cycles. The determining module is specifically used to: within the detection period, arrange the second echo signals in different detection directions according to the target area detected by the ultrasonic transducer array to obtain an image to be processed; perform normalization processing on the image to be processed to obtain a planar image of the target area; and determine the area of ​​the region in the planar image whose pixel depth is greater than a fourth threshold as the size of the target object. The determining module is specifically used to: determine the position of the target object within an adjacent detection period based on the reception time of the second echo signal with a signal strength greater than a first threshold and the detection direction; and determine the velocity of the target object based on its position within the adjacent detection period and the detection period. The determining module is specifically used to determine the filter coefficients using the following expression: Where h(k,l) are the filter coefficients; Φ xx (k,l) is the estimated covariance matrix of the target signal, Φ vv (k,l) is the estimated covariance matrix of the noise signal; u1 is [1 0…0] T , is an N-dimensional vector, where N is the number of arrays of the ultrasonic transducer array; tr represents the trace of the matrix; The first echo signal is corrected using the following expression: x T (k,l)=h H (k,l)y(k,l) Where x(k,l) is the second echo signal, y(k,l) is the first echo signal, and the superscript H indicates the conjugate transpose operation; The estimated covariance matrix of the target signal is determined using the following expression: Φ xx (k,l)=y(k,l)y H (k,l)-Φ vv (k,l) Where y(k,l)y H (k,l) represents the smoothed power spectrum of the first echo signal input; The estimated covariance matrix of the noise signal is determined using the following expression: F vv (k,l)=a v (k,l)Φ vv (k,l-1)+(1-a v (k,l))y(k,l)y H (k,l) Where, α v (k,l) are constants, Φ vv It is initially an identity matrix.

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