Fish size calculation device and fish size calculation method

Abstract

To accurately calculate a size of a fish swimming in a fish farm or the like.SOLUTION: A target size calculation device 200 includes: a transducer 22 for transmitting an ultrasonic wave transmission wave toward a target existing in water and receiving a reflected wave from the target to generate an echo signal; a target tracking unit 25 for tracking the target from the echo signal by different transmission waves transmitted from the transducer 22; an incident angle calculation unit 26 for calculating an incident angle of the transmission wave to the tracked target at each position based on the echo signal; a distance calculation unit 27 for calculating distance between a first region of the target tracked from the echo signal and a second region different from the first region regarding each position of the tracked target; and a target size calculation unit 30 for calculating a size of the target tracked based on the incident angle and the distance.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to signal processing for fish group detection in an aquaculture environment, and particularly to the calculation of fish size using ultrasonic waves.

Background Art

[0002] In fish farms, fish are cultured in cages. In order to confirm whether the fish are being cultured as desired, it is necessary to regularly measure the size and weight of the fish. At this time, it is desirable to measure without actually touching the fish so as not to stress or damage the fish (here, measuring without touching the fish is referred to as "remote measurement").

[0003] As a method for remotely measuring fish, conventionally, for example, as disclosed in WO2020 / 090287, a transducer is installed in a net in water stretched in a fish farm, and ultrasonic waves are emitted using a normal fish finder to obtain an echo of the fish group. In a typical fish echo signal obtained from such a fish finder, the horizontal axis of the fish echo signal indicates time, that is, depth, and the vertical axis indicates the intensity of the echo, that is, the signal intensity from the target. And the size of the fish can be calculated by calculating the time difference between two peaks in the fish echo signal. The highest peak indicates the echo received from the swim bladder of the fish, and the other peaks indicate the echoes received from other parts of the body such as the back of the fish.

[0004] However, in conventional fish size calculation devices or methods, there is variation in the values for each measurement, making it difficult to accurately remotely measure the fish size.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] The present invention aims to improve the accuracy of calculating the size of fish swimming in a fish farm. [Means for solving the problem]

[0007] In one embodiment of the present invention, a target size calculation device is provided that includes a transducer, a target tracking unit, an incident angle calculation unit, a distance calculation unit, and a target size calculation unit.

[0008] The transducer is configured to transmit ultrasonic waves towards a target located in water and receive reflected waves from the target to generate an echo signal. The target tracking unit is configured to track the target using echo signals from different transmitted waves sent from the transducer. The incident angle calculation unit is configured to calculate the incident angle of the transmitted waves to the tracked target at each position based on the echo signal. The distance calculation unit is configured to calculate the distance between a first part of the tracked target and a second part different from the first part at each of the above positions on the tracked target, based on the echo signal. The target size calculation unit calculates the size of the tracked target based on the incident angle and the distance.

[0009] Herein, optionally, the target size calculation device may further include an incident angle-distance distribution diagram generation unit that generates a distribution diagram showing the distribution of multiple targets on the incident angle and distance, based on the incident angle and distance calculated for multiple targets, and the target size calculation unit may be configured to calculate the size based on this distribution diagram. This distribution diagram is a histogram showing the distribution of targets on the incident angle and distance, and the incident angle-distance distribution diagram generation unit may be configured to include an incident angle-distance histogram calculation unit that calculates the histogram.

[0010] Furthermore, the system may include a peak extraction unit that extracts a first peak and a second peak different from the first peak from the distribution map, and calculates a first peak distance corresponding to the first peak and a second peak distance corresponding to the second peak on the distribution map. The target size calculation unit may then calculate the average size of multiple targets from the first peak distance and the second peak distance.

[0011] Furthermore, the target size calculation device may be configured such that the target size calculation unit calculates the size of the tracked target when the first incident angle of the transmitted wave to the tracked target at a first timing and the second incident angle of the transmitted wave to the tracked target at a second timing different from the first timing are between a predetermined threshold angle.

[0012] The target size calculation unit may calculate the size of the tracked target based on the distance of the tracked target at the first angle of incidence and the distance of the tracked target at the second angle of incidence.

[0013] Alternatively, the incident angle calculation unit may be configured to calculate the incident angle based on the angle between a first line that temporally connects two different positions of the tracked target and a second line that connects one of the two different positions to the position of the transducer. The incident angle calculation unit may also calculate the incident angle based on the angle between a second line that connects the position of the tracked target to the transducer and a third line that extends vertically from the transducer toward the seabed.

[0014] The incidence angle calculation unit may calculate the incidence angle based on a first distance between the transducer and the first position of the tracked target in a first time instance and a second distance between the transducer and the second position of the tracked target in a second time instance different from the first time instance. Here, the incidence angle calculation unit may be configured to calculate the incidence angle assuming that the first distance and the second distance each change over time based on a hyperbola.

[0015] The target used in the target size calculation device may be a fish, but it can also be other aquatic animals, such as mammals, and the device is widely applicable. Furthermore, the first part may be the swim bladder and the second part may be the outer surface of the fish, but the device is not limited to these and any part can be selected.

[0016] The present invention provides a method for calculating the size of a target underwater, comprising: transmitting a wave from a transducer to a target; generating an echo signal from the reflected wave of the target; tracking the target in time using echo signals from different transmitted waves transmitted from the transducer; and calculating the angle of incidence of the transmitted wave to the target for each position of the tracked target based on the echo signal; and for each position of the tracked target, calculating the distance between a first part of the tracked target and a second part different from the first part from the echo signal, and calculating the size of the tracked target based on the angle of incidence and the distance.

[0017] Here, a distribution map may be generated showing the distribution of multiple targets at the calculated angle of incidence and distance, and the size may be calculated based on this distribution map.

[0018] Furthermore, a first peak and a second peak different from the first peak may be extracted from the distribution map, the first peak distance corresponding to the first peak on the distribution map and the second peak distance corresponding to the second peak may be calculated, and the average size of multiple tracked targets may be calculated based on the first peak distance and the second peak distance.

