Swimming speed measuring device and swimming speed measuring method

Abstract

A swimming speed measurement apparatus (1) is disclosed, comprising a transducer (2), a radial velocity calculation module (13), a distance derivative calculation module (14), and a swimming speed calculation module (15). The transducer (2) is configured to generate echo signals based on ultrasound pulses, which are periodically emitted into water and reflected by a swimming object moving in the water. The radial velocity calculation module (13) is configured to calculate a radial velocity of the swimming object based on a phase difference between two echo signals. The distance derivative calculation module (14) is configured to calculate a first derivative of a distance between the swimming object and the transducer with respect to time based on two echo signals. The swimming speed calculation module (15) is configured to calculate a swimming speed of the swimming object based on the radial velocity and the first derivative of the distance.

Description

Technical Field

[0001] This disclosure relates to a swimming speed measuring device, swimming speed measuring method and procedure. Background Technology

[0002] Patent document 1 discloses a technique for calculating the swimming speed of a fish using a single-beam transducer and utilizing the distance between the transducer and the fish based on the fact that the distance changes hyperbolically over time (see paragraphs 0085-0094).

[0003] Existing technical documents Patent documents Patent Document 1: JP2022-158950 However, the accuracy of measuring swimming speed using the technology disclosed in Patent Document 1 is insufficient.

[0004] This disclosure is made in view of the above-mentioned problems, and its main purpose is to provide a swimming speed measuring device, swimming speed measuring method and program that can improve the measurement accuracy of swimming speed. Summary of the Invention

[0005] To address the aforementioned problems, a swimming speed measuring device according to a first aspect of this disclosure includes a transducer, a radial velocity calculation module, a distance derivative calculation module, and a swimming speed calculation module. The transducer is configured to generate echo signals based on ultrasonic pulses, which are periodically emitted into the water and reflected by a swimming object. The radial velocity calculation module is configured to calculate the radial velocity of the swimming object based on the phase difference between two of the echo signals. The distance derivative calculation module is configured to calculate the first derivative of the distance between the swimming object and the transducer with respect to time based on the two echo signals. The swimming speed calculation module is configured to calculate the swimming speed of the swimming object based on the radial velocity and the first derivative of the distance. Therefore, the measurement accuracy of swimming speed can be improved.

[0006] In the above implementation scheme, the swimming speed calculation module can also be configured to adjust the radial speed based on a comparison of the first derivative of the radial speed and the distance. Therefore, the measurement accuracy of the swimming speed can be improved.

[0007] In the above implementation scheme, the swimming speed calculation module can also be configured to calculate the swimming speed based on the product of the adjusted radial velocity and the distance. Therefore, the measurement accuracy of the swimming speed can be improved.

[0008] In the above implementation scheme, the swimming speed calculation module can also be configured to calculate the swimming speed based on the product of a linear function of time. Therefore, the measurement accuracy of the swimming speed can be improved.

[0009] In the above implementation scheme, the swimming speed calculation module can also be configured to calculate the swimming speed based on the slope of a linear function corresponding to the square of the swimming speed. Therefore, the measurement accuracy of the swimming speed can be improved.

[0010] In the above implementation, a tracking module may also be provided. The tracking module can be configured to track the echo of the same swimmer from the echo signal. In this way, the swimming speed of the same swimmer tracked among multiple swimmers can be measured.

[0011] In the above embodiment, the transducer can be a single-beam transducer. Therefore, even when using a single-beam transducer, the measurement accuracy of the swimming velocity can be improved.

[0012] In the above embodiment, the transducer can generate the echo signal by forming one or more receiving beams, and can use one of the one or more receiving beams to generate the two echo signals. Therefore, the measurement accuracy of swimming speed can be improved by using a single receiving beam.

