JPH0325753B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a device for measuring the speed of a ship using the Doppler effect of sound waves.

(Prior Art) Ship speed measurement devices conventionally known as Dotsuprasona or Dotsupuralog are:
A Doppler deviation corresponding to the ship's speed occurs between the sound waves emitted diagonally downward from the bottom of the ship and the received signal that is scattered and reflected by the seabed or floating objects in the water and is received again. It is something to be measured. In order to reduce measurement errors caused by tilting or oscillation of the ship, such a ship speed measurement device arranges the sound beams symmetrically, for example in the forward direction and the rear direction, and calculates the Doppler shift of each sound beam. The JANUS method is used to reduce the error based on the difference.

In addition, as another example of the prior art, JP-A-58-
There is also a speed measuring device for ships that is miniaturized using a phased array type transducer, as described in Japanese Patent No. 39970.

(Problems to be Solved by the Invention) The former conventional technology, that is, the JANUS system, requires separate transducers for the forward direction and the rearward direction, so an increase in size is unavoidable.

The latter prior art disclosed in Japanese Patent Laid-Open No. 58-39970 requires a complex beam combining circuit using phase control to separate the forward beam signal component and the backward beam signal component.

(Means for Solving the Problems) In order to solve these problems, the present invention uses a phased array type transducer to emit and receive sound wave signals in relative directions, such as forward and backward directions, and This system measures the speed of a ship by detecting Doppler shift without separating the direction beam signal component and backward beam signal component, and is designed to reduce the size of the transducer device and simplify the circuit configuration. be.

(Example) Examples of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing the principle of a phased array type transducer, in which 1 ₁ to 1 _o are the vibrating elements, d ₁ is the interval between the vibrating elements, and θ ₀ is the beam combining direction. As shown in Fig. 1, in a phased array type transducer in which n vibrating elements are arranged on a straight line with an interval d ₁ , the excitation amplitude of each vibrating element is made equal, and the excitation phase difference between adjacent vibrating elements is δ. Then, the directional characteristic E of this transducer is
(θ) is expressed by the following equation (1).

E(θ)∝sin n(πd ₁ /λsinθ−δ/2)/sin(
πd ₁ /λsinθ−δ/2)...(1) Here, λ is the wavelength of the sound wave. This E(θ) takes a maximum value when πd ₁ /λsinθ−δ/2 = mπ(m=0, ±1, ±2, . . . ) (2). Here, m=0 is the main rope, and m=±1, ±2, . . . correspond to the grating gloves. In equation (2), m
= 0 and set δ=2πd ₁ /λsinθ ₀ (3), a main rope is formed in the θ ₀ direction.
Furthermore, from equation (2), it can be seen that a grating globe is generated under the condition of d ₁ >λ/2. The beam forming method during transmission or reception uses this grating globe to form two beams, and in equation (2), the transducer element spacing d ₁ =λ, the excitation phase difference δ =
When π is assumed, a main lobe and a grating lobe appear in the direction of θ=±30°, making it possible to emit or receive sound waves in two directions simultaneously.

FIG. 2 shows another second row of vibrating elements 2 1 to _{2 o} in the phased array type transducer explained in FIG. 1.
2 is a diagram for explaining a transducer including a transducer, and the transducer is installed on the bottom 3 of the ship. The first transducer elements 1 1 are arranged so that the second transducer element rows 2 ₁ to 2 _o are located between the first transducer rows 1 ₁ to _{1 o} , respectively.
They are equally spaced at a distance of d ₂ =λ/2 with respect to ~1 _o . In order to set the excitation phase difference to π for the first vibration elements 1 _i to 1 _o , '+' and '-' in the figure are used.
The polarization direction is alternately reversed as shown by the sign φ
They are grouped together as phases. Similarly, the second vibrating elements 2 ₁ to 2 _o perform polarization similar to the former and have π/
It is summarized as two phases.

During transmission, the angular frequency ω is applied to the φ phase or π/2 phase.
By sending an electric signal, a sound wave is emitted in the direction of θ ₀ =±30° based on the principle described above. Furthermore, even when each vibrating element row 1 ₁ to 1 _o and 2 ₁ to 2 _o is simultaneously excited with an electric signal having the same phase as the φ phase and the π/2 phase, the equivalent vibrating element spacing is λ, and the equivalent excitation position is The phase difference becomes π, and a sound wave can be emitted in the direction of θ ₀ =±30°, similar to when the φ phase or the π/2 phase is excited independently.

