JPH0565014B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a water temperature measuring method for remotely measuring water temperature at a given depth underwater using the propagation time of sound waves.

(Prior Art) Several technologies have been proposed for remotely measuring water temperature at arbitrary depths using ultrasonic waves, as described below.

JP 60-50296 JP 58-27034 JP 58-184520 JP 58-184521 JP 58-184522 JP 58-184523 JP 60-46435 Related devices When explained with reference to Fig. 3, A,
A transducer is installed at point C, the time required for the sound wave to propagate the distance ABC is measured, and the speed of sound is calculated backwards from this to calculate the water temperature.

(Problem to be solved by the invention) However, since the water temperature varies depending on the depth and the speed of sound also changes, according to Snell's law (Page 60 of the Ultrasonic Technology Handbook, revised edition), sound waves are refracted and, for example,
AB′C will be propagated. That is, the measured propagation time includes a refraction path component in addition to the temperature component, and the calculated water temperature value includes an error because the component due to the position of B' is not corrected.

In particular, since the invention described in the patent publication among the above-mentioned publicly known materials is a method that focuses on the difference in sound wave propagation time between tilt angles θ and dθ, a more precise value of the propagation path difference is required. Considering this, the above-mentioned error appears as a big problem.

(Means for Solving the Problems) The present invention focuses on the fact that the propagation path of sound waves (hereinafter referred to as sound rays) becomes circular within a depth range where water temperature changes are constant, and the temperature change is assumed to be constant. The depth range to be detected is set sequentially from the sea surface to 1st layer, 2nd layer, etc., and a transmitter and a receiver are installed, and 1st layer and 2nd layer are set sequentially for each wave transmission.
The propagation time is measured sequentially from layer to layer.The first time is to identify the sound ray in the first layer from the propagation time and the transmission direction, and the second time is to measure the sound ray in the first layer from the propagation time - the previous sound ray analysis of the first layer. 2 from the propagation time of one layer) and the transmission direction
The sound ray is identified by calculating the propagation time within the layer, and is repeated sequentially through the 3rd layer, etc., and on the ith time, (propagation time - calculated propagation time of the 1st layer +... + calculated i - the calculated propagation time of the 1st layer). We calculated the propagation time in the i layer from the propagation time (propagation time) and the wave transmission direction to identify the sound rays, and then approximated the water temperature linear equation for each layer from these i sound rays and water temperature sensors installed at specific depths. This is what we provide.

(Function) In the range where water temperature change is constant, the sound ray is x ² + y ² = (Cs/g) ² = R ² , where x is the horizontal distance, Cs is Snell's constant, y is the vertical distance, and g is the water temperature gradient. Draw a circle (Ultrasonic Technology Handbook, New Edition No. 61-62)
page).

Therefore, cases in which g is positive and negative will be explained below.

(1) When g>0 Figure 4 explains the working principle of the present invention.
In the figure, it is assumed that a transmitter is installed at point A and a receiver is installed at point C. Also, S ₁ indicates the first sound ray, that is, the sound ray in the first layer, and S ₂ indicates the second sound ray.
This shows the sound rays up to the second layer, that is, the second layer.

In addition, each position and numerical value shall be expressed as shown in the figure.

The sound speed function is v=k+ay......(1) However, assuming that k is the sound speed at y=0 and a is a proportionality constant, the first wave transmission to the first layer is x ² + (y+R) ² =R along the circle of ² . Thereby, the sound ray S ₁ is expressed with the position of y=0 as a reference.

At this time, the coordinates of point A and point C are A(Rl sinθ ₁ , -R+R cosθ ₁ ) C(l ₁ +R sinθ ₁ , -R+R cosθ ₁ ) Also, the coordinates of point _B is that the sound ray draws a circle. Therefore, B ₁ (l ₁ +R sinθ ₁ −R+√ ² −( ₁ +
₁ ) ^2On the other hand, if the passage angle of the sound ray passing through point _B1 is _θ2 , the coordinates of point _B1 can also be expressed as _B1 (R _sinθ2 , -R+R cosθ2 ₎ .

Also, since the coordinates of _one point B are the same, comparing their x coordinates, sinθ ₂ = l ₁ /R + sinθ ₁ ...... (2) From Snell's law, v ₀ / cosθ = v ₁ / cosθ ₁ = v ₂ / cosθ ₂ ......(3) However, v ₀ is the sound speed of y=0 v ₁ is the sound speed of point A (top of the first layer) v ₂ is the sound speed of the top of the second layer. Therefore, equations (1), (3) and From the y coordinate of point A, k=v ₀ = v ₁ /cosθ ₁ =k+a(-R+R cosθ ₁ )/co
sθ ₁ ...(4) holds true. Note that k is known because v ₁ is calculated by a water temperature sensor (not shown) provided at that depth position based on the unique relationship between water temperature and sound speed.

