JPS63236985A - Ultrasonic distance measuring instrument - Google Patents

Abstract

PURPOSE:To decide whether or not a detected reflected wave signal is reliable and to decide a distance with an accurate ultrasonic wave by outputting a level variation abnormality signal when the received reflected ultrasonic wave is large in level variation. CONSTITUTION:An intensity difference detection part 4 inputs an ultrasonic wave received signal from the time measurement part 2 of a measurement part 8 and a time signal corresponding to the distance based upon a transmitted and a received signal and corrects the level of the received signal according to a time signal. Then the difference between plural corrected level signals is detected and when the difference exceeds a prescribed value, the detection part 4 outputs a signal indicating the received signal abnormality. Further, a composition part 6 generates a signal indicating time signal abnormality when the time difference from a time difference detection part 5 exceeds a specific value and both signals indicating the abnormality are ORed; and a decision part 7 decides whether or not the detected reflected wave signal is reliable and when not, an abnormality warning is outputted. Consequently, the distance is decided by accurate ultrasonic wave reception.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention measures the time from transmitting ultrasonic waves to a target until receiving a reflected signal from the target, and based on the measured time. The present invention relates to an ultrasonic distance measuring device that measures the distance to a target.

(Conventional technology) A conventional example of the present invention will be explained using FIG.

In this conventional example, an ultrasonic transmitting/receiving element (1) that emits ultrasonic waves and receives reflected waves, and an ultrasonic transmitting/receiving element (1) that emits ultrasonic waves by driving the ultrasonic transmitting/receiving element (1) and then transmitting the emitted signal. It consists of a time measurement section (2) that measures the time until reception and outputs it as a measurement signal. This time measurement unit (2) repeats the same measurement on the same target multiple times using the ultrasonic oscillation receiving element (1), takes the average value of the obtained times, and uses the average value as the final result. , improving the reliability of measurements.

(Problems to be Solved by the Invention) When the target object is a liquid or the like, the liquid level is not necessarily constant. If there are waves on the liquid surface, the strength of the reflected signal will be weakened and it will be affected by noise, causing the time measurement section (2
) variations in measurement time adversely affect accurate distance measurement. For this reason, a signal having an intensity higher than a preset level is used as a reflected signal. However, this increases the noise when the liquid surface has large ripples, increasing the possibility that the noise will be mistaken for a measurement signal. As a result, there was a problem in that it was not possible to accurately measure the distance to the liquid level.

The present invention has been made to solve the above problems, and makes it possible to realize accurate distance determination by determining whether the reflected signal detected by the ultrasonic transmitting/receiving element (1) is reliable. The purpose is to

[Configuration of the Invention (Means for Solving Problems)] In order to achieve the above object, the present invention transmits an ultrasonic wave to a target object, measures the time until the reflected signal is received, and measures the time until the reflected signal is received. In calculating the distance to a target from time,
The apparatus includes a level fluctuation abnormality detecting means for checking the level fluctuation of the received reflected signal and outputting a level fluctuation abnormality signal when the width of the level fluctuation is larger than a predetermined level.

Further, a time variation abnormality detection means is provided which measures the time a plurality of times, examines the fluctuations in these times, and outputs a time fluctuation abnormality signal when the width of the fluctuation in the time is larger than a predetermined level, Measured value abnormality determining means may be added that outputs a measured value abnormality signal when at least either the level fluctuation abnormal signal of the fluctuation abnormality means or the time fluctuation abnormal signal is output.

(Operation) In most cases, the signals transmitted and received by the ultrasonic transmitting/receiving means have a range of fluctuation. If the surface of the target object is unstable in position, the received signal is also unstable, so the width of the fluctuation becomes large. The level fluctuation abnormality detecting means detects the width of the fluctuation, and outputs a level fluctuation abnormality signal when the width is equal to or larger than a pre-measured width.

In other words, it can be said that the measurement data when this signal is output has low reliability.

Further, the time from the transmission of the ultrasonic wave measured by the distance measuring means to the reception of the reflected wave is measured multiple times. If this measurement result is not constant or unstable, it means that the distance to the target object surface is not constant. For this reason, the time fluctuation abnormality detection means may output a time fluctuation abnormality signal when the fluctuation width of the measurement result is equal to or larger than a predetermined width.

(Example) Embodiments of the present invention will be described using FIGS. 1 to 4.

First, a first embodiment will be described with reference to FIG.

Distance measurement using ultrasonic waves used to determine distance by measuring the time from emitting ultrasonic waves to a target until receiving the reflected waves.

In this embodiment, the measurement unit (8) includes an ultrasonic excavation/reception element (1) that transmits and receives ultrasonic waves and a time measurement unit (2), and the ultrasonic oscillation/reception element (1) generates ultrasonic waves. The time measuring section (the time it takes for the reflected wave to return)
Measure in 2).

This time measurement section (2) outputs the measured time signal to the intensity difference detection section (4) and time difference detection section (5), and sends the received signal, which uses the reflected wave as an electric signal, to the intensity difference detection section (4). Output.

In the received signal, when the surface of the target object changes, the reflected wave is disturbed and noise is generated in the signal, and the fluctuation level of the signal increases or attenuates as the measurement distance increases. do. Therefore, in order to accurately detect level fluctuations in the received signal due to the disturbance of the reflected waves, the received signal is corrected as if it were measured at a certain distance as a reference, and the reception signal due to the disturbance of the reflected waves is corrected. The purpose is to extract the magnitude of signal level fluctuations.

