JPS6148674B2 - - Google Patents

Description

Detailed Description of the Invention This invention is a guidance device for an underwater vehicle that uses ultrasonic waves, and uses the Doppler effect to receive the reflected sound of a sound wave emitted by itself, so that a reflector moves with a stationary object. The present invention relates to a Doppler sampling time setting device for an underwater vehicle that changes the length of the Doppler sampling time according to external conditions when distinguishing it from an object.

As a guidance device for underwater vehicles using ultrasonic waves, it captures the reflected sound (echo) of the sound waves emitted by itself.
Tracking a target using this signal is known as active homing. It is also well known that this method uses the Doppler effect to detect the frequency of reflected sound and distinguish that the reflecting object is a moving object rather than a stationary object such as a rock.

In order to take advantage of this Doppler effect, it is necessary to always know what frequency the ultrasonic waves emitted by themselves are reflected from stationary objects. Therefore, the underwater vehicle detects the volumetric reverberation of the sound waves it itself oscillates, and stores the frequency as the echo frequency from the stationary object. This operation is called Doppler sampling. Only when the frequency of the echo arriving from the target deviates from the stored frequency by more than a certain value, it is determined that the echo is a reflected echo from the target.

FIG. 1 shows this state, with the input level plotted on the vertical axis and time t plotted on the horizontal axis. In FIG. 1, P ₁ indicates the oscillation pulse, Δt is the sampling time, the volume residual tube T ₁ at this sampling time is detected, and in the relationship between its frequency ₀ and the echo frequency _E , | _E − ₀ If |≧Δ, it is determined that it is a reflected echo from the target and the Doppler gate is opened.

By the way, this Doppler sampling conventionally employs a method of sampling at a predetermined time under any external conditions. For this reason, an underwater vehicle traveling near the water surface (or the water bottom) may detect and store frequencies due to water surface (or water bottom) reverberations.
This conventional Doppler sampling method is described with reference to FIGS. 2a and 2b. FIG. 2a shows the relationship between the underwater vehicle 1 and the sampling range SE,
The volume reverberation reflected from this sampling range SE is sampled. Also, in Figure 2b, the input level is plotted on the vertical axis, similar to Figure 1.
Time is plotted on the horizontal axis, and parts corresponding to those in FIG. 1 are given the same reference numerals.

This conventional Doppler sampling method always performs sampling for a predetermined time Δt from a predetermined time (a point delayed by t ₁ after the end of the transmission pulse shown in FIG. 2b). In addition, with this Doppler sampling method, it is necessary to consider the fact shown in FIG. 3. Figure 3 a corresponds to Figure 2 a, and shows the underwater vehicle 1 and the sampling range.
Fig. 3b shows the relationship between the sampling range and the input level. In FIG. 3a, when the underwater vehicle 1 is traveling at a speed V _T , the signal from the sampling range SE on the O-A line and the sampling range SE on the O-B line
In the signal from , the frequency changes by cosθ.
Since the transducers used in normal navigation vehicles have directivity, the O-A
Since there is a difference in level between the signals on the line and the O-B line, the frequency of the signal on the O-A line is mainly stored.

Here, a conventional guidance device using the above-mentioned Doppler sampling method will be explained with reference to the block diagram of FIG. 2 in FIG. 4 is a pulse oscillation Doppler sampling control circuit, which is a circuit that commands the interval and width of oscillation pulses and the timing and time of Doppler sampling, and this pulse oscillation Doppler sampling timing control circuit 2
The high-frequency pulse oscillation circuit 3 oscillates high-frequency pulses at specific intervals based on the output from the high-frequency pulse oscillation circuit 3, and sends them to the power amplification circuit 4. This power amplification circuit 4 is configured to amplify the power when receiving a pulse from the high frequency pulse oscillation circuit 3 and send it to the transducer 5.

The transducer 5 converts the high-output electrical pulse signal from the power amplification circuit 4 into an ultrasonic wave, and emits the transmitted sound 6 into the water toward the target 7.
It is configured to receive reflected sound (including reverberation) 8 from the input signal, convert it into an electrical signal, and send it to an input signal amplification circuit 9. The input signal amplification circuit 9 amplifies the electrical signal of the reflected sound from the transducer 5,
The signal is output to the level detection circuit 10. The level detection circuit 10 receives TVG (time variable gain =
Control the input signal according to its distance. ) detects that the output (reflected sound 8) of the input signal amplification circuit 9 is at a predetermined level or higher and activates the Doppler detection circuit 11 in order to prevent malfunctions due to reverberation of the ultrasonic waves oscillated from the transducer 5. It is now output to .

