JPH09304513A - Distance measuring system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the time resolution in the measurement by an acoustic distance measuring system. SOLUTION: A first signal generator 1A and a second signal generator 1B are connected to a wave transmitter 2 so that the sound waves of two frequencies f1 and f2 can be transmitted from the wave transmitter 2. In the mean time, operators 4A and 4B of two systems are connected to a wave receiver 3, which receives the reflected signals. In the respective operators 4A and 4B, filters 5A and 5B, which can pass only the frequencies f1 and f2 , are provided. Therefore, even if the sound wave of the frequency f2 is transmitted without waiting the receiving of the sound wave of the frequency f1 , confusion is not generated in the operators, and the time resolution of the measurement can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring system using sound waves, and in particular, it uses a vibrator to send sound waves and receive reflected waves from a target reflecting surface, and to send time. The present invention relates to a distance measuring system that measures a distance from a sound velocity and a sound reception time to a reflecting surface.

[0002]

2. Description of the Related Art A conventional distance measuring system comprises, as shown in FIG. 5, a sound wave generator and a sound wave receiver, and the sound wave generator is a signal generator 1 and a piezoelectric wave transmitter. 2, the sound wave receiving unit is composed of a piezoelectric wave receiver 3 and an arithmetic unit 4 for analyzing the received signal. The arithmetic unit 4 includes a filter 5 for extracting only a predetermined signal from the received signal, a comparator 6 for comparing the reference signal from the reference signal generator 11, a counter 8 for counting the reference signal from the clock 7, and an arithmetic unit. It is composed of 9 and 9.

Reference numeral 10 indicates an object to be measured, and the distance is measured by placing the wave transmitter 2 and the wave receiver 3 facing the object to be measured 10. That is, when a voltage that matches the natural frequency of the system is applied to the piezoelectric body of the wave transmitter 2, the piezoelectric body vibrates in the longitudinal direction of the system, and the longitudinal vibration of the vibrator of the wave transmitter 2 is excited to vibrate. Sound waves are transmitted from both end faces of the child. In the signal generator 1, for example, an applied voltage having a natural frequency f ₁ in the longitudinal one-node mode of the system (see FIG. 6) can be applied to the piezoelectric body of the wave transmitter 2.

Further, in the wave receiver 3, when a sound wave arrives at one of both end surfaces of the vibrator, longitudinal vibration of the system is excited, and the piezoelectric body expands and contracts in the longitudinal direction of the system. A potential difference corresponding to Reference numeral 6 denotes a comparator. In the comparator 6, the output of the filter 5 is compared with the reference signal (threshold) from the reference signal generator 11 and when the output becomes larger than the threshold, the stop signal is sent to the counter 8. Is entered.

On the other hand, since the activation signal A ₀ for the signal generator 1 is also input to the counter 8 at the same time, the transmission time and the reception time (the time when the stop signal is input to the counter 8 from the comparator 6) are compared. The number of clocks in between is counted by the counter 8, and the time difference T can be measured by this counted number.

Therefore, a sound wave is transmitted from the vibrator to the surface (the surface of the object 10 to be measured) whose distance is desired to be measured, and the time and the reflected wave from the target surface (the surface of the object 10 to be measured) are received. By measuring the time difference from the wave time, the distance to the target surface using the sound velocity can be measured based on [Equation 1].

## EQU1 ## l = cT / 2 l: distance to be measured c: speed of sound in medium up to object to be measured T: time difference between transmitted wave and received wave

[0007]

By the way, in the above-described distance measuring system which uses the sound wave as the wave transmitter 2 and the wave receiver 3 as the vibrator, the wave is transmitted once and the reflected wave caused by the wave is transmitted. If the next wave is transmitted before the wave is received, it becomes impossible to associate the wave signal with the wave signal. Therefore, as shown in FIG. 7, the second transmitted signal X ₂ must be transmitted after the reflected signal Y ₁ from the target surface of the _first transmitted signal X ₁ is received by the receiver. However, there is a problem in that it cannot be transmitted and the time resolution ΔT _{1 of} measurement cannot be improved. Further, although time resolution can be obtained by disposing a plurality of vibrators having different natural vibration characteristics, installing a plurality of vibrators poses a problem in terms of work or cost. The present invention is intended to solve such a problem.

