JPS6359114B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is based on the Doppler effect that occurs when ultrasonic waves are emitted from a ship into the sea, and the reflected waves are reflected by the seabed or floating objects in the sea (for example, schools of small fish, puncton, etc.). This invention relates to a method for measuring a ship's ground speed or water speed.

As a method for measuring frequency deviation due to the Doppler effect, a phase lock circuit, the basic configuration of which is shown in FIG. 1, has conventionally been used. In FIG. 1, 20 is a phase detector, 21 is a low-pass filter, and 22
is a voltage controlled oscillator. This circuit uses the reflected wave signal voltage ef ₂ and the output signal voltage of the voltage controlled oscillator 22.
ef ₁ is introduced into the phase detector 20, and the phase difference changes voltage ef ₁ −ef ₂ based on the frequency difference between both signal voltages.
is detected and inputted to the low-pass filter 21 to extract the DC signal voltage V corresponding to the changing voltage ef ₁ -ef ₂ . Thereby, the frequency of the output signal voltage of the voltage controlled oscillator 22 is tracked to match the frequency of the reflected wave, and the change in the frequency of the output signal of the voltage controlled oscillator 22 is measured to measure the ship speed, etc. .

However, in general, reflected waves do not maintain a constant frequency, and are usually mixed with frequency components other than the original Doppler component due to various disturbances. Therefore, if the reflected wave is directly tracked by the phase lock circuit, the measured value will be unstable. Furthermore, if one were to simultaneously measure the water velocity at multiple points at different depths, the number of phase lock circuits required would be equal to the number of points, which would complicate the device and increase costs.

In order to solve these difficulties, the present invention generates a gate signal with a time width equal to N wavelengths of the reflected wave, and uses a counter to set the time width of the gate signal to a sufficiently high frequency compared to the reflected wave. The ground speed is measured by counting the pulses that have a certain frequency and processing them using statistical methods to detect only the parts that maintain a certain frequency. This provides a method for measuring water velocity at multiple points.

An embodiment of the present invention will be described below with reference to the drawings.

In Figure 2, 1 is a transmitter that transmits ultrasonic pulses, 2 is a transmission/reception switching circuit, 3 is an ultrasonic transducer, 4 is a receiver that applies AGC and STC to the received wave and dewidth it, and 5 is this receiver. 6 is an oscillator that generates a frequency sufficiently higher than the transmission frequency; 7 is an AND gate; 8 is a counter; and 9 is a latch. 10 is a monostable circuit which outputs a load signal g to the latch at the fall of the input signal d. 11
is also a monostable circuit, and outputs a reset signal h to the frequency divider 5 and counter 8 at the fall of the load signal g. 12 is a calculator, 13 is a display connected to the calculator 12, and 14 is a detector for detecting the output signal C from the receiver 4.

The operation of the apparatus configured as described above will be explained below with reference to FIGS. 3 and 4. Ultrasonic pulses a generated by a transmitter 1 are supplied to an ultrasonic transducer 3 via a transmission/reception switching circuit 2. Transducer/receiver 3
emits an ultrasonic pulse diagonally downward underwater, receives the reflected wave, converts it into an electrical signal, and supplies it to the receiver 4. FIG. 3b shows a reflected signal reflected from floating objects in the water and a reflected signal reflected from the seabed. This received signal b is amplified by the receiver 4 and inputted to the frequency divider 5 as an output signal as shown in FIG. 3C and its enlarged view FIG. 4C. The frequency divider 5 divides the frequency by 1/N, and since the gate 7 is turned on only during the high level period, the counter 8 counts the oscillation frequency e of the oscillator 6. FIG. 4d shows the output of the frequency divider 5, and in this embodiment, the signal C is frequency-divided to 1/10. 4e is the output of the oscillator 6, and FIG. 4f is the output of the gate 7. 1/N
At the fall of the output signal d of the frequency divider 5, which is divided into
A load signal g of the monostable circuit 10 is obtained, and the count value counted by this signal g is stored in the latch 9.