Further, the pulse oscillation Doppler sampling timing control circuit 2 instructs the Doppler sampling circuit 12 to perform the Doppler sampling timing and time. The system detects the frequency of reverberant sound according to the command, and stores that frequency as the sound reflected from a stationary object. This Doppler sampling circuit 12 is configured to send the stored frequency to the Doppler detection circuit 11, and based on this frequency, the Doppler detection circuit 11 determines whether the reflected sound is from a moving object. The results of the discrimination are sent to the direction discrimination circuit 13.

The direction discrimination circuit 13 is based on this Doppler detection circuit 11.
In response to the output of
It is now being sent to This steering circuit 14
The submersible vehicle is steered by the signal from the azimuth discrimination circuit to guide the underwater vehicle toward the target 7.

In conventional guidance devices having such a configuration and operation, when an underwater vehicle travels near the water surface (or the water bottom), problems as shown in FIGS. 5a to 5c occur. Figure 5 a shows the vehicle 1
Figure 5b shows the case where the is sailing near the water surface 15 (or the water bottom), and Figure 5b shows the input level on the O-B line and the O-A line in Figure 5a (the transducer 5 receives reflected sound 8). Furthermore, FIG. 5c shows the relationship between this input level and time. In Fig. 5c, _tX shows that the frequency of Doppler sampling is influenced by the water surface reverberation frequency, and xy shows that water surface reverberation is added.

As shown in FIGS. 5a to 5c, when the underwater vehicle 1 travels near the water surface 15 (or the water bottom), the signal reflected by the water surface 15 (or the water bottom) increases, and The frequency component in the direction greatly influences the sampling storage frequency of the sampling circuit 12.

The present invention was made to eliminate the above-mentioned conventional drawbacks, and includes a pulse oscillation Doppler sampling timing control circuit that commands the intervals and widths of oscillation pulses and the period and time of Doppler sampling, and A transducer that converts the sound into a sound wave and radiates it to an underwater target and receives the reflected sound from the target, and a reverberation system that prevents the reflected sound from malfunctioning due to the reverberation of the ultrasonic waves emitted from the transducer. A level detection circuit that controls the volume of the sound according to the distance and detects that the input signal is at a predetermined level or higher, and a level detection circuit that detects the frequency of the reverberant sound and uses that frequency as the sound reflected from a stationary object. The frequency stored in the Doppler sampling circuit is compared with the frequency of the reflected sound received by the transducer to determine whether the reflected sound is from a moving object and to determine whether the reflected sound is from a moving object or not. In an underwater vehicle equipped with means for guiding the underwater vehicle to a target by discriminating the direction of the sound from the axis of the underwater vehicle, the emitted ultrasonic waves are Compare the round trip time from the water surface or the water bottom with the sum of the predetermined time from the end of the firing pulse to the start of sampling and the regular sampling time, and if the round trip time is greater or equal, the Doppler sampling circuit In addition to commanding the regular sampling time as the Dotsupura sampling time, if the above round trip time is small, subtract the above predetermined time from this round trip time, and if the subtraction result is positive, use this subtraction result as the length of the sampling time. By providing a variable Doppler sampling time circuit that commands the Doppler sampling circuit to set the sampling time to 0 when Satoshi is negative, when an underwater vehicle travels near the water surface or the bottom of the water. Another object of the present invention is to provide a Doppler sampling time setting device for an underwater vehicle in which reverberations reflected from the water surface or the bottom do not affect Doppler sampling.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the Doppler sampling time setting device for an underwater vehicle according to the present invention will be described below with reference to the drawings. FIG. 6 is a block diagram showing the configuration of one embodiment. As is clear from comparing this FIG. 6 with FIG. 4 above, the difference from FIG. 4 is between the pulse oscillation Doppler sampling timing control circuit 2 and the Doppler sampling circuit 12 in FIG. , except that a variable Doppler sampling time circuit 16 is newly provided, and other parts are the same as in Fig. 4, so to avoid duplication, the same parts as in Fig. 4 are given the same reference numerals. Therefore, the explanation thereof will be omitted, and the portion of this variable Doppler sampling time circuit 16 will be mainly described.

The detailed configuration of this variable Doppler sampling time circuit 16 is shown in FIG. 7, and 16a in FIG. Inclination information θG of the running object is input, and a constant θ* determined from the directivity of the transducer 5 is given. From these inclination information θG of depth information ZG and constant θ*, the distance to the water surface RS= It is designed to calculate ZG/sin (θG+θ*). The distance RS calculated by the distance calculation circuit 16a to the water surface is the round trip time calculation circuit 16 to the water surface.
The data is now sent to b. The round trip time calculation circuit 16b to the water surface calculates the round trip time t _S =2ZG/VSsin (θG+θ*). However, VS indicates the underwater sound speed of ultrasonic waves.

