JPH0371671B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention measures the speed, etc. of a ship attempting to berth using ultrasonic waves, notifies the ship, and assists the ship to appropriately slow down and berth. This paper relates to a noise evaluation method for an ultrasonic measurement system in a system.

[Prior Art] In this type of berthing support system, the berthing speed of a ship is generally determined using an ultrasonic range finder.
The distance is detected at a predetermined sampling period, and the distance is measured based on the change in this distance over time.

The ultrasonic range finder is configured to measure the time interval between the transmission of a pulsed transmission wave and the reception of a reflected wave from a detection target, and obtain target information from this time information. This type of measuring instrument often receives noise caused by obstacles, density changes in the medium, multiple reflections, etc. before and after the original received wave.

As an example, a signal waveform received by an ultrasonic range finder is shown in FIG. 9a. In the same figure,
The waveform indicates the transmission leakage signal, , indicates the noise signal, and indicates the reflected echo signal from the measurement object targeted by the ultrasonic range finder.
indicates the multiple reflection echo.

As shown in the figure, if a noise signal exists before the target reflected echo signal, the ultrasonic range finder misidentifies the noise signal as the target reflected echo signal and makes an erroneous measurement.

To prevent such erroneous measurements, the ultrasonic range finder captures the desired reflected echo signal at the initial point of measurement and then removes the noise signal, as shown in Figure 9b above. A mask gate may be applied using a transmission mask signal.

This mask gate opens just before the expected reception of the desired reflected echo signal, and operates to enable subsequent signal components to be received. Figure 9c
shows the signal waveform obtained in this case.

In addition, this mask signal opens the mask gate only at the predicted arrival time of the desired reflected echo signal.
It may then be set to close again.
This example is shown in dashed lines in Figure 9b. In this case, the signal shown in c in the figure disappears.

The mask signal described above is controlled to move in synchronization with the movement (movement of arrival time) of the target reflected echo signal, so it is called a tracking gate and always detects the arrival of the target reflected echo signal. It is controlled to open just before.

In measuring instruments such as ultrasonic range finders, only the noise that exists before the target reflected echo signal causes erroneous measurements, so a mask gate is applied using a mask signal as shown in Figure 9b above. As a result, a signal waveform as shown in FIG.

The circuit shown in FIG. 8 is a conventional noise removal circuit for measuring instruments having such a function. This noise removal circuit includes an amplifier 1 that amplifies an input signal,
a mask signal generation circuit 2 that forms a mask signal;
The analog switch 3 is configured to open and close using the mask signal as a control signal. This analog switch 3 is opened during the mask signal generation period when the mask signal shown in FIG. 9b is at a high level, and blocks the output of the input signal.

[Problems to be Solved by the Invention] As mentioned above, conventional noise removal circuits can be expected to have some effect on noise removal, but depending on the measurement state, they may have the following problems. Ta.

That is, due to a sudden displacement of the measurement target, etc., the reflected echo signal shown as a waveform in FIG. If this happens, the output signal waveform will be 0, as shown in FIG. In addition to this, there is also the problem of capturing multiple echo signals or the next noise signal, resulting in erroneous measurements.

In order to avoid such inconveniences, conventional ultrasonic rangefinders using mask signals open the mask gate fully at regular intervals or after a certain number of measurements, as shown in Figure 9f. However, it has always been necessary to check whether the desired reflected echo signal is being captured. Of course, when this mask gate is fully opened, it is controlled so as not to pass any transmission leakage signals.

However, if the mask gate is fully opened, a contradiction arises in that there is a possibility that noise present before the reflected echo signal will be captured.

Furthermore, even when the mask gate is set, there is a problem in that erroneous measurements occur due to the nozzle entering just before the reflected echo signal.

On the other hand, the inventor has found that the above-mentioned problems can be solved by slicing the input signal waveform at an appropriate level and removing signals whose peak values do not exceed this level as noise. . In this case, the problem is how to set the level at which the input signal waveform is sliced. That is, it is necessary to evaluate the level of input noise at various miscellaneous levels.

