Underwater preset system activation method, system and device based on laser-induced sound

Abstract

The invention provides an underwater preset system activation method, system and device based on laser-induced sound, and solves the technical problems that an existing laser-induced sound communication technology is insufficient in reliability in the aspect of signal code element design, is weak in anti-interference capability and is difficult to stably trigger a preset system in a complex marine environment. The method comprises the following steps: acquiring an activation instruction of to-be-activated equipment, encoding to generate an activation signal, inputting the activation signal into a control module, adjusting and emitting laser to an underwater activation area by the control module, performing photoacoustic conversion on the laser on a water-air interface, and transmitting an acoustic signal to the to-be-activated equipment; the preset system receives the sound signal transmitted to the to-be-activated equipment, converts the sound signal into an electric signal, carries out envelope extraction and sampling to obtain a sampled signal, carries out demodulation to obtain a signal frequency, compares the signal frequency with a preset activation frequency, and if half or more of the signal frequencies are matched, it is judged that the activation is effective, and the preset system enters a working state; otherwise, keeping dormancy. The method can be widely applied to the technical field of cross-medium communication.

Description

Technical Field

[0001] This application belongs to the field of cross-media communication technology, and more specifically, relates to a method, system and device for activating an underwater pre-positioned system based on laser-induced acoustics. Background Technology

[0002] Underwater pre-positioned systems are core facilities for three-dimensional marine monitoring and national defense early warning. The reliability, concealment, and anti-interference capabilities of their activation technology are crucial. Existing activation methods mostly rely on underwater acoustic communication technology. While this technology has advantages such as low attenuation in water and the ability to achieve long-distance transmission, the transmitting end and relay devices are often exposed on the water surface or in shallow ocean, resulting in insufficient concealment and limited deployment and operational flexibility. Furthermore, in complex sea conditions, it is susceptible to noise, multipath effects, and current disturbances, limiting triggering reliability.

[0003] Laser-induced acoustic communication technology enables direct cross-medium information transmission between airborne platforms and underwater targets, offering advantages such as high concealment, flexible platform deployment, and wide coverage. It effectively meets the rapid activation requirements of long-term submerged equipment and provides a novel technological approach for superior remote activation. However, existing laser-induced acoustic communication technologies suffer from insufficient reliability and weak anti-interference capabilities in signal symbol design, making stable triggering difficult in complex marine environments. Therefore, there is an urgent need to design a highly robust activation signal and symbol structure to improve the stability and security of the activation process. Summary of the Invention

[0004] The purpose of this application is to provide a method, system, and apparatus for activating an underwater pre-set system based on laser-induced acoustics, so as to solve the technical problems of insufficient reliability and weak anti-interference ability in the signal symbol design of existing laser-induced acoustic communication technology, which makes it difficult to stably trigger the pre-set system in complex marine environments.

[0005] To achieve the above objectives, a first aspect of this application provides a method for activating an underwater pre-positioned system based on laser-induced acoustics, comprising the following steps: The activation command of the device to be activated is obtained, and the device to be activated is encoded using multi-frequency shift keying technology to generate an activation signal. The activation signal is input to the control module, which adjusts and emits a laser to the underwater activation area. The laser performs photoacoustic conversion at the water-air interface and transmits the acoustic signal to the device to be activated. The preset system receives the acoustic signal transmitted to the device to be activated, converts it into an electrical signal, performs envelope extraction and sampling to obtain the sampled signal, demodulates it to obtain the signal frequency, and compares it with the preset activation frequency. If half or more of the signal frequencies match, it is determined to be effectively activated and the preset system enters the working state; otherwise, it remains in sleep mode.

[0006] Preferably, the process of generating the activation signal includes: using multi-frequency shift keying technology to construct a discrete frequency library, selecting n non-repeating frequencies for the device to be activated to form a unique set of frequencies with a unique coding index; designing rectangular pulse symbols and generating a single-frequency signal sequence containing M symbols, inserting a fixed interval time between different frequency signal segments to generate the activation signal.

[0007] Preferably, the control module adjusts the incident energy, pulse width, spot radius, and incident angle of the activation signal to make the laser emitted into the activation area; The formula for the adjustment relationship is as follows: ; In the formula, Angular frequency, For incident energy, The imaginary unit, The pulse width. For sound wave number, The radius of the light spot is... For vertical viewing angle, This represents the distance to the observation point.

