Method for improving anti-detection capability of underwater equipment by using hydrophone

Abstract

The invention belongs to the technical field of underwater detection, and relates to a method for improving the anti-detection capability of underwater equipment by using a hydrophone, which comprises the following steps: the underwater equipment enters water and is firstly electrified to work, and then the hydrophone is electrified to work; the hydrophone starts an active sonar system to actively detect surrounding targets, when the hydrophone detects an opponent signal, active sonar detection is stopped, and a passive sonar system is started to passively receive the opponent signal; the hydrophone analyzes the frequency of the opponent signal; a motor in the underwater equipment is turned on to enable the underwater equipment to float on the water surface, detected opponent information is reported to a ground receiving shore station, and in the floating process of the underwater equipment, the working frequency of the motor is intermittently regulated and controlled, so that the motor is switched between single frequency multiplication and multiple frequency multiplication of opponent signal frequency. According to the invention, the problem that the underwater equipment is easily captured by the opponent when emergently floating after the hydrophone carried by the underwater equipment detects the opponent signal is solved, and the anti-detection capability of the underwater equipment of our part is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of underwater detection, and in particular relates to a method for improving the anti-detection capability of underwater equipment by utilizing a hydrophone. Background Art

[0002] The underwater equipment widely used in marine environmental monitoring includes buoys, submersibles, submersibles, underwater gliders, etc. Among them, many buoys are profile buoys, which use buoyancy drive to realize autonomous diving, fixed-depth drifting, surfacing CTD measurement, surface communication, and re-diving profile cycle process, that is, regular or periodic up and down ocean profiles, and can carry different types of sensors (such as CTD, DO, CO2, etc.) to realize profile measurement of marine environmental elements. The data collected by the buoy can be transmitted to the ground receiving shore station through the satellite communication system; the submersible buoy is located below the water surface as a whole and is fixed in a specific position by an anchor system. Through the installation of sensors at different depths, full-water depth, fixed-point, long-term, continuous, multi-level, and multi-element synchronous observation can be realized, which has the advantages of good concealment and not easy to be destroyed.

[0003] The above-mentioned underwater equipment usually has the ability to dive and float. When a hydrophone for underwater sound wave detection and reception is installed on the underwater equipment, it can play a variety of key roles in the ocean, such as underwater communication monitoring of underwater enemy targets, mine detection, marine bioacoustic research, marine environment monitoring, seabed topography mapping, etc. Specifically, a hydrophone is a transducer that converts underwater sound signals into electrical signals, and it is widely used in underwater detection and other fields. Hydrophone detection is divided into active sonar detection and passive sonar detection; active sonar detection is an active sonar system that generates an electrical signal through a transmitter, converts the electrical signal into an acoustic signal through a transducer and transmits it into the water. When the sound wave encounters the target object, it will be reflected back. The reflected sound wave is received by the transducer and converted into an electrical signal. The receiver amplifies and processes the signal, and finally determines the position, distance, speed, shape and other information of the underwater target based on the time difference and frequency shift of the transmitted and received signals; passive sonar detection is a passive sonar system that mainly relies on the sound emitted by the underwater target itself, such as the mechanical noise of the ship, propeller noise, and the sound of marine life. These sound signals are received by hydrophones, analyzed and processed to determine the direction, type and other information of the underwater target, while the passive sonar system itself does not emit sound waves.

[0004] When a hydrophone is mounted on an underwater device for underwater enemy target detection, the hydrophone is usually turned on underwater and active or passive sonar detection is used to monitor targets around the ocean. When the enemy's torpedoes, underwater vehicles, submarines and other equipment are detected, the underwater device must urgently surface to the surface and report the enemy's information to the ground receiving shore station using drones or satellite communications. However, this method has a serious problem. When the underwater device urgently surfaces, the motor and other equipment in the underwater device need to be turned on. The motor will generate noise when working, which can easily be captured by the enemy, causing the enemy to quickly slip away. What's worse, the enemy may capture the location of our equipment and interfere with or destroy it. Summary of the invention

[0005] In view of the shortcomings existing in the related technology, the present invention provides a method for improving the anti-detection capability of underwater equipment by using hydrophones, aiming to solve the problem that the underwater equipment is easily captured by the opponent when the hydrophone carried by the underwater equipment detects the opponent's signal and the underwater equipment urgently surfaces, thereby improving the anti-detection capability of our underwater equipment.

