JPH0760187B2 - Road area snow depth meter - Google Patents

Description

The present invention relates to an apparatus for measuring snow depth on a road using ultrasonic waves.

[Conventional technology]

First, the principle of measuring the road area snow depth will be described. As shown in FIG. 2, an ultrasonic transmitter / receiver (hereinafter simply referred to as “transmitter / receiver”) 1 is attached at a position of 5 to 6 m on the road surface toward the road surface,
An ultrasonic pulse is emitted, and the time it takes for the ultrasonic wave to return from the snow surface on the road surface is measured. From this propagation time and the speed of sound, the distance between the snow surface and the handset can be measured. To determine the snow depth from this distance, the distance between the handset and the road surface is set in advance in the road area snow depth meter, and the difference between the set distance and the measured distance is calculated. Since the propagation speed of the sound wave depends on the temperature in the air, the temperature sensor 2 measures the temperature to correct the temperature.

FIG. 3 (a) shows a wave having a frequency of 26 kHz, a pulse width of 1 ms, and a transmission interval of 100 ms, for example, and FIG.
Is a direct wave and 1b is a reflected wave. Further, FIG. 3 (c) shows the time from the transmission of the ultrasonic pulse to the reception of the reflected wave, that is, the round-trip propagation time t of the ultrasonic pulse, and the snow depth is represented by the following equation (1). .

D = H- (Vt / 2) (1) where H (m) is the distance from the road surface to the handset 1, V
(M / s) is the speed of sound, and V is 3 when T is the temperature (° C).
It will be 31.45 + 0.61T.

[Problems to be solved by the invention]

In such measurement of the snow depth, noise such as horn engine noise of an automobile may be received between the waves shown in FIG. 3 (a). These noises are often received throughout the transmission,
There were cases where the snow depth was erroneously measured due to these noises.

The present invention has been made in view of such a point, and an object thereof is to provide a road area snow depth meter that does not make an erroneous measurement even in an environment where the above noise is generated. To get.

[Means for solving problems]

In order to solve such an object, according to the present invention, the first reception gate period provided after the transmission of the ultrasonic pulse and the first reception gate period after the transmission of the ultrasonic pulse overlap. A transmission / reception timing generating means for generating a second reception gate period provided in a non-retaining period, and a first according to a detection degree of a reception signal detected within the second reception gate period.
Valid signal deciding means for deciding validity / invalidity of the received signal detected within the receiving gate period of the above, and the received signal detected within the first receiving gate period when the effective signal deciding means decides to be valid And a snow depth calculation means for calculating the snow depth based on the above.

[Action]

In the road area snow depth meter according to the present invention, when a received signal is detected at a specific time, it is regarded as noise and the snow depth is not measured.

〔Example〕

FIG. 1 is a system diagram showing an embodiment of a road area snow depth meter according to the present invention. In FIG. 1, 1 is a transmitter / receiver, 2 is a temperature sensor, 3 is an input / output transformer, 4 is a transmitter / receiver drive circuit, 5 is a transmission / reception timing generation circuit as transmission / reception timing generation means, and 6 is a reception amplification circuit. , 7 is a receiving and detecting circuit, 8 is an A / D converting circuit, 9 is a CPU having an effective signal determining means 91 and a snow depth calculating means 92, 10 is an amplifier circuit for amplifying the output signal of the temperature sensor 2, and 11 is A / D conversion circuit, 12 is ROM,
Reference numeral 13 is a RAM, 14 is a clock generation circuit, 15 is a receiver mounting height setting switch, 16 is an output circuit for outputting snow depth data, and 17 is a snow depth indicator for displaying the snow depth.

4 is a time chart showing the signal waveforms in FIG. 1, FIG. 4 (a) shows a transmission timing signal a output from the transmission / reception timing generation circuit 5, and FIG. 4 (b) is a handset. The transmission signal b output from the drive circuit 4,
4 (c) is a received signal c output from the receiving amplifier circuit 6, FIG. 4 (d) is a received signal d containing a noise signal output from the receiving amplifier circuit 6, FIG. FIG. 4E shows the received wave detection signal e output from the received wave detection circuit 7, and FIG. 4F shows the first and second reception gate signals f output from the transmission / reception timing generation circuit.

Further, S1 in FIG. 4 (c) shows the waveform of the received signal c due to the reflected wave from the snow surface, S2 in FIG. 4 (d) shows the waveform of the noise signal, and S3 and S4 in FIG. 4 (f). Shows the waveforms of the first reception gate signal and the second reception gate signal.

The reception gate signal f in Fig. 4 (f) is 0 to 1 m deep.
The time t1 corresponds to the distance of 1 m from the handset 1, the time t2 corresponds to the distance of 1.5 m from the handset 1, the time t3 corresponds to the snow depth of 1 m, and the time t4 corresponds to the road surface position.

Next, the operation of the road area snow depth meter of FIG. 1 will be described with reference to the flowchart of FIG. First, ultrasonic waves are transmitted from the handset 1 (step 21). Next, the reflected wave of the ultrasonic wave is received, amplified by the reception amplification circuit 6 (step 22), and detected by the reception detection circuit 7. In step 23, the noise is measured and the noise is measured by the second reception gate signal shown in FIG. 4 (f). That is, the valid signal determining means 91 determines whether or not any signal is received during the second reception gate period (the period from time t1 to t) shown in step 24, and the reception signal is present within this second reception gate period. If the received signal does not exist, the process returns to step 21 (step 25). If there is no received signal, the process proceeds to step 27, and the received signal is detected by the reflected wave (step 26). This is because the second reception gate period is originally a period in which no reflected wave exists, and the presence of a signal in this period means that noise is generated. This second receiving gate period is focused on the fact that there is a time period during which the received signal due to the reflected wave does not enter from one transmission wave to the next transmission wave. This specific example is shown in FIG.

