JPH0142534B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wireless transmission device capable of transmitting data required in an underwater position measurement system that measures three-dimensional position in a narrow band.

As a system to accurately measure the three-dimensional position underwater, that is, the position of an object moving underwater, such as a navigation vehicle, three or more receivers or transponders installed on the seabed are used as reference points to measure the three-dimensional position of underwater objects. There is a so-called long baseline method in which the direct distance between the reference point and the reference point is acoustically measured, and the position of the object is calculated from the direct distance and the coordinates of the reference point. In other words, to measure the direct distance, an acoustic pulse signal is transmitted from an object, this signal is received at a reference point, the time required for propagation is measured, and this time is multiplied by the speed of sound to determine the distance between the object and the reference point. Get the direct distance of When the reference point is a wave receiver, the conventional method is to separately transmit the received signal to land or ship via a cable or wireless transmission path, and perform processing such as detection there.

Among these conventional methods, the problems with wireless transmission in particular are that it requires a wide frequency band to directly transmit the received signal, requires special lines, and that the number of transmission channels is equal to the number of reference points. This makes it difficult to obtain allocation of radio waves.

In order to eliminate these drawbacks, the present invention first uses only one reference point as a receiver and the other reference points as transponders, thereby reducing the number of necessary transmission lines to one, and furthermore, Rather than transmitting the signal as it is, it performs processing such as detection and converts it into reception time data, which can be transmitted over a normal data line, and will be explained in detail below.

FIG. 1 shows an embodiment of the present invention, in which 1 is an underwater object whose position is to be measured, 2 is a sound source device, 3 ₁ ,..., 3 ₄ are transponders, 4 is a receiver, 5 is an intermediate buoy, and 6 is a transponder.
is a surface buoy, and 7 is a surface ship. A sound source device 2 that transmits an acoustic pulse signal is attached to the underwater object 1,
The signal sent from this is transmitted to the transponder 3 ₁ ,
..., 3 ₄ and receiver 4. At least two of the transponders 3 ₁ , . . . , 3 ₄ respond to this signal, each transmitting an acoustic pulse signal of a different frequency. The signals transmitted from these transponders are received by the receiver 4 together with the signals transmitted from the sound source device 2, and the underwater cable 8
is sent to sea surface buoy 6 via. The receiver 4 is suspended by an intermediate buoy 5, and the transponders 3 ₁ ,...,
3 Similar to ₄ , it is held in a fixed position relative to the seabed. At the sea surface buoy 6, pulse signals having different frequencies are separated and detected from among the signals received by the wave receiver 4, and their reception times are measured. The measurement results are converted into a code sequence, transmitted via radio waves from an antenna, and received by the watercraft 7. Here, since the code sequence is demodulated and the measurement data is reproduced, this data is input to the onboard position calculator to calculate the position of the underwater object 1, that is, the three-dimensional position.

Figure 2 is a block diagram of sea buoy 6 and 10
11 is an input terminal, 11 is a pulse detector group, 12 is a timer group, 13 is a parallel-to-serial converter, 14 is a clock generator, 15 is a frame code combiner, 16 is a radio transmitter, and 17 is an antenna. Receiver 4 in Figure 1
The signal received at is applied to the input terminal 10 and input to each pulse detector of the pulse detector group 11. Each pulse detector detects a pulse signal of a specific frequency, and when it detects a pulse signal, it generates a trigger signal and starts the corresponding timer of the timer group 12. The clock generator 14 supplies a clock signal with a small period _T0 to each timer in the timer group 12, and outputs the output of each of these timers to the parallel-to-serial converter 13 every large period _Tf , and then immediately outputs the output of each of these timers to the parallel-serial converter 13. and prepare for operation in the next major cycle. The outputs of the timer group 12 stored in the parallel-to-serial converter 13 are read out in series at a medium period _Tt , a frame code is added to the beginning of the output in the frame code combiner 15, and the output is sent to the wireless transmitter 16. It will be done. In the radio transmitter 16, the carrier wave signal is subjected to modulation such as FSK (frequency shift keying) using a code sequence with a rate of medium period _Tt , and is sent into the air from the antenna 17.

