JP7055922B2 - Ultrasonic measuring device and ultrasonic measuring method - Google Patents

Description

The present invention relates to an apparatus and method for high-precision position measurement using ultrasonic waves, and more particularly to an ultrasonic measuring apparatus and an ultrasonic measuring method for measuring a relative distance between devices by utilizing the propagation time of ultrasonic waves.

Conventionally, there is known a technique of measuring the displacement of an object to be measured in the air at a position separated from a reference point by a certain distance by using ultrasonic waves. Distance measurement by ultrasonic waves is also useful for measurement in places where it is dangerous for people to enter, and for continuous management of distance measurement. , Distance measurement is possible.

In addition, in in-line inspection that non-destructively inspects workpieces on the machining line using ultrasonic waves, not only the uneven shape but also the surface condition can be determined more accurately before machining, and machining is accurate after machining. It is determined whether or not it was performed, for example, the depth of the hole is obtained from the reference position.

For example, an automobile engine manufacturing factory has a processing line for a cylinder block such as a casting, and in the cylinder block manufacturing process, not only the uneven shape but also the surface state can be discriminated and processed in the processing line, that is, in-line. More precise inspections such as determination of proper performance are required.

Further, the one using an ultrasonic displacement sensor using ultrasonic waves as a medium is suitable for use in a transport line because the measurement distance is long. However, the accuracy was lower than that of other methods, and the size of the measurement surface had to be large.

In the technology that uses ultrasonic waves to measure the displacement of a measurement object in the air at a position a certain distance away from the reference point, the object is irradiated with ultrasonic waves, and the transmission time and reception time at the object are received. It is known to measure the displacement of an object based on the difference between the two. In such a displacement measuring device, the method of determining the voltage threshold value for detecting the reception of ultrasonic waves is important in the displacement measurement accuracy, and the error in the determination of the arrival time increases as the reception intensity decreases. Furthermore, due to the influence of attenuation and dispersion of ultrasonic waves in the air, the waveform changes in the path to reach the object, and the waveform change becomes an obstacle in determining the reception time.

Therefore, a displacement measurement method based on the phase difference between the transmitted signal and the received signal is proposed by using the ultrasonic wave of the frequency sweep wave without using the voltage threshold value received by the ultrasonic wave to detect the reception time of the ultrasonic wave. ing. However, the range of measurable displacement is limited to within one wavelength of ultrasonic waves.

Therefore, in order to measure the displacement that changes over a wider range than the wavelength with high accuracy with a resolution sufficiently smaller than the wavelength, it is practically performed twice while switching the phase delay measurement with two different frequencies f1 and f2. It is known to measure the phase using the frequency of "f1-f2", and it is described in Patent Document 1.

Further, it is known to transmit an ultrasonic burst in order to accurately transmit timing information from a waveform generator to a waveform receiver, but the ultrasonic burst has an infinite spread in the frequency spectrum. In contrast, existing waveform generators, wave propagation media and waveform receivers have some non-uniform amplitude frequency characteristics and phase frequency characteristics. Therefore, the rectangular electric signal pulse and the rectangular ultrasonic burst are deformed at the receiving end, and it is difficult to accurately transmit the timing information.

In particular, since the piezoelectric ceramic element used in the ultrasonic measuring device has a narrow band frequency characteristic, the received waveform is strongly distorted. Further, when a region such as the leading edge of the ultrasonic burst, which is strongly affected by the transient response characteristic in terms of signal, is used, the variation in the characteristic of the transmitting / receiving element tends to affect the measurement accuracy and the transmission accuracy of the timing information. Further, since the envelope of the waveform is affected by both the amplitude frequency characteristic and the phase frequency characteristic of the transmission line, when a transmission line having these characteristics is used, the shape of the envelope is likely to change, and as a result. , The transmission accuracy of timing information is reduced.

In order to compensate for this defect and improve the accuracy, an ultrasonic burst that is a growl signal consisting of two frequencies is transmitted as a transmission signal provided with only one point where the phases match. A measuring means called a phase matching method using this phase matching point as a reception time reference point is known, and is described in, for example, Patent Document 2.

Japanese Unexamined Patent Publication No. 2004-191145 Japanese Patent No. 4621924

In the phase matching method, which is the above-mentioned conventional technique, it is important to generate and receive a high-quality beat. Therefore, in Patent Document 2, a plurality of frequency signals are generated by a transmitter, the phase is adjusted, and then the plurality of frequency signals are synthesized. Then, the generated synthetic waveform is stored, D / A converted, and converted into an analog signal. Further, the amplification unit amplifies the analog signal to drive a piezoelectric ceramic vibrating body which is an ultrasonic element, and transmits a plurality of synthesized frequency signals to the receiver by ultrasonic waves.

Therefore, not only the complicated processing is required to generate the composite waveform and the cost is high, but also the amplification unit handles the analog signal, which requires wasteful power consumption. In addition, a good quality beat with less distortion is required. Further, in order to drive the ultrasonic element, a large amplitude and a high output are required, and in order to drive at a high frequency, the ultrasonic wave has to be driven at a relatively low frequency of 40 kHz.