The count value obtained in this way represents the reciprocal of the frequency of the reflected signal, that is, the period. Further, at the falling edge of the load signal g, a reset signal h, which is the output of the monostable circuit 11, is obtained, and the counter 8 is reset by this signal h, and the frequency divider 5 is set to N-1. This allows the output of the frequency divider 5 to be at a high level for a longer period of time as shown in FIG. 4d, making it possible to increase the number of data samples.

On the other hand, in order to detect the seabed reflected signal from the reflected signal b, the receiver 4 performs AGC,
The amplified signal l subjected to STC is detected by a detector 14 to obtain a detected envelope signal as shown in FIG. 3m.

Next, the computer 12 will be explained. FIG. 5 shows details of the computer 12. In Figure 5, 12-1 is a discrimination circuit, 12-2 is a submarine signal discrimination circuit, and 12-3
is a gate circuit, 12-4 is a memory circuit, 12-
5 is a write address generation circuit, 12-6 is a read address generation circuit, 12-7 is a timing signal generation circuit, 12-8 is an average value calculation circuit, 12-
9 is a standard deviation calculation circuit, 12-10 is an addition circuit,
12-11 is a subtraction circuit, 12-12 is a discrimination circuit,
12-13 is an average value calculation circuit, and 12-14 is a speed conversion circuit.

First, the data storage operation will be explained.

The determination circuit 12-1 determines that among the counted data An sent from the latch circuit 9, it has a clearly unreasonable value when converted to ship speed, for example, a value corresponding to a value other than -6 knots to 30 knots. The remaining Bn data are sent to the gate circuit 12-3 every reset signal h. This operation eliminates data that is clearly considered abnormal from subsequent statistical methods, resulting in greater stability.

Further, the envelope signal m of the reflected signal detected by the wave detector 14 is compared with a preset threshold value, for example, by the submarine signal discrimination circuit 12-2, and after being determined as a submarine reflected signal, the gate circuit 12-2 is open, allowing data to pass only for the duration of the seabed reflection signal. In this way, n pieces of data having valid values pass through the gate circuit 12-3 and reach the memory circuit 12-4.

On the other hand, write address generation circuit 12-5 generates an address signal that is updated according to a timing signal from timing signal generation circuit 12-7.

If the cycle of to is set slightly shorter than the expected cycle of the reset signal h, all of the Bn pieces of data mentioned above will be sequentially stored in the memory circuit 12-4.

Next, when the transmission of the above operation is repeated K times, the memory circuit 12-4 has _k 〓 ⁿ⁼¹
This means that Bn valid data are stored, forming one population. Also, the memory circuit 12-4
Since there is a limit to the storage capacity of the memory circuit 12-4, if the data from the oldest transmission is sequentially rewritten in the above operation, the data up to K times before the current time will always be stored in the memory circuit 12-4. .

Next, the calculation operation will be explained. First, the timing signal from the timing signal generation circuit 12-7
In accordance with _t1 , the read address generation circuit 12-6 sequentially generates an address signal for reading out the entire population stored in the above operation. Memory circuit 1
The data read from 2-4 is sent to an average value calculation circuit 12-8, a standard deviation calculation circuit 12-9,
The population mean and standard deviation values are calculated.

Note that the calculation of the average value and standard deviation value of the population may be performed every K transmission repetitions, or may be performed every time new data is rewritten on a moving average basis.

The adder 12-10 adds the average value and the standard deviation value to obtain the upper limit discrimination condition. Similarly, the subtracter 12-11 subtracts the standard deviation value from the average value to obtain lower limit discrimination conditions, which are respectively set in the discrimination circuit 12-12.

Next, in accordance with the timing signal _t2 , the read address generation circuit 12-6 again generates an address signal for reading data from the population. The data read here is selected based on required response time characteristics for part or all of the population. In this case, the more data that goes back to before the current time is used, the worse the response characteristics will be, but the stability will be improved.