[0013] The swimming speed measurement method according to a second aspect of this disclosure includes: generating echo signals based on ultrasonic pulses using a transducer, the ultrasonic pulses being periodically emitted into the water and reflected by a swimming body in the water; calculating the radial velocity of the swimming body based on the phase difference between two said echo signals; calculating the first derivative of the distance between the swimming body and the transducer with respect to time based on the two echo signals; and calculating the swimming speed of the swimming body based on the first derivative of the radial velocity and the distance. Therefore, the accuracy of swimming speed measurement can be improved.

[0014] A third aspect of this disclosure relates to a program including instructions that, when executed by a computer, cause the computer to perform the method of the second aspect. Specifically, the program according to the third aspect causes the computer to perform the following operations: obtain echo signals generated by a transducer based on ultrasonic pulses, which are periodically emitted into water and reflected by a swimming body in the water; calculate the radial velocity of the swimming body based on the phase difference between two said echo signals; calculate the first derivative of the distance between the swimming body and the transducer with respect to time based on the two echo signals; and calculate the swimming speed of the swimming body based on the radial velocity and the first derivative of the distance. Therefore, the accuracy of swimming speed measurement can be improved.

[0015] According to this disclosure, the accuracy of swimming speed measurement can be improved. Attached Figure Description

[0016] Figure 1 An example of a swimming speed measuring device is shown.

[0017] Figure 2 An example of a processing module is shown.

[0018] Figure 3 An example of a method for measuring swimming speed is shown.

[0019] Figure 4 It is a diagram illustrating the measurement of swimming speed.

[0020] Figure 5 It is a diagram illustrating the measurement of swimming speed.

[0021] Figure 6 This is a graph showing the measurement results of a reference example.

[0022] Figure 7 This is a graph showing the measurement results of the implementation scheme. Detailed Implementation

[0023] The functionality of the elements disclosed herein can be implemented using circuitry or processing circuitry, including general-purpose processors, special-purpose processors, integrated circuits, ASICs (“Application-Specific Integrated Circuits”), conventional circuitry, and / or combinations thereof configured or programmed to perform the disclosed functions. Processors are considered processing circuitry or circuit systems because they include transistors and other circuitry.

[0024] In this disclosure, a circuit, unit, or device is hardware that performs or is programmed to perform the functions described herein. The hardware can be any hardware disclosed herein or otherwise known that is programmed or configured to perform the functions described herein.

[0025] When hardware is a processor that can be considered a type of circuit, the circuit, device, or unit is a combination of hardware and software, with the software used to configure the hardware and / or processor.

[0026] Embodiments of the present disclosure will now be described with reference to the accompanying drawings. In this specification and drawings, elements similar to those previously described with respect to the previous drawings may be denoted by the same reference numerals, and detailed descriptions may be omitted accordingly.

[0027] Figure 1 This diagram illustrates a configuration example and application example of the swimming speed measuring device 1. The swimming speed measuring device 1 is used to measure the swimming speed of a swimming object FS moving in water. The swimming object FS is, for example, a fish. The swimming speed measuring device 1 is installed, for example, in a fish farm, such as in a fish farming cage. The swimming object FS can be not only a living organism, but also any moving object moving in water, such as an underwater drone.

[0028] The swimming speed measuring device 1 includes a transducer 2 fixed in the water and a processing module 3 communicatively connected to the transducer 2.

[0029] Transducer 2 is a transducer that converts electrical signals into ultrasonic waves and vice versa. Transducer 2 periodically emits ultrasonic pulses (hereinafter also referred to as "pulses") into the water and receives pulses reflected by swimming objects FS to generate echo signals.

[0030] In this embodiment, transducer 2 is a single-beam transducer. A single-beam transducer is a transducer that has a single receiving channel and forms a single receiving beam.

[0031] In contrast, split-beam transducers have multiple receiving channels and form multiple receiving beams. The three-dimensional position of the swimming animal can be determined based on the phase difference between the multiple receiving channels, and the swimming speed can be accurately measured based on the change in position over time. However, split-beam transducers are more expensive than single-beam transducers.

[0032] According to the technology disclosed in Patent Document 1, a single-beam transducer can be used to measure swimming speed, but the measurement accuracy is insufficient.