[0019] In another aspect of the present invention, a computer-executable program is provided which, when executed, transmits a wave from a transducer to a target in water, generates an echo signal from the reflected wave of the target, tracks the target in time from the echo signals of different transmitted waves transmitted from the transducer, calculates the angle of incidence of the transmitted wave to the target for each position of the tracked target based on the echo signals, calculates the distance between a first part of the tracked target and a second part different from the first part for each position of the tracked target based on the echo signals, and calculates the size of the tracked target based on the angle of incidence and the distance. [Effects of the Invention]

[0020] The problem that ultrasound cannot calculate fish weight with sufficient accuracy is solved by calculating the distance between the fish's swim bladder and back at different ultrasonic incidence angles of the transmitted waves. [Brief explanation of the drawing]

[0021] The illustrated embodiments of the subject will be best understood by referring to the drawings. These, as well as other aspects, advantages, and alternatives will be apparent to those skilled in the art by reading the following detailed description with appropriate reference to the accompanying drawings. Here, similar parts are indicated by similar figures throughout.

[0022] Furthermore, the descriptions provided elsewhere in this specification are not intended to limit the subject matter of the invention recited in the claims, but are presented by way of example. The following description is intended solely as an example of the invention and merely shows certain selected embodiments of the apparatus, system, and process that coincide with the subject matter claimed in this application.

[0023] [Figure 1A] Figure 1A shows a fish swimming horizontally. [Figure 1B] Figure 1B shows a fish swimming with its head downward. [Figure 2] Figure 2 is a block diagram showing the overall configuration of a target size calculation device according to a first embodiment of the present invention. [Figure 3] Figure 3 is a perspective view showing how the target size calculation device is used within the cage net of an aquaculture farm according to an embodiment of the present invention. [Figure 4] Figure 4 shows an example of the envelopes of the first, second, and third echo signals generated by a transducer based on the first, second, and third transmission waves T_1, T_2, and T_3, respectively. [Figure 5A] Figure 5A shows a fish being tracked at two positions obtained using two consecutive transmissions T_(n - 1) and T_n by a transducer according to an embodiment of the present invention. [Figure 5B] Figure 5B shows a fish being tracked at two positions obtained using two consecutive transmissions T_(n - 1) and T_n by a transducer according to another embodiment of the present invention. [Figure 5C] Figure 5C shows a fish being tracked at two positions obtained using two consecutive transmissions T_(n - 1) and T_n by a transducer according to yet another embodiment of the present invention. [Figure 6] Figure 6 shows the calculation of the distance between the float bag and the back for a fish being tracked for a given transmission. [Figure 7A] Figure 7A shows a histogram of the ultrasonic incident angle versus the distance between the float bag and the back according to an embodiment of the present invention. [Figure 7B]Figure 7B shows a one-dimensional histogram of the distance between the swim bladder and the back, according to an embodiment of the present invention. [Figure 8] Figure 8 is a graph showing the results of five experiments conducted using yellowtail, a fish species for which average fish weight was calculated. [Figure 9] Figure 9 is a block diagram showing the overall configuration of a target size calculation device according to a second embodiment of the present invention. [Figure 10] Figure 10 shows the first and second ultrasonic incidence angles of the transmitted waves on the tracking fish being tracked on the first and second transmits T_(n-1) and T_n, respectively, by the transducer. [Figure 11A] Figure 11A is a top view illustrating the calculation of the ultrasonic incidence angle when the transducer includes a single receiving channel, according to one embodiment of the present invention. [Figure 11B] Figure 11B is a side view showing the calculation of the ultrasonic incidence angle when the transducer includes a single receiving channel, according to one embodiment of the present invention. [Figure 12] Figure 12 shows the various echo signals generated at different time instances when a fish swims under a transducer with a single receiving channel. [Figure 13] Figure 13 is a flowchart showing a method for calculating the target size according to an embodiment of the present invention. [Modes for carrying out the invention]

[0024] The following illustrates a target size calculation device of the present invention. Exemplary embodiments or features of the invention can be further utilized in other embodiments, and modifications can be made thereto without departing from them. These will be described in detail below with reference to the drawings. The exemplary embodiments described herein are not intended to be limiting. The aspects of the invention generally described herein and shown in the drawings can be arranged, substituted, combined, separated, and designed in a variety of different configurations expressly intended herein.

[0025] The inventors have identified the factors that made it difficult to accurately remotely measure fish size, as explained in the background technology section. Specifically, the distance between the fish's swim bladder and back (hereinafter referred to as "swim bladder-back distance"), i.e., the time (difference) of echo reception, changes depending on the direction from which the ultrasound penetrates the inside of the fish. Therefore, changes in the angle of incidence of the ultrasound, i.e., the angle at which the ultrasound penetrates the inside of the fish, can be a factor that causes errors in calculating the size of the fish. Figures 1A and 1B illustrate the principle that causes such errors. Figure 1A shows a fish 100 swimming horizontally, and Figure 1B shows a fish 100 swimming with its head facing downwards.

[0026] In these two different swimming directions, assuming that ultrasound propagates vertically, the distance between the swim bladder and the dorsal side is 102a when the fish is swimming horizontally as shown in Figure 1A, but 102b when the fish is swimming with its head down as shown in Figure 1B. This distance can differ even for the same species. Note that distances 102a and 102b may differ depending on the fish species, and therefore the difference between them may also differ. The size of the fish is used here to refer to both the literal size of the fish and the weight calculated from its size, given that the species of fish has been identified.

[0027] Figure 2 is a block diagram showing the overall configuration of the target size calculation device 200 according to the first embodiment of the present invention. Figure 3 is a perspective view showing how the target size calculation device 200 is used in a fish farm net 300.

[0028] The fish farm net 300 is a net-like structure that encloses the fish farm in water to prevent fish from escaping. It includes a frame 301, floats 302, a net 303, and a pier 304. The frame 301 is formed in a loop shape to enclose a predetermined area in plan view (viewed from above). By attaching multiple floats 302 to the frame 301, the frame 301 can be made to float on the water surface. The frame 301 is connected to a weight on the bottom of the water by a mooring rope (not shown).

[0029] The upper end of the net 303 is fixed to the frame 301. The net 303 is suspended to partition the water, forming a closed space, within which known species (specific types of fish selected for aquaculture) are farmed. A pier 304 for performing various aquaculture-related tasks is fixed to the frame 301.

