JPH0778537B2 - Berth speedometer - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a berth speedometer used in a berth assist system of a large ship.

(Prior Art) In order to berth a relatively large vessel such as a tanker for ocean voyage, as shown in FIG. 8, the vessel 100 is stopped parallel to the wharf 200 several hundred meters offshore and the bow of the vessel is The two boats, one near the stern and one near the stern, are propelled at a constant speed by collaborative work with the two tugs 101 and 102, so that control is performed so that the berth is slowly approached while maintaining the parallel state with the quay.
At this time, the berthing speed of the ship is measured one by one on the quay side, and feedback control is notified to the tugboat side.
In the present specification, the approaching motion of the ship toward the quay is referred to as “berthing”.

Conventionally, an ultrasonic radar has been used as the above-mentioned berthing speed meter. That is, as shown in FIG. 8, the ultrasonic radars 201 and 202 are installed in the seawater on the quay side. Each ultrasonic radar consists of a pair of ultrasonic radiator and receiver.The ultrasonic wave emitted from the radiator propagates in the sea and is reflected by the side of the ship below the waterline, and propagates in the sea again to propagate the ultrasonic radar. It returns to and is received by the receiver. The distance between the quay and the ship is measured from this round-trip travel time and a constant propagation speed, and the berthing speed is measured from the time change rate of this measured distance. This berthing speed is measured independently for at least two locations on the ship, as illustrated in FIG. 8, for the purpose of maintaining the parallel state with the quay.

For further details of such a berth speed meter using ultrasonic waves, refer to the specification of JP-A-52-86353, which is entitled "Vessel berth guidance device," as necessary.

(Problems to be Solved by the Invention) The above-mentioned conventional berthing speed meter utilizing ultrasonic waves utilizes the property that ultrasonic waves travel straight at a constant propagation speed in the sea. However, with this method, it is affected by various obstacles such as fish in the sea, debris, bubbles, and ultrasonic waves emitted may pass through the bottom of the hull depending on weather conditions such as waves and tide levels. There is a problem in terms of reliability.

Setting the propagation path of this ultrasonic wave in the air rather than in the sea is difficult in that the amount of attenuation during propagation becomes excessive and the propagation path is curved due to the influence of wind.

Further, in this ultrasonic radar, since the wavelength of the ultrasonic waves is sufficiently larger than the unevenness of the surface of the ship that reflects the ultrasonic waves, the ultrasonic waves that collide with the ship will undergo regular reflection such that the incident angle and the reflection angle are equal. receive. For this reason, as illustrated in FIG. 9, as the parallel relationship between the ship and the quay collapses during berthing, the ultrasonic waves reflected on the side of the ship are received by the receiver installed in pairs with the radiator. There is also a problem that it disappears and measurement becomes impossible.

On the other hand, referring to the specification of Japanese Patent Application Laid-Open No. 54-51793, which is entitled "Navigation Assistance Device", a method of using a radio wave detector whose propagation path is in seawater or air can be considered. However, according to the consideration of the present inventor, this radio wave detector has the following drawbacks.

First, there is a problem that a large facility such as an antenna is required, which increases the establishment cost, and a large amount of electric power is required, which also increases the operation cost.

Further, in this radio wave detector, similarly to the case of the ultrasonic radar, since the emitted radio wave is regularly reflected on the side of the ship, there is a problem that measurement becomes impossible if the parallelism between the ship and the quay collapses to some extent.

Further, this radio wave detector has a problem that it is difficult to independently measure the berthing speed at a plurality of locations of the ship because the radio wave has a large wavelength and the resolution is not sufficient.

In addition, the radio wave detector causes a problem of electromagnetic compatibility with peripheral systems, such as inducing interference in a nearby communication facility.

(Means for Solving the Problem) A berth speedometer according to the present invention includes a first oscillating portion that generates a drive pulse repeated in a first cycle and a second cycle that is slightly larger than the first cycle. A second oscillating unit that generates repeated sampling pulses, a light emitting unit that emits a laser beam pulse to the ship approaching the quay in synchronization with the drive pulse, and a laser beam reflected by the ship. And a light receiving section for receiving the pulse and converting it into an electric signal and outputting the electric signal.