This round trip time t _S to the water surface is the sum of the time t ₁ (hereinafter referred to as sampling start time) from the end of the pulse oscillation from the high frequency pulse oscillation circuit 3 until the start of sampling (hereinafter referred to as the sampling start time) and the regular sampling time Δt. That is, t ₁ +Δt is compared, and if t ₁ +Δt≦t _S , the Doppler sampling time is left unchanged at Δt and the signal is sent to the Doppler sampling circuit 12 . In addition, in the case of t ₁ +Δt≧t _S , t _S −t ₁ is calculated, and if the result is positive, the calculation result of t _S − _{t 1} is set as the Doppler sampling time, and the Doppler sampling circuit 12 The government is beginning to issue instructions to the government. Furthermore, if the calculation result of t _S -t ₁ is negative, a command is issued to the Doppler sampling circuit 12 to set the sampling time to 0. In other words, it is designed not to sample.

Next, the operation of the Doppler sampling time setting device for an underwater vehicle of the present invention constructed as described above will be described, focusing mainly on the variable Doppler sampling time circuit 16.
First, a case will be described in which the underwater vehicle 1 is traveling in a part far from the water surface (or the water bottom) to some extent. FIG. 8a is a diagram for explaining this case, in which 1 is the underwater vehicle and 15 is the water surface. In this case, the sampling range is t ₁ ~ (t ₁ + Δt)
Considering the directivity attenuation of the transducer 5, the constant θ* (angle) determined from the directivity of the transducer 5, the tilt information θG (attitude angle) of the underwater vehicle 1, and the underwater vehicle 1. The distance calculation circuit 16a to the water surface calculates the distance RS to the water surface from the depth information ZG (depth). That is, find RS=ZG/sin(θG+θ*).

The distance RS to the water surface is determined by the round trip time t _S to the water surface by the round trip time calculation circuit 16b. The round trip time t _S to the water surface is the value obtained by dividing the distance RS to the water surface by the sound speed VS of the ultrasonic wave in the water. That is, it is determined as t _S =2ZG/VSsin (θG+θ*). In this way, the round trip time t _S to the water surface is determined.
compares the time from the end of the pulse oscillated by the high frequency pulse oscillation circuit 3 until the start of sampling, that is, the sum of the sampling start time t ₁ and the sampling time Δt, (t ₁ +Δt). In other words, it is compared whether (t ₁ +Δt)≦t _S or not. As a result of this comparison, if t ₁ +Δt≦t _S , the sampling time Δt is directly commanded to the Doppler sampling circuit 12 .

Next, a case where the underwater vehicle 1 is traveling near the water surface 15 will be described. FIG. 8b is a diagram for explaining this case. In this case, the round trip time t _S to the water surface mentioned above is the sampling start time.
This is the case when it is smaller than the sum of t ₁ and sampling time Δt, that is, when (t ₁ +Δt)≧t _S.
In this case, Doppler sampling time Δt _S =
(t _S −t ₁ ), that time is newly determined as the Doppler sampling time, and the command is given to the Doppler sampling circuit 12. This makes it possible to prevent the effects of water surface reverberation.

As mentioned above, when the underwater vehicle 1 is traveling near the water surface or the bottom, (t _S −
If t ₁ ) is negative, the sampling time is set to 0, a command is issued to the Doppler sampling circuit 12, and Doppler sampling is not performed.

As described in detail above, according to the Doppler sampling time setting device for an underwater vehicle of the present invention, the pulse oscillation Doppler sampling timing control circuit commands the interval and width of the oscillation pulse and the period and time of Doppler sampling. and a transducer that converts the oscillation pulse into an ultrasonic wave and radiates it to an underwater target and receives the reflected sound from the target, and the reflected sound is caused by the reverberation of the ultrasonic wave emitted from the transducer. A level detection circuit that detects that the input signal is at a predetermined level or higher by controlling the magnitude of the reverberant sound according to its distance to prevent activation, and a level detection circuit that detects the frequency of the reverberant sound and detects whether the reverberant sound A Doppler sampling circuit stores the frequency as a reflected sound of In an underwater vehicle, the underwater vehicle is equipped with a means for discriminating the direction of the reflected sound and the axis of the underwater vehicle to guide the underwater vehicle to a target,
Based on the depth and inclination of the underwater vehicle, the sum of the time required for the emitted ultrasonic waves to travel back and forth from the water surface or the water bottom, the predetermined time from the end of the emitted pulse to the start of sampling, and the regular sampling time is determined. If the round-trip time is larger or equal, the Doppler sampling circuit is instructed to use the regular sampling time as the Doppler sampling time, and if the round-trip time is smaller, the predetermined time is subtracted from the round-trip time. and a variable Doppler sampling time circuit that instructs the Doppler sampling circuit to set the subtraction result to the sampling time length when the subtraction result is positive and to set the sampling time to 0 when the subtraction result is negative. Therefore, even when an underwater vehicle travels near the water surface or the water bottom, it is possible to prevent reverberations reflected from the water surface or the water bottom from affecting Doppler sampling.