[0030] A float 305 is suspended approximately in the center of the frame 301, and the float 305 is connected to the pier 304 by a rope. The target size calculation device 200 in this embodiment is positioned on the float 305. As shown in Figure 2, the target size calculation device 200 comprises a transducer (ultrasonic transducer) 22, a transmitting and receiving unit 23, and a signal processing unit 24.

[0031] The transducer 22 can convert between electrical signals and ultrasonic vibrations, and can detect underwater conditions using the transmitted ultrasonic waves. In this embodiment, the transducer 22 is mounted on the underside of the float 305. The transducer 22 is positioned facing downwards and transmits ultrasonic waves from above the water toward the fish in the fish farm net 300.

[0032] In this embodiment, the transducer 22 includes one transmitter and a receiver having multiple elements divided into four receiving channels.

[0033] In this embodiment, the transducer 22 can acquire the position of an underwater target (such as a fish) based on the difference in timing (i.e., the phase difference of the received reflected waves) between the four receiving channels. As a result, three-dimensional detection using the known split-beam method is achieved. The structure of the transducer 22 can be modified as appropriate.

[0034] The transmitting / receiving unit 23 is connected to the transducer 22 via an electrical cable. The transmitting / receiving unit 23 can output an electrical signal to the transducer 22 via the electrical cable, and the transducer 22 receives this and transmits a transmission wave. The transmitting / receiving unit 23 can acquire the electrical signal acquired by the transducer 22 based on the reflected wave via the electrical cable and convert the electrical signal into a received signal, which is a digital signal.

[0035] The signal processing unit 24 includes a target tracking unit 25, an ultrasonic incidence angle calculation unit 26, a distance calculation unit 27, an ultrasonic incidence angle-distance histogram calculation unit 28, a peak extraction unit 29, and a target size calculation unit 30. In this embodiment, as an example of an underwater target, we will use fish in a fish farm's net enclosure for explanation. Therefore, to facilitate understanding, the target tracking unit 25 will be referred to as the fish tracking unit 25, and the target size calculation unit 30 will be referred to as the fish size calculation unit 30. Similar terminology will be used as appropriate in the explanation of other embodiments.

[0036] The signal processing unit 24 can be configured using a known computer and can be communicatively coupled to the transmitting / receiving unit 23 via a communication cable to acquire received signals from the transducer 22. Specifically, the signal processing unit 24 may include a CPU, ROM, RAM, etc. The ROM, etc., may store a program for realizing the target size calculation method of the present invention.

[0037] Generally, the transducer 22 is configured to convert between electrical signals and ultrasonic vibrations. During transmission, the transducer 22 converts a high-power transmission signal supplied from the transmitting / receiving unit 23 into ultrasound and transmits it into the water. During reception, the transducer 22 receives the reflected wave from the underwater target, converts the reflected wave into an electrical signal, and outputs it to the transmitting / receiving unit 23. The transmitting / receiving unit 23 is configured to amplify and filter the electrical signal.

[0038] The A / D converter converts an electrical signal (analog signal) into a digital signal, which is the received signal, and stores it in the memory (not shown) of the corresponding signal processing unit. Transducer 22 transmits a wave toward an underwater target and generates an echo signal from the reflection of the wave toward the underwater target. Examples of underwater targets include, but are not limited to, fish. The signal processing unit is configured to receive, store, and process the echo signal in order to measure the length, width, height, and / or weight of the fish underwater.

[0039] The calculation of fish size is not limited to fish farmed in the fish pen net 300. For example, if the fish species of a school of fish can be estimated by a fisherman, or if the species can be identified by a conventional fish finder capable of identifying fish species, the target size calculation device 200 may be attached to a fishing boat and used as a device to estimate the size of fish in a school of fish.

[0040] Figure 4 shows an example of envelopes 400 for the first, second, and third echo signals 401, 402, and 403, respectively, generated by transducer 22 based on the first transmit wave T_1, the second transmit wave T_2, and the third transmit wave T_3. The first, second, and third transmit waves T_1, T_2, and T_3 are transmitted sequentially, and the corresponding echo signals 401, 402, and 403 are stored in memory (not shown).

[0041] In Envelope 400, the horizontal axis represents time, and the vertical axis represents the target signal strength (Target Strength TS), which indicates the intensity of the received echo signal. The target signal strength is a parameter that indicates the extent to which some of the ultrasound scattered after hitting a fish returns in the direction of incidence, and can be considered to be substantially the same as the echo strength.

[0042] The fish tracking unit 25 tracks fish in an underwater target in time from first, second, and third echo signals 401, 402, and 403 generated from different transmitted waves. The fish tracking unit 25 is configured to extract swim bladder peaks in the echo signals 401, 402, and 403. The fish tracking unit 25 determines whether the signal intensity of the target is above a predetermined detection threshold. Echo signal peaks exceeding the predetermined threshold can be considered echoes originating from the fish's swim bladder (hereinafter referred to as "swim bladder peak echoes" as appropriate).

[0043] Generally, the ultrasound transmitted from transducer 22 is most strongly reflected from the swim bladder among the various parts of the fish. Therefore, as shown in Figure 4, when the target signal intensity (TS) shows a maximum peak, this peak is thought to originate from the reflected waves reflected by the swim bladder. Echo signal peaks below a predetermined threshold correspond to echoes from other parts of the fish's body, such as the dorsal side. Here, the threshold is -40 dB, and the first echo signal 401 includes the swim bladder peak P1, the second echo signal 402 includes the swim bladder peak P2, and the third echo signal 403 includes two swim bladder peaks P3 and P4.

[0044] The fish tracking unit 25 determines, for each swim bladder peak echo in a given echo signal, whether there is a swim bladder peak corresponding to a previous transmitted wave that occurred at approximately the same time. If such a peak exists, the two swim bladder peak echoes can be considered to actually come from the same fish. In one example, peaks P1, P2, and P3 can be considered to have occurred at approximately the same time and therefore originate from the same fish.

[0045] The fish tracking unit 25 performs fish tracking by comparing the peak positions of echo signals from two consecutive transmissions. There is no limit to the number of consecutive transmissions, and two or more transmissions can be used for fish tracking. The fish tracking unit 25 can employ sophisticated tracking algorithms for fish tracking, such as prediction using a Kalman filter.

