JPH10186060A - Ultrasonic snow gauge - Google Patents

Abstract

(57) [Summary] [Problem] To introduce the concept of table conversion by software into the determination of the gain of an amplifier circuit, even if the reception level of the reflected wave changes exponentially sharply due to the propagation distance, weather conditions, etc. Provided is an ultrasonic snowfall meter capable of accurately compensating for attenuation of a reflected wave by changing a gain characteristic according to the steeply changing attenuation characteristic. SOLUTION: A storage means 32 for converting a reflected wave from a monitoring area into digital data and storing the digital data, a receiving level determining means 38 for determining a receiving level of the stored reflected wave, and a receiving level of the reflected wave. A table conversion memory 36 storing the corresponding gain value, a table conversion means 37 for converting the reception level of the reflected wave into a gain value by referring to the conversion table, and a gain value comprising the converted digital data as an analog signal And a receiving gain control circuit 18 'for automatically setting a circuit gain to a gain value given from the DA conversion circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic snowfall meter used for weather observation on roads and the like, and more particularly, to a snow depth by constantly controlling a receiving gain to an optimum value with respect to attenuation of ultrasonic waves. The present invention relates to an ultrasonic snow gauge capable of accurately measuring the snow.

[0002]

2. Description of the Related Art First, the measurement principle of this type of ultrasonic snow gauge will be described with reference to FIG. An ultrasonic transducer mounted on the ground GL at a height H (hereinafter referred to as a transducer).
Using a round trip propagation time t (hereinafter, referred to as a reflection time) t from transmitting an ultrasonic wave from 15 to the ground GL to receiving a reflected wave from the snow surface, and a sound velocity V with respect to the temperature at that time, the following ( 1) The snow depth D is measured from the equation (2). In order to compensate for a change in the sound speed V of the ultrasonic wave due to a change in the air temperature, a ventilation tube W having a built-in temperature sensor for detecting the temperature T is attached to the column P.

V = 331.45 + 0.61T (1) D = {H− (t / 2) · V} (2) where V: sound velocity at temperature T ° C. (m / s) T: temperature (° C.) D: Snow depth (m) H: Height from ground GL to transducer 15 (m) t: Reciprocating propagation time of ultrasonic wave (s)

FIGS. 6 and 7 show an example of a conventional ultrasonic snow gauge constructed based on the above principle. FIG. 6 is a block diagram of an electric circuit, and FIG. 7 is an operation waveform diagram of each part of the circuit. The circuit roughly radiates ultrasonic waves toward the ground,
A propagation time measurement system 1 for measuring a reflection time t until the reflected wave returns, a temperature measurement system 2 for measuring a temperature T,
It is divided into a control unit 3 that calculates the snow depth D from the signals of the systems 1 and 2.

[0005] The propagation time measuring system 1 includes a transmission start signal a provided from a timing generation means 31 of the control unit 3 described later.
, A pulse generating circuit 11 for sequentially outputting an intermittent pulse c of 1 ms width at a repetition cycle of 100 ms, an oscillator 12 for outputting a high-frequency signal (carrier) d of 40 kHz, for example, and combining both signals for 1 ms and 40 KH.
a burst wave generating circuit 13 for outputting a transmission signal e composed of a burst wave of z, and an amplifier 14 for amplifying the transmission signal e
And a transmitter / receiver 15 that converts a transmission signal e output from the amplifier 14 into an ultrasonic wave and emits the ultrasonic wave toward the ground and receives the reflected wave, and a reception signal f received by the transmitter / receiver 15. Amplifier 16 to amplify and 40 k from received signal f
And a detection circuit 17 for removing a high-frequency signal of 1 Hz and outputting it as a detection signal g, and a detection signal g reflected from a snow surface in the detection signal g by opening a gate by the reception gate signal b provided from the timing generation means 31 described above. STC (Gain time control: Sensit) that allows only the signal i to pass through and amplifies with a gain corresponding to the reception timing of the reflected wave detection signal i.
(ivty Time Control) circuit 18, and an AD conversion circuit 19 that converts the reflected wave detection signal i amplified by the STC circuit 18 into digital data and sends the digital data to the control unit 3.

