JPH10325870A - Ultrasonic range finder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately measure a distance up to a measuring object regardless of the existence of ultrasonic reflection on a floating matter, by setting the range from transmission of ultrasonic wave to attenuation of its reflected wave as the time required for receiving the reflected wave from the objective. SOLUTION: A time measuring means 4 clocks an elapsed time of transmission of an ultrasonic wave to reception of a reflected ultrasonic wave by an ultrasonic sensor 3, and an operation means 12 calculates a distance up to a measuring object on the basis of the measuring time and ultrasonic velocity. At this time, a transmission completion time detection part 6 detects the transmission completion of the ultrasonic wave by the ultrasonic sensor 3, and a reflection ultrasonic attenuation detection part 8 detects the attenuation for the preset amplitude of the reflection ultrasonic wave from the measuring object. A clocking control part 10 sets the detection times of both the detection parts 6, 8 to clocking start and clocking end. Thus, the completion of reception can be judged even if many floating matters exist and a reflection wave from a precipitation sludge interface attenuates, and, since a reflection time from the precipitation sludge is exact, a distance up to the interface can be accurately measured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic range finder, and more particularly to an ultrasonic range finder for measuring a distance to a measurement object in a state where a floating object or the like exists between the objects. .

[0002]

2. Description of the Related Art Conventionally, it has been practiced to measure the distance to an object to be measured existing in a liquid using ultrasonic waves by utilizing the properties of ultrasonic waves that have good straightness and weak absorption in water. Have been done. For example, measurement of the distance to the sediment in the sedimentation layer, measurement of the sludge level in the storage tank for various liquid materials and fuels, and measurement of the level in the granular material washing tank are performed using an ultrasonic distance meter. ing.

As shown in FIG. 6, an ultrasonic distance meter (ultrasonic level meter) for measuring the distance from the water surface in the sedimentary layer 51 to the interface of the sediment sludge 55 transmits and receives ultrasonic waves. And a measuring unit 52 for calculating a distance based on a reflection time from transmission of the ultrasonic wave to reception of the ultrasonic wave. When the ultrasonic sensor 53 transmits an ultrasonic wave, the ultrasonic wave goes straight through the water 50 and the interface 56 of the sludge 55.
And is reflected at the sludge interface 56. Ultrasonic sensor 5
3 receives this reflected ultrasonic wave. The measuring unit 52 calculates the distance to the sludge interface 56 using the reflection time. The distance is L, the distance from the water surface to the settled sludge, V is the sound velocity of the underwater ultrasonic wave, and T is the time from when the ultrasonic wave is transmitted from the ultrasonic distance meter to the time when the ultrasonic wave is reflected back to the sludge interface (reflection time). Then, L = V × T / 2.

In the prior art, the reflection time T measures the time from the start of oscillation to the start of reception. In a state where the sludge is well settled, as shown in FIG. 7, a strong reflected wave can be received with respect to the transmission of the ultrasonic wave.

[0005]

However, as shown in FIG. 8, if there is a lot of suspended sludge in the water, the ultrasonic wave is reflected by the suspended matter 54 on the way to the transmission of the ultrasonic wave. The reflection has a disadvantage that the reflected wave from the settled sludge interface 56 is weakened. Settling sludge interface 5
When the reflected wave from the antenna 6 is weakened, the reception
As shown in FIG. 7, the reception wave includes the reflection from the suspended sludge 54, and the amplitude from the settled sludge is also reduced. Since the reflection time T measures the time from the start of transmission to the start of reception, the start of reception of the reflected wave from the settled sludge becomes unclear, and the measurement value of T becomes inaccurate. was there.

In order to remove the influence of the reflected noise from the suspended matter, a gain is applied to the received wave as shown in FIG. 10 to increase the amplitude of the reflected wave from the settled sludge. It is determined to be reflection from
However, since the attenuation of the reflected wave from the settled sludge by the suspended matter is not constant, it is difficult to set the amplitude value to judge the reflection from the settled sludge. The distance to is incorrect.

[0007]

The object of the present invention is to improve the disadvantages of the prior art, and to achieve a good measurement without the need for delicate setting even if various suspended matters exist between the object to be measured. It is an object of the present invention to provide an ultrasonic range finder capable of measuring a distance to an object.