[0046] Figure 5A shows a target fish 500 being tracked at two locations using two consecutive transmissions T_(n-1) and T_n from transducer 22. For each location of the target fish 500, the ultrasonic incidence angle calculation unit 26 calculates the ultrasonic incidence angle of the transmitted wave relative to the target fish 500 based on the echo signal. This allows the ultrasonic incidence angle calculation unit 26 to calculate the angle at which the transmitted wave enters the target fish 500. In connection with the present invention, transducer 22 may include multiple transducer elements (which can also be called channels) at reception. The ultrasonic incidence angle calculation unit 26 can calculate the direction of arrival (DOA) of the echo from the target fish 500 using conventional interferometry, i.e., the phase difference between echo signals received by multiple transducer elements of transducer 22.

[0047] In this embodiment, the transducer 22 may include multiple receiving channels, and the direction of arrival of the reflected wave can be obtained by interferometry (conventionally also known as the split-beam method). Each receiving channel is located at a different position from the others and has a different directivity from the others, and receives the reflected wave reflected from a target in water. The transducer 22 then converts the received reflected wave into an electrical signal. Using the split-beam method, the angle between the direction of arrival of the reflected wave and the central axis of the transmitted wave is calculated based on the phase difference of the electrical signals received in the receiving channels.

[0048] The ultrasonic incidence angle calculation unit 26 calculates the three-dimensional position of the tracking fish 500 in each transmission. In particular, for each position, the ultrasonic incidence angle calculation unit 26 calculates the distance between the tracking fish 500 and the transducer 22 based on the time difference between the transmission and reception of the tracking fish 500's echo. Then, the ultrasonic incidence angle calculation unit 26 calculates the three-dimensional position of the tracking fish 500 relative to the transducer 22 based on the DOA corresponding to the tracking fish's echo and the distance between the tracking fish 500 and the transducer 22. The position of the tracking fish 500 relative to the transducer 22 constitutes the fish-transducer vector 503, but this position may change when moving from one transmission to another.

[0049] The ultrasonic incidence angle calculation unit 26 further calculates the previous transmission T_(n-) of the tracking fish 500. 1) Based on the position change from the current transmission T_n, the swimming direction vector 504 of the pursuing fish 500 is calculated. The ultrasonic incidence angle calculation unit 26 calculates the ultrasonic incidence angle by calculating the angle between a first line (i.e., the swimming direction vector 504) that temporally connects two different positions of the pursuing fish 500 and a second line (i.e., vector 503) that connects one of the two different positions to the position of the transducer 22. For each position of the pursuing fish, the ultrasonic incidence angle calculation unit 26 calculates the ultrasonic incidence angle of the transmitted wave relative to the pursuing fish 500 based on equation 1.

number

[0050] The ultrasonic incidence angle is the complementary angle of the angle between the swimming direction vector 504 and the fish-transducer vector 503. In one example, the ultrasonic incidence angle is zero for a fish that is vertically below the transducer 22 and swimming horizontally. The definition of the ultrasonic incidence angle is not limited to the complementary angle described above; for example, as shown in Figure 5B, the angle between the swimming direction vector 504 and the fish-transducer vector 503 can also be used as the definition of the ultrasonic incidence angle. Thus, in another embodiment of the present invention, the ultrasonic incidence angle can be calculated based on Equation 2.

number

[0051] In yet another embodiment of the present invention, the ultrasonic incidence angle calculation unit 26 calculates the ultrasonic incidence angle by calculating the angle between a second line connecting the position of the tracking fish 500 and the transducer 22 (i.e., the fish-transducer vector 503) and a third line which is a vertical line from the transducer 22 to the seabed (i.e., the vertical vector 505), as shown in Figure 5C. Thus, the ultrasonic incidence angle can be defined as the angle between the fish-transducer vector 503 and the vertical vector 505.

[0052] In this embodiment, the ultrasonic incidence angle calculation unit 26 calculates the ultrasonic incidence angle of the transmitted wave relative to the pursuing fish 500 for each position of the pursuing fish 500 based on equation 3.

number

[0053] In the above embodiment, the transducer 22 is assumed to transmit vertically downward from above the pursuing fish 500. The transducer 22 may also be positioned to transmit vertically upward from below the pursuing fish 500.

[0054] In the embodiments described above, the transducer 22 includes multiple receiving channels, and the ultrasonic incidence angle is calculated using the conventional split-beam method to determine the position of the fish within the beam of the transducer 22; however, the scope of the present invention is not limited thereto. In another embodiment of the present invention, the transducer 22 may have a single receiving channel, and the ultrasonic incidence angle may be calculated using an appropriate method. The calculation of the ultrasonic incidence angle when the transducer 22 includes a single receiving channel will be described later.

[0055] Figure 6 shows the calculation of the swim bladder-to-back distance of the tracking fish 500 for a given transmission. The swim bladder-to-back distance is the distance between the swim bladder and the back of the tracking fish 500, and is calculated based on the time difference between the peak P5 of the echo signal corresponding to the swim bladder (hereinafter referred to as the "swim bladder peak") and the peak P6 of the echo signal corresponding to the back of the tracking fish 500 (hereinafter referred to as the "back peak"). Specifically, to convert the time difference into distance, the time difference is multiplied by the speed of sound of ultrasound in water (usually 1500 m / sec). For the sake of simplification, the explanation of the conversion from time difference will be omitted as appropriate in the following explanation.

[0056] The distance calculation unit 27 in Figure 2 calculates the time difference between the swim bladder peak P5 and the peak P6 corresponding to another part (body part) of the pursuing fish for each position of the pursuing fish. The distance calculation unit 27 then converts this time difference into the swim bladder-to-back distance. The other body part is not limited to the back; it may also be the fish's belly as another outer surface of the fish, or the fish's spine as an internal part of the fish.

[0057] To detect the echo reflected from the back of the pursuing fish 500, the following processing may be performed. That is, when the transducer 22 transmits ultrasonic waves from above to below the pursuing fish 500, the echo with the maximum echo intensity (target signal intensity TS) may be considered as the echo reflected from the swim bladder of the pursuing fish 500, and the peak of the echo signal that appears just before the swim bladder peak may be considered as the echo from the back of the fish 500, thereby detecting the echo reflected from the back of the pursuing fish 500.