FIG. 7A shows a transmission timing, FIG. 7B shows a reception timing, FIG. 7C shows a reception signal, and FIG. 7D shows a time period during which the reception signal does not enter. In the example of FIG. 7, the time period during which no received signal is input is 6 ms to 9 ms. This time zone corresponds to a distance of 1 m to 1.5 m from the handset 1 having the waveform S4 shown in FIG. 4 (f). When the received signal is detected several times (1 to 10 can be arbitrarily set) during this time period, it is considered that there is a lot of noise, and the measurement is not performed at the transmission timing. In FIG. 7 (c), the gradually decreasing signal waveform S5 indicates the reverberation part,
S6 and S7 indicate reflected crawling and secondary reflected waves.

If there is a received signal, the process returns to the first step 21 without processing the received signal as shown in step 25, but if there is no received signal, the process proceeds to step 27 to process the received signal. First, in step 28, the start of the first reception gate is determined, and a waiting state is entered until the start. When the first reception gate period starts, the reception signal is A / D converted every 50 μs, and the RAM 13
(Step 29).

Next, when the first reception gate period ends (step 3
0), the reception time t of the reception signal stored in the RAM 13 is calculated (step 31), and the temperature T is detected by the temperature sensor 2 (step 32). Sound velocity V from temperature T to time t
To calculate. By substituting these values of V, t into the equation (1), the snow depth D is obtained (step 33).

Next, in step 34, valid / invalid data determination processing is performed. This purpose is to eliminate erroneous measurement due to vehicles etc. The method is D (1 to 99 can be arbitrarily set) cm from the past N (1 to 99 can be arbitrarily set) average value.
The measured values separated from each other are removed.

Next, in step 35, it is determined whether or not the data is valid.
Move to 37.

In step 36, snow depth statistical processing is performed. The purpose of this is to prevent the measured snow depth from fluctuating instantly due to wind and other disturbances. The method is
The oldest measured value and the latest measured value of the past N pieces of data determined to be valid are replaced with each other to obtain an average value, and this average value is used as the final output snow depth measurement value. The average value calculation method is the moving average value method.

In step 37, invalid data statistical processing is performed. This is intended to check for invalidity. The method calculates the variance when the data determined to be invalid reaches N times in succession, compares the variance of invalid data with the variance of valid data, and if the variance of invalid data is smaller, treats it as invalid data. It replaces valid data.

Next, the output circuit 16 outputs the display data to the snow depth indicator 17, and outputs the analog signal g and the digital signal h of the snow depth.

In the above-mentioned embodiment, the case of measuring the snow depth on the road has been described, but the present invention is not limited to this, and an ultrasonic level meter that does not need to rush the measurement once, for example, in a hopper at a civil engineering site. It is clear that it is effective for ultrasonic level meters for the purpose of measuring the amount of rock.

〔The invention's effect〕

As described above, the present invention is provided in the first reception gate period provided after the transmission of the ultrasonic pulse and the period after the transmission of the ultrasonic pulse and which does not overlap with the first reception gate period. And a reception / transmission timing generating means for generating the second reception gate period, and a reception detected within the first reception gate period according to the degree of detection of the reception signal detected within the second reception gate period. A valid signal determining means for determining validity / invalidity of a signal, and a snow depth for calculating a snow depth based on a reception signal detected within the first reception gate period when the validity signal determining means determines that the snow depth is valid. By providing the calculation means, correct measurement can be performed without erroneous measurement due to noise, and thus there is an effect that road management in a snowy state can be efficiently performed.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of a road area snow depth meter according to the present invention, FIGS. 2 and 3 are explanatory diagrams and time charts for explaining the principle of road area snow depth measurement, and FIG. A time chart for explaining the operation of the apparatus of FIG. 1, FIGS. 5 and 6 are flow charts for explaining the operation of the apparatus of FIG. 1, and FIG. 7 is for explaining the time zone of the second receiving gate. It is a time chart for. 1 ... Transceiver, 2 ... Temperature sensor, 3 ... Input / output transformer, 4 ... Transceiver drive circuit, 5 ... Transmission / reception timing generation circuit, 6 ... Reception amplification circuit, 7 ... Reception detection Circuit, 8,
11 ... A / D conversion circuit, 9 ... CPU, 10 ... amplification circuit, 12 ...
… ROM, 13 …… RAM, 14 …… Clock generator, 15 …… Transmitter mounting height setting switch, 16 …… Output circuit, 17 ……
Depth of snow indicator.

Claims (1)

[Claims] 1. A road area snow depth meter for measuring a road area snow depth based on a round-trip propagation time of an ultrasonic pulse, wherein a first reception gate period provided after the ultrasonic pulse is transmitted and after the ultrasonic pulse is transmitted. And a transmission / reception timing generation means for generating a second reception gate period provided in a period that does not overlap the first reception gate period, and detection of a reception signal detected within the second reception gate period. A valid signal determining means for determining validity / invalidity of a reception signal detected within the first reception gate period according to the degree, and a first signal when the validity signal determining means determines that the reception signal is valid.
And a snow depth calculation means for calculating a snow depth based on a reception signal detected within the reception gate period of the road area snow depth meter.