[0008] Preferably, the demodulation process includes: grouping the sampled signals according to the activation signal length corresponding to the preset minimum frequency to obtain multiple groups of signals; performing convolution operation on each group of signals using multi-pulse sequence signals of different frequencies to obtain the convolved signal; analyzing the time domain and frequency domain of the convolved signal, and extracting the frequency of the maximum value position as the signal frequency.

[0009] Preferably, the formula for extracting the signal frequency is: ; In the formula, For the first Frequency characteristics of the group signal For the kth g The response amplitude characteristics on the preset activation frequency template after the group signal is convolved with the multi-pulse signal of the m-th frequency sequence.

[0010] Preferably, the process of extracting the envelope and sampling to obtain the sampled signal includes: calculating the Hilbert transform of the electrical signal, combining the Hilbert transform with the electrical signal to construct an analytic signal, and obtaining the envelope of the electrical signal; sampling the envelope of the electrical signal according to the Nyquist sampling theorem to obtain the sampled signal.

[0011] Preferably, the envelope formula for an electrical signal is: ; In the formula, Electrical signal The envelope, To analyze the signal, For electrical signals, This is the Hilbert transform part of the electrical signal.

[0012] Preferably, before inputting the activation signal into the control module, a pulse signal of a fixed frequency needs to be sent to switch the device to be activated from a deep standby state to a receive state.

[0013] A second aspect of this application provides an underwater pre-positioned system activation system based on laser-induced acoustics, comprising: The preprocessing module is used to obtain the activation command of the device to be activated and uses multi-frequency shift keying technology to encode the device to be activated to generate an activation signal; The transmitting module is used to input the activation signal into the control module. The control module adjusts and emits a laser to the underwater activation area. The laser performs photoacoustic conversion at the water-air interface and transmits the acoustic signal to the device to be activated. The judgment module is used to enable the preset system to receive the acoustic signal transmitted to the device to be activated, convert it into an electrical signal, extract the envelope and sample it to obtain the sampled signal, demodulate it to obtain the signal frequency, and compare it with the preset activation frequency. If half or more of the signal frequencies match, it is determined to be validly activated and the preset system enters the working state; otherwise, it remains in sleep mode.

[0014] A third aspect of this application provides an underwater pre-set system activation device based on laser-induced acoustics, comprising: The system includes a laser modulation module, a control module, and a preset system installed underwater. The control module includes a laser and a light guide arm connected to each other. The preset system includes a signal processing unit and a device to be activated connected to each other. The device to be activated is equipped with a hydrophone, which is connected to the preset system. The laser modulation module acquires the activation command of the device to be activated and uses multi-frequency shift keying technology to encode the device to be activated to generate an activation signal. The laser in the control module receives the activation signal and adjusts the laser. It then emits the laser to the underwater activation area through the light guide arm. The laser undergoes photoacoustic conversion at the water-air interface and transmits the acoustic signal to the device to be activated. The preset system receives the acoustic signal transmitted to the device to be activated through a hydrophone, converts it into an electrical signal, performs envelope extraction and sampling to obtain the sampled signal, demodulates it in the signal processing unit to obtain the signal frequency, compares it with the preset activation frequency, if half or more of the signal frequencies match, it is determined to be effectively activated and the preset system enters the working state; otherwise, it remains in sleep mode.

[0015] The beneficial effects of this application are as follows: This application provides an underwater preset system activation method, system, and apparatus based on laser-induced acoustics. First, multi-frequency shift keying (MFS) technology is used to encode the activation command of the device to be activated. This encoding method can significantly improve the distinguishability of the signal sequence, enabling it to differentiate the activation commands of multiple devices, thereby achieving strong anti-interference capability and low bit error rate in complex underwater acoustic environments. Second, a laser is adjusted and emitted to the underwater activation area by a control module. Utilizing the photoacoustic conversion effect at the water-air interface, the laser is converted into an acoustic signal and transmitted to the device to be activated, achieving long-distance activation signal transmission. Finally, after the preset system receives the acoustic signal and converts it into an electrical signal, it first extracts the low-frequency characteristics of the electrical signal using the Hilbert transform envelope detection method, removes the high-frequency carrier component, and focuses on the main trend of signal change. Then, by extracting the envelope before sampling, the sampling rate is reduced to decrease the amount of data, significantly reducing the computational load of subsequent signal processing. Finally, convolution operation is used for demodulation, and the demodulated signal is compared with the preset activation frequency, further enhancing the anti-interference capability and ensuring the stability and accuracy of the activation process. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 A schematic diagram of the overall process of an underwater pre-positioned system activation method based on laser-induced acoustics is provided in an embodiment of this application; Figure 2 A schematic diagram of the structure of an underwater pre-set system activation device based on laser-induced acoustics is provided in one embodiment of this application; Figure 3 This is a schematic diagram of the structure of the activation signal symbol provided in an embodiment of this application; Figure 4 The waveform of the received original wake-up signal is provided in an embodiment of this application. Detailed Implementation