The berth speedometer of the present invention further includes a sample-and-hold unit that holds the electric signal output from the light-receiving unit in synchronization with the sampling pulse and outputs the received laser beam pulse while extending the time axis. , This sample
A distance calculation unit that calculates the distance to the ship by detecting the propagation delay time from the laser beam pulse emission time to the light reception time based on the output of the hold unit, and the berthing speed of the ship from the time change rate of this calculated distance And a berth speed calculation unit for calculating

Furthermore, the berth speedometer of the present invention is a phase lock that controls one of the oscillation frequencies of the first and second oscillating units so that the frequency difference between the drive pulse and the sampling pulse is 1 / integral of one frequency. By providing a loop, the stability of a slightly different frequency difference is ensured and the detection accuracy is improved.

(Operation) It is assumed that the sampling timing for the received pulse signal is sequentially shifted by Δτ due to a slight difference in frequency (frequency) between the drive pulse and the sampling pulse. If the width of the received pulse is W (sec), the number of times that a non-zero sample value is obtained for this received pulse is W / δτ times. Then, each non-zero sampling value is held for a sampling period τ (sec), so that τ (se
It is extended at the time of c). As a result, the width of the received pulse after sample hold is τ (sec / time) × W / δτ (time) =
(Τ / δτ) W (sec). Therefore, the width of the pulse signal output from the sample and hold unit is [(τ / δτ) W] / W = τ / δτ = (τ ₀ + δτ) / δτ ≈τ ₀ / δτ ... (1) It will be extended by a factor of 3. In this way, by extending the width of the received pulse signal on the time axis, the output time of the received pulse signal can be detected with high accuracy. Hereinafter, the present invention will be described in more detail with reference to Examples.

(Embodiment) FIG. 1 is a block diagram showing the configuration of a berthing speed meter according to an embodiment of the present invention.

In the figure, 10 is a main oscillator, 11 is a frequency divider, 12 and 15 are amplifiers, 13 is a light emitting section, 14 is a light receiving section, 16 and 18 are sample and hold circuits, 17 is a binarization circuit, and 20 is a sub oscillator. , 21 and 23 are frequency dividers, 22 is a mixer, 24 is a phase comparator, 25 is a low-pass filter, 30 is a CPU, 31 and memory, and 32 is a memory controller.

The main oscillator 10 is mainly composed of a stable crystal oscillator, and generates a pulse train having an oscillation frequency Fo. This pulse train is decimated to 1 / N in the frequency divider 11, becomes a drive pulse having a constant repetition frequency fo (= Fo / N), and is supplied to the light emitting unit 13 via the amplifier 12. The light emitting unit 13 is composed of a laser diode (LD) and an LD drive circuit for driving the laser diode, drives the laser diode in synchronization with the drive pulse supplied from the amplifier 12, and has a period τo (= 1 / f
At step o), a pulsed laser beam is emitted. The light emitting unit 13 is installed at a predetermined position on the sea surface such as on the quay, and emits a pulsed laser beam in front of the quay and in a direction orthogonal to the quay.

The pulsed laser beam emitted from the light emitting unit 13 is propelled by the tugboat, reflected by the bow of the ship on the shore or near the stern, and enters the light receiving unit 14. Light receiving section
14 is mainly composed of an avalanche photodiode (APD), and outputs an electric signal having an amplitude according to the amount of received light. Therefore, each time the reflected component of the pulsed laser beam is received, a pulsed electric signal is output from the light receiving unit 14. The pulsed electric signal is amplified in the amplifier 15 while being subjected to amplitude limitation so that the peak value becomes a predetermined value, and then is supplied to the sample and hold circuit 16. This sample and hold circuit 16 includes a sub oscillator 20
The pulse train generated in 1 is frequency-divided by the frequency divider 21 to be supplied as a sampling pulse having a period τ. The pulse-shaped electric signal output from the amplifier 15 in synchronization with this sampling pulse is held in the sample-hold circuit 16.

The output of the sample and hold circuit 16 is binarized by being compared with a predetermined threshold value in the binarization circuit. That is, if the output of the sample and hold circuit 16 does not reach the above threshold value, the binary signal "0" is output from the binarization circuit 17, and if the output of the sample and hold circuit 16 is above the above threshold value, it is binarized. The binary signal "1" is output from the circuit 17.
The output of the binarization circuit 17 is written in the memory 31 under the control of the memory controller 32. The drive pulse output from the amplifier 12 is held in the sample / hold circuit 18 in synchronization with the sampling pulse and supplied to the memory controller 32. The memory controller 32 is
Every time a signal is held in the sample and hold circuit 18, the output of the binarization circuit 17 is written into the memory 31 while advancing the address counter. Therefore, the CPU 30 detects the address at which the write data changes from continuous “0” to continuous “1” by accessing the memory 31 while advancing the address and radiating from this address value. The time difference between the pulse and the received pulse, that is, the propagation delay time can be detected.