The present invention makes it possible to evaluate the level of the input nozzle each time a measurement is made, and to utilize the evaluation for the next measurement, making it possible to remove or reduce the noise that exists before the target reflected echo signal. It is an object of the present invention to provide a noise evaluation method for a berthing support system that improves the S/N of a measuring instrument and makes it possible to prevent erroneous measurements even when the mask gate is fully open.

[Means for Solving the Problems] The present invention provides a system that measures the distance from a quay of a ship attempting to berth using ultrasonic waves, notifies the ship, and assists the ship to appropriately decelerate and berth. This is a noise evaluation method for ultrasonic measurement systems, and as a means to solve the above problems, as shown in Figure 1, the distance from the quay to the ship is calculated from the previous measurement values, and the calculated distance is a distance/speed calculating means for calculating the speed of the ship from the above-mentioned calculated speed, the measurement period and the above-mentioned calculated distance; Received wave predicted arrival time area calculating means for calculating a received wave predicted arrival time area after transmission of the transmitted wave at the time of measurement; noise level determination gate setting means for setting a time domain for noise level determination, and setting a gate that allows a noise level determination result to be output only within the noise level determination time domain; and a peak value of a received input signal is set in advance. The apparatus is characterized in that it comprises a noise level determination means that outputs a high noise level determination signal when there is an input signal whose peak value exceeds the reference value when compared with a reference value.

Each means of the present invention is constituted by a microcomputer, and is connected to a front end including a transmitting circuit, a receiving circuit, a noise removal circuit, a time measuring circuit, a timing signal generating circuit, and the like. In addition, the microcomputer constituting the present invention calculates the distance from the quay to the ship based on the previous measurement value based on the ultrasonic round trip time measured in the time measurement circuit, and also calculates the distance from the quay to the ship using the calculated distance and ultrasonic transmission. It has a data processing function to calculate the speed of the ship from the period, and this function is the same as the distance/speed calculation means of the present invention. The present invention actually uses the calculation result of the data processing function as the calculation result of the distance/speed calculation means.

Further, in the present invention, the predicted received wave arrival time area calculated by the received wave predicted arrival time area calculation means may be the same as the tracking gate of the received wave, and when the support system is provided with tracking gate setting means. , this means can be used as received wave predicted arrival time domain calculation means.

In the present invention, preferably, the noise level determination gate setting means sets a time domain necessary for preventing erroneous reception due to transmission contamination in the transmission system, such as transmission leakage or transmission reverberation, as a transmission mask gate.
This makes it possible to output the noise level determination result after the transmission mask gate ends.

[Operation] In the problem solving means of the present invention, the noise level judgment time domain is set after the transmission of the transmitted wave and before the predicted arrival time domain of the received wave, so that the noise that is input before the arrival of the original received signal is Assess the level of

In addition, evaluation is performed by monitoring whether or not there is a signal whose peak value exceeds the reference value among the signals input within the noise level judgment time domain, and if there is an input signal whose peak value exceeds the reference value. By outputting a high noise level determination signal, it is determined whether or not the input signal contains noise whose peak value exceeds a certain level.

Through this evaluation, it is possible to set the level at which the input signal waveform should be sliced at the time of the next measurement, and it becomes possible to reliably remove or reduce the noise waveform having a relatively high level peak value. Alternatively, the same effect can be obtained by changing the slice level relative to the noise waveform by amplifying the input signal with an amplification factor corresponding to the above evaluation using a variable gain amplifier or the like without changing the slice level. I can do it.

In this way, by repeatedly evaluating the nozzle level and correspondingly changing the input signal waveform slice level, it is possible to eliminate most of the noise, except for high-level noise that occurs extremely rarely in the environment in which the instrument is used. noise is removed.

[Example] An example of the present invention will be described with reference to the drawings.

<Configuration of First Example> FIGS. 2A to 2C show the configuration of a first example of the noise evaluation method of the present invention.

The noise evaluation method shown in the figure includes a microcomputer 31 that functions as a distance/velocity calculation means, a received wave predicted arrival time area setting means, and a level judgment means that functions as a noise level judgment means and a gate setting means for noise level judgment. The circuit 36 is configured to include a circuit 36.

