JPH07318335A - Method and apparatus for ultrasonic detection - Google Patents

Abstract

PURPOSE:To perform a quick-response detection without a need of resetting a sampling signal even when the interval between an ultrasonic-wave transmitter and an ultrasonic- wave receiver is changed by a method wherein a received signal is changed into shaped waves having one peak value and the peak value of the shaped waves is fetched into and held at the timing of the peak value of the shaped waves. CONSTITUTION:An utrasonic pulse train which is not cut off by an object to be measured or an ultrasonic pulse train which has been attenuated and an ultrasonic pulse train which has been reflected out of ultrasonic pulse trains which are transmitted by an ultrasonic-wave transmitter 3 are received by an ultrasonic-wave receiver 4, they are rectified and smoothed by a waveform shaping circuit 6, and shaped waves having one peak value are obtained. Since a received signal is rectified, the peak value indicates the maximum value of absolute values of the received signal. A differentiating circuit 7 finds the generation timing of the output signal of the waveform shaping circuit 6, and the peak value of the shaped waves is fetched into and held by a sample-and-hold circuit 11 at the timing. The amplitude of direct waves which are not cut off by the object to be measured or which have passed the object can be known by the peak value, and the position, the thickness and the like of the object to be measured can be detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic detecting method and apparatus for detecting an end position of a web carried between an ultrasonic wave transmitter and an ultrasonic wave receiver, a thickness of the web, a seam position and the like.

[0002]

2. Description of the Related Art An edge position of a web is detected by irradiating the edge of the web with light and detecting the edge position (edge position) according to the amount of light shielding, or an object that transmits light or a photosensitive object. In this case, there is a method in which air is blown onto the lower surface of the edge of the web and the position of the web edge is detected from the amount of change in the air pressure on the upper surface of the web edge. In addition, a method of arranging the ultrasonic transmitter and the ultrasonic receiver facing each other and detecting the position of the web edge from the change in the received signal of the ultrasonic receiver when the edge of the web enters between them It is disclosed in Japanese Patent Publication No. 62-501520. In this method, when a pulse train of ultrasonic waves is intermittently transmitted from a wave transmitter, a direct wave and a reflected wave reflected by a web or a wave receiver are received by a wave receiver,
Of these, the range of the direct wave is limited and sampling is performed, and the peak value is extracted as an electric signal.

[0003]

The optical edge position detection method cannot be used when the web is transparent. In addition, the method of using air often causes the web to become dirty due to the cleanliness of the air or the inclusion of dust in the surrounding area.Furthermore, the change in the wind pressure of the air causes the web edge to wavy or be caught, resulting in output signals. Change. In addition, the response is slow, so it becomes less stable. Also, published patent publication Sho 6
In the case of No. 2-501520, in the electric signal converted by the wave receiver, a limited area not including the reflected wave is sampled, so that the reception signal of the wave receiver is synchronized with the transmission timing of the wave transmitter. Sampling and resetting,
The timing signal must be reset when the mounting distance between the transmitter and the receiver changes.

A reflected wave may cause a standing wave, that is, a so-called beat phenomenon due to interference with a direct wave. A standing wave is one in which the waves have the same amplitude but travel in opposite directions and do not travel. When a standing wave occurs, the received signal fluctuates and measurement becomes impossible. However, if the generation of standing waves can be prevented, the detection of the edge position, thickness, and seam position of the web will not be hindered even if the direct wave and the reflected wave overlap. This is because the direct wave with a large peak value is usually received first, and the peak value of the reflected wave received thereafter is often smaller than that of the direct wave, so detecting the maximum value will detect the edge position of the web. Because you can.

The present invention has been made on the basis of such knowledge, and in detecting the edge position of the web, the peak value of the received signal of the wave receiver is detected so that the sampling signal and the reset signal of the wave receiver are detected. It is not necessary to synchronize the generation of the ultrasonic wave with the wave transmitter, and even if the distance between the ultrasonic wave transmitter and the ultrasonic wave receiver is changed, it is not necessary to reset the sampling signal, and the ultrasonic wave detection method with a quick response and The purpose is to provide a device.

