JPS6358188A - Ultrasonic range finder - Google Patents

Abstract

PURPOSE:To obtain a range finder capable of surely detecting even a faint received ultrasonic signal without being affected by a noise by dividing and integrating an ultrasonic transmitting signal and generating a round signal as a comparing reference signal. CONSTITUTION:An ultrasonic transmitting signal generated from a pulse generator 1 is divided by a frequency divider 10. The output signal of the pulse generator 1 and the frequency divider 10 is amplified by an amplifier 2 and transmitted from a transmitter 3 as an ultrasonic wave. The transmitted ultrasonic wave reflected from an object is received by a receiver 4 to become an ultrasonic received signal, which is inputted to a comparator 8 via an amplifier 5 and a discriminator 6. The ultrasonic received signal inputted to the comparator 8 is compared with a round signal that is a comparing reference signal obtained by rounding the output signal of the frequency divider 10 by an integrator 11. As a result, when the ultrasonic received signal is larger than the round signal, the comparator 8 outputs a comparing signal. A counter 9 determines the distance of the object to be measured based on the output timing of the comparing signal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ultrasonic distance measuring device that measures distance using ultrasonic waves.

[Conventional technology]

FIG. 3 is a system diagram of a conventional ultrasonic distance measuring device shown in, for example, the instruction manual for the educational intelligent robot "LAB○" (published by Mitsubishi Electric Semiconductor Software Co., Ltd.). In Fig. 3, 1 is a pulse generator that generates an ultrasonic transmission signal, 2 is an amplifier that amplifies the ultrasonic transmission signal generated by the pulse generator 1, 3 is a transmitter that transmits ultrasonic waves, and 4 is a transmitter. An ultrasonic receiver receives the ultrasonic waves emitted from the transducer 3 and outputs an ultrasonic reception signal, 5 is an amplifier for the ultrasonic reception signal, and 6 is a discriminator for detecting the ultrasonic reception signal and shaping the waveform. 7 is a comparison reference signal generator that generates a comparison reference signal; 8 is a comparator that compares the magnitude of the comparison reference signal output from the comparison reference signal generator 7 and the ultrasonic reception signal;
9 is a counter that counts actual distance data.

Next, the operation of the device configured in this way will be explained. The ultrasonic transmission signal generated by the pulse generator 1 passes through the amplifier 2 and is transmitted as an ultrasonic wave by the transmitter 3.

The emitted ultrasonic waves are reflected by the object and received by the receiver 4 to become an ultrasonic reception signal. This ultrasonic reception signal is amplified by an amplifier 5, passes through a discriminator 6, and is compared in magnitude with a comparison reference signal by a comparator 8. Based on the comparison result, the counter 9 is controlled to obtain distance data.

[Problem that the invention seeks to solve]

In conventional distance measuring devices, the presence or absence of an ultrasonic reception signal is determined based on the magnitude of the comparison reference signal having a certain value. When the signal of period TS) is large, the comparison reference signal (signal of waveform 12) can also be made large, so noise (
It operates normally without being affected by waveform N2 period (TN noise). However, as shown in FIG. 4fb), when the ultrasonic reception signal (signal of waveform 31 period TS) is smaller than the noise (noise of waveform N1 period TH), the comparison reference signal (signal of waveform 13) Since the value of cannot be made smaller than the noise value, there is a problem in that the ultrasonic reception signal cannot be detected using the comparison reference signal, making distance measurement impossible.

The present invention has been made in view of these points, and its purpose is to provide an ultrasonic distance measuring device that can reliably detect even small ultrasonic reception signals without being affected by noise. be.

[Means for solving problems]

In order to achieve such an object, the present invention provides a pulse generator that generates an ultrasonic transmission signal, a transmitter that transmits the ultrasonic transmission signal as an ultrasonic wave, and an ultrasonic wave transmitted from the transmitter. There is a receiver that receives the ultrasound reflected by the object and outputs it as an ultrasound reception signal, a frequency divider that divides the frequency of the ultrasound transmission signal, and a frequency divider that integrates the output signal of this frequency divider. an integrator that outputs a rounded signal; a comparator that compares a mixed signal of the ultrasonic reception signal and noise with the rounded signal; and outputs a comparison signal when the mixed signal is larger than the rounded signal; and this comparison signal. The device is equipped with a counter that measures the distance to the object based on the timing of the output.

[Effect]

In the present invention, an ultrasonic reception signal is detected using a comparison reference signal whose level decreases as time elapses from ultrasonic transmission.

〔Example〕

An embodiment of an ultrasonic distance measuring device according to the present invention is shown in FIG. In FIG. 1, 10 is a frequency divider for dividing the frequency of the pulse generated by the pulse generator, and 11 is an integrator for integrating the output from the frequency divider 10. In FIG. In FIG. 1, the same or equivalent parts as in FIG. 3 are given the same reference numerals.