A temperature measuring system 2 includes a temperature sensor 20 composed of a platinum temperature measuring element, an amplifier 21 for amplifying a temperature detection signal output from the temperature sensor 20, and a digital signal for converting the amplified temperature detection signal from an analog signal to a digital signal. A to convert to data
And a D conversion circuit 22.

The control unit 3 includes a timing generating means 31 for generating a transmission start signal a and a reception gate signal b,
Received data storage means 32 for storing the AD converted reflected wave detection signal i sent from the propagation time measurement system 1, and the reception time of the reflected wave from the reflected wave detection signal i stored in the received data storage means 32 Receiving time detecting means 3 for detecting position
3, a propagation time calculating unit 34 for calculating a reflection time t of the ultrasonic wave from a time difference between the detected reception time position and the transmission start position of the transmission start signal a, and a temperature detection from the temperature measurement system 2. The sound speed V of the ultrasonic wave at that time is calculated using the signal, and the snow depth calculating means 35 for calculating the snow depth D using the sound speed V and the reflection time t is provided.

The operation of the conventional ultrasonic snow gauge having the above-described configuration will be briefly described. The ultrasonic wave reflected on the snow surface (or the ground) is input to the transducer 15 and amplified by the amplifier 16. The signal is detected by the detection circuit 17 and sent to the STC circuit 18. The STC circuit 18 allows only the reflected wave detection signal i from the snow surface in the detection signal g to pass by opening the gate only during the reception gate signal b given from the timing generation means 31, and the reflected wave detection signal i at that time. After being amplified with a gain corresponding to the reception timing of the
Then, the data is converted into digital data and sent to the received data storage means 32 of the control unit 3 for storage.

Next, the receiving time detecting means 33 is shown in FIG.
As shown in (B), the maximum level position of the reflected wave detection signal i stored in the reception data storage means 32 is detected as the reception time position of the reflected wave and sent to the propagation time calculation means 34.
The propagation time calculation means 34 calculates the reflection time t of the ultrasonic wave from the time difference between the detected reception time position and the transmission start position of the transmission start signal a. Next, the snow depth calculating means 3
5 uses the data of the temperature T sent from the AD conversion circuit 22 of the temperature measurement system 2 to obtain the sound velocity V of the ultrasonic wave at that time from the above equation (1). Finally, using the sound velocity V and the reflection time t obtained above, the snow depth D is calculated from the equation (2), and the calculation result is output to an external display or the like via the output circuit 4. Then, display or record in a desired format.

[0010]

As shown in the waveform diagram at the bottom of FIG. 7, the STC circuit 18 in the above-mentioned conventional ultrasonic snow meter measures the gain linearly or exponentially. To amplify the signal as a gain corresponding to each reception timing.

However, the attenuation characteristics of the ultrasonic waves reflected from the snow surface vary greatly as shown in FIG. 8, and it is difficult for the above-described STC circuit to accurately and sufficiently compensate for the attenuation. Was. That is, when the ultrasonic wave travels 1 m in the air, the attenuation is reduced by half. For example, in FIG. 5, the transducer 15 is set at H = 7 m from the ground GL.
If it is installed at the height of, the attenuation is twice (１ ／) 7 times the power of 7 (round trip), that is, 1/1.
It reaches 6383 (-84 dB). Furthermore, since the horn shape of the transducer 1, the weather condition of the propagation space, the snow quality, and the like affect the change, the variation of the attenuation becomes more irregular and large.

When observing the amount of snow on a road or an urban area, the maximum amount of snow that can be considered is usually a height of about 2 m from the ground GL, and information of reflected ultrasonic waves from this range is extremely important. As is clear from FIG. 8, the ultrasonic wave has the steepest and most intense attenuation in the vicinity. For this reason,
In the level control of the received signal using the conventional STC circuit, it is impossible to reliably follow the steep change, and the curve becomes as shown by a two-dot chain line in FIG. However, there is a problem that it is difficult to compensate for the reception gain while following the above.

When the distance from the transducer 1 to the road surface is long, the attenuation is further increased, and the snow depth near the road surface is affected by external noise such as engine noise of an automobile. There was also a problem that sometimes it was not possible to measure correctly.

