Single-beam sounding system with self-calibration function

Abstract

The invention provides a single-beam sounding system with a self-calibration function. The system comprises at least two single-beam depth sounder, a calibration scale and a data calibration unit, the single-beam depth sounder used for sound velocity calibration is installed on the calibration scale, and the single-beam depth sounder used for sound velocity calibration and other single-beam depth sounder used for underwater distance measurement are connected to the data calibration unit together. The calibration scale and the single-beam depth sounder are placed in the same water body to be measured, and the single-beam depth sounder used for sound velocity calibration returns a known and constant underwater distance measurement value on the calibration scale to the data calibration unit. The single-beam depth sounder used for underwater distance measurement returns a measured value of an unknown underwater distance to the data calibration unit, and the data calibration unit calibrates the measured values returned by all the single-beam depth sounder. The single-beam sounding system with the self-calibration function provided by the invention has the characteristics of no drifting of a measurement result, high precision, no need of integrating additional temperature and turbidity sensors and the like, and the like.

Description

Technical Field

[0001] This invention relates to the field of underwater ultrasonic ranging technology, and in particular to a single-beam depth sounding system with self-calibration function. Background Technology

[0002] Underwater ranging is the primary method for achieving three-dimensional topographic surveying of underwater riverbeds or seabeds, and single-beam echo sounders are currently the most commonly used underwater three-dimensional topographic surveying instruments. The working principle of a single-beam echo sounder is as follows: an ultrasonic transducer emits several pulsed sound waves vertically downwards. The sound waves propagate in a straight line in the water at the speed of sound C, and upon encountering the riverbed or seabed surface, they are reflected to form an echo. The echo propagates in the opposite direction along the original path and is captured by the ultrasonic transducer. Let the time interval from the emission of the pulsed sound wave to the arrival of the echo at the ultrasonic transducer be ΔT, then the distance between the ultrasonic transducer and the riverbed or seabed surface is d = 0.5CΔT.

[0003] According to the measurement principle, the error in underwater ultrasonic ranging mainly comes from the speed of sound (C) and the sound wave propagation time (ΔT). Currently, the timing circuit of ordinary single-beam echo sounders can achieve an accuracy of 10 ns, and the measurement error caused by timing error is only about 0.015 mm, which can be ignored. The speed of sound in water is about 1500 m / s under normal temperature conditions, but it changes with environmental factors such as water temperature and turbidity. Taking seawater as an example, the speed of sound can change by 4 m / s for every 1°C increase or decrease in temperature, resulting in a relative measurement error of about 0.27%, which becomes the main source of error in ultrasonic ranging. To reduce the impact of sound speed error on measurement accuracy, the current common practice is to integrate a temperature sensor into the ultrasonic transducer and correct the sound speed by measuring the actual temperature. However, adding a temperature sensor increases the size of the ultrasonic transducer, affecting its performance; at the same time, the commonly used formulas for calculating the speed of sound are mostly empirical formulas, which are only applicable to specific conditions such as clear water. In addition, regarding the impact of water turbidity on the speed of sound, there is currently neither a reliable calculation formula nor a high-precision turbidity measurement sensor.

[0004] Therefore, current single-beam echo sounders cannot overcome measurement errors caused by changes in temperature and water turbidity. When used for long-term underwater distance measurement, systematic deviations will exist in the measurement results, and these errors will change (drift) over time and are difficult to eliminate. Summary of the Invention

[0005] This invention provides a single-beam echo sounder system with self-calibration function, which effectively eliminates systematic underwater distance measurement errors caused by dynamic changes such as temperature and turbidity.

[0006] To achieve the above objectives, the present invention adopts the following technical solution.

[0007] A single-beam echo sounding system with self-calibration function comprises: at least two single-beam echo sounders, a calibration scale and a data calibration unit, wherein one single-beam echo sounder is used for sound velocity calibration and the other single-beam echo sounders are used for underwater distance measurement.

[0008] A single-beam echo sounder for sound velocity calibration is mounted on the calibration scale and connected to the data calibration unit along with other single-beam echo sounders for underwater distance measurement. The calibration scale for sound velocity calibration and the single-beam echo sounders for underwater distance measurement are placed in the same body of water to be measured, and underwater distances are measured synchronously. The single-beam echo sounder for sound velocity calibration returns the measured value of the known and fixed underwater distance on the calibration scale to the data calibration unit, while the single-beam echo sounder for underwater distance measurement returns the measured value of the unknown underwater distance to the data calibration unit. The data calibration unit calibrates the measured values ​​returned by all single-beam echo sounders.