[0033] In this embodiment, by using the following calculation method, the measurement accuracy of swimming velocity can be improved even when a single-beam transducer, which is cheaper than a split-beam transducer, is provided.

[0034] Note that transducer 2 can be a split-beam transducer. The calculation method of this embodiment can be applied when the split-beam transducer is used in single-beam mode, i.e., when the echo signal is generated by one of multiple receiving beams.

[0035] like Figure 1 As shown, assume that at time t, the swimming body FS moves linearly at a constant speed v at a distance r from transducer 2. At time t, the angle θ of the pulse incident on the swimming body FS has the relationship expressed by Equation 1 below.

[0036] Equation 1 t p The time when the swimming body FS, moving at a constant speed, comes closest to transducer 2. p At time t p The distance between the swimmer FS and the transducer 2 is the length of the vertical line from the transducer 2 down to the straight line corresponding to the three-dimensional trajectory of the swimmer FS.

[0037] For the swimming velocity *v* of a swimming body *FS*, the acoustically detectable velocity component is *vsinθ* along the incident angle of the pulse. Since *vsinθ* is the radial velocity *v* that contributes to the Doppler effect... dop (Doppler velocity), therefore, the calculation method of this embodiment uses this relationship to calculate the swimming velocity v.

[0038] Figure 2 This is a block diagram illustrating a configuration example of processing module 3. Processing module 3 is a computer including a CPU and performs signal processing according to a program. The program can be provided from a non-transitory storage medium or from a communication line.

[0039] Processing module 3 includes an echo signal acquisition module 11, a tracking module 12, a radial velocity calculation module 13, a distance derivative calculation module 14, and a swimming velocity calculation module 15. These functional modules are implemented by the CPU executing signal processing according to the program.

[0040] Figure 3 This is a flowchart illustrating an example of a swimming speed measurement method implemented in swimming speed measuring device 1. The processing module 3 of swimming speed measuring device 1 executes the signal processing shown in this figure according to a program. Figure 4 and 5 It is a diagram used to illustrate the measurement of swimming speed.

[0041] In step S11, processing module 3 acquires the echo signal from transducer 2 (processing by echo signal acquisition module 11). For example... Figure 4 As shown, processing module 3 acquires echo signals from multiple pulses 1 to 3. Although in Figure 4 The example shown only shows 3 pulses, but echo signals of 4 or more pulses can be acquired and used for swimming speed measurement.

[0042] In step S12, processing module 3 tracks the echo from the same swimmer FS in the echo signal (processing by tracking module 12). For example... Figure 4 As shown, processing module 3 performs tracking by extracting echoes with at least a given intensity from the echo signals of multiple pulses 1-3 and by determining the continuity of the echoes between adjacent pulses. Other methods can be used for tracking, such as using a Kalman filter.

[0043] In step S13, processing module 3 measures the distance r from transducer 2 to swimmer FS based on the echo signal. For example... Figure 4 As shown, processing module 3 calculates the distance r of each echo signal from multiple pulses 1 to 3. The distance r is calculated based on the time from when the transducer 2 emits a pulse to when the reflected pulse is detected (the round-trip time of the pulse) and the propagation speed of ultrasound in water.

[0044] In step S14, processing module 3 measures the phase difference ΔΦ of the echo signal. For example... Figure 4 As shown, processing module 3 measures the phase difference ΔΦ between adjacent pulses of the echo signals of multiple pulses 1 to 3. Specifically, processing module 3 calculates the IQ signal (in-phase / quadrature-phase signal) of each echo signal and uses complex correlation to calculate the phase difference ΔΦ between adjacent pulses.

[0045] In step S15, processing module 3 calculates the radial velocity v of the swimming body FS based on the phase difference ΔΦ. dop (Doppler velocity) (Processed by radial velocity calculation module 13). Radial velocity v dop This is expressed by Equation 2 below. λ is the wavelength of the pulse. Δt is the pulse emission period.