[Brief explanation of the drawing]

Figure 1 is a diagram for explaining a situation in which the frequency of the echo from the target deviates in a conventional Doppler sampling system for guiding an underwater vehicle, and a state in which reverberation occurs on the water surface or the bottom. Diagram 2 for explaining the case of sampling volumetric reverberation in the Doppler sampling method of
Figure b is a diagram showing the relationship between time and echo input from the target, corresponding to Figure 2 a, and Figure 3 a is a diagram showing the relationship between time and echo input from the target, and Figure 3 a shows the speed of the underwater vehicle in the conventional Doppler sampling method.
This is a diagram to explain how the sampling frequency changes due to changes in the sampling range when cruising at _T. Figure 3b corresponds to Figure 3a, and the echo from the target is directed toward the transducer. Figure 4 is a block diagram showing the configuration of a guidance system using the conventional Doppler sampling method. Figure 5a is a diagram showing how the underwater vehicle in the guidance system shown in Figure 4 is located near the water surface or the bottom. Figure 5b is a diagram showing the input level of the transducer corresponding to Figure 5a, and Figure 5c is a diagram showing the Doppler sampling due to reverberant sound in the case of Figure 5a. FIG. 6 is a block diagram showing the configuration of an embodiment of the Doppler sampling time setting device for an underwater vehicle according to the present invention, and FIG. 7 is a diagram showing the variable Doppler sampling time in the same embodiment. FIG. 8a is a block diagram showing the detailed configuration of the circuit, and FIG. FIG. 8b is a diagram for explaining the variable Doppler sampling time circuit when the underwater vehicle travels near the water surface in the same embodiment. DESCRIPTION OF SYMBOLS 1...Underwater vehicle, 2...Pulse oscillation Doppler sampling timing control circuit, 3...High frequency pulse oscillation circuit, 5...Transducer/receiver, 7...Target,
10... Level detection circuit, 11... Doppler detection circuit, 12... Doppler sampling circuit, 13
... Direction discrimination circuit, 14 ... Steering circuit, 16 ...
Variable Doppler sampling time circuit, 16a...
Distance calculation circuit to the water surface, 16b... Circuit for calculating round trip time to the water surface.

Claims (1)

[Claims] 1. A pulse oscillation Doppler sampling timing control circuit that commands the interval and width of oscillation pulses and the period and time of Doppler sampling, and converts the oscillation pulses into ultrasonic waves and radiates them to an underwater target, and also generates reflected sound from the target. a transducer that receives the reflected sound, and a transducer that emits the reflected sound from the transducer.In order to prevent malfunctions due to reverberation of ultrasonic waves, the magnitude of the reverberant sound is controlled according to the distance, and the input signal is set to a predetermined level. a level detection circuit that detects the level above, a Doppler sampling circuit that detects the frequency of the reverberant sound and stores the frequency as a reflected sound from a stationary object; The frequency is compared with the frequency of the reflected sound received by the transducer to determine whether the reflected sound is from a moving object and the direction of the reflected sound with respect to the axis of the underwater vehicle. In an underwater vehicle equipped with a means for guiding the body to a target, the time required for the emitted ultrasonic waves to travel back and forth from the water surface or the water bottom, and after the emission of the oscillation pulses is completed, based on the depth and inclination of the underwater vehicle. Compare the sum of the predetermined time until sampling starts and the regular sampling time, and if the required round trip time is greater or equal, the Doppler sampling circuit is instructed to take the regular sampling time as the Doppler sampling time, and the round trip time is If the time is small, the above predetermined time is subtracted from this round trip time, and when the subtraction result is positive, the subtraction result is set as the length of the sampling time, and when it is negative, the sampling time is set to 0, and the above-mentioned Doppler sampling circuit 1. A Doppler sampling time setting device for an underwater vehicle, characterized by comprising a variable Doppler sampling time circuit for commanding.