[0006] The present invention provides a method for improving the anti-detection capability of underwater equipment by using a hydrophone, comprising the following steps: S1. Load the hydrophone onto the underwater equipment; S2, the underwater equipment enters the water and is powered on first, and then the hydrophone is powered on; S3, the hydrophone activates the active sonar system to actively detect surrounding targets; when the hydrophone detects the opponent's signal, the active sonar detection is stopped and the passive sonar system is activated to passively receive the opponent's signal; S4, hydrophone analyzes the frequency of the opponent's signal; S5. Turn on the motor in the underwater device to make the underwater device float to the surface, so as to report the detected opponent information to the ground receiving shore station; during the surfacing process of the underwater device, intermittently adjust the working frequency of the motor to switch between single and multiple times the opponent's signal frequency.

[0007] In some embodiments, in step S5, when the underwater device starts to float up, the intermittent regulation of the motor operating frequency is performed according to the following steps: S51, adjust the motor's operating frequency to be equal to the opponent's signal frequency, and delay Second; S52, adjust the motor's operating frequency to a multiple of the opponent's signal frequency, and delay Second; S53, repeating steps S51 to S52 until the underwater device floats to the surface; The delay time is in seconds. and All are random numbers.

[0008] In some embodiments, the multiple frequency is doubled frequency or tripled frequency.

[0009] In some embodiments, the delay seconds are calculated as follows: C1. Whenever the motor operating frequency is adjusted, all the spectrum noises monitored by the hydrophone are sorted from small to large, and then Mark and calculate the difference between two adjacent noises according to formula (1) , according to formula (2) to calculate the adjacent The difference ;in, is the total amount of spectral noise; ; ; (1); (2); C2, from Start by judging Is it satisfied? and ,in, is the noise mean, calculated according to formula (3); when When the requirements are met, Values ​​are marked as ,Will As the spectral reference point of the spectral noise monitored by the hydrophone that exceeds the surrounding environmental noise; (3); C3. Calculate the standard deviation of the noise signal strength exceeding the reference point of the ambient noise spectrum according to formula (4) ; (4); C4. In step S51, after the operating frequency of the motor is adjusted to be equal to the frequency of the opponent signal, the frequency of the motor is calculated through steps C1 to C3. and , and then calculate the delay in seconds according to formula (5) In step S52, when the operating frequency of the motor is adjusted to a multiple of the opponent's signal frequency, first calculate through steps C1 to C3 and , and then calculate the delay in seconds according to formula (6) ;in, For numerical values A random number between (5); (6).

[0010] In some embodiments, in step S5, the operating frequency of the motor is controlled by PWM; after the adjustment of the operating frequency of the motor is completed, the PWM duty cycle is adjusted. The motor speed is adjusted by PWM duty cycle Calculate according to formula (7), where is the period of the preset PWM signal; (7).

[0011] In some of the embodiments, the underwater device is a buoy; before executing step S5, the current working state of the buoy is first determined; if the buoy is in a hovering state or a diving state, the current working state of the buoy is first stopped and then switched to a floating state; if the buoy is in a floating state, it continues to float.

[0012] In some of the embodiments, the underwater device is a submerged buoy; when executing step S5, the submerged buoy directly changes from an anchored state to a floating state.

