JP2005049302A - Method for detecting build up of acoustic wave signal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily detect the rise of an acoustic wave signal while discriminating from noise in a method for detecting the build up of the acoustic wave signal received by an ultrasonic element element. <P>SOLUTION: When the acoustic wave signal is received by the ultrasonic receiving element, the acoustic signal is stored in time series. A window W having a predetermined time band to the stored signal is scanned in the time axial direction (arrowed direction a) based on the transmitting time t0 of sound wave at a window width pitch, and the integrated value of waveform 10 of the acoustic signal in the window W is computed for each of scanning positions W1 and W2. It is determined whether or not the resulting integrated value is more than threshold. When the integrated value is the threshold or more, the time t' corresponding to the window position W2 at the time when the window W is detected is taken as the rise timing. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for detecting a rising edge of a sound wave signal, and more particularly to a method for detecting a rising edge of a sound wave signal in an ultrasonic sensor that measures the distance and direction to a detection target using ultrasonic waves.

  Conventionally, the time (propagation time) until the sound wave transmitted from the ultrasonic wave transmission element is reflected by the detection target and received by the ultrasonic wave reception element is measured, and the detection target is measured based on the propagation time and the sound speed. A method for measuring the distance is generally known. In addition, the signals received by a plurality of ultrasonic receiving elements are processed by delaying the time corresponding to the incident angle and the positional relationship between the elements, thereby selectively extracting only incident waves from any direction. A method is known in which the direction of an object is measured only by electrical signal processing without using a mechanical movable part (see Patent Document 1).

In such a distance / direction measuring method using ultrasonic waves, it is necessary to detect the rising timing of the first wave of the signal received by the ultrasonic receiving element. In addition, since noise is also received, there is a risk of erroneously detecting the rising timing of the received signal. The noise includes radio wave noise and external sound wave noise. The radio wave noise can be reduced to some extent by the shield, but is not perfect. The external sound wave noise cannot be prevented because the ultrasonic receiving element receives sound waves. In order to prevent such erroneous detection of the signal rise timing due to noise, a method in which the timing when the amplitude value of the waveform exceeds a predetermined threshold is used as the signal rise timing, or the received signal is sampled at a specific frequency. In addition, a method for estimating the rising timing from an envelope connecting a plurality of obtained peak values is known (see, for example, Patent Document 2).
JP 2002-156451 A JP-A-9-184716

  However, in the method for detecting the rising edge of the sound wave signal described in Patent Document 2 and the like, since the instantaneous value of the waveform is measured, the distinction between the sound wave signal and the noise still remains a problem. Patent Document 1 provides an ultrasonic sensor that is small and suitable for a built-in application, and does not provide a method for detecting a rising edge of a sound wave signal. An object of the present invention is to solve the above-described problem, and to provide a method capable of distinguishing noise from a sound wave signal and easily detecting the rising timing of the sound wave signal in the sound wave signal rise detection method. And

  The invention of claim 1 is a method for detecting the rising of a sound wave signal received by an ultrasonic wave receiving element of an ultrasonic sensor, and a) an analog signal obtained when the ultrasonic wave receiving element receives a sound wave signal A signal storing step for sequentially storing; b) a scanning step for scanning in a time axis direction a window having a predetermined time width with respect to the signal stored in the above with reference to the time of sound wave transmission; c) A feature amount measuring step for obtaining a feature amount of the sound wave signal in the window for each predetermined scanning position; and d) a rising edge detecting step for obtaining the rise timing of the sound wave signal based on the feature amount obtained as described above.

  According to a second aspect of the present invention, in the method for detecting a rising edge of a sound wave signal according to the first aspect, the scanning in the step b) performs a window with a window width pitch, and the feature amount in the step c) is a window. And the rising time is a time corresponding to the window position at the time when a window in which the integrated value is equal to or greater than a predetermined value is detected in step d). To do.

  According to a third aspect of the present invention, in the method for detecting a rising edge of a sound wave signal according to the second aspect, in the step d), with respect to the window in which the integrated value of the sound wave signal waveform in the window is equal to or greater than a predetermined value, It is divided, and a time corresponding to the window position at the time when a window in which the integrated value of the sound wave signal waveform in the divided window is equal to or greater than a predetermined value is detected is set as the rising timing.

