JPH044559B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an ultrasonic distance measuring device, and particularly to an ultrasonic distance measuring device using a frequency modulation method.

[Conventional technology]

Conventionally, various distance measurement methods using ultrasonic waves have been known, such as a time difference method and a frequency modulation method.

Among these methods, in the frequency modulation method, ultrasonic waves as continuous modulated waves whose frequency changes linearly and continuously with respect to time during a constant sweep period are continuously transmitted to the target object, etc. It has a configuration that receives reflected waves and takes the beat of transmitted waves and received waves. Distance measurement is performed based on the principle that the frequency of the beat signal is proportional to the distance to be measured.

[Problem that the invention seeks to solve]

However, in the above-mentioned conventional technology,
Multiple reflected waves traveling back and forth between the transmitter, receiver, and target object and reflected waves propagating on different routes mix into the received signal as noise, making measurements unstable and significantly reducing measurement accuracy. Ta. This inconvenience becomes more pronounced as the distance is measured, and in the worst case, it becomes impossible to measure.

[Purpose of the invention]

The present invention has been devised in view of the disadvantages of the prior art, and uses ultrasonic waves that have a relatively simple configuration but can significantly eliminate the contamination of multiple reflected waves, thereby improving measurement accuracy. Its purpose is to provide a distance measuring device.

[Means for solving problems]

Therefore, in the present invention, a wave transmitting power source unit that outputs a predetermined frequency modulated signal, a wave transmitter that is activated by the wave transmitting power source unit and outputs a frequency modulated ultrasonic wave, and a frequency modulated It has a transmitter that receives the reflected waves of the transmitted ultrasonic waves and converts them into electrical signals. Then, there is a beat signal generation section that mixes the signal received by this transmitter with the output signal from the wave transmission power supply section and outputs a beat signal, and a beat signal generation section that mixes the signal received by this transmitter with the output signal from the wave transmission power supply section and outputs a beat signal. and a measurement unit that calculates the distance to the target object, and the wave transmission power supply unit generates a burst-like frequency modulation signal in which the first half of one cycle is a frequency modulation signal and the second half is a constant frequency. It has the ability to output
It has this configuration. This aims to achieve the above-mentioned purpose.

[Effect]

The wave transmission power supply section intermittently and periodically outputs a frequency modulated signal whose frequency changes regularly every fixed sweep period to the wave transmission period and beat signal generation section. Thereby, the transmitter emits a frequency-modulated ultrasonic signal toward the target object. The reflected ultrasound reflected by the target object and returned to the receiver is converted into a corresponding electric signal in the receiver, and this is output to the beat signal generator.

The beat signal generating section mixes two signals from the wave transmitting power supply section and the wave receiver, which are outputted with a time difference, to generate a beat signal including distance information. Based on this beat signal, the measuring section calculates the distance to the target object. That is,
This calculation is performed based on the fact that the frequency of the beat signal is proportional to the measured distance.

In this way, the time difference between the sending time and the receiving time of the burst-shaped ultrasonic signal is converted into a beat signal,
Since the distance is measured based on this, the chance of contamination by multiple reflected waves, etc. is significantly reduced, and therefore there are advantages such as highly accurate measurement.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

In FIG. 1, reference numeral 2 indicates a transmitter equipped with an ultrasonic transducer that converts an electrical signal into an ultrasonic signal corresponding to the electrical signal, and reference numeral 4 indicates an ultrasonic transducer that converts the ultrasonic signal into a corresponding electrical signal. This shows a receiver equipped with As shown in the figure, the transmitter 2 and the receiver 4 are arranged at a distance l to be measured from the target object 6, and are arranged so as to be capable of transmitting and receiving ultrasonic signals.

Among these, on the input side of the transmitter 2, the transmitter 2
The structure is configured to generate a burst-like ultrasonic signal from. That is, there is a transmitting power supply section 8 for outputting a burst frequency modulated signal (hereinafter simply referred to as "FM signal"), and an FM signal output from this transmitting power supply section 8 is amplified and transmitted. Vessel 2
An amplifier 10 is connected to output the output signal.
Furthermore, the output side of the wave receiver 4 is equipped with an amplifier 12 for amplifying the received signal.