[0013] Based on the above technical scheme, the method of using hydrophones to improve the anti-detection capability of underwater equipment in the embodiment of the present invention solves the problem that after the hydrophone carried by the underwater equipment detects the opponent's signal, the underwater equipment is easily captured by the opponent due to the operation of the motor when it urgently floats, through the coordinated application of active sonar detection and passive sonar detection of the hydrophone, dynamically changing the motor frequency to a single or multiple times the opponent's signal frequency during the surfacing of the underwater equipment, and dynamically adjusting the motor speed, thereby improving the anti-detection capability of our underwater equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings: Figure 1 It is a schematic diagram of various underwater equipment equipped with hydrophones when underwater; Figure 2 A flow chart of a method for improving the anti-detection capability of underwater equipment using a hydrophone according to the present invention; Figure 3 This is a flow chart of intermittently regulating the motor operating frequency in step S5 of the present invention. DETAILED DESCRIPTION

[0015] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0016] In the description of the present invention, it should be understood that the terms "center", "lateral", "longitudinal", "up", "down", "top", "bottom", "inside", "outside", "left", "right", "front", "back", "vertical", "horizontal", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0017] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0018] refer to Figure 1-Figure 3 As shown, the present invention provides a method for improving the anti-detection capability of underwater equipment by using a hydrophone, the method comprising the following steps: S1. Mount the hydrophone on the underwater equipment, such as Figure 1 As shown; the underwater equipment has the ability to dive and float, including but not limited to profile drifting buoys, deep-sea profile drifting buoys, air-dropped profile buoys, deep-sea submersibles, unmanned submersibles, manned submersibles, underwater gliders, etc.

[0019] S2. The underwater equipment is put into water and powered on first, and then the hydrophone is powered on.

[0020] S3. The hydrophone activates the active sonar system to actively detect surrounding targets. When the hydrophone detects the opponent's signal, it immediately deactivates the active sonar system, that is, stops active sonar detection to avoid being detected by the opponent or alerting the opponent, and instead activates the passive sonar system to passively receive the opponent's signal, but does not actively send out a signal.

[0021] It is further explained that active sonar detection has the advantage of high detection accuracy, especially for stationary targets, but it is easy to be exposed because it actively sends out signals; passive sonar detection has the advantage of good concealment because it only receives signals, and has a good detection effect on dynamic targets, but it cannot directly measure distance and has difficulty in detecting silent targets; therefore, through the coordinated application of active sonar detection and passive sonar detection, it is possible to quickly detect opponent targets, thereby better conducting covert detection of opponent targets.

[0022] S4. The hydrophone analyzes the frequency of the opponent's signal. The analysis method is well known to those skilled in the art and will not be described in detail here.

[0023] S5. Turn on the motor in the underwater device, and the motor starts working to make the underwater device float to the surface urgently, so as to report the detected opponent information to the ground receiving shore station; it should be noted that the opponent information such as the opponent signal and signal frequency obtained by the hydrophone is stored in the communication module of the underwater device. When the underwater device floats to the surface, the communication module of the underwater device reports the opponent information to the ground receiving shore station through a drone or satellite.

[0024] It is further explained that during the surfacing process of underwater equipment, the operating frequency of the motor in the underwater equipment is intermittently regulated so that the operating frequency of the motor is switched between a single frequency (i.e. the same frequency) and a multiple frequency of the opponent's signal frequency, that is, the operating frequency of the motor of our underwater equipment is dynamically changed; therefore, even if the opponent's detection equipment detects the noise signal generated by the operation of the motor when our underwater equipment is surfacing, it will be the opponent's own signal frequency or a harmonic frequency of a multiple frequency, and then the detected signal of our side will be discarded as irrelevant noise; thereby, it is beneficial for our underwater equipment to quickly float to the surface to report the opponent's information and seize the initiative without the opponent's perception.

[0025] In the above-mentioned illustrative embodiment, while the underwater equipment is working normally, the coordinated application of active sonar detection and passive sonar detection by the hydrophone can quickly detect the opponent's target, and conduct covert detection of the opponent's target, and then parse the opponent's signal frequency; during the surfacing process of the underwater equipment, by dynamically changing the motor frequency to a single or multiple times the opponent's signal frequency, even if the opponent's detection equipment detects the noise signal generated by the motor when our underwater equipment is surfacing, it is difficult to distinguish the noise from the frequency or harmonics emitted by itself, and thus it is difficult to identify our underwater equipment, thereby avoiding the possibility of our underwater equipment being captured by the opponent due to the motor operation during the surfacing process, and significantly improving the anti-detection capability of our underwater equipment.