The microcomputer 31 includes a microprocessor 32, a memory 33, and an I/O port 34.
and a bus 35 that connects these.
The I/O port 34 includes the level determination circuit 36.
, a time measuring circuit 60 that measures the round trip time of the ultrasonic waves from the received signal, and a timing signal generating circuit 70 that outputs a transmission pulse, a transmission mask gate signal, and a clock pulse.

As shown in FIG. 2C, the level determination circuit 36 includes a comparator 37, a noise level determination gate 38, and a flip-flop circuit 39 for holding the determination result. The determination result of this level determination circuit 36 is determined by the gain control signal generation circuit 4.
It is input to 0.

The comparator 37 is composed of, for example, an operational amplifier, and has an inverting input terminal connected to a reference voltage source _ER . This comparator 37 compares the output voltage of the variable gain amplifier 10 that amplifies the received input voltage with the reference voltage E _r of the reference voltage source E _R . That is, the nozzle level determination means compares the peak value of the received input signal with a preset reference value E _r and outputs a high noise level determination signal if there is an input signal whose peak value exceeds the reference value E _r . functions as

The noise level determination gate 38 includes, for example, AND gate circuits 38a and 38b. The AND gate circuit 38a includes a tracking gate signal as a signal for setting the predicted arrival time region of the received wave;
A transmission mask gate signal is input. Further, the AND gate circuit 38b receives the noise level judgment gate signal and the output signal of the comparator 37, and is capable of outputting the output signal of the comparator 37 only when the noise level judgment gate signal is at a high level. do. That is, the noise level determination gate 38 functions as noise level determination gate setting means by these gate circuits. However, the AND gate circuits 38a and 38b
Of course, it can be constructed from one AND gate circuit or from a logic gate circuit.

The flip-flop circuit 39 is set by this high noise level determination signal and holds the logical product.

<Operation of First Embodiment> The operation of this embodiment configured as described above will be explained by taking as an example the case where the circuit of this embodiment is applied to the noise removal circuit shown in FIG. 2B.

Prior to explaining the operation, the configuration of the noise removal circuit shown in FIG. 2B will be explained.

The noise removal circuit shown in the figure is applied to an ultrasonic range finder of a berthing support system, and includes a variable gain amplifier 10, a signal level slice circuit 20,
It is configured to include a noise evaluation circuit 30 to which the noise evaluation method of this embodiment is applied, a gain control signal generation circuit 40, and an amplifier 50.

The variable gain amplifier 10 is composed of, for example, an operational amplifier, and amplifies the input signal with an amplification gain specified by a gain control signal from a gain control signal generation circuit 40, which will be described later. In this embodiment, this input signal is a burst wave received by an ultrasonic receiver (not shown). However, it may also be a pulse signal obtained by detecting this.

As shown in FIG. 3, the signal level slicing circuit 20 includes resistors R ₁ and R ₂ forming an input circuit;
A resistor R ₃ forming a feedback circuit is connected to an inverting input terminal to form an adder, and an operational amplifier 21 is provided, and an output voltage below the zero line is cut off at the output side of the operational amplifier 21. A diode D is provided. The operational amplifier 21 includes:
The output of the variable gain amplifier 10 is input as an input signal via a resistor _R1 . Further, a bias voltage +E _b from a bias power supply E _B for raising the zero line of the output voltage to a slice level is input via a resistor R ₂ .

The gain control signal generation circuit 40 has a gain setting/changing function for setting a standard gain for the variable gain amplifier 10 and changing the standard gain in response to the high noise level determination signal. It has the function of converting the gain into an analog gain control signal.

Next, the operation of the first embodiment of the noise removal circuit configured as described above will be explained with reference to the above figures and FIGS. 4A and 4B.

In FIG. 3, the received input signal amplified by the variable gain amplifier 10 is sent to a signal level slice circuit 20 and a noise evaluation circuit 30. This input signal typically includes:
It includes a reflected echo signal, a preceding noise signal, and multiple reflected echo and noise signals.

Further, in the figure, the waveform is a transmission pulse, but it is shown for convenience of explanation and is not included in the actual received input signal, and its leakage is also removed by the transmission mask gate.

Although this transmission mask gate is not shown in this embodiment, for example, the amplifier 10 shown in FIG.
It can be configured by providing a gate circuit at the front stage. The opening and closing of the mask gate is set by a transmission mask signal that is triggered by a transmission command pulse, as shown in FIG. Prevents erroneous measurements.