The data read from the memory circuit 12-4 is passed to the discrimination circuit 12-12 under the discrimination conditions (average value + standard deviation value) and (average value - standard deviation value).
The En pieces of data belonging to those other than between are excluded, and the remaining Cn pieces of data are computed in the average value calculation circuit 12-13 to obtain an average value.

In this way, even if the input data fluctuates, the average of the population is always dynamically determined, and data that occurs with a small frequency that is a standard deviation away from the average value of the population can be eliminated. , instability caused by disturbances is removed, and a more stable average value can be obtained. It goes without saying that this standard deviation value can also be used as an index representing the variability of data.

Next, the Doppler frequency is determined from the period of the reflected wave in the speed conversion circuit 12-14, and then converted into a required speed value and displayed on the display circuit 13.

In the detailed embodiment of the calculator described here, the count value representing the period of the input reflected signal is operated on and then converted into a speed value, but the same effect can be obtained even if the reverse is done. The matter is clear.

Further, although the computer in this embodiment is constructed by combining individual circuit blocks, it is also possible to construct a part or the whole virtually on the storage device of the computer and control it with software.

The above explanation is about ground speed measurement, but when measuring the water speed at a given depth at multiple points at different depths, it is necessary to A similar implementation can be achieved with the same circuit configuration by replacing it with a time gate signal generation circuit corresponding to the propagation time of the sound wave to the required depth.

Further, although the above embodiments have been described with respect to a single beam, it is clear that in the case of a commonly used four-beam system, the above-described method is applied to each beam.

As mentioned above, the instability caused by various disturbances when measuring the ground speed or water speed of a ship has been significantly improved, and when measuring the water speed at multiple points at each depth, it is possible to use a single circuit. The practical effect of being able to realize an inexpensive device because of its ability to measure is remarkable.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a conventional phase lock circuit for measuring frequency deviation due to the Doppler effect, Fig. 2 is a block circuit diagram showing an embodiment of the present invention, and Figs. A waveform diagram showing the signal waveforms of each main part of the embodiment circuit and the timing between the signals, and FIG. 5 is a block circuit diagram showing details of the computer 12. 1... Transmitter, 2... Transmission/reception switching circuit, 3... Transmitter/receiver, 4... Receiver, 5... Frequency divider, 6... Oscillator, 7... Gate, 8... Counter, 9... Latch, 10, 11... Monostable circuit, 12... Calculator, 13... Display, 14... Detector, 12-1
...Discrimination circuit, 12-2...Submarine signal discrimination circuit,
12-3...gate circuit, 12-4...memory circuit, 12-5...write address generation circuit,
12-6...read address generation circuit, 12-
7... Timing signal generation circuit, 12-8... Average value calculation circuit, 12-9... Standard deviation calculation circuit,
12-10... Addition circuit, 12-11... Subtraction circuit, 12-12... Discrimination circuit, 12-13... Average value calculation circuit, 12-14... Speed conversion circuit.

Claims (1)

[Scope of Claims] 1. A method of emitting pulsed ultrasonic waves from an ultrasonic transducer and detecting the speed of a ship using Doppler components included in reflected waves from a stationary or moving object. A gate signal having a time width equal to N wavelengths of the reflected wave is generated, and the time width of the gate signal is counted by a counter using a pulse having a sufficiently high frequency compared to the reflected wave. Collect the number An corresponding to the pulse width,
Bn excluding those Dn that clearly deviate from the speed range of the ship from the ultrasonic transducer
Furthermore, the mean value and standard deviation value of the population of _n = ^{n = 1} Bn are calculated for the number of repetitions K of transmissions, and the Values other than the average value minus the standard deviation value and the average value plus the standard deviation value
An ultrasonic Doppler velocity detection method, characterized in that the average value of Cn values excluding En values is calculated and converted into a relative velocity between the ultrasonic transducer and the object.