JPH06347548A - Ship speed measuring instrument - Google Patents

Abstract

PURPOSE:To accurately measure ship speed stably regardless of the difference in water depth and the rapid change in ship speed by varying an averaging time constant corresponding to the ship speed. CONSTITUTION:Ultrasonic waves are transmitted slantly downward into the sea at a constant depression angle from a wave transmitter/receiver 1, reflection waves from the seabed or plankton within the sea are received and are supplied to a reception signal amplification circuit 4 as an electrical signal, its gain is controlled to a proper level according to depth data, and then the signal is supplied to a gate measurement circuit 5. A specific threshold is provided at the circuit 5 as a primary gate, a secondary gate which varies according to the signal pulse width of a ship speed/depth operation circuit 7 is provided, only the signal which passes the gates is input to Doppler frequency measurement circuit 6, and then the measured Doppler frequency is supplied to the circuit 7. The circuit 7 consecutively calculates the ship speed data with the obtained pulse width by auto-correlation method etc., and then inputs them to an automatic averaging circuit 8, performs averaging processing with a time constant corresponding to the ship speed, and then displays a measurement average ship speed on a display 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ship speed measuring device for transmitting and receiving ultrasonic waves from a moving ship to the seabed and measuring the Doppler frequency to measure the navigation speed of the ship.

[0002]

2. Description of the Related Art As is well known, a ship speed measuring device of this type transmits / receives ultrasonic waves to and from the seabed at a predetermined depression angle toward the seabed, measures the Doppler frequency, and measures the ship's own speed. Measuring the navigation speed. FIG. 3 is a block diagram showing the outline of the configuration of a conventional vessel speed measuring device of this type. In the figure, 1 is a transmitter / receiver for transmitting and receiving ultrasonic pulses to the seabed, 2 is a transmission circuit, and 3 is Transmission / reception switching circuit, 4
Is a received signal amplifier circuit, 6 is a Doppler frequency counter circuit, 7
Is a ship speed / depth calculation circuit, and 9 is an indicator. As shown in FIG. 3, in the conventional device, in order to obtain a stable reception signal, the gain of the reception signal amplification circuit 4 is controlled based on the water depth information measured by the ship speed / depth calculation circuit 7 so that the reception signal becomes the water depth. In order to be irrelevant, the signal is always amplified to a certain level and only the signal exceeding a predetermined threshold level is extracted (see FIG. 2 (b)).

[0003]

Since the conventional ship speed measuring device as described above is constructed and operates as described above, it has the following problems and cannot stably and accurately measure the ship speed. . That is, since the arrival time interval of the received signal is short at a shallow water depth, the transmission pulse width must be shortened, and therefore the front end and the rear end of the frequency where the frequency of the received signal is unstable compared to the stable central part of the frequency of the received signal. Will increase and the ship speed will become unstable. Therefore, it is necessary to perform sufficient averaging. On the other hand, when the water depth is deep, it is difficult to obtain a steep rectangular reception signal, and therefore it is necessary to obtain a reception signal using a gate that is relatively narrow with respect to the transmission pulse width. That is, in order to measure as accurately as possible, a device that can set a gate according to the water depth is required.

However, even such a device has a problem when the water depth is deep and the ship speed is high. That is, in this type of device, the ship speed is measured by the average value of the Doppler frequency for the pulse width of the received signal obtained through the gate, but the ship speed of a ship traveling at high speed suddenly changes. Then, since sufficient averaging is performed, tracking is slow and the measurement result is disturbed.

The present invention has been made in order to solve such a problem, and is capable of measuring the ship speed relatively stably and accurately, even when the ship speed is suddenly changed or the water depth varies. An object is to provide a speed measuring device.

[0006]

A vessel speed measuring device according to the present invention comprises means for varying an averaging time constant for obtaining a measured average value of vessel speeds in correspondence with the vessel speed. Further, it is characterized in that it is provided with means for varying an averaging time constant for obtaining a measured average value of the ship speed in accordance with the water depth.
Further, in addition to these means, a means for varying the gate width of the received signal according to the water depth is provided.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, 1 is a transducer for transmitting and receiving ultrasonic waves to the seabed, 2 is a transmission circuit, 3 is a transmission / reception switching circuit, and 4 is reception signal amplification. Circuit, 5 gate setting circuit, 6 Doppler frequency counting circuit, 7 ship speed / depth calculation circuit, 8 automatic averaging circuit,
Reference numeral 9 is a display.

Next, the operation will be described. Based on the transmission trigger generated by the ship speed / depth calculation circuit 7, the transmission circuit 2 amplifies the signal of the transmission frequency f ₀ by the transmission trigger width (see FIG. 2 (a)), and transmits it via the transmission / reception switching circuit 3. Is supplied to the transceiver 1. The transducer 1 is usually equipped on the bottom of a ship, and is set to transmit and receive ultrasonic waves at a predetermined depression angle in the bow or stern direction at a slanting downward angle in the sea. It is reflected by a plankton or the like in the sea, is received again by the wave transmitter / receiver 1, and is supplied as an electric signal to the reception signal amplification circuit 4 via the transmission / reception switching circuit 3. This electric signal is gain-controlled by the reception signal amplification circuit 4 based on the depth information from the ship speed / depth calculation circuit 7, amplified to an appropriate level, and then supplied to the gate setting circuit 5.

