JPS63158484A - Ultrasonic detector - Google Patents

Abstract

PURPOSE:To prevent the lowering of response at the arrival time of noise, by a method wherein a noise monitor section is shortened up to the falling point of time of the first one noise pulse when a noise pulse is detected in the noise monitor section and detection processing is performed after said section is finished. CONSTITUTION:The output of a receiving circuit 3 is inputted to a noise detection circuit 7. When a signal is received in a noise monitor section T2, the circuit 7 detects said signal as noise. When a noise pulse N1 is detected in the section T2, the section T2 is shortened up to the falling point of time of the pulse N1 and the length of said section becomes a section T2'. At the point A1 of time after the finish of the section T2, detection processing is performed. Further, the noise monitor section is shortened to the section T2' even with respect to the next noise pulse N2 and detection processing is performed at the point A2 of time. By this method, the lowering of response at the arrival time of noise is prevented.

Description

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

[Background technology 1] In general, in ultrasonic detectors, most of the noise received is ultrasonic pulses emitted by rotating machines such as engines;
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, or pulse width, from the detected noise, we can predict the next point in time when there will be no noise, and output a transmission pulse at that point. A method has been proposed in which detection processing is performed using

Fig. 4 shows the method; (a) shows the tone burst noise waveform generated from the rotating machine, and (b) shows the timing of the operation of the ultrasonic detector. In the figure, P 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 τ and pulse width τ2 are measured to predict the next point in time when no noise occurs, and the next This is to delay the detection process.

If there is no noise now, the detector operates as shown in figure (b), repeating the detection process in section T and the noise monitoring in section T2. 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 τ2 are measured, and the next time point A when the detection process is possible is determined, and the detection process is postponed until that time point A, as shown in (c)l. This time point A usually occurs immediately after the end of the noise monitoring period T2 or immediately after the first noise N after the noise monitoring period T2 (in the case shown).

By the way, in the above conventional method, it is necessary to detect at least two noises in order to measure the noise repetition period τ1, and therefore the length of the noise monitoring interval T is set to be more than twice as long as τ. However, if T2 is made too large so that a large number of noise pulses (Nf) are detected, the interval between detection processes becomes long and the responsiveness of the detector deteriorates; conversely, if T2 is made small, , repetition period τ1
There is a problem in that the reliability of the detector decreases as it becomes unable to respond to large noises and becomes unpredictable. Moreover, this repetition period τ is determined by the rotational speed of the rotating machine that is the source of the noise, and for example, the repetition period τ8 of a motorcycle that has just started and a motorcycle that is running at high speed is several times different, so the response It was extremely difficult to set the noise monitoring section T2 without sacrificing performance or reliability.

[Objective of the Invention 1] The present invention has been made in view of the above-mentioned problems, and its purpose is to suppress noise in a wider range of repetition periods than before without sacrificing the responsiveness of the detector. The goal is to provide an ultrasonic detector that can deal with this problem.

[Disclosure of the Invention] The present invention provides 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. A noise monitoring section is provided between the detection processing section including transmission and 1 reception and the next detection processing section, and when a noise pulse is detected in the section, the section is monitored until the falling point of the noise pulse. The detection process is performed after the end of the section, and the distribution of the repetition period of ultrasonic noise in urban areas is almost known. Since the noise pulse rarely disappears,
The feature is that the detection process is performed at this point.

[Embodiment 1] FIG. 1 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, It receives reflected wave pulses from an object, and this received signal is amplified by a wave receiving circuit 3, further amplified and detected by an amplification/detection circuit 4, and input to an object detection circuit 5. As shown in FIG. 2(a), the object detection circuit 5 detects the presence of an object when a signal is received within the transfer interval T, and also detects the transmitted pulse P of the received 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 the noise detection circuit 7, which detects the noise monitoring area nn T
When a signal is received within m, this is detected as noise.