Assume now that the number of underwater objects that can be measured simultaneously is two, and the number of transponders is four. The frequencies of the pulse signals sent by each underwater object are ₀ and ₀ ', and the frequencies of the pulse signals sent from each transponder in response are ₁ , ₂ , ₃ , _4, and ₁ ', ₂ ', ₃ ', ₄ ′. The transmission code sequence at this time is as shown in FIG. Here, F is the frame code, and ₀ , ₁ , ... are the frequencies ₀ , _1, ..., respectively.
This code indicates whether or not a pulse signal is detected and the reception time. Assuming that the start position of the frame code F is the readout time of each timer, the code at each reception time has a short cycle T ₀ with this readout time as a reference.
It represents time measured in units of (interpreted as a negative value). The time of occurrence of frame code F can be determined by receiving the transmission signal from the sea surface buoy 6 using the onboard radio receiver and comparing it with the standard clock. Therefore, the reception time code (negative value) following this frame code By adding this to the frame code generation time, the reception time of the acoustic pulse can be determined. Therefore, if the transmission timing of the transmission signal of the sound source device 2 attached to the underwater object 1 is synchronized with the standard clock in advance, the propagation time of each acoustic pulse can be measured, and the The propagation distance is determined by multiplying by the speed of sound, and the position of the underwater object 1 is calculated from this and the coordinates of the transponders 3 ₁ , . . . , 3 ₄ and the receiver 4. Transponders 3 ₁ ,..., 3 ₄ and receiver 4
The coordinates of are previously determined by a calibration operation similar to that in normal acoustic navigation.

If this device is used, it is possible to transmit the presence or absence of detection of one pulse signal for each frequency and the detection time during the large period T _f , so the transmission period T _a of the sound source device 2 can be set to be larger than the large period T _f . For example, all the time data necessary for position measurement can be transmitted to the destination via a single channel wireless transmission path. For example, in the above example, if the frame code word length is 40 bits,
Assuming that the reception time code is 20 bits and T _f = 1 second,
The transmission route is (40 + 20 x 5 x 2) = 240 bits/sec, and since transmission is possible through a low-speed data transmission path, a normal wireless line can be used.

In the above explanation, the number of underwater objects to be measured is 2,
Although the number of transponders is four and the number of receivers is one, standard usage is to arrange six transponders near the vertices of a regular hexagon and one receiver near the center. In this case, five underwater objects can be measured simultaneously by using a 35-wave acoustic pulse signal. What's more, the transmission route requires less than 1000 bits/second, making it easy to transmit over ordinary wireless lines.

In order to further widen the underwater measurement range, a set of six transponders and one receiver shown in the above standard usage may be used as one unit, and a plurality of sets may be used. However, since the wireless line must be separate, expanding the measurement range requires increasing the number of wireless lines, but since it is a low-speed data line, it is relatively easy to obtain a line assignment.

Instead of directly transmitting multi-frequency acoustic pulse signals, the present invention separates and detects multi-frequency acoustic pulse signals, encodes the reception time, and multiplexes the signals.
Since it is possible to transmit data using a single wireless transmission line, it will be highly effective if applied to a mobile underwater position measurement system.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an embodiment of the present invention, FIG. 2 is a block diagram of the sea surface buoy 6 in FIG. 1, and FIG.
The figure is a time chart of the output signal. 1... Underwater object, 3 ₁ ,..., 3 ₄ ... Transponder, 4... Receiver, 6... Sea surface buoy, 7... Surface ship.

Claims (1)

[Claims] 1. As a reference point for position measurement, one wave receiving station and a plurality of transponders are provided, and the wave receiver receives an acoustic pulse signal sent from an object whose position is to be measured and a plurality of the transponders. The device receives an acoustic pulse signal sent from a transponder, and transmits the signal received by the receiver via a wireless transmission path, and the frequencies of the acoustic pulse signals of the object and the transponder are different from each other. In a wireless transmission device configured as described above, a means for separately detecting a plurality of acoustic pulses having different frequencies, a means for measuring the time between the time of detection and a certain reference time, and a time measurement result. A wireless transmission device comprising: means for serially reading out the reference time; and means for serially combining and transmitting a code (frame code) representing the reference time and a time measurement result read out in series.