Further, a low-frequency ultrasonic element can generate vibration with low energy, but when it is transmitted to a long distance, its beam diameter becomes large, and the one described in Patent Document 2 is not suitable for measuring the position of a small target. .. Further, a high frequency element having a small beam diameter requires higher energy for driving, and it is extremely difficult to synthesize it in an electric circuit to generate a beat as a high-quality synthesized waveform.

Further, in the case described in Patent Document 2, the measurable direction is only one direction in which the transmitter faces, and it is difficult to measure when the target moves. That is, for that purpose, it was necessary to change the measurement direction of the ultrasonic wave, and the transmitter side had to be movable or a plurality of sensors had to be arranged.

However, even if a plurality of sensors are arranged, it is necessary to change the sensor position every time the measurement point is changed, which is a great disadvantage in terms of time and cost. Further, although measurement based on an image is known as a representative of a sensor having a wide measurement surface, it is often impossible to measure correctly in a line near a machine tool due to contamination of an optical system because light is used. Therefore, the measurement by the image is not suitable for the processing line of the cylinder block or the like.

An object of the present invention is to solve the above-mentioned problems of the prior art, to simplify the generation of a synthetic waveform, to suppress the cost, and to make it possible to easily change the measurable direction. Further, the distance measurement is to be performed with high accuracy even for a plurality of measurement points and moving targets.

In order to achieve the above object, the present invention measures the distance between the transmitter and the receiver by transmitting an ultrasonic beam from the transmitter to the receiver and obtaining the propagation time from the transmission to the reception. In the sound measurement device, the transmitter in which a plurality of vibrators are arranged in an array, a timing adjustment / synchronization circuit for controlling the transmission timing of the vibrators, and ultrasonic waves at the first frequency of the plurality of vibrators. Is transmitted from the oscillator of the first group, the oscillator of the second group that transmits ultrasonic waves at the second frequency among the plurality of oscillators, and the oscillators of the first group and the second group. The reception time reference point is obtained from the phase of the receiver arranged at the position where the ultrasonic beams overlap and the signal obtained by the receiver, and the time when transmission is started by the transmitter and the reception time reference are obtained. The transmitter is provided with an analyzer for obtaining the distance between the transmitter and the receiver based on the points, and the transmission of the vibrator of the first group and the vibrator of the second group is performed by one of the transmission durations. Is a finite ultrasonic burst wave, and the other is a continuous wave.

As a result, a plurality of oscillators are arranged in an array, the oscillators of the first group transmit ultrasonic waves at the first frequency, the oscillators of the second group transmit ultrasonic waves at the second frequency, and the respective ultrasonic beams overlap. Since the reception time reference point is obtained from the phase of the signal obtained by the receiver placed at the position, it is easy to generate the composite waveform in the receiver, the cost is suppressed, and the measurable direction is easily changed. It becomes possible.
Here, the position where the ultrasonic beams overlap means a position where the beat generated by the overlap of the ultrasonic beams can be received, and does not necessarily mean only the position where the ultrasonic beams overlap for the first time.
Further, the distance between the transmitter and the receiver means the distance of the ultrasonic path from the transmitter to the receiver, and does not necessarily mean only the linear distance between the transmitter and the receiver. It's not a thing.

Further, in the above, it is desirable to determine the measurement direction by sequentially delaying the transmission timing of the oscillator by the timing adjustment / synchronization circuit.

Further, in the above, it is desirable to switch the measurement direction by changing the transmission timing of the oscillator by the timing adjustment / synchronization circuit.

Further, in the above, it is desirable that the number of the oscillators in the first group and the oscillators in the second group is determined according to the size of the measurement point.

Further, in the above, it is desirable that at least one of the oscillators in the first group and the oscillators in the second group is an ultrasonic burst wave having a finite transmission duration. ..

Further, in the above, the transmitter includes a switch circuit for driving the oscillator with an on / off signal, and the analyzer obtains a trigger signal from the switch circuit for determining the time when transmission is started by the transmitter. It is desirable to sample the signal obtained by the receiver.
This makes the calculation of the propagation time from transmission to reception more accurate. In addition, the power consumption of the drive circuit can be reduced, and high-frequency ultrasonic waves can be transmitted.

Further, in the above, it is desirable that one of the ultrasonic beams transmitted from the oscillators of the first group and the second group is smaller than the other.
As a result, it is possible to avoid the influence of the direction other than the measurement axis direction.