In addition, as mentioned in the conventional example above, the ultrasonic distance measuring device using this noise removal circuit has the following functions: A mask gate is set. This mask gate is especially called a tracking gate because it changes the opening position of the gate by tracking the movement of the receiving position of the target reflected echo signal on the time axis. .

In this embodiment, the tracking gate is set by calculating the received wave predicted arrival time domain, as described above, and outputting the setting signal from the microcomputer 31 as the tracking gate signal.

The calculation of the predicted arrival time region of the received wave and the output of the tracking gate signal based on the calculation are performed by the microcomputer 31, for example, according to the flowchart shown in FIG.

The microprocessor 32 first stores the memory 33
The previous measured value (required time for ultrasonic round trip) stored in is read out, and the distance to the target ship is calculated from the measured value and the underwater sound speed (step 1).
In the memory 33, the microprocessor 32 stores the measurement values sent from the time measurement circuit 60 in a preset area. At that time, the previous measured value is updated with the new measured value.

Note that in this embodiment, the previous value is used as the measured value, but a moving average value for a plurality of measurements may be calculated and this moving average value may be used as the measured value for the above calculation.

Next, the microprocessor 32 stores the calculated distance value in a specific area of the memory 33. Thereafter, the speed of the ship is calculated from the distance and the ultrasonic transmission period (stored in advance as a constant in the memory 33 or in the program) (step 2).

The microprocessor 32 calculates a predicted moving distance of the ship from the above-mentioned calculated speed and the above-mentioned transmission cycle, and calculates a predicted travel distance (between the ship and (distance to the quay) is calculated (Step 3).

Furthermore, the round-trip time required for the ultrasonic waves at the time of the next measurement is determined by using this calculation result and the sound speed, and the received wave predicted arrival time region is set in this time, taking into account a preset tolerance width (step 4). ). This received wave predicted arrival time region serves as a tracking gate in this embodiment. The numerical value of this tracking gate is stored in a preset area of the memory 33. In this embodiment, the set value of this gate is set as a target value by a numerical value corresponding to the measured value n of the counter set by a program described later.

The above processing is performed after the previous measurement is completed. Thereafter, when the transmission command pulse is input, the microprocessor 32 resets a register (not shown) that constitutes a counter. Next, it is checked based on the set value of the register whether or not n has reached the target value (step 5). If the target value has not been reached,
The calculation n=n+1 is executed and a new value of n is set in the register (step 6). and,
Returning to step 5 above, the same operation is repeated until n reaches the target value.

When n reaches the target value, the microprocessor 32 outputs a tracking gate signal (step 7).

In this embodiment, the tracking gate that is opened and closed by the tracking gate signal is set by providing a gate circuit after the amplifier 50, although not shown.

Therefore, in the ultrasonic range finder to which this embodiment is applied, the above-mentioned tracking gate normally operates, so that the noise signal input just before receiving the reflected echo signal is blocked. Therefore, below,
A case in which the tracking gate is in an open state will be explained.

Signal level slicing circuit 2 to which the input signal is sent
0 is a circuit that functions to subtract a certain level of voltage from an input signal and output it. That is, noise is removed by applying a bias voltage E _b in the range shown by the following equation to the inverting input terminal of the operational amplifier 21.

E _b ×R ₃ /R ₂ ≧R ₃ /R ₁ ×E _r +V _f where E _r is the reference voltage of the reference power source of the comparator 37 included in the level determination circuit 36 . Further, V _f is the signal level slice circuit 20
The forward voltage of diode D is shown.

Now, as shown in FIG. 4B, the input signals to the signal level slice circuit 20 are a reflected echo signal whose peak value E _e is larger than the reference voltage E _r and a reflected echo signal whose peak value E _o is greater than the reference voltage E If the noise signal component smaller than _r is included, these signals are processed by the operational amplifier 2.
If the diode D is not connected on the output side of 1, the result will be as shown in FIG. That is, the peak value E _e of the reflected echo signal is E _e ·R ₃ /R ₁ , and the peak value E _o of the noise signal is E _o ·R ₃ /R ₁
becomes. In this case, E _e exceeds the zero line shown in FIG. 4B b, and E _o becomes less than the zero line.