[0018] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0019] Please see Figure 1 The first embodiment of this application provides a method for activating an underwater pre-positioned system based on laser-induced acoustics, comprising: S1: Obtain the activation command of the device to be activated, and use multi-frequency shift keying technology to encode the device to be activated to generate an activation signal.

[0020] The pre-installed system includes One activatable device exists. This application obtains an activation command for a device to be activated in a pre-installed system. Activation command.

[0021] Devices to be activated The activation command not only includes the function of triggering startup (on), but also has a built-in function to identify the device to be activated. The encoded index. This encoded index is related to the device to be activated. Uniquely bound and can be used with other devices (such as...) , The encoding index is completely different, which directly determines the frequency combination rules of subsequent nFSK encoding.

[0022] In an optional embodiment, the device to be activated The encoded index corresponds to the frequency sequence f1-f2-f3, while the activation device The encoded index corresponds to the frequency sequence f4-f5-f6. Activation command and device to be activated. The binding logic essentially links the startup function with the device to be activated. The encoding index is deeply associated. Specifically, when generating the activation instruction, the device to be activated... The encoding index has been determined, ensuring that the activation instruction can only be used to generate commands compatible with the device to be activated. The activation signal is matched with the preset frequency rules, thereby avoiding conflicts with the frequency rules of other activation devices in the preset system and achieving targeted activation.

[0023] Using n-ary Frequency Shift Keying (nFSK) technology, n frequencies are selected from N different frequencies to encode each activation instruction. Each activation instruction contains signals of n different frequencies, and each signal segment is... Composed of several code elements with a fixed signal interval of T, an activation signal (multi-frequency pulse sequence) is generated. This application uses nFSK encoding to encode the activation command, which not only improves the distinguishability of the signal sequence but also supports the differentiated activation of multiple activation devices, providing stronger anti-interference capability and lower bit error rate in complex underwater acoustic environments.

[0024] Specifically, a discrete frequency library F={f1,f2,...,f N} is the device to be activated. Select n frequencies to form a dedicated frequency set {fx1 ,f x2 ,...,f xn} F, satisfies ≥ It is worth noting that repeatedly selecting n frequencies is not allowed, and the preset system must be guaranteed to work correctly. Each activated device has a unique encoding index. The symbol is represented by a rectangular pulse, for a frequency of f... i The time-domain expression of the k-th pulse is: ; In the formula, For a frequency of f i The time domain of the k-th pulse, The amplitude of a single high-level pulse. For time, For frequency f i The pulse period corresponding to (i=1,2,...,n) and f i =1 / , The duration of the high level. Pulse period rect(x) is a normalized rectangular window function that satisfies the condition that rect(x) = 1 when |x| < 1 / 2, and 0 otherwise. This function ensures that the impulse is within the range t ∈ [kT]. i ,kT i + The value within ] is high level A, and in t∈(kT) i + ,(k+1)T i The value inside is low level 0.

[0025] For a frequency f i Include The sequence of code elements can be represented as: ; In the formula, For a frequency of f i Include A sequence of code elements, The number of code elements. For the k-th pulse, t represents the duration of the high-level signal, where t is time.

[0026] A fixed interval T, longer than the length of each activation signal segment, is inserted between signals of different frequencies to improve signal separation. The multi-frequency pulse sequence structure is excited sequentially, forming a typical "f1-T-f2-T-...-Tf" pattern. n "The time series, the overall expression is: ; In the formula, It is a multi-frequency pulse sequence. The amplitude of a single high-level pulse. Let i be the index variable of the frequency sequence, where i is the period of a single symbol in the m-th frequency band. Let T be the period of a single symbol in the (i+1)th frequency band, where T is a fixed interval. The high-level duration is given by k, where k is the k-th pulse, t is time, and n represents n different frequencies. This represents the number of symbols contained in each frequency signal segment.