Further, the present invention is an ultrasonic measurement method for measuring the distance between the transmitter and the receiver by transmitting an ultrasonic beam from a transmitter to a receiver and obtaining a propagation time from transmission to reception. In the transmitter, a plurality of oscillators are arranged in an array, the plurality of oscillators are grouped into a first group and a second group, and the oscillators in the first group have a first frequency and a second. The oscillator of the group has a second frequency, and the transmission of the oscillator of the first group and the oscillator of the second group is an ultrasonic burst wave having a finite transmission duration on one side and a continuous wave on the other side. The reception time is from the phase of the signal obtained by the receiver arranged at the position where the ultrasonic beams transmitted from the oscillators of the first group and the second group overlap with each other. The reference point is obtained, and the distance between the transmitter and the receiver is obtained based on the time when transmission is started by the transmitter and the reception time reference point.
Here, the position where the ultrasonic beams overlap means a position where the beat generated by the overlap of the ultrasonic beams can be received, and does not necessarily mean only the position where the ultrasonic beams overlap for the first time.
Further, the distance between the transmitter and the receiver means the distance of the ultrasonic path from the transmitter to the receiver, and does not necessarily mean only the linear distance between the transmitter and the receiver. It's not a thing.

According to the present invention, a plurality of oscillators are arranged in an array, the oscillators of the first group transmit ultrasonic waves at the first frequency, and the oscillators of the second group transmit ultrasonic waves at the second frequency, and the respective ultrasonic waves are transmitted. Since the reception time reference point is obtained from the phase of the signal obtained by the receiver arranged at the position where the beams overlap, it is possible to easily generate a composite waveform, reduce the cost, and easily change the measurable direction. Is possible. Therefore, the distance measurement can be performed with high accuracy and energy saving even for a plurality of measurement points and moving targets.

Basic configuration diagram of the ultrasonic measuring device according to the embodiment of the present invention. Principle diagram showing the transmission method in one embodiment Configuration diagram according to one embodiment according to the present invention Explanatory drawing of waveform synthesis which concerns on one Embodiment by this invention The figure which shows the measurement example which concerns on one Embodiment by this invention The figure which shows the measuring method of the distance which concerns on one Embodiment by this invention. The figure which shows the application example of the measurement which concerns on one Embodiment by this invention. A block diagram showing signal processing of a transmitter according to an embodiment of the present invention. Block diagram showing transmission / reception signal processing in one embodiment A block diagram showing signal processing of a receiver according to an embodiment of the present invention. Explanatory diagram of position measurement by conventional ultrasonic waves Explanatory drawing showing the method of synthesizing beat waves in the phase matching method by the prior art. Configuration diagram according to another embodiment according to the present invention. Explanatory drawing of waveform synthesis which concerns on other embodiment by this invention

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Ultrasonic distance measurement enables distance measurement in an environment where sound can be transmitted, whether in the air, in liquids, or in metal, and the measurement distance is as long as 60 mm to 10 m. As a result, as various positioning, height control before robot suction, robot arm positioning, steel plate misalignment detection, machine tool positioning, welding position copying control, liquid crystal glass positioning, solar cell substrate transfer stop. Widely used for position measurement.

In addition, under multi-model low-volume production such as automobile production, it is better than assembling products on a dedicated line for each model from the viewpoint of production efficiency, total length of the line, cost related to incidental equipment, and line operation rate. , It is preferable to assemble the product on a multi-model mixed line that can handle multiple models. Further, in an automobile engine manufacturing factory, there is a processing line for a cylinder block such as a casting, and in the cylinder block manufacturing process, measurement is performed at a plurality of points on the processing line, that is, in-line.

Therefore, it is possible to actively change the measurement point, and by using ultrasonic waves, stable measurement is possible even in a bad environment such as oil mist and dust. In addition, the ultrasonic frequency is arbitrarily optimized so that the spot size that matches the object to be measured can be selected.

The ultrasonic measuring device detects the presence or absence of an object and the distance to the object by transmitting ultrasonic waves by a transmitter and receiving them by a receiver. An ultrasonic element is used for transmitting and receiving ultrasonic waves. The ultrasonic element is an element that generates ultrasonic waves by applying electric energy or converts ultrasonic vibration energy into an electric signal. A barium titanate vibrating element that utilizes the piezoelectric phenomenon is used.

The piezoelectric element vibrates when an AC voltage is applied, has a unique frequency, and vibrates efficiently when an AC voltage of the same frequency as that frequency is applied. Generally, 40 kHz is often used, a low frequency is used for measuring a long distance, and a high frequency is used for accurately measuring a short distance.

FIG. 1 is a basic configuration diagram of an ultrasonic measuring device 10 according to an embodiment of the present invention, and FIG. 2 is a principle diagram showing a transmission method. The ultrasonic phased array method is known as a technique for changing the measurement direction of ultrasonic waves. In FIG. 1, both the transmitter 3 and the receiver 1 have an ultrasonic phased array such that the transmitting side vibrating element 3-1, 3-2, 3-3, ... 3-n, and the receiving side vibrating element 1-. 1, 1-2, 1-3, ... 1-n are arranged in a plane in an array.

The transmission timing of the vibrating elements 3-1, 3-2, 3-3, ... 3-n on the transmitting side is controlled by the timing adjustment / synchronization circuit 13, and further, reception is performed from the vibrating elements. As shown in FIG. 2, the vibrating elements 3-1 and 3-2, 3-3, ... 3-n on the transmitting side are the wave 21 produced by the vibrating element 3-1 of the transmitter and the wave produced by the vibrating element 3-2. 22. The wave 23 created by the vibrating element 3-3 is synthesized, and a plurality of ultrasonic waves are transmitted so as to form a single wave 24 running in the intended direction.