By the way, in the actual circuit, as shown in FIG. 3, a diode D is connected to the output side of the operational amplifier 21, so as shown in FIG. 4B c,
Below the zero line (more precisely, below -V _f )
The output of the signal voltage is blocked, and only the original reflected echo signal is output.

Here, if the above-mentioned noise signal includes a peak value E _o larger than the above-mentioned reference voltage E _r (not shown), in that case, among the peak values of the noise signal, , the amount exceeding the zero line is
It will be output. In preparation for such a case, the noise evaluation circuit 30 monitors the noise level.

The noise evaluation circuit 30 uses the microcomputer 3 to set this noise level monitoring period.
1 to form a tracking gate signal, and as shown in FIGS. A noise level judgment gate signal is created from the downstream signal. This noise level determination gate signal opens the AND gate circuit 38b of the noise level determination gate 38 during the period _to .

The comparator 37 uses the received input voltage as a reference voltage.
When compared with E _r , if there is an input voltage exceeding the reference voltage E _r , a high level signal is output. That is, the fourth
When there is an input signal shown in Fig. A, the binary signals ',',' as shown in Fig. 2F are outputted to point A in Fig. 2C.

These binarized signals are ANDed by the noise level judgment gate 38, and among them, those outputted during the period t _o are judged by the gate 38.
“1” is output from b as a high noise level determination signal. FIG. 4g shows the signal waveform at point B in FIG. 2C.

This determination signal is input to the terminal of the flip-flop circuit 39, and sets the flip-flop circuit 39 to a set state. As a result, this judgment signal is
The signal is held in the flip-flop circuit 39 and output from its Q terminal as a high noise level determination signal. In Figure 4Ah, C shown in Figure 2C.
The high noise level judgment signal output at the point is shown.
Note that the flip-flop circuit 39 is reset by the transmission command pulse signal.

The gain control signal generation circuit 40 monitors whether the noise level judgment output is "1" or "0" while outputting the set gain control signal, and if it is "1", the gain of the variable gain amplifier 10 is kept constant. To lower the level
The gain control signal is changed; on the other hand, when it is "0", the current gain is maintained as it is.

That is, as shown in FIG. 4B, the gain control signal generation circuit 40 maintains the gain control signal as it is when the peak value of the noise signal is smaller than the reference voltage E _r . On the other hand, as shown in FIG. 4A, when the peak value of the noise signal is larger than the reference voltage _Er , the set value is changed and output as a corresponding gain control signal.

Variable gain amplifier 10 amplifies the input signal with a gain indicated by this gain control signal.

Now, if the gain is lowered and a noise signal of the same level as the previous one is input, its output level will be lower than the previous one. As a result, if the peak value becomes smaller than the reference voltage _Er , this noise signal is removed in the signal level slice circuit 20. Further, the noise evaluation circuit 30 does not output a high level determination signal, and the variable gain amplifier 10
The amplification gain of is maintained as is.

On the other hand, when a noise signal whose peak value is larger than the reference voltage E _r is input, the same operation as described above is repeated to further lower the amplification gain of the variable gain amplifier 10 to a certain level.

In this way, according to this embodiment, the level of the input noise signal can be evaluated, and based on this evaluation, the input signal is sliced at a voltage greater than the peak value of the input noise signal at the next measurement. This removes the noise signal that exists before the reflected echo signal and prevents erroneous measurements.

Note that due to the above-mentioned slice, the waveform of the original reflected echo signal is also reduced. However, this can be compensated for by amplifying with the amplifier 50 in the subsequent stage. Moreover, since noise is removed, the S/N of the amplified signal is significantly improved.

<Other Embodiments> The present invention is not limited to the first embodiment described above, and various embodiments are possible for each component. Below are some examples.

In the example shown in FIG. 5, the level determination circuit is configured to use only the tracking signal as the noise level determination gate signal of the noise level determination gate 38, and input the transmission mask signal to the reset terminal R of the flip-flop circuit 39. It is.

In the example shown in FIG. 6, the level determination circuit is constructed by adding a switch 38c to the noise level determination gate 38 that opens and closes in response to the noise level determination gate signal, and also providing the switch 38c on the input side of the comparator 37 to detect the input signal. This is an example of a configuration in which the signal is input to the comparator 37 only during the noise level determination period.