[0008]

Therefore, according to the present invention, there is provided an ultrasonic sensor which emits an ultrasonic wave to an object to be measured and detects a reflected ultrasonic wave reflected from the object to be measured, and an ultrasonic sensor by the ultrasonic sensor. Time measuring means for measuring the elapsed time from the transmission of the reflected ultrasonic wave to the reception of the reflected ultrasonic wave, and a calculation for calculating the distance to the object to be measured based on the measuring time measured by the time measuring means and the sound speed of the ultrasonic wave Means. In addition, the time measuring means includes a transmission completion time detecting unit that detects completion of transmission of the ultrasonic wave by the ultrasonic sensor, and a reflected ultrasonic wave that detects attenuation of the reflected ultrasonic wave reflected from the measurement target to a predetermined amplitude. A sound attenuation detector,
A clock control unit that sets the time detected by the transmission completion time detection unit to the clock start time and sets the time detected by the reflected ultrasonic attenuation detection unit to the clock end time. . This aims to achieve the above-mentioned object.

The transmission completion time detector detects when the ultrasonic wave is transmitted by the ultrasonic sensor and the transmission is completed. For example, completion of transmission drive control of the ultrasonic sensor is captured. Then, the clock control unit sets the time when the transmission is completed as the clock start time. And the ultrasonic wave emitted from the ultrasonic sensor is reflected by a floating object or a measurement object, and the ultrasonic sensor
This reflected ultrasonic wave is received. When there is a floating object, the ultrasonic wave reflected by the floating object is received, and thereafter, the ultrasonic wave reflected by the measurement object is received. The reflected ultrasonic attenuation detector is
Detects the attenuation of the reflected ultrasonic wave reflected from the object to be measured to a predetermined amplitude, and the timekeeping control means determines when the reflected ultrasonic wave attenuation is detected by the reflected ultrasonic wave attenuation detection unit as a time-measurement end time. I do. For this reason, the time measuring means measures the time from the completion of transmission of the ultrasonic wave to the attenuation of the reflected ultrasonic wave, and thereby the time until the reflected ultrasonic wave reflected by the measurement object is received by the ultrasonic sensor. Time accurately.
Depending on the state of the floating object, the amplitude of the reflected ultrasonic wave due to the reflection from the floating object is substantially the same as the amplitude of the reflected ultrasonic wave reflected from the object to be measured. The amplitude of the ultrasonic wave is not used to determine whether the sound is a sound wave. On the other hand, the amplitude of the ultrasonic wave received after receiving the ultrasonic wave reflected by the measurement object is extremely attenuated. For this reason, the ultrasonic attenuation detector detects such attenuation of the reflected ultrasonic waves, and the time measuring means determines that the reception of the reflected ultrasonic waves reflected by the object to be measured is completed when the attenuation is detected. And end the timing. In this way, since the time from the completion of transmission of the ultrasonic wave to the time when the reflected ultrasonic wave is attenuated is the time from the reflection of the ultrasonic wave by the measurement object to the reception of the reflected ultrasonic wave, the ultrasonic wave generated by the suspended matter Irrespective of the presence or absence of reflection of the object, the reflection of the ultrasonic wave on the object to be measured is detected. For this reason, even if there is an object such as a floating substance between the ultrasonic sensor and the object to be measured, the distance to the object to be measured is accurately and stably detected.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an ultrasonic range finder according to the present invention. The ultrasonic distance meter emits an ultrasonic wave to the object to be measured and detects a reflected ultrasonic wave reflected from the object to be measured. The reflected ultrasonic wave is transmitted from the ultrasonic sensor 3 by transmitting the ultrasonic wave. Time measuring means 4 for measuring the elapsed time until the reception of the signal, and calculating means 1 for calculating the distance to the object to be measured based on the measuring time measured by the time measuring means 4 and the sound speed of the ultrasonic wave.
2 is provided.

The arithmetic means 12 calculates the underwater sound velocity of the ultrasonic wave as V,
When the time (reflection time) from when the ultrasonic wave is transmitted from the ultrasonic distance meter to the time when the ultrasonic wave is reflected at the sludge interface and returns is T, the distance L from the water surface to the settled sludge is L = V × T / 2. Ask.

The time measuring means detects a transmission completion time detecting section 6 for detecting the completion of transmission of the ultrasonic wave by the ultrasonic sensor, and detects an attenuation of the reflected ultrasonic wave reflected from the measuring object to a predetermined amplitude. A timed control unit that sets the time detected by the reflected ultrasonic attenuation detection unit 8 and the transmission completion time detection unit 6 as a timekeeping start time and sets the time detected by the reflected ultrasonic attenuation detection unit 8 as a timekeeping end time. 10 is provided.

