JPH011994A - Wave direction measurement method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of measuring wave direction using ultrasonic waves.

[Conventional technology]

An example of the conventional method of measuring wave direction using ultrasonic waves is shown in Part 3.
This will be explained with a diagram. As shown in the plan view in Figure 3 (al.
Ultrasonic transducer A at an appropriate location on the seabed.

B and C are arranged to form a triangle, and ultrasonic waves are transmitted directly above each. Let the angle of vertex A be α, and let the lengths of each side be (a, b, c) as shown in the figure.

For convenience of explanation, it is assumed that the points A, B, and C transmit waves at the same time.

Now, suppose that a wave W parallel to a line at an angle θ with respect to side CA comes as shown in the figure. The traveling direction (wave direction) of the wave is a direction perpendicular to the line of the wave W, that is, (90° - 0) with respect to the side CA.

At this time, as shown in Figure 3, the time from the time Tc when the wave W passes through the 0 point to the time T^ when it passes through the A point is t.
>, t is the time from TA to time point T when the same wave passes point B, and the distance between CA and AB, measured along the traveling direction of wave W, is 1) and 4. When the traveling speed of the wave W is V, J, I! b sin θ−v t ,
+1)1t, =c sin (α-θ)-vt,
(2) From this, c 5in (α-θ) tm From equation (3), θ can be found as follows.

sin"θ (b/c)" + 2(tb/tll)(b/c)
cos α+ (tb/tJ ``Three ultrasonic transceivers A, B, and C each perform the same operation as a wave height meter, and one wave passes through the point directly above each of the ultrasonic receivers A, B, and C. The travel time t□t1 of this wave is determined by capturing the time point and using the difference between the time points.

In equation (4), everything except "b" and "@" are constants, so if you put tb+"m obtained above into equation (4) and calculate θ, you can obtain the wave direction (90° - θ). .

[Problem that the invention seeks to solve]

However, in this conventional method, an ultrasonic transducer requires 3 cents, and it is difficult to accurately obtain the horizontal and vertical positions of three sets of ultrasonic transducers on the seabed. Although it is possible to do this at a depth of about 50 meters, it becomes extremely difficult to do so at a depth of about 50 meters.

As described above, there is a problem in that the three-dimensional relative positions of the three sets tend to include large errors, and the reliability of the wave direction measurement results is significantly impaired.

The present invention solves the problems of the conventional methods as described above, and can measure wave direction with high reliability even when installed at the bottom of a large body of water, regardless of the accuracy of identifying the installation position of the ultrasonic transducer. The object of the present invention is to provide a wave direction measurement method that can perform the following steps.

[Means for solving problems]

The present invention uses an ultrasonic transducer held at a predetermined position below the water surface to transmit ultrasonic waves substantially upward in at least three directions separated by angles from each other over time. This wave direction measuring method is characterized in that the wave direction is determined based on the reception time difference of the reception signals of the same wave in the three directions.

[For production]

According to the present invention, one set of ultrasonic transceivers is placed at one suitable location on the bottom or below the water surface, and ultrasonic waves are transmitted from that one location in three directions upward, so that the transmitting source position is And the wave reception positions are always the same among the three beams, and even when the installation position is deep and it is difficult to identify the position itself, the relative position of the three beam transmission and reception points is always the same. There is no error in the data, and reliable data can be obtained.

The three ultrasonic wave transmission directions may be different directions, and may be within the - plane.

〔Example〕

An embodiment of the present invention will be described using an open view.

In FIG. 1, l indicates the sea surface and 2 indicates the seabed.

3 shows an ultrasonic transceiver device placed at one point on the seabed 2. The ultrasonic transceiver device 3 has an ultrasonic device that transmits ultrasonic waves in three different directions to measure wave heights. A single unit with three sets of transducers is supported by a gimbal structure so that the reference plane is always horizontal and the vertical axis perpendicular to the reference plane is always vertical. In the figure, 4 indicates the vertical axis when the ultrasonic transceiver 3 having such a structure is installed on the seabed, and the vertical axis is 5°6.
7 shows ultrasound beams sent out in three transmission directions. The intersection points of the ultrasonic beam 5.6.7 and the calm sea surface 1 are A, B, and C, forming a triangle. Let O be the intersection of the vertical axis 4 and the sea surface 1.