[0009] Preferably, the calibration scale includes an ultrasonic transducer mounting bracket, an acoustic reflector, and a connecting component. The ultrasonic transducer mounting bracket fixes the ultrasonic transducer in the single-beam depth sounder used for sound velocity calibration. The area of ​​the acoustic reflector is larger than the diameter of the acoustic beam emitted by the single-beam depth sounder used for sound velocity calibration. The distance between the acoustic reflector and the ultrasonic transducer mounting bracket is larger than the blind zone of the single-beam depth sounder. The acoustic reflector is perpendicular to the axis of the fixed ultrasonic transducer. The connecting component is used to connect the ultrasonic transducer mounting bracket and the acoustic reflector.

[0010] Preferably, the single-beam depth sounder is any depth sounder based on an ultrasonic transducer.

[0011] Preferably, the data calibration unit simultaneously receives readings from all single-beam echo sounders, obtains the underwater sound velocity based on the measurement value returned by the single-beam echo sounder used for sound velocity calibration, and then calibrates the measurement value returned by the single-beam echo sounder used for underwater distance measurement.

[0012] Preferably, the step of the data calibration unit calibrating the measurement values ​​returned by the single-beam echo sounder used for underwater distance measurement includes:

[0013] (1) The single-beam depth sounder used for underwater distance measurement and the single-beam depth sounder used for sound velocity calibration perform a data measurement under the control of the data calibration unit;

[0014] (2) Let the underwater sound velocity built into the single-beam echo sounder used for sound velocity calibration be C1. This single-beam echo sounder is used to measure a known and fixed underwater distance L. j If at a certain time t the single-beam echo sounder returns a measurement value of L1, then the calibrated underwater sound velocity C at this time is:

[0015]

[0016] (3) The calibrated underwater sound velocity correction value C t The underwater sound velocity correction values ​​C are stored in a data list arranged chronologically. The data list is then used to retrieve the underwater sound velocity correction values ​​C from the data list, which are the most recent values ​​from the current time. t A data sequence is formed, outliers in the data sequence are removed, and the underwater sound speed calibration value C at the current moment is calculated based on the data sequence.

[0017] (4) Suppose that the underwater sound velocity built into a single-beam echo sounder used for underwater distance measurement is C2, and the measurement value returned by the single-beam echo sounder at the same time t is L2, then the underwater distance L returned by the corrected single-beam echo sounder is:

[0018]

[0019] (5) All measurements of the single-beam echo sounder used for underwater distance measurement are corrected according to the method described in step (4), and the corrected values ​​are used as the final measurements.

[0020] (6) Repeat steps (1) to (5) until the underwater distance measurement task is completed.

[0021] Preferably, the data calibration unit calculates the underwater sound speed calibration value C at the current moment based on the data sequence, including:

[0022] The data calibration unit extracts the underwater sound velocity correction values ​​of the nearest set number of times from the data list to form a data sequence. It then uses the normalized median method to remove outliers from the data sequence and obtains the underwater sound velocity calibration value C for the current time through algebraic averaging.

[0023] As can be seen from the technical solution provided by the present invention, the single-beam depth sounding system with self-calibration function proposed by the present invention has the characteristics of no drift in measurement results, high accuracy, and no need to integrate additional sensors such as temperature and turbidity sensors.

[0024] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and will become apparent from the description or may be learned by practice of the invention. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a structural diagram of a single-beam depth sounding system with self-calibration function provided in an embodiment of the present invention;

[0027] Figure 2 This is a structural diagram of a calibration scale provided in an embodiment of the present invention. Detailed Implementation

[0028] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0029] Those skilled in the art will understand that, unless specifically stated otherwise, the singular forms “a,” “an,” “the,” and “the” used herein may also include the plural forms. It should be further understood that the term “comprising” as used in this specification means the presence of the stated features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. It should be understood that when we say an element is “connected” or “coupled” to another element, it can be directly connected or coupled to the other element, or there may be intermediate elements. Furthermore, “connected” or “coupled” as used herein can include wireless connections or couplings. The term “and / or” as used herein includes any and all combinations of one or more of the associated listed items.

[0030] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.

[0031] To facilitate understanding of the embodiments of the present invention, the following will provide further explanation and description with reference to the accompanying drawings and several specific embodiments. These embodiments do not constitute a limitation on the embodiments of the present invention.