Similarly, the receiver 1 synthesizes inputs from a plurality of elements. This makes it possible to flexibly support inspection and measurement of complicated shapes, distance measurement of moving targets, measurement of a plurality of points, and the like. The transmitter 3 is arranged in a planar array with a plurality of vibrating elements 3-1, 3-2, 3-3, ... 3-n, and the receiver 1 has a small number of vibrating elements 1-n. It may be possible, which is advantageous for lowering the price.

FIG. 2 shows a state in which sound waves are transmitted from the transmitter 3 with a slight delay in order, and the sound waves are transmitted while shifting the timing of each vibrating element of the transmitter 3. The phases of the waves 21, 22, and 23 created by the individual vibrating elements are aligned, and the wave 24 is a wave generated by the entire array of the transmitter 3. As shown in the figure, since the transmission timings of the vibrating elements 3-1, 3-2, and 3-3 are deviated, the traveling direction 25 has an angle with respect to the direction of the array.

High accuracy can be achieved by a measuring means called a phase matching method in which an ultrasonic burst that has become a beat signal is transmitted and the phase matching point is used as a reception time reference point. It is important to generate and receive good quality beats. Therefore, a plurality of frequency signals are generated by the transmitter, the phase is adjusted, and then the plurality of frequency signals are combined. Therefore, it is extremely difficult to use the ultrasonic phased array method in order to change the measurement direction of ultrasonic waves.

FIG. 11 is an explanatory diagram of position measurement by conventional ultrasonic waves, and FIG. 12 is an explanatory diagram showing a method of synthesizing beat waves in the conventional phase matching method, which is a feature of the present application with reference to FIGS. 11 and 12. The above is described in detail.

In FIG. 11, the ultrasonic transmitter 50 transmits an ultrasonic burst at about 40 kHz. It is received by the ultrasonic receiver 51 installed at a position separated by a distance L. Since the envelope 52 of the transmission waveform 52 has a rectangular envelope, the start position should be uniquely determined, but the reception waveform 53 is deformed by the attenuation and response characteristics of the receiving side element. In addition, providing frequency selectivity by a filter is indispensable for removing out-of-band noise, improving the signal-to-noise ratio of the system, and extending the measurement distance. Therefore, it is difficult to accurately determine the propagation time by simply setting a threshold value from the envelope 54 of the received signal from the received waveform 53 to obtain the reception time.

The prior art of FIG. 12 eliminates the drawbacks of FIG. 11 and is a measuring means called a phase matching method. The waveforms of the frequencies f1 (60) and the frequency f2 (61) are combined to calculate the beat signal 62 of f1 + f2, which is stored in the memory 64. In the ultrasonic transmitter 63, the data stored in the memory 64 is D / A converted, converted into an analog signal whose amplitude and phase change, and transmitted to the drive circuit 65 (analog amplifier circuit). In the drive circuit 65, the electric power required to drive the piezoelectric ceramic, which is an ultrasonic element, is converted. The ultrasonic element 66 transmits an ultrasonic burst 67.

The composite waveform is generated according to the measurement distance, the characteristics of the ultrasonic element, the size of the target, and the like, and the data stored in the memory 64 is required each time. In the drive circuit 65, since the amplification unit handles an analog signal, wasteful power consumption is required. Further, in order to drive the ultrasonic element, a large amplitude and a high output are required, and in order to drive at a high frequency, the ultrasonic wave has to be driven at a relatively low frequency of 40 kHz.

Further, a low-frequency ultrasonic element can generate vibration with low energy, but when it is transmitted to a long distance, its beam diameter becomes large, and it is not suitable for measuring the position of a small target when driven at about 40 kHz. Furthermore, high-frequency elements with a small beam diameter require higher energy to drive, and it is difficult to synthesize high-frequency signals of about 300 kHz in an electric circuit and drive them with high output without distortion. there were.

When the conventional technique of FIG. 12 is to be applied to the ultrasonic phased array method shown in FIGS. 1 and 2, the composite waveform must be electrically generated and then transmitted while shifting the timing of each vibrating element of the transmitter 3. It must be extremely complicated. Even if it is possible, the transmitter 3 will generate a plurality of frequency signals, adjust the phase, and then transmit the ultrasonic burst 67 by the transmitter 3. Therefore, it becomes difficult to accurately determine the propagation time, and it is extremely difficult to adopt an ultrasonic phased array method that can change the measurement direction after electrically synthesizing a plurality of frequency signals.

Therefore, in the present invention, two different types of ultrasonic waves having a single frequency wave are transmitted in an arbitrary direction by a phased array method, and a beat signal is spatially synthesized on the receiving side. As a result, the transmitter 3 may transmit two types of ultrasonic waves having different frequencies while shifting the timing. Therefore, it becomes easy to realize a phase matching method capable of measuring a distance in an arbitrary direction by using a phased array method.

FIG. 3 is a configuration diagram according to an embodiment, and FIG. 4 is an explanatory diagram of waveform synthesis, in which a group of half of the vibrating elements constituting the array of the transmitter 3 has a frequency f1 which is the first frequency, and the rest. Half of the groups transmit an ultrasonic beam at the second frequency, f2. As shown in FIG. 4, as in FIG. 2, transmission is performed at the frequency f1 while shifting the timing of the oscillators 3-1, 3-2, and 3-3 of the first group. The plane where the phases of the waves created by the frequencies f1 of the vibrating elements 3-1, 3-2, and 3-2 are aligned becomes the wave 41 of the frequency f1, and the traveling direction is as shown by the arrow 43. It should be noted that the grouping of the vibrating elements may not be divided into half, but one may be increased, and a flexible response can be made by deciding according to the measurement location.

On the other hand, the second group oscillators 3-6, 3-7, 3-8 are transmitted at the same time as f1 at the frequency f2 while shifting the timing. The plane in which the phases of the waves created by the frequencies f2 of the vibrating elements 3-6, 3-7, and 3-8 are aligned becomes the wave 42 of the frequency f2, and the traveling direction is as shown by the arrow 44. Both the wave 41 and the wave 42 head toward the vibrating element 1-5 of the receiver 1. As a result, two different frequencies f1 and f2 are spatially combined by the vibrating elements 1-5 of the receiver to receive the beat waveform. The arrival time of ultrasonic waves can be accurately determined by using the phase matching method for the received beat waveform.

FIG. 13 is a configuration diagram according to another embodiment, and FIG. 14 is an explanatory diagram of waveform synthesis according to another embodiment. Half of the groups of vibrating elements constituting the array of the transmitter 3 are grouped at the first frequency. At a certain frequency f1, the other half of the group transmits an ultrasonic beam at a second frequency, frequency f2. The difference is that the vibrating elements transmitted at the frequency f1 and the frequency f2 are alternately arranged with respect to the configurations of FIGS. 3 and 4. As shown in FIG. 14, as in FIG. 2, transmission is performed at the frequency f1 while shifting the timing of the oscillators 3-1, 3-2, and 3-3 of the first group. The plane where the phases of the waves created by the frequencies f1 of the vibrating elements 3-1, 3-2, and 3-3 are aligned becomes the wave 41 of the frequency f1, and the traveling direction is as shown by the arrow 43. Since the traveling direction 43 of the wave of frequency f1 and the traveling direction 44 of the wave of frequency f2 can be made substantially parallel to the configurations of FIGS. 3 and 4, the path from the transmitter 3 to the receiver 1 can be made substantially the same. .. Therefore, the arrival time of the ultrasonic wave can be obtained more accurately regardless of the size of each vibrating element. In the present embodiment, since the frequency f1 and the frequency f2 can be combined and generated from the beginning, the beat itself is propagated by changing the traveling direction of the wave of the frequency f1 and the wave of the frequency f2. Can be changed.

On the other hand, while shifting the timing of the oscillators 3-6, 3-7, 3-8 of the second group, the oscillators are transmitted at the frequency f2 at the same time as f1. The plane in which the phases of the waves created by the frequencies f2 of the vibrating elements 3-6, 3-7, and 3-8 are aligned becomes the wave 42 of the frequency f2, and the traveling direction is as shown by the arrow 44. Both the wave 41 and the wave 42 head toward the vibrating element 1-5 of the receiver 1. As a result, two different frequencies f1 and f2 are spatially combined, and the beat waveform is received by the receiver 1. The arrival time of ultrasonic waves can be accurately determined by using the phase matching method for the received beat waveform.

FIG. 5 shows a measurement example, and the object to be measured 70 has two targets to be measured, such as measurement points 70-1 and 70-2. This is a common example of a cylinder block processing line. Normally, two sets of ultrasonic measuring devices 10 arranged so as to face each of the measuring points 70-1 and 70-2 are required.

In this embodiment, the measurement direction can be switched by changing the transmission timing of the vibration elements 3-1, 3-2, 3-3, ... 3-n on the transmission side by the timing adjustment / synchronization circuit 13. Therefore, it is possible to switch the measurement direction with one ultrasonic measuring device 10 for detection. In addition, the number of vibrating elements to be transmitted may be determined according to the size of the target, which is the measurement point. If the size of the target is large, the number of vibrating elements to be transmitted at frequencies f1 and f2 can be increased. Is possible.

FIG. 6 is a diagram showing a distance measuring method, in which the horizontal axis shows time and the vertical axis shows the distance to the object to be measured 70. As shown in FIG. 2, the transmitter 3 starts the transmission of the vibrating element 3-1 at the time T = 0, and sequentially transmits the vibrating element 3-2 and the vibrating element 3-3 by the time T = t1. The transmission timing is controlled by the timing adjustment / synchronization circuit 13.

Since the transmitter 3 transmits high-frequency ultrasonic waves into the air, an ultrasonic burst wave or an ultrasonic burst wave that is continuous for a predetermined time by a switch circuit that drives the ultrasonic element in a pulsed manner with a high-voltage on / off signal, that is, a rectangular wave, or It is transmitted as a continuous wave of ultrasonic pulses.

