JPH0526150B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an underwater acoustic positioning device such as a sonar.

Generally, this type of underwater acoustic positioning device uses multiple receivers to receive signals (sound waves) emitted or reflected from a target, and measures the direction of arrival of the received sound waves from the phase difference or time difference between the received signals. do.

FIG. 1 is a diagram showing the principle of measuring the direction of arrival of received sound waves by an underwater acoustic positioning device. Suppose now that a sound wave arrives from a direction forming an angle γ (azimuth angle) with respect to the normal 3 of the line connecting the acoustic centers of the receivers 1 and 2.
At this time, the following relationship holds true.

φ=2π/λd sinγ...(1) λ: Wavelength of sound wave d: Acoustic center distance between receivers 1 and 2 φ: Phase difference between outputs of receivers 1 and 2 Therefore, γ=sin ^-1 (φ/2π/λd) ...(2), and the azimuth angle γ is found from the phase difference φ. Also,
If the speed of sound is c, and if the difference in time when receivers 1 and 2 receive sound waves of the same phase (commonly called time difference) is τ, then τ=d/csinγ, so γ=sin ^-1 (τ・d /c) ...(3) The azimuth angle γ can also be found from the time difference τ. In this way, by measuring the phase difference or time difference in the received signals of a plurality of receivers, the azimuth angle γ of the arriving sound wave can be detected.

FIG. 2 is a block diagram of a conventional method for measuring the azimuth angle γ from the phase difference φ between the received signals of two receivers. The received signals E ₁ and E ₂ are the outputs (effective values) of the wave receiver 12 shown in FIG. 1, respectively.
Now, E ₁ = E ₂ = E _S , and if the signal-to-noise ratio of E ₁ and E ₂ is S/N, then the output E ₀ of the method shown in Figure 2 is
is E ₀ =√2E _S [{1+sinφ+1/(S/N) ² } ^1/2 −{
1+sinφ+1/(S/N) ² } ^1/2 ]...(4) FIG. 3 is a characteristic diagram showing the relationship between the phase difference φ in equation (4) and the output E ₀ using the signal-to-noise ratio S/N as a parameter. As is clear from this figure 3, the worse (smaller) the S/N is, the lower the output E ₀
It is difficult to specify the phase difference φ with respect to the phase difference φ, and therefore the error becomes large. From this, the conventional method shown in FIG. 2 has the disadvantage that the closer the phase difference φ approaches 90°, the larger the error in the azimuth angle γ becomes. Furthermore, since the amount of phase shift of the 90° phase shift circuit used in this method differs depending on the frequency, this also causes a measurement error in the azimuth angle γ.

FIG. 4 is a block diagram of a conventional method for determining the azimuth angle γ from the difference in reception times of four receivers. The delay circuits 21 to 23 are so-called delay lines having delay times τ ₁ to _{τ 3} , respectively. Multipliers 24-26
outputs the products E 1 _to E 3 of the output Ei ₄ of the reference receiver and the time-delayed signals of the outputs E _i1 to _{E i3} of the other receivers, respectively. The maximum value of these outputs E ₁ to _{E 3} is determined, and the azimuth angle γ is calculated from the delay time τ of the delay circuit corresponding to the maximum value using equation (3).
For example, if E ₂ is maximum, the azimuthal angle γ is γ=sin ⁻¹ (τ ₂ c/d). In the method shown in Fig. 4, the angle measurement range is θ _A ,
When the angle measurement resolution is θ _i , the number N of required delay circuits is N=θ _A /θ _i . Therefore, this method generally requires a large number of delay circuits and the same number of multipliers, which inevitably results in a complicated circuit.

An object of the present invention is to provide an underwater acoustic positioning device with good angle measurement accuracy and a simple configuration.

The underwater acoustic positioning device of the present invention includes first and second receivers that respectively convert received sound waves into electrical signals, and a time delay having a length corresponding to the frequency of a delay time control signal. The first value given to the output of the
a second delay circuit that provides a predetermined time delay to the output of the second wave receiver, and a circuit that detects a phase difference between the outputs of the first and second delay circuits; A circuit for integrating sample values of the phase difference detection circuit at predetermined time intervals, and a circuit for generating the delay time control signal having a frequency corresponding to the output of the integration circuit, the first delay circuit, the phase difference detection circuit, A circuit for detecting the phase difference, a circuit for integrating, and a circuit for generating the delay time control signal form a closed loop, and the closed loop is controlled so that the output signal of the circuit for detecting the phase difference becomes zero, and the delay time control signal is controlled. It is configured to detect the arrival direction of the received sound wave from the frequency of the signal.