[0058] To reliably confirm that the peak before the swim bladder peak actually corresponds to the peak on the back of the fish 500, the processing circuit (not shown) of the distance calculation unit 27 may check the following conditions. That is, the processing extends before the peak on the fish's back and checks whether there is another peak with at least a predetermined echo signal intensity within a predetermined time interval of a predetermined period starting from the peak on the fish's back. If no other peak exists within the predetermined time interval, the peak that appears immediately may be detected as the back of the fish with high accuracy, assuming it corresponds to the back of the fish. Furthermore, as another processing step, it checks whether there is a section below a threshold before the peak on the fish's back, and whether there is a temporal section starting from the peak on the fish's back where the echo signal intensity exceeds the threshold. If there is no echo signal intensity exceeding the threshold within the predetermined time interval, the peak that appears immediately may be detected as the back of the fish with high accuracy, assuming it corresponds to the back of the fish.

[0059] In the above embodiment, the swim bladder-to-dorsal distance of the fish is calculated, but it is not necessarily limited to this. Alternatively, the time difference between the swim bladder peak and other peaks in the echo signal of the same fish may be used.

[0060] Figure 7A shows a histogram 700 (i.e., a 2D histogram) of swim bladder-to-back distance against ultrasonic incidence angle according to an embodiment of the present invention. The ultrasonic incidence angle-distance histogram calculation unit 28 in Figure 2 calculates the swim bladder-to-back distance histogram 700 against ultrasonic incidence angle from the ultrasonic incidence angle and swim bladder-to-back distance calculated for a large number of pursuing fish. By repeatedly performing calculations in the fish tracking unit 25, ultrasonic incidence angle calculation unit 26, and distance calculation unit 27 over a large number of transmission and reception cycles, a large number of pursuing fish can be obtained for which swim bladder-to-back distance and ultrasonic incidence angle have been calculated. The histogram 700 is generated using this large number of swim bladder-to-back distance and ultrasonic incidence angle data.

[0061] To generate histogram 700, the entire range of values ​​for the swim bladder-to-dorsal distance data and the entire range of values ​​for the ultrasonic incidence angle data are divided into a series of intervals, and the number of occurrences of values ​​corresponding to each interval is counted. Histogram 700 represents this count.

[0062] The dark regions in histogram 700 (areas where the bars in the histogram are dark black) indicate the most frequently occurring combinations of (ultrasonic incidence angle, buoyancy-to-dorsal distance). Two dark regions are observed in histogram 700, which indicate the ultrasonic incidence angles at which the buoyancy-to-dorsal distance was most frequently measured.

[0063] As described above, transducer 22 is positioned to transmit waves downwards from near the water surface. Therefore, negative values ​​on the horizontal axis represent the dorsal side of the fish relative to the swim bladder position (reference position), and positive values ​​represent the ventral side of the fish relative to the swim bladder position.

[0064] The peak extraction unit 29 in Figure 2 extracts the first and second peaks from the histogram 700 corresponding to the two dark regions in Figure 7A, and calculates the first peak distance H1 for the first peak and the second peak distance H2 for the second peak on the histogram 700. The first and second peak distances H1 and H2 are shown with reference to Figure 7A.

[0065] An example of how to extract the second peak from histogram 700 is described below. To extract the second peak, only the data from the two-dimensional histogram 700 that has an ultrasonic incidence angle between [0 and 10 degrees] is extracted, and this is rearranged in Figure 7B into a one-dimensional histogram 702 that shows the histogram (number of occurrences) of the buoyancy-to-dorsal distance (i.e., the horizontal axis in Figure 7B) for ultrasonic incidence angles between [0 and 10 degrees].

[0066] The horizontal axis of the one-dimensional histogram 702 is the same as the horizontal axis of the two-dimensional histogram 700. The vertical axis of the one-dimensional histogram 702 shows the number of occurrences, which is equal to the total number of occurrences in the ultrasonic incidence angle range [0 to 10 degrees] of the two-dimensional histogram 700.

[0067] This one-dimensional histogram 702, which focuses only on the ultrasonic incidence angle between [0 and 10 degrees], more clearly emphasizes the second peak, i.e., the right-hand peak in both Figure 7A and Figure 7B.

[0068] To extract the first peak, only the data for histogram 700 with ultrasonic incidence angles between [-20 degrees and 0] is extracted from the two-dimensional histogram 700, and then rearranged into a one-dimensional histogram (not shown) using the same principle as above to emphasize the first peak, i.e., the peak on the left side of Figure 7A.

[0069] To remove noise in the one-dimensional histogram 702, the peak extraction unit 29 may apply a moving average to the one-dimensional histogram 702.

[0070] Next, the peak extraction unit 29 uses the one-dimensional histogram 702 that emphasizes the first peak and the one-dimensional histogram 702 that emphasizes the second peak, respectively, to calculate the first peak distance H1 for the first peak and the second peak distance H2 for the second peak. Figure 7B shows the second peak distance H2, which refers to the distance on the horizontal axis between the position of the second peak on the horizontal axis (i.e., the position where the second peak is maximum) and the reference position on the horizontal axis (the position of the swim bladder). The method of extracting the first and second peaks from the histogram 700 described above and calculating the first peak distance H1 and the second peak distance H2 converts the two-dimensional histogram 700 into a one-dimensional histogram 702. There are several conventional methods for extracting peaks and calculating the distance between those peaks and the reference position, so the above method does not particularly reduce the complexity of the process. The 0 to 10 degree and -20 to 0 degree ranges used for peak extraction are also not limited and may vary depending on the fish species and maturity of the fish in the fish farm net 300.

[0071] The fish size calculation unit 30 in Figure 2 calculates the average size of multiple pursuing fish from the first peak distance and the second peak distance. Specifically, the average fish size Wm can be calculated using formula 4.

number

[0072] The ultrasonic incidence angle-distance histogram 700 in Figure 7A contains two peaks, but there is no limit to the number of peaks; there may be three or more. Based on the fish species, the ultrasonic incidence angle-distance histogram calculation unit 28 can calculate a histogram with three or more peaks and calculate the average fish size Wm using formula 5.

number

[0073] Although not shown in the diagram, the signal processing unit 24 generates display data for displaying data related to the size of the fish, and may output the display data as appropriate to a display device connected to the signal processing unit 24.

