JP2869692B2 - Ultrasonic snow depth measuring method and ultrasonic snow depth measuring device. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a snow depth measuring method for measuring snow depth by ultrasonic waves and a snow depth measuring device using the method.

[0002]

2. Description of the Related Art Conventionally, snow depth measurement is performed by intermittently transmitting a short-time pulsed ultrasonic wave and receiving a reflected wave from the surface of the snow, from the time of transmission of the ultrasonic wave to the time of reception. A method of measuring the depth of snow cover based on detection of a time difference until time has been developed and widely used. (Hereinafter, this method will be referred to as a "pulse radar method.") For example, the publication number 52-36714
"Snow gauge", Publication number 56-29922 "Ultrasonic snow measurement apparatus", Publication number 58-33042 "Snow level meter", Publication number 62-171159 "Snow depth measurement apparatus", Publication number 62-231204 "Street area snow depth" That is the total.

[0003]

[Technical Problems to be Solved] In the pulse radar system, it is fundamental to accurately detect the rising point of the received signal. However, in snow cover, the reflectivity of ultrasonic waves due to snow quality, such as fresh snow and closed snow, differs greatly, and interference of sound waves occurs due to unevenness of the snow surface, so the amplitude change of the received signal is large and the waveform is extremely It is indefinite. Therefore, as seen in the above-described conventional example, various measures such as reception level correction, noise suppression, average value processing, and maximum / minimum judgment processing have been devised. However, the circuit and waveform processing become complicated, and soft snow during snowfall is reduced. However, there is a problem that the operation may be unstable.

[0004] In particular, in the pulse radar system, when the level of a received signal is reduced due to the influence of snow quality, the S / N is deteriorated, and processing for removing noise in the received signal becomes complicated. . Also, interference of sound waves occurs due to irregularities on the surface of the snow, and the waveform of the reflected wave changes irregularly in a beat shape. Therefore, it is often difficult to specify the rising point of the received signal. The present invention has been made in order to solve the above-described problems, and an object of the present invention is to provide a device capable of accurately measuring the snow depth without being affected by the snow quality or the condition of the snow surface. Aim.

[0005]

[Means for Solving the Problems] The inventor of the present invention has conducted intensive studies to solve the problems. As a result, when a system in which a continuous wave subjected to FM modulation is used as a transmission and reception wave is used, the reception level greatly fluctuates first. Even when the signal fluctuates irregularly in the form of a beat, the signal is demodulated through the high-gain saturation amplifier circuit to perform S / N.
That a modulated wave signal with a stable amplitude can be obtained without deterioration, and a phase difference between the transmitted and received waves of the modulated wave signal can be measured stably. Second, due to the influence of sound wave interference due to unevenness of the snow-covered surface. Although the phenomenon in which the phase of the modulated signal when the demodulated changes occur, this phenomenon is a reference positive
A signal obtained by adding a low-frequency triangular wave signal to a sine wave signal is a modulated wave signal
When the frequency (carrier frequency) of the ultrasonic wave when the FM modulation is applied to this signal is continuously changed, the phase of the received modulated wave signal becomes a low frequency centered on the phase difference corresponding to the distance from the snow surface. A new finding was confirmed that it changes periodically with the cycle of the triangular wave signal . The inventor has developed the following ultrasonic snow depth measuring method and ultrasonic snow depth measuring device based on this new knowledge.

A first invention to be patented is to modulate a signal obtained by adding a triangular wave signal to a reference sine wave signal.
An ultrasonic wave multiplied by the FM modulation to transmit to the snow surface as an issue,
The reception signal receives a reflected wave from the snow surface after having FM demodulation, to remove low-frequency triangular wave signal by the band pass filter
Give the reception sine wave signal, a sine wave signal and the received wave underlying
The phase difference from the sine wave signal is measured, the average value of the phase difference of the sine wave signal is obtained at the cycle of the triangular wave signal, the distance from the ultrasonic wave propagation speed to the snow surface is obtained, and the height of the ultrasonic transducer is measured. This is an ultrasonic snow depth measurement method that measures the depth of snow from the difference between the two.