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 5 is a block diagram of one embodiment of the present invention. The sound waves emitted or reflected from the sonar target are
The received sound waves 101 and 201 are input to the receivers 1 and 2, and the acoustic signals are converted into electrical signals 102 and 202, respectively. The electrical signal 102 is applied to the input of the phase difference detection circuit 35 as the signal 103 via the variable delay time circuit 33, and the electrical signal 202 is applied as the signal 203 via the fixed delay circuit 34, respectively. An output voltage 301 corresponding to the phase difference between the signals 103 and 203 is output from the phase difference detection circuit 35. Output voltage 301 is applied to integration circuit 36. The integrating circuit 36 includes a switch that samples the input signal at regular intervals, and integrates the sampled input signal. The frequency of the voltage variable oscillator 37 is controlled according to the output 302 of the integrating circuit 36. The output of this oscillator 37 is input to the delay time variable circuit 33 as a delay time control signal 303. The delay time variable circuit 33 receives the delay time control signal 3
The delay time is changed according to the frequency of 03. A closed loop consisting of the variable delay time circuit 33, the phase difference detection circuit 35, the integration circuit 36, and the variable voltage oscillator 37 operates so that the output signal 301 of the phase difference detection circuit 35 becomes zero. That is, the phase difference detection circuit 3
If there is no phase difference (or time difference) between the signals 103 and 203 input to the output signal 301, the output signal 301 will be zero. is the integrating circuit 36
As a result, the voltage of the output signal 302 changes, and this voltage change of the output signal 302 changes the frequency of the delay time control signal 303 output by the voltage variable oscillator 37.
This frequency change of 3 changes the delay time τ of the delay time variable circuit 33 in a direction in which the phase difference between the signals 103 and 203 decreases. This change in delay time τ continues until the phase difference between signals 103 and 203 becomes zero. When the phase difference becomes zero, the output signal 301 of the phase difference detection circuit 35 becomes zero, and the integrator circuit 36
The output signal 302 of is held at a constant level, and the frequency f of the delay time control signal 303 output from the voltage controlled oscillator 37 under the control of the output signal 302 is held at a constant frequency and is controlled by this frequency f. The delay time τ of the variable delay time circuit 33 stops changing, and the closed loop is stabilized. The frequency f of the delay time control signal 303 corresponding to the delay time τ is converted into a voltage 304 by the frequency-voltage converter 38.
When the closed loop stabilizes, the voltage 304 also stabilizes,
It becomes a constant voltage. Since the voltage 304 is proportional to the phase difference φ between the received sound waves of the receiver 1 and the receiver 2, the phase difference φ can be easily measured from the voltage 304. The direction of the target is determined by the measured phase difference φ.
It can be measured using (2).

The operations of the integrating circuit 36, variable voltage oscillator 37, variable delay time circuit 33, and phase difference detection circuit 35 will be explained in more detail with reference to FIGS. 6 to 8.

FIG. 6 is a characteristic diagram of the voltage variable oscillator 37.
The input of the voltage variable oscillator 37 is the integral circuit output 30.
2 has been added. The frequency f of the voltage variable oscillator 37 changes in proportion to this voltage V.

FIG. 7 is a characteristic diagram of the variable delay time circuit 33. The delay time variable circuit 33 receives the delay time control signal 3
The delay time can be changed in proportion to the frequency of 03.
Here, τ ₀ is the delay time of the fixed delay circuit 34.