[0008]

According to the present invention, in a distance measuring system, a sound wave comprising a signal generating means and a wave transmitter which receives a signal from the signal generating means and transmits a sound wave toward an object to be measured. A wave receiving unit consisting of a generator, a wave receiver for receiving the sound wave reflected by the object to be measured, and a calculating means for calculating a distance to the object to be measured by receiving a signal from the wave receiver. The signal generating means comprises a plurality of signal generators for outputting signals of different frequencies, the arithmetic means comprises the same number of arithmetic devices as the signal generators, and each arithmetic device has The means for solving the problem is configured so that it can operate only in response to the frequency of the signal of each of the signal generators.

Further, each arithmetic unit is constructed by connecting a filter, a comparator, a counter and an arithmetic unit in this order, and the filter determines the signal frequency of the signal generator corresponding to the arithmetic unit. The center frequency is used as a means for solving the problem.

Further, the plurality of signal generators are constructed so as to be sequentially operated for each cycle set by the switching cycle setting device, which is a means for solving the problem.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION A distance measuring system as an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a system diagram thereof, FIG. 2 is a diagram showing sound waves in its longitudinal one-node mode, and FIG. FIG. 4 is a diagram showing the sound waves in the vertical three-bar mode, and FIG.

As shown in FIG. 1, in the distance measuring system of this embodiment, the sound wave generator is provided with a first signal generating device 1A and a second signal generating device 1B as signal generating means. The signals from the second signal generators 1A and 1B are configured to be input to one wave transmitter 2.

The first signal generator 1A is adapted to apply an applied voltage of a frequency of the natural frequency f ₁ (see FIG. 2) of the longitudinal one-node mode of the system to the transmitter 2, and The two-signal generator 1B can apply an applied voltage to the wave transmitter 2 at a frequency of the natural frequency f ₂ (see FIG. 3) of the longitudinal three-node mode of the system.

Then, the first and second signal generators 1
In order to alternately (sequentially) actuate A and 1B at predetermined intervals, the first and second signal generators 1A and 1B are first actuated by being actuated by the signals of the switching period setter 12 and the switching setter 12. A switching device 13 is provided which outputs the signal A and the second activation signal B in each predetermined cycle.

The sound wave receiving unit is provided with the same number of first signal processing devices 4A and second signal processing devices 4B as the number of signal generating devices (two systems in this embodiment).
It should be noted that the signals of one wave receiver 3 are input to both arithmetic units 4A and 4B. Each of the arithmetic units 4A and 4B has the same configuration as the conventional arithmetic unit 4 (see FIG. 5).

That is, both arithmetic units 4A and 4B have a first filter 5A, a second filter 5B, a first comparator 6A and a second filter 5A.
The comparator 6B, the first counter 8A, the second counter 8B, the first arithmetic unit 9A, and the second arithmetic unit 9B are connected in this order, respectively, and further common to the first counter 8A and the second counter 8B. Clock 7 of is connected.

The first filter 5A includes the first signal generator 1
A signal frequency f _{1 of} A is used as a center frequency, and the second filter 5B has a second signal generator 1B.
Of the signal frequency f ₂ is used as the center frequency. That is, the first arithmetic unit 4A is the first signal generator 1A.
The system also includes a second arithmetic unit 4B is configured to correspond to the second signal generator 1B system, the frequency f ₁
The first arithmetic unit 4A operates only when the signal (sound wave) of 4 is received, and the second arithmetic unit 4B operates only when the signal (sound wave) of the frequency f ₂ is received.

Further, the activation signals A and B for both the signal generators 1A and 1B are input to the first counter 8A and the second counter 8B as the activation signals of the respective counters.

In the above configuration, the first signal generator 1
Start signal A to either A or the second signal generator 1B
Or when B is input from the switching device 13, a signal for generating a sound wave of frequency f ₁ or f ₂ is transmitted from the signal generator 1A or 1B to which the activation signal A or B is input to the wave transmitter 2. The input sound wave is transmitted from the wave transmitter 2 to the DUT 10.

Sound waves reflected by the object to be measured 10 (reflection signal)
Is received by the wave receiver 3 and input to the first arithmetic device 4A and the second arithmetic device 4B. In both arithmetic units 4A and 4B,
One of the frequencies (f ₁ or f ₂ ) is selected by both filters 5A and 5B, and the corresponding arithmetic unit 4 is selected.
Only A or 4B performs the following calculation.