That is, when measuring the distance to a target object using ultrasonic waves, accurate measurement results cannot be expected if the target object is constantly moving or its surface generates noise. Therefore, the degree of noise is investigated by detecting the degree of disturbance from the reflected waves of the ultrasonic waves. In order to examine the degree of this disturbance, it is necessary to examine the reflected waves at the same distance, but in reality the distance to the target is not constant, so the received signal of the reflected wave from the target is attenuates by the amount. Therefore, the received signal is corrected by taking the ratio of the obtained time to a time signal corresponding to the time for the ultrasonic wave to travel back and forth over the reference distance, and amplifying the received signal based on this ratio.

The intensity difference detection unit (4) inputs the time signal and the received signal from the time measurement unit (2), performs the above-mentioned correction on the received signal based on the time signal, and determines that the received signal after correction has a level fluctuation range. If the width is greater than the set width, a signal indicating an abnormality in the received signal is output.

As explained above, accurate measurement cannot be performed even when the target is constantly moving. Therefore, the time difference detection section (5
), a plurality of past time signals are stored, the dispersion of the plurality of time signals is checked, and a signal indicating an abnormality of the time signal is output based on the magnitude. In other words, time is measured by emitting ultrasound for a certain period of time and measuring the time it takes for the signal to be reflected and received.The time is measured from the time the ultrasound begins to be transmitted to the time the reflected wave is received. Then, if the difference between the longest time and the shortest time among the plurality of times is greater than or equal to a set difference, a signal indicating a time signal abnormality is output. In this embodiment, variations are investigated based on the difference between the longest time and the shortest time, but the present invention is not particularly limited to this method.

The synthesis section (6) receives the outputs of the intensity difference detection section (4) and the time difference detection section (5), and outputs a signal indicating an abnormality if at least one of them indicates an abnormality.

The determination section (7) outputs an alarm when the synthesis section (6) outputs a signal indicating an abnormality.

This allows it to be determined whether the measurement results are reliable.

In addition, an intensity difference detection section (4) and a time difference detection section (5)
outputs a signal with a level corresponding to each change width, the synthesis section outputs the logical sum of each level signal, and the judgment section (
In step 7), an alarm may be output when the output is higher than a preset level.

The device shown in FIG. 2 includes only an intensity difference detection section (4) and outputs an alarm based only on the variation width of the received signal.

FIG. 3 is equipped with only a time difference detection section (5) and outputs an alarm based on the variation in measured time.

FIG. 4 shows an embodiment in which a delay section (9) and an interlotter section (10) are added to the configuration of FIG. 1. In this embodiment, the output of the determination section (7) obtained in the embodiment of FIG. 1 is used to prevent the measurement signal from going outside if the measurement signal is unreliable. First, the measurement signal output from the measurement section (8) passes through the delay section (9) and is input to the interlotter section (10). This interlock part (10
) is also inputted with the output of the determination unit (7).

If the output of the determination section (7) is a warning, the measurement signal is prevented from going out from the interrotter section (10). The delay section (9) is for preventing the measurement signal from reaching the interlock section (10>) until the output of the determination section (7) is determined based on the current measurement signal and the received signal.

As described above, when the reliability of the measurement signal is low, it is possible to prevent the measurement signal from going out to the outside.

[Effects of the Invention] According to the present invention, when measuring distance using ultrasonic waves, it is possible to determine whether or not the measurement result is reliable, so that more accurate measurement results can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a first embodiment of the present invention.
Fig. 2 is a diagram for explaining the second embodiment, Fig. 3 is a diagram for explaining the third embodiment, Fig. 4 is a diagram for explaining the fourth embodiment, and Fig. 5 is a diagram for explaining the fourth embodiment.
The figure is a diagram explaining a conventional example. 1... Ultrasonic oscillation/receiving element 2...
...... Time measurement section 4 ..... Intensity difference detection section 5 ..... Time difference detection section 6 ..... Synthesis section 7. ..... Determination section 8 ..... Measurement section 9 ..... Delay section

Claims (1)

[Scope of Claims] 1) Ultrasonic wave transmitting/receiving means for transmitting ultrasonic waves to a target object and receiving reflected signals from the target object; An ultrasonic distance measuring device comprising: distance measuring means for measuring a time until a signal is received, and determining a distance signal from the ultrasonic transmitting/receiving means to the target object based on the measured time; An ultrasonic distance measuring device comprising level fluctuation abnormality detection means for detecting a level fluctuation of a reflected signal received by the means and outputting a level fluctuation abnormality signal if this level fluctuation is larger than a predetermined level. . 2) measuring the time from the transmission of the ultrasonic wave obtained by the distance measuring means to the reception of the reflected signal multiple times;
A time fluctuation abnormality detection means is provided for checking the time fluctuations and outputting a time fluctuation abnormality signal when the width of the time fluctuation is larger than a predetermined level, and the level fluctuation abnormality signal of the level fluctuation abnormality means is The ultrasonic distance measuring device according to claim 1, wherein a measured value abnormal signal is output when at least one of the time-varying abnormal signals is output.