FIG. 8 is an overall characteristic diagram of this embodiment. Now, the phase difference φ between the received sound waves 101 and 102 is zero,
That is, if a sound wave arrives from the front of the receivers 1 and 2, the delay time τ in the delay time variable circuit 33
When becomes τ ₀ , the outputs of the phase difference detection circuit 35 and the integration circuit 36 become zero, and the frequency of the voltage variable oscillator becomes f ₀ . At this time, the closed loop becomes stable. The phase difference φ of the received sound waves can be measured using this frequency f ₀ . Furthermore, when the phase difference changes from a stable state where the phase difference between the received sound waves 101 and 103 is zero and the delay time τ of the variable delay time circuit 33 is τ ₀ to φ _{2 , the phase difference of the phase difference detection circuit 35 changes to φ 2} . Output signal 30
1 is no longer zero, and the output signal 30 is no longer zero.
1 is integrated by the integrating circuit 36 and its output signal 30
2 becomes _VH . The output voltage V _H of this integrating circuit 36
Therefore, the frequency of the output signal of the voltage variable oscillator 37 becomes _fH . This signal of frequency f _H is input to the delay time variable circuit 33 as a delay time control signal 303, and controls the delay time variable circuit 33 so that the delay time becomes τ _H. When the delay time of the variable delay time circuit 33 reaches τ _H , the output of the phase difference detection circuit 35 becomes zero and the closed loop is stabilized. The phase difference φ ₂ of the received sound waves can be measured by the frequency f _H of the voltage variable oscillator. As the delay time variable circuit 33 in this embodiment, a shift register or an analog delay line is used. When a shift register is used, the signal 102 is converted into a digital signal and input to the shift register, and a delay time control signal 303 is added as a clock signal. An example of an analog delay line is a CCD (charge coupled device). The delay time control signal 303 is also used as the CCD clock signal. In this embodiment, there are two receivers, but the present invention can also be applied to a device having three or more receivers. For example, with receiver 2 as the reference receiver, receiver 1 is one selected from a number of receivers by a switch.
The present invention also includes a method in which this method is used. In this embodiment, the input signals 103 and 20 of the phase difference detection circuit 35 are
This method detects the azimuth angle γ by controlling in a closed loop so that the phase difference with An angle measurement error caused by the large phase difference φ, which is inevitable in the conventional method shown in FIG. 2, does not occur. Furthermore, since this embodiment does not use a 90° phase shift circuit, it does not have the drawback of the conventional method shown in FIG. 2 that the angle measurement accuracy depends on the frequency of the received sound wave. Furthermore, this embodiment requires a large number of delay circuits and multipliers depending on the angle measurement range θ _A and the angle measurement resolution θ _i ,
There is also no disadvantage of the conventional system shown in FIG. 4, which is that the circuit is complicated.

As described above, according to the present invention, it is possible to provide an underwater acoustic positioning device with good angle measurement accuracy and a simple configuration.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the principle of measuring the direction of arrival of received sound waves, Fig. 2 is a block diagram of a conventional underwater acoustic positioning device that measures azimuth from the phase difference, and Fig. 3 is a characteristic diagram of the device shown in Fig. 2. Figure 4 is a block diagram of a conventional underwater acoustic positioning device that measures azimuth from the time difference.
Figure 6 is a block diagram of one embodiment of the present invention, Figure 6 is a characteristic diagram of the variable voltage oscillator of this embodiment, Figure 7 is a characteristic diagram of the variable delay time circuit of the aforementioned embodiment, and Figure 8 is a diagram of the characteristics of the variable delay time circuit of the aforementioned embodiment. FIG. 1, 2... Receiver, 33... Variable delay time circuit, 34... Fixed delay circuit, 35... Phase difference detection circuit, 36... Integrating circuit, 37... Variable voltage oscillator, 38... Frequency voltage converter.

Claims (1)

[Claims] 1. The first converts each received sound wave into an electrical signal.
and a second wave receiver, a first delay circuit that applies a time delay of a length corresponding to the frequency of the delay time control signal to the output of the first wave receiver, and a first delay circuit of the second wave receiver. a second delay circuit that gives a predetermined time delay to the output, a circuit that detects a phase difference between the outputs of the first and second delay circuits, and a sample value of the phase difference detection circuit at predetermined time intervals. The circuit includes an integrating circuit, and a circuit that generates the delay time control signal having a frequency corresponding to the output of the integrating circuit, the first delay circuit, the phase difference detecting circuit, the integrating circuit, and the delay time. A closed loop is formed by a circuit that generates a control signal, the closed loop is controlled so that the output signal of the circuit that detects the phase difference becomes zero, and the direction of arrival of the received sound wave is detected from the frequency of the delay time control signal. Underwater acoustic positioning device.