[0074] Graph 800, shown in Figure 8, shows the results of five experiments in which the average fish size of the yellowtail species was calculated using the target size calculation device 200 of the present invention and applying the conventional fish size calculation method (described in WO2020 / 090287). In Graph 800, the horizontal axis represents the true fish size (average size of fish in the fish farm net 300 measured by a weighing scale), and the vertical axis represents the average fish size calculated by the conventional method and the method of the present invention. The conventional method resulted in an average error of 7.8%, while the method of the present invention resulted in an average error of 3.8%.

[0075] Figure 9 is a block diagram showing the overall configuration of a target size calculation device 900 according to a second embodiment of the present invention.

[0076] The target size calculation device 900 of the second embodiment differs from the target size calculation device 200 of the first embodiment in the configuration of the fish size calculation unit 901. The target size calculation device 900 also does not include the ultrasonic incidence angle-distance histogram calculation unit and peak extraction unit of the first embodiment.

[0077] The fish size calculation unit 901 calculates the fish size for each pursuing fish. Here, the weight of the pursuing fish is assumed as the fish size, but the body length or body height of the pursuing fish may also be used. When a fish is pursued by multiple transmitted waves, the ultrasonic incidence angle calculation unit 26 calculates the ultrasonic incidence angle of the transmitted wave for the pursuing fish for each transmission.

[0078] Figure 10 shows the first ultrasonic incidence angle 1000 and the second ultrasonic incidence angle 1001 of the transmitted waves on the tracking fish 1002 being tracked on the first transmission T_(n-1) and the second transmission T_n, respectively, by the transducer 22, and these are illustrated as defined by equation (2) and Figure 5B. However, there are no restrictions on these, and they can also be illustrated as defined by equation (1) and Figure 5A, or as defined by equation (3) and Figure 5C. The fish size calculation unit 901 compares each of the first and second ultrasonic incidence angles with a predetermined threshold angle and calculates the size of the tracking fish 1002 if there is a predetermined threshold angle between the first and second ultrasonic incidence angles.

[0079] In one embodiment, if it is determined that the second ultrasonic incidence angle is greater than a predetermined threshold angle and the first ultrasonic incidence angle is smaller than a predetermined threshold angle, the fish size calculation unit 901 extracts the swim bladder-to-back distance at the first and second ultrasonic incidence angles from the distance calculation unit 27. Then, the fish size calculation unit 901 calculates the individual fish size Wi of the pursuing fish based on formula 6.

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[0080] If the predetermined threshold angle is not between the first ultrasonic incidence angle and the second ultrasonic incidence angle, that is, if both the first and second ultrasonic incidence angles are greater than the predetermined threshold, or if both the first and second ultrasonic incidence angles are less than the predetermined threshold, the fish size calculation unit 901 extracts the swim bladder-to-back distance from the distance calculation unit 27 at either the first or second ultrasonic incidence angle.

[0081] Alternatively, the fish size calculation unit 901 may extract the swim bladder-to-dorsal distance at both the first and second ultrasonic incidence angles and calculate the average of the two. Based on the extracted swim bladder-to-dorsal distance, or the average swim bladder-to-dorsal distance, the fish size Wi of the individual chasing fish is calculated. In one embodiment, if both the first and second ultrasonic incidence angles are found to be greater than a predetermined threshold angle (i.e., when only H2 is available), equation 6 can be modified to equation 7.

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[0082] The fish size calculation unit 901 is shown to calculate the size of the tracking fish based on tracking the fish through two transmissions, but the fish size may also be calculated based on tracking the fish through two or more transmissions.

[0083] In one embodiment, if three transmissions are used to calculate the weight of a fish, and one ultrasonic incidence angle is less than a predetermined threshold angle, and the other two ultrasonic incidence angles are greater than a predetermined threshold angle, the swim bladder-to-dorsal distances at the other two ultrasonic incidence angles may be averaged before using them in Equation 6.

[0084] In this way, the fish size calculation unit 901 calculates the fish size for each chasing fish and determines the distribution of fish sizes within the fish farm net when calculating the fish sizes of multiple chasing fish. The fish size calculation unit 901 provides more information than the fish size calculation unit 30 of the first embodiment, which calculates the average size of fish in the fish farm net 300, namely information regarding the distribution of fish sizes within the fish farm net.

[0085] Figure 11A is a top view showing the calculation of the ultrasonic incidence angle when the transducer 22 includes a single receiving channel, according to one embodiment of the present invention. Figure 11B is a side view showing the calculation of the ultrasonic incidence angle when the transducer 22 includes a single receiving channel, according to one embodiment of the present invention.

[0086] As shown in Figures 11A and 11B, the chasing fish 1100 are positioned in a fixed location within the fish farm net 300 and swim linearly below a single beam transducer 22 (i.e., a transducer 22 containing a single receiving channel) that is directed vertically downward.

[0087] In Figures 11A and 11B, the transducer 22 is shown to be positioned at the center of a three-dimensional Cartesian coordinate system, and the pursuing fish 1100 is assumed to be swimming at a distance r from the transducer 22 at a velocity v.

[0088] At time t=0, the pursuing fish 1100 crosses the YZ plane. The distance r changes with time t according to the following equation (hyperbola), equation 8.

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[0089] As shown in Figure 11B, the ultrasonic incidence angle is the angle between the fish-transducer vector 1101 (i.e., the line connecting the pursuing fish 1100 and the transducer 22) and the perpendicular vector 1102 (i.e., a second line perpendicular to the direction in which the pursuing fish 1100 is swimming).

[0090] The angle of incidence of ultrasound at time t can be expressed using the equation shown in Equation 9.

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[0091] Figure 12 shows various echo signals, i.e., echo signals 1201, 1202, 1203, and 1204 generated during different time instances (transmission timings), i.e., pings n, n+1, n+2, and n+3, respectively, when a tracking fish 1100 swims under a single receiving channel transducer 22. Note that ping refers to one circle in which the transducer 22 transmits and receives ultrasound.