The timekeeping controller 10 measures the time from the end of transmission of the ultrasonic wave to the end of the reception as the reflection time T. The transmission completion time detection unit 6 starts measuring the reflection time T when, for example, an oscillation stop signal is input from the CPU that drives the ultrasonic sensor. The reflected wave from the settled sludge is received last, and thereafter, as shown in FIG. 9, the received wave rapidly attenuates. Therefore, even if the amplitude value determined as the end of the received wave is set to a considerably small value, It can be determined that reception has ended. Therefore, even if there are a lot of suspended matter and the reflected wave from the interface of the settled sludge is considerably attenuated, it is possible to judge the end of the reception. Since T can be measured, the distance to the interface can be accurately measured.

In one embodiment, as shown in FIG. 2, the reflected ultrasonic attenuation detector 8 measures the oscillation elapsed time from the start of the ultrasonic oscillation by the ultrasonic sensor to the end thereof. Elapsed time from the time measurement function 13 until the amplitude of the reflected ultrasonic wave received by the ultrasonic sensor 3 exceeds the first specified amplitude a1 for reflection determination and becomes equal to or less than the second specified amplitude a2 for amplitude attenuation determination. A reception elapsed time counting function 14 for counting time, and when the reception elapsed time counted by the reception elapsed time counting function 14 exceeds the oscillation elapsed time counted by the oscillation time counting function 13, the reception elapsed time is counted. A determination function 15 for determining a waveform as an ultrasonic wave reflected by the measurement object; The transmission elapsed time is the pulse width of the ultrasonic wave emitted by the ultrasonic sensor 3. The ratio of the specified amplitude is defined as “specified amplitude a1 >> specified amplitude a
2 ".

In this example, the amplitude of the received waveform is determined to be a reflected wave in consideration of the possibility that the received waveform is attenuated before receiving the reflected wave from the object to be measured with few floating substances. When the amplitude a1 exceeds a1 and attenuates to a2, it is determined that the reflected wave is from the object to be measured. Furthermore, if there is a large floating substance, it may exceed the first specified amplitude a1 for the reflection determination, and it is difficult to optimize the setting of the amplitude value. It is difficult to determine whether the amplitude is from a floating substance or a measurement object.

In the present embodiment, in order to properly determine whether the reflection is from the object to be measured or the reflection from a floating object in a state where the difference between the amplitudes disappears, in the present embodiment, the oscillation elapsed time of the ultrasonic wave and the reception elapsed time Compare with time. That is, since the reflected wave from the floating object does not exceed the oscillation elapsed time of the ultrasonic wave, when the reception elapsed time exceeds the oscillation time, the determination function 15 determines that the waveform of the reception time is reflected by the object to be measured. Judge as a sound wave. Thereby, regardless of the degree of sludge and the type of suspended matter, the distance to the measurement object (interface) can be measured stably.

FIG. 3 is a block diagram showing the configuration of hardware resources according to this embodiment. Time measuring means 4 shown in FIG.
The calculation means 12 is realized by the CPU 20 executing the time measurement program and the calculation program. The ultrasonic range finder includes an oscillating circuit 21 for emitting ultrasonic waves from the ultrasonic sensor 3, a receiving circuit 22 for detecting ultrasonic waves received by the ultrasonic sensor 3, and a receiving waveform received by the receiving circuit 22. A waveform shaping circuit 23 for shaping and a detection circuit 24 for detecting a waveform shaped by the waveform shaping circuit are provided. The oscillation circuit 21 operates according to the drive control of the CPU 20, and when the drive control of the oscillation circuit 21 is completed, the CPU determines that the oscillation of the ultrasonic wave is completed. Also,
The CPU 20 corrects the value of the propagation speed V of the ultrasonic wave according to the output from a temperature sensor (not shown) attached to the ultrasonic sensor 3.

Further, the CPU 20 analyzes the received waveform input from the detection circuit 24, specifies the reflected wave from the object to be measured, and measures the reflection time. Then, the CPU calculates the distance from the reflection time to the sludge interface as the measurement target. The calculation result is digitally processed by the digital processing unit 31, and then displayed on the screen display unit 33. In addition, analog output and relay output are performed according to the control of the external input / output unit. The setting of the specified amplitude and the setting of the operation mode are performed by operating the key switch unit 34.