[0026] refer to Figure 1-Figure 3 As shown, in some embodiments, in step S5, when the underwater device starts to float up, the intermittent regulation of the operating frequency of the motor in the underwater device is performed according to the following steps: S51, adjust the motor's operating frequency to be equal to the opponent's signal frequency, and delay seconds, that is, the motor in the underwater device runs at the same working frequency as the opponent seconds to make the underwater equipment float; S52, adjust the motor's operating frequency to a multiple of the opponent's signal frequency, and delay seconds, that is, the motors in the underwater equipment run at a frequency several times that of the opponent seconds to make the underwater equipment float; S53, repeating steps S51 to S52 until the underwater device floats to the surface; The delay time is in seconds. and All are random numbers.

[0027] The above-mentioned illustrative embodiment refines the specific means of intermittent regulation of the motor operating frequency; through the switching of the motor frequency and the random delay setting after the switching, the signal recognition and tracking logic of the opponent's detection equipment is disrupted and confused, thereby effectively reducing the risk of being discovered and locked by the opponent, providing reliable concealment protection for the surfacing of our underwater equipment, and further improving the anti-detection capability of our underwater equipment.

[0028] In some embodiments, the multiple frequency is doubled or tripled.

[0029] In some embodiments, the delay seconds are calculated as follows: C1. After the motor operating frequency is adjusted once, all the spectrum noises detected by the hydrophone are sorted from small to large, and then sorted in order. The unit is decibel, where This is the total amount of spectral noise detected by the hydrophone at this time.

[0030] According to formula (1), the difference between two adjacent noises is calculated. , according to formula (2) to calculate the adjacent The difference ;in, ; ; (1); (2).

[0031] C2, from Start by judging Is it satisfied? and ,in, is the noise mean, calculated according to formula (3); (3); when satisfy and , then the Values ​​are marked as ,Will It is the spectral reference point in the spectral noise monitored by the hydrophone that exceeds the surrounding environmental noise.

[0032] C3. Calculate the standard deviation of the noise signal strength exceeding the reference point of the ambient noise spectrum according to formula (4) ; (4).

[0033] C4. In step S51, after the operating frequency of the motor is adjusted to be equal to the frequency of the opponent signal, the current operating frequency of the motor is calculated through steps C1 to C3. and , and then calculate the delay in seconds according to formula (5) ;in, For numerical values A random number between is the total amount of spectral noise monitored by the hydrophone in step C1; (5).

[0034] In step S52, after the operating frequency of the motor is adjusted to a multiple of the opponent signal frequency, the current motor operating frequency is calculated through steps C1 to C3. and , and then calculate the delay in seconds according to formula (6) ;in, For numerical values A random number between is the total amount of spectral noise monitored by the hydrophone in step C1; (6).

[0035] The above exemplary embodiment can accurately find the signal that exceeds the ambient noise and take the value of the exceeding part. The larger the value, the stronger the detected opponent signal is, which proves that the opponent is closer to us. The calculated delay seconds and The duration is relatively long, that is, the number of frequency changes is reduced; if the value exceeds The smaller it is, the weaker the detected opponent signal is, which proves that the opponent is farther away from us. The calculated delay seconds and The duration of is relatively short, that is, the number of frequency conversions is increased; in formula (5) and formula (6), Taking random numbers is the algorithm for discretizing this solution, which limits the maximum cycle value and cycle range of the motor frequency switching to avoid delay seconds. and The duration is too long.

[0036] In some embodiments, in step S5, the operating frequency of the motor is controlled by PWM; specifically, the operating frequency of the local motor is controlled by STM32 PWM (Pulse Width Modulation); the following briefly introduces the control method of the motor operating frequency.

[0037] In the STM32 timer, the frequency of the PWM signal is determined by the timer clock source frequency ftimer, the prescaler coefficient PSC (Prescaler) and the auto reload value ARR (Auto Reload Register). The clock source of the timer usually comes from the system clock or other clock sources, such as the system clock of STM32 is fsys. First, the clock source fsys is divided by the prescaler PSC to obtain the actual timer clock source frequency ftimer, which is calculated as follows: ftimer=fsys / (PSC+1); then, the timer counter counts at the frequency of ftimer. When the counter value reaches the auto reload value ARR, the counter will start counting from 0 again to complete a cycle. Therefore, the period T of the PWM signal is T=(ARR+1) / ftimer, and the frequency f=ftimer / (ARR+1).

