JPH0431551B2 - - 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 provides guidance assistance so that the ship can appropriately decelerate and berth. This invention relates to a weak signal receiving device for an ultrasonic measurement system in a system.

[Prior Art] In this type of berthing guidance support system, the berthing speed of a ship is generally measured by detecting the distance at a predetermined sampling period using an ultrasonic range finder and measuring the change in this distance over time. ing.

The ultrasonic range finder emits ultrasonic pulses from a quay toward a ship, receives reflected waves that are reflected by the ship's hull, and calculates the distance from the round trip time and the speed of sound. In this case, the round trip time is
The transmission of the transmitted wave is used as a trigger to open the gate, the reception of the reflected wave is used as the trigger to close the gate, and while the gate is open, the reference clock pulses output from the clock circuit are counted, and the counted value is based on the gate. It is obtained by calculating the time.

By the way, in this type of gate, in order to prevent malfunctions due to noise, it is necessary to separate received waves from noise. Therefore, a signal extraction circuit consisting of a comparator or the like is provided to extract only received waves above a certain threshold level as received pulses.

In order to extract the received pulse from the reflected wave whose level has been attenuated, the level of the received wave must be amplified so that it exceeds the threshold level of the signal extraction circuit. Furthermore, it is necessary to set the threshold level of the signal extraction circuit in accordance with this amplification.

In this case, if the amplification degree is increased too much, it will rise to the noise level and cause erroneous measurements, so the amplification degree must be set within an optimal range.

Conventional berthing guidance assistance systems are configured to amplify received waves using a variable gain amplifier equipped with a manual gain adjuster. Gain adjustment was performed by receiving reflected waves at the location where the guidance assistance system was installed and manually adjusting a gain adjuster so that the received waves were at an optimal level.

On the other hand, the threshold level is set by adjusting the output voltage of the threshold voltage generation circuit in accordance with the output of the variable gain amplifier.

[Problems to be Solved by the Invention] However, in the conventional gain adjustment and threshold level setting described above, the adjustment is made when the device is installed and the device is left fixed. It has the disadvantage of causing erroneous measurements when heated. In addition, since the adjustment work is done by humans,
It is inevitable that variations in adjustment will occur depending on the operator.

Furthermore, when the echo level decreases and the reflected waves cannot be received, it is difficult to make adjustments each time. As a result, there is a problem in that continuous measurement becomes impossible.

The present invention has been made to solve the above-mentioned problems, and its purpose is to constantly monitor the level of the received signal and automatically adjust the gain to the optimum level. It is possible to constantly monitor whether or not the echo level is being output, and automatically change the threshold level to ensure that the received pulse can be captured. To provide a weak signal receiving device for a berthing guidance assistance system that can cope with such problems, does not become unable to measure continuously, and does not cause individual differences in adjustment.

By the way, since the echo level often fluctuates, if it is adjusted each time, it may have the opposite effect and increase the fluctuation width of the next reflected wave. Furthermore, if the threshold level is adjusted every time the received wave level accidentally drops, there is a risk that noise will be picked up when the echo level becomes high.

Another object of the present invention is to provide a weak signal receiving device for a berthing guidance assistance system that can detect that fluctuations are occurring either high or low and make appropriate adjustments.

[Means for Solving the Problems] The present invention provides an ultrasonic measurement system in a system that measures the speed, etc. of a ship attempting to berth using ultrasonic waves, notifies the ship, and assists the ship to berth at an appropriate speed. In order to achieve the above-mentioned purpose, the weak signal receiving device of 2008 is equipped with a variable gain amplifier that amplifies the received signal with a gain specified by a gain control signal, and a preset upper and lower limit, as shown in Fig. 1. The level of the amplified received signal is within the appropriate range between
Compare and judge whether the level is within the appropriate range, higher than the upper limit value, or lower than the lower limit value, and the state is "higher than the upper limit value" or "lower than the lower limit value". gain control means for outputting a gain control signal that changes the gain of the variable gain amplifier when the variable gain amplifier continues for a predetermined number of times; a signal extraction circuit that outputs a received signal exceeding the threshold level as a received pulse to a subsequent stage; and threshold level changing means for instructing a change in the threshold level of the extraction circuit.

For example, as shown in FIG. 2, the gain control means sets an appropriate range between a preset upper limit and a lower limit, and adjusts the level of the amplified received signal to
A level judgment circuit that compares and judges whether the level is within the appropriate range, higher than the upper limit value, or lower than the lower limit value and outputs a level status signal corresponding to each; continuity determination means for outputting a level change instruction signal to change the gain of the variable gain amplifier when the level is "higher than the upper limit value" or "the level is lower than the lower limit value" and this state continues for a predetermined number of times; and a gain control signal generation circuit that generates a gain control signal that instructs to change the gain of the variable gain amplifier in response to the level change instruction signal from the continuity determining means.

