JP2005233640A - Distance measurement method by ultrasonic wave air sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a distance measurement method by ultrasonic wave air sensor installed in the air capable of measuring the distance to the measurement object always precisely. <P>SOLUTION: The distance measurement method by ultrasonic wave air sensor for measuring the distance L from the ultrasonic wave sensor 4 installed in the air to the free surface of the drainage water 2 (object to be measured) based on the time from the ultrasonic wave transmitted from the ultrasonic sensor 4 and returns to the same after reflected by the free surface of the drainage water 2. The ultrasonic sensor 4 is air washed and its transmission/reception surface is dried, and after that the standard target 7 is inserted on the course of the ultrasonic waves in a known distance, then the standard distance LS from the ultrasonic sensor 4 to the target is measured. By measuring the intensity of the reflected ultrasonic waves, the contamination and the precision of the ultrasonic sensor 4 is confirmed, then, the distance L is measured. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a distance measuring method for measuring a distance to an object to be measured using an ultrasonic sensor installed in the air.

  For example, a triangular weir is known as a means for measuring the flow rate of liquid. This triangular weir measures the height of the upstream liquid surface and the upper edge (weir edge) of the weir (weir head), Thereby, the flow rate of the liquid is measured.

  By the way, in the flow rate measurement by such a triangular weir, the head of the weir is measured by an ultrasonic sensor. In this case, the ultrasonic sensor is installed in the air above the triangular weir, measures the time until the ultrasonic wave transmitted from the ultrasonic sensor is reflected on the liquid surface and returns, and based on that time It detects the height to the water surface. In addition, the technique which measures the height to a liquid level with the ultrasonic sensor installed in the air in this way is utilized in various fields (for example, refer patent document 1).

Japanese Patent Laid-Open No. 5-322721

  However, in the method of measuring the distance to the liquid level with an ultrasonic sensor installed in the air, if a water drop or a foreign object adheres to the transmission / reception surface of the ultrasonic sensor, the ultrasonic wave is refracted by the water drop and the distance to the liquid level. There was a problem that it was impossible to measure accurately. For example, when measuring the head of a weir with an ultrasonic sensor in a triangular weir, if water droplets or foreign matter adhere to the transmission / reception surface of the ultrasonic sensor, the head of the weir is not accurately measured and is calculated based on the head of this weir. There was a problem that an error occurred in the flow rate of the liquid.

  The present invention has been made in view of the above problems, and an object thereof is an ultrasonic aerial sensor that can always measure the distance to an object to be measured with an ultrasonic sensor installed in the air with high accuracy. The object is to provide a distance measuring method.

  In order to achieve the above object, the invention according to claim 1 measures the time until the ultrasonic wave transmitted from the ultrasonic sensor installed in the air is reflected by the object to be measured and returns. In the distance measurement method using an ultrasonic aerial sensor that measures the distance from the ultrasonic sensor to the object to be measured based on the ultrasonic wave path after the ultrasonic sensor is washed with air and the transmitting / receiving surface is dried The standard target is inserted into a position at a known distance, the distance between this and the ultrasonic sensor is measured, and the error is detected by measuring the reflection intensity of the ultrasonic wave to measure the contamination of the ultrasonic sensor. It is characterized by measuring after confirming the accuracy.

  According to a second aspect of the present invention, in the first aspect of the present invention, when an error is detected by the error detection, the ultrasonic sensor is liquid-washed and then air-washed to dry its transmitting / receiving surface, and then again. It is characterized in that measurement is performed after error detection is performed and contamination of the ultrasonic sensor and measurement accuracy are confirmed.

  According to the first aspect of the invention, before the original measurement (measurement of the distance to the object to be measured) by the ultrasonic sensor is performed, the measurement accuracy and dirt of the ultrasonic sensor are reduced by error detection using a standard target. Since the confirmation (confirmation that the accuracy of the ultrasonic sensor is high and there is no contamination on the transmission / reception surface of the ultrasonic sensor), the distance to the object to be measured by the ultrasonic sensor is always highly accurate. Can be done.

