Horizontal directivity measuring device and method of multi-beam side-scan sonar

Abstract

The invention relates to the technical field of sonar, in particular to a horizontal directivity measuring device and method of multi-beam side-scan sonar. The device comprises a display controller, a first lifting mechanism and a second lifting mechanism, the first lifting mechanism comprises a rotary table and a side-scan sonar array, the second lifting mechanism comprises a rotary table and a transducer, one end of the display controller is connected with the rotary table of the first lifting mechanism, and the other end of the display controller is connected with the transducer of the second lifting mechanism through a signal generator. A power amplifier is arranged between the signal generator and the transducer, the display controller controls the signal generator to generate an emission signal, the emission signal of the signal generator is sent to the power amplifier, and the power amplifier amplifies the received signal, then sends the amplified signal to the transducer and emits an acoustic signal; the display control communicates with the dry end of the side-scan sonar, the dry end controls the side-scan sonar array to receive a transmitting signal of a transducer under the triggering of a synchronizing signal of the signal generator, the transducer and the array are located underwater, and other devices are located on water.

Description

Technical Field

[0001] The invention relates to the technical field of sonar, and in particular to a device and method for measuring the horizontal directivity of a multi-beam side-scan sonar. Background Art

[0002] Side scan sonar is a type of imaging sonar and is the main equipment for landform measurement. It has the advantages of high resolution, continuous acquisition of two-dimensional seabed images, and low price. It is widely used in marine surveying and mapping, marine geological surveys, marine engineering exploration, underwater search and rescue, underwater archaeology, and marine military. The principle of side scan sonar is to form a narrow strip beam perpendicular to the towing direction. The beam is a narrow beam in the track direction and a wide beam in the plane perpendicular to the track. When the sonar moves along the towing direction, it periodically transmits and receives sound pulses to obtain echoes from a narrow strip of seabed area illuminated by the beam. The echoes of different emission cycles are spliced ​​together along the towing direction to form a seabed landform image. The horizontal directivity of side scan sonar is an important indicator of side scan sonar, which determines the track resolution of side scan sonar and is an important factor affecting the imaging quality and target detection performance of side scan sonar. With the deepening of ocean development, the performance requirements of side-scan sonar are getting higher and higher. In order to improve the resolution of the track, a higher working frequency and array length are adopted. The working range of the side-scan sonar includes the near-field area. In order to obtain good track resolution in the near-field area, near-field focusing is usually performed. The beam width in the track direction, that is, the horizontal directivity of the side-scan sonar, is an important indicator of the side-scan sonar. It determines the resolution of the side-scan sonar in the track direction and is an important factor affecting the imaging quality and target detection performance of the side-scan sonar.

[0003] The current methods for measuring the horizontal directivity of side-scan sonar mainly include the following two methods: one is that engineers infer the horizontal directivity of side-scan sonar based on the designed sonar array length and empirical formula, but due to the position error of the sonar array elements, amplitude and phase deviation and other reasons, the actual horizontal directivity of the side-scan sonar has a certain deviation from the empirical formula. In addition, this method is generally used to calculate the far-field directivity of sonar. The other is to use a measurement system to measure in an anechoic pool or lake, using a sound source to emit a single-frequency signal of a specific frequency, and process it by listening to a single beam at the measured direction, control the turntable to rotate a small angle, and manually read the direction information after stabilization, and manually read the amplitude output of the receiving hydrophone, and finally draw a directivity diagram.

[0004] The existing directivity measurement method mainly uses the sonar array to measure directly, which is unable to measure the near-field horizontal directivity after near-field focusing. Therefore, a multi-beam side-scan sonar horizontal directivity measurement method is urgently needed to solve the problem that the existing method cannot measure the near-field horizontal directivity after near-field focusing. Summary of the invention

[0005] The problem to be solved by the present invention is to provide a device and method for measuring the horizontal directivity of a multi-beam side-scan sonar.