The signal obtained by the receiver 1 is sampled by the analyzer, A / D converted, and recorded in the memory. Then, the reception time reference point is obtained by the phase matching method that detects the point where the phase difference becomes 0 from the received waveform. The propagation delay time is obtained based on the time when the transmission trigger is applied to start transmission to the transmitter 3 and the obtained reception time reference point, and the distance from the transmitter 3 to the receiver 1 is determined.

As shown in FIG. 14, since half of the vibrating elements constituting the array of the transmitter 3 are transmitted at the frequency f1 and the other half are transmitted at the frequency f2, the wave 41 and the wave 42 are reflected by the object 70 to be measured. Both head toward the vibrating element 1-5 (FIG. 14) of the receiver 1. As a result, two different frequencies f1 and f2 are spatially combined by the vibrating element 1-5 of the receiver 1 and received as a beat waveform. Assuming that the arrival time at the time of reception is tr, the distances L1 and L2 in FIG. 6 have the speed of sound of the medium as V.

It is obtained as L1 + L2 = (tr-t1) × V.

It should be noted that at least one of the transmissions of the frequency f1 and the frequency f2 of the transmitter 3 may be an ultrasonic burst wave having a finite transmission duration, and the other may be a continuous wave. The distance L1 + L2 may be determined according to the timing of the ultrasonic burst wave. Of course, both may be burst waves.

In the distance measurement, the area where the wave 41 of the transmitter 3 and the ultrasonic beam of the wave 42 overlap is a measurable area. Therefore, when one of them is a continuous wave, increasing the size of the ultrasonic beam expands the measurable area in the measurement axis direction, which may cause an error in the measurement direction. Therefore, it is preferable that the size of one ultrasonic beam is smaller than the size of the other ultrasonic beam, and it is more preferable that the size of the ultrasonic beam as a burst wave is smaller than the size of the ultrasonic beam as a continuous wave.

FIG. 7 shows a measurement example on the machining line, and is an example in which the transmitter 3 and the receiver 1 configured by the ultrasonic phased array serving as the ultrasonic measuring device 10 are arranged on both sides of the machining line. In the line transport process, it is possible to improve the yield such as machining mistakes by measuring the type and size of the workpiece to be transported. Contact type sensors and non-contact image sensors are often used for type discrimination. However, in the case of the contact type sensor, it is necessary to arrange it at a position facing the determination point, and it cannot be installed in the line traveling direction. Also, in the case of an image sensor, there is a possibility of contamination.

According to the present invention, since the measurement direction can be switched, by arranging the ultrasonic measuring devices 10 as a pair as shown in the figure, the measurement points 70-3, 70 on the front surface, the side surface, and the back surface with respect to the traveling direction. -4, 70-5, 70-6 can be measured and detected.
Here, the ultrasonic elements 6 and 7 (see FIG. 9) constituting the ultrasonic measuring device 10 can be used as both the transmitter 3 and the receiver 1 by switching the circuits (transmission circuit, reception circuit). Can be done. Therefore, the transmitter 3 and the receiver 1 may be provided separately, or one ultrasonic measuring device 10 can be used as both the transmitter 3 and the receiver 1 by switching the circuit to the internal ultrasonic element. You can do it.

The measurement is, for example, a distance measurement, and if there is a hole, a step, or the like at the measurement point 70-3, the depth is measured, and it can be determined whether or not the processing is normally performed. Further, if the object to be measured 70 is marked with a step according to its type, the type, product number, etc. of the object to be measured 70 can be discriminated. This makes it possible to flexibly support inspection and measurement of complicated shapes, distance measurement of moving targets, measurement of a plurality of points, and the like.

8 is a block diagram showing details of signal processing of a transmitter, FIG. 9 is a block diagram showing details of signal processing of a transmitter / receiver, and FIG. 10 is a block diagram showing details of signal processing of a receiver. FIG. 8 shows the signal processing of the vibrating elements 3-1, 3-2, 3-3, which are the ultrasonic elements in FIG. 4, and the signal processing of the vibrating elements 3-6, 3-7, 3-8 below. Shows. In addition, what is shown as an ultrasonic element in FIGS. 8, 9, and 10 shows a vibrating element arranged so as to be an ultrasonic phased array.

In FIG. 8, the timing adjustment / synchronization circuit 13 starts the preparation for measurement, and the signal is input to the CPU 4-1. The CPU 4-1 generates a pulse signal which is a square wave. A pulse signal having a frequency f1 (304 kHz) is input to the switch circuit 5-1 to drive the vibrating element 3-1. Since the switch circuit 5-1 does not amplify an analog signal in which amplitude distortion becomes a problem, even if it is a continuous wave, the drive circuit itself does not require unnecessary power consumption and only turns on and off.

The signal of the timing adjustment / synchronization circuit 13 is input to the CPU 4-2 that controls the vibrating element 3-6 of the transmitter 3. The CPU 4-2 generates a pulse burst signal which is a square wave. A pulse burst signal having a frequency f2 (296 kHz) is input to the switch circuit 5-2, and the vibrating element 3-6 is driven for a predetermined time.