  According to a fourth aspect of the present invention, in the method for detecting a rising edge of a sound wave signal according to the first aspect, the feature value in the step c) is used for transmission obtained by performing frequency analysis on the sound wave signal in the window. In the step d), a time corresponding to the window position at the time when a window in which the level of the frequency component obtained in the step c) is a predetermined value or more is detected. It is characterized by timing.

  According to a fifth aspect of the present invention, in the method for detecting a rising edge of a sound wave signal according to claim 1, it is known that the transmission frequency f of the sound wave is known and the amplitude of the sound wave signal received at the rising edge of the nth cycle is maximized. In some cases, the feature amount in the step c) is the amplitude of the received sound wave signal, and (n−0.75) × 1 from the time when the amplitude of the sound wave signal becomes the maximum in the step d). It is characterized in that the time detected by the time of / f is the rising detection timing.

  The invention of claim 6 further comprises an envelope extraction step of extracting an envelope component of the sound wave signal received by the ultrasonic wave receiving element in the method of detecting rising of the sound wave signal according to claim 1, wherein The feature amount in the step is an integral value of the envelope component in the window.

  According to a seventh aspect of the present invention, in the method for detecting a rising edge of a sound wave signal according to the sixth aspect, in the step d), an approximate curve is obtained from an integral value in a window where the integral value of the envelope component is equal to or greater than a predetermined value. The approximate curve and the intercept of the time axis are set as the rising timing.

  According to the rising detection method of the sound wave signal of the present invention, the sound wave signal received by the ultrasonic wave receiving element is stored in time series, and a window having a predetermined time width is set to the sound wave signal sequence with the sound wave transmission time. As the reference, scanning is performed in the time axis direction, and the rising timing of the sound wave signal is obtained from the feature value such as the integrated value of the sound wave signal in the window. Can be requested. Furthermore, by extracting the envelope component of the sound wave signal and obtaining the rising timing of the sound wave signal using the envelope component, the influence of noise can be further reduced.

(First embodiment)
Hereinafter, a method for detecting rising of a sound wave signal according to a first embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, the ultrasonic sensor 1 includes an ultrasonic transmission control unit 2 that controls a transmission operation of a sound wave, and an ultrasonic transmission element 4 for driving the ultrasonic transmission element 4 based on the control of the ultrasonic transmission control unit 2. A signal generation unit 3 that outputs a signal, an ultrasonic transmission element 4 that transmits a sound wave, an ultrasonic reception element 6 that receives a sound wave transmitted by the ultrasonic transmission element 4 and reflected by the detection target 5, and an ultrasonic wave The signal processing distance conversion unit 7 processes an analog signal received by the receiving element 6. The ultrasonic transmitting element 4 and the ultrasonic receiving element 6 may be a single element or an array element. In the case of a single element, only distance measurement is possible, and in the case of an array-like element, distance and direction can be measured. Further, the waveform of the signal transmitted by the ultrasonic transmission element 4 may be a single pulse or a burst wave.

  First, a procedure for measuring the distance and direction to the detection target 5 in the ultrasonic sensor 1 will be described. When a transmission start trigger is output from the ultrasonic transmission control unit 2 to a power source (not shown), the signal generation unit 3 outputs a signal for driving the ultrasonic transmission element 4. The ultrasonic transmission element 4 transmits a sound wave having a predetermined frequency (for example, about 20 to 100 kHz) based on this signal, and the transmitted sound wave is reflected by the detection target 5 and received by the ultrasonic reception element 6. The received signal is detected in the angular direction from the reflected wave arrival time and the delay time of the sound wave signal between the plurality of ultrasonic receiving elements 6 by detecting the rise time of the sound wave signal to be described later. A distance up to 5 can be determined.

  Next, the procedure for detecting the rising edge of the sound wave signal will be described with reference to FIGS. When the sound wave signal is received by the ultrasonic wave receiving element 6, the signal processing distance conversion unit 7 stores the sound wave signal in time series (# 21). Then, the window W having a predetermined time width with respect to the stored signal is scanned at the window width pitch in the time axis direction (arrow a direction) with reference to the sound wave transmission time t0 (# 22), and the scanning position Every time, the integral value (feature value) of the waveform 10 of the sound wave signal in the window W is calculated (# 23). Then, it is determined whether or not the obtained integral value is equal to or greater than the threshold value (# 24). If the integral value is equal to or greater than the threshold value (YES in # 24), when the window W is detected. The time t ′ corresponding to the window position is set as the rising timing (# 25). In the example of FIG. 3, the value is small at the window position W1 because it is an integration of only the noise component, but the value is large at the window position W2 because part of the sound wave signal (black part) is integrated. When this value exceeds a predetermined threshold value, the time t ′ corresponding to the window position W2 is set as the rising timing.

