Dynamic sonar scanning system and method based on frequency and angle coding

Abstract

The invention relates to the technical field of sonar analysis, in particular to a dynamic sonar scanning system and method based on frequency and angle coding, and the method comprises the steps: driving a transducer to continuously rotate around a shaft, transmitting sound wave signals to a plurality of preset sectors, collecting echo signals reflected by a target, and generating a rotation angle feedback signal of the transducer; a current scanning sector is determined according to the rotation angle feedback signal, angle information of the sector is coded into unique corresponding emission frequencies, and the starting time and the duration time of each emission frequency are recorded to form a frequency coding time sequence; determining a transmission mode based on a historical accumulated value of the rotation angle feedback signal, the transmission mode including a dynamic switching mode and a parallel transmission mode; calculating a target distance according to the frequency coding time sequence and distance calculation methods corresponding to different transmitting modes; decoupling of the mechanical rotating speed and the scanning process and signal interference caused by high-speed rotation are completed through angle feedback and mode self-adaptive switching of the transducer.

Description

Technical Field

[0001] The present invention relates to the technical field of sonar analysis, and specifically to a dynamic sonar scanning system and method based on frequency and angle encoding. Background Art

[0002] Traditional rotary mechanical scanning sonars have two major bottlenecks: First, the scanning frame rate is strongly coupled with the mechanical rotation speed of the transducer. Although increasing the rotation speed can accelerate the scanning speed, it will cause incomplete coverage of the transmitted signal due to the rotation gap, resulting in the loss or blurring of the target echo. Especially in the scenario of high-speed underwater movement, the target dynamic tracking ability is limited. Second, the Doppler frequency shift caused by high-speed rotation seriously reduces the signal-to-noise ratio of the echo signal, and the acoustic wave signals in multiple sectors are prone to interfere with each other, resulting in a decrease in ranging and direction-finding accuracy.

[0003] Although existing electronic scanning technologies can partially overcome mechanical limitations, their high costs and complex signal processing algorithms are difficult to apply to wide-coverage and low-cost scenarios. Therefore, there is an urgent need for a sonar scanning technology solution that can simultaneously achieve high-speed motion adaptability, high detection accuracy, and anti-interference ability. Summary of the Invention

[0004] The purpose of the present invention is a dynamic sonar scanning system and method based on frequency and angle encoding to solve the problems raised in the above background art. The specific technical problems include the strong coupling between the mechanical rotation speed and the scanning frame rate, resulting in limited scanning speed or the inability to have both data integrity and resolution; and the Doppler frequency shift and multi-sector signal interference caused by high-speed rotation, reducing the ranging and direction-finding accuracy.

[0005] To achieve the above purpose, one of the purposes of the present invention is a dynamic sonar scanning system based on frequency and angle encoding, including a transducer module, a transmission control module, and a reception processing module, where The transducer module realizes continuous rotation through a closed-loop drive mechanism, generates a rotation angle feedback signal through a built-in rotary encoder, and uses a transmitting unit to transmit acoustic wave signals to multiple equally-angled divided sectors. Each sector is bound to a unique frequency or an orthogonal encoding waveform to form a sector-based directional coverage ability; it provides a real-time spatial angle reference for transmission and reception, and establishes a direct mapping relationship of "physical pointing → frequency encoding" to lay the foundation for rotational speed decoupling.