[0046] Equation 2 Due to aliasing (entanglement), the phase difference ΔΦ remains arbitrary and cannot be uniquely determined. This uncertainty is addressed below by using the first derivative of the distance r, -dr / dt.

[0047] In step S16, processing module 3 calculates the first derivative of distance r with respect to time t, -dr / dt, based on the echo signal (processing by distance derivative calculation module 14). For example... Figure 4 As shown, processing module 3 calculates the first derivative -dr / dt between adjacent pulses of the echo signals of multiple pulses 1 to 3.

[0048] If the radial velocity v dop Without aliasing, the first derivative -dr / dt should be equal to the radial velocity v. dop However, the first derivative -dr / dt is not accurate enough to be used independently to calculate the swimming velocity v.

[0049] In steps S17 to S20, processing module 3 is based on radial velocity v dop The swimming velocity v is calculated using the first derivative -dr / dt (processed by the swimming velocity calculation module 15). Steps S17 to S20 are described below.

[0050] In step S17, processing module 3 is based on radial velocity v dop Adjusting the radial velocity v by comparing it with the first derivative -dr / dt. dop Specifically, processing module 3 uses the following equation 3 to calculate the nearest integer n. The square brackets in the equation indicate the rounding operation to the nearest integer.

[0051] Equation 3 Then, processing module 3 uses the calculated integer n to adjust the radial velocity v using the following equation 4. dop As a result, the radial velocity v obtained by subtracting the aliasing component is obtained. dop In the following text, the left side of Equation 4 (v with the cap symbol) dop This is referred to as "adjusted radial velocity v". dop ".

[0052] Equation 4 In step S18, processing module 3 calculates the adjusted radial velocity v dop The product of the distance r. Specifically, by substituting the above Equation 1 into sinθ of Equation 2, we obtain the following Equation 5, and by multiplying both sides of Equation 5 by -r, we obtain the following Equation 6.

[0053] Equation 5 Equation 6 According to Equation 6, the adjusted radial velocity v dop The product of the distance r and the distance t is a linear function of time t. The slope of the linear function corresponds to the square of the swimming velocity v.

[0054] In step S19, processing module 3 performs linear regression based on the calculated product and time t to obtain the slope of the linear function. Furthermore, in step S20, processing module 3 calculates the swimming speed v based on the slope of the linear function.

[0055] like Figure 5 As shown in Equation 6, due to the adjusted radial velocity v dop The product of distance r and time t is a linear function of time t, and the slope of the linear function corresponds to the square of the swimming speed v. Therefore, the slope of the linear function can be obtained through linear regression to obtain the square of the swimming speed v, and the swimming speed v can be obtained by calculating the square root of the slope of the linear function.

[0056] when Figure 5 When the slope of the linear function shown in Equation 6 is negative or when the correlation is low (e.g., when the coefficient of determination is 0.8 or less), the processing module 3 may not output the swimming speed v.

[0057] The process of measuring swimming speed is completed. According to this implementation scheme, the radial velocity v can be adjusted by using the first derivative of distance r -dr / dt. dop To improve the measurement accuracy of swimming speed v.

[0058] The following describes an example and a reference example. The example is a calculation method for the above-described embodiment. The reference example is a calculation method from Patent Document 1.

[0059] In the experiment, a split-beam fish detector was used to track yellowtail fish in aquaculture cages from data recorded from echo recordings. Then, for each tracked individual, the swimming speed was calculated using the split-beam method, a swimming speed calculated based on an example, and a swimming speed calculated based on a reference example.

[0060] Figure 6 It plots curves for each individual, with the horizontal axis representing the swimming velocity calculated from the split beam and the vertical axis representing the swimming velocity calculated based on the reference example. Figure 7 It plots a curve for each individual, where the horizontal axis represents the swimming speed calculated by split beams, and the vertical axis represents the swimming speed calculated based on the example.

[0061] The diagonal line in the diagram is the line y=x, that is, the line when the two swimming speeds are the same, and the closer to the line, the higher the measurement accuracy.