  According to the second aspect of the present invention, when an error is detected in the error detection, the dirt adhering to the transmission / reception surface of the ultrasonic sensor causing the error is removed by liquid cleaning, and the liquid cleaning is performed. Since the water droplets adhering to the transmission / reception surface of the ultrasonic sensor are evaporated and dried by air cleaning, the error state can be quickly eliminated and a highly accurate distance measurement by the ultrasonic sensor can be realized.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. In addition, the following shows an example of the embodiment of the present invention, and the scope of the present invention is not limited thereby.

  1 is a cross-sectional view of a water channel showing a flow rate measurement method using a triangular weir, FIG. 2 is a front view of the triangular weir, and FIG. 3 is a side view showing a state in which the distance to the water surface is measured in the distance measuring method according to the present invention. 4 is a side view showing a state when an error is detected in the distance measuring method according to the present invention, and FIGS. 5A to 5C are side views showing the state of the lower surface (transmission / reception surface) of the ultrasonic sensor.

  1 and 2, reference numeral 1 denotes a water channel (opening) having a rectangular cross-section with an open upper surface. In this water channel 1, a liquid such as a slurry containing a figure or solid matter, for example, a waste water 2 containing sludge is contained. Flowing. A triangular weir 3 is provided at the end of the water channel 1, and the drainage 2 passes through the triangular weir 3 and is discharged out of the water channel 1.

  Here, as shown in FIG. 2, the triangular weir 3 has an inverted triangular notch with an apex angle α (α = 90 ° in the present embodiment) as a weir, and two sides 2a sandwiching the corner as a thin blade. As shown in FIG. 1, the drainage 2 that is configured and flows through the water channel 1 is squeezed when passing through the triangular weir 3 to be jetted and discharged out of the water channel 1.

  Thus, the flow rate Q of the drainage 2 over the triangular weir 3 is determined by measuring the weir head h which is the vertical distance from the weir edge 3b of the triangular weir 3 to the free surface of the drainage 2 (upstream water level). It is calculated by the formula.

^{Q = Kh 5/2 ... (} 1)
(K: Flow coefficient)
By the way, in the present embodiment, the head h of the weir is formed by an ultrasonic air sensor (hereinafter simply referred to as an ultrasonic sensor) 4 installed above the drainage 2 upstream of the triangular weir 3. This is obtained by measuring the distance L from the acoustic wave sensor 4 to the free surface of the drainage 2, and the state is shown in FIG.

  That is, when ultrasonic waves are transmitted from the ultrasonic sensor 4 at regular time intervals, the ultrasonic waves are reflected by the free surface of the drainage 2 and received by the ultrasonic sensor 4. Propagation time) t is measured by a measuring means (not shown), and the distance L from the ultrasonic sensor 4 to the free surface of the drainage 2 is calculated by the following formula by a calculating means (not shown) based on the measured time t. Is done.

L = a × t / 2 (2)
(A: speed of sound)
Here, since the distance L ₀ from the ultrasonic sensor 4 shown in FIG. 1 to the weir edge 3b of the triangular weir 3 is known, the head h of the weir is obtained by the following equation.

h = L ₀₋ L (3)
In the present embodiment, a commercially available product of HD500 manufactured by Honda Electronics Co., Ltd. is used as the ultrasonic sensor 4, and the outer diameter of the lower surface, which is the transmission / reception surface, is 32 mm.

  By the way, as shown in FIG. 5A, when the water droplet 5 adheres to the lower surface, which is the transmitting / receiving surface of the ultrasonic sensor 4, the ultrasonic wave is refracted by the water droplet 5, and the distance L to the free surface of the drainage 2 is accurately set. It cannot be measured.

  Therefore, in this embodiment, as shown in FIGS. 3 and 4, an injection nozzle 6 is provided in the vicinity of the ultrasonic sensor 4, and a standard target 7 for detecting a measurement error is rotated around its axis 7a. It was provided to be movable.

  Here, the jet nozzle 6 is bent at an acute angle so that the tip thereof is directed to the lower surface, which is the surface to be cleaned of the ultrasonic sensor 4, and a compressor (not shown) for supplying compressed air or the like A pump (not shown) for supplying clean washing water is selectively connected by the switching means.