[0038] To change the frequency f of PWM, you can adjust the pre-scaling coefficient PSC and the automatic reload value ARR. When PSC is increased, the timer clock source frequency ftimer decreases, and the frequency f of the PWM signal will also decrease accordingly; when ARR is increased, the time required for the counter to count to ARR becomes longer, the PWM cycle becomes longer, and the frequency f decreases when the timer clock source frequency ftimer remains unchanged; conversely, reducing PSC or ARR can increase the frequency f of PWM. In practical applications, the pre-scaling coefficient PSC and the automatic reload ARR are flexibly adjusted according to the specific system clock source frequency ftimer and the required PWM frequency f. After the PWM frequency f is applied to the motor, the operating frequency of the motor in the underwater equipment is controlled.

[0039] In step S5, after each adjustment of the motor operating frequency is completed, the PWM duty cycle is adjusted. The motor speed is adjusted by PWM duty cycle. Refers to the ratio of the high level time to the period in the pulse wave, expressed as a percentage; PWM duty cycle Calculate according to formula (7), where is the period of the preset PWM signal; (7).

[0040] The above exemplary embodiments refine the motor speed adjustment method and the PWM duty cycle calculation method; The larger the value, the stronger the detected opponent signal is, which proves that the opponent is closer to us. The calculated duty cycle Smaller, that is, slowing down the motor speed to avoid being detected by the opponent and improving the safety and concealment of underwater equipment when it surfaces; The smaller it is, the weaker the detected opponent signal is, which proves that the opponent is farther away from us. The calculated duty cycle Larger, that is, to increase the motor speed so that the underwater equipment can float up quickly; thus, during the floating process of the underwater equipment, the motor speed can be dynamically adjusted according to the strength of the opponent's signal, so that the underwater equipment can float to the surface quickly and safely.

[0041] In some embodiments, the underwater device is a buoy; before executing step S5, the current working state of the buoy is first determined; if the buoy is in a suspended state or a submerged state, the current working state of the buoy is first stopped and then switched to a floating state; if the buoy is in a floating state, it continues to float. In some embodiments, the underwater device is a submerged buoy; when executing step S5, the submerged buoy directly switches from an anchored state to a floating state.

[0042] Through the description of multiple embodiments of the method for improving the anti-detection capability of underwater equipment by using a hydrophone of the present invention, it can be seen that the present invention has at least one or more of the following advantages: 1) While the underwater equipment is working normally, the active sonar detection of the hydrophone and the passive sonar detection can be used together to quickly detect the enemy's target, conduct covert detection of the enemy's target, and then analyze the enemy's signal frequency; 2) During the surfacing process of underwater equipment, by dynamically changing the motor frequency to a single or multiple frequency of the opponent's signal frequency, even if the opponent's detection equipment detects the noise signal generated by the motor when our underwater equipment is surfacing, it will be regarded as the noise generated by the opponent's own signal frequency or harmonic frequency and will not pay attention to it, thus avoiding the possibility of our underwater equipment being captured by the opponent due to the motor operation during the surfacing process; 3) During the surfacing process of underwater equipment, the random delay setting after the motor frequency switching can disrupt and confuse the signal recognition and tracking logic of the opponent's detection equipment, effectively reducing the risk of being discovered and locked by the opponent, and further improving the anti-detection capability of our underwater equipment; 4) During the surfacing process of the underwater equipment, the motor speed is dynamically adjusted by adjusting the PWM duty cycle according to the strength of the opponent's signal, so that the underwater equipment can float to the surface quickly and safely; 5) In summary, the present invention can solve the problem that after the hydrophone carried by the underwater equipment detects the opponent's signal and the underwater equipment is easily captured by the opponent due to the operation of the motor when it urgently floats up, it can significantly improve the anti-detection capability of our underwater equipment, which is conducive to our underwater equipment to quickly and safely float to the surface and report the opponent's information in time without the opponent's perception.