The second invention to be patented is a means for oscillating a reference sine wave signal and a signal obtained by adding a triangular wave signal to the reference sine wave signal as a modulation wave signal.
The ultrasonic frequency triangular wave signal when multiplied by the FM modulation to
Means for FM modulation so as to continuously change at the cycle of the signal, ultrasonic wave transmitting means for transmitting ultrasonic waves to the snow surface, ultrasonic wave receiving means for receiving reflected waves from the snow surface, Means for FM demodulating the received signal to a sine wave signal, means for comparing the phase of the sine wave signal of the received signal with the reference sine wave signal and measuring the phase difference, and means for changing the period of the triangular wave signal From the means for calculating the average value of the phase difference of the sine wave signal and the means for determining the distance to the snow surface from the propagation speed of the ultrasonic wave and further measuring the depth of the snow from the difference with the height of the ultrasonic transducer An ultrasonic snow depth measuring apparatus characterized in that:

[0008] A third invention to be patented is a sine wave oscillation circuit for generating a reference sine wave signal, a triangular wave oscillation circuit for generating a low frequency triangular wave signal, an oscillated reference sine wave signal and a triangular wave signal. Circuit that adds a signal to a modulated wave signal, an FM modulation circuit that FM-modulates the modulated wave signal, and an ultrasonic wave transmission device that includes a drive circuit that transmits an ultrasonic wave that has been subjected to FM modulation to a snow-covered surface. a vessel, and ultrasonic receiver which receives a reflected wave from the snow surface, an amplifier circuit to saturate amplifying a receive signal, an FM demodulation circuit for demodulating the FM-modulated, reception
A modulated signal obtained by FM demodulation of a signal through a saturation amplifier
And Luo low a frequency triangular wave signal to remove band-pass filter to a sine wave signal, compares the phases of the sine wave signal and the reference sine wave signal of received signal, a logic signal to provide a pulse width proportional to the phase difference A phase comparison circuit to be obtained, a clock signal oscillation circuit for detecting the temperature at the time of measurement by a temperature sensor to control the oscillation frequency, and giving an AND condition between the clock signal and a logic signal to give a clock number proportional to the phase difference. An AND circuit that obtains a phase difference proportional clock signal and a trigger signal that outputs the phase difference proportional clock signal at the cycle of the low frequency triangular wave signal are counted, and the counting result is the ratio of the reference sine wave signal to the low frequency triangular wave signal. The average value of the phase difference is obtained by dividing by the average value of the phase difference, the distance from the ultrasonic wave propagation velocity to the snow surface is obtained from the average value of the phase difference, and the difference from the height of the ultrasonic transducer is obtained. An ultrasonic snow depth measuring device comprising a snow depth computing circuit for measuring the depth of snow.

The present invention is different from the prior art in that the ultrasonic FM
The first characteristic is that the modulated continuous wave is transmitted and received. After the received signal is FM-demodulated, the phase difference between the transmission signal and the reception signal of the sine wave signal is measured, and the phase difference is measured at a predetermined period. The second feature is that the average value of the phase difference is obtained, and thereby, the influence of interference is reduced and accurate and stable measurement can be performed.

As an embodiment of the present invention, as a means for continuously changing the frequency of an ultrasonic wave, a low frequency triangular wave signal is added to a sine wave modulated wave signal, and an FM-modulated ultrasonic wave is transmitted and received. After demodulating the wave signal by FM, the triangular wave signal is removed, the phase difference between the transmission signal and the reception signal of the sine wave signal is measured, and the average value of the phase difference of the sine wave signal is calculated at the cycle of the triangular wave signal. The feature is that the influence can be reduced and accurate measurement can be performed.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram of a measuring circuit in an ultrasonic snow depth measuring apparatus. FIG. 2 is a diagram showing an installation state and a measurement state of the ultrasonic snow depth apparatus, 6 is an ultrasonic transmitter,
Reference numeral 9 denotes an ultrasonic wave receiver, which is installed at a height of H from the ground surface 8. In the figure, reference numeral 7 denotes an uneven snow surface. Assuming that the phase difference (time conversion value) between the transmitted wave and the received wave is t, the sound velocity at a temperature of 0 ° C. is v0, and the temperature at the time of measurement is T, the snow depth D is D = H−0.5t (v0 + 0. 607T) (1). By measuring H, t, v0, and T, the snow depth D can be obtained. FIG. 3 is a signal waveform diagram for explaining the operation of the circuit shown in FIG.

An ultrasonic snow depth measuring method and an ultrasonic snow depth measuring apparatus therefor will be described below with reference to a measurement circuit block diagram of FIG. 1 and a signal waveform diagram for explaining the operation of the circuit of FIG. 1 is a sine wave oscillation circuit that generates a reference sine wave signal a for measuring a phase difference,
In the embodiment, when the measurement range of the snow depth is 5 m, the oscillation frequency is 30 Hz.