[0027] The total signal length of the multi-frequency pulse sequence is: ; In the formula, Let T be the total signal length of the multi-frequency pulse sequence, and T be a fixed interval time. Let n be the single symbol period of the i-th frequency band, and n be the n different frequencies. This represents the number of symbols contained in each frequency signal segment.

[0028] S2: Send a fixed frequency pulse signal to switch the device to be activated from deep standby state to receive state.

[0029] The system is preset to be in deep standby mode by default, and the signal receiving module is in T... a In periodic scanning mode, the receiving circuit is only briefly activated during each cycle to detect external signals, remaining in sleep mode the rest of the time. This ensures the availability of devices to be activated in the pre-installed system. It can switch from deep standby mode to receive mode. Before sending the activation signal, it needs to send a fixed frequency f. wake A wake-up pulse signal, with a duration T. wake >T a To ensure the device to be activated The signal is captured within at least one scan cycle. Device to be activated. After entering the receiving state, the scanning cycle is shortened to T. b (T) b T a It can detect external signals in real time. At this time, it sends an activation signal, ensuring that the activation signal can be reliably received by the device to be activated. Simultaneously, the device to be activated... By switching from deep standby to receiving mode on demand, the overall power consumption is effectively reduced and the system's energy efficiency is improved.

[0030] S3: Input the activation signal into the control module. The control module adjusts and emits a laser to the underwater activation area. The laser performs photoacoustic conversion at the water-air interface and transmits the acoustic signal to the device to be activated.

[0031] The generated activation signal (multi-frequency pulse sequence) is input into the laser control module. The laser in the control module precisely controls the transmission distance and directivity of the sound field by adjusting parameters such as incident energy, pulse width, spot radius, and incident angle, ensuring that the laser beam converted from the activation signal is accurately incident on the underwater activation area. After the laser beam propagates from the air to the water-air interface, it completes photoacoustic conversion at the interface due to thermal expansion. The generated acoustic signal propagates in the water along a preset direction to the device to be activated. .

[0032] Specifically, when laser light propagates from air to the water vapor interface and is refracted, the relationship between the angle of refraction and the angle of incidence is as follows: ; In the formula, The angle of refraction in water, laser beam incident angle, The refractive index of air is approximately 1. The refractive index of water is approximately 1.33.

[0033] Under the effect of thermal expansion, the relationship between the excitation sound pressure function and the modulation parameters such as propagation distance, medium parameters, and laser beam parameters is as follows: ; In the formula, The imaginary unit, Optical transmittance, The coefficient of thermal expansion is... For laser power, The optical absorption coefficient, Angular frequency, is the specific heat capacity of the liquid. The distance to the observation point, The sound wave number (w / c, where c is the speed of sound in water) For vertical viewing angle, Horizontal viewing angle The radius of the light spot is... The angle of refraction in water, For the laser pulse frequency domain, For the coupling term, the expression is as follows: ; ; In the formula, The optical absorption coefficient, These are intermediate variables used to simplify coupling terms. The expression. j is the imaginary unit. The sound wave number (w / c, where c is the speed of sound in water) For vertical viewing angle, Horizontal viewing angle The radius of the light spot is... The angle of refraction in water.

[0034] Angle of incidence The directivity of the laser-induced acoustic signal is affected, which in turn affects the activated coverage area. When the laser is incident perpendicularly to the water surface, both the incident angle and the refraction angle are 0 degrees. At this time, the excitation sound pressure function can be expressed as: ; In the formula, The imaginary unit, Optical transmittance, The coefficient of thermal expansion is... For laser power, The optical absorption coefficient, Angular frequency, is the specific heat capacity of the liquid. The distance to the observation point, The sound wave number (w / c, where c is the speed of sound in water) For vertical viewing angle, The radius of the light spot is... This refers to the laser pulse frequency domain.

[0035] The frequency domain expression of a laser pulse can be defined as: ; In the formula, The pulse width. The imaginary unit, ω is the angular frequency.

[0036] To focus on the relationship between laser parameters and acoustic signals for subsequent adjustment, the laser pulse frequency domain expression is... Substituting the sound pressure function and removing constants and angle-related terms that are independent of the laser parameters, we obtain the following formula: ; In the formula, Angular frequency, The pulse width. The imaginary unit, The sound wave number (w / c, where c is the speed of sound in water) For vertical viewing angle, Let E be the laser spot radius, E be the incident energy, and E be the laser power. =E / .