W is a wave, which travels along a line of travel 9 perpendicular to its ridgeline 8, passes through these points in the order of C, A, and B, and the wave height of the wave passed by the ultrasonic beam 7.5.6 is It is detected over time and the waveform is sensed.

The point at which the wave height reaches its maximum value is the point at which the wave passes, so find the point at which the wave passes for each of the ultrasonic beams 7.5.6, and use the time difference to find the wave direction using the same calculation as above. Can be done.

At this time, the three ultrasonic beams 5, 6, and 7 are transmitted with a time difference in order to avoid mutual interference. is approximately 80as. If we consider the second echo, the interval between the transmission points of each ultrasound beam is 1
The measurement time using three ultrasonic beams is approximately 32 seconds from the first delivery to the last reception.
There is a deviation of 0m5. However, for a wave with a period of about 10 seconds, this time lag is about 3.2%, which is sufficiently short, and the error is small.

Furthermore, since the wave height is detected using an ultrasonic beam tilted with respect to the vertical, an error occurs accordingly. for example,
When the angle at around 1 is 19.1°, compared to the vertical wave height, 1/cos 19.1° = 1.058,
A value that is approximately 5.8% higher is detected, but this measurement method does not care about the absolute value of the wave height, but rather detects the point at which the wave height reaches its maximum value. Errors don't matter.

However, this inclination causes a detection error in the horizontal direction of the wave crest. In other words, the second
In the figure, the passage of a wave is detected at an apex 10, for example by means of an ultrasound beam 6.

Detection of the passage of the wave by the ultrasonic beam 5 is as follows: Since the ultrasonic beam 5 is perpendicular to the projection plane in Fig. 2, the time difference between the passing points of the wave by the two beams 5.6 is ta+, and it is measured with the perpendicular beam. The time difference t with respect to the wave peak 1) involved an error of Δt1. Immediately, ta - ta + - ΔL, +51 this error Δt
is expressed as ΔL,=kHtan φ, where φ is the inclination angle of the ultrasonic beam 6 with respect to the vertical axis on this projection plane, H is half the height of the wave height, and k is a proportionality constant. This wave height H is expressed by H = H, cosφ with respect to the apparent wave height H8, so Δ is expressed as = kH, tanφcosφ (6), and the inclination angle φ is projected onto a plane perpendicular to the direction of the wave. Since it is the inclination angle of the ultrasonic beam, it is a function of θ, which indicates the wave direction. That is, φ=f(θ) (7) Formula f61 for correcting the wave travel time difference. (51 and equation (7).

(4) is combined to calculate the wave direction (90°-θ).

A minimum of three ultrasonic beams are required.

If 4 or more beams are used and data with a large time difference is selected, the error will be reduced.

〔Effect of the invention〕

According to the present invention, the ultrasonic wave transmission point and delivery point always coincide with each other for a plurality of beams, so there is no error caused by measurement errors in the relative positions of the wave transmission and reception points.
Moreover, it is not affected by measurement errors in the absolute position of the installation point itself, the structure of the measuring instrument is simple, the measurement work is easy, and it is possible to use an extremely reliable wave direction measurement method even in deep water locations. can be provided, and has extremely great practical effects.

[Brief explanation of drawings]

Fig. 1 is a perspective view illustrating an example of implementing the method of the present invention, Fig. 2 is a projection view thereof projected onto a vertical plane in the wave direction, and Fig. 3 (al indicates a conventional measurement method). (bl is a graph showing the response of the receiver at each point A, B, and C. ■... Sea surface, 2... Seabed, 3... Ultrasonic transducer , 4... Vertical axis, 5, 6.7... Mi'fl wave beam, 8... Ridge line, 9... Progress line, 10.1)...
·vertex.

Claims (1)

[Claims] (1) Using an ultrasonic transducer held at a predetermined position below the water surface, the wave height is measured over time using ultrasonic waves transmitted almost upward in at least three directions separated by angles from each other. A wave direction measuring method characterized in that the wave direction is determined based on the reception time difference of the reception signals of the same wave in the three directions.