The CPU 30 calculates the distance to the ship under berth from the propagation delay time and the speed of light, and calculates the berthing speed of the ship from the time change speed (rate of change) of this distance. The CPU 30 displays the calculated berthing speed on a display device (not shown), or automatically sends it from a transmitter (not shown) to a ship on berth or a tugboat on berth.

The two berth speedometers of FIG. 1 are typically installed on the quay 200 at a predetermined distance, as illustrated by reference numerals 1 and 2 in FIG. The light emitting portions of the berth speedometers 1 and 2 emit laser beams to the boat side near the bow and the boat side near the stern of the ship 100, which is propelled by the tugs 101 and 102 and berths substantially parallel to the quay 200. Since the surface of the side of the ship that reflects the emitted laser beam has a rough surface having irregularities sufficiently larger than the wavelength of the laser beam, the incident laser beam is isotropically scattered by this rough surface. That is, as illustrated in FIG. 2, when the incident surface of the laser beam is represented by an incident point,
A reflected beam having a spherical directivity is emitted from this incident point.

Therefore, as illustrated in FIG. 3, even if the parallelism between the ship 100 and the quay 200 while docking is broken, the directivity of the reflected laser beam is so wide that the light receiving sensitivity of the light receiving section is insufficient, and detection becomes impossible. There is no such thing. Due to this wide directivity, the berth speed meter 1
The reflected waves of the laser beam emitted from each of No. 2 and No. 2 also reach the light receiving unit of the other party. However, it is possible to easily avoid mutual interference due to reception of reflected waves of the other party by giving the light receiving section of each berth speed meter an appropriate directivity.

The berth speed meter shown in FIG. 1 uses a laser beam having a propagation speed that is orders of magnitude higher than that of ultrasonic waves. For this reason, the propagation delay time of the reflected wave becomes orders of magnitude shorter than that of the ultrasonic wave, and it becomes difficult to measure the propagation delay time with high accuracy by an ordinary method. In addition, this berth speed meter uses a laser beam with a wavelength that is orders of magnitude shorter than radio waves. For this reason, a radar that uses radio waves cannot adopt a method of measuring the propagation delay time of a reflected wave from the amplitude difference and phase difference of the effective transmitted and received modulated waves.

Therefore, in the berthing speed meter shown in FIG. 1, the required measurement accuracy is secured by using the following sampling method.

That is, referring to the waveform diagram of FIG. 4, the laser beam pulse is repeatedly emitted with a constant period τo, as shown in FIG. As a result, as illustrated in FIG. 6B, the reflected laser beam pulse is received with a delay of propagation delay time τd from the emission time point of each laser beam pulse. However, if the berthing speed of the ship is v and the distance to the ship is r, by increasing the repetition frequency fo (= 1 / τo) of the laser beam pulse by an order of magnitude greater than the assumed value of v / r. , Are set so that the propagation delay times τd detected each time are equal. In order to detect this delay time τd with high accuracy, it is necessary to detect the received pulse waveform with high accuracy. Therefore, as illustrated in FIG. 4 (C),
A sampling pulse having a period .tau. slightly larger than .tau.o is supplied from the frequency divider 21, and the received pulse output from the amplifier 15 is held in the sample and hold circuit 16 in synchronization with this sampling pulse.

Assuming that the difference between the sampling pulse period τ and the laser beam pulse period τo is δτ, it is clear from the comparison between (A) and (C) in FIG. 4 that the first sampling pulse is the laser beam.・ Although it occurs at the same time as the pulse, from the next time onward, it will be delayed by δτ from the laser beam pulse. Therefore, paying attention to the relative relationship on the time axis between this sampling pulse and the reception pulse illustrated in (B), the latter is sampled and held by the former at a time interval of δτ. Since the sampling and holding are performed in the period of τ, the time axis of the received pulse waveform output from the sample and hold circuit 16 is as described above by the equation (1), as will be understood by referring to (D). Will be expanded by the magnification given by.

In the example shown in FIG. 4 (D), δτ is too large compared to the width of the original reflected pulse, so that the waveform whose time axis is enlarged is a rough waveform. In practice, a sufficiently smooth time-axis expanded waveform can be obtained by setting δτ to a value that is sufficiently smaller than the width of the original reflected pulse.