FIG. 4 is a waveform diagram showing an example of the oscillation and reception waveforms in this embodiment. When the oscillation circuit 21 emits for the specified oscillation time C1, various reflected ultrasonic waves are received. In the example shown in FIG. 4, a signal having an amplitude exceeding the first specified amplitude a1 is input. However, since the duration of the signal is C21 and does not exceed the oscillation time C1, this is determined to be a reflection from a floating substance. Next, there are many reflections from small suspended matter near the interface, and it becomes impossible to determine where the reflection is from the interface depending on the amplitude. However, in the present embodiment, the first specified amplitude a
If the input exceeding 1 continues longer than the oscillation time C1,
When the signal is attenuated, it is determined that the reception of the reflected signal is completed. For this reason, even if there are many suspended matters,
The distance to the sludge interface can be accurately measured.

FIG. 5 is a flowchart showing an example of the distance calculation processing according to the present embodiment. Here, the CPU 20
Performs time measurement using two counters. Counter 1
Time the reflection time. For this reason, the counter 1 measures the time from the completion of transmission of the ultrasonic wave to the predetermined attenuation of the reflected ultrasonic wave. The counter 2 counts the duration of reception having a predetermined amplitude or more.

There are two types of specified amplitudes used in the judgment branch, and the first specified amplitude a1 is an amplitude for judging that the sludge is reflected from the interface of the sludge. However, even the reflected ultrasonic waves from the suspended matter may exceed the specified amplitude a1. The second specified amplitude a2 is an amplitude for determining the last attenuation of the received wave. However, if there is no reflection from another floating object after reflection from a large isolated floating object, the amplitude is attenuated below the specified amplitude a2.

Further, in the processing shown in FIG.
The oscillation time C1 of 1 is compared with the reception elapsed time C2 from the time when the amplitude exceeds the specified amplitude a1 according to the output of the counter 2 until it becomes equal to or less than the specified amplitude a2. Elapsed reception time C2 is oscillation time C
If the time is shorter than 1, the reflected ultrasonic wave from the suspended matter is shorter than the oscillation time, so it is determined that the signal is not a signal from the sludge interface but an ultrasonic wave reflected by the suspended matter. .

First, the CPU 20 clears the counter 1 for measuring the reflection time (S1). Next, the oscillation circuit 2
1 to drive the ultrasonic sensor for a predetermined oscillation time C1 (S2). This oscillation time C1 is actually on the order of μs. When the oscillation is completed, the counter 1 starts counting (S3). Then, the counter 2 for measuring the reception elapsed time is cleared, and the value of C2 is set to "0" (S4). Next, the reflected wave is detected by the detection circuit 24.
(S5).

It is confirmed whether or not the amplitude of the received wave exceeds the specified amplitude a1 (S6). If it exceeds, it can be determined that it is some kind of reflected wave, so the counter 2 is started (S12). If the counter 2 has already counted, this S12 is skipped. After counting up, it waits for a certain time (S15),
The process returns to step S5.

On the other hand, if the amplitude of the received wave is smaller than the specified amplitude a1, the process proceeds to step S7. in this case,
There is a possibility that the reflected ultrasonic wave from the suspended matter is being received, and that the reception of the reflected wave from the sludge interface is terminated. In step S7, it is confirmed whether or not the received wave is smaller than the specified amplitude a2. If the received wave is smaller than the specified amplitude a2, the counter 2 is stopped and the value of the counter 2 is converted into the reception duration C2 (S8). When the received wave is larger than the specified amplitude a2, the counter 2 is cleared because the attenuation is different from the attenuation of the reflected wave from the sludge interface.
The value of C2 is set to "0". In this case, after waiting for a certain time (S15), reception is continued (S5).

In step S9, the oscillation time C1 is compared with the reception continuation time C2. When the received wave does not exceed the specified amplitude a1, C2 is smaller than C1 because C2 = 0. Therefore, the process does not proceed to step S10 for completing the time measurement, the counter 2 is cleared (S13), and the process waits (S1).
5) Re-receiving (S5).

When the count of the counter 2 is performed, and when the attenuation becomes smaller than the specified amplitude a2 when the amplitude becomes smaller than the specified amplitude a1, the process branches in the comparison of step S9. If the reception time C2 is longer than the oscillation time C1,
Stop the counter 1 and convert it to the reflection time (S1
0). On the other hand, if the reception time C2 is shorter than the oscillation time C1, it is determined that the reflection is from a floating substance, the counter 2 is cleared (S13), the standby (S15), and the re-reception (S5) are performed.