[0006] In view of the deficiencies of the prior art, the present invention adopts the following technical solution to solve the technical problems: a horizontal directivity measuring device for a multi-beam side-scan sonar, the device comprising a display and control, a first lifting mechanism and a second lifting mechanism, the first lifting mechanism comprising a turntable and a side-scan sonar array, the second lifting mechanism comprising a turntable and a transducer, one end of the display and control is connected to the turntable of the first lifting mechanism, and the other end is connected to the transducer of the second lifting mechanism through a signal generator, a power amplifier is arranged between the signal generator and the transducer, the display and control controls the signal generator to generate a transmitting signal, the transmitting signal of the signal generator is given to the power amplifier, the power amplifier amplifies the received signal and gives it to the transducer and emits an acoustic signal; the display and control communicate with the dry end of the side-scan sonar, the dry end controls the transmitting signal of the receiving transducer of the side-scan sonar array under the triggering of the synchronization signal of the signal generator, the transducer and the array are located underwater, and the remaining equipment is located above water.

[0007] A method for measuring the horizontal directivity of a multi-beam side-scan sonar comprises the following steps:

[0008] Step 1: Connect the side scan sonar to be tested to the measuring device and adjust the power amplifier to ensure sufficient signal-to-noise ratio for reception;

[0009] Step 2: Automatically align the array center and the transmitting transducer;

[0010] Step 3: Automatically adjust the array orientation to align the array center beam with the transducer;

[0011] Step 4: Adjust the array position so that the center of the beam to be measured is aligned with the transducer, and automatically measure the horizontal directivity of the first beam;

[0012] Step 5: Adjust the array position and repeat step 4 to complete the horizontal directivity measurement of all beams.

[0013] Preferably, in step one, the side scan sonar array is perpendicular to the water surface, the transducer and the side scan sonar array are immersed in the water at the same depth, and the power amplifier is adjusted to a suitable amplification factor so that the side scan sonar receiving signal has a high signal-to-noise ratio and is saturated, and the side scan sonar only receives but does not transmit.

[0014] Preferably, the transmission signal generated by the signal generator in step 2 is amplified by the power amplifier to excite the transducer to emit an acoustic signal, and at the same time, the signal generator generates a synchronization signal of the transmission signal to trigger the side scan sonar to start collecting, and the side scan sonar converts the array element domain data s array Upload, calculate and record the distance r from the transducer to the wet end of the side scan sonar based on the array element domain data of the array element at the geometric center of the array. If the number of array elements M is an odd number, the array element domain s of the center array element centre for:

[0015]

[0016] If the number of array elements M is an even number, the average value of the array domain data of the two middle array elements is used instead, that is:

[0017]

[0018] Preferably, in step three, the display and control controls the first lifting mechanism to move along the X-axis to -(M-1)*d / 2, where M is the number of side-scan sonar array elements and d is the array element spacing; then the first lifting mechanism is controlled to rotate from -10° to 10°, with each step being dθ. After the rotation is in place, the display and control controls the signal generator to emit a pulse signal of the center frequency of the side-scan sonar and simultaneously sends working parameters to the side-scan sonar. The display and control calculates the signal strength amp and angle θ of the beam domain data of the measured beam, and draws a horizontal directivity diagram of the beam based on all (θ, amp).

[0019] The beneficial effects of the present invention are as follows: the device and method of the present invention can accurately measure the near-field directivity of all beams of the multi-beam side-scan sonar, reflect the track resolution capability of the multi-beam side-scan sonar in actual work, and can be used for factory inspection of the multi-beam side-scan sonar. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The beam pattern adopts far-field beamforming in all ranges;

[0021] Figure 2 It is the near-field 40m focused beam pattern;

[0022] Figure 3 is the near-field segmented focusing beam pattern;

[0023] Figure 4 It is a schematic diagram of the working mode of parallel multi-beam;

[0024] Figure 5 is a schematic diagram of a device involved in the present invention;

[0025] Figure 6 The present invention is a flow chart of the method. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The embodiments of the present invention are provided for the purpose of illustration and description, and are not intended to be exhaustive or to limit the present invention to the disclosed forms. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiments are selected and described in order to better illustrate the principles and practical applications of the present invention, and to enable those of ordinary skill in the art to understand the present invention and thereby design various embodiments with various modifications suitable for specific uses.