The value τo / δτ of the equation (1) is also the total number of laser beam pulses emitted for one distance measurement. If the total number of radiations required for this one-time distance measurement is Σn, then Σn ≈ τo / δτ (2) In order to realize time extension by such a sampling method, the main oscillator 10 and sub The oscillation frequency of the oscillator 20 is determined based on the following consideration.

That is, first, the measurable range (the longest measurable distance) of this berth speed meter is R meters (m), and the speed of light is C
(M / s), the propagation delay time τmax (s) of the laser beam pulse reflected and received from the ship located at the farthest distance R is τmax = 2R / C (s) ...... ( 3)

Therefore, in order to secure the measurable range of R (m),
It is necessary to set the period τo of the light emission pulse for driving the light emitting unit 13 to be τmax or more in the equation (1). Here, τo = τmax = 2R / C (s) (4) is set.

The repetition frequency fo of the light emission pulse is fo = 1 / τo = C / 2R (1 / s) (5).

If the frequency division ratio of the frequency divider 11 is N, the oscillation frequency Fo of the main oscillator 10 becomes Fo = Nfo = NC / 2R (1 / s) (6).

On the other hand, if the distance measurement resolution is set to δR (m), the propagation delay time measurement resolution δτ based on this is δτ = 2δR / C (s) (7).

Therefore, the period τ of the sampling pulse output from the frequency divider 21 may be set to τ = τo + δτ = (2R + 2δR) / C (s) (8). The repetition frequency f of the sampling pulse is f = 1 / τ = C / (2R + 2δR) (1 / s) (9).

Here, if the frequency division ratio of the frequency divider 21 is set to the same value N as the frequency division ratio of the frequency divider 11, the oscillation frequency F of the sub oscillator 20 is F = Nf = NC / (2R + 2δR) (1 / s)… (10)

From equations (6) and (10), δF = Fo−F = NCδR / [2R (R + δR)] ≈NCδR / (2R ² ) ... (11) Equations (6), (11) and (7) From equations (8) and (8), δF / F _o ≈ [NCδR / (2R ² )] / [NC / (2R)] = δR / R = [Cδτ / 2] / [C (τ-δτ) / 2] = δτ / (τ-δτ) = δτ / τ ₀ (12) Here, the measurable range R is 750 m and the measurement resolution δR is 1 cm.
If (0.01m), δF / Fo = 1.333 × 10 ^-5 (13) is obtained from Eq. (10).

It is extremely difficult to hold such a minute difference in oscillation frequency in the main oscillator 10 and the sub oscillator 20 that operate independently of each other. Therefore, as shown in FIG.
By configuring the sub-oscillator 20 with a voltage controlled oscillator (VCO) and configuring a phase-locked loop including a mixer 22, a frequency divider 23, a phase comparator 24, and a low-pass filter 25,
The oscillation frequency F of the sub oscillator 20 is made to follow the value lower than the oscillation frequency Fo of the main oscillator 10 by δF. This δF is given by δF = Fo / MN (14), where M is the frequency division ratio of the frequency divider 23.

Hereinafter, a specific method of setting a numerical value based on the above consideration will be described.

First, 750 m is set as the measurable range R. From this measurable range R and the equation (4), 5.00 μs (microsecond) is obtained as the radiation period τo of the laser beam. This is 200k
It corresponds to the repetition frequency fo of Hz. Next, the distance measurement value is obtained at a rate of 5 times per second. Accordingly, the time required for one measurement is 200 ms (millisecond). Therefore, 1
Total number of laser pulse beams emitted for each measurement Σ
n is Σn = 200 kHz × 200 ms = 4 × 10 ⁴ . This Σn is equal to τo / δτ from equation (2), which is also equal to R / δR from equation (12).

Therefore, the measurement resolution δR is 750 m / (4 × 10 ⁴ ) = 1.87
Get 5 cm. Further, if the frequency division ratio N is 750, from the formula (6), the oscillation frequency Fo of the main oscillator 10 is 750 × 200 kH
Get z = 150MHz. From equation (12), δF = 150MHz /
(4 × 10 ⁴ ) = 3.75 KHz is obtained.

FIG. 5 shows an example of four numerical values set by trial and error in this way.

FIG. 6 is a circuit diagram showing an example of the configuration of the light receiving section 14 of FIG.

The light receiving unit 14 includes an avalanche photo diode APD that receives a reflected laser beam pulse from a ship, a load resistor r that is connected in series to the avalanche photo diode, and the connection point is connected to an output terminal O in series. It is composed of a resistor R and a constant voltage source BT for applying a constant voltage to a series connection circuit of the avalanche photo diode and the resistors r and R.