[0037] As can be seen from the formula, the incident energy E is positively correlated with the sound pressure amplitude. The larger E is, the higher the sound pressure amplitude, but it has no direct effect on the signal frequency.

[0038] Pulse width The smaller the value, the higher the sound pressure level, the wider the bandwidth, and the richer the high-frequency components; When the amplitude increases, the sound pressure level decreases and the frequency is concentrated in the low-frequency range.

[0039] Spot radius The larger the amplitude, the stronger the attenuation of the sound pressure level, and the lower the amplitude of the laser-induced sound signal; at the same time, the attenuation of the sound pressure level in the high-frequency band is more severe, and the effective frequency range of the signal will shift to lower frequencies.

[0040] In summary, signal amplitude and frequency affect the signal transmission distance underwater. Therefore, jointly adjusting the incident energy E and pulse width... Spot radius and angle of incidence It can effectively change the activation distance and activation coverage.

[0041] S4: The preset system receives the acoustic signal transmitted to the device to be activated, converts it into an electrical signal, performs envelope extraction and sampling to obtain the sampled signal, performs cropping and grouping, and uses convolution operation to demodulate the signal, extracts the frequency features of the signal, compares the demodulated frequency with the preset activation frequency, if half or more of the signal frequencies match, it is determined to be a valid activation and the preset system is triggered to enter the working state; otherwise, it remains in sleep mode.

[0042] The pre-set system receives the data transmitted to the device to be activated via a hydrophone. The acoustic signal is converted into an electrical signal. Envelope detection is used to process the received electrical signal. First, the envelope of the electrical signal is extracted, and then it is sampled to reduce computational load, resulting in a sampled electrical signal. The sampled signal is then cropped and grouped, and demodulated using convolution operations to obtain the signal frequency. The frequency of the demodulated signal is compared with a preset activation frequency. If half or more frequencies match, it is considered a valid activation, triggering the preset system to enter the working state; otherwise, it remains in sleep mode.

[0043] Specifically, the Hilbert transform envelope detection method is used to extract the electrical signal. The signal envelope, the specific formula and steps are as follows: Calculate the electrical signal according to the Hilbert transform formula. The Hilbert transform part is given by the following formula: ; In the formula, For the generated and Signals with a 90° phase difference represent electrical signals. The Hilbert transform part, For time, For electrical signals, It is the integral variable.

[0044] electrical signal Its Hilbert transformation part Combine to construct analytic signals To separate the envelope from the carrier, the formula is as follows: ; In the formula, To analyze the signal, For electrical signals, For the generated and Signals with a 90° phase difference It is the imaginary unit.

[0045] Analyzing signals The modulus is the electrical signal. The instantaneous envelope is given by the formula: ; In the formula, Electrical signal The instantaneous envelope, To analyze the signal, For electrical signals, For the generated and Signals with a 90° phase difference.

[0046] By using the Hilbert transform envelope detection method, the low-frequency characteristics of the electrical signal can be effectively extracted, and the high-frequency carrier component can be removed, which helps to extract the main trend of the electrical signal.

[0047] set up The maximum frequency is According to the Nyquist sampling theorem, the sampling frequency The following formula should be satisfied: ; In the formula, For sampling frequency, 2 This is the critical sampling frequency.

[0048] electric signal It contains high-frequency components, with its maximum frequency > For electrical signals Sampling must satisfy the sampling theorem, and its sampling rate must be... > Therefore, we have the following formula: ; In the formula, The instantaneous envelope of an electrical signal Number of sampling points per unit time. For electrical signals Number of sampling points per unit time.

[0049] Since the computational cost of subsequent signal processing (such as demodulation and feature extraction) is positively correlated with the number of sampling points, this application reduces the amount of data by first extracting the envelope and then sampling, thereby significantly reducing the computational cost.

[0050] The sampled signal is cropped and grouped, and then demodulated using convolution operations to extract the frequency features of the signal.

[0051] This application groups the sampled signals according to the activation signal length corresponding to a preset minimum frequency, since the minimum frequency f min The corresponding period T min =1 / f min The longest, therefore the length L of this activation signal segment. max This also maximizes the time-domain integrity of all frequency signals, providing a reliable foundation for subsequent demodulation.