[0092] The distance between each ping, corresponding to the distance from the tracking fish 1100 to the transducer 22, can be calculated by measuring the time required for the transmission and reception of ultrasonic waves reflected from the swim bladder of the tracking fish 1100. This distance is obtained by multiplying the time required for transmission and reception by the speed of sound of ultrasonic waves in water and dividing by 2. The distance r for each ping is shown in Table 1. [Table 1]

[0093] Referring again to Figure 11B, it is assumed that the distance between the pursuing fish 1100 and the transducer 22 changes with respect to time, according to the hyperbolic equation 10.

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[0094] The parameters a, b, and c in equation 10 can be determined, for example, using the least squares method. Based on equations 8 and 10, the fish's velocity v and time tp are calculated using equations 11 and 12.

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[0095] Here, the ultrasonic incidence angle calculation unit 26 calculates the ultrasonic incidence angle by substituting the value of the speed v of the pursuing fish 1100 and the time tp for each ping into equation 9. In relation to the present invention, when the transducer 22 generates a first echo signal 1201 and a second echo signal 1202 based on a first ultrasonic ping n and a second ultrasonic ping n+1 (i.e., the first ping n and the second ping n+1), the first distance rn and the second distance r_(n+1) are calculated as described above.

[0096] In this embodiment, a second ultrasonic wave is transmitted after a first ultrasonic wave. Thus, in the second time instance, the ultrasonic incidence angle calculation unit 26 calculates a second incidence angle θ_(n+1) based on a first distance rn between the pursuing fish 1100 and the transducer 22 in the first echo signal 1201 and a second distance r_(n+1) between the pursuing fish 1100 and the transducer 22 in the second echo signal 1202. The ultrasonic incidence angle calculation unit 26 assumes that the first distance rn and the second distance r_(n+1) each change while maintaining a hyperbolic relationship with respect to time, and calculates the second incidence angle θ_(n+1) using equation 10. As a variation, instead of just two distances, the first distance rn and the second distance r_(n+1), three or more distances (for example, a first distance rn, a second distance r_(n+1), and a third distance r_(n+2)) may be used. In this case, for example, the ultrasonic incidence angle calculation unit 26 assumes that the first distance rn, the second distance r_(n+1), and the third distance r_(n+2) each change while maintaining a hyperbolic relationship with respect to time, and calculates the third incidence angle θ_(n+2) using equation 10.

[0097] Figure 13 is a flowchart of a method 1300 for calculating a target size according to an embodiment of the present invention. Each step in this method has already been described with reference to Figures 2 to 9.

[0098] In step 1302, the transducer 22 transmits a wave toward the underwater target and generates an echo signal from the reflection of the wave toward the underwater target.

[0099] In step 1304, the fish tracking unit 25 tracks the fish in the underwater target in time from echo signals generated from different transmitted waves.

[0100] In step 1306, the ultrasonic incidence angle calculation unit 26 calculates the ultrasonic incidence angle of the transmitted wave of the pursuing fish based on the echo signal for each temporal position of the pursuing fish.

[0101] In step 1308, the distance calculation unit 27 calculates the distance between the swim bladder of the pursuing fish and another part of the fish from the echo signal of the pursuing fish for each position of the pursuing fish.

[0102] In step 1310, the fish size calculation units 30 and 901 calculate the size of the pursuing fish based on the ultrasonic incidence angle and the calculated distance.

[0103] Not all objectives or benefits can necessarily be achieved by following any particular embodiment described herein. Therefore, for example, a person skilled in the art may configure a particular embodiment to operate in a manner that achieves or optimizes one benefit or set of benefits taught herein, without necessarily achieving other objectives or benefits taught or suggested herein.

[0104] Furthermore, although the embodiments described the calculation of the size of fish swimming in a fish farm where the effects of the present invention are demonstrated, the invention is not limited to fish farms in terms of accurately calculating the size of fish. Also, although fish were used as an example to explain the target for size calculation, the invention can be applied to mammals such as dolphins, as long as it is a target in which two or more echo signal peaks can be captured among aquatic organisms. In one embodiment, the size was calculated based on the distance between the swim bladder and the back of the fish, but it is not limited to the back and may be other parts of the external surface of the fish.

[0105] In one embodiment, the relationship between the ultrasonic incidence angle and distance is represented in a histogram, and a first peak and a second peak are extracted using this histogram. The first peak distance corresponding to the first peak on the histogram and the second peak distance corresponding to the second peak are then calculated. The calculation of the first and second peak distances is not limited to a histogram; more broadly, based on the incidence angles and distances calculated for multiple targets, the number of targets within each predetermined range of incidence angles and each predetermined range of distances can be calculated, and a distribution map showing the distribution can be generated. For example, the number of fish corresponding to the ranges divided by incidence angle and distance can be counted using dots, and the first and second peak distances can be calculated based on this count.

[0106] All processes described herein are embodied in software code executed by a computing system including one or more computers or processors, and may be fully automated. The software code may be stored in any type of non-temporary computer-readable medium or other computer storage device. Some or all of these methods may be embodied in dedicated computer hardware.

[0107] Many other modifications not described herein will be apparent from this disclosure. For example, depending on the embodiment, any particular operation, event, or function of any of the algorithms described herein may be performed in different sequences and may be added, combined, or excluded as a whole (for example, not all described actions or events are required to perform the algorithm).

[0108] Furthermore, in certain embodiments, operations or events are executed not sequentially, but in parallel, for example, through multithreading, interrupt handling, or via multiple processors or processor cores, or on other parallel architectures. Additionally, different tasks or processes can be executed by different machines and / or computing systems that can work together.

[0109] Various exemplary logic blocks and parts described in connection with embodiments disclosed herein can be implemented or executed by a machine such as a processor. The processor may be a microprocessor, or alternatively, a controller, microcontroller, state machine, or a combination thereof. The processor may include executable instructions that include electrical circuits configured to process computer executable instructions. In another embodiment, the processor may include an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable device that performs logical operations without processing computer executable instructions.

[0110] A processor can also be implemented as a combination of computing devices, for example, a combination of a digital signal processor (DSP) and a microprocessor, multiple microprocessors, one or more microprocessors combined with a DSP core, or any other such configuration.

[0111] This specification primarily describes digital technologies, but processors may also primarily include analog components. For example, some or all of the signal processing algorithms described herein can be implemented by analog circuits or mixed analog and digital circuits. The computing environment may include, but is not limited to, any type of computer system based on microprocessors, mainframe computers, digital signal processors, portable computing devices, device controllers, or computing engines within devices.