In addition, the threshold level changing means described above is
For example, as shown in Fig. 2, after the transmission wave is transmitted and before the next transmission, it is determined whether or not a reception pulse is output from the signal extraction circuit, and a status signal indicating the presence or absence of the reception pulse is output. a circuit for determining the presence or absence of a received pulse; continuity determining means for monitoring the status signal and outputting a threshold level change instruction signal when the received pulse is not output a preset number of times in succession; and changing the threshold level. and a threshold voltage generation circuit that receives an instruction signal and outputs a corresponding threshold level to the signal extraction circuit.

[Operation] In the problem solving means of the present invention configured as described above, the variable gain amplifier amplifies the received signal with a gain specified by the gain control signal. Therefore, unlike manual adjustment, which has large individual differences,
Automatic constant adjustment is possible.

In addition, since the gain control means constantly monitors whether the level of the received signal is within the appropriate range, it is possible to adequately deal with not only the initial adjustment when installing the berthing guidance support system, but also any subsequent fluctuations. be able to. Therefore, even if a received signal at a level that can act as a gate trigger cannot be obtained because the level of the reflected wave is low, the gain is automatically changed to obtain a received signal at a triggerable level. Furthermore, when the gain of the amplifier is large and the noise level is high, the gain is lowered to prevent erroneous reception due to noise.

On the other hand, the signal extraction circuit is automatically set to a specified level by the threshold level changing means. This setting is performed by detecting that the received pulse is not continuously output a preset number of times from the signal extraction circuit. Therefore, it is not changed by accidental fluctuations.

This threshold level is changed when the echo level of the received wave does not reach the threshold level, so the change is performed exclusively by lowering the threshold level.
This change is particularly effective when the echo level of the received wave is still low even if the gain of the variable gain amplifier is set to the maximum.

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

<Configuration of Embodiment> FIG. 3 shows the configuration of an embodiment of the weak signal receiving device of the present invention.

The receiving system of the embodiment shown in the figure includes a variable gain amplifier 1, a level determination circuit 2 that determines whether the level of the output voltage of the amplifier 1 is within an appropriate range,
The gain control signal generation circuit 4 which forms a gain control signal according to the level change instruction signal and sends it to the variable gain amplifier 1, the signal extraction circuit 5, and whether or not a received pulse is output from the signal extraction circuit 5. A threshold voltage generation circuit 8 changes the threshold level according to a level change instruction signal and sends it to the signal extraction circuit 5, and a microcomputer 9.

The level determination circuit 2 comprises, for example, a window comparator, and compares the output signal level of the variable gain amplifier 1 with reference to a preset upper limit value and lower limit value. As a result of the comparison, if the signal level is between the upper and lower limits, it is "appropriate", and if it exceeds the upper limit, it is "high level".
and level status signals PROPER, HIGH, and
Outputs LOW.

In this embodiment, the gain control signal generation circuit 4 forms a gain control signal that changes the amplification gain of the variable gain amplifier stepwise in a range of one to a plurality of stages. In this embodiment, this gain control signal is changed by ±1 step in accordance with instructions from the microcomputer 9.

The signal extraction circuit 5 is composed of a comparator, and compares the output voltage of the variable gain amplifier 1 with a threshold voltage, and outputs a received pulse when the output voltage exceeds the threshold voltage.

The received pulse presence/absence determination circuit 6 is configured to determine whether or not a pulse has been input within a predetermined period of time after opening the gate described above, and output a status signal indicating the presence or absence of a received pulse.

The threshold voltage generation circuit 8 is comprised of a variable voltage DC power supply, and in this embodiment, is sent to the comparator of the signal extraction circuit 5 as a threshold voltage. This threshold voltage generation circuit 8 is
In response to instructions from continuity determining means 7, which will be described later,
Can output one to multiple stages of different voltages.

The microcomputer 9 functions as a continuity determining means 3 that determines whether the inappropriate level continues for a certain number of times, and as a continuity determining means 7 that determines that the received pulse is not output continuously for a certain number of times. This microcomputer 9 includes a microprocessor 90, a program memory 91 that stores programs for the processor 90, an input/output port 92, and an internal bus 93 that connects these.
It is composed of: Note that this microcomputer 9 does not need to be provided exclusively for the continuity determining means 3 and 7, and one used for other purposes of the system can be used.

<Operations of the Embodiment> The weak signal receiving device of this embodiment configured as described above operates as follows.

First, as shown in FIG. 4, a transmitted wave T is transmitted at a cycle longer than the round trip time required for ultrasonic waves, and a reflected wave R is received after the round trip time has elapsed after the transmission of the transmitted wave. Since this received wave R is attenuated, it is amplified by the variable gain amplifier 1. As a result, as shown in FIG. 4, if the peak value is between the upper and lower limits of the appropriate range, it is determined that the received wave is normal.