Further, the standard target 7 has a shielding portion 7b attached horizontally to the lower end portion of the shaft 7a, and the ultrasonic sensor 4 measures the distance L to the free surface of the drainage 2 in FIG. In the state shown, the standard 7 shielding portion 7b is retracted to a position where the ultrasonic wave transmitted from the ultrasonic sensor 4 is not blocked as shown in the figure. Here, the distance L _S from the ultrasonic sensor 4 to the standard target 7 shielding portion 7b is set in advance to a predetermined value (for example, 1 m), and this value is the value of the ultrasonic sensor 4 when an error is detected. This is a reference value for determining accuracy.

  Next, a distance measuring method according to the present invention will be described with reference to a flowchart shown in FIG.

  Before starting the measurement of the distance L, first, compressed air is supplied from an unillustrated compressor to the injection nozzle 6, and the compressed air is injected from the injection nozzle 6 to adhere to the lower surface of the ultrasonic sensor 4. 5 (see FIG. 5A) is evaporated, and the lower surface of the ultrasonic sensor 4 is washed with air and dried (step S1). Thereafter, as shown in FIG. 4, the standard target 7 is rotated 180 ° around its axis 7 a, and the shielding part 7 b is located below the ultrasonic sensor 4 (position where the ultrasonic wave transmitted from the ultrasonic sensor 4 is blocked). Then, error detection is started (step S2).

In the error detection, as shown in FIG. 4, the distance from the ultrasonic sensor 4 to the standard target 7 shielding portion 7 b is measured by the ultrasonic sensor 4. That is, the ultrasonic wave transmitted from the ultrasonic sensor 4 is reflected by the shielding part 7b and received by the ultrasonic sensor 4, but the time (ultrasonic propagation time) t until that time is measured by a measuring means (not shown). Then, based on the measured time t, the distance from the ultrasonic sensor 4 to the shielding part is calculated by the equation (2). Here, the distance actually measured by the ultrasonic sensor 4 is defined as L _S ′.

Then, the obtained distance (actually measured distance) L _S ′ is compared with a preset reference value L _S, and whether the error ΔL _S (= | L _S ′ −L _S |) is less than the allowable value. Whether or not dirt is attached to the lower surface, which is the transmitting / receiving surface of the ultrasonic sensor 4, is visually determined (step S3).

When the error ΔL _S is less than the allowable value and no dirt is attached to the lower surface of the ultrasonic sensor 4 (when the determination result in step S3 is YES), the ultrasonic reflection intensity is the reference value. In comparison with the above, it is determined whether the ultrasonic sensor 4 is deteriorated (step S4). That is, if the reflection intensity error is within the allowable range, it is determined that the error is normal, and if it is outside the allowable range, it is determined that the ultrasonic sensor 4 has deteriorated, and an alarm is output.

  If it is determined to be normal in step S4 (if the determination result in step S4 is YES), the standard target 7 is rotated 180 ° around its axis 7a from the state shown in FIG. As shown, after the shield 7b is retracted from below the ultrasonic sensor 4, the distance L from the ultrasonic sensor 4 to the free surface of the drainage 2 is measured by the above method (step S5).

On the other hand, when the error ΔL _S exceeds the allowable value (when the determination result in step S3 is NO), the result of air cleaning shown in FIG. As shown in FIG. 5 (b), it is determined that dirt 8 remains on the lower surface of the ultrasonic sensor 4 and the connection of the injection nozzle 6 is switched to the pump, and clean water is supplied from the pump to the injection nozzle 6. Then, as shown in FIG. 5B, clean water is jetted from the jet nozzle 6 to remove dirt 8 such as sludge adhering to the lower surface of the ultrasonic sensor 4 by water washing (step S6).