[0006]

In order to achieve the above object, an ultrasonic wave detecting method for detecting an object to be measured between an ultrasonic wave transmitter and an ultrasonic wave receiver, The sound wave pulse train is transmitted at a predetermined interval, the signal received by the ultrasonic wave receiver is used as a shaping wave having one peak value, the timing at which this shaping wave reaches a peak is determined, and the shaping is performed at this peak timing. Try to capture and hold the peak value of the wave.

Further, in an ultrasonic wave detecting device for detecting an object to be measured between the ultrasonic wave transmitter and the ultrasonic wave receiver, the output of the ultrasonic wave receiver is a shaped wave having one peak value. Waveform shaping means, peak detecting means for detecting the timing when the output waveform of the waveform shaping means reaches a peak, and a sample and hold circuit for taking in and holding the output of the waveform shaping means according to the peak timing output by the peak detecting means. And the ultrasonic wave transmitter transmits the ultrasonic pulse train at predetermined intervals.

The waveform shaping means includes a rectifier, a capacitor for storing the output of the rectifier, and a leak resistor for discharging the capacitor.

Further, the peak detecting means includes a differentiating circuit that differentiates the output of the waveform shaping means, and a zero-cross comparator circuit that detects a zero point of the output of the differentiating circuit.
The one-shot multivibrator circuit that outputs a pulse by the output of the zero-cross comparator circuit is provided.

A retriggerable multivibrator circuit for outputting a pulse signal having a predetermined pulse width longer than the predetermined interval of the ultrasonic pulse train to the sample and hold circuit from the time when the output of the zero-cross comparator circuit is input is provided. The sample and hold circuit releases the hold value by the pulse signal.

Further, the ultrasonic wave transmitter makes the transmission duration of the ultrasonic pulse train shorter than the time required for the ultrasonic waves to reciprocate between the ultrasonic wave transmitter and the ultrasonic wave receiver, and At a predetermined interval, the next pulse train arrives at the ultrasonic receiver after the reflected wave of the previous pulse train has almost disappeared.

[0012]

Function: The ultrasonic pulse train transmitted from the ultrasonic wave transmitter receives what is not blocked, attenuated and reflected by the object to be measured, and is received by the ultrasonic wave receiver. Rectify and smooth to get a shaped wave with one peak value. Since the received signal is rectified, this peak value indicates the maximum absolute value of the received signal. The peak detection means determines the timing of generation of this peak value, and the peak value of the shaped wave is fetched and held in the sample and hold circuit at this timing. From this peak value, the amplitude of the direct wave that is not blocked by the measured object or transmitted through it can be known, and the position and thickness of the measured object can be detected. The received wave received by the wave receiver first appears as a direct wave, and then a reflected wave having a smaller amplitude than this. The shaped wave is attenuated after reaching the peak value, but the shaped wave having only one peak is obtained by attenuating so that the level at the time of this attenuation is kept higher than the level of the reached reflected wave.

The waveform shaping means rectifies the received wave of the wave receiver by the rectifier, accumulates it in the capacitor, and discharges it by the leak resistance. As a result, the maximum value of the first arriving direct wave is accumulated in the capacitor, and then the voltage gradually decreases. When a reflected wave with a smaller amplitude than the direct wave arrives following the direct wave, one peak value (maximum value) can be set by setting the leak resistance value so that the discharged voltage is larger than the reflected wave voltage. A shaped wave having only (value) is obtained.

In the peak detecting means, when the shaped wave is differentiated by the differentiating circuit, the position of the peak value appears as a pole point where the gradient becomes 0. Therefore, the zero crossing comparator circuit determines the timing when the output of the differentiating circuit becomes 0 point. By detecting and generating a pulse from the one-shot multivibrator circuit at this timing, the sample and hold circuit can hold the peak value of the shaped wave.

The retriggerable multivibrator circuit outputs a pulse signal having a predetermined pulse width longer than the transmission interval of the ultrasonic pulse train to the sample and hold circuit from the time when the output of the zero cross comparator circuit is input, and the sample signal is sampled by this pulse signal. -The hold circuit releases the hold value, so when the ultrasonic wave transmitter stops transmitting the pulse train, or the space between the wave transmitter and the wave receiver is completely shielded.
When the received signal becomes zero, the output of the sample and hold circuit is set to zero. In addition, since the peak is detected and the hold is released by differentiation, the response is faster than resetting due to capacitor leakage.