A level determination circuit 2 determines whether the received wave is at an appropriate level. Level judgment circuit 2
is PROPER, which means "appropriate" if the signal level is between the upper and lower limits as a result of comparison,
If it exceeds the upper limit, it means "high level"
It outputs corresponding level status signals of HIGH and LOW, which means "low level" if it falls below the lower limit.

Furthermore, the continuity determining means 3 determines whether the level determining circuit is ``high level'' or ``low level''.
Either level status signal HIGH or
LOW is the preset number of times (twice in this example)
The continuity determining means 3 monitors whether or not they are outputted continuously, and when either one is outputted consecutively a predetermined number of times, the continuity determining means 3 outputs a level change instruction signal. This action will be explained with reference to the flowchart of FIG.

First, the microprocessor 90 of the continuity determining means 3 reads the received signal level status signal from the level determining circuit 2 through the input/output port 92 (step 1). Then, the microprocessor 90 checks whether this status signal is PROPER or not, and checks whether it is within the appropriate range (step 2). If it is within the appropriate range, return to step 1. If it is inappropriate, proceed to step 3.

Step 3 determines whether the received signal level is higher or lower than the appropriate range by checking whether the status signal is HIGH or
Determine whether it is LOW or not. Here, as shown in Figure 5, if it is "high level",
The microprocessor 90 checks whether the level was "high" during the previous sampling (step 4). If the level is not "high", return to step 1. If the previous time was also "high level", proceed to step 5.

Note that the microprocessor 90 stores the previous status signal in a memory (not shown).
After checking the previous status signal, the current status signal is updated.

In step 5, a signal is sent to the internal bus 93 to set the gain level to -1 and instruct the gain to be lowered by one step.
and is sent to the gain control signal generation circuit 4 via the input/output port 92.

Note that in step 3 above, if the level is lower than the lower limit value, the microprocessor 9
0, it is checked whether it was at a "low level" during the previous sampling (step 6). If the level is not "low", return to step 1. If the previous time was also "low level", proceed to step 7.

In step 7, a signal is sent to the internal bus 93 to set the gain level to +1, instructing to raise the gain by one step.
and is sent to the gain control signal generation circuit 4 via the input/output port 92.

In response to this, the gain control signal generating circuit 4 generates a gain control signal for specifying a change in the gain of the variable gain amplifier 1.

Even if the gain of the variable gain amplifier 1 is lowered in this way, as shown in FIG.
If the level of the received waveform is higher than the appropriate range, the same operation as described above is repeated until it becomes as shown in the figure.

Note that in this embodiment, when a "high level" received signal and a "low level" received signal appear alternately, neither state occurs consecutively twice, so the gain of the variable gain amplifier is not changed.

Next, the received wave output from the variable gain amplifier 1 is input to the signal extraction circuit 5 and compared with the threshold voltage output from the threshold voltage generation circuit 8. As a result, if the input signal is larger than the threshold voltage, the received wave is taken out as a received pulse and sent to a subsequent gate (not shown).

On the other hand, as shown in Fig. 7, when the input signal is lower than the threshold voltage, this input received wave is
Not output as a signal. Output presence/absence determination circuit 6
The microprocessor that constitutes the continuity determining means 7 monitors whether or not a received pulse is output after transmitting the transmitting wave T and before transmitting the next transmitting wave T, and sends a status signal indicating the presence or absence of the received pulse. Send to Setsa90. In this embodiment, a signal is output as a status signal indicating the presence or absence of a received pulse, which is at a high level when a received pulse is being output, and is at a low level when a received pulse is not being output.

The microprocessor 90 determines continuity, as shown in FIG. That is, the output pulse presence/absence status signal is read (step 1), and the presence or absence of the status signal is checked (step 2). If the signal is at a high level, the received pulse has been output, and the microprocessor 90 returns to step 1. On the other hand, as shown in FIG. 7, if the signal is at a low level, the process proceeds to step 3.

In step 3, it is checked whether there was no status signal during the previous sampling. If there was a status signal last time, the process directly returns to step 1. On the other hand, if there was no status signal last time as well, the process advances to step 4. That is, in this example, 2
When there is no status signal for consecutive times, the threshold level is changed.

The microprocessor 90 stores the previous status signal in a memory (not shown), and after checking the previous status signal, updates it to the current status signal.

In step 4, a signal instructing to lower the threshold voltage by one step is sent to the threshold voltage generation circuit 8 via the internal bus 93 and the input/output port 92.

In response to this, the threshold voltage generation circuit 8
sends a threshold voltage lower than that during the previous sampling to the signal extraction circuit 5.

Even if the threshold voltage of the signal extraction circuit 5 is lowered in this way, if the level of the received waveform is lower than the threshold level as shown in FIG. 7, the same operation as described above is performed. ,
Repeat until it looks like in the figure.

