JP2916362B2 - Apparatus and method for correcting sound velocity in position measurement - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound velocity compensator for position measurement, and more particularly to an SBL (Short Base-Line System).
m) A sound velocity correction device and method capable of performing sound velocity correction in water (including seawater) in position measurement using a method.

[0002]

2. Description of the Related Art Conventionally, as a device relating to this kind of sound velocity correcting device, for example, those shown in FIGS. 1 and 3 are known.

A measuring object 1 is mounted on the bottom of a measuring ship S shown in FIG. 1, and a signal processing arithmetic unit 2 mounted on the measuring object 1 is connected to an underwater moving object 4 via a signal transmission cable 3. It is connected. A transmission signal or a transmission trigger pulse signal is transmitted from the signal processing arithmetic unit 2 via the signal transmission cable 3 to the transmitter 5 attached to the underwater moving object 4. The transmitter 5 transmits an ultrasonic signal having a predetermined frequency. This ultrasonic signal is applied to the measurement object 1
Received by the wave receiver 7 attached (7 _1, 7 _2, 7 _3). The received signals received by the receivers 7 (7 ₁ , 7 ₂ , 7 ₃ ) are processed by the signal processing and arithmetic unit 2, where the transmitter 5 and the receivers 7 ₁ and 7 ₁ ,. 7 _2, 7 ₃ obtains distances between the between the receivers of calculating the three-dimensional position of the transmitting device 5. That is, the time from transmission to reception is measured,
It is converted into distance by the propagation speed of underwater sound.

Although the distance can be obtained by the above-described processing, sound velocity correction is conventionally performed when this distance is obtained. When performing this sound velocity correction, the water temperature sensor 1
One (0) (10a, 10b, 10c, 10d, 10e) is attached to the measurement object 1, the transmission signal cable 3, the underwater moving object 4, or the like, and the signal from the water temperature sensor 10 is calculated by the signal processing calculation device 2. The water temperature is read by the processing.

[0005]

However, when performing the sound velocity correction based on the water temperature, various known methods are used. However, depending on which of these methods is used, the same water temperature may be used. The disadvantage is that a difference of about 20 m to 50 m results. The speed of sound is the density of water,
There is a drawback that accurate distance cannot be calculated by the sound velocity correction as described above because the distance greatly changes depending on the water pressure.

Accordingly, the present invention has been made in view of the above-mentioned drawbacks of the prior art, and provides a sound velocity correction apparatus and method capable of accurately performing sound velocity correction by actual measurement and improving accuracy in position measurement. It is intended to be.

[0007]

SUMMARY OF THE INVENTION The present invention provides a measuring object having at least one or more receivers and a transmitter capable of receiving an ultrasonic signal, and an ultrasonic signal received by the measuring object. A signal processing arithmetic device for performing arithmetic processing, and an underwater moving object connected to the signal processing arithmetic device via a signal transmission cable and having a transmitter and a receiver. The sound speed between a specific point with the wave device and the sound speed between the specific point of the receiver and the transmitter of the underwater moving object are respectively obtained, and the signal processing arithmetic device is used by using the obtained sound speed. By calculating the corrected sound speed, the distance between the measurement object and the underwater moving object can be obtained. The present invention also determines the sound speed between a specific point between the receiver and the transmitter of the measurement object and the sound speed between the specific point of the receiver and the transmitter of the underwater moving object, respectively. The distance between the measurement object and the underwater moving object can be obtained by calculating the sound speed corrected by the signal processing operation device using the obtained sound speed.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a sound velocity correcting device for position measurement according to the present invention will be described with reference to FIG. Note that the same reference numerals are used for those having substantially the same function and configuration as those of the conventional device.

In the case of seawater shown in FIG. 1, the temperature decreases as the depth increases, except in special cases, and is never uniform.
Also, the density changes. Therefore, in the present invention, the actual sound speed is measured near the sea surface where the measuring ship S is located and at the depth where the underwater moving object is located to improve the positional accuracy.

As shown in FIG. 2, in addition to the conventional configuration shown in FIG. 3, a receiver 6 for sound velocity correction is attached to an underwater moving object 4. The receiver 6 is arranged at a distance L ₀ arbitrarily set in advance from the transmitter 5, and a transmitter 8 for sound velocity correction is provided on the lower surface of the measurement object 1 attached to the bottom of the measurement ship S. Installed. The transmitter 8 and the receiver 7
Between the 7 ₁ between the L _1, 7 ₂ between the L _2, 7 ₃ between the L ₃
Are placed at a distance of This distance is arbitrarily set in advance.