  Next, the connection of the injection nozzle 6 is switched again to the compressor, compressed air is supplied from the compressor to the injection nozzle 6, and as shown in FIG. The water droplet (water droplet of washing water) 9 adhering to the lower surface of 6 is evaporated, and the lower surface of the ultrasonic sensor 4 is washed with air and dried (step S1). In the present embodiment, the air and water are jetted from one jet nozzle 6 by switching. However, the jet nozzles for air jet and water jet may be provided independently. In the present embodiment, water is jetted from the jet nozzle 6 when an error is detected. However, other liquids such as alcohol or carbon dioxide saturated water may be jetted. good.

Thereafter, error detection is performed in the same manner as described above (step S2), and water cleaning, air cleaning, and error detection are performed until the error ΔL _S is less than an allowable value and no contamination is observed on the lower surface of the ultrasonic sensor 4. Is repeated (step S3 → step S6 → step S1 → step S2), and when the error ΔL _S is less than the allowable value and no contamination is observed on the lower surface of the ultrasonic sensor 4, as shown in FIG. The distance L from the ultrasonic sensor 4 to the free surface of the drainage 2 is measured by the above method through the deterioration determination process of the ultrasonic sensor 4 in step S4 (step S5).

  The above operation is repeated until the measurement is completed (step S7). In this embodiment, the standard measurement is performed before the original measurement (measurement of the distance L to the free surface of the drainage water 2) by the ultrasonic sensor 4. The measurement accuracy and dirt of the ultrasonic sensor 4 are confirmed by error detection using 7 (confirm that the precision of the ultrasonic sensor 4 is high and no dirt adheres to the lower surface of the ultrasonic sensor 4). Therefore, the distance L to the free surface of the drainage 2 by the ultrasonic sensor 4 can always be measured with high accuracy, and the head h of the weir is accurately calculated by the equation (3) based on the measured distance L. Based on the head h of this weir, the flow rate Q of the drainage 2 can be accurately obtained by the equation (1).

  In this embodiment, when an error is detected in the error detection, the dirt 8 (see FIG. 5B) adhering to the lower surface of the ultrasonic sensor 4 causing the error is washed with water. The water droplets 9 (see FIG. 5C) adhering to the lower surface of the ultrasonic sensor 4 by this water cleaning are evaporated and dried by air cleaning, so that the error state is quickly eliminated and the ultrasonic sensor 4 can realize the measurement of the distance L with high accuracy.

  The present invention is not only for measuring the flow rate with a triangular weir, but also for measuring the distance to any object to be measured using an ultrasonic sensor installed in the air, such as the water level of a water tank or pool, the water level of various tanks, etc. It can be widely used for the method of measuring.

It is sectional drawing of the water channel which shows the flow measurement method by a triangular weir. It is a front view of a triangular weir. It is a side view which shows the state which is measuring the distance to the water surface in the ranging method which concerns on this invention. It is a side view which shows the state at the time of the error detection in the distance measuring method which concerns on this invention. (A)-(c) is a side view which shows the state of the lower surface (transmission-and-reception surface) of an ultrasonic sensor. It is a flowchart which shows the procedure of this invention method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Waterway 2 Drainage 3 Triangular weir 4 Ultrasonic sensor 5 Water drop 6 Injection nozzle 7 Standard target 7a Shaft 7b Shielding part 8 Dirt 9 Water drop

Claims (2)

Measures the time until the ultrasonic wave transmitted from the ultrasonic sensor installed in the air is reflected by the measured object and returns, and measures the distance from the ultrasonic sensor to the measured object based on that time In the distance measurement method using an ultrasonic air sensor,
After the ultrasonic sensor is cleaned with air and its transmitting / receiving surface is dried, a standard target is inserted at a known distance on the path of the ultrasonic wave to measure the distance between the ultrasonic sensor and the ultrasonic sensor. A distance measuring method using an ultrasonic aerial sensor, wherein an error is detected by measuring the reflection intensity of ultrasonic waves, and measurement is performed after confirming contamination and measurement accuracy of the ultrasonic sensor.   If an error is detected by the error detection, the ultrasonic sensor is washed with liquid and then air-washed to dry its transmitting / receiving surface, and then error detection is performed again to check the contamination and measurement accuracy of the ultrasonic sensor. 2. The distance measuring method using an ultrasonic air sensor according to claim 1, wherein the measurement is performed after the measurement.

Images