<Modification of Embodiment> In the above embodiment, the gain of the variable gain amplifier is changed when either a "high level" received signal or a "low level" received signal occurs twice in a row. However, the number of consecutive attempts may be three or more times.

Similarly, there are two conditions in which the input signal is below the threshold level and no status signal is output.
Although the configuration is such that the threshold level is changed when the threshold level is changed consecutively, the number of consecutive times may be three or more times.

Further, in the above embodiment, the continuity determination means 3 and 7 are configured by a microcomputer, but the level determination circuit 2, gain control signal generation circuit 4, output pulse presence/absence determination circuit 6, etc. are also configured by a microcomputer. can do.

[Effects of the Invention] As explained above, the present invention can constantly monitor the level of the received signal and automatically adjust it to the optimum level, and can also constantly monitor whether or not the received pulse is being output. The threshold level can be automatically changed to ensure that the received pulse can be captured, and it can automatically respond to fluctuations in the echo level after the device is installed, making continuous measurements impossible. Moreover, there is an effect that adjustment can be made without causing individual differences in adjustment.

Further, the present invention has the advantage that it is possible to detect that the peak level fluctuation of the received wave is occurring in either the high or low direction, and to make appropriate adjustments.

Therefore, according to the present invention, it is possible to realize a weak signal receiving device for a berthing guidance assistance system that is less likely to cause erroneous measurements.

[Brief explanation of drawings]

Figure 1 is a block diagram showing the configuration of the present invention, Figure 2 is a block diagram showing the configuration of the present invention.
The figure is a block diagram showing details of the configuration of the present invention.
The figure is a block diagram showing the configuration of an embodiment of the present invention.
4 and 5 are waveform diagrams for explaining the gain control action of this embodiment, FIG. 6 is a flowchart for explaining the gain control action of this embodiment, and FIG. 7 is a waveform diagram for explaining the gain control action of this embodiment. FIG. 8 is a waveform diagram for explaining the effect of changing the threshold level. FIG. 8 is a flowchart for explaining the effect of changing the threshold level of this embodiment. DESCRIPTION OF SYMBOLS 1... Variable gain amplifier, 2... Level determination circuit, 3... Continuity determination means, 4... Gain control signal generation circuit, 5... Signal extraction circuit, 6... Reception pulse presence/absence discrimination circuit, 7... Continuity determining means, 8...
Threshold voltage generation circuit, 90...Microprocessor, 91...Program memory, 92...
...I/O port, 93...Internal bus.

Claims (1)

[Scope of Claims] 1. In a weak signal receiving device for an ultrasonic measurement system in a system that measures the speed, etc. of a ship attempting to berth using ultrasonic waves and notifies the ship to assist the ship in berthing at an appropriate speed, A variable gain amplifier amplifies the received signal with a gain specified by a gain control signal, and the level of the amplified received signal is set within the appropriate range between the upper and lower limits set in advance.
Compare and judge whether the level is within the appropriate range, higher than the upper limit value, or lower than the lower limit value, and the state is "higher than the upper limit value" or "lower than the lower limit value". gain control means for outputting a gain control signal that changes the gain of the variable gain amplifier when the variable gain amplifier continues for a predetermined number of times; a signal extraction circuit that outputs a received signal exceeding the threshold level as a received pulse to a subsequent stage; 1. A weak signal receiving device for a berthing guidance assistance system, comprising threshold level changing means for instructing a change in threshold level of a take-out circuit. 2 The gain control means sets an appropriate range between a preset upper limit value and a lower limit value, and controls the level of the amplified received signal to be
A level judgment circuit that compares and judges whether the level is within the appropriate range, higher than the upper limit value, or lower than the lower limit value and outputs a level status signal corresponding to each; continuity determination means for outputting a level change instruction signal to change the gain of the variable gain amplifier when the level is "higher than the upper limit value" or "the level is lower than the lower limit value" and this state continues for a predetermined number of times; and a gain control signal generation circuit that generates a gain control signal that instructs to change the gain of the variable gain amplifier in response to the level change instruction signal from the continuity determining means. A weak signal receiving device for the berthing guidance assistance system described in . 3 The threshold level changing means determines whether or not a received pulse is output from the signal extraction circuit after transmitting the transmitted wave and before the next transmission, and outputs a status signal indicating the presence or absence of the received pulse. a circuit for determining the presence or absence of a received pulse; continuity determining means for monitoring the status signal and outputting a threshold level change instruction signal when the received pulse is not output a preset number of times in succession; and changing the threshold level. A berthing guidance assistance system according to claim 1 or 2, further comprising a threshold voltage generation circuit that receives an instruction signal and outputs a corresponding threshold level to the signal extraction circuit. Weak signal receiver.