[0043] Finally, it should be noted that: the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0044] The above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or some technical features can be replaced by equivalents without departing from the spirit of the technical solution of the present invention, which should be included in the scope of the technical solution for protection of the present invention.

Claims

1. A method for improving the anti-detection capability of underwater equipment using a hydrophone, characterized in that: The following steps are involved: S1. Load the hydrophone onto the underwater equipment; S2, the underwater equipment enters the water and is powered on first, and then the hydrophone is powered on; S3, the hydrophone activates the active sonar system to actively detect surrounding targets; when the hydrophone detects the opponent's signal, the active sonar detection is stopped and the passive sonar system is activated to passively receive the opponent's signal; S4, the hydrophone analyzes the frequency of the opponent's signal; S5, turning on the motor in the underwater device to make the underwater device float to the surface of the water, so as to report the detected opponent information to the ground receiving shore station; During the surfacing process of the underwater device, the operating frequency of the motor is intermittently regulated to switch between the single frequency and the multiple frequency of the opponent signal frequency.

2. The method for improving the anti-detection capability of underwater equipment using a hydrophone according to claim 1, characterized in that: In step S5, when the underwater device starts to float up, the intermittent regulation of the motor operating frequency is performed according to the following steps: S51, adjusting the operating frequency of the motor to be equal to the frequency of the opponent's signal, and delaying Second; S52, adjusting the operating frequency of the motor to a multiple of the opponent's signal frequency, and delaying Second; S53, repeating steps S51 to S52 until the underwater device floats to the surface of the water; The delay time is in seconds. and All are random numbers.

3. The method for improving the anti-detection capability of underwater equipment using a hydrophone according to claim 1, characterized in that: The multiple frequency is double frequency or triple frequency.

4. The method for improving the anti-detection capability of underwater equipment using a hydrophone according to claim 2, characterized in that: The delay seconds are calculated according to the following steps: C1. Whenever the motor operating frequency is adjusted, all the spectrum noises monitored by the hydrophone are sorted from small to large, and the noises are sorted in order of Mark and calculate the difference between two adjacent noises according to formula (1) , according to formula (2) to calculate the adjacent The difference ;in, is the total amount of spectral noise; ; ; (1)； (2)； C2, from Start by judging Is it satisfied? and ,in, is the noise mean, calculated according to formula (3); when When the requirements are met, Values ​​are marked as ,Will As a frequency spectrum reference point exceeding the surrounding environment noise in the frequency spectrum noise monitored by the hydrophone; (3)； C3. Calculate the standard deviation of the noise signal strength exceeding the reference point of the ambient noise spectrum according to formula (4) ; (4)； C4. In step S51, after the operating frequency of the motor is adjusted to be equal to the frequency of the opponent signal, the operation frequency of the motor is calculated through steps C1 to C3. and , and then calculate the delay in seconds according to formula (5) In step S52, after the operating frequency of the motor is adjusted to a multiple of the opponent's signal frequency, the first step is to calculate through steps C1 to C3 and , and then calculate the delay in seconds according to formula (6) ;in, For numerical values A random number between (5)； (6)。 5. The method for improving the anti-detection capability of underwater equipment using a hydrophone according to claim 4, characterized in that: In step S5, the operating frequency of the motor is controlled by PWM. After the adjustment of the operating frequency of the motor is completed, the PWM duty cycle is adjusted. The speed of the motor is adjusted in the manner of: Calculate according to formula (7), where is the period of the preset PWM signal; (7)。 6. The method for improving the anti-detection capability of underwater equipment using a hydrophone according to any one of claims 1 to 5, characterized in that: The underwater device is a buoy; before executing step S5, first determine the current working state of the buoy; if the buoy is in a hovering state or a diving state, first stop the current working state of the buoy and then switch to a floating state; if the buoy is in a floating state, continue to float.

7. The method for improving the anti-detection capability of underwater equipment using a hydrophone according to any one of claims 1 to 5, characterized in that: The underwater device is a submerged buoy; when executing step S5, the submerged buoy directly changes from an anchored state to a floating state.

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