JPH1082855A - Object measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect received waveform with an analogical simple circuit constitution even in the case where reflected wave (received waveform) is superposed on the first half part of transmitted waveform and reduce a wrong detection by the compression of a right slope part fluctuated relatively easily, by providing a means for compressing only the latter half part (right slope part) of received wavform, and comparing the received waveform, compressed by this means, with a prescribed threshold value to measure a parameter on a testee, and reduce dispersion caused by reverberation by compressing the right slope part (reverberating wave part) of a reverberation signal so as to be able to cope with the measurement with an inexpensive transmitting device. SOLUTION: In this object measuring device, wave motion is transmitted toward a prescribed detecting direction by a transmitting device 5, and the wave motion reflected by a subject 6 is received by a receiving device 7 to convent it into an electric signal so as to measure a parameter on the subject 6. In this case, a means 11 for compressing only the latter half part of received waveform is provided, and the received waveform compressed by the means 11 is compared with a prescribed threshold value to measure the above- mentioned parameter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for transmitting a wave such as an ultrasonic wave in a predetermined detection direction by a wave transmitting device, and a wave reflected by a test object such as an obstacle by a wave receiving device. The present invention relates to an object measuring apparatus that receives a wave, converts the signal into an electric signal, and measures a parameter (for example, a distance to the object) related to the object.

[0002]

2. Description of the Related Art Conventionally, a wave, for example, an ultrasonic wave transmitted by an object measuring apparatus of the above-described example is reflected by an object to be measured.
Means for detecting the reflected signal at the signal processing stage when receiving the reflected wave include the STC (Sensitivity Time Control) method described in Japanese Patent Application Laid-Open No. Hei 5-87911 and the method disclosed in There is a TTC (Threshold Time Control) method described in -79782.

In the former STC method, the amplification factor of the ultrasonic wave receiving circuit is changed so that the level of the reflected signal from a short distance becomes equal to the level of the reflected signal from a long distance, and the reflected signal is set at a certain threshold value. Is a method for detecting In the latter TTC method, in a region where the background level of the received waveform is not flat, a reflected signal is detected by changing a threshold value as a level with reference to a comparator in accordance with time. .

[0005] As shown in FIG. 5, the waveform of a transmission wave when there is no reception signal is denoted by a, and the reflection b is added to the first half (left slope) of the transmission wave. When the amplification factor of the amplifier in the signal processing unit is attenuated by the STC method, the entire waveform a including the reflected wave b is compressed, and even the reflected wave b to be detected is similarly compressed. (That is, the received waveform) cannot be accurately detected.

When the reflected wave b is added to the first half (left slope) of the transmitted wave as described above, the threshold value (see curve c in FIG. 5) is changed according to time by the TTC method. Even if this is done, there is a problem that it is difficult to detect the above-mentioned reflected wave b (that is, a received waveform) superimposed on the left slope portion.

[0006]

According to the first aspect of the present invention, there is provided means for compressing only the latter half (right slope) of the received waveform, and the received waveform compressed by this means is subjected to a predetermined process. By measuring the parameter relating to the object to be measured in comparison with the threshold value, even if the reflected wave (received waveform) is added to the first half of the transmitted waveform as described above, the analog With the simple and simple circuit configuration, it is possible to accurately detect the received waveform, and to reduce the erroneous detection by compressing the relatively swayable right slope section. It is an object of the present invention to provide an object measurement device that reduces a variation caused by reverberation by compressing a reverberation wave portion, thereby enabling an inexpensive transmission device to cope with the problem.

According to a second aspect of the present invention, in addition to the object of the first aspect of the present invention, the above-described threshold value is configured so that its value decreases with time. The object of the present invention is to provide an object measuring apparatus capable of performing more accurate detection of a received wave because the attenuation of the received wave and the change of the threshold value correspond to the attenuation of the received wave with time.

[0008] The invention according to claim 3 of the invention combines the object of the invention described in claim 1 or 2 with transmitting a pulse in the form of a pulse and based on the time difference between the transmitted wave and the received wave. It is an object of the present invention to provide an object measuring device capable of accurately measuring not only the object detection but also the distance to the object by configuring the apparatus to measure the distance to the object.