After calculating the reflection time T from the value of the counter 1, the CPU calculates the distance using the reflection time T,
It is displayed (S11).

As described above, according to the flowchart shown in FIG. 5, only when the received wave satisfies all of the following conditions, it is determined that the attenuation of the received wave is the end of the reception of the reflected ultrasonic wave from the sludge interface. First, the received wave becomes equal to or greater than the specified amplitude a1, and then attenuates to a specified amplitude a2 or less when attenuated from an amplitude equal to or larger than the specified amplitude a1, and an amplitude larger than the specified amplitude a1 is longer than the oscillation time C1. Then, it is assumed that the time of the attenuation is the time when the reflection time is completed. The time required for the change from the state exceeding the specified amplitude a1 to the state smaller than the specified amplitude a2 is adjusted by the wait time in step S15.

[0031]

The present invention is constructed and functions as described above. According to this, the timekeeping control unit controls the ultrasonic wave on the object to be measured from the time when the transmission of the ultrasonic wave is completed to the time when the reflected ultrasonic wave is attenuated. Is reflected and the time until the reflected ultrasonic wave is received, so that it is possible to detect the reflection of the ultrasonic wave on the measurement object without being influenced by the presence or absence of the ultrasonic wave reflection by the floating object. An unprecedented ultrasonic rangefinder that can accurately and stably detect the distance to the measurement object even if there is a noise such as a floating substance between the ultrasonic sensor and the measurement object. Can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a block diagram showing a detailed configuration of a reflected ultrasonic attenuation detector shown in FIG.

FIG. 3 is a block diagram illustrating a configuration of hardware resources according to the embodiment illustrated in FIG. 1;

FIG. 4 is a waveform chart showing a waveform of a reception signal received by the ultrasonic sensor shown in FIG.

FIG. 5 is a flowchart illustrating an example of a distance measurement process by the configuration illustrated in FIG. 1;

FIG. 6 is an explanatory diagram showing a schematic configuration of a conventional ultrasonic range finder.

FIG. 7 is a waveform diagram illustrating a received signal waveform when there is no suspended sludge.

FIG. 8 is an explanatory diagram showing an example of a sedimentation tank having suspended sludge.

FIG. 9 is a waveform diagram showing an example of a received signal waveform of reflected ultrasonic waves reflected at the interface of the settling tank shown in FIG.

FIG. 10 is a graph illustrating an example of a gain applied to a received wave in order to remove an influence of reflected noise from a floating substance.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st counter 2 2nd counter 3 Ultrasonic sensor 4 Time measurement means 6 Transmission completion time detection part 8 Reflection ultrasonic attenuation detection part 10 Time control part 12 Calculation means

Claims (2)

[Claims] An ultrasonic sensor that emits an ultrasonic wave to a measuring object and detects a reflected ultrasonic wave reflected from the measuring object, and from transmission of the ultrasonic wave by the ultrasonic sensor to reception of the reflected ultrasonic wave. An ultrasonic distance including time measuring means for measuring the elapsed time of the ultrasonic wave, and arithmetic means for calculating a distance to the object to be measured based on the measuring time measured by the time measuring means and the sound speed of the ultrasonic wave. In the meter, the time measuring means, a transmission completion time detecting unit that detects completion of transmission of the ultrasonic wave by the ultrasonic sensor, and attenuates the reflected ultrasonic wave reflected from the measurement target to a predetermined amplitude. The reflected ultrasonic attenuation detection section to be detected, and the time detected by the reflected ultrasonic attenuation detection section while setting the time detected by the transmission completion time detection section to the clocking start time. Ultrasonic distance meter, characterized in that a timing control unit that sets at the end time. 2. A reflection ultrasonic attenuation detection unit for measuring an oscillation time from the start of the ultrasonic oscillation by the ultrasonic sensor to the end of the oscillation, and a reflection received by the ultrasonic sensor. A reception elapsed time counting function for counting an elapsed time from when the amplitude of the ultrasonic wave exceeds the first specified amplitude for determining reflection to when it becomes equal to or less than the second specified amplitude for amplitude attenuation determination; When the reception elapsed time measured by the function exceeds the oscillation elapsed time measured by the oscillation time counting function, a determination function of determining the waveform of the reception elapsed time as the ultrasonic wave reflected by the measurement object. The ultrasonic distance meter according to claim 1, further comprising: