JPS6351510B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device that emits ultrasonic waves into the sea from the bottom of a ship and measures the moving speed of a school of fish based on the Doppler effect generated in reflected waves reflected from the seabed or a school of fish. The present invention relates to a detection method for calculating moving speed with high accuracy.

Conventionally, this type of measurement device emits ultrasonic waves diagonally downward from a transducer installed on the bottom of the ship in the direction of the bow and stern line, and a transducer in the transverse direction perpendicular to the bow and stern line. Detects the Doppler frequency generated in reflected waves reflected from the seabed or fish schools in the front-back and left-right directions, averages these detected data to determine the ship's speed relative to the sea bed or fish school, and calculates the speed of the fish school relative to the bow direction. At the same time, a device is known in which the true moving speed of the school of fish is calculated and displayed from the speed of the school of fish and azimuth information such as a gyroscope.

Conventional measurement devices configured in this way usually use a phase lock circuit in the Doppler frequency detection circuit, so averaging processing is performed on the Doppler frequency in the direction of ultrasonic emission, and when the ship is turning, This method has the drawback of causing a large error in the moving speed of the school of fish.

Therefore, a method for calculating the moving speed of a school of fish using a conventional measuring device will be explained with reference to conceptual diagrams shown in FIGS. 1 to 3. That is, FIG. 1 shows a state of follow-up delay when the ship turns by an angle A from constant speed navigation. FIG. 2 shows the relationship between the speed of the ship relative to the seabed, the speed relative to the school of fish, and the moving speed of the school of fish during constant speed navigation. FIG. 3 shows the speed of the ship relative to the seabed, the speed of the ship relative to the school of fish, and the moving speed of the school of fish in both true and calculated values when the ship turns by an angle A from constant speed navigation.

Generally, measured values vary with some error around the true value, so it is common to average the measured values and display them. Therefore, if there is an acceleration component, this appears as a delay in tracking. Next, the error in calculating the moving speed of a school of fish when conventional averaging processing is performed will be described in detail. Note that for the sake of simplicity, it is assumed that the measured value is the true value. Further, in FIGS. 1 to 3, y indicates the bow direction, x indicates the starboard direction, and the xy coordinates are formed by the front, rear, left and right of the ship. Furthermore, V〓 represents a velocity vector, v〓 _x represents a component in the x direction, and v〓 _y represents a component in the y direction, and these are assumed to be given as measured values. In this case, α is O, I, N, B, W,
Represents T.

[1] Follow-up delay when turning by angle A from constant speed navigation in Figure 1 V _O (v _Ox , v _Oy ): Vessel speed calculated by averaging the previous measured values V _I (v _Ix , v _Iy ): Current measured value V _N (v _Nx , v _Ny ): Ship speed calculated by averaging the current measured value Under the above conditions, the average processing value with K as the time constant, etc. The formula is as follows.

v _Nx = (v _Ix −v _Ox +K・v _Ox )/K ...(1) v _Ny = (v _Iy −v _Oy +K・v _Oy )/K ...(2) Therefore, the tracking delay is ΔV (Δv _x , Δv _y ) is as follows.

Δv _x = v _Ix −v _Nx = (1-1/K) (v _Ix −v _Ox ) ...(3) Δv _y = v _Iy −v _Ny = (1-1/K) (v _Iy −v _Oy ) ...(4) [2] Regarding the case where the ship is sailing at a constant speed with respect to the seabed and fish school in Figure 2 V _B (v _Bx , v _By ): The speed of the ship measured this time with respect to the sea bed V _W (v _Wx , v _Wy ): Speed of the ship measured this time with respect to the school of fish V _T (v _Tx , v _Ty ): Speed of the school of fish determined from V _B and V _W Under the above conditions, the speed of the school of fish V _T is calculated using the following formula. It will be done.

V _T = V _B − V _W ...(5) In Figure 2, constant speed navigation is assumed, so the previous measured value and the current measured value are equal. Also, if we consider the point when the averaging process has reached a sufficiently steady state, in the above equation (1),
Since v _Ox = v _Ix , v _Nx = v _Ix, that is, the measured value and the calculated value are equal. Further, the same applies to the above formula (2). From this, V _B and V _W
The calculated value of is equal to the measured value. Therefore, no error occurs in the moving speed V _T of the school of fish calculated using the above equation (5).

[3] Regarding the speed of the ship with respect to the seabed, the speed of the ship with respect to the school of fish, and the moving speed of the school of fish when turning by angle A from constant speed navigation in Figure 3 V _BO (v _BOx , v _BOy ): Based on the previous measurement value Velocity of the ship with respect to the seabed after averaging processing V _BI (v _BIx , v _BIy ): Velocity of the ship with respect to the seafloor measured this time V _BN (v _BNx , v _BNy ): Velocity of the ship with respect to the seabed that has been subjected to averaging processing Velocity of the vessel relative to the seabed V _WO (v _WOx , v _BWy ): Velocity of the vessel relative to the school of fish obtained by averaging the previous measurement values V _WI (v _WIx , v _WIy ): Velocity of the vessel measured this time relative to the school of fish V _WN (v _WNx , v _WNy ): Velocity of the ship relative to the school of fish obtained by averaging the current measured values V _TI (v _TIx , v _TIy ): Movement speed of the school of fish measured this time calculated from V _BI , V _WI V _TN (v _TNx , v _TNy ): The moving speed of the school of fish obtained by averaging the current measurement values obtained from V _BN and V _WN Under the above conditions, the moving speed of the school of fish when using true north as the reference is Assuming that there is no change, and the speed of the ship relative to the seabed in xy coordinates is the same as before, v _BNx = v _BIx = v _BOx , v _BNy = v _BIy =
v _BOy , and the speed of the vessel relative to the school of fish V _WI changes. Also, if the rate of change in the x direction of this velocity v _WI is a, and the rate of change in the y direction is b, then v _WIx = a・v _WOx , v _WIy = b・v _WOy ...(6) (However, a ≠0, b≠0). Therefore, by substituting the above equation (6) into the above equations (1) and (2) to calculate V _WN , it is obtained by the following equation.

v _WNx = a-1 + K/a・K・v _WIx ...(7) v _WNy = b-1+K/b・K・v _WIy ...(8) Therefore, V _TN calculated by the above formula (5) is , from the above equations (7) and (8), the following equation is obtained.

v _TNx = v _BNx −v _WNx = v _BIx = −a−1+K/a・K・v _WIx …(9) v _TNy = v _BNy −v _WNy = v _BIy −b−1+K/a・K・v _WIy ...(10) Also, what is based on the measured value is shown by the following formula.

v _TIx = v _BIx −v _WIx …(11) v _TIy = v _BIy −v _WIy …(12) Therefore, the error ΔV _T (Δv _Tx , Δv _Ty ) is calculated using the above formula.
From (3), (4), (9), (10), (11), and (12), we get the following.

Δv _Tx = v _TIx −v _TNx = (1-1/K) (1-1/a) v _WIx )
...(13) Δv _Ty = v _TIy −v _TNy = (1-1/K) (1-1/b) v _WIy )
...(14) In this way, V _TI and V _TN will be different, resulting in an error as shown in Figure 3.

The present invention was proposed in order to eliminate the problems with the conventional measuring device described above, and its purpose is to use a circuit that does not involve averaging processing in the frequency detection circuit, and to Convert the frequency of the reflected wave from the coordinate system of the beam emission direction to the coordinate system with true north as the reference,
In this system, the moving speed of the school of fish is calculated from the speed of the ship with respect to the seabed and the speed of the ship with respect to the school of fish, and then averaging processing is performed to prevent errors in the moving speed of the school of fish even when the ship is turning. The present invention provides a method for detecting the moving speed of a school of fish.

Next, an embodiment of the method for detecting the moving speed of a school of fish according to the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 4 is a block diagram of a frequency detection circuit implementing the detection method of the present invention. That is, in FIG. 4, 1 is a transmitter that transmits ultrasonic pulses, and 2 is a transmitter that transmits ultrasonic pulses.
is a transmission/reception switching circuit, 3 is an ultrasonic transducer, 4 is a transmitter, 5 is a frequency divider, 6 is an oscillator that oscillates at a frequency sufficiently higher than the transmission frequency, 7 is an AND gate,
8 is a counter, and 9 is a calculator.

In the circuit configured in this way, the transmitter 1
The pulses generated are supplied to the ultrasonic transducer 3 via the transmission/reception switching circuit 2. The transducer 3 emits ultrasonic pulses diagonally upward underwater, receives the reflected waves, converts them into electrical signals, and supplies the electrical signals to the transmitter 4 . In this way, the signal transmitted by the transmitter 4 is amplified and divided by the frequency divider 5. This frequency divided signal is applied to the AND gate 7 only during its high level period.
is turned on, and the oscillation frequency of the oscillator 6 is counted by the counter 8. And this counter 8
The oscillation frequency of the oscillator 6 counted by is supplied to the calculator 9. The count value obtained in this way gives the period of the reflected wave and is converted into the ship speed. Moreover, the Doppler frequency detected in this way is a measured value itself without averaging processing.

Next, a detection method in which the moving speed of the school of fish is calculated by coordinate transformation based on the measured values and subjected to averaging processing will be explained with reference to the conceptual diagrams shown in FIGS. 5 to 7. In addition, in FIGS. 5 to 7, y
indicates the bow direction, x indicates the starboard direction, and the xy coordinates are composed of the front, rear, left and right of the ship. Also, Y is due north,
X indicates the east direction, and north, south, east, and west constitute the XY coordinates. Furthermore, V〓 denotes the velocity vector, and V〓 _x is x
The direction component, V〓 _{y ,} represents the component _in the y _direction , _v〓 In this case, α
represents B, W, and T.

FIG. 5 shows the state of coordinate transformation from xy coordinates to XY coordinates. FIG. 6 shows a case where the speed of the ship with respect to the seabed and the speed of the ship with respect to the school of fish during constant speed navigation are subjected to coordinate transformation to calculate the moving speed of the school of fish. Figure 7 shows the angle C from constant speed navigation.
A case is shown in which the speed of the ship with respect to the seabed and the speed of the ship with respect to the school of fish are converted into coordinates when the ship turns by a certain amount, and the moving speed of the school of fish is calculated.

[ ₁ ] Concerning coordinate conversion from _xy coordinates to If coordinate transformation is performed so that V is expressed by components v _x and v _y with V as the true north Y direction, it is expressed by the following equation.

_{v _ _ _ _ _} Regarding the speed of the ship with respect to the seabed, the speed of the ship with respect to the school of fish, and the moving speed of the school of fish when sailing at high speed (Figure 6) V _B (v _Bx , v _By ): The speed of the ship with respect to the sea bed measured this time V _W (v _Wx , v _Wy ): Speed of the ship measured this time relative to the school of fish V _T (v _Tx , v _Ty ): Moving speed of the school of fish determined by XY coordinates based on V _B and V _W B: Angle between true north and bow of the ship The above conditions When V _B and V _W are converted into XY coordinates and expressed, the following equation is obtained from equations (15) and (16) above.

v _BX ＝v _Bx・cos(B)−v _By・sin(B) ……(17) v _BY ＝v _By・cos(B)＋v _Bx・sin(B) ……(18) v _WX ＝v _Wx・cos(B)−v _Wy・sin(B) ……(19) v _WY =v _Wy・cos(B)＋v _Wx・sin(B) ……(20) Therefore, the moving speed of the school of fish V _T is It is determined by the following formula based on the above formula (5).

v _X = v _BX −v _WX = (v _Bx −v _Wx ) cos(B) − (v _By −V _Wy ) sin(B)
...(21) v _Y = v _BY −v _WY = (v _By −v _Wy ) cos(B) + (v _Bx −V _Wx ) sin(B)
...(22) In this case, since V _B and V _W are the measured values themselves, no error occurs in V _T.

[3] Regarding the speed of the ship with respect to the seabed, the speed of the ship with respect to the school of fish, and the moving speed of the school of fish when turning by angle A from constant speed navigation (Figure 7) V _B1 (v _B1x , v _B1y ): Vessel measured this time V _W1 (v _W1x , v _W1y ): Velocity of the ship with respect to the fish school measured this time V _T1 (v _T1x , v _T1y ): Moving speed of the fish school determined in XY coordinates based on V _BI , V _WI C: Angle between true north and the bow Under the above conditions, V _B1 and V _W1 are converted to XY coordinates in exactly the same way as shown in Figure 6 [see formulas (17) to (20)], and the movement of the school of fish is calculated. The velocity V _T1 is found [see equations (21) and (22)]. Moreover,
Since V _B1 and V _W1 are the measured values themselves, the moving speed V _T1 of the school of fish gives the true value.

In the above explanation, it is assumed that the measured value and the true value are equal, but since the measured value generally has an error from the true value, it is averaged to the moving speed of the fish school V _T1 calculated by the method described above. By performing this processing, it is possible to stably display the moving speed of a school of fish without errors when turning.

As is clear from the embodiments described above, according to the method for detecting the moving speed of a school of fish according to the present invention, the moving speed of a school of fish can be displayed stably without error even when the ship is turning, and it is possible to track a school of fish properly. becomes.

[Brief explanation of the drawing]

1 to 3 are conceptual diagrams showing a conventional detection method for calculating the moving speed of a school of fish, FIG. 4 is a block diagram of a frequency detection circuit implementing the method of detecting the moving speed of a school of fish according to the present invention, and FIG. 7 to 7 are conceptual diagrams showing the detection method of the present invention. 1... Transmitter, 2... Transmission/reception switching circuit, 3... Transmitter/receiver, 4... Receiver, 5... Frequency divider, 6... Oscillator, 7... AND gate, 8... Counter, 9
...Calculator.

Claims (1)

[Claims] 1. An ultrasonic signal is emitted into the water diagonally downward from the bow and stern line and a direction perpendicular to it, and the frequency of the reflected waves reflected from the seabed and the frequency of the reflected waves reflected from the school of fish are determined. A device that measures the moving speed of a school of fish detects the frequency of the reflected waves reflected from the seabed and the school of fish, and from these frequencies, a frequency detection circuit calculates the speed of the ship relative to the seabed and the school of fish, and calculates the bow and stern line. The speed expressed in the reference coordinate system is converted to a coordinate system with true north as the reference, and the moving speed of the fish school is calculated from the speed of the ship with respect to the seabed and the speed of the ship with respect to the school of fish in this coordinate system. A method for detecting the moving speed of a school of fish, characterized in that the moving speed of the school of fish is detected without error when a ship turns by performing averaging processing on the moving speed of the school of fish. 2. In the method for detecting the moving speed of a school of fish according to claim 1, the frequency detection circuit divides the frequency signal of a reflected wave reflected from the seabed and the school of fish, and detects a high level of the divided output. A method for detecting the moving speed of a school of fish, which comprises counting an oscillation frequency higher than that of an ultrasonic signal emitted into the water, and converting this count value as the period of the reflected wave to the speed of the ship relative to the seabed and the school of fish.