Figure 2 (a) shows the operation of the detector in a noise-free state, in which a detection processing section T3 consisting of a transmission pulse P and a transfer section T1 immediately after it is repeated at regular intervals, and within this interval A noise monitoring section T2 of a certain length is provided. Note that a in the figure is the reverberation period. Stay here (b
) When the noise as shown in the figure is detected within the noise monitoring section T2 and the noise pulse N is detected, the noise monitoring section T2 becomes (c).
As shown in the figure, the interval length is shortened to the falling point of the noise pulse N1, and the interval length becomes T2', and the detection process is performed at time A1 after the end of this interval. Furthermore, for the next noise pulse N2, the noise monitoring interval is shortened to T2',
Detection processing is performed at time A2.

In some cases, the falling edge of the noise pulse detected in the noise monitoring interval T2 in the figure (a) may be different from Nl in the figure (b).
In some cases, the noise monitoring interval T2 may be after the rear end of the noise monitoring interval T2, as shown in FIG.

According to the above configuration, detection processing is performed immediately when noise is detected within the noise monitoring interval T2, so by detecting two noise pulses as in the conventional case, the noise repetition period τ
1, and therefore the responsiveness does not deteriorate when noise is detected, and even if only one noise pulse enters the noise monitoring section T2, the detection processing time becomes unpredictable as in the conventional method. There is no danger.

Note that the repetition period τ1 of the noise pulse is very short, and (
If the detection processing period T3 including the transmission and handover period does not fall within the period of τ, -τ2-a), the above method will also be interfered with by noise, but this situation can occur in multiple ways. It only occurs when other motorbikes are passing by, and the frequency is extremely small.

FIG. 3 shows another embodiment. In the case of ultrasonic noise in an urban area, as shown in FIG.
Immediately after the noise pulse N1 ends, whisker-like pulses called glitches are often accompanied, and in such cases, if object detection processing is performed immediately after the noise pulse N1, as shown in FIG.
This glitch G is received during the detection processing section T, and cannot be distinguished from the reflected wave from the object. Therefore, in this embodiment, as shown in figure (c), the noise monitoring section T
2, when the noise pulse N1 is detected, the noise monitoring interval T2 is extended or shortened until a certain time T has elapsed from the fall of the noise pulse N1, and within this extended period fill 'r 4 If glitch G is detected again in
, the noise monitoring section is extended by .

With this configuration, it is possible to prevent the detector from malfunctioning due to glyphs specific to ultrasonic noise, and it is possible to further improve the reliability of object detection.

[Effect of the Invention 1 As described above, the present invention shortens or extends the noise monitoring interval until the falling edge of the first noise pulse when a noise pulse is detected in the noise monitoring interval, and terminates this interval. Since the detection process is performed later, there is no need to detect the repetition period of the noise using two noise pulses as in the conventional method, and therefore, when only one noise pulse enters the noise monitoring interval. In addition, there is no risk of unpredictability at the time of detection processing as in conventional methods, and there is no need to wait for the second noise pulse, so there is an advantage that responsiveness does not deteriorate even during noise periods. It is something that you have.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing one embodiment of the present invention, Fig. 2 is a timing diagram showing the same operation as above, Fig. 3 is a timing diagram showing the operation of another embodiment, and Fig. 4 is the operation of the conventional example. FIG. P... Transmission pulse, T1... Receiving section, T2...
Noise monitoring section, T3...detection processing section, N, N,, N
2... Noise pulse, T1... Noise repetition period,
T2...Pulse width of noise, A,,A,...Detectable time point.

Claims (2)

[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,
An ultrasonic detector characterized in that when a noise pulse is detected in the section, the section is shortened or extended until the falling point of the noise pulse, and detection processing is performed after the end of the section. . (2) When a noise pulse is detected in the noise monitoring interval, the interval is shortened or extended until a certain period of time has elapsed since the fall of the noise pulse, and a whisker-like pulse is detected within the extended period. 2. The ultrasonic detector according to claim 1, wherein if the detection occurs, the section is further extended by a certain period of time from the time of detection.