Since the avalanche photodiode has a carrier multiplication function inside, the avalanche photodiode has an advantage that the light receiving sensitivity is extremely higher than that of a normal photodiode and the post-amplifier in the subsequent stage can be omitted. Further, as shown in FIG. 7, the avalanche photodiode has a multiplication factor that increases as the amount of incident light decreases. Therefore, even if the amount of incident light changes, the output current does not change so much. Has output characteristics. On the other hand, the avalanche photodiode has a problem in that the multiplication factor changes significantly according to changes in various operating environments such as the applied voltage and the ambient temperature, and the operation of the light receiving section tends to be unstable.

Therefore, in the light receiving section shown in FIG. 6, the resistance value of the series resistor R is set to a value sufficiently larger than the internal resistance value of the avalanche photo diode APD and the resistance value of the load resistor r. -The operation is stabilized by keeping the current flowing in the diode almost constant.

(Effects of the Invention) As described in detail above, the berth speedometer of the present invention detects the time from the emission time point of the laser beam pulse to the light reception time point with high accuracy by using the sampling method, and reaches the ship. Is different from the conventional radar that uses ultrasonic waves or radio waves, it has a high reliability and accuracy. The effect that economical measurement can be realized is exhibited.

[Brief description of drawings]

FIG. 1 is a block diagram showing the structure of a berth speedometer according to an embodiment of the present invention, and FIGS. 2 and 3 are plan views for explaining the usage of the berth speedometer of the above embodiment. FIG. 5 is a waveform diagram for explaining the operation of the berth speedometer of the above embodiment, FIG. 5 is a conceptual diagram showing an example of setting items related to the operation of the berth speedometer of the above embodiment, and FIG. 6 is of FIG. FIG. 7 is a circuit diagram showing an example of the structure of the light receiving portion, FIG. 7 is a characteristic diagram for explaining the input / output characteristics of the avalanche photodiode shown in FIG. 6 while comparing them with those of an ordinary photodiode, and FIG. FIG. 9 and FIG. 9 are plan views for explaining the use situation and problems of the conventional berth speedometer by the ultrasonic radar. 1,2 shore speedometer, 10 ...... main oscillator, 11,21 ...... divider, 12,15 …… amplifier, 13 …… light emitting part, 14 …… light receiving part, 16,18 …… sample ・Hold circuit, 17 …… Binarization circuit, 20 …… Sub oscillator, 30 …… CPU, 31 …… Memory, 3
2 …… Memory controller, 100 …… Ship docking, 101,
102 …… Tugboat, 200 …… Quay.

Claims (3)

[Claims] 1. A first oscillator for generating a drive pulse repeated in a first cycle, and a second oscillator for generating a sampling pulse repeated in a second cycle slightly larger than the first cycle. And a phase-locked loop that controls one of the oscillation frequencies of the first and second oscillating units so that the frequency difference between the drive pulse and the sampling pulse is an integer fraction of one frequency. A light emitting unit that emits a laser beam pulse in synchronization with the drive pulse with respect to the ship on berth, and a light receiving unit that receives the laser beam pulse reflected by the ship, converts it into an electric signal, and outputs the electric signal. Corresponding to an extension of the time axis of the received laser beam pulse by holding the electric signal output from the light receiving section a plurality of times in synchronization with the sampling pulse. A sample-and-hold section that outputs an electric signal to detect the time difference from the emission point to the reception point of the laser beam pulse based on the electric signal output from the sample-and-hold section to calculate the distance to the ship. And a berth speed calculator for calculating the berth speed of the ship from the calculated time change rate of the distance. 2. The distance calculating section is a binarization circuit for binarizing and outputting the output of the sample and hold section, a memory, and a write address of the memory in synchronization with the drive pulse. However, the memory controller that writes the output of the binary circuit to this stepped address, and the address where the write data of this memory has changed are detected, and based on this detected address, from the emission time to the light reception time. The berth speedometer according to claim 1, further comprising a CPU that detects a time difference between the berthing speed and the shore speed. 3. The phase-locked loop, a mixer for generating and outputting beat signals of the drive pulse and the sampling pulse, a divider for dividing one of the drive pulse and the sampling pulse, the mixer and the divider 2. A phase comparison circuit for controlling the oscillation frequencies of the first and second oscillating units so that the phase difference between the pulses output from each of the detectors is equalized. Alternatively, the berth speedometer described in item 2.