According to a fourth aspect of the present invention, in addition to the object of the first, second, or third aspect of the present invention, the use of ultrasonic waves as waves makes it possible to reduce reverberation and fluctuations in transmission and reception levels. It is an object of the present invention to provide an object measuring apparatus which can achieve accurate object measurement or distance measurement even with an ultrasonic wave having a large influence, and is suitable for the ultrasonic wave.

[0010]

According to a first aspect of the present invention, a wave is transmitted by a wave transmitting device in a predetermined detection direction, and the wave reflected by a test object is transmitted to a wave receiving device. An object measuring device that receives and converts the received signal into an electric signal, and measures parameters related to a test object, including a unit that compresses only the latter half of the received waveform. The object measuring device measures the parameter by comparing with a predetermined threshold value.

According to a second aspect of the present invention, in addition to the configuration of the first aspect, the threshold value is an object measuring device whose value decreases with time.

According to a third aspect of the present invention, in addition to the configuration of the first or second aspect, the transmission is performed in a pulse form, and the transmission is performed based on a time difference between the transmission and the reception. It is an object measuring device for measuring a distance to a test object.

According to a fourth aspect of the present invention, in addition to the configuration of the first, second, or third aspect of the present invention, the object is an object measuring apparatus in which the wave is set to an ultrasonic wave. .

[0014]

According to the first aspect of the present invention, the above-described wave transmitting device transmits a wave in a predetermined detection direction (the direction of a test object), and the wave receiving device transmits the wave in the above-described direction. The transmitted wave of (1) receives the wave (reflected wave) reflected by the test object and converts it into an electric signal. However, since the above-described compression means compresses only the latter half (the right slope) of the received waveform, In the case where a reflected wave (received waveform) is superimposed on the first half of the transmitted waveform, the signal of the reflected wave to be detected is relatively moved to the right side of the slope to be in a detectable state. .

Therefore, there is an effect that the reflected wave (received waveform) can be accurately detected by comparing the compressed received waveform with a predetermined threshold value. In addition, there is an effect that reception can be detected with a simple analog circuit configuration, and erroneous detection can be reduced by compressing the relatively sloping right slope. Further, by compressing the right slope portion (reverberation wave portion) of the reverberation signal, variation caused by reverberation can be reduced, and thus, there is an effect that an inexpensive transmission device can be used.

According to the invention described in claim 2 of the present invention,
In addition to the effect of the first aspect of the present invention, the above-mentioned threshold value is configured to decrease with time, so that the reception wave naturally attenuates with time. There is an effect that more accurate wave detection can be performed in response to the change.

According to the invention described in claim 3 of the present invention,
In addition to the effect of the first or second aspect of the present invention, the transmission is performed in the form of a pulse, and the distance to the test object is measured based on the time difference between the transmission and the reception. In addition to the object detection, there is an effect that the distance to the test object can be accurately measured.

According to the invention described in claim 4 of the present invention,
Since the ultrasonic wave is used as the wave in addition to the effect of the invention described in the above-mentioned claim 1, 2 or 3, it is possible to accurately measure the object even if the ultrasonic wave has a large influence such as a reverberation or a fluctuation of the transmission / reception level. The distance measurement can be achieved, and there is an effect that it is suitable for an ultrasonic wave having a short distance measurement range.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the drawings. The drawing shows an object measuring device. In FIG. 1, the object measuring device 1 is connected to a transmitting unit 5 of an ultrasonic transducer 4 via a transmitting unit 3 which forms a transmitting waveform at the next stage of a system control unit 2. ing.

The above-mentioned transmitting unit 5 is a transmitting device for transmitting a wave, that is, an ultrasonic wave, in a pulse shape toward the object 6 (predetermined detection direction). The wave is received by the wave receiving unit 7 as a wave receiving device, and is converted into an electric signal. In this embodiment, the above-described transmitting unit 5 and receiving unit 7 are integrated, but are separately illustrated in FIG. 1 for convenience of explanation.

An amplifier 8, a detector 9, and a comparator 10 are connected in this order to the next stage of the receiving unit 7, and an STC signal generating circuit 11 which operates upon receiving a transmission trigger from the system control unit 2. And a TTC signal generation circuit 12, and a start trigger line 13 and a stop trigger line 14 are provided in the system control unit 2 and the comparator 10.
Are connected to the distance counting unit 15 via each of them.