[0032] This invention addresses the challenge of existing single-beam echo sounders failing to eliminate measurement errors caused by factors such as water temperature and turbidity. It proposes a single-beam echo sounder system with self-calibration capabilities, characterized by drift-free measurement results, high accuracy, and the elimination of the need for additional sensors such as temperature and turbidity sensors.

[0033] This invention provides a self-calibrating single-beam echo sounder system comprising at least two single-beam echo sounders, a calibration scale, and a data calibration unit. One single-beam echo sounder is used for sound velocity calibration, while the others are used for underwater distance measurement. The aforementioned single-beam echo sounders can be any general-purpose echo sounder based on an ultrasonic transducer.

[0034] The calibration scale consists of an ultrasonic transducer mounting bracket, an acoustic reflector, and connecting components. The ultrasonic transducer mounting bracket secures the ultrasonic transducer in the single-beam echo sounder used for sound velocity calibration. The area of ​​the acoustic reflector is larger than the diameter of the acoustic beam emitted by the single-beam echo sounder used for sound velocity calibration. The distance between the acoustic reflector and the ultrasonic transducer mounting bracket is larger than the blind zone of the single-beam echo sounder, and the acoustic reflector is perpendicular to the axis of the fixed ultrasonic transducer. The connecting components connect the ultrasonic transducer mounting bracket and the acoustic reflector, ensuring that their relative positions remain unchanged.

[0035] The single-beam echo sounder used for sound velocity calibration is mounted on the calibration scale and connected to the data calibration unit along with other single-beam echo sounders used for underwater distance measurement.

[0036] The calibration scale of the ultrasonic transducer in the single-beam echo sounder used for sound velocity calibration and the ultrasonic transducer in the single-beam echo sounder used for underwater distance measurement are placed in the same body of water to be measured, and the underwater distance is measured synchronously. The single-beam echo sounder used for sound velocity calibration returns the known and fixed underwater distance measurement value on the calibration scale to the data calibration unit, while the single-beam echo sounder used for underwater distance measurement returns the measurement value of the unknown underwater distance to the data calibration unit.

[0037] The data calibration unit simultaneously receives readings from all single-beam echo sounders. Based on the measurement values ​​returned by the single-beam echo sounder used for sound velocity calibration, it obtains the accurate underwater sound velocity. Then, it calibrates the measurement values ​​returned by the single-beam echo sounder used for underwater distance measurement to eliminate measurement errors caused by temperature, turbidity, etc.

[0038] In this embodiment, the steps for the data calibration unit to complete the calibration of the underwater distance measurement results are as follows:

[0039] (1) The single-beam echo sounder used for underwater distance measurement and the single-beam echo sounder used for sound velocity calibration perform a data measurement under the control of the data calibration unit. The data calibration unit sends a data acquisition command to the single-beam echo sounder at a fixed frequency. After receiving the data acquisition command, the single-beam echo sounder completes an underwater distance measurement and sends the measurement results and the currently preset underwater sound velocity and other data to the data calibration unit.

[0040] (2) Let the underwater sound velocity built into the single-beam echo sounder used for sound velocity calibration be C1. At a certain time t, the measurement value returned by the single-beam echo sounder is L1. Then the calibrated underwater sound velocity C at this time is:

[0041]

[0042] (3) The calibrated underwater sound velocity correction value C t The data is stored in a chronologically ordered list for preprocessing. To eliminate the influence of random errors on the underwater sound velocity correction values, the underwater sound velocity correction values ​​C from the most recent time are retrieved from the data list. t This forms a data sequence. Outliers in the data sequence are then removed, and the underwater sound velocity calibration value C for the current moment is calculated based on the data sequence. In this implementation, the underwater sound velocity calibration values ​​for the nine moments closest to the current moment are retrieved from the data list. The normalized median method is used to remove outliers from the data sequence, and then an algebraic average is used to obtain the underwater sound velocity calibration value for the current moment.

[0043] (4) Suppose that the underwater sound velocity built into a single-beam echo sounder used for underwater distance measurement is C2, and the measurement value returned by the single-beam echo sounder at the same time t is L2, then the corrected underwater distance L is:

[0044]

[0045] (5) All measurements of the single-beam echo sounder used for underwater distance measurement are corrected according to the method described in step (4), and the corrected values ​​are used as the final measurements.

[0046] (6) Repeat steps (1) to (5) until the underwater distance measurement task is completed.