[0027] As shown in the figure, Figure 5 The present invention provides a device for measuring the horizontal directivity of a side-scan sonar. The device includes a display control, a first lifting mechanism and a second lifting mechanism. The first lifting mechanism includes a turntable and a side-scan sonar array. The second lifting mechanism includes a turntable and a transducer. One end of the display control is connected to the turntable of the first lifting mechanism, and the other end is connected to the transducer of the second lifting mechanism through a signal generator. A power amplifier is provided between the signal generator and the transducer. The display control controls the signal generator to generate a transmitting signal. The transmitting signal of the signal generator is given to the power amplifier. The power amplifier amplifies the received signal and gives it to the transducer and transmits an acoustic signal. The display control communicates with the dry end of the side-scan sonar. The dry end controls the transmitting signal of the receiving transducer of the side-scan sonar array under the triggering of the synchronization signal of the signal generator. The transducer and the array are located underwater, and the remaining equipment is located above water. At present, the measurement system measures far-field directivity and cannot accurately measure near-field directivity. The present invention provides a device and method for measuring the horizontal directivity of a side-scan sonar, which can accurately measure the directivity of the side-scan sonar in the near field.

[0028] The resolution of the side-scan sonar track direction depends on the horizontal beam width of the array, and the horizontal beam width depends on the aperture length and operating frequency wavelength of the array. The beam width calculation formula of the linear array is shown below.

[0029]

[0030] Where L is the length of the linear array, and λ is the wavelength of the working center frequency. Therefore, in order to obtain sufficient resolution in the track direction, a sufficiently large array length is required. An increase in the array length will result in the side scan sonar working range not fully meeting the far field conditions. The far field discrimination conditions of the array also depend on the array aperture length and the working frequency wavelength. The calculation formula for the far field conditions is as follows.

[0031]

[0032] Taking the side scan sonar with a center frequency of 450kHz as an example, assuming that the sound speed c = 1500m / s, the horizontal beam angle must not be greater than 0.2°, the array length must not be less than 0.844m, and the far field condition is 59m. In order to make the side scan sonar suitable for higher speeds, a parallel multi-beam working mode is usually adopted, such as Figure 4 As shown, the array is further increased. For example, if the array length is increased to 1.3m, the far-field condition is 127m, and the far-field condition is not fully met within the working range. In order to ensure that the resolution of the side-scan sonar in the near-field track direction does not decrease, the sound beam is focused in the near field, that is, by phase-controlled delay of different channel signals, the signals are weakened and enhanced at different positions in space, so that a focused sound beam in the shape of an hourglass can be formed. Figure 1 Far-field beamforming is used for all distances, Figure 2 This is the near-field 40m focusing result. Figure 3The existing side-scan sonar horizontal directivity measurement is to combine all channels of the array together for direct measurement, which is equivalent to far-field beamforming and cannot reflect the real directivity of the side-scan sonar in the near field.

[0033] In order to reflect the real directivity of the side-scan sonar in the near field, the control method of the side-scan sonar near-field directivity measurement device of the present invention is as follows:

[0034] Step 1: Connect the side scan sonar to be tested to the measuring device and adjust the power amplifier to ensure sufficient signal-to-noise ratio for reception;

[0035] Press the side scan sonar to be tested and the measuring device Figure 5 The transducer is an omnidirectional transducer, the side scan sonar array is perpendicular to the water surface, the transducer and the side scan sonar array are immersed in the water at the same depth, and the power amplifier is adjusted to a suitable amplification factor so that the side scan sonar receiving signal has a high signal-to-noise ratio and is not saturated. The side scan sonar only receives but does not transmit;