The ultrasonic wave transmitter makes the transmission duration of the ultrasonic pulse train shorter than the time it takes for the ultrasonic waves to reciprocate between the ultrasonic wave transmitter and the receiver, and sets the transmission interval of the ultrasonic pulse train first. Since the next pulse train arrives at the ultrasonic receiver after the reflected wave of the pulse train has almost disappeared, it is possible to prevent the standing wave from being generated and reduce the influence of the reflected wave on the direct wave.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of this embodiment. The oscillator circuit 1 has a cycle of a pulse train of ultrasonic waves to be transmitted,
Amplitude, pulse train transmission duration T2, pulse train interval T
Determine 1 and oscillate. The power amplification circuit 2 power-amplifies the pulse train generated by the oscillation circuit 1. The ultrasonic wave transmitter 3 converts the power-amplified signal into ultrasonic waves and transmits the ultrasonic waves. The ultrasonic wave transmitter 3 and the ultrasonic wave receiver 4 are arranged to face each other, and the web 12 is conveyed therebetween in the direction perpendicular to the drawing. The ultrasonic wave receiver 4 transmits the ultrasonic wave from the ultrasonic wave transmitter 3 and arrives at the web 12 without being blocked, the web 12, the wave receiver 4,
The reflected wave reflected by the surrounding members is converted into an electric signal. The pre-stage amplifier circuit 5 amplifies this electric signal.

The waveform shaping circuit 6 rectifies the amplified electric signal with a diode and generates a unipolar shaped wave with a capacitor and a resistor. The shaping wave has the maximum value of the maximum value of the direct wave, and the capacitors and resistance values are set so as to have a shape that gently attenuates. The differentiating circuit 7 differentiates the shaped wave to generate a waveform in which the voltage is zero at the peak value (maximum value). The zero-cross comparator circuit 8 detects the timing when the differentiated waveform becomes zero. The one-shot multivibrator circuit 9 generates one pulse having a short width at this timing. The retriggerable multivibrator circuit 10 is the same circuit as the one-shot multivibrator circuit 9 and sets the pulse width to T3, which is longer than the interval T1 of the pulse trains oscillated by the oscillation circuit 1, so that the pulse falls after T3 from the latest input. Is set to. The sample-and-hold circuit 11 takes in and holds the output of the waveform shaping circuit 6 each time the pulse of the one-shot multivibrator circuit 9 is output, and is reset by the output of the retriggerable multivibrator circuit 10.

FIG. 2 is a diagram showing means used for reducing the influence of the reflected wave. FIG. 2A shows a pulse train of ultrasonic waves transmitted from the ultrasonic wave transmitter 3 to the ultrasonic wave receiver 4. The web 12 is arranged so as to be inclined so that reflected waves from the web 12 do not enter the ultrasonic wave transmitter 3 and the ultrasonic wave receiver 4. In (b), the wave receiving surface of the ultrasonic wave receiver 4 is inclined with respect to the pulse train transmitted from the ultrasonic wave transmitter 3 so that reflected waves do not enter the ultrasonic wave transmitter 3. By taking such measures and setting the oscillation condition of the pulse in the oscillation circuit 1 so as not to generate a standing wave described later, the influence of the reflected wave can be sufficiently reduced.

FIG. 3 shows waveforms generated in each circuit shown in FIG. a to h represent waveforms in the corresponding circuits. FIG. 4 is a diagram showing a configuration example of the waveform shaping circuit 6 and the subsequent components in the circuit of FIG. The circuit will be described in detail below with reference to FIGS.

FIG. 3a shows the output waveform of the power amplifier circuit 2.
T1 represents the pulse train interval, and T2 represents the transmission duration of the pulse train. T1 and T2 are set to values such that a standing wave due to the direct wave and the reflected wave does not occur. T2 is an ultrasonic wave transmitter 3
The ultrasonic wave receiver 4 and the ultrasonic wave receiver 4 are set shorter than the time when the ultrasonic wave reciprocates so that the reflected wave from the wave receiver 4 and the direct wave from the wave transmitter 3 are not combined. T1 is set so that the next pulse train reaches the receiver 4 when the reflected wave by the previous pulse train almost disappears. As an example, T1 / T2 is set to 10 or more, although it depends on the installation conditions and the frequency.