[0047] A structural diagram of a single-beam depth sounding system with self-calibration function provided in this embodiment of the invention is shown below. Figure 1 As shown, the structural diagram of the calibration scale is as follows: Figure 2 As shown. Figure 1As shown, the single-beam echo sounder system with self-calibration function provided in this embodiment of the invention consists of two single-beam echo sounders (1a, 1b, 2a, 2b), calibration scales (3a, 3b, 3c), and a data calibration unit 4. The single-beam echo sounders can be any general-purpose echo sounder based on an ultrasonic transducer. In this embodiment, the single-beam echo sounder for underwater distance measurement consists of ultrasonic transducer 1a and a main unit 1b, and the single-beam echo sounder for sound velocity calibration consists of ultrasonic transducer 2a and a main unit 2b. In a preferred embodiment, the single-beam echo sounders are all of the same model and specifications, with an ultrasonic transducer outer diameter of 14mm and a sound wave frequency of 2MHz. The main unit controls the transmission of sound wave pulses and the processing of echo signals, and performs underwater distance measurement based on the sound wave propagation time and a preset sound velocity, outputting the measured values ​​as digital or analog signals.

[0048] A structural diagram of a calibration scale provided in this embodiment of the invention is shown below. Figure 2 As shown, the calibration scale consists of an ultrasonic transducer mounting bracket 3a, a connecting component 3b, and an acoustic wave reflector 3c. The ultrasonic transducer mounting bracket 3a is a rectangular stainless steel plate, 5cm long, 2cm wide, and 1cm thick. A through hole 3d is pre-drilled on the plate for mounting the ultrasonic transducer. The inner diameter of the hole is slightly larger than the outer diameter of the ultrasonic transducer 2a in the single-beam echo sounder used for sound velocity calibration. The axis of the hole is perpendicular to the plate surface. The acoustic wave reflector 3c serves to provide a stable reflecting surface with a known distance for the sound waves emitted by the ultrasonic transducer. In this embodiment, a thin stainless steel plate, 2mm thick, is used as the acoustic wave reflector 3c. The plate surface is flat, and its area is larger than the diameter of the sound wave beam emitted by the single-beam echo sounder used for sound velocity calibration, measuring 5cm × 5cm. The connecting component 3b consists of two stainless steel strips, each 20cm long and with a cross-sectional dimension of 1cm × 1cm. It is used to connect and fix the ultrasonic transducer mounting bracket 3a and the acoustic wave reflector plate 3c, ensuring that the axis of the ultrasonic transducer mounting through hole 3d on the mounting bracket is perpendicular to the acoustic wave reflector plate 3c, and the extended line of the axis intersects the acoustic wave reflector plate 3c at the middle position of the plate.

[0049] In this embodiment, the ultrasonic transducer 2a in the single-beam depth sounder used for sound velocity calibration is installed in the through hole 3d on the ultrasonic transducer mounting support 3a of the calibration scale. The sound wave emission direction of the ultrasonic transducer is perpendicular to the sound wave reflector 3c. The distance between the front end of the ultrasonic transducer 2a and the sound wave reflector 3c is greater than the measurement blind zone of the depth sounder.

[0050] When measuring underwater distance, ultrasonic transducers 1a and 2a from both the single-beam echo sounder used for sound velocity calibration and the single-beam echo sounder used for underwater distance measurement are simultaneously placed in the water body 5 to be measured. The measurement returned by the single-beam echo sounder used for sound velocity calibration is the known distance L between the front end of its ultrasonic transducer 2a and the sound wave reflector 3c. jThe measured value L2 is the measurement value returned by the single-beam echo sounder used for underwater distance measurement, which is the measured value L1 of the unknown underwater distance L that needs to be measured.

[0051] In this embodiment, the data calibration unit 4 controls all depth sounders to continuously acquire data at a specified frequency, and receives the measurement values ​​returned by all single-beam depth sounders after each acquisition step, including the measured underwater distance and preset sound velocity. The data calibration unit 4 first performs preset sound velocity calibration based on the measurement value L2 returned by the single-beam depth sounder used for sound velocity calibration, and then calibrates the measurement value L1 returned by the single-beam depth sounder used for underwater distance measurement based on the calibrated sound velocity C, obtaining the underwater distance measurement result L, which is unaffected by temperature and turbidity. In this embodiment, the data calibration unit 4 is host computer software installed on a computer, which simultaneously receives real-time readings from the single-beam depth sounders via the computer's serial port.