Arranging the left side = right side of equation (4), R=k/a......(5) Next, find the time required for the sound wave to propagate through AB ₁ C.

If the propagation time of AB ₁ is t ₁ , then t ₁ =∫〓 ² 〓 ₁ Rdθ/v=∫〓 ₂ 〓 ₁ R/k cosθdθ Here, using equation (5), t ₁ =∫〓 ₂ 〓 ₁ dθ /a cosθ=1/a[log|tan(θ
/2+π/4)｜]〓 ₂ 〓 ₁ = 1/a log｜tan(θ ₂ /
2+π/4)/tan(θ ₁ /2+π/4) | B ₁ The propagation time t ₂ of C is t ₂ =−R+R cosθ ₁ −R+cosθ ₂ dy/v=∫−R+R cosθ ₁ −R+R cosθ ₂ dy/k+ay =1/alog | k+a (-R+R cosθ ₁ )/k+a
(−R+R cosθ ₂ ) |=1/alog | cosθ ₁ /cosθ ₂
| (∵k=aR) ∴t=t ₁ +t ₂ = 1/alog | 1−sinθ ₁ /1−sinθ| ………(6) By substituting equations (2) and (5), sinθ ₂ = a/kl ₁ + sin θ ₁ ......(7) By the way, since k, θ ₁ and l ₁ are known, when the propagation time t is measured, a and θ are obtained from equations (6) and (7). Find ₂ . That is, the sound speed function can be determined. Therefore, the water temperature for any depth y within one layer can be calculated from the unique relationship between the speed of sound and the water temperature.
This unique relationship is v=1458.64+3.18T
(T is the water temperature) is known.

Next, the case of sound speed S ₂ will be similarly analyzed.

In this case, the sound waves are transmitted at an angle of θ' ₁ = tan ^-1 CD ₂ /l ₁ = tan ^-1 2d/l ₁ (8). If the passing angle of _one point B' is θ' ₂ , the y-coordinate of _one point B' can be considered as in the above case, so it can be expressed as -R+R cos θ' ₁ -d or -R+R cos θ' ₂ . Therefore, if we organize this, θ' ₂ = cos ^-1 (cos θ' ₁ - d/R) ......(9) Also, the change in x coordinate between AB' ₁ is l ₁ - _{l 2} = R (sin θ′ ₂ −sin θ′ ₁ )……(10) l ₂ can be found from equations (9) and (10). This is because θ' ₁ is known from equation (8).

Then, the sound wave is vertically d between AB′ ₁ and from point B′ ₁ .
Letting t' be the time required to propagate upward, that is, to propagate within one layer, t=1/alog | 1-sinθ' ₁ /1-sinθ' ₂ |...
...(11) Here, since θ′ ₁ and θ′ ₂ are known from the above equations (8) and (9), t′ can be found from this.

Now, the propagation time t'' between B' ₁ B' ₂ D ₁ can be determined as follows.

Note that in the case of two layers, the proportionality constant a is different from the above-mentioned a, so the radius R of the sound ray and further k also inevitably change. Therefore, each of these values in the two layers is a′, R′,
Replace it with k′. Between these values, using Snell's law, R′=k′/a′ ………(12) also holds, and from k′=v′ ₀ =v ₁ /cosθ′, k′ is found. This is because v ₁ and θ′ ₁ are known.

By the way, in the second layer, the aforementioned θ ₁ is changed to θ′ ₂ , and θ ₂
can be considered by replacing θ' ₃ with l ₁ and l ₂ . That is, considering equations (6) and (12), t″1/a′log | 1−sinθ′ ₂ /1−sinθ′ ₃ |……
…(13) Also, from equations (7) and (12), sinθ′ ₃ = a′/k′l ₂ + sinθ′ ₂ ………(14) Here, t″ is t−t′ (however, t is the 2
θ′ ₁ and θ′ ₂ are as follows from equations (8) and (9):
Considering l ₂ from equation (10) and k′ in the same way as equation (3),
Since it is known from k′=v′ ₀ =v ₁ /cosθ′ ₁ , the above
From equations (13) and (14), a′ and θ′ ₃ can be found.

In other words, the sound speed function v=k′+a′y in the two layers
can be determined. Therefore, the water temperature for any depth y in the second layer can be calculated in the same way as in the case of the first layer. This is because the water temperature gradient g is determined from the sound velocity function v, and the water temperature at the lower end of the layer, that is, at the boundary with the upper end of the second layer, is determined in advance by the first process.