The present invention has been made in order to solve the above-mentioned problem. The concept of table conversion by software is introduced for determining the gain of an amplifier circuit, and the reception level of a reflected wave is indexed according to the propagation distance and weather conditions. Even if it changes functionally steeply, the gain characteristics are changed along the steeply changing attenuation characteristics to accurately compensate for the attenuation of the reflected wave, minimize the level fluctuation of the received signal, and reduce the snow depth. It is an object of the present invention to provide an ultrasonic snow gauge capable of measuring accurately.

Further, by receiving a reflected wave only for a minimum time required for measurement, the influence of external noise such as an engine noise of an automobile can be suppressed as much as possible, and the ultrasonic snow depth can be measured more accurately. The purpose is to provide a total.

[0016]

According to a first aspect of the present invention, an ultrasonic wave is radiated toward the ground, and the reflection time from the snow surface is measured to determine the snow depth. In an ultrasonic snowfall meter configured to measure, a storage unit that converts a reflected wave from a monitoring area into digital data and stores the digital data, a reception level determination unit that determines a reception level of the stored reflected wave, A table conversion memory storing a gain value corresponding to the wave reception level, table conversion means for converting the reception level of the reflected wave to a gain value by referring to a conversion table of the table conversion memory, and the converted A DA conversion circuit for converting a gain value composed of digital data into an analog signal;
A receiving gain control circuit for automatically setting a gain value provided from the conversion circuit.

In the case of the first aspect of the present invention, the optimum gain value corresponding to the reception level of the reflected wave can be provided by the conversion table, so that the reflected wave can be attenuated no matter how steeply attenuated. An extremely large gain value corresponding to this can be prepared. For this reason, as shown by the bold dotted line in FIG. 8, the gain can be compensated in accordance with the attenuation characteristic of the reception level of the reflected wave that attenuates exponentially sharply, and in any weather condition. It is also possible to accurately measure the snow depth.

Further, the invention according to claim 2 is characterized in that timing generation means for setting a gate time of a reception signal based on a reception timing signal from the reception level determination means is provided.

According to the second aspect of the present invention, the reflected wave is received only for the minimum time required for the measurement, so that the influence of external noise such as engine noise of a car can be suppressed.
The snow depth can be measured more accurately.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 show an embodiment of an ultrasonic snow gauge according to the present invention. FIG. 1 is a block diagram of an electric circuit, and FIG. 2 is an operation waveform diagram of each part of the circuit of FIG. In the figure, the same parts as those in the conventional example (FIG. 6) are denoted by the same reference numerals, and detailed description thereof will be omitted. The temperature measurement system 2 of the propagation time measurement system 1, the temperature measurement system 2, and the control unit 3 has exactly the same circuit configuration as the conventional example.

In the propagation time measuring system 1, different points from the conventional example are a DA converter 10, a detector 17 ', and a reception gain controller 18'. The DA conversion circuit 10
This is a circuit which converts a gain setting signal m composed of digital data sent from a table conversion means 37 of the control unit 3 described later into an analog signal and sends it to a reception gain control circuit 18 '.

The detection circuit 17 'includes a reception gain control circuit 1
The detection operation and the non-detection operation are alternately repeated for each period of ultrasonic transmission and reception by the enable (effective) signal EN from 8 '. When the enable signal EN is given, the signal is received by the transducer 15. 40 kHz from received signal f
The high frequency signal of z is detected and removed, and is output as a detection signal g consisting of only an envelope component. When the enable signal EN is not given, the detection operation is stopped and 40 k
The received signal f on which the Hz is superimposed is output as it is.

The reception gain control circuit 18 'sets the gain of the circuit to an optimum value based on a gain setting signal m sent from a table conversion means 37 to be described later via the DA conversion circuit 10, and sets an enable signal. EN is alternately transmitted to the detection circuit 17 'every cycle. Further, the gate for selectively passing the output signal of the detection circuit 17 'is turned ON / OFF by the reception gate signals h and j given from the timing generation means 31' of the control section 3 described later.

The receiving gain control circuit 18 'is different from the above-described conventional STC circuit 18 in that the circuit gain is not gradually increased but the table conversion means 36 is used.
It is characterized in that the circuit gain is instantaneously set to a specified value based on the gain setting signal m sent from. As described above, by directly setting the circuit gain by the table conversion means 36, the circuit gain can be instantaneously set from an extremely small value to an extremely large value.
It is possible to cope with any fluctuation or attenuation of the reception level.

