JPH04177192A - Ultrasonic distance meter - Google Patents

Abstract

PURPOSE:To improve response, prevent erroneous function due to jamming and at the same time increase the accuracy of distance measurement by setting a predetermined center frequency of the ultrasonic pulse signal emitted by itself as a standard. CONSTITUTION:An ultrasonic pulse transmitter and receiver means 20 transmits an ultrasonic pulse signal having a determined center frequency and receives the ultrasonic pulse signal having returned due to the reflection from an object. A distance measurement means 30 measures the distance between the objects based on the information of transmission and reception of the pulse at the transmitter and receiver means 20 and indicates the measured distance on an indicator 6. A judgement means 40 compares the maximum amplitude of the received wave not subjected to band-pass filtering and the amplitude of the received wave subjected to band-pass filtering, judges by the comparison whether or not the received pulse signal wave is the reflection of the transmission by itself and determines with a control means 60 whether or not to indicate on the indicator 6 the distance measured with the distance measurement means 30 based on the judged result.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an ultrasonic distance measuring device that uses ultrasonic pulses to measure and display the distance to a target including obstacles. relates to a device that prevents malfunctions due to interference with other ultrasonic distance measuring devices.

[Conventional technology]

Conventionally, a narrow-band piezoelectric vibrator with high acoustic-to-electrical conversion efficiency has been used in the ultrasonic transducer of this type of device because of the need to obtain high sensitivity. Therefore, as the number of users increases, there is a concern that malfunctions may occur due to interference between devices using the same frequency. As a countermeasure for this, for example, as in Japanese Patent Publication No. 58-40148, the transmission time interval is sequentially and randomly changed, and from the results of several pulse transmission and reception,
A method is known for identifying whether the waves are reflected waves from the own transmission or waves transmitted from other devices of the same type nearby, that is, interference waves or noise. However, while the above example is effective in the case of radio waves, in the case of ultrasonic waves, the speed of sound is slow at approximately 340 m/s, and it takes time to transmit and receive, resulting in a significant deterioration of responsiveness. This is not practical because the probability of malfunction increases as the number of batteries increases.

[Problem to be solved by the invention]

The purpose of the present invention is to provide a distance measuring device using ultrasonic waves that can solve the problems in the conventional technology, improve responsiveness, prevent malfunctions due to interference, and improve ranging accuracy. It is something to do.

[Means to solve the problem]

In order to achieve the above object, the present invention basically employs the following technical configuration. That is, an ultrasonic pulse transmitting/receiving means that transmits an ultrasonic pulse signal having a predetermined center frequency and receives the ultrasonic pulse signal reflected from a target object, and transmitting/receiving the pulse in the ultrasonic pulse transmitting/receiving means. a distance measuring means for measuring the distance to the target based on information on the target object, a means for displaying the measured distance, a maximum value of the amplitude of the received wave that is not band-filtered, and a maximum value of the amplitude of the band-pass filtered received wave. Comparison and determination means for comparing and determining whether or not the received pulse signal wave is a reflected wave from the transmission itself, and displaying the distance measured by the distance measuring means on the display means based on the result of the determination means. This is an ultrasonic ranging device having a control means for determining whether or not.

[For production]

In the present invention, in order to prevent malfunctions due to interference or errors in distance measurement results, a predetermined center frequency of the ultrasonic wave signal transmitted by the self is set as a reference, and the received ultrasonic wave By analyzing the amplitude and center frequency of the pulse signal, if the center frequency of the received ultrasonic pulse signal matches the predetermined center frequency and exhibits the maximum amplitude, it is determined that the transmitted pulse is It is determined that the ultrasonic pulse was reflected from the target and returned, and if it does not fail, it is determined that the received ultrasonic pulse is not the ultrasonic pulse signal transmitted by itself, and the distance measurement result is invalidated. .

〔Example〕

A specific example of a distance measuring device using ultrasonic waves according to the present invention will be described below with reference to the drawings.

That is, FIG. 1 is a diagram showing the basic principle of the distance measuring device according to the present invention, in which an ultrasonic pulse signal having a predetermined center frequency is transmitted, and the ultrasonic pulse signal reflected back from the target object is transmitted. an ultrasonic pulse transmitting/receiving means 20 for receiving the ultrasonic pulse, a distance measuring means 30 for measuring the distance to the target based on information on the transmission and reception of the pulse in the ultrasonic pulse transmitting/receiving means, a means 6 for displaying the measured distance, and a band. A determining means 40 for comparing and determining whether the received pulse signal wave is a reflected wave from its own transmission by comparing the maximum amplitude of the unfiltered received wave with the amplitude of the bandpass filtered received wave; An apparatus comprising a control means 60 for determining whether or not to display the distance measured by the distance measuring means 30 on the display means 6 based on the result; and an ultrasonic distance measuring apparatus according to the present invention shown in FIG. To explain specifically, an embodiment of the present invention is shown in Fig. 1. In Fig. 1, l receives a transmission signal for excitation from an analog switch 2 via a line 2A, and generates a pulsed ultrasonic wave. and reflect the target (
This is an ultrasonic transducer that receives reflected waves from (not shown) and outputs the received signal to line 2A.

Reference numeral 2 denotes a switch whose switching is controlled by a digital input signal 5b outputted to a line 5B, and when transmitting ultrasonic waves, the line is connected to a distance measuring means 30 which is an ultrasonic excitation frequency generating means and has a distance measuring function to be described later. 5A, transmits the excitation frequency signal of the ultrasonic transducer 1 to 2A for a predetermined time, and when receiving ultrasonic waves, is connected to the amplitude means 3 via the line 2B, and receives output from the ultrasonic transducer 1. This is an analog switch that transmits signals from line 2A to line 2B, and is controlled so that when the digital input of line 5B is at "H" level, it is switched to the transmitting side, and when it is at "L" level, it is switched to the receiving side. be.