That is, assuming that a sound wave of frequency f ₁ is transmitted by the first signal generator 1A, the reflected signal is input to the first comparator 6A via the first filter 5A. In the first comparator 6A, the reference signal (threshold value) transmitted from the reference signal generator 11A is compared with the output of the first filter 5A, and when the output of the first filter 5A becomes larger than the threshold value, the stop signal is output. It is output to the first counter 8A.

Since the number of clocks from the time when the start signal A is input to the time when the stop signal is input is counted by the counter 8A, the time from transmission to reception can be measured. . Then, according to this time and the speed of sound in the medium, in the first computing unit 9A, [Equation 1]
The measured distance is calculated based on

Needless to say, when the second signal generator 1B transmits a sound wave of frequency f ₂ , the same calculation is performed in the second processor 4B. In the case of this embodiment, as shown in FIG.
Without waiting for the reflected signal Y ₁ from the target surface of the _first transmitted signal X ₁ transmitted from A to be received by the wave receiver 3,
Even when the first transmitted signal Z ₁ is transmitted from the second signal generator 1B, the reflected signal Y ₁ is processed by comparison with the first signal A in the first arithmetic unit 4A, while the transmitted signal Z ₁ The reflected signal W ₁ is compared with the second signal B in the second arithmetic unit 4B.

As described above, the signal generating means is provided with two signal generators capable of oscillating two kinds of frequencies, while the arithmetic device is provided with two circuits and the filters are provided at the entrances of the arithmetic devices. By specifying the target frequency of the arithmetic device, the transmitted signals X and Y can be associated with the reflected signals (received signals) Z and W, and the time resolution ΔT _{0 of} measurement can be set to the conventional system. It can be improved about twice. Although the number of signal generators and the number of arithmetic devices are two in the above-described embodiment, when the number of signal generators to be set is two or more and the same number of arithmetic devices is set, the time resolution of measurement is further increased. Needless to say, can be improved.

[0025]

As described above in detail, in the conventional distance measuring system, in order to properly correspond the received signal with the transmitted signal, the transmitted wave is transmitted until the reflected wave by the previous transmitted signal is received. Although it had to wait, the distance measuring system of the present invention has an advantage that the time resolution of measurement can be improved as compared with the conventional one by changing the frequency of the transmitted signal.

[Brief description of drawings]

FIG. 1 is a system diagram of a distance measuring system as an embodiment of the present invention.

FIG. 2 is a diagram showing a sound wave in the same vertical one-node mode.

FIG. 3 is a diagram showing sound waves in the same vertical three-bar mode.

FIG. 4 is an explanatory view of the operation.

FIG. 5 is a system diagram of a conventional distance measuring system.

FIG. 6 is a diagram showing a sound wave in the same vertical one-node mode.

FIG. 7 is an explanatory view of the operation.

[Explanation of symbols]

 1A 1st signal generator as signal generating means 1B 2nd signal generator as signal generating means 2 Transmitter 3 Wave receiver 4A 1st computing device as computing means 4B 2nd computing device as computing means 5A 1 Filter 5B 2nd Filter 6A 1st Comparator 6B 2nd Comparator 7 Clock 8A 1st Counter 8B 2nd Counter 9A 1st Calculator 9B 2nd Calculator 10 DUT 11A 1st Reference Signal Generator 11B 2nd Reference signal generator 12 Switching cycle setting device 13 Switching device

Claims (3)

[Claims] 1. A distance measuring system, comprising: a sound wave generator comprising a signal generator and a wave transmitter which receives a signal from the signal generator and transmits a sound wave toward an object to be measured.
The wave receiving section comprising a wave receiver for receiving the sound wave reflected by the object to be measured and a calculation means for calculating a distance to the object to be measured by inputting a signal from the wave receiver, The signal generating means is composed of a plurality of signal generating devices that output signals of mutually different frequencies, the calculating means is composed of the same number of calculating devices as the signal generating devices, and the calculating devices are respectively the signals. A distance measuring system, which is configured so that it can operate only in response to the frequency of the signal of the generator. 2. Each of the arithmetic units is configured by connecting a filter, a comparator, a counter, and an arithmetic unit in this order, and the filter determines the signal frequency of the signal generator to which the arithmetic unit corresponds. The distance measuring system according to claim 1, wherein the distance measuring system is configured to have a center frequency. 3. The distance measuring system according to claim 1, wherein the plurality of signal generators are configured to sequentially operate at each cycle set by the switching cycle setter. .