[0036] Step 2: Automatically align the array center and the transmitting transducer;

[0037] A rectangular coordinate system is established along the length, width and height of the anechoic pool, such as Figure 5 As shown, the display and control controls the first lifting mechanism to move along the x-axis, and each time it steps dx, after it moves into position, the display and control controls the signal generator to emit a pulse signal of the working center frequency of the side-scan sonar and simultaneously sends working parameters to the side-scan sonar, so that the side-scan sonar only receives but does not transmit and is in an external synchronization working mode, that is, the side-scan sonar receives an external trigger signal from the signal generator once to start signal acquisition; the transmitting signal generated by the signal generator is amplified by the power amplifier to stimulate the transducer to emit an acoustic signal, and at the same time, the signal generator generates a synchronous signal of the transmitting signal to trigger the side-scan sonar to start acquisition, and the side-scan sonar converts the array element domain data s array Upload, calculate and record the distance r from the transducer to the wet end of the side scan sonar based on the array element domain data of the array element at the geometric center of the array. If the number of array elements M is an odd number, the array element domain s of the center array element centre for:

[0038]

[0039] If the number of array elements is even, the average value of the array domain data of the two middle array elements is used instead, that is:

[0040]

[0041] After completing all distance steps, the display control controls the first lifting mechanism to move to the position with the smallest r value according to the recorded data, sets the position x to 0, and then controls the first lifting mechanism to move along the y-axis direction until the distance r is equal to the distance F to be measured.

[0042] Step 3: Automatically adjust the array orientation to align the array center beam with the transducer;

[0043] The display and control controls the first lifting and rotation, each step dθ, after the rotation is in place, the display and control controls the signal generator to transmit a pulse signal of the center frequency of the side scan sonar and simultaneously sends the working parameters to the side scan sonar, so that the side scan sonar only receives but does not transmit and is in an external synchronization working mode. The transmission signal generated by the signal generator is amplified by the power amplifier to stimulate the transducer to emit an acoustic signal. At the same time, the signal generator generates a synchronization signal of the transmission signal to trigger the side scan sonar to start collecting. The side scan sonar uploads the array element domain data. The display and control software selects a subarray with a certain number of array elements and located at the geometric center of the side scan sonar array according to the distance F to be measured. The subarray should be in the far field at the distance F. The display and control adds the array element domain data of the selected subarray to obtain the central beam domain data and calculates its signal strength amp. After completing all angle measurements, the display and control controls the first lifting mechanism to rotate to the angle with the maximum signal strength according to the recorded data, and sets the angle to 0°.

[0044] Step 4: Adjust the array position so that the center of the beam to be measured is aligned with the transducer, and automatically measure the horizontal directivity of the first beam;

[0045] The display control controls the first lifting mechanism to move to a certain distance along the X-axis so that the center position of the first parallel beam is aligned with the transducer. Figure 4 The distance is -(M-1)*d / 2, where M is the number of side-scan sonar array elements and d is the element spacing. Then the first lifting mechanism is controlled to rotate from -10° to 10°, with each step being dθ. After the rotation is in place, the display control signal generator transmits a pulse signal of the center frequency of the side-scan sonar and simultaneously sends working parameters to the side-scan sonar, so that the side-scan sonar only receives but does not transmit and is in an external synchronous working mode. The transmitting signal generated by the signal generator is amplified by the power amplifier to stimulate the transducer to emit an acoustic signal. At the same time, the signal generator generates a synchronization signal of the transmitting signal to trigger the side-scan sonar to start collecting. The side-scan sonar uploads the beam domain data, which is formed by the near-field focusing algorithm of the actual application state of the side-scan sonar. The display control calculates the signal strength amp and angle θ of the beam domain data of the measured beam, and draws the horizontal directivity diagram of the beam based on all (θ, amp);

[0046] Step 5: Adjust the array position and repeat step 4 to complete the horizontal directivity measurement of all beams;

[0047] The display and control controls the first lifting mechanism to move d along the x-axis. After it is in place, repeat step 4 until the horizontal directivity measurement of all parallel beams is completed. If the side scan sonar is in a multi-frequency working mode, repeat steps 4 and 5 to complete the measurement of all frequencies. If the directivity of multiple distances needs to be measured, change F and repeat steps 4 and 5.