When receiving waves, the sound waves are scattered and reflected by the seabed or floating objects in the water, and are received again after undergoing a Doppler shift depending on the relative speed between the ship and the reflecting objects. This is shown by the following relational expression.

ωd＝2ωVsinθ ₀ /C ...(4) Here, ωd: Doppler deviation angular frequency ω: Transmission angular frequency V: Relative velocity C: Sound speed At this time, in Fig. 2, the ship moves in the χ direction at a speed V. If so, a sound wave emitted as a forward beam will undergo a positive Doppler deflection, and conversely a sound wave emitted as a backward beam will undergo a negative Doppler deflection. As a result, a cos from the front direction
A sound wave (ω+ωd)t arrives, and b
A sound wave of cos(ω-ωd)t arrives.

These sound waves arriving from the front and rear directions have their sound sources far enough away and can be regarded as plane waves, so the φ phase, which combines the first transducer arrays 1 ₁ to 1 _o , has the opposite operation when transmitting waves. As a result, signals in two directions appear in the form of simultaneous addition. Therefore, the following signal appears in the φ phase: φ phase: a cos (ω+ωd) t+b cos (ω−ωd) t (5). On the other hand, the second vibrating element array 2 ₁ -
In the π/2 phase that combines 2 _o , the first vibrating element row 1 ₁
1 _o and the second transducer element array 2 ₁ to 2 _o , the following phase change occurs due to the difference in spatial arrangement. In Figure 2, the forward beam component a cos(ω+ωd)t
requires an extra propagation path by d ₂ sin θ ₀ for the first transducer array 1 ₁ to 1 _o to reach the second transducer array 2 ₁ to 2 _o , and the backward beam component b
cos(ω-ωd)t reaches the second transducer arrays 2 ₁ to 2 _o earlier by a propagation path difference of d ₂ sin θ ₀ than the first transducer arrays 1 ₁ to 1 _o . As a result, the amount of phase change caused by the difference in the propagation paths is 2π/λd ₂ sinθ ₀ =2π/λd ₂ δλ/2πd ₁ =π/2...
…(6) becomes. Here, using equation (3), δ=π and d ₁ =2d ₂ were set.

Summarizing the above, the output of the π/2 phase with the φ phase as the reference is as follows, taking into account the delay and lead of the phase: π/2 phase: a cos {(ω+ωd)t−π/
2}+b cos {(ω-ωd)t+π/2} =a sin(ω+ωd)t-b sin(ω
-ωd)t...(7)

FIG. 3 shows an embodiment of the present invention of a device for measuring the speed of a ship using the transducer. 1 ₁ to 1 _o are the first transducer element array, 2 ₁ to 2 _o are the second transducer element array, and 3
is the bottom of the boat, 4 is a transducer, 5 is a signal generator, 6 is a transmitter, 7a and 7b are transceiver switches, 8a and 8b are amplifiers, 9a and 9b are frequency mixers, 10a and 10b are low-pass filters, 1
1 is a fast Fourier transformer, 12 is a velocity calculator, and 13 is a display.

The operation during wave transmission is as described above, if the transmitter 6 generates a transmission pulse based on the angular frequency ω generated by the signal generator 5, passes through the transmitter/receiver switchers 7a and 7b, and drives the transducer 4. Before and after ±
Generates two sound beams in 30° directions.

Next, regarding the operation at the time of reception, the reception signal shown by equation (5) appears in the φ phase that combines the first transducer element rows 1 ₁ to 1 _o , and on the other hand, the reception signal shown by equation (5) appears in the φ phase that combines the first transducer element rows 1 ₁ to 1 o.
A received signal expressed by equation (7) appears in the π/2 phase that combines 2 _o . These two signals pass through duplexers 7a and 7b, are amplified to appropriate magnitudes by amplifiers 8a and 8b, and are guided to frequency mixers 9a and 9b. Then, the frequency is mixed with the angular frequency ω generated by the signal generator 5, and the outputs thereof are passed through the low-pass filters 10a and 10b, so that the transmission angular frequency ω and the reception angular frequency ω+
Doppler deviation components +ωd and −ωd, which are the differences between ωd and ω−ωd, are extracted. Here, if we define the signal corresponding to the φ phase as 'REAL' and the signal corresponding to the π/2 phase as 'IMAG', then the low pass filter 10
The outputs of a and 10b are frequency-converted and become as follows.