[0112] Any process description, element, or block in the flowcharts described herein and / or shown in the accompanying drawings should be understood as potentially representing a section, segment, or part of code, including one or more executable files. [Explanation of symbols]

[0113] 22 transducers 23 Transmitter / Receiver 24 Signal Processing Unit 25 Fish tracking unit (target tracking unit) 26 Ultrasonic incidence angle calculation section 27 Distance Calculation Unit 28 Ultrasonic Incidence Angle-Distance Histogram Calculation Unit 29 Peak extraction section 30. Fish size calculation unit (target size calculation unit) 100 fish 102a Distance between swim bladder and dorsal surface (when the fish is swimming horizontally) 102b Swim bladder-to-dorsal distance (when the fish is swimming downwards) 200 Fish size calculation device (target size calculation unit) 300 fish tank nets 301 Frame 302 Float 303 Net Pier 304 305 Float 400 Envelope 401 Echo signal 402 Echo signal 403 Echo signal 500 Tracking Fish 503 Fish - Transducer Vector 504 Swimming direction vector 505 Vertical vector 900 Fish Size Calculation Device 901 Fish size calculation unit 1100 Tracking fish 1101 Tracking fish 1102 Ultrasonic incidence angle 1201 Echo signal 1202 Echo signal 1203 Echo signal 1204 Echo signal

Claims

1. A transducer that transmits ultrasonic waves towards one or more targets located in water, receives reflected waves from the targets, and generates an echo signal. A target tracking unit that tracks the target from echo signals of different transmission waves transmitted from the transducer, An incidence angle calculation unit that calculates the incidence angle of the transmitted wave to the tracked target at each position based on the echo signal, A distance calculation unit calculates the distance between a first part of the tracked target and a second part different from the first part for each of the positions of the tracked target, based on the echo signal. The system includes a target size calculation unit that calculates the size of the tracked target based on the angle of incidence and the distance. The aforementioned target is a fish of a known species. The first part mentioned above is a swim bladder. Target size calculation device.

2. A target size calculation device according to claim 1, further, An incident angle-distance distribution diagram generation unit generates a distribution diagram showing the distribution of the multiple targets in terms of incident angle-distance, based on the incident angle and distance calculated for multiple targets. The system includes a peak extraction unit that extracts a first peak and a second peak different from the first peak from the distribution map, and calculates a first peak distance corresponding to the distance between the position of the first peak and the position of the swim bladder on the distribution map, and a second peak distance corresponding to the distance between the position of the second peak and the position of the swim bladder, respectively. The target size calculation unit calculates the average size of the plurality of targets from the first peak distance and the second peak distance. Target size calculation device.

3. A target size calculation device according to claim 2, The distribution diagram is a histogram showing the distribution of the target along the angle of incidence and distance. The incident angle-distance distribution diagram generation unit includes an incident angle-distance histogram calculation unit that calculates the histogram. Target size calculation device.

4. A target size calculation device according to claim 1, The target size calculation unit calculates the size of the tracked target when there is a predetermined threshold angle between the first incidence angle of the transmitted wave to the tracked target at a first timing and the second incidence angle of the transmitted wave to the tracked target at a second timing different from the first timing. Target size calculation device.

5. A target size calculation device according to claim 4, The target size calculation unit calculates the size of the tracked target based on the distance of the tracked target at the first angle of incidence and the distance of the tracked target at the second angle of incidence. Target size calculation device.

6. A target size calculation device according to any one of claims 1 to 5, The incident angle calculation unit calculates the incident angle based on the angle formed by a first line that temporally connects two different positions of the tracked target and a second line that connects one of the two different positions to the position of the transducer. Target size calculation device.

7. A target size calculation device according to any one of claims 1 to 5, The incident angle calculation unit calculates the incident angle based on the angle formed by a second line connecting the position of the tracked target and the transducer, and a third line extending vertically from the transducer toward the bottom of the water. Target size calculation device.

8. A target size calculation device according to any one of claims 1 to 5, The incident angle calculation unit calculates the incident angle based on a first distance between the transducer and the first position of the tracked target in a first time instance and a second distance between the transducer and the second position of the tracked target in a second time instance different from the first time instance. Target size calculation device.

9. A target size calculation device according to claim 8, The incident angle calculation unit calculates the incident angle assuming that the first distance and the second distance change over time based on a hyperbola. Target size calculation device.

10. A target size calculation device according to claims 1 to 9, The second part is the outer surface of the fish, and the device is a target size calculation device.

11. A method for calculating the size of one or more targets in water, A transducer transmits a wave towards the target, and generates an echo signal from the reflected wave of the target. The target is tracked in time from echo signals from different transmission waves transmitted from the transducer, Based on the echo signal, the incidence angle of the transmitted wave onto the tracked target is calculated for each position of the target. For each of the positions of the tracked target, the distance between a first part of the tracked target and a second part different from the first part is calculated from the echo signal. The size of the tracked target is calculated based on the angle of incidence and the distance. The aforementioned target is a fish of a known species. The first part mentioned above is a swim bladder. Method for calculating target size.

12. A method for calculating the target size according to claim 11, further, Based on the incident angle and distance calculated for multiple targets, a distribution map is generated showing the distribution of the multiple targets at the incident angle and distance. From the aforementioned distribution map, a first peak and a second peak different from the first peak are extracted. A first peak distance, which corresponds to the distance between the position of the first peak on the distribution map and the position of the swim bladder, and a second peak distance, which corresponds to the distance between the position of the second peak and the position of the swim bladder, are calculated. The average size of the plurality of targets is calculated based on the first peak distance and the second peak distance. Method for calculating target size.

13. A program that can be executed by a computer, when executed, A transducer transmits a wave to one or more targets in the water, and generates an echo signal from the reflected wave of the targets. The target is tracked in time from echo signals from different transmission waves transmitted from the transducer, Based on the echo signal, the incidence angle of the transmitted wave onto the tracked target is calculated for each position of the target. For each of the positions of the tracked target, the distance between a first part of the tracked target and a second part different from the first part is calculated from the echo signal. The size of the tracked target is calculated based on the angle of incidence and the distance. The aforementioned target is a fish of a known species. The first part mentioned above is a swim bladder. A program for calculating target size.

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