The vibrating element 3-1 side generates a pulse signal of 296 kHz, and the vibrating element 3-6 side generates a pulse signal of 304 kHz. Since the switch circuits 5-1 and 5-2 do not handle analog signals such as electrically synthesized roar signals, the drive circuit itself does not require wasteful power consumption and only needs to be turned on and off. Therefore, it is possible to drive with a large amplitude and a high output up to a high frequency of around 300 kHz, there is no distortion, and the measurement accuracy can be increased by an order of magnitude in terms of distance.

As shown in FIG. 8, the beat signal is a combination of a signal having a frequency f1 and a phase φ1 and a signal having a frequency f2 and a phase φ2. The two phases change at high speed at each frequency, but the difference is only between -π and π. Therefore, there is always only one point in which the phase difference becomes 0 in one packet of the beat signal.

In the receiver 1, the signals transmitted by the vibrating element 3-1 side and the vibrating element 3-6 side are synthesized in a section, so that the phase of the combined signal only changes between −π and π. Will be. Since there is one phase matching point in this, the analysis device 9 extracts it from the synthesized waveform as a reception time reference point. As a result, the detection of the reception time reference point can be detected with an accuracy of several μs.

In FIG. 9, the transmitter 3 transmits the pulse signal output by the switch circuit 5 to the analysis device 9 as a trigger signal. It is possible to avoid the influence of the delay time from the timing adjustment / synchronization circuit 13 on the input side of the switch circuit 5 to the switch circuit 5.

The receiver 1 receives a burst-like roar signal obtained by combining the ultrasonic pulse burst wave transmitted from the transmitter 3 and the continuous wave of the ultrasonic pulse transmitted from the transmitter 3 by the ultrasonic element 7. do. The ultrasonic element 7 is connected to the analyzer 9 via a filter 8 that removes out-of-band noise and improves the signal-to-noise ratio of the system.

In the receiver 1 of FIG. 10, the ultrasonic pulse burst wave transmitted by the transmitter 3 and the ultrasonic pulse wave which is a continuous wave are at the position of the receiver 1 (1-5 in FIG. 4), that is, in space. It is synthesized as a beat signal, and the beat signal is received by the ultrasonic element 7. The signal received by the ultrasonic element 7 is sent to the analysis device 9 via the filter 8, and is analyzed by removing noise outside the band, amplifying the signal, and the like.

The analysis device 9 obtains a reception time reference point by the phase matching method. Then, the propagation delay time is obtained based on the time when the transmission trigger is applied by the timing adjustment / synchronization circuit 13 to start the transmission and the obtained reception time reference point, and the distance from the transmitter 3 to the receiver 1 is calculated. decide.

In FIGS. 9 and 10, in the analysis device 9, the received signal in the receiver 1 is sampled based on the trigger signal input from the transmitter 3 and determining the time when the transmission is started, and A / D converted. Perform FFT processing. Next, the phase of the carrier at the time origin of the transmitter 3 is obtained, and the phase coincidence point is obtained from the difference and used as the reception time reference point. If the reception time reference point can be detected, the propagation delay time can be known as the difference between the time when the trigger is applied and the reception time reference point, and the distance from the transmitter 3 to the receiver 1 can be determined.

Since the memory address at the time of A / D conversion corresponds to the reception time, the propagation delay time is obtained by recording the memory write address at the time when the transmitter 3 is triggered by the analyzer 9 and sampling the received signal. It can be obtained from the recorded address at the time.

Since the propagation delay time includes the response time of the ultrasonic element, it is necessary to convert the propagation delay time into a distance in the actual measurement of the distance, and it is necessary to cancel the response time and the like. Therefore, the transmitter 3 and the receiver 1 are installed separated by a predetermined distance, and the relative displacement is measured with the distance as a reference. When measuring the displacement, not the distance between the transmitter and the receiver, for example, move the position of the receiver 1 according to the reference gauge, and use the change in the distance between the transmitter 3 and the receiver 1 as the calibration value. ..

In addition, for this calibration, it is better to change the one corresponding to the reference gauge and measure at several points to obtain the calibration value. Further, since the measurement result of the ultrasonic measuring device 10 is affected by the atmospheric change, it is desirable to record the air temperature with the analysis device 9 and calibrate the distance measurement.

Further, since the phase of the signal is used for the measurement, the measurement error due to the multipath due to the ambient reflected wave is received, but since the burst wave for a short time is used, the signal processing by the analyzer 9 is compared with the duration of the burst. If done fast enough, the measurement time can be close to the duration of the burst. Therefore, if the path difference between the multipath wave and the direct wave is greater than or equal to the measurement distance, the influence of the multipath can be avoided.

Further, when the frequency is the same and the dimensions of the vibrating element are different, the directivity becomes sharp when the vibrating element dimension is large, and the beam width is large at a short distance, but the ultrasonic beam does not spread so much at a long distance. On the other hand, if the size of the vibrating element is small, the directivity becomes dull and the beam width becomes small at a short distance.