Furthermore, the output side of the amplifier 12 is equipped for signal processing. First, a part of the output side of the wave transmission power supply section 8 and the output side of the amplifier 12 are as follows.
This leads to a beat signal generating section 14 for generating a beat signal. The output side of the beat signal generating section 14 is equipped with a measuring section 16 for data processing and a display 18 for displaying distance data measured by the measuring section 16.

Furthermore, each of the above-mentioned configurations will be specifically explained.

The wave transmission power supply unit 8 generates a repetitive pulse with a predetermined period T.
_{P _ 1} (T ₁ <T)
A lamp voltage generator 22 outputs a lamp voltage e (see FIG. 2) that varies linearly from e ₁ to e ₂ at f is the initial frequency f ₁
A frequency modulator 2 that outputs an FM signal S ₁ (see Fig. 2, 3, a, b) that changes linearly from f to f ₂ and outputs a signal with a constant frequency f ₁ after T ₁ time has elapsed.
4. Lamp voltage generator 2
2 and the output of the frequency modulator 24 are T ₁ ′ (T ₁ ′=T
−T ₁ ), each initial value e ₁ and f ₁
is set to hold. Here, the frequency modulator 24 is constituted by, for example, a voltage controlled oscillator. Further, the period T is set to be a sufficient time for the transmitted ultrasonic signal to attenuate to a negligible extent.

For this reason, the wave transmission power supply section 8 linearly increases the frequency as time passes during the sweep time _T1 , and returns it to the initial value during the predetermined period _T1 '.
A sawtooth and burst-like intermittent voltage ( _second
2 and 3) to the transmitter 2.

Therefore, the transmitter 2 sequentially converts the FM transmission signal S ₁ inputted through the amplifier 10 into a corresponding ultrasonic signal S _A , and radiates this toward the target object 6 . This emitted ultrasonic signal S _A is reflected by the target object 6 and reaches the receiver 4 as a reflected wave after a time t. In this receiver 4, the received ultrasonic signal S _A is again converted into a corresponding electric signal, and then voltage amplified by an amplifier 14 to FM
It is output to the beat signal generator 14 as a received signal S ₂ (see FIG. 2, 4). Here, if the circuit delay time of the transmitting system and the receiving system is ignored as being minute, the output S ₁ of the amplifier 12 is delayed by approximately t time with respect to the output S ₁ of the frequency modulator 24 (see Fig. 2). ).

On the other hand, the beat signal generating section 14 has a function of receiving the outputs of the frequency modulator 24 and the amplifier 12 and forming a beat signal B _S (see FIG. 2, 5) for both, and this is composed of, for example, a mixer. ing.

Furthermore, the measuring unit 16 includes a counter 26 that counts the frequency of the beat signal B _S and outputs this counted value;
Based on the count value by this counter 26, the distance l
, and a computing unit 28 that calculates the .
Specifically, the arithmetic unit 28 is configured using a microprocessor or the like.

Next, a method of distance calculation performed by the arithmetic unit 28 will be explained.

Now, the propagation speed of the ultrasonic signal in the propagation medium is C
Then, the propagation time t of the ultrasonic signal propagating the distance l between the transmitter and receiver 2, 4 and the target object 6 is t=2l/C (1).

Further, the frequency f ₃ of the beat signal B _S obtained in the beat signal generation unit 14 is determined as f ₃ = [(f ₂ − f ₁ )/T ₁ ]・t = [(f ₂ − f 1 ) in the sweep period T ₁ . ₁ )/T ₁ ]・(2l/C) ...(2). Here, f ₁ and f ₂ are the frequencies of the FM transmission signal S ₁ (see FIG. 2, 3, a).

Then, the above equation (2) becomes l= _CT1f3 /[2( _f2 - _f1 )]...(3), and l can be obtained by _{measuring f3} .