Here, the above-mentioned amplifier 8 is a variable gain type amplifying means for amplifying a received signal after being converted into an electric signal (amplifier having a variable gain depending on a voltage value applied to a variable gain terminal). Then, the above-described detector 9 performs a detection process for extracting an envelope of the amplified received signal, and the above-described comparator 9 compares the detected signal with a threshold to form a comparison output. I do.

The above-described distance counting section 15 starts counting by a start trigger output at the time of transmission of a transmission trigger, ends counting by a stop trigger as an output of the comparator 10, and determines the transmission time and reception time. The distance to the test object 6 is measured based on the time difference from the time. That is, the distance counting section 15 converts the product of the time difference and the wave propagation velocity into distance information.

Further, the above-described STC signal generating circuit 11 outputs an STC signal (a signal for decreasing the amplification factor in accordance with time) to the amplifier 8 and reflects the received waveform (the transmission waveform a shown in FIG. 2). Only the latter half (right slope) of the waveform b) is compressed, and the received waveform d shown in FIG.
Compress as shown by. The above-described TTC signal generation circuit 12 outputs a TTC signal (a signal whose threshold value decreases with time) to the comparator 10, and changes the threshold curve c shown in FIG. As shown by the curve f.

The illustrated embodiment is configured as described above, and the operation will be described below.

Upon receiving a transmission trigger from the system controller 2, the transmitter 3 forms a transmission waveform, and the transmitter 5
The ultrasonic wave is transmitted in a pulse shape in the direction of. The ultrasonic wave reflected by the test object 6 is received by the wave receiving unit 7,
After being converted into an electric signal, the signal is amplified by an amplifier 8 at the next stage. Since the STC signal is applied to the amplifier 8 and the amplification factor decreases with time, the received waveform shown in FIG. d is a received waveform e in which only the latter part (right slope part) is compressed, and if the reflected wave (received waveform) b is added to the first half of the transmitted waveform a, this detection is desired. The signal of the reflected wave b is relatively shifted to the right.

Since the TTC signal is applied to the comparator 10 and the threshold value decreases with time, the degree of attenuation of the received wave and the change in the threshold value (change from the curve c to the curve f) ) The degree substantially corresponds to the degree.

Therefore, even if the reflected wave b is added to the first half (left slope portion) of the transmitted waveform a as described above, the reflected wave (received waveform) can be accurately obtained by a simple analog circuit configuration. b can be detected, and the distance count 15 is determined by the start trigger application time and the stop from the comparator 10 which is compared and output when the reflected wave b in the compressed state reaches the threshold value f. The distance to the test object 6 can be measured based on the difference between the application points of the trigger (the time difference between the transmitted wave and the received wave).

In short, the above-described wave transmitting device (wave transmitting unit 5)
) Transmits a wave (refer to an ultrasonic wave) in a predetermined detection direction, and a wave receiving device (refer to a wave receiving unit 7) transmits the wave (reflected wave) in which the above-described transmitted wave is reflected by the object 6. The received signal is converted into an electric signal.
) Compresses only the latter half (the right slope) of the received waveform, so that the reflected wave (received waveform) appears in the first half of the transmitted waveform a.
When b is added, the signal of the reflected wave b to be detected can be relatively moved to the right side of the slope (see waveform e).

Therefore, there is an effect that the reflected wave (received waveform) b can be accurately detected by comparing the compressed received waveform e with a predetermined threshold (see curve f). In addition, the received wave can be detected with a simple analog circuit configuration.
In addition, there is an effect that erroneous detection can be reduced by compression of the right slope portion which is relatively easily changed. Further, by compressing the right slope portion (reverberation wave portion) of the reverberation signal, variation caused by reverberation can be reduced, and thus, there is an effect that an inexpensive transmission device can be used.

Since the above threshold value is configured to decrease with time by the TTC signal generation circuit 12, the reception wave attenuates with time, and the attenuation of the reception wave corresponds to the change in the threshold value. Therefore, there is an effect that more accurate wave reception detection can be performed.

Further, the transmission is executed in the form of a pulse, and the distance counting unit 15 measures the distance to the object 6 based on the time difference between the transmission and reception. This has the effect that the distance to the test object 6 can be accurately measured.