On the other hand, in the control unit 3, the parts different from the conventional example are the timing generation means 31 ', the reception time calculation means 33', the table conversion memory 36, the table conversion means 3
7 and a reception level determination unit 38.

The timing generation means 31 'sends the transmission start signal a to the pulse generation circuit 11 and the propagation time calculation means 34, and receives the reception timing signal n from the reception level determination means 38, which will be described later. The reception gate signal h, as shown in FIG.
j is transmitted alternately in each cycle of transmission and reception of ultrasonic waves. Further, the separation signal q is stored in the reception data storage unit 3.
2 to transmit the received data to the receiving level determining means 38 during the receiving level determining operation, and to transmit the receiving data to the receiving time calculating means 33 during the reflection time calculating operation. The reception gate signal h is a gate signal for determining the level, and the reception gate signal j is a gate signal for detecting the reception position of the reflected wave. By outputting the reception gate signal j having a very narrow time width when detecting the reception position, it is possible to prevent external noise such as the above-mentioned vehicle engine noise from being mixed into the reception signal, and to more accurately measure the reflection time. Becomes possible.

The table conversion memory 36 is a circuit composed of a ROM or the like in which the reception level of the reflected wave i and the gain value corresponding to the reception level are stored as a conversion table. In this conversion table, the relationship between the reception level and the gain value that sufficiently covers up to the maximum attenuation (1/18000 in the illustrated example) of the attenuation curve in FIG. 8 is stored as a table.

The table conversion means 37 is a circuit which reads out a gain value corresponding to the received signal level given from the received wave level determination means 38 and sends it to the DA conversion circuit 10.
Further, the reception level determining means 38 receives the received data storage means 3 based on the separation signal q of the timing generating means 31 '.
When the reflected wave detection signal i is sent from the second detection signal 2, the reception level of the reflected wave is detected from the reflected wave detection signal i and sent to the table conversion means 37, and the timing generation means 31 '
Is a circuit for transmitting a reception timing signal n.

When the reflected wave high-frequency signal k is sent from the received data storage means 32 by the cut-off signal q of the timing generation means 31 ', the reception time calculation means 33' This is a circuit that analyzes the waveform of the reflected wave high-frequency signal k and obtains the reception time position of the reflected wave of the ultrasonic wave by calculation.

Next, the operation of the ultrasonic snow gauge having the above configuration will be described. Pulse generation circuit 11 of propagation time measurement system 1
When the transmission start signal a is given from the timing generation means 31 'of the control section 3, for example, an intermittent pulse c of 1 ms width is output at a repetition period of 100 ms. Then, in the burst wave generating circuit 13, the signal is combined with a high-frequency signal (carrier) d of, for example, 40 kHz sent from the oscillator 12 to become a transmission signal e composed of a burst wave of 1 ms and 40 kHz. Is transmitted to the transmitter / receiver 15 and is converted into an ultrasonic wave on the ground GL (see FIG. 5).
Fired at.

The ultrasonic wave reflected on the snow surface (or the ground) is received again by the transmitter / receiver 15, amplified by the amplifier 16, and sent to the detection circuit 17 'as a received signal f. To the detection circuit 17 ', an enable signal EN which is alternately turned ON / OFF for each period of ultrasonic transmission / reception is sent from the reception gain control circuit 18'. Therefore, as shown in FIG. 2, when the enable signal EN is "1", the detection circuit 17 'detects and removes the high-frequency signal of 40 kHz in the reception signal f, and detects the detection signal g consisting only of the envelope component. And the enable signal EN
Is "0", the received signal f is passed without detection.