To summarize below, in the second time, the propagation time in the first layer can be calculated from each data obtained in the first time, and the propagation time in the second layer can be calculated from the actual measurement time. It is found by subtracting. That is, the sound ray within the two layers is specified from the calculated propagation time, the sound wave passage angle at the boundary, and the passage position, the sound speed function is determined, and the water temperature within the second layer is calculated from the boundary water temperature. Ru.

This relationship holds true the third time, the fourth time, etc.

Generally, at the i-th time, 1/a _i log | 1-sinθ _ii /1-sinθ _i,i+1 |=t _i −
_i-1 〓 〓 ^j=1 1/a _j log｜1−sinθ _ij /1−sinθ _i,j+1 ｜………(
15) sinθ _i,i+1 =a _i /k _i l _i-1 +sinθ _ii ………(16) k _i =v _i0 =v ₁ /cosθ _il …(17), k _i , a _i and θ _i,i+1 is found.

However, the respective numerical values and constants are as shown in Figure 5. t _i ...... First measurement time a _i , a _j ...... Proportionality constant k _i of layer i and j layer ...... Value l _i in layer _-1 ......Illustrated horizontal distance θ _ij of the top end of the i layer...This is the passing angle of the j layer at the i-th time.

(2) When g<0 In this case, the sound ray passes on the line x ² + (y-R) ² = R ² as shown in Figure 6. Also, let the sound speed function be v=k-ay.

Now, thinking in the same way as above, A(-R sinθ ₁ , R-R cosθ ₁ ) C(l-R sinθ ₁ , R-R cosθ ₁ ) B(l-R sinθ ₁ , R-√ ² −(- ₁
) ² ) Also, B(-R sinθ ₂ , R-R cosθ ₂ ) ∴θ ₂ =-l/R+sinθ ₁ =-a/kl+cosθ ₁ …………(18) (∵R=k/a) Between AB The propagation time t ₁ is t ₁ =∫〓 ₁ 〓 ₂ Rdθ/v=1/alog｜tan(θ ₁ /2+π
/4)/tan(θ ₂ /2+π/4) | The propagation time t ₂ between BC is t ₂ =∫R−Rcosθ ₂ t ₂ =∫R−Rcosθ ₂ R−Rcosθ ₁ dy/k−ay=1/ alog｜cosθ ₂ B／cosθ ₁
| (∵k=aR) ∴t=t ₁ + t ₂ = 1/a _i log | 1−cosθ ₂ /1−cosθ ₁ | ………(19) Therefore, thinking in the same way as above, (18), A can be found from equation (19). Also, from the second time onwards, the passing angle can be calculated from equation (18).

From the above, at the i-th time, 1/a _i log|1−cosθ _i,i+1 /1−cosθ _ii |=t _i − _i-1 〓 ^j=1 log|1−cosθ _i,i+1 / 1−cosθ _ij | …(20) cosθ _i,i+1 =a _i /k _i l _i-1 +cosθ _ii ………(21) From equations (17), k _i , a _i , θ _i,i You can ask for ₊₁ .

(Example) FIG. 1 shows a configuration for implementing the present invention, and FIG. 2 is a waveform diagram.

In the figure, reference numeral 1 denotes a wave transmitter configured to transmit a beam having a narrow pointing width, and the direction of wave transmission is determined mechanically by a tilt changing circuit 2 or electronically by phase control. This tail change is the first
The first time is at θ ₁ , the second time is at θ ₂ , and so on, and so on, so that the sound waves propagate downward in order.

Reference numeral 3 denotes a receiver that receives waves in a so-called pencil beam with a narrow directivity or in a fan shape with a wide directivity in the front and back directions of the drawing, which is directed directly downward and receives the propagating ultrasonic waves from the transmitter 1. It is designed to receive reflected waves, which are volumetric reverberant echoes, generated at the intersection with the wave beam. Note that fan-shaped beams are not limited to the receiving side;
It may be formed on the transmitting side.

4 amplifies and detects the received reflected wave (Fig. 2b)
5 is a pulse shaping circuit that shapes the received echo signal into a pulse shape (see c in the figure). Reference numeral 6 denotes a timer consisting of a counter, etc., which measures the time t from the point in time when the key pulse a is sent out to the point in time when the pulse c is sent in, when the transmission trigger drives the generation circuit 7 and excites the transmitter 1. That is, this time t corresponds to the time from when the ultrasonic wave is transmitted from the transmitter 1 until the reflected wave from the intersection is received by the receiver 3, and is given by the above equation (6).