Conventionally, methods such as "multiple arrangement of sensors" and "sensors having a wide measurement surface" have been adopted for measurement at a plurality of points. However, even if a plurality of sensors are arranged, it is necessary to change the sensor position every time the measurement point is changed, which is a great disadvantage in terms of time and cost. Further, in the measurement based on the image, since light is used, it is often not possible to measure correctly in the line near the machine tool due to the contamination of the optical system.

In the present invention, by arranging the transmitter 3 and the receiver 1 configured by the ultrasonic phased array, it is possible to actively change the measurement point. In addition, since ultrasonic waves are used, stable measurement is possible even in adverse environments such as oil mist and dust. Furthermore, since the ultrasonic frequency can be optimized arbitrarily, it is possible to select a spot size that matches the object to be measured.

1 Receiver 1-1, 1-2, 1-3, ... 1-n (receiver side) vibration element 3 Transmitter 3-1, 3-2, 3-3, ... 3-n (transmitter side) vibration element (3-1, 3-2, 3-3 First group oscillator)
(3-6, 3-7, 3-8 second group oscillator)
4-1 4-2 CPU
5,5-1,5-2 Switch circuit 6 Ultrasonic element (transmitting side)
7 Ultrasonic element (reception side)
8 Filter 9 Analytical device 10 Ultrasonic measuring device 13 Timing adjustment / synchronization circuit 21, 22, 23, 24, 41, 42 Wave 25 Travel direction 43, 44 Arrow 50, 63 Ultrasonic transmitter 51 Ultrasonic receiver 52 Transmission waveform 53 Received waveform 54 Envelopment line 60 Frequency f1
61 frequency f2
62 Beat signal 64 Memory 65 Drive circuit 66 Ultrasonic element 67 Ultrasonic burst 70 Measured object 70-1, 70-2, 70-3, 70-4, 70-5, 70-6 Measurement points

Claims (8)

In an ultrasonic measuring device that measures the distance between the transmitter and the receiver by transmitting an ultrasonic beam from the transmitter to the receiver and obtaining the propagation time from transmission to reception.
With the transmitter in which a plurality of oscillators are arranged in an array,
A timing adjustment / synchronization circuit that controls the transmission timing of the oscillator, and
Among the plurality of oscillators, the oscillator of the first group that transmits ultrasonic waves at the first frequency and the oscillator.
The second group of oscillators that transmit ultrasonic waves at the second frequency among the plurality of oscillators,
The receiver arranged at the position where the ultrasonic beams transmitted from the oscillators of the first group and the second group overlap with each other.
An analysis in which a reception time reference point is obtained from the phase of a signal obtained by the receiver, and a distance between the transmitter and the receiver is obtained based on the time when transmission is started by the transmitter and the reception time reference point. Equipped with equipment,
The transmission of the oscillator of the first group and the oscillator of the second group is characterized in that one is an ultrasonic burst wave having a finite transmission duration and the other is a continuous wave. .. The ultrasonic measuring apparatus according to claim 1, wherein the measurement direction is determined by sequentially delaying the transmission timing of the vibrator by the timing adjustment / synchronization circuit. The ultrasonic measuring apparatus according to claim 1 or 2, wherein the measurement direction is switched by changing the transmission timing of the vibrator by the timing adjustment / synchronization circuit. The invention according to any one of claims 1 to 3, wherein the number of the oscillators in the first group and the oscillators in the second group is determined according to the size of the measurement point. Ultrasonic measuring device. Claims 1 to 4 are characterized in that at least one of the oscillators in the first group and the oscillators in the second group is an ultrasonic burst wave having a finite transmission duration. The ultrasonic measuring apparatus according to any one of the above items. The transmitter includes a switch circuit that drives the oscillator with an on / off signal.
One of claims 1 to 5, wherein the analyzer obtains a trigger signal for determining a time when transmission is started by the transmitter from the switch circuit, and samples the signal obtained by the receiver. The ultrasonic measuring device according to item 1. According to any one of claims 1 to 6, the size of the ultrasonic beam transmitted from the oscillators of the first group and the second group is smaller than that of the other. The described ultrasonic measuring device. It is an ultrasonic measurement method that measures the distance between the transmitter and the receiver by transmitting an ultrasonic beam from the transmitter to the receiver and obtaining the propagation time from transmission to reception.
In the transmitter, a plurality of oscillators are arranged in an array, the plurality of oscillators are grouped into a first group and a second group, and the oscillators in the first group have the first frequency and the second group. The vibrator has a second frequency, and the transmission of the vibrator of the first group and the vibrator of the second group is an ultrasonic burst wave having a finite transmission duration and a continuous wave on the other. Sends ultrasonic waves
The reception time reference point is obtained from the phase of the signal obtained by the receiver arranged at the position where the ultrasonic beams transmitted from the oscillators of the first group and the second group overlap.
An ultrasonic measurement method for obtaining a distance between a transmitter and a receiver based on a time at which transmission is started by the transmitter and a reception time reference point.

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