Then, first, the timing generating means 31 '
The gate is opened by the reception gate signal h sent from the controller, and only the reflected wave detection signal i which is a reflected wave component from the snow surface in the detection signal g is passed. Received gain control circuit 1
8 'sets the gain of the circuit to the value specified by the gain setting signal m given from the table conversion means 37, and amplifies the reception signal f sent from the detection circuit 17' with this circuit gain. Next, the gate is opened by the reception gate signal j sent from the timing generation means 31 ', and only a part of the reflected wave high-frequency signal k which is a reflected wave component from the snow surface in the received signal f is passed. As a result, the reflected wave detection signal i and the reflected wave high-frequency signal k are alternately output to the AD converter 19 every period of ultrasonic transmission and reception. The AD converter 19 converts the transmitted reflected wave detection signal i and reflected wave high-frequency signal k into digital data, and sends the digital data to the reception data storage means 32 for storage.

When the received reflected wave detection signal i is sent from the reception data storage means 32 based on the separation signal q from the timing generation means 31 ', the reception level judgment means 38 as shown in FIG. Then, the receiving level of the reflected wave of the ultrasonic wave at that time is determined from the maximum value of the envelope, and is sent to the table converting means 37. Table conversion means 3
7 reads the circuit gain value corresponding to the received wave level from the table conversion memory 36 and sends it to the DA conversion circuit 10. The DA conversion circuit 10 converts the gain value composed of the read digital data into an analog signal, and then sends the analog signal to the reception gain control circuit 18 ', and changes the circuit gain of the reception gain control circuit 18' to the gain value. Set. As a result of repeating such a gain setting operation at every other cycle, a waveform composed of i and k shown in FIG. 2 is obtained, and the reception gain control circuit 18 'has an exponential function as shown in FIG. Gain compensation can be performed along the attenuation curve of the reception level of the reflected wave that attenuates sharply, and the snow depth can be accurately measured in any weather condition.

Further, the reception level determination means 38 sends a reception timing signal n to the timing generation means 31 '. The reception timing generating means 31 'receives the reception timing signal n, generates the above-described reception gate signal j, and sends it to the reception gain control circuit 18'. The reception gate j is 1 ms before and after the initial maximum value of the reflected wave in order to pass only the reflected wave high-frequency signal k in the received signal f.
Pulse width. In this way, by reducing the time width of the gate signal j as much as possible, it is possible to prevent external noise such as an engine noise of an automobile from being picked up, and to more accurately measure the snow depth.

On the other hand, when the received reflected high-frequency signal k is sent from the received data storage means 32 based on the separation signal q from the timing generation means 31 ', the received time calculation means 33' The wave receiving position of the reflected wave is calculated and obtained from the wave high frequency signal k. That is, FIG.
As shown in (A), the waveform of the reflected wave high-frequency signal k is shown in an enlarged manner, the ultrasonic wave starting from the wave front having the maximum value as a starting point.
With respect to wavefronts falling within the frequency range of 0 KHz ± 10%, the positions of wavefronts preceding by a predetermined number, for example, three wavefronts, are obtained, and the position of the wavefront is set as the reception time position of the reflected wave, and the propagation time calculation means is used. Send to 34. Then, the propagation time calculating means 34 calculates the reflection time (reciprocation time) t of the ultrasonic wave to the snow surface from the time difference between the reception position and the transmission start position of the transmission start signal a.

Incidentally, the accurate receiving position of the reflected wave is originally
The position P ₀ in FIG. 4A is actually undetectable since the position P ₀ has a low signal level and is buried in noise. To do an accurate time measurement, reception position of the reflected wave, it is desirable to detect as a position as close as possible to the P ₀ position. For the present invention, since the signal level of the reflected wave RF signal k is detected as the reception position of the reflected wave a predetermined number before the position from the position where the steady state, detected as a value closer to P ₀ can do. On the other hand, in the case of the conventional device of FIG.
As shown in (B), the maximum level position of the reflected wave detection signal i must be detected as the received position of the reflected wave. For this reason, the present invention can detect the receiving position of the reflected wave with higher accuracy.

The snow depth calculation means 35 uses the temperature T sent from the AD conversion circuit 22 of the temperature measurement system 2 to determine the sound velocity V of the ultrasonic wave at that time from the above equation (1). Then, using the obtained sound velocity V and the reflection time t obtained as described above, the snow depth D at that time is calculated from the equation (2). The calculation result is output to the output circuit 4.
And output to an external display or the like to display or record in a desired format.