In the gate setting circuit 5, a predetermined threshold level is provided as a primary gate (FIGS. 2B and 2C).
In addition, a gate that varies according to the pulse width T of the transmission signal obtained from the ship speed / depth calculation circuit 7 is provided as a secondary gate (see FIG. 2 (d)).
Only the received signal that has passed through the next gate is input to the Doppler frequency measuring circuit, where the Doppler frequency is measured.
That is, in the gate circuit 5, a primary gate is applied to a signal exceeding the threshold level with respect to a reflected signal from the sea bottom, and further, based on the transmission pulse width T from the ship speed / depth calculation circuit 7, For example, from the rise of the primary gate to LOW to HIGH with a delay of t ₂ which is proportional to the ship speed,
Fast from the fall of the primary gate by t ₂ from HIGH to L
The secondary gate that becomes OW is set.

In the next Doppler frequency counting circuit 6, the Doppler frequency corresponding to the pulse width of only the portion passing through the above-mentioned primary and secondary gates is counted by the autocorrelation method, FFT method, zero-cross method, PLL method or the like. , And supplies the counting result to the ship speed / depth calculation circuit 7. And next ship speed / depth calculation circuit 7
Then, the obtained ship speed information for the pulse width is sequentially calculated based on the relational expression between the Doppler frequency and the ship speed, and is input to the automatic averaging circuit 8. From the ship speed information for the pulse width, the ship speed correspondence is obtained. The averaging process is performed with the time constant, and the measured average ship speed is input and displayed on the display 9 as the measured ship speed. That is, for the averaging process in the automatic averaging circuit 8, a moving average, a digital low-pass filter, etc. are used.
In this embodiment, the averaging time constant for obtaining the average value of the ship speed is made to correspond to the ship speed. For example, when the ship speed is 0.5 knots or less, 120 seconds, and when it is 1.0 knots or less. 90 seconds, 60 seconds if less than 1.5 knots, 1.5
If it exceeds the knot, the averaging process is performed with a time constant of 30 seconds.

That is, since it is generally difficult for a ship traveling at a low speed to rapidly change the ship speed, the averaging process can be performed by lengthening the averaging time constant. , A ship traveling at high speed may change the ship speed relatively rapidly. In this case, if the time constant is long, a sudden change in ship speed will also be included in the data for averaging processing, and this will disturb the measurement results, and in order to solve the problem that stable measurement cannot be performed, In the embodiment, the automatic averaging circuit 8 is provided so that stable measurement can be performed.

In the above embodiment, the averaging time constant is determined by the automatic averaging circuit 8 in correspondence with the ship speed. However, in general, a ship has a slow ship speed in a place where the water depth is shallow, and It is also possible to determine the sampling width according to the water depth by utilizing the characteristics that it is difficult to change the ship speed rapidly and the ship speed is fast at deep water and the ship speed can be changed rapidly. .

[0013]

As described above, the vessel speed measuring device according to the present invention appropriately changes the gate width of the reception signal in correspondence with the transmission pulse width corresponding to the water depth, thereby appropriately controlling the unstable region of the frequency component. By changing the averaging time constant of the data for obtaining the measured average value according to the ship speed, it is possible to provide a device that can be stably and accurately measured without being disturbed by sudden changes in ship speed. can get.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a waveform diagram for explaining the operation of the present invention.

FIG. 3 is a block diagram showing an example of a conventional device.

[Explanation of symbols]

 1 wave transmitter / receiver 2 transmission circuit 3 transmission / reception switching circuit 4 reception signal amplification circuit 5 gate setting circuit 6 Doppler frequency counting circuit 7 ship speed / depth calculation circuit 8 automatic averaging circuit 9 indicator

Claims (3)

[Claims] 1. A ship speed measurement in which an ultrasonic pulse of a predetermined width is transmitted and received from a moving ship to the seabed, the Doppler frequency from the received signal is measured and averaged, and the measured average value is used as the ship speed of the ship. A vessel speed measuring apparatus, characterized in that the apparatus comprises means for varying an averaging time constant for obtaining a measured average value of the vessel speed in correspondence with the vessel speed. 2. A vessel speed measuring device for transmitting and receiving ultrasonic pulses of a predetermined width from a moving vessel to the seabed, measuring and averaging the Doppler frequency of the received signal, and using the measured average value as the ship's speed. In the vessel speed measuring device, a means for varying an averaging time constant for obtaining a measured average value of the vessel speed in accordance with the water depth. 3. A means for obtaining a reception pulse width required for measurement through a gate whose gate width is variable corresponding to a transmission pulse width which changes in relation to water depth. Alternatively, the ship speed measuring device according to the second item.