JPS63158482A - Ultrasonic detector - Google Patents

Abstract

PURPOSE:To perform accurate estimation, by measuring the repeated cycle and pulse width of a noise pulse when the noise pulse is detected in a noise monitor section to store the same in a memory circuit and using the measured results in the determination of the detection processing point of time. CONSTITUTION:The output of a receiving circuit 3 is inputted to a noise detec tion circuit 7 which in turn detects said output as noise when a signal is re ceived in a noise monitor section T2. When two noise pulses N1, N2 are detected in the section T2, the repeated cycle tau1 of the noise and the continuing time, that is, the pulse width tau2 thereof are measured. On the basis of the measured values, the next detection processable point A1 of time is determined and a transmitting circuit 2 is controlled on the basis of the result thereof. When the third noise pulse N3 is detected in the section T2, the previously measured results stored in a memory circuit 9 are used as the values of the repeated cycle tau1 and the pulse width tau2. By this method, so far as even one noise pulse is detected, accurate estimation is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field 1] The present invention relates to a technique for preventing malfunction of an ultrasonic detector due to noise.

[Background Art] Generally, in an ultrasonic detector, most of the noise received is ultrasonic pulses emitted by a rotating machine such as an engine.
Since the period is relatively close to the operating period of the ultrasonic detector, there is a problem in that malfunctions are likely to occur due to noise. Therefore, by making use of the periodicity of this noise and measuring the repetition period and duration, that is, the pulse width, from the detected noise, we can predict α at the next noise-free time, and at that point A method has been proposed to perform detection processing by outputting .

Figure 3 shows this method. Figure (a) shows the tone burst noise waveform generated from the rotating machine, Figure (b) shows the timing of the operation of the ultrasonic detector, and Figure 3 shows the timing of the operation of the ultrasonic detector. P in the middle is a transmission pulse, T1 is a delivery period of a reflected wave pulse from an object, T2 is a noise monitoring period, and T is a detection processing period. In this noise monitoring section T2, the object is outside the detection area and there is no possibility that the reflected wave from the object will be received due to attenuation in the air, so the signal received in this section T2 is considered to be noise. This is an interval that can be determined, and if a noise pulse is detected in this interval, the repetition period τ1 and pulse width τ are measured to predict the next time when no noise will occur.
The next detection process is delayed until that point.

If there is no noise now, the detector operates as shown in figure (b), repeating the detection process of section T and the noise monitoring of section T2, but if the noise as shown in figure (a) is If you don't,
Two or more noise pulses N detected in the noise monitoring section T2
Then, the repetition period τ1 and pulse width τ□ are measured, and the next time point A when the detection process is possible is determined, and the detection process is postponed until dA at that time, as shown in FIG. This point A is usually immediately after the end of the noise monitoring period T2, or at the first noise N after the noise monitoring period Tj.
(in the illustrated case), but when the repetition period of the noise is small, detection processing may not be possible until the noise disappears.

By the way, in the above conventional method, in order to measure the noise repetition period τ1, the length of the noise monitoring section T2 must be set to at least twice 71 (although it is necessary to set T2 to be too thick ( If a large number of noise pulses N are detected, the interval between detection processes will become long and the responsiveness of the detector will deteriorate.On the other hand, if T2 is made small, it will not be possible to cope with large noises with a repetition period τ-. There is a problem that it becomes unpredictable and the reliability of the detector decreases.Moreover, this repetition period τ is determined by the rotation speed of the rotating machine that is the source of the noise. In the case of a running motorbike, the repetition period τ1
Since there is a difference of several times, it is difficult to set the noise monitoring section T2 without sacrificing both responsiveness and reliability.

[Object of the Invention] The present invention has been made in view of the above-mentioned problems, and its purpose is to cope with noise having a wider range of repetition periods than before without sacrificing the responsiveness of the detector. We aim to provide ultrasonic detectors that can

[Disclosure of the Invention] Accordingly, the present invention transmits ultrasonic pulses intermittently,
In an ultrasonic detector that detects the presence of an object or the distance to the object by receiving reflected waves from an object, noise monitoring is performed between a detection processing section including wave transmission and reception and the next detection processing section. A section is provided, and when a noise pulse is detected in the section, the repetition period and pulse width of the noise pulse are measured and stored in a storage circuit, and the next detection processing time point is determined from the measurement result. If the above measurement cannot be performed during the noise monitoring period, the previously stored measurement result is used to determine the detection processing point, and two noise pulses are not necessarily detected in the noise monitoring period. Since it is now possible to predict even if there is no noise, the feature is that the range of repeating periods of noise that can be detected can be almost doubled, without deteriorating the response even in the upstream.