[0062] Compare Figure 6 and 7 It can be seen that the measurement accuracy of swimming speed is higher in the implementation scheme than in the reference example, because the point is... Figure 6 The curve is more discrete, and the points are in Figure 7 The curves are more clustered near the diagonal line.

[0063] Although embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications are of course possible for those skilled in the art.

[0064] The above-described method for measuring swimming speed is commonly used in fish detectors, but is not limited to them, and can also be used, for example, in sonar. Even in fish detectors or sonars that form multiple receiving beams, the calculation method of this embodiment can be applied to the echo signal generated by one of the multiple receiving beams.

[0065] The determination of the integer n in step S17 can be performed on a unit of one pulse, or for each tracked individual, while adjusting v. dop Then, v can be calculated for all pulses. dop The difference between -dr / dt and the average value can be obtained.

[0066] Symbol Explanation 1. Swimming speed measuring device 2. Transducer 3 Processing Module 11 Echo signal acquisition unit 12 Tracking Module 13 Radial velocity calculation module 14 Distance derivative calculation module 15 Swimming speed calculation unit FS swimmers

Claims

1. A swimming speed measuring device (1), comprising: The transducer (2) is configured to generate an echo signal based on an ultrasonic pulse, which is periodically emitted into the water and reflected by a swimming body in the water. The radial velocity calculation module (13) is configured to calculate the radial velocity of the swimming body based on the phase difference between the two echo signals; The distance derivative calculation module (14) is configured to calculate the first derivative of the distance between the swimmer and the transducer (2) with respect to time based on the two echo signals; as well as The swimming speed calculation module (15) is configured to calculate the swimming speed of the swimming body based on the radial velocity and the first derivative of the distance.

2. The swimming speed measuring device (1) according to claim 1, wherein: The swimming speed calculation module (15) is also configured to adjust the radial speed based on a comparison of the radial speed with the first derivative of the distance.

3. The swimming speed measuring device (1) according to claim 2, wherein: The swimming speed calculation module (15) is also configured to calculate the swimming speed based on the product of the adjusted radial speed and the distance.

4. The swimming speed measuring device (1) according to claim 3, wherein: The swimming speed calculation module (1) is also configured to calculate the swimming speed based on the product of a linear function of time.

5. The swimming speed measuring device (1) according to claim 4, wherein: The swimming speed calculation module (1) is also configured to calculate the swimming speed based on the slope of the linear function corresponding to the square of the swimming speed.

6. The swimming speed measuring device (1) according to any one of claims 1 to 5, further comprising: The tracking module (12) is configured to track the echo from the same swimming object in the echo signal.

7. The swimming speed measuring device (1) according to any one of claims 1 to 6, wherein: The transducer (2) is a single-beam transducer.

8. The swimming speed measuring device (1) according to any one of claims 1 to 6, wherein: The transducer (2) generates the echo signal by forming one or more receiving beams; as well as The two echo signals are generated using one or more of the receiving beams.

9. A method for measuring swimming speed, comprising: An echo signal is generated based on an ultrasonic pulse using a transducer, the ultrasonic pulse being periodically emitted into the water and reflected by swimming organisms in the water (S11). The radial velocity of the swimming body is calculated based on the phase difference between the two echo signals (S15); Calculate the first derivative of the distance between the swimmer and the transducer with respect to time based on the two echo signals (S16); as well as The swimming speed of the swimming body is calculated based on the first derivative of the radial velocity and the distance (S20).

10. A program that causes a computer to perform the following operations: An echo signal is obtained using a transducer based on ultrasonic pulses, which are periodically emitted into the water and reflected by swimming bodies in the water (S11). The radial velocity of the swimming body is calculated based on the phase difference between the two echo signals (S15); Calculate the first derivative of the distance between the swimmer and the transducer with respect to time based on the two echo signals (S16); as well as The swimming speed of the swimming body is calculated based on the first derivative of the radial velocity and the distance (S20).

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