[0048] In summary, the device and method of the present invention can accurately measure the near-field directivity of all beams of the multi-beam side-scan sonar, reflect the track resolution capability of the multi-beam side-scan sonar in actual work, and can be used for factory inspection of the multi-beam side-scan sonar.

Claims

1. A horizontal directivity measurement device for a multi-beam side-scan sonar, characterized in that: The device includes a display and control, a first lifting mechanism and a second lifting mechanism. The first lifting mechanism includes a turntable and a side-scan sonar array, and the second lifting mechanism includes a turntable and a transducer. One end of the display and control is connected to the turntable of the first lifting mechanism, and the other end is connected to the transducer of the second lifting mechanism through a signal generator. A power amplifier is arranged between the signal generator and the transducer. The display and control controls the signal generator to generate a transmitting signal, and the transmitting signal of the signal generator is given to the power amplifier. The power amplifier amplifies the received signal and gives it to the transducer to emit an acoustic signal. The display and control communicate with the dry end of the side-scan sonar. The dry end controls the transmitting signal of the receiving transducer of the side-scan sonar array under the triggering of the synchronization signal of the signal generator. The transducer and the array are located underwater, and the remaining equipment is located above water.

2. A method for measuring the horizontal directivity of a multi-beam side-scan sonar, characterized in that: The following steps are included: Step 1: Connect the side scan sonar to be tested to the measuring device and adjust the power amplifier to ensure sufficient signal-to-noise ratio for reception; Step 2: Automatically align the array center and the transmitting transducer; Step 3: Automatically adjust the array orientation to align the array center beam with the transducer; Step 4: Adjust the array position so that the center of the beam to be measured is aligned with the transducer, and automatically measure the horizontal directivity of the first beam; Step 5: Adjust the array position and repeat step 4 to complete the horizontal directivity measurement of all beams.

3. The method for measuring the horizontal directivity of a multi-beam side-scan sonar according to claim 2, characterized in that: In step one, the side scan sonar array is perpendicular to the water surface, the transducer and the side scan sonar array are immersed in the water at the same depth, and the power amplifier is adjusted to a suitable amplification factor so that the side scan sonar receiving signal has a high signal-to-noise ratio and is saturated. The side scan sonar only receives but does not transmit.

4. The method for measuring the horizontal directivity of a multi-beam side-scan sonar according to claim 3, characterized in that: In step 2, the transmitting signal generated by the signal generator is amplified by the power amplifier to stimulate the transducer to emit an acoustic signal. At the same time, the signal generator generates a synchronous signal of the transmitting signal to trigger the side-scan sonar to start collecting. The side-scan sonar converts the array element domain data s array Upload, calculate and record the distance r from the transducer to the wet end of the side scan sonar based on the array element domain data of the array element at the geometric center of the array. If the number of array elements M is an odd number, the array element domain s of the center array element centre for: If the number of array elements M is an even number, the average value of the array domain data of the two middle array elements is used instead, that is:

5. The method for measuring the horizontal directivity of a multi-beam side-scan sonar according to claim 4, characterized in that: In step three, the display and control controls the first lifting mechanism to move along the X-axis to -(M-1)*d / 2, where M is the number of side-scan sonar array elements and d is the array element spacing; then the first lifting mechanism is controlled to rotate from -10° to 10°, with each step being dθ. After the rotation is in place, the display and control controls the signal generator to emit a pulse signal of the center frequency of the side-scan sonar and simultaneously sends working parameters to the side-scan sonar. The display and control calculates the signal strength amp and angle θ of the beam domain data of the measured beam, and draws the horizontal directivity diagram of the beam based on all (θ, amp).

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