FIG. 3b shows the output waveform of the ultrasonic receiver 4,
First, a large amplitude direct wave appears, and then a smaller amplitude reflected wave appears. After the reflected wave disappears, the next direct wave of the pulse train appears.

The waveform shaping circuit 6 will be described with reference to FIG.
This circuit 6 uses a peak hold circuit, performs single-wave rectification with a diode 6a, and accumulates it in a capacitor 6b.
The voltage of the capacitor 6b is discharged by the leak resistance 6c. The operational amplifier 6d is used as a voltage follower and holds and outputs the charge voltage. The operational amplifier 6e prevents the voltage drop (about 0.6 V) of the diode 6a and operates as an ideal diode. Capacitor 6b and leak resistance 6
The value of c is set so that the discharge voltage of the peak value due to the direct wave becomes larger than the peak value of the reflected wave, and becomes 0 level after the elapse of T1 time. As a result, as shown in FIG. 3c, a shaped wave having one peak value is obtained, which is smoothly attenuated from the maximum value of the direct wave.

The differentiating circuit 7 uses the operational amplifier 7a and outputs a signal proportional to the time derivative (change) of the input signal. The peak of the input waveform indicated by the signal c is a point at which the rate of change becomes zero, so the output voltage becomes zero at this point. That is, the point where the output signal d of the differentiating circuit 7 crosses 0 is the signal c.
Is the peak position (maximum value). Since the output d of the differentiating circuit 7 in FIG. 4 is an inverted output, it is shown as a forwardly rotated d ′ in FIG. 3 for easy understanding.

The zero-cross comparator circuit 8 is composed of an operational amplifier. The comparator is a circuit that determines whether the voltage of the input signal is higher or lower than the reference voltage. A circuit in which the reference voltage is 0V is called a zero-cross comparator circuit. This is because the output voltage of the comparator changes every time the input voltage crosses 0V from positive to negative or from negative to positive. FIG. 3e shows the output of the zero-cross comparator circuit 8. Since the sign changes from negative to positive at the rising of d ', e rises, and falls from positive to negative at the 0th line and falls. This falling point represents the peak value of c.

One-shot multivibrator circuit 9
Is also called a monostable multivibrator, and outputs one pulse signal of a constant width by an input (pulse) signal.
Generally, a dedicated IC is used. 3f shows the output of the one-shot multivibrator circuit 9, which outputs a short pulse when e falls. FIG. 3f shows this state.

Retriggerable multivibrator circuit 1
0 outputs a pulse signal with a constant width by an input (pulse) signal as in the one-shot multivibrator circuit 9, but accepts a trigger as many times as necessary. If the next pulse is input before this constant width has passed from the input, a pulse signal with a constant width is output from the pulse input. In this embodiment, this constant width is T3, which is longer than T1. That is, if the next peak does not occur even after T3 time has elapsed after the peak of the shaped wave c, the generation of the peak signal is considered to have ended,
Used for reset signal. FIG. 3g shows this state.

The sample and hold circuit 11 includes an input switch 11a, a capacitor 11b, a relay protection resistor 11c,
It is composed of a reset switch 11d and an operational amplifier 11e. The input switch 11a is turned on when the pulse signal of the one-shot multivibrator circuit 9 rises and turned off when it falls. Capacitor 11
b charges to the input voltage during this ON. The output voltage (potential of the capacitor 11b) at this time follows the input signal. When the input switch 11a is turned off, the voltage immediately before being turned off is held. Reset switch 1 by falling signal of retriggerable multivibrator circuit 10
1d is turned on, the capacitor 11b is discharged, and the output voltage becomes 0V. The operational amplifier 11e functions as a voltage follower and holds and outputs the charge voltage. FIG. 3 h shows this state.

From the output of h in FIG. 3, the edge position of the web 12 shown in FIG. 1 can be detected. That is, the value of h is maximum when the web 12 is not present,
If the path of the ultrasonic wave is cut off, h becomes 0. As shown in the figure, when the web 12 is at the half position, the value of h is also half the value. Actually, a calibration curve of the position of the web 12 and the value of h is created in advance, and based on this, the edge position of the web 12 can be accurately detected from the value of h. Further, by detecting the amount of attenuation of ultrasonic waves that pass through the web 12, it is possible to detect the lap joint and the thickness of the web 12.