In the sound velocity compensating apparatus having the above-described structure, the signal processing arithmetic unit 2 transmits the transmission signal via the signal transmission cable 3 to the transmitter 5 attached to the underwater moving object 4 similarly to the operation of the SBL system shown in FIG. Alternatively, a transmission trigger pulse signal is transmitted. The transmitter 5 transmits an ultrasonic signal having a predetermined frequency. The ultrasonic signal measurement object 1 wave receiver 7 attached to (7 _1, 7 _2, 7 ₃₎ receives any receivers 6 attached to the underwater vehicle body 4 simultaneously receives at.
Therefore, the signal processing operation device 2 also measures the time from the transmitter 5 to the receiver 7 and the time from the transmitter 5 to the receiver 6. Assuming that this time is t ₀ , the underwater moving object 4
Acoustic velocity v of the position depth ₀ can be expressed by the following equation (1). That is, v ₀ = L ₀ / t ₀ (1)

Next, near the sea surface shown in FIG.
From transmitting toward the wave receiver 7 ultrasound signals from the transmitters 8 as well as to transmit ultrasound signals (7 _1, 7 _2, 7 _3). The received signals received by the receivers 7 (7 ₁ , 7 ₂ , 7 ₃ ) are converted by the signal processing arithmetic unit 2 into the respective receivers 7 ₁ , 7 ₂ ,
Measuring the time for receiving 7 _3. Assuming that the time corresponding to L ₁ is t ₁ , the time corresponding to L ₂ is t ₂ , and the time corresponding to L ₃ is t ₃ , the sound velocity v ₁ near the sea surface is given by the following equation (2).
Can be represented by That is, v ₁ = １ ／ (L ₁ / t ₁ + L ₂ / t ₂ + L ₃ / t ₃ ) (2)

The operation for obtaining v ₁ is different from the operation for obtaining v ₀ described above, and may be performed between operations of the conventional SBL system. That is, when to perform a series of operations for calculating the position by receiving approximately every one second wave receiver 7 ultrasound signals transmitted (7 _1, 7 _2, 7 ₃₎ from the wave transmitter 5, the v ₁
It is enough to perform once in about 10 seconds.

The ultrasonic wave transmitted by the transmitter 5 measures the time of reception by the receiver 7 (7 ₁ , 7 ₂ , 7 ₃ ) according to the SBL method, and is determined by the above equation (1). ₀ and v ₁ obtained by the above equation (2) are obtained. Therefore, from these data, the sound velocity V can be expressed by the equation (3). That is, V = １ ／ (v ₀ + v ₁ ) (3) That is, the acoustic velocity v ₀ in water moving object 4, attempts to accurately calculate the distance between the water moving object 4 by determining the average sound velocity V and the measured object 1 from the sound velocity v ₁ Tokyo in the measurement object 1 It is assumed that.

[0015] In the present invention, the wave receiver 7 transmitters 8 for sound velocity correction (7 _1, 7 _2, 7 ₃₎ are provided separately from the, wave receiver (7 _1, 7 _2, Any one of 7 ₃ ) may have a transmission function. Further, in the present invention, the receiver 7 is constituted by _three of 7 ₁ , 7 ₂ , and 7 ₃ , but the present invention is not limited to this, and it goes without saying that a plurality of receivers may be provided.

In the present invention, the sound velocity V is calculated by the equation (3). The sound velocity V at each position is obtained and averaged while moving the underwater moving object 4 while varying the depth. Thus, a more accurate sound speed may be obtained. Further, the present invention has been described on the assumption that it is used in water (including seawater). However, it is needless to say that it can be used not only in water but also in other liquids as long as ultrasonic waves are transmitted. is there.

[0017]

As described above, according to the present invention,
Since the sound velocity can be obtained from the actually measured value, elements such as density and pressure are also included, so that there is an effect that an accurate sound velocity is obtained and the positional accuracy is improved. Further, according to the present invention, it is not necessary to use a water thermometer, so that the circuit of the signal processing operation device can be simplified and the device can have a simple configuration.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a measurement method of an SBL method according to the present invention.

FIG. 2 is a diagram showing a configuration of a sound velocity correction device according to the present invention.

FIG. 3 is a diagram showing a configuration of a conventional sound speed correction device.

[Explanation of symbols]

1 measured object 2 signal processing operation apparatus 3 signal transmission cable 4 underwater moving objects 5 wave transmitter 6 wave receiver 7 (7 _1, 7 _2, 7 ₃₎ receivers 8 transmitters

Claims (3)

(57) [Claims] 1. A measurement object including at least one or more receivers and a transmitter capable of receiving an ultrasonic signal, and a signal processing operation device for performing arithmetic processing on an ultrasonic signal received by the measurement object. Comprising an underwater moving object having a transmitter and a receiver connected from the signal processing operation device via a signal transmission cable, between a specific point of the receiver and the transmitter of the measurement object. Sound speed between the specific point of the receiver and the transmitter of the underwater moving object, respectively, and using the obtained sound speed to calculate the sound speed corrected by the signal processing arithmetic device Wherein the distance between the measurement object and the underwater moving object can be obtained. 2. The sound velocity compensator according to claim 1, wherein one of the receivers of the measurement object further includes a transmitter. 3. The sound velocity between a specific point between the receiver and the transmitter of the measurement object and the sound velocity between the specific point of the receiver and the transmitter of the underwater moving object are respectively obtained. Calculating the sound speed corrected by the signal processing operation device using the obtained sound speed, whereby the distance between the measurement object and the underwater moving object can be obtained. Method.