  As described above, since the signal rising timing is detected by the integral value of the waveform 10 in the window W, unlike the case where the instantaneous value of the waveform 10 is used, it is easy to distinguish between the signal and the noise. The rising timing of the sound wave signal can be detected by the method.

(Second Embodiment)
Next, a second embodiment will be described with reference to FIGS. The second embodiment is the same as the first embodiment in that the rising timing of the sound wave signal is detected by using the integrated value of the waveform 10 of the sound wave signal in the window W, but further, the window W is set to a predetermined value. This is different from the first embodiment in that a divided window (for example, w1 to w6) divided by the number of divisions is used. The signal processing distance conversion unit 7 stores the sound wave signal in time series (# 41), scans the window W with respect to the stored signal (# 42), and generates the waveform 10 of the sound wave signal in the window W. An integral value is calculated (# 43), and it is determined whether the integral value is equal to or greater than a threshold value (# 44). If the integral value of the waveform 10 of the sound wave signal in the window W is equal to or greater than the threshold value (YES in # 44), the window W is divided by a predetermined number of divisions (# 45). FIG. 5A shows a state where the integrated value exceeds the threshold value at the window position W1, and FIG. 5B shows that divided windows w1 to w6 are formed by dividing the window W into six at the window position W1. Indicates the state. Then, a divided window w2 in which the integrated value of the waveform 10 of the sound wave signals in the divided windows w1 to w6 is equal to or larger than a separately set threshold is detected (# 46), and the time corresponding to the detected position of the divided window w2 is detected. Let t ′ be the rise timing (# 47). Even in this configuration, since the signal rise timing is detected using the feature amount in the window W, it is easy to distinguish between the signal and the noise, and the rise timing of the sound wave signal can be detected by a simple method. Can do. Further, the rising edge of the sound wave signal can be detected with high accuracy by using the divided windows w1 to w6.

(Third embodiment)
Next, a third embodiment will be described with reference to FIGS. The third embodiment is different from the other embodiments in that the rising timing of the sound wave signal is detected using a frequency component (feature amount) obtained by performing frequency analysis on the sound wave signal in the window W. The signal processing distance conversion unit 7 stores the sound wave signal in time series (# 61), scans the window W with respect to the stored signal (# 62), and performs frequency with respect to the sound wave signal in the window W. Analysis is performed (# 63). In FIG. 7A, when frequency analysis is performed on the window positions W1 and W2, as shown in FIG. 7B, since only the noise component is present at the window position W1, there is a characteristic in the waveform subjected to frequency analysis. However, as shown in FIG. 7 (c), the window position W2 includes a sound wave signal, and therefore the waveform obtained by frequency analysis shows a peak P at the frequency f of the sound wave used for transmission. Then, it is determined whether the frequency component level is equal to or higher than the threshold value (# 64). If the frequency component level is equal to or higher than the threshold value (YES in # 64), the window at the time when the window is detected is determined. The time corresponding to the position is set as the rising timing (# 65). Even in this configuration, since the signal rise timing is detected using the feature amount in the window W, it is easy to distinguish between the signal and the noise, and the rise timing of the sound wave signal can be detected by a simple method. Can do.

(Fourth embodiment)
Next, a fourth embodiment will be described with reference to FIGS. In the fourth embodiment, when the transmission frequency f of the sound wave is known and the amplitude of the sound wave signal received at the rise of the nth cycle is known to be the maximum, the amplitude (feature value) of the received sound wave signal is known. ) Is used to detect the rising timing of the sound wave signal. Hereinafter, a case where the transmission frequency f of the sound wave is known and the amplitude of the sound wave signal received at the rise of the nth cycle is known to be maximum will be described. The signal processing distance conversion unit 7 stores the sound wave signal in time series (# 81), and until the window position and the time t at which the amplitude is maximum for the stored signal is detected (in # 83). YES), the window W is scanned (# 82). Then, a time that goes back by the time (n−0.75) × 1 / f from the time t at which the amplitude of the detected sound wave signal becomes maximum is calculated (# 84), and the obtained time t ′ is calculated as the sound wave signal. The rise detection timing is set (# 85). As shown in FIG. 9, when it is known that the amplitude of the sound wave signal received at the rising edge of the third period is maximized, from the time t when the amplitude of the received sound wave signal becomes maximum (3-0). .75) × 1 / f is the time before the sound wave signal rises. Here, (3-0.75) × 1 / f is a time obtained by multiplying (3-0.75) by (1 / f) which is a time per period. Even in this configuration, since the signal rise timing is detected using the feature amount in the window W, it is easy to distinguish between the signal and the noise, and the rise timing of the sound wave signal can be detected by a simple method. Can do.