Since the pulse generation period is short and the pulse interval has sufficient time for the influence of the surrounding reflection to be attenuated, the generation of a standing wave can be prevented. Further, since the reset is performed by the peak detection, the reset is performed in a shorter time than the reset by the leak of the leak resistance, so that the response is fast.

[0031]

As is apparent from the above description, the present invention prevents the generation of a standing wave due to a reflected wave from the surroundings, and the output of the ultrasonic wave receiver is a shaped wave having one peak value,
Since this peak value is detected and sampled and held, it is not necessary to transmit a sampling signal or a reset signal of the peak value of the received signal from the ultrasonic wave transmitter side to the wave receiver side. Even if the distance between the wave transmitter and the wave receiver changes, it is not necessary to change the settings of the peak value sampling signal and the reset signal. Further, since the sampling of the received signal and the reset signal are not transmitted from the ultrasonic wave transmitter side to the wave receiver side, a communication line connecting them is unnecessary.

[Brief description of drawings]

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

FIG. 2 is a diagram illustrating means used to reduce the influence of reflected waves.

FIG. 3 is a diagram showing an output waveform of each circuit.

FIG. 4 is a diagram illustrating circuit contents after a waveform shaping circuit.

[Explanation of symbols]

 1 Oscillation circuit 2 Power amplification circuit 3 Ultrasonic wave transmitter 4 Ultrasonic wave receiver 5 Pre-stage amplification circuit 6 Waveform shaping circuit 7 Differentiation circuit 8 Zero cross comparator circuit 9 One-shot multivibrator circuit 10 Retriggerable multivibrator circuit 11 samples・ Hold circuit 12 Web

Claims (6)

[Claims] 1. An ultrasonic wave detecting method for detecting an object to be measured between an ultrasonic wave transmitter and an ultrasonic wave receiver, wherein an ultrasonic wave pulse train is transmitted from the ultrasonic wave transmitter at predetermined intervals, The signal received by the ultrasonic wave receiver is used as a shaped wave having one peak value, the timing at which this shaped wave reaches a peak is obtained, and the peak value of the shaped wave is captured and held at this peak timing. An ultrasonic wave detection method characterized by the above. 2. An ultrasonic detector for detecting an object to be measured between an ultrasonic wave transmitter and an ultrasonic wave receiver, wherein the output of the ultrasonic wave receiver is a shaped wave having one peak value. Waveform shaping means, peak detecting means for detecting the timing when the output waveform of the waveform shaping means reaches a peak, and a sample and hold circuit for taking in and holding the output of the waveform shaping means according to the peak timing output by the peak detecting means. And an ultrasonic wave transmitter, wherein the ultrasonic wave transmitter transmits an ultrasonic pulse train at a predetermined interval. 3. The ultrasonic detecting device according to claim 2, wherein the waveform shaping means includes a rectifier, a capacitor that stores the output of the rectifier, and a leak resistor that discharges the capacitor. . 4. The peak detecting means differentiates the output of the waveform shaping means, a zero-cross comparator circuit that detects a zero point of the output of the differentiating circuit, and a pulse by the output of the zero-cross comparator circuit. The ultrasonic detection device according to claim 2 or 3, further comprising a one-shot multivibrator circuit for outputting. 5. A retriggerable multivibrator circuit for outputting a pulse signal having a predetermined pulse width longer than the predetermined interval of the ultrasonic pulse train to the sample and hold circuit from the time when the output of the zero-cross comparator circuit is input. The ultrasonic detecting apparatus according to claim 4, wherein the sample-hold circuit releases the hold value by the pulse signal. 6. The ultrasonic wave transmitter makes the transmission duration of the ultrasonic pulse train shorter than the time it takes for the ultrasonic wave to reciprocate between the ultrasonic wave transmitter and the ultrasonic wave receiver, and The ultrasonic detecting apparatus according to any one of claims 2 to 5, characterized in that the next pulse train arrives at the ultrasonic receiver after a reflected wave of the previous pulse train has almost disappeared at a predetermined interval. .