The reception level of the above-mentioned reflected wave detection signal i is the minimum judgment level L _MIN of the reception level judgment means 38 (FIG. 3).
If the signal level is too small to reach the value, the reception level determination means 38 determines whether the received signal level
0, the circuit gain of the reception gain control circuit 18 'is set to 2
When the reception level of the reflected wave detection signal i reaches the minimum judgment level L _MIN , the operation of increasing the gain is stopped, and thereafter, gain control using the above-described conversion table is performed. Move to By doing so, the gain control according to the present invention can be executed regardless of the small reception level.

When the circuit gain is increased to the minimum judgment level L _{MIN because} the reception level of the reflected wave is too small as described above, the conversion gain value in the conversion table is deviated by the increased gain. . Therefore, in order to prevent this, the increased gain value is stored in the table conversion means 3.
7 during the gain control operation using the conversion table thereafter.
A value obtained by subtracting the increased gain value from the converted gain value read from the received signal may be sent to the reception gain control circuit 18 '.

[0040]

As described above, according to the first aspect of the present invention, the storage means for converting the reflected wave from the monitoring area into digital data and storing the digital data, and determining the reception level of the stored reflected wave. Receiving level determination means, a table conversion memory storing a gain value corresponding to the received level of the reflected wave, and a received level of the reflected wave converted into a gain value by referring to a conversion table of the table conversion memory. A table conversion unit, a DA conversion circuit for converting a gain value formed from the converted digital data into an analog signal, and a reception gain control circuit for automatically setting a circuit gain to a gain value given from the DA conversion circuit. Thus, the conversion table can have an optimum gain value corresponding to the reception level of the reflected wave. Therefore, gain compensation can be performed in accordance with the attenuation characteristic of the reception level of the reflected wave that attenuates exponentially sharply, and the snow depth can be accurately measured in any weather condition.

According to the second aspect of the present invention,
Since the timing generation means for setting the gate time of the reception signal based on the reception timing signal from the reception level determination means is provided, it is possible to receive the reflected wave only for the minimum time necessary for the measurement, such as engine noise of a vehicle. The effect of external noise can be minimized and the snow depth can be measured more accurately.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of an ultrasonic snowfall meter according to the present invention.

FIG. 2 is an operation waveform diagram of each part of the circuit of FIG.

FIG. 3 is an explanatory diagram illustrating a relationship between a reception level and a threshold of a determination level.

FIG. 4 is an explanatory diagram of a method of detecting a reception timing in the case of FIG. 3;

FIG. 5 is a diagram illustrating the principle of an ultrasonic snowfall meter.

FIG. 6 is a block diagram of a conventional example.

FIG. 7 is an operation waveform diagram of each part of the circuit of FIG. 6;

FIG. 8 is a diagram illustrating attenuation characteristics of ultrasonic waves.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Propagation time measurement system 2 Temperature measurement system 3 Control part 4 Output circuit 10 DA conversion circuit 11 Pulse generation circuit 12 Oscillator 13 Burst wave generation circuit 14 Amplifier 15 Transmitter / receiver 16 Amplifier 17 'Detection circuit 18' Receiving gain control circuit 19 A / D conversion circuit 20 Temperature sensor 21 Amplifier 22 A / D conversion circuit 31 'Timing generation means 32 Received data storage means 33' Receiving time calculation means 34 Propagation time calculation means 35 Snow depth calculation means 36 Table conversion memory 37 Table conversion means 38 Receive Wave level judgment means

Claims (2)

[Claims] An ultrasonic snow meter that emits ultrasonic waves toward the ground and measures the time of reflection from the snow surface to measure the snow depth, wherein the reflected waves from the monitoring area are digitally measured. Storage means for converting and storing data; reception level determination means for determining the received level of the stored reflected wave; table conversion memory storing a gain value corresponding to the received level of the reflected wave; and table conversion. A table conversion means for converting the reception level of the reflected wave into a gain value by referring to a conversion table of a memory, a DA conversion circuit for converting a gain value formed from the converted digital data into an analog signal, and a circuit gain An ultrasonic snowfall meter, comprising: a reception gain control circuit that automatically sets a gain value given from the DA conversion circuit. 2. An ultrasonic snow gauge according to claim 1, further comprising timing generation means for setting a gate time of a reception signal based on a reception timing signal from said reception level determination means.