[0052] If the valid signal is Its duration is L total The duration of each signal segment is given by the following formula: ; In the formula, The duration of a signal segment. The number of symbols contained in each signal group. The period of a single pulse.

[0053] The signal is segmented starting at t=0, and the signal is divided into segments by incrementing the time interval. The time domain range of each signal segment is: ; In the formula, For grouped signals, For the first Groups, For a valid signal, For time, The duration of a signal segment.

[0054] To ensure pulse continuity, each group must contain continuous pulses. One pulse, that is: ; In the formula, For grouped signals, For the first Groups, This is the m-th single pulse signal.

[0055] For each group of signals Convolution operations are performed using multi-pulse sequence signals of different frequencies. The convolution operation formula is as follows: ; In the formula, The signal after convolution. For a multi-pulse signal with the m-th frequency sequence, it is represented as: ; In the formula, The pulse amplitude. It is the number of pulses. For time, For index variables, Let m be the period of a single pulse, and m be different frequency sequences. For phase shifts of different frequency sequences, The duration of the high-level signal.

[0056] Convolutional signal After analysis in the time and frequency domains, the frequency of the maximum value is extracted as the frequency feature of the signal. The formula for frequency extraction is as follows: ; In the formula, For the first The frequency characteristics of a signal group represent the frequency corresponding to the maximum amplitude in the signal spectrum. For the first The response amplitude characteristics on the preset activation frequency template after the group signal is convolved with the multi-pulse signal of the m-th frequency sequence.

[0057] The demodulated frequency is compared with the preset activation frequency. If half or more of the signal frequencies match, it is determined to be a valid activation, triggering the preset system to enter the working state; otherwise, it remains in sleep mode.

[0058] Specifically, the frequency of each group of signals obtained by demodulation The frequency error is calculated by comparing it with the preset activation frequency, using the following formula: ; In the formula, This represents the absolute difference in frequencies between the two sets of signals. The first convolution is the result of... The frequency of the group signal, This is the preset activation frequency.

[0059] like < ,(in, (If the preset frequency difference threshold is used), then the first... The frequency of the group signals matches the preset activation frequency. When the frequency of at least half of the signals matches the preset activation frequency, it is considered validly activated, as shown in the formula: ; In the formula, This represents the absolute difference in frequencies between the two sets of signals. is the preset frequency difference threshold, and n is the total number of signal groups.

[0060] The second embodiment of this application provides an underwater pre-set system activation system based on laser-induced acoustics, comprising: The preprocessing module is used to acquire the activation command of the device to be activated, and uses multi-frequency shift keying technology to encode the device to be activated to generate an activation signal; it sends a fixed frequency pulse signal to change the device to be activated from a deep standby state to a ready-to-receive state. The transmitting module is used to input the activation signal into the control module. The control module adjusts and emits a laser to the underwater activation area. The laser performs photoacoustic conversion at the water-air interface and transmits the acoustic signal to the device to be activated. The activation module is used to enable the preset system to receive the acoustic signal transmitted to the device to be activated, convert it into an electrical signal, extract the envelope and sample the sampled signal, trim and group it and demodulate it using convolution operation. The obtained signal frequency is compared with the preset activation frequency. If half or more of the signal frequencies match, it is determined to be a valid activation and the preset system is triggered to enter the working state; otherwise, it remains in sleep mode.

[0061] Please see Figure 2 The third embodiment of this application provides an underwater preset system activation device based on laser acoustics, which includes a laser modulation module, a control module, and a preset system installed underwater. The control module includes a laser and a light guide arm connected to each other, and the preset system includes a signal processing unit and a device to be activated connected to each other. The device to be activated is equipped with a hydrophone.

[0062] The laser modulation module acquires the activation command of the device to be activated, uses multi-frequency shift keying technology to encode the device to be activated to generate an activation signal, sends a fixed frequency pulse signal to change the device to be activated from a deep standby state to a ready-to-receive state, and inputs the activation signal into the control module.