(Fifth embodiment)
Next, a fifth embodiment will be described with reference to FIGS. Compared with the other embodiments described above, the fifth embodiment extracts the envelope component 20 of the waveform 10 of the sound wave signal received by the ultrasonic receiving element 6, and extracts the envelope component 20 (feature value). This is different from the other embodiments in that the rising timing of the sound wave signal is detected. First, the signal processing distance conversion unit 7 stores the sound wave signal in time series (# 101), and extracts the envelope component 20 of the waveform 10 from the stored signal (# 102). Then, the window W is scanned with respect to the envelope component 20 (# 103), and an integral value of the envelope component 20 in the window W is obtained (# 104). Then, it is determined whether or not the integral value is equal to or greater than the threshold value (# 105). If the integral value is equal to or greater than the threshold value (YES in # 105), the window at the time when the window W is detected is determined. The time corresponding to the position is set as the rising timing (# 106). Even in this configuration, since the signal rise timing is detected using the feature amount in the window W, it is easy to distinguish between the signal and the noise, and the rise timing of the sound wave signal can be detected by a simple method. Can do. Further, when detecting the rising edge of the sound wave signal, the integrated value of each window W changes gently by using the integrated value of the envelope component 20, so that the behavior of the sound wave signal can be easily traced, and the influence of noise. It can be made difficult to receive.

(Sixth embodiment)
Next, a sixth embodiment will be described with reference to FIGS. The sixth embodiment is the same as the fifth embodiment in that the rising timing of the sound wave signal is detected using the envelope component 20, but a window in which the integral value of the envelope component 20 is greater than or equal to a predetermined value. The difference from the fifth embodiment is that the rising timing of the sound wave signal is detected using the approximate curve 30 obtained from the integral value in W. The signal processing distance conversion unit 7 stores the sound wave signal in time series (# 121), and extracts the envelope component 20 of the waveform 10 (# 122). Then, the window W is scanned with respect to the envelope component 20 (# 123), and an integral value in the window W is obtained (# 124). Then, it is determined whether or not the integral value is equal to or greater than the threshold value (# 125). If the integral value is equal to or greater than the threshold value (YES in # 125), the integral value is plotted against the time axis. (# 126). The same procedure is repeated until the integral value is plotted at a predetermined point or more (YES in # 127), and the approximate curve 30 is obtained (# 128). For example, as shown in FIG. 13A, when the integral value 31 of the window positions W1 to W5 is equal to or greater than the threshold value, these are plotted with respect to the time axis, and curve fitting is performed to obtain the approximate curve 30. obtain. Then, an intercept between the approximate curve 30 and the time axis is calculated (# 129), and the intercept time t ′ is set as the rising timing (# 130). Even in this configuration, since the signal rise timing is detected using the feature amount in the window W, it is easy to distinguish between the signal and the noise, and the rise timing of the sound wave signal can be detected by a simple method. Can do. Further, when the rising edge of the sound wave signal is detected, the integral value of each window W changes gently by using the integral value of the envelope component 20, so that the behavior of the sound wave signal can be easily traced, and the influence of noise. It can be made difficult to receive.

  The present invention is not limited to the above-described configuration, and various modifications are possible. For example, the window scanning pitch is not limited to the window width. Alternatively, only a component around the resonance frequency of the ultrasonic receiving element 6 may be extracted from the sound wave signal received by the ultrasonic receiving element 6 using a band pass filter. By using a band-pass filter, it is possible to make it less susceptible to noise.