In addition, since an ultrasonic wave was used as a wave,
In particular, accurate measurement or ranging of an object can be achieved even with an ultrasonic wave having a great influence of reverberation or fluctuation of a transmitted / received wave level, which is advantageous for an ultrasonic wave having a short ranging range.

FIG. 3 shows the configuration of the ultrasonic sensor head.
The ultrasonic sensor head 16 is provided with a metallic resonance housing 17 for the purpose of obtaining an electromagnetic shielding effect (effect of preventing noise mixing).
A metal back plate 18 is used in the same manner as
Piezoelectric ceramic element 1 as a piezoelectric vibrator inside 18
9 (corresponding to the ultrasonic transducer 4 in FIG. 1) and the receiving circuit unit 20, and a circuit ground (earth unit) 21.
Are connected to the resonance housing 17. Moreover, the inside of the resonance housing 17 is filled with a silicone rubber-based filler 22 that also functions as a vibration damper and a waterproofer, and the back surface is covered with the back plate 18, and the back plate 18 is also grounded. In the figure, reference numeral 23 denotes a cable.

In order to amplify a signal directly obtained from the output terminal of the piezoelectric ceramic element 19 via the lines 19a and 19b in the receiving circuit section 20, to make the signal level sufficiently high, and further to make the impedance sufficiently low for output. Make up.
Since the signal is directly obtained from the output terminal described above, noise is less mixed, and at this stage, the signal level is sufficiently increased by the amplifier 8 (see FIG. 1) and the impedance of the transmission system is reduced, so that the S / N ratio is reduced. Is greatly improved, and high-sensitivity reception becomes possible. Further, since it can be realized with an extremely simple circuit and can be accommodated in a simple structure, the cost is low, the occupied space and the power consumption are small. In addition, a damper effect for suppressing the reverberation of the filler 22 can be secured.

FIG. 4 shows an example of usage of the above-described object measuring apparatus. For example, a plurality of ultrasonic sensor heads 16 shown in FIG. F is ensured, and the object measuring device is configured to be used as a corner sensor and a back sonar for a vehicle. With this configuration, the vehicle 2
This is convenient because the distance between the vehicle 23 and the test object 6 can be measured when the vehicle 3 is parked or when necessary.

In the correspondence between the configuration of the present invention and the above-described embodiment, the wave of the present invention corresponds to the ultrasonic wave of the embodiment, and similarly, the transmitting apparatus corresponds to the transmitting section 5, The wave receiving device corresponds to the wave receiving unit 7, and the parameter is
The means for compressing and corresponding to the distance up to corresponds to the STC signal generating circuit 11 and the means for lowering the threshold value with time corresponds to the TTC signal generating circuit 12. However, the present invention is not limited only to the above configuration. For example, another wave such as an electromagnetic wave or a laser may be used instead of the above-described ultrasonic wave.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an object measuring device according to the present invention.

FIG. 2 is an explanatory diagram of a waveform and a threshold value when a received wave is detected.

FIG. 3 is a sectional view of an ultrasonic sensor head.

FIG. 4 is a schematic plan view showing an example of a usage mode of the object measuring device of the present invention.

FIG. 5 is an explanatory view showing a conventional problem.

[Explanation of Symbols] 5 ... Transmission unit 6 ... Test object 7 ... Reception unit 11 ... STC signal generation circuit 12 ... TTC signal generation circuit

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Satoshi Morioka 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Co., Ltd.

Claims (4)

[Claims] 1. A wave transmitting device in which a wave is directed in a predetermined detection direction by a wave transmitting device, and the wave reflected by an object to be measured is received by a wave receiving device and converted into an electric signal. An object measuring device for measuring a parameter, comprising: means for compressing only the latter half of a received waveform, and comparing the received waveform compressed by the means with a predetermined threshold to measure the parameter. measuring device. 2. An object measuring apparatus according to claim 1, wherein said threshold value decreases with time. 3. The object measuring apparatus according to claim 1, wherein the transmitting is performed in a pulse shape, and the distance to the object to be measured is measured based on a time difference between the transmitting and receiving waves. 4. The method according to claim 1, wherein the wave is set to an ultrasonic wave.
4. The object measuring device according to 2 or 3.