[0063] Specifically, the laser modulation module acquires the device to be activated. The activation command in this embodiment uses 3FSK technology to activate the underwater pre-set system, and selects three frequencies—50Hz, 100Hz, and 125Hz—from multiple frequency groups for the device to be activated. The activation is constructed by creating an activation signal segment with a symbol length of 10 (each segment contains 10 consecutive rectangular pulses, and the pulse high level duration is...). The pulse periods for each frequency are 20ms, 10ms, and 8ms respectively. The interval between different frequency signals is designed as T, generating a complete activation signal of "f1-T-f2-T-f3". The activation signal symbol structure is as follows: Figure 3 As shown. Before sending the activation signal, a pulse signal with a fixed frequency of 20Hz and a duration of 5s is sent to ensure the device to be activated is activated. Switching from deep standby mode to receive mode will activate the signal input control module.

[0064] The laser in the control module receives the activation signal and adjusts the light guide arm to emit the laser to the underwater activation area. The laser performs photoacoustic conversion at the water-air interface and transmits the acoustic signal to the device to be activated.

[0065] Specifically, after receiving the activation signal, the laser in the control module adjusts its laser beam, controlling it to emit laser light sequentially through the light guide arm at frequencies f1, f2, and f3 to the underwater activation area. The laser parameters are set as follows: single-pulse energy E, pulse width... Spot radius By controlling the laser to be incident perpendicularly onto the water-air interface, i.e., at an incident angle of 0°, according to the law of refraction, the refractive index of air... 1. Water refractive index The value is 1.33, and the refraction angle is synchronously 0°. The laser beam is incident on the water-air interface, and the photoacoustic conversion is completed through the thermal expansion effect. The acoustic signal propagates in the water to the device to be activated. Hydrophone.

[0066] The preset system receives the acoustic signal transmitted to the device to be activated through a hydrophone, converts it into an electrical signal, performs envelope extraction and sampling to obtain the sampled signal, demodulates it in the signal processing unit to obtain the signal frequency, compares it with the preset activation frequency, if half or more of the signal frequencies match, it is determined to be effectively activated and the preset system enters the working state; otherwise, it remains in sleep mode.

[0067] Specifically, the pre-set system receives the data transmitted to the device to be activated via a hydrophone. The acoustic signal is converted into an electrical signal, and then the signal envelope is extracted using Hilbert transform envelope detection and sampled again (the highest frequency of the envelope is f). e =30kHz, sampling rate f is taken according to the Nyquist sampling criterion. s=60kHz). The sampled signal is sent to the signal processing unit. The signal processing unit trims and groups the sampled signal according to the signal length period corresponding to the minimum frequency of 50Hz, and performs convolution demodulation using preset activation frequencies of 50Hz, 100Hz, and 125Hz. If at least two of the three demodulated signal segments match the preset activation frequencies, it is determined to be a valid activation, triggering the preset system to enter the working state, thereby completing the activation verification; otherwise, it remains in sleep mode.

[0068] Please see Figure 4 The figure shows the acoustic signal waveforms received by the hydrophone in a laboratory environment of this embodiment at frequencies of 125Hz, 100Hz, and 50Hz, respectively, which are devices to be activated. The received signals. As can be seen from the figure, the waveforms of each frequency signal are regular and clear, unaffected by environmental interference, which intuitively verifies the actual receptivity of the signal and also intuitively proves that the activation signal generated by this application has good anti-interference ability and can achieve reliable activation.

[0069] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software 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.

[0070] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A method for activating an underwater pre-positioned system based on laser-induced acoustics, characterized in that, Includes the following steps: Obtain the activation command of the device to be activated, and use multi-frequency shift keying technology to encode the device to be activated to generate an activation signal; The activation signal is input to the control module, which adjusts and emits a laser to the underwater activation area. The laser performs photoacoustic conversion at the water-air interface and transmits an acoustic signal to the device to be activated. The preset system receives the acoustic signal transmitted to the device to be activated, converts it into an electrical signal, performs envelope extraction and sampling to obtain the sampled signal, demodulates it to obtain the signal frequency, and compares it with the preset activation frequency. If half or more of the signal frequencies match, it is determined to be effectively activated, and the preset system enters the working state; otherwise, it remains in sleep mode.

2. The underwater pre-positioned system activation method based on laser-induced acoustics as described in claim 1, characterized in that, The process of generating the activation signal includes: using multi-frequency shift keying technology to construct a discrete frequency library, selecting n non-repeating frequencies for the device to be activated to form a unique frequency set with a unique coding index; designing rectangular pulse symbols and generating a single-frequency signal sequence containing M symbols, inserting a fixed interval time between different frequency signal segments to generate the activation signal.