REAL: Acosωdt + Bcos (-ωdt) ...(8) IMAG: Asinωdt-Bsin (-ωdt) ...(9) Here, A and B are the amplitude of the forward beam after amplification or frequency conversion and the backward direction Indicates the beam amplitude. Also, each component of (8) and (9) is cos(−
According to the relationships θ)=cosθ and sin(−θ)=−sinθ, it can be converted as follows.

REAL: Acosωdt + Bcosωdt ...(10) IMAG: Asinωdt+Bsinωdt ...(11) Now, we introduce the concept of complex numbers, and let the REAL signal represented by (10) be a real number term, and the IMAG signal represented by (11). Considering the following complex number g(t) as an imaginary term, g(t)=(REAL)+j(IMAG)=(Acosωdt+Bcos
ωdt)+j(Asinωdt+Bsinωdt) =Ae ^j 〓 ^dt +Be ^jwdt (12). As shown in FIG. 4, this is given by combining the vector Ae ^j 〓 ^dt due to the Doppler deviation of the forward beam and the vector Be ^j 〓 ^dt due to the Doppler deviation of the rear beam. Also, since the vector rotation by the forward beam and the vector rotation by the backward beam both have the same ωd,
The composite vector shown in (12) has the size |A+B
It can be seen that | is a simple vector rotating with an angular frequency ωd.

Next, the fast Fourier transformer 11 converts the power spectrum based on the signals of the real term 'REAL' shown in (10) and the imaginary term 'IMAG' shown in 11 in order to obtain the rotational angular frequency ωd of the composite vector. and detect the angular frequency ωd of the unknown input signal by its maximum value or first moment (average frequency). Then, the velocity calculator 12 calculates, based on the angular frequency ωd detected by the fast Fourier transformer 11, V=ωd・C/2ωsinθ゜ according to the modified form of the following equation (4)... (13) Movement of the ship The speed V is determined and output to the display 13.

In the above example description, a fast Fourier transformer was used to determine the rotational angular frequency ωd of the vector, but it is also possible to measure the speed of the ship by determining the Doppler shift based on the amount of phase change of the vector per unit time. is also possible.

Further, in the above embodiment, velocity measurement was described in which the direction in which the sound waves are emitted is the front-rear direction, but if the sound waves are emitted in the left-right direction as well, velocity components in the front-rear, left-right and front-rear directions can be obtained at the same time.

(Effects of the invention) As explained above, by using a phased array type transducer, it is possible to downsize the device, and at the same time, it is possible to reduce the size of the device spatially without using a beam combining circuit to separate two beams in relative directions. By directly vector processing the outputs of two vibrating element arrays having different arrangements, the Doppler deviation frequency can be directly detected, which has the advantage of greatly simplifying the circuit configuration of the speed measuring device.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the operating principle of a phase array type transducer, FIG. 2 is a diagram for explaining the signal output during wave reception in the transducer according to the embodiment of the present invention, and FIG. 4 is a block diagram showing an apparatus according to an embodiment of the present invention, and FIG. 4 is a diagram for explaining a complex vector corresponding to a Doppler deviation. 1 ₁ to 1 _o ...First transducer element row, 21 to _{2 o} ...Second transducer element row, 3...Bottom, 4...Transducer/receiver, 5
...Signal generator, 6...Transmitter, 7a, 7b...
Transmission/reception switch, 8a, 8b...Amplifier, 9a, 9b
...Frequency mixer, 10a, 10b...Low pass filter, 11...Fast Fourier transformer, 12
...Speed calculator, 13...Display device.

Claims (1)

[Claims] 1. A transducer in which a second transducer array is arranged between first transducer arrays arranged at intervals of one wavelength at a distance of 1/2 wavelength from the first transducer array, and the wave transmitter/receiver. a transmitter for emitting two sound wave beams in relative directions by a device; and a circuit for frequency converting the two signals of the first vibrating element row and the second vibrating element row by the signal frequency emitted by the transmitter. and 2 obtained by the frequency conversion circuit.
1. A speed measuring device comprising: means for determining the rotational angular frequency of a vector having two signals as components; and a speed calculator for determining the moving speed of a ship from the determined angular frequency.