8 is a set value given in advance, a water temperature value from a water temperature sensor disposed at a predetermined depth within the measurement range (for example, the position of a transmitter), a sequentially changed tail θ, measurement time t, and other data. Originally mentioned above (15),
Calculate equations (16) and (17) or (20) and (21) respectively.
It is the CPU. 9 is a ROM in which programs for processing the above calculation formulas and others are written in advance; 10
is a RAM that temporarily stores values during calculation and other intermediate results.

FIG. 7 shows another embodiment, in which, for example, the beams from the transmitter 1 and the receiver 2 are directed at the same angle so that they intersect in the middle. The propagation time of ABC at this time is twice that of AB.

This propagation time between AB was obtained from the explanation in Figure 4.
The same formula as that for the propagation time t ₁ of AB ₁ is sufficient, and calculation is not required for the propagation time of B ₁ C. With this method, it is possible to increase the AC distance.

In addition, in this example, the wave is transmitted in the tilted direction,
Although the received wave is directed directly downward, it is also possible to reverse the relationship due to the reversibility of sound rays.

Furthermore, since the speed of sound changes not only in relation to water temperature but also in relation to depth, corrections for this should also be considered. However, in the shallow depth range of 0 to several hundred meters, its influence is considerably smaller than that of water temperature.

Furthermore, it is not necessary that the width of each layer is constant as d;
Depending on the area and the general characteristics of depth and temperature
It is also possible to arbitrarily define d ₁ , d ₂ , . . . .

Finally, when implementing the present invention, it is generally considered that transmitters and receivers are placed at the front and rear of the ship's bottom, but if the distance between ships can be maintained and the timing of transmitting waves can be known, Alternatively, one (or both) may be a fixed object.

(Effects of the Invention) As explained above, according to the water temperature measuring method according to the present invention, it is possible to measure the water temperature in a depth range where the water temperature change is considered to be constant with extremely high accuracy, and for each layer, the water temperature can be measured sequentially from the first layer to the lower layer. Since the measurements are repeatedly carried out toward the target temperature, the propagation time based on the actual sound ray can be obtained, which allows more accurate and less error-prone water temperatures to be determined down to the lower layers. Furthermore, since a sound measurement function for depth is used, water temperatures at all depths within the detection range can be determined.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a configuration for implementing the present invention;
FIG. 2 is a waveform diagram. FIG. 3 is a diagram for explaining propagation path errors of sound waves. 4 to 6 are diagrams for explaining the principle of operation of the present invention. 7th
The figure is a diagram showing another configuration for implementing the present invention.

Claims (1)

[Claims] 1. An ultrasonic wave transmitter and an ultrasonic wave receiver are arranged at a fixed distance apart in the horizontal direction, and an ultrasonic signal is transmitted from the ultrasonic wave transmitter to generate reflected waves from underwater. is received by the ultrasonic receiver, the time from transmission to reception is measured, and when the water temperature change rate in the depth direction is constant, based on the measurement time and the transmission direction of the ultrasonic signal. Then, a sound ray path uniquely formed between the ultrasonic transmitter and the underwater reflection point of the reflected wave is specified, and a water temperature corresponding to the sound ray path is determined from the specified sound ray path. A method for measuring water temperature, characterized in that the rate of change is determined, and the water temperature at each depth corresponding to each position on the sound ray path is calculated based on the water temperature change and the water temperature at a specific point given in advance. 2. Transmit an ultrasonic signal from an ultrasonic transmitter provided in a first region where a rate of change in water temperature in the depth direction is given in advance, and determine whether the rate of change in water temperature continues in the first region by transmitting an ultrasonic signal By receiving the reflected waves reflected within the unknown second region and returning to the ultrasonic receiver at a position horizontally different from the ultrasonic transmitter by a certain fixed distance, the process from the above transmission to reception is performed. The time of The passage position and passage direction of the acoustic ray path of the ultrasonic signal transmitted from the transmitter passing through the boundary are calculated, and when the water temperature change rate in the depth direction in the second region is constant, the calculated Based on the boundary water temperature, the passage position and passage direction of the sound ray path passing through the boundary, and the measurement time, the distance from the passage position of the boundary to the reflection point of the ultrasonic signal in the second area is determined. Identify the sound ray path uniquely formed between the sound ray paths, determine the water temperature change rate corresponding to the sound ray path from the identified sound ray path, and calculate the water temperature change rate corresponding to the sound ray path based on the water temperature change rate and the water temperature at the boundary. A method for measuring water temperature, characterized in that the water temperature at each depth corresponding to each position on the sound ray path is calculated.