Next, the overall operation of this embodiment will be explained.

As mentioned above, the FM transmission signal S ₁ (see FIG. 2, 3) whose frequency f changes linearly from f ₁ to f ₂ during a certain sweep period T ₁ is transmitted from the wave transmission power supply unit 8 to a predetermined period of time. The signal is output intermittently every period T (T>T ₁ ) (see FIG. 1). Then, excited by the FM transmission signal S ₁ , the ultrasonic signal S _A is emitted from the transmitter 2 toward the target object 6 for a time T ₁ . This ultrasonic signal
The frequency of S _A also changes linearly over time in response to the FM transmission signal S ₁ .

Then, the ultrasonic signal S _A reflected by the target object 6 reaches the transmitter 4 after approximately t seconds and returns to the FM
The signal is converted into a signal and amplified by the amplifier 12 (see FIG. 4).

After that, the beat signal generator 16 generates the transmitted FM transmission signal _S1 and the received FM reception signal.
The beat with S ₂ is taken to form a beat signal B _S . The frequency f ₃ of this signal B _S is proportional to the measurement distance l (see equation (2)).

The frequency f ₃ of this beat signal B _S is counted by the counter 26 of the measuring section 16 . Then, the calculator 28 calculates the distance l according to the above-mentioned equation (3) using the known data set in advance and the count value of the above-mentioned frequency _f3 , and displays this on the display 18. urge

In this manner, in this embodiment, distance calculation is performed immediately every time a burst type FM signal is transmitted/received.
After that, in the next measurement, there are almost no remaining multiple reflected waves from the previous time, so unlike the conventional continuous transmission type, the advantage is that the possibility of being affected by multiple reflected waves, etc. is eliminated as much as possible. be. In addition, the conventional time difference method had problems with measurement accuracy and reproducibility due to the slow rise characteristics of the transmitter and receiver pulses, but in this example, a frequency modulation method was used. As a result, such problems have been greatly improved.

Incidentally, in the above embodiment, a case has been described in which the distance to the target object is determined by reflecting the ultrasonic signal on the target object. However, in the present invention, as shown in FIG. It can also be applied to the case where ultrasonic waves are transmitted and received and the distance l between them is measured.

Note that the FM signal may be a signal whose frequency linearly decreases or increases or decreases over time. Further, the measuring unit 16 may calculate the distance based on the time width in which the beat signal B _S is generated.

〔Effect of the invention〕

Since the present invention is configured and functions as described above,
In addition to being relatively easy to configure, the output of the ultrasonic signal for distance measurement is a burst-like modulated ultrasonic wave, which reduces the effects of multiple reflected waves, etc., as described above, compared to the conventional continuous wave transmission type. It is possible to significantly reduce noise contamination, thereby providing an unprecedented and excellent ultrasonic distance measuring device that can significantly improve measurement accuracy, especially when measuring short distances.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention;
2. FIGS. 1 to 5 are timing charts showing the operation of each part of FIG. 1, and FIG. 3 is an explanatory diagram showing an example of application of the present invention. 2... Wave transmitter, 4... Wave receiver, 6... Target object, 8... Wave transmission power supply section, 14... Beat signal generation section, 16... Measurement section.

Claims (1)

[Scope of Claims] 1. A wave transmitting power source unit that outputs a predetermined frequency modulated signal, a wave transmitter that is activated by being energized by the wave transmitting power source unit and outputs frequency modulated ultrasonic waves; It has a transmitter that receives reflected waves from frequency-modulated ultrasonic waves and converts them into electrical signals, and mixes the signals received by the transmitter with the output signal from the wave transmission power supply section to generate a beat. The wave transmission power supply unit includes a beat signal generation unit that outputs a signal, and a measurement unit that calculates the distance between the transmitter and the reflecting object based on the output of the beat signal generation unit, An ultrasonic distance measuring device characterized by having a function of outputting a burst-like frequency modulated signal in which the first half of one cycle is a frequency modulated signal and the second half is a constant frequency.