3. The underwater pre-positioned system activation method based on laser-induced acoustics as described in claim 1, characterized in that, The control module adjusts the incident energy, pulse width, spot radius, and incident angle of the activation signal to make the laser emitted into the activation region; The formula for the adjustment relationship is as follows: ； In the formula, Angular frequency, For incident energy, The imaginary unit, The pulse width. For sound wave number, The radius of the light spot is... For vertical viewing angle, This represents the distance to the observation point.

4. The underwater pre-positioned system activation method based on laser-induced acoustics as described in claim 1, characterized in that, The demodulation process includes: grouping the sampled signal into multiple groups according to the activation signal length corresponding to the preset minimum frequency; performing convolution operation on each group of signals using multi-pulse sequence signals of different frequencies to obtain the convolved signal; analyzing the time domain and frequency domain of the convolved signal, and extracting the frequency of the maximum value position as the signal frequency.

5. The underwater pre-positioned system activation method based on laser-induced acoustics as described in claim 4, characterized in that, The formula for extracting the signal frequency is: ； In the formula, For the first Frequency characteristics of the group signal For the kth g The response amplitude characteristics on the preset activation frequency template after the group signal is convolved with the multi-pulse signal of the m-th frequency sequence.

6. The underwater pre-positioned system activation method based on laser-induced acoustics as described in claim 1, characterized in that, The process of extracting the envelope and sampling to obtain the sampled signal includes: calculating the Hilbert transform of the electrical signal, combining the Hilbert transform with the electrical signal to construct an analytic signal, and obtaining the envelope of the electrical signal; sampling the envelope of the electrical signal according to the Nyquist sampling theorem to obtain the sampled signal.

7. The underwater pre-positioned system activation method based on laser-induced acoustics as described in claim 6, characterized in that, The envelope formula for the electrical signal is: ； In the formula, Electrical signal The envelope, To analyze the signal, For electrical signals, This is the Hilbert transform part of the electrical signal.

8. The underwater pre-positioned system activation method based on laser-induced acoustics as described in claim 1, characterized in that, Before inputting the activation signal into the control module, a pulse signal of a fixed frequency needs to be sent to change the device to be activated from a deep standby state to a ready-to-receive state.

9. A laser-induced acoustic underwater pre-positioning system activation system, applied to the laser-induced acoustic underwater pre-positioning system activation method according to any one of claims 1-8, characterized in that, The preprocessing module is used to obtain the activation command of the device to be activated and to encode the device to be activated using multi-frequency shift keying technology to generate an activation signal. The transmitting module is used to input the activation signal into the control module. The control module adjusts and emits a laser to the underwater activation area. The laser performs photoacoustic conversion at the water-air interface and transmits an acoustic signal to the device to be activated. The judgment module is used to enable the preset system to receive the acoustic signal transmitted to the device to be activated, convert it into an electrical signal, perform envelope extraction and sampling to obtain the sampled signal, demodulate it to obtain the signal frequency, and compare it with the preset activation frequency. If half or more of the signal frequencies match, it is determined to be effectively activated and the preset system enters the working state; otherwise, it remains in sleep mode.

10. An underwater pre-positioning system activation device based on laser-induced acoustics, applied to the underwater pre-positioning system activation method based on laser-induced acoustics as described in any one of claims 1-8, characterized in that, include: The system includes a laser modulation module, a control module, and a preset system installed underwater. The control module includes a laser and a light guide arm connected to each other. The preset system includes a signal processing unit and a device to be activated connected to each other. The device to be activated is equipped with a hydrophone, which is connected to the preset system. The laser modulation module acquires the activation command of the device to be activated and uses multi-frequency shift keying technology to encode the device to be activated to generate an activation signal; The laser in the control module receives the activation signal to adjust the laser, and emits the laser to the underwater activation area through the light guide arm. The laser performs photoacoustic conversion at the water-air interface and propagates the acoustic signal to the device to be activated. The preset system receives the acoustic signal transmitted to the device to be activated through the hydrophone, converts it into an electrical signal, performs envelope extraction and sampling to obtain the sampled signal, demodulates it in the signal processing unit to obtain the signal frequency, compares it with the preset activation frequency, if half or more of the signal frequencies match, it is determined to be effectively activated and the preset system enters the working state; otherwise, it remains in sleep mode.

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