Next, the operation of this apparatus configured as described above will be explained. The ultrasonic transmission signal generated by the pulse generator 1 is frequency-divided by the frequency divider 10. The output signals of the pulse generator 1 and the frequency divider 10 are amplified by the amplifier 2 and transmitted from the transmitter 3 as ultrasonic waves. The reflected waves of the emitted ultrasonic waves from the object are received by the receiver 4 and become ultrasonic reception signals, which are then sent to the amplifier 5.
．． The signal is input to a comparator 8 via a discriminator 6. The ultrasonic reception signal inputted to the comparator 8 is compared in magnitude with a rounded signal which is a comparison reference signal obtained by rounding the output signal of the frequency divider 10 with an integrator 11, and as a result of the comparison, the ultrasonic reception signal is If the received signal is larger than the rounded signal, the comparator 8 outputs a comparison signal. The counting unit 10 determines the distance to the object based on the output timing of the comparison signal. The rounded signal is a signal whose level decreases over time, and an example thereof is shown by curve 14 in FIG. 2.

As mentioned above, this device uses a rounded signal having a waveform as shown in curve 14 in Fig. 2 as a comparison reference signal instead of a conventional comparison reference signal with a constant value. The ultrasonic reception signal (see waveform S3) can also be reliably compared and detected.

Next, the relationship between the ultrasonic reception signal, the rounded signal, and the noise will be explained in detail. The rounded signal of the curve 14 changes as the distance from the object on which the transmitted ultrasonic wave is reflected increases, that is, from when the ultrasonic wave is emitted by the transmitter 3 until it is reflected by the object and received by the receiver 4. As the time becomes longer, its value becomes smaller. This corresponds to the fact that the level of the received ultrasonic signal becomes smaller as the distance from the object that reflects the ultrasonic wave increases, but the level of the received ultrasonic signal is always higher than the rounded signal. The curve 14 is set to . Noise is mainly caused by the wraparound of ultrasonic waves due to the directivity of the transmitter 3 and receiver 40 and the propagation of ultrasonic waves from the transmitter 3 to the receiver 4 due to mechanical vibrations. Therefore, the longer the time elapses since the call, the smaller the value becomes. Since the relationship between the ultrasonic reception signal, the accented signal, and the noise is as described above, the comparator 8 actually compares the mixed signal, which is a mixture of the ultrasonic reception signal and the noise, and the accented signal, A comparison signal is output when the mixed signal is larger than the rounded signal.

Due to the relationship between the ultrasonic reception signal, the rounded signal, and the noise as described above, it is possible to detect an ultrasonic reception signal with a small value while keeping the value of the rounded signal always larger than the noise value.

Furthermore, as shown in Fig. 2, the noise value reaches its maximum not immediately after the transmission but a little while after the transmission, whereas noise due to mechanical vibration reaches the receiver 4 immediately after the transmission. This is because wraparound noise due to directivity causes a delay due to the propagation time from the transmitter 3 to the receiver 4.

In the above embodiment, the case of distance measurement was explained, but
It may be a device that measures the thickness of an object or a monitoring and alarm device, and the same effects as in the above embodiments can be achieved.

〔Effect of the invention〕

As explained above, the present invention divides and integrates the ultrasonic transmission signal to generate an accented signal as a comparison reference signal, thereby making the comparison reference signal always larger than noise and higher than the ultrasonic reception signal. Since the ultrasonic waves can be made small, even small ultrasonic reception signals can be reliably detected without being affected by noise.

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing an embodiment of the ultrasonic distance measuring device according to the present invention, Fig. 2 is a waveform diagram for explaining its operation, and Fig. 3 is a system diagram showing a conventional ultrasonic distance measuring device. figure,
FIG. 4 is a waveform diagram for explaining the operation. 1... Pulse generator, 2. Amplifier, 3. Transmitter, 4. Receiver, 6. Discriminator, Comparator, 9. Counter, 10. Frequency divider, 11 ...integrator.

Claims (1)

[Claims] A pulse generator that generates an ultrasonic transmission signal, a transmitter that transmits the ultrasonic transmission signal as an ultrasonic wave, and an ultrasonic wave that is reflected by an object among the ultrasonic waves transmitted from the transmitter. a receiver that receives and outputs it as an ultrasonic reception signal;
a frequency divider that divides the frequency of the ultrasonic transmission signal; an integrator that integrates the output signal of the frequency divider and outputs a rounded signal; a mixed signal that is a mixture of the ultrasonic reception signal and noise; A comparator that compares the mixed signal with the accented signal and outputs a comparison signal when the mixed signal is larger than the accented signal, and a counter that measures the distance of the object based on the timing of output of the comparison signal. Ultrasonic distance measuring device.