JPS5912994B2 - Marine ultrasonic speed meter error correction method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an error correction method for a Doppler ultrasonic speed meter for ships, the purpose of which is to obtain information equivalent to the equivalent ground speed from the water speed.

Doppler speedometers, which emit ultrasonic waves toward the seabed and utilize the Doppler effect of the reflected waves, have recently come into use in ships, and are attracting attention as their usefulness as ground speedometers has been recognized.

However, ultrasonic waves attenuate significantly beyond a certain depth (approximately 150 m), making it difficult to detect them when reflected from the seabed.
Doppler speedometers can no longer be used as ground speedometers.

For this reason, conventionally, above a certain depth, the reflection from the seafloor mass is detected and used as a water velocity meter.

When operating as a water speed meter, it does not indicate the true ground speed due to the influence of currents and winds, so the route calculated by this measurement includes an error, but no method has been taken to correct this error in the past.

In other words, ground speed is necessary for navigation, but since the sea areas in which ships navigate are generally deep, the Doppler method can almost only operate in water mode.

On the other hand, however, since the routes traveled by general ships are almost constant, a certain relationship can be empirically determined between the voyage obtained by integrating the speed relative to the water and the actual voyage obtained on the nautical chart.

Therefore, if the velocity relative to water is corrected at a certain rate,
The obtained route almost matches the actual route.

In light of the above, the present invention aims to obtain information equivalent to equivalent ground speed from water speed.

There are various error factors in the Doppler ultrasonic speed meter, and they are comprehensively corrected at the time of factory testing or trial run. In the special Doppler sonar and Doppler log, which is characterized by making corrections to suit the The time width is controlled by the gate pulse width.

Therefore, by changing this gate pulse width from the reference value (after the above-mentioned total error correction) only in the water mode, the above-mentioned error compensation can be achieved.

In order to correct errors caused by the influence of tidal currents, the method of determining ground speed by adding or subtracting the tidal current value determined from a current chart to the ship's speed relative to the water is difficult. However, the number of corrections is difficult because the tidal current value changes depending on the date and time and sea area. This has the disadvantage that it becomes a hassle and the correction device becomes complicated.

In contrast, the present invention can easily and easily calculate the integrated value of water speed by considering the average value in a certain section (or from a port of departure to a port of entry, or from a certain point of departure to a point of arrival). This is what you are trying to modify to the value.

That is, the gate pulse width of the Doppler ultrasonic speedometer to which the present invention is applied is kept at the above-mentioned reference value, and the target section is sailed once, and then the measured distances A1 and A2 are calculated from the actual distance B determined from the nautical chart. , B=At (1+e1)
and B=A2(1+e2) to calculate the errors e1 and e2 during the round trip voyage due to the influence of the tidal current.

Then, during the second voyage, the gate pulse width was adjusted to the standard value (
1+et) times and (1+62) times.

In addition, if the results from the second voyage are taken into account during the third voyage, the correction accuracy will be further improved, and multiplying the reference value of the gate pulse width by a coefficient is extremely effective as a correction method for voyages along almost the same route in a certain section. It is simple and fully practical.

Hereinafter, details of the method of the present invention will be explained with reference to specific configuration circuit examples.

In Figure 1, first, the frequency f oscillated by nuclear power plant 1
The frequency o is divided by 1/M by the frequency divider 2, thereby determining the period T=M/fo of the gate pulse.

Further, this frequency fo is divided by 1/N by the frequency divider 3, thereby determining the reference frequency fo/which determines the gate pulse width.
N is created.

A portion 7 surrounded by a dotted line in the figure and consisting of a phase detector 4, a voltage controlled oscillator 5, and a preset counter 6 is a well-known phase synchronization circuit, into which a signal fo/N is input and a value of X is set in the preset counter 6. , the voltage controlled oscillator outputs a frequency of fo.

This signal foe is further divided into 1/1000 by the frequency divider 8, and then applied to the reset terminal of the A flip-flop 9 to reset it.

The A flip-flop 9 is set by the above-mentioned periodic signal fo/M, and at the same time the frequency divider 8 is reset and starts dividing from the beginning, so the time until the A flip-flop 9 is reset is equal to the frequency XI N
The reciprocal of 100O foNlooO becomes , and this is the
X This is the gate pulse width when converting the plastic shift into a speed value.

The reference value is when the set value X of the preset counter 6 is set to 1000, and N/fo is the reference gate pulse width.

If there is a factor that affects the accuracy of the system, such as an installation error, the gate pulse width can be arbitrarily changed in units of 0.1% by setting the value of X according to the degree of the factor.

The gate pulse thus obtained is used as a gate pulse when measuring ground speed.

Setting of the water mode error correction value (that is, the correction value for obtaining the equivalent ground speed from the water speed) can be performed in the same manner.

That is, the error correction value Y is set in the coincidence circuit 11, and its sign is set in the contact 1 by the interlocking switch 12 when it is positive and at the contact 2 when it is negative.

The counter 13 uses the output signal fOX of the voltage controlled oscillator 5 as an input, and the counter 13 counts this signal.
If it becomes Y, the coincidence circuit 11 switches to the B flip-flop 1.
Sends a reset signal to 4.

If the time when the count number reaches Y is t, then fo M t
= Y, so t=NY/foX.

Since the setting of the B flip-flop 14 and the reset of the counter 13, that is, the start of counting, occur at the same time, the output pulse width of the B flip-flop 14 is NY/foX.

The pulse determined by the water mode error correction value Y is added or subtracted as a correction value from the pulse determined by the A flip-flop 9 in the pulse synthesis circuit 15.

The results are shown in Figure 2, and the water speed measurement gate pulse width is 1000·N + Y, N -X
fo X f.

1000・N (1±□ product.

), and the value of Y is ground speed X f.

0.1% of the standard value of 1000 N for temperature measurement gate pulse width
Xf.

You can add or subtract in units.

In addition, when measuring normal water speed using the ultrasonic speed meter for ships according to the method of the present invention, the correction value of Y set in the matching circuit 11 is set to zero, and the interlocking switch 12 is set to contact 1,
Set it to either of 2.

As described above, according to the method of the present invention, the pulse width determined by the water mode error correction value Y can be determined independently, thereby not disturbing the adjusted reference pulse width determined by X.

[Brief explanation of drawings]

FIG. 1 is a configuration circuit diagram of an embodiment of the method of the present invention, and FIG.
This is an explanatory diagram of the pulse width in each part of the figure.

Claims (1)

[Claims] 1 Receiving the reflected waves of the ultrasonic waves emitted from the ship from the seabed or from the seafloor mass at a predetermined depth, and counting the Doppler frequency (△f) signals of the reflected waves included in the standard gate time In the method of measuring ground speed or water speed, when navigating in a section at a depth greater than a specified depth where ground speed cannot be measured, the specified point on the nautical chart, which was obtained during a past navigation on approximately the same route in the above section, is used. Based on the difference between the distance obtained assuming that the ship sailed at an average speed and the measured distance obtained at the same average speed over the water as the above-mentioned average speed over the ground, calculate the above-mentioned reference gate time for measuring speed over the water. A method for correcting errors in an ultrasonic speedometer for ships, characterized by adjusting the width and obtaining equivalent ground speed from water speed based on this.