FIG. 7 shows an example of a circuit for creating the noise level determination gate signal used in each of the above embodiments. This circuit consists of a D flip-flop circuit 38
In this example, inverter 3 is configured using d.
The transmission mask signal inverted at 8e is used as a clock signal, and the tracking gate signal inverted at inverter 38f is used as a clear signal to obtain a noise level determination gate signal.

Although not shown, the transmission mask signal is
It can be formed using a microcomputer. That is, similar to steps 5 and 6 in FIG. 10 described above, a counter is set by a program, triggered by a transmission command pulse, and a transmission mask signal is formed by counting clock pulses with the counter.

[Effects of the Invention] As explained above, the present invention allows the level of input noise to be evaluated for each measurement, and the evaluation can be used for the next measurement, and the level of input noise can be evaluated at the next measurement. This has the effect of making it possible to remove or reduce noise, improve the S/N ratio of the measuring instrument, and prevent erroneous measurements even when the mask gate is fully open.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of the noise evaluation method of the berthing support system of the present invention, FIG. 2A is a block diagram showing the configuration of the first embodiment of the noise evaluation method of the present invention, and FIG. 2B is the noise evaluation method of the present invention. FIG. 2C is a circuit diagram showing an example of the noise determination circuit that constitutes the above embodiment, and FIG. 3 is a block diagram showing an example of the noise removal circuit incorporating the noise removal circuit. A circuit diagram showing an example, FIGS. 4A and 4B are waveform diagrams for explaining the operation of the first embodiment, and FIGS. 5 and 6 are diagrams showing the second and third embodiments of the noise evaluation method of the present invention, respectively. A circuit diagram showing the configuration of an example; FIG. 7 is a circuit diagram showing an example of a circuit for creating a noise level gate signal that can be used in each of the above embodiments of the present invention; FIG. 8 shows a conventional noise removal circuit for measuring instruments. FIG. 9 is a waveform diagram showing the operation of the conventional noise removal circuit for a measuring instrument, and FIG. 10 is a flowchart showing the operation of the microcomputer that forms the tracking gate signal in the first embodiment. 10... Variable gain amplifier circuit, 20... Signal level slice circuit, 21... Operational amplifier, 30...
Noise level evaluation circuit, 31...Microcomputer, 32...Microprocessor, 33...
Memory, 34... I/O port, 36... Level judgment circuit, 37... Comparator, 38... Noise level judgment gate, 38a, 38b... AND gate circuit, 39... Flip-flop circuit, 4
0...gain control signal generation circuit, 50...amplifier,
60... Time measurement circuit, 70... Timing signal generation circuit.

Claims (1)

[Claims] 1. Noise evaluation of an ultrasonic measurement system in a system that uses ultrasonic waves to measure the distance of a ship attempting to berth from a quay, notifies the ship, and supports the ship to appropriately decelerate and berth. A distance/speed calculation means that calculates the distance from the quay to the ship based on the measured values up to the previous time, and calculates the speed of the ship from the calculated distance and the ultrasonic transmission cycle; Receiving wave predicted arrival time region calculation that calculates a predicted arrival distance based on the transmission period and the above-mentioned calculated distance, and calculates a received wave predicted arrival time region after the transmitted wave is transmitted at the next measurement time from the predicted arrival distance and the sound speed. and a means for setting a time domain for noise level determination before the calculated received wave predicted arrival time domain after transmitting the transmitted wave, and outputting the noise level determination result only within the noise level determination time domain. a gate setting means for noise level determination, which sets a gate for determining a noise level; and a peak value of a received input signal is compared with a preset reference value, and if there is an input signal whose peak value exceeds the reference value, a high noise level is detected. 1. A noise evaluation method for a berthing support system, comprising: noise level determination means for outputting a determination signal. 2 The noise level determination gate setting means includes:
A patent claim that sets a time domain necessary for preventing erroneous reception due to transmission system signal contamination such as transmission omission or transmission reverberation as a transmission mask gate, and outputs a noise level determination result after the transmission mask gate ends. Noise evaluation method for the berthing support system described in item 1.