Reference numeral 2 denotes a triangular wave generating circuit for generating a low frequency triangular wave signal b for continuously changing the frequency of the ultrasonic wave.
128).

The addition circuit 3 adds the sine wave signal and the triangular wave signal to generate a modulation wave signal c, and the FM modulation circuit 4 performs FM modulation with the modulation wave signal c using the vibration center frequency of the ultrasonic transmitter as the carrier frequency. .

The power is amplified by the driving circuit 5, and the ultrasonic wave transmitter 6 is driven to transmit the ultrasonic wave d subjected to the FM modulation to the snow surface 7.

The reception signal e, which is obtained by receiving the ultrasonic wave reflected from the snow surface 7 by the ultrasonic wave receiver 9 and saturating and amplifying it by the reception amplifier circuit 10, is demodulated by the FM demodulation circuit 11 and the band pass filter 12 Removes the low frequency triangular wave signal b to obtain a sine wave signal f for measuring the phase difference.

The phase comparison circuit 13 compares the phase difference between the reference sine wave signal a and the sine wave signal f of the received signal to obtain a logic signal g giving a pulse width proportional to the phase difference.

In the figure, reference numeral 14 denotes a clock signal oscillating circuit. The clock signal oscillating circuit 14 can detect a temperature T at the time of measurement by a temperature sensor 15 and control the oscillation frequency to correct a change in sound speed due to the temperature. Assuming that the proportionality constant is K, the oscillation frequency fa is given by: fa = K (v0 + 0.607T) (2) In the embodiment, the temperature is 166 kHz at 0 ° C.
z.

In the figure, reference numeral 16 denotes an AND circuit.
The circuit 16 obtains a phase difference proportional clock signal h that provides a clock number proportional to the phase difference by taking an AND condition of the logic signal g that provides a pulse width proportional to the phase difference with the clock signal.

In the figure, reference numeral 17 denotes a snow depth calculation circuit. In the snow depth calculation circuit 17, a trigger signal i for outputting a signal h for giving a clock number proportional to the phase difference at a period of the low frequency triangular wave signal b is also provided. And the result of the counting is divided by the ratio of the reference sine wave signal a to the low frequency triangular wave signal b (128 in the embodiment) to obtain the phase difference between the reference sine wave signal a and the sine wave signal f between the received signal and the received signal. Can be obtained. In the embodiment, the average value is 1 mm per clock.
become. Further, by subtracting the average value from the value of the installation height H of the ultrasonic transducers 6, 9, the snow depth D is obtained, and the result is output to the output terminal 18.

FIG. 3 is a signal waveform diagram for explaining the operation of the circuit. In FIG. 3, a is a reference sine wave signal, b is a low frequency triangular wave signal, and c is a modulation obtained by adding a sine wave signal and a triangular wave signal. Wave signal, d is an ultrasonic wave with FM modulation, e is a received signal,
f is a sine wave signal of the received signal, g is a logical signal giving a pulse width proportional to the phase difference, h is a phase difference proportional clock signal giving a clock number proportional to the phase difference, and i is a low frequency triangular wave signal b. This is a trigger signal output in a cycle.

[0023] Figure 4 is a measurement result of snow depth in the embodiment of the present invention, the measurement value j, when the average value was obtained was added a triangular wave signal to a sine wave modulation signal, measured value k is a modulated wave signal
Is a measurement result when only a sine wave signal is used and a triangular wave signal is not added. Only a sine wave signal as the modulated wave signal
In the case of a measurement value when a triangular wave signal is not added and is used, the width is as large as about 20 mm and is unstable. However, when a triangular wave signal is added to a sine wave modulation signal and the average value is obtained, the width of the measured value j is At 1 mm or less, there is almost no influence of sound wave interference. As is clear from the comparison between the two, the measured value j indicates that the effect of reducing the influence of sound wave interference is remarkable.

[0024]

As described above, the first, second, and third inventions of the present invention each have a case in which the reception level of the ultrasonic wave fluctuates greatly due to snow quality or interference, or changes irregularly in a beat shape. But S
Since the FM modulation / demodulation method is capable of obtaining a modulated wave signal having a stable amplitude without deteriorating / N, the phase difference between the transmission and reception of the modulated wave signal can be stably measured.

According to the first and second aspects of the present invention, the phenomenon that the phase of a modulated wave signal changes when demodulated due to the influence of snow quality or sound wave interference is caused by adding a triangular wave signal to the modulated wave signal, With a simple circuit configuration that calculates the average value of the phase difference of the sine wave signal, the effect of interference can be reduced and accurate measurement can be performed, and the measured value has a remarkable effect of reducing the effect of sound wave interference. .