[0052] In summary, when the single-beam echo sounder with self-calibration function proposed in this embodiment of the invention conducts underwater distance measurements, although the temperature and turbidity of the measured water may change continuously over time, the system performs sound velocity calibration at each acquisition step, thereby eliminating systematic measurement errors caused by dynamic changes in temperature and turbidity, making the measurement results of the underwater topographic erosion and deposition process stable and reliable.

[0053] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of one embodiment, and the modules or processes shown in the drawings are not necessarily essential for implementing the present invention.

[0054] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for apparatus or system embodiments, since they are basically similar to method embodiments, the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments. The apparatus and system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0055] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A single-beam bathymetric system with self-calibration function, characterized in that, The application relates to a single-beam depth sounder calibration system, which comprises at least two single-beam depth sounders, a calibration ruler and a data calibration unit. The single-beam depth sounder for sound velocity calibration is installed on the calibration ruler and connected to the data calibration unit together with the single-beam depth sounders for underwater distance measurement; the calibration ruler on which the single-beam depth sounder for sound velocity calibration is installed and the single-beam depth sounders for underwater distance measurement are placed in the same water body to be measured, and underwater distances are synchronously measured; the single-beam depth sounder for sound velocity calibration returns the measurement value of the underwater distance on the calibration ruler which is known and unchangeable to the data calibration unit; the single-beam depth sounders for underwater distance measurement return the measurement value of the unknown underwater distance to the data calibration unit; and the data calibration unit calibrates the measurement values returned by all the single-beam depth sounders. The calibration ruler comprises an ultrasonic transducer mounting support, an acoustic wave reflection plate and a connecting component; the ultrasonic transducer mounting support fixes the ultrasonic transducer in the single-beam depth sounder for sound velocity calibration; the area of the acoustic wave reflection plate is larger than the diameter of the acoustic wave beam emitted by the single-beam depth sounder for sound velocity calibration; the distance between the acoustic wave reflection plate and the ultrasonic transducer mounting support is larger than the blind area of the single-beam depth sounder; the acoustic wave reflection plate is perpendicular to the axis of the fixed ultrasonic transducer; and the connecting component is used for connecting the ultrasonic transducer mounting support and the acoustic wave reflection plate.

2. The system of claim 1, wherein, The single-beam depth sounder is any ultrasonic transducer-based depth sounder.

3. The system of claim 1, wherein, The data calibration unit receives the readings of all the single-beam depth sounders at the same time, obtains the underwater sound velocity according to the measurement value returned by the single-beam depth sounder for sound velocity calibration, and then calibrates the measurement value returned by the single-beam depth sounder for underwater distance measurement.

4. The system according to claim 1 or 2 or 3, characterized in that, The calibration of the measurement value returned by the single-beam depth sounder for underwater distance measurement by the data calibration unit comprises the following steps:

5. The system of claim 4, wherein, (1) the single-beam depth sounders for underwater distance measurement and the single-beam depth sounder for sound velocity calibration perform data measurement under the control of the data calibration unit; (4) assuming that the underwater sound velocity of a single-beam depth sounder for underwater distance measurement is C2, and the measurement value returned by the single-beam depth sounder at the same time t is L2, then the underwater distance L returned by the single-beam depth sounder after correction is: (2) The underwater sound velocity built-in in the single-beam sounder for sound velocity calibration is C1, and the single-beam sounder is used to measure a known and fixed underwater distance L j The measurement value returned by the single-beam sounder at a certain time t is L1, and the calibrated underwater sound velocity C at this time is: (3) the calibrated underwater sound speed correction value C t The underwater sound speed correction values C stored in the data list in chronological order are taken out from the data list, and the underwater sound speed correction values C at several time points closest to the current time are taken out from the data list t , a data sequence is formed, outliers in the data sequence are eliminated, and the underwater sound speed correction value C at the current time is calculated according to the data sequence; (5) the measurement values of all the single-beam depth sounders for underwater distance measurement are corrected according to the method described in step (4), and the corrected values are taken as the final measurement values; (6) steps (1) to (5) are repeated until the underwater distance measurement task is completed. The data calibration unit calculates the underwater sound velocity calibration value C at the current time according to the data sequence, which comprises the following steps:

6. The system of claim 5, wherein, The data calibration unit takes the underwater sound velocity correction values of a set number of time points closest to the current time from the data list to form a data sequence, removes the abnormal values in the data sequence by using the normalized median method, and then obtains the underwater sound velocity calibration value C at the current time through algebraic average operation. ​

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