[Example 1 tlfJ1 Figure shows an embodiment of the present invention, in which an ultrasonic transducer 1 for both transmitting and receiving waves is driven by a wave transmitting circuit 2 to intermittently transmit ultrasonic pulses, and This reception signal is amplified by the wave receiving circuit 3, further amplified and detected by the amplification/detection circuit 4, and input to the object detection circuit wr5. As shown in FIG. 2(b), the object detection circuit 5 detects the presence of an object when a signal is received within the reception period T, and also detects the transmission pulse P of the reception pulse. The distance to the object is calculated from the time delay from the time lag, and the output is displayed on the display 6.

The output of the delivery circuit 3 is also input to a noise detection circuit 7, and when a signal is received within the noise monitoring section T2 of FIG. Detected as. When 2 @tr>*sound pulses N3 and N2 are detected within this interval T2, the noise repetition period τ1
and its duration, that is, the pulse width τ2, are used to determine a possible time point A1 for the next detection process, and the wave transmitting circuit 2 is controlled based on the result.

Fig. 2(b) shows the operation of the detector in a noise-free state, in which a detection processing period T3 consisting of a transmission pulse P, a reception period T immediately after it, and a detection processing period T3 is repeated at regular intervals. A noise monitoring section T2 of a certain length is provided within the interval. Here *(a) Noise as shown in the figure arrives, two of which are noise pulses N and N, are in the noise monitoring interval T.
2, the repetition frequency τ1 of the noise pulse
and pulse width τ2 are measured, and from this measurement result (c)
As shown in the figure, the transmission time point A of the next transmission pulse P is calculated. In the figure, this time point A is the point in time when the reverberation time a has elapsed since the fall of the second noise pulse N2, and in reality (τ2
+a) Calculated after elapsed time.

(e) In the figure, when the next detection process is completed and a third noise pulse N is detected in the subsequent noise monitoring section T2, two noise pulses are detected in the same noise monitoring section T2 this time. become unable. Such a thing may occur if the repetition period τ1 is larger than 1/2 of the noise monitoring interval T, but in that case, the values of T1 and T2 are stored in the storage circuit 9. Use the previous measurement results.

(c) Time A2 in the figure is calculated in this way, and the time point N4 is calculated from one noise pulse N and the previous result, and the wave is transmitted at the previous time A. P
It is predicted that it will be possible to receive the wave T.

According to the above configuration, as long as at least one noise is detected within the noise monitoring section T2, the time point at which the next noise will arrive can be almost accurately predicted. If it is set to about twice the repetition period of the noise of a motorbike, it will be sufficient to deal with the case where a low-speed motor pike passes by, which rarely passes by.

Note that the repetition period τ1 of the noise pulse is very short, and (
If the detection processing interval T, including the wave transmission and handover intervals, does not occur within the period τ, -τ2-a), the detection processing possible time point A will be postponed until the noise disappears.

[Effects of the Invention] As described above, the present invention provides an ultrasonic detector that detects objects by detecting noise by detecting its repetition period and duration and predicting the point in time when the noise does not enter. In the case where two noise pulses are not detected in the monitoring interval and the repetition period cannot be measured, the previous measurement result is used, so as long as at least one noise pulse is detected in this interval, the prediction will be accurate. Therefore, there is an advantage in that malfunctions can be reliably prevented even with noise of approximately twice the repetition period without impairing responsiveness compared to the conventional method.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a timing diagram showing the operation of the same, and FIG. 3 is a timing diagram showing the operation of the conventional example. P... Transmission pulse, T1... Receiving section, T2...
Noise monitoring section, T3...detection processing section, N 1-N
2- N -... Noise pulse, T1... Noise repetition period, T2... Noise pulse width, A + -A
2...Detectable time. Agent Patent Attorney Ishi 1) Chief Figure 7 3

Claims (1)

[Claims] (1) In an ultrasonic detector that transmits ultrasonic pulses intermittently and receives reflected waves from an object to detect the presence of an object or the distance to the object, detection including wave transmission and reception A noise monitoring section is provided between the processing section and the next detection processing section,
When a noise pulse is detected in this section, the repetition period and pulse width of the noise pulse are measured and stored in a memory circuit, and the next detection processing time point is determined based on the measurement results, thereby monitoring the noise. An ultrasonic detector characterized in that, if the above-mentioned measurement cannot be carried out in the section, the previously stored measurement result is used to determine the detection processing point.