[0006] The transmission control module maps the current sector in real time based on the rotation angle feedback signal, encodes the central angle of the sector into a unique transmission frequency, and allocates frequencies using a linearly increasing frequency interval and orthogonal waveforms to ensure that the signals in each sector do not interfere with each other. For example, a linear frequency modulation signal The mathematical formula is: , where is the signal amplitude; is the starting frequency; is the frequency modulation slope (unit: Hz / s, >0 means up-conversion, <0 means down-conversion); is the time variable is the imaginary unit, used to construct the signal expression in complex form and simplify the phase and frequency domain analysis; Record the start time and duration of each transmission frequency to form a frequency encoding time sequence, and record the global synchronization time reference for the parallel transmission mode; Count the cumulative rotation angle within a unit time, compare it with the preset rotation angle threshold to determine the transmission mode, where the transmission mode includes a dynamic switching mode and a parallel transmission mode. In the dynamic switching mode, when the transducer rotates to a sector, it triggers the emission of corresponding frequency pulses, and a time domain guard interval is inserted between adjacent sectors to avoid echo and transmission pulse aliasing; The parallel transmission mode synchronously transmits multi-frequency signals covering all sectors through orthogonal coding technology, breaking through the traditional pulse interval limit and supporting omnidirectional instantaneous coverage under high-speed rotation; Decouple the mechanical rotation speed and the signal time sequence through real-time angle-to-frequency encoding, and the mode adaptive switching takes into account the requirements of low-speed high-resolution and high-speed full coverage.

[0007] In the dynamic switching mode, the receiving and processing module separates the single frequency components of each sector through a bandpass filter bank or digital down-conversion technology; In the parallel transmission mode, it uses a matched filter bank or time-frequency analysis algorithm to separate the orthogonal coded multi-frequency signals; According to the preset frequency and angle mapping table, map the frequency components to the central angle of the corresponding sector and calculate the target direction angle; Among them: In the dynamic switching mode, the pulse delay method is used to calculate the target distance , and the formula is as follows: , where is the speed of sound, is the arrival time of the echo signal corresponding to the frequency encoding time sequence; In the parallel transmission mode, the frequency modulation continuous wave difference frequency method is used to calculate the target distance through the frequency difference between the echo signal and the reference signal , and the formula is as follows: , where is the frequency modulation slope.

[0008] Combine the target direction angle and the calculated target distance to jointly form the polar coordinates of the target and achieve precise positioning of the target in two-dimensional or three-dimensional space; Break through the fixed resolution limit of mechanical scanning angle calculation, eliminate multi-frequency interference, and achieve target positioning with centimeter-level to meter-level accuracy under all working conditions.

[0009] The second object of the present invention is a method for a dynamic sonar scanning system based on frequency and angle encoding, including the following method steps: S1. Rotate the drive transducer continuously around an axis and transmit acoustic wave signals to multiple preset sectors to collect the echo signals reflected by the target and generate a rotation angle feedback signal of the transducer; S2. Determine the current scanning sector according to the rotation angle feedback signal, encode the angle information of this sector into a uniquely corresponding transmission frequency, record the start time and duration of each transmission frequency, and form a frequency encoding time sequence; based on the historical cumulative value of the rotation angle feedback signal, determine the transmission mode, where the transmission mode includes a dynamic switching mode and a parallel transmission mode; S3. Calculate the target distance according to the frequency encoding time sequence and the distance calculation methods corresponding to different transmission modes.

[0010] Compared with the prior art, the beneficial effects of the present invention are: By dynamically binding the physical angle and frequency encoding, decouple the strong coupling relationship between the mechanical rotation speed and the scanning frame rate, so that the system can achieve non-missing detection within a wide rotation speed range; the dynamic switching mode and the parallel transmission mode are adaptively switched, taking into account the centimeter-level high-precision ranging in low-speed scenarios and the omnidirectional instantaneous coverage requirements in high-speed scenarios; combined with orthogonal encoding signal separation, suppress multi-frequency interference and frequency offset errors, and improve the target positioning accuracy in complex motion environments. Description of the Drawings

[0011] Figure 1 It is a schematic diagram of the overall module of the present invention; Figure 2 It is a schematic diagram of the overall method flow of the present invention.

[0012] In the figure: 100, transducer module; 200, transmission control module; 300, reception and processing module. Detailed Embodiments

[0013] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0014] Next, please refer to Figure 1 , one of the purposes of this embodiment is a dynamic sonar scanning system based on frequency and angle encoding, including a transducer module 100, a transmission control module 200, and a reception and processing module 300.

[0015] The transducer module 100 is used to drive the transducer to rotate continuously around the axis. By integrating a high-precision rotation drive unit (such as a brushless motor or a stepper motor), the transducer is driven to rotate continuously around the central axis through a closed-loop control system to ensure stability under uniform or variable speed motion; it supports dynamic speed adjustment (for example, 10-120RPM) to adapt to different scanning scene requirements (fast coverage or high-resolution detection).

[0016] The transducer module 100 transmits acoustic wave signals to multiple preset sectors by dividing the 360° scanning range into N equal-angle sectors (such as N=24, 15° per sector), and each sector is assigned a unique identifier; when the transducer rotates to a certain sector, the transmitting unit generates an acoustic wave signal bound to the sector; the signal center frequency, bandwidth, pulse width and other parameters are programmable and support linear frequency modulation (LFM) or phase coded modulation.

[0017] The transducer module 100 collects the echo signal reflected by the target, receives the echo signal in real time through an integrated high-sensitivity hydrophone array, and performs signal conditioning through a low-noise amplifier and a bandpass filter; an analog-to-digital converter is used to sample the echo signal with a dynamic range of ≥80dB and a sampling rate matching the signal bandwidth (e.g., 100kHz-1MHz); based on the timestamp of the transmitted signal, the echo acquisition window is triggered to ensure signal alignment.

[0018] The transducer module 100 generates a rotation angle feedback signal of the transducer, measures the transducer rotation angle in real time through a built-in absolute rotary encoder or inertial measurement unit (IMU), and outputs a digital pulse signal (such as generating a pulse for every 0.1° rotation) as a rotation angle feedback signal, which is strictly synchronized with the mechanical position of the transducer; the angle feedback signal is transmitted to the transmission control module 200 to trigger the frequency transmission of the corresponding sector (dynamic switching mode) or multi-frequency synchronous timing calibration (parallel transmission mode).

[0019] The transmitting control module 200 receives the rotation angle feedback signal (such as a digital pulse or continuous angle value every 0.1°) output by the transducer module 100; based on a preset sector division rule (such as N=24 sectors, 15° per sector), the current angle value is mapped to a corresponding sector identifier (such as sector k, k=1, 2, ..., N); Example: If the angle feedback is 37.5° and the sector width is 15°, the current sector is determined to be the third sector (37.5° / 15°=2.5, k=3 after rounding); The transmission control module 200 allocates transmission frequencies to sectors by using linear incremental frequency intervals and orthogonal waveforms, by allocating a unique corresponding transmission frequency fk=f0+kΔf to sector k, where f0 is the base frequency and Δf is the frequency interval (e.g., f0=100kHz, Δf=5kHz); and allocating orthogonal waveforms to sector k ensures that multi-sector signals do not interfere with each other. When the transducer rotates to sector k, the start time and duration (usually pulse width or frequency modulation period) of the transmission frequency fk corresponding to the sector are recorded; Record the global synchronization time base of all orthogonal coded frequencies to ensure the timing alignment of multi-frequency signal transmission and reception; The start time and duration of each transmission frequency are used as the frequency encoding timing.

[0020] The transmission control module 200 determines the transmission mode based on the historical cumulative value of the rotation angle feedback signal; by counting the cumulative rotation angle of the transducer in a unit time (such as the total rotation angle per second); if the cumulative rotation angle exceeds the set rotation angle threshold (such as 360° / second), it is determined to be a high-speed scanning scene and the parallel transmission mode is enabled; if the cumulative rotation angle is lower than the set rotation angle threshold, it is determined to be a low-speed scene and the dynamic switching mode is enabled; wherein: The parallel transmission mode uses orthogonal coding technology to simultaneously cover the multi-frequency signal transmission of all preset sectors. During the high-speed rotation of the transducer, the transmission control module 200 uses the global synchronization time reference to simultaneously drive the transducer to transmit the orthogonal waveforms corresponding to all sectors (such as linear frequency modulation signal groups, with different frequency modulation slopes assigned to each sector); this mode breaks through the traditional pulse interval limitation, supports high-speed rotation of the transducer, and realizes instantaneous coverage of omnidirectional scanning, but it needs to sacrifice some resolution in exchange for scanning efficiency, and relies on high dynamic range receiving channels and complex signal processing algorithms to suppress multi-frequency interference; The dynamic switching mode is a working mode that triggers frequency transmission sector by sector based on the mechanical rotation angle of the transducer. When the transducer rotates continuously, the transmission control module 200 accurately determines the sector it is currently pointing to (such as sector k) by receiving the rotation angle feedback signal in real time, and immediately switches to the unique transmission frequency fk bound to the sector; the transmission behavior of each sector is completed in the form of a pulse, and its duration is consistent with the pulse width or frequency modulation period, and a time domain protection interval is inserted when adjacent sectors are switched to avoid time domain aliasing of the echo signal and the next sector transmission pulse; this mode is suitable for low-speed scenarios, and ensures high-resolution detection of each sector through sequential scanning, but because it is necessary to wait for the transducer to rotate to the target sector, the scanning speed is limited by the product of the mechanical rotation speed and the number of sectors.

[0021] The receiving and processing module (300) identifies the transmission frequency components corresponding to each sector from the echo through signal separation technology (such as bandpass filtering in dynamic switching mode or orthogonal waveform matching in parallel mode); maps each frequency component to the center angle of the sector to which it is bound according to a preset frequency and angle mapping table, and calculates the target direction angle in combination with the real-time rotation angle feedback of the transducer, thereby achieving unambiguous positioning of the target direction.

[0022] The receiving and processing module 300 calculates the target distance according to the frequency encoding timing sequence and the distance calculation method corresponding to different transmission modes, specifically including: Based on the frequency encoding timing sequence provided by the transmission control module 200 (recording the start time and duration of each frequency), calculate the arrival time of the echo signal; in the dynamic switching mode, use the pulse delay method to calculate the target distance , the formula is as follows :, where is the speed of sound, is the arrival time of the echo signal corresponding to the frequency encoding timing sequence; In the parallel transmission mode, use the frequency-modulated continuous wave difference frequency method to calculate the target distance through the frequency difference between the echo signal and the reference signal , the formula is as follows: , where is the frequency modulation slope.

[0023] The receiving and processing module 300 combines the target direction angle with the calculated target distance to jointly form the polar coordinates of the target, realizing the precise positioning of the target in two-dimensional or three-dimensional space.

[0024] In addition, in a low-speed scenario, use a high-resolution pulse signal, combined with a time-domain guard interval, to ensure that there is no aliasing of the echo signal, and the ranging accuracy reaches the centimeter level; In a high-speed scenario, through orthogonal signal separation and Doppler compensation algorithms (based on the rotational angular velocity of the transducer), suppress the frequency offset caused by high-speed rotation and improve the signal-to-noise ratio.

[0025] Please refer to Figure 2 , the second object of this embodiment is to provide a method for a dynamic sonar scanning system based on frequency and angle encoding, including the following method steps: S1. Drive the transducer to continuously rotate around an axis and emit acoustic wave signals to multiple preset sectors to collect the echo signals reflected by the target and generate a rotational angle feedback signal of the transducer; S2. Determine the current scanning sector according to the rotational angle feedback signal, encode the angle information of this sector into a uniquely corresponding transmission frequency, record the start time and duration of each transmission frequency, and form a frequency encoding timing sequence; based on the historical cumulative value of the rotational angle feedback signal, determine the transmission mode, where the transmission mode includes a dynamic switching mode and a parallel transmission mode; S3. Calculate the target distance according to the frequency encoding timing sequence and the distance calculation method corresponding to different transmission modes.