The block diagram of the ultrasonic sensor to which the method of this invention is applied. 3 is a flowchart showing a procedure for detecting the rising edge of a sound wave signal according to the first embodiment of the present invention. Explanatory drawing of the method to detect the rising of the sound wave signal by the embodiment. 9 is a flowchart showing a procedure for detecting a rising edge of a sound wave signal according to the second embodiment. It is explanatory drawing of the method of detecting the rising of the sound wave signal by the embodiment, (a) is a figure which shows a scanning step, (b) is explanatory drawing of a division | segmentation window. 9 is a flowchart showing a procedure for detecting a rising edge of a sound wave signal according to a third embodiment. It is explanatory drawing of the method to detect the rising of the sound wave signal by the embodiment, (a) is a figure which shows a scanning step, (b) is a figure which shows the frequency analysis result of window position W1, (c) is a window position The figure which shows the frequency analysis result of W2. 10 is a flowchart showing a procedure for detecting a rising edge of a sound wave signal according to a fourth embodiment. Explanatory drawing of the method to detect the rising of the sound wave signal by the embodiment. 10 is a flowchart showing a procedure for detecting a rising edge of a sound wave signal according to a fifth embodiment. Explanatory drawing of the method to detect the rising of the sound wave signal by the embodiment. 10 is a flowchart showing a procedure for detecting a rising edge of a sound wave signal according to a sixth embodiment. It is explanatory drawing of the method of detecting the rising of the sound wave signal by the embodiment, Comprising: (a) The figure which shows a scanning step, (b) is explanatory drawing of an approximated curve.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ultrasonic sensor 6 Ultrasonic receiving element 7 Signal processing distance conversion part (Signal storage step, scanning step, feature amount measurement step, rise detection step, envelope extraction step)
10 Waveform of sound wave signal 20 Envelope component of sound wave signal 30 Approximate curve W window W1, W2, W3, W4, W5 Window position w1, w2, w3, w4, w5, w6 Divided window

Claims (7)

A method for detecting a rising edge of a sound wave signal received by an ultrasonic wave receiving element of an ultrasonic sensor,
a) a signal storage step for storing, in time series, an analog signal obtained when the ultrasonic receiving element receives a sound wave signal;
b) a scanning step of scanning a window having a predetermined time width with respect to the signal stored as described above in the time axis direction with reference to the sound wave transmission time;
c) a feature amount measuring step for obtaining a feature amount of the sound wave signal in the window for each predetermined scanning position;
d) a rising edge detecting step for determining a rising edge timing of the sound wave signal based on the characteristic amount obtained as described above. The scanning in the step b) performs windows at a window width pitch,
The feature value in the step c) is an integrated value of the sound wave signal waveform in the window,
2. The rising edge of the sound wave signal according to claim 1, wherein a rising time is a time corresponding to a window position at the time when a window in which the integrated value is equal to or larger than a predetermined value is detected in the step d). Detection method.   In step d), the window in which the integrated value of the sound wave signal waveform in the window is equal to or greater than a predetermined value is divided by a predetermined number of divisions, and the integrated value of the sound wave signal waveform in the divided window is a predetermined value set separately. 3. The method for detecting a rising edge of a sound wave signal according to claim 2, wherein a time corresponding to the window position at the time when the above window is detected is set as a rising timing. The characteristic amount in the step c) is a frequency component of the sound wave used for transmission obtained by performing frequency analysis on the sound wave signal in the window,
The time corresponding to the window position at the time when the window in which the level of the frequency component obtained in the step of c) is a predetermined value or more is detected in the step d) is set as the rising timing. Item 2. A method for detecting a rising edge of a sound wave signal according to Item 1. When the transmission frequency f of the sound wave is known and the amplitude of the sound wave signal received at the rise of the nth period is known to be maximum,
The feature amount in step c) is the amplitude of the received sound wave signal,
2. The rise detection timing according to claim 1, wherein, in the step d), a time that goes back by a time of (n−0.75) × 1 / f from a time when the amplitude of the sound wave signal becomes maximum is used. Method of detecting the rising edge of sound wave signal. An envelope extraction step of extracting an envelope component of a sound wave signal received by the ultrasonic receiving element;
The method according to claim 1, wherein the feature amount in step c) is an integral value of the envelope component in a window.   In the step d), an approximate curve is obtained from an integral value within a window in which the integral value of the envelope component is equal to or greater than a predetermined value, and the approximate curve and the intercept of the time axis are used as the rising timing. Item 7. A method for detecting a rising edge of a sound wave signal according to Item 6.

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