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of an ultrasonic snowfall measuring device.

FIG. 2 is a diagram showing an installation state of an ultrasonic snow depth measuring device.

FIG. 3 is a signal waveform diagram for explaining the operation of the circuit shown in FIG. 1;

FIG. 4 is a diagram showing a measurement result of a snow depth in an example.

[Explanation of major symbols]

 DESCRIPTION OF SYMBOLS 1 Sine wave oscillation circuit 2 Triangular wave generation circuit 3 Addition circuit 4 FM modulation circuit 5 Drive circuit 6 Ultrasonic wave transmitter 7 Snow covered surface 8 Ground surface 9 Ultrasonic wave receiver 10 Reception amplification circuit 11 FM demodulation circuit 12 Band pass filter 13 phase comparison circuit 14 clock signal oscillation circuit 15 temperature sensor 16 AND circuit 17 snow depth calculation circuit 18 output terminal

Continuation of the front page (72) Inventor Yoshiaki Maebashi 3-9 Izumi-ku, Izumi-ku, Sendai-shi Izumi Part-Town Industrial and Distribution Complex Tsuken Electric Industry Co., Ltd. In-house (58) Field surveyed (Int. Cl. ⁶ , (DB name) G01W 1/14

Claims (3)

(57) [Claims] 1. A ultrasonic waves the addition signal of the triangular wave signal to the reference becomes sine wave signal subjected to FM modulation by the modulation wave signal to transmit to the snow surface and receives a reflected wave from the snow surface After FM demodulation of the received signal , the low-frequency triangular wave signal is removed by a band-pass filter to obtain a received sine wave signal.
Comprising measuring the phase difference between the sine wave signal and the received wave sine wave signal, the average value of the phase difference of the sinusoidal signal at the period of the triangular wave signal determines the distance from the propagation speed of the ultrasonic up snow surface, An ultrasonic snow depth measurement method that measures the depth of snow from the difference between the height of the ultrasonic transducer and the height. 2. A means for oscillating a reference sine wave signal, and a signal obtained by adding a triangular wave signal to the reference sine wave signal.
Is a modulated wave signal and FM modulation is applied to this signal.
Means for FM modulation so that the frequency of the sound wave changes continuously at the cycle of the triangular wave signal, ultrasonic wave transmitting means for transmitting ultrasonic waves to the snow surface, and ultrasonic waves for receiving reflected waves from the snow surface and reception means, means for measuring and means for the FM-demodulating the received signal sine wave signal, compares the phases of the sine wave signal as a sine wave signal and the reference of the received signal and the phase difference, a triangular wave
Means for calculating the average value of the phase difference of the sine wave signal that changes with the signal period, and the distance to the snow surface from the propagation speed of the ultrasonic wave, and the depth of the snow from the difference with the height of the ultrasonic transducer And a means for measuring snow depth. 3. A sine wave oscillating circuit for generating a reference sine wave signal, a triangular wave oscillating circuit for generating a low frequency triangular wave signal, and adding the oscillated reference sine wave signal and the triangular wave signal to form a modulated wave signal. An adder circuit and the modulated wave signal
An FM modulation circuit for modulating, an ultrasonic transmitter having a drive circuit for transmitting ultrasonic waves subjected to FM modulation to a snow surface, and an ultrasonic receiver for receiving a reflected wave from the snow surface. ,
An amplifier circuit to saturate amplifying a receive signal, an FM demodulation circuit for demodulating the FM-modulated, the received signal through the saturated amplifier F
A band-pass filter that removes a low-frequency triangular wave signal from a modulated wave signal that has been M-demodulated to a sine wave signal, compares the phase of the sine wave signal of the received signal with the phase of the reference sine wave signal, and makes a pulse proportional to the phase difference. A phase comparison circuit for obtaining a logic signal giving a width;
A clock signal oscillation circuit for controlling the oscillation frequency by detecting the temperature at the time of measurement by the temperature sensor; Counting based on the obtained AND circuit and a trigger signal that outputs the phase difference proportional clock signal at the cycle of the low frequency triangular wave signal,
By dividing the counting result by the ratio of the reference sine wave signal and the low-frequency triangular wave signal, an average value of the phase difference is obtained. An ultrasonic snow depth measuring device comprising: a snow depth calculating circuit for measuring a snow depth from a difference between a height of a transducer and a height of the transducer.