[0026] The foregoing has shown and described the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments, and the above embodiments and the descriptions in the specification are only preferred examples of the present invention, and are not used to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A dynamic sonar scanning system based on frequency and angle coding, characterized in that: It comprises a transducer module (100), a transmission control module (200) and a reception processing module (300), wherein: The transducer module (100) is used to drive the transducer to continuously rotate around an axis and transmit sound wave signals to a plurality of preset sectors to collect echo signals reflected by a target and generate a rotation angle feedback signal of the transducer; The transmission control module (200) is used to determine the current scanning sector according to the rotation angle feedback signal, and encode the angle information of the sector into a unique corresponding transmission frequency, record the start time and duration of each transmission frequency, and form a frequency encoding time sequence; based on the historical accumulated value of the rotation angle feedback signal, establish a transmission mode of the adaptive switching mechanism, wherein the transmission mode includes a dynamic switching mode and a parallel transmission mode; The receiving processing module (300) calculates the target distance according to the frequency coding timing and the distance calculation methods corresponding to different transmission modes.

2. The dynamic sonar scanning system based on frequency and angle coding according to claim 1 is characterized in that: The multiple preset sectors are implemented by dividing the scanning range into equal-angle sectors, wherein each sector is assigned a unique identifier, and the number of sectors and the angle range are configurable.

3. The dynamic sonar scanning system based on frequency and angle coding according to claim 1, characterized in that: The transmission control module (200) allocates a unique corresponding transmission frequency to each sector, and the transmission frequency is allocated in a linear incremental frequency interval and orthogonal waveform manner to ensure that the signals of each sector do not interfere with each other.

4. The dynamic sonar scanning system based on frequency and angle coding according to claim 1, characterized in that: The transmission control module (200) determines whether to enable the dynamic switching mode or the parallel transmission mode by counting the cumulative rotation angle of the transducer within a unit time and comparing it with a preset rotation angle threshold.

5. The dynamic sonar scanning system based on frequency and angle coding according to claim 1, characterized in that: In the dynamic switching mode, the transmission control module (200) inserts a time domain guard interval when switching between adjacent sectors to avoid time domain aliasing of the echo signal and the transmission pulse.

6. The dynamic sonar scanning system based on frequency and angle coding according to claim 1, characterized in that: In the parallel transmission mode, the transmission control module (200) synchronously drives the transmission of multi-frequency signals covering all sectors through orthogonal coding technology, and records the global synchronization time reference.

7. The dynamic sonar scanning system based on frequency and angle coding according to claim 1, characterized in that: The receiving and processing module (300) extracts each frequency component from the echo signal and calculates the target direction angle according to a preset frequency and angle mapping table.

8. The dynamic sonar scanning system based on frequency and angle coding according to claim 1, characterized in that: The receiving processing module (300) calculates the target distance based on the pulse delay method in the dynamic switching mode , the formula is as follows: ,in is the speed of sound, It is the arrival time of the echo signal corresponding to the frequency encoding timing.

9. The dynamic sonar scanning system based on frequency and angle coding according to claim 1, characterized in that: The receiving processing module (300) is in parallel transmission mode, based on the frequency modulation continuous wave difference frequency method, using the frequency difference between the echo signal and the reference signal Calculate target distance , the formula is as follows: ,in is the frequency modulation slope.

10. A method for using the dynamic sonar scanning system based on frequency and angle coding according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: S1, driving the transducer to continuously rotate around the axis and emitting acoustic wave signals to a plurality of preset sectors to collect echo signals reflected by the target and generate a rotation angle feedback signal of the transducer; S2. Determine the current scanning sector according to the rotation angle feedback signal, and encode the angle information of the sector into a unique corresponding transmission frequency, record the start time and duration of each transmission frequency, and form a frequency encoding timing sequence; determine the transmission mode based on the historical cumulative value of the rotation angle feedback signal, wherein the transmission mode includes a dynamic switching mode and a parallel transmission mode; S3. Calculate the target distance according to the frequency coding timing and the distance calculation method corresponding to different transmission modes.

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