3 is an amplifier that amplifies the received signal input from line 2B. Further, 4 receives the output of the amplifier 3 from the line 3A, performs envelope detection on the signal, and then compares it with a predetermined voltage level to output a digital pulse to the line 4A at the receiving timing of the ultrasonic pulse. , a reception pulse generation circuit.

5 generates a signal for controlling the timing of transmitting and receiving ultrasonic waves from, for example, the excitation frequency generating means and distance measuring means 30 described above and outputs it via line 5B, and also controls the excitation frequency of the ultrasonic transducer 1 to a predetermined value. value and send that signal to line 5
A, and the output of the reception pulse generation circuit 4 is input from the line 4A, and the distance to the target is measured from the timing of the digital signal generation time on the line 5B and the input time, On the other hand, a first peak detection means comprises a bandpass filter 8 having the predetermined center frequency and into which the received pulse signal is input, and a peak hold circuit 9 that stores the peak value of the pulse signal that has passed through the bandpass filter 8. 42, and a second peak detecting means 43 consisting of a peak hold circuit 7 that directly stores the peak value of the received pulse signal without passing it through a bandpass filter, and detects the first and second peaks. Comparing and determining means 40 that compares the respective outputs of the detecting means 42 and 43, and determines whether or not the received signal is due to the ultrasonic wave transmitted by itself using the center frequency as a reference. 40, and a control means 60 for transmitting measured distance information to the display 6 based on the results.

Reference numeral 6 denotes a display device that inputs distance information from the control means 60 in the central control circuit 5 and displays the distance.

For the comparison/judgment means 40, the received pulse signal is simultaneously inputted from the output of the amplifier 3 to the first and second peak detection means 42, 43 via the line 3A'. For example, by taking the ratio of each peak voltage value output from 42.43, it is determined whether the received signal is due to the ultrasonic wave transmitted by itself based on the value of the ratio, and based on the result, A signal for transmitting information on the measured distance to the display 6 and for setting the center frequency F0 of the bandpass filter 8 to be equal to its own excitation frequency is sent from the ultrasonic excitation frequency generating means 30 via the line 8B. It is supplied to the filter 8.

In other words, the center frequency of the filter can be changed as appropriate.

On the other hand, 7 is a peak hold circuit forming second peak detection means for detecting the peak value of the output of the amplifier 3 and transmitting the value to the control circuit 5.

Further, 8 is a band pass filter which inputs the output of the amplifier 3 from the line 3A' and performs a filter tongue at a predetermined center frequency set by the ultrasonic excitation frequency generating means 30; This is a peak hold circuit that detects and holds the peak value of the output, and together with the bandpass filter 8 forms a first peak detection means, and transmits the detected value to the comparison and determination circuit 41. As described above, in the present invention, in addition to the above-described technical configuration, there is provided a bandpass filter having at least the predetermined center frequency into which the received ultrasonic pulse signal is input, and a peak of the pulse signal that has passed through the bandpass filter. a first peak detecting means consisting of a peak hold circuit that stores a value; and a second peak detecting means consisting of another peak holding circuit that directly stores the peak value of the input pulse signal without passing the input signal through a bandpass filter. and a comparison/judgment means comprising a comparison/judgment circuit that inputs outputs from the first and second peak detection means and compares and makes a decision between the peak values, and the comparison/judgment means For example, the ratio of the peak voltage values output from the first and second peak detection means is calculated, and if the value of the ratio is confirmed to be equal to or higher than a predetermined value, the received pulse is It is determined that the signal is transmitted by the user itself, and the distance measuring means 30 displays the measurement result on the display means 6, and if the value of the ratio is less than a predetermined value, the received pulse signal is This ultrasonic distance measuring device is comprised of a control means 60 that determines that the measurement result is not transmitted by itself and controls the display means 6 not to display the measurement result.

The operation of the present invention will be explained below using FIGS. 1 to 3. FIG. 2 is a timing chart showing the signal timing in each line in FIG. 1, and FIG. 3 is a flow chart showing the operation of this embodiment. In Figure 3,
The part that starts with the terminal and start is the main routine of this embodiment, and the routine that starts with the terminals Judgment 1 and Judgment 2 is a subroutine accessed from the main routine.

Fo in FIG. 3 indicates the excitation frequency value output to line 5A in FIG. 1. F indicates a signal that is output to line 8B in FIG. 1 and determines the center frequency value of bandpass filter 8. That is, in this specific example, the bandpass filter 8 is adjusted to have the same center frequency as the center frequency F0 of the oscillation frequency of the ultrasonic pulse to be transmitted.

Also, n is a counter on the software, which is reset before starting the measurement, and is counted once per transmission of the ultrasonic pulse signal.
It is incremented by one. The basic operation of this embodiment will be explained below using FIG. 2, and the flow of operation will be explained using FIG.

The central control circuit 5 outputs an excitation frequency whose predetermined center frequency is Fo to the analog switch 2 (5a), and the excitation signal (5b) is pulse-modulated during the level of "°H". An excitation frequency signal is applied to the ultrasound transducer 1. The ultrasonic transducer 1 thereby transmits an ultrasonic pulse signal (2a-■) into the air. The transmitted ultrasonic pulse signal is reflected when a reflective target exists, is received by the ultrasonic transducer 1 again (2a-■), and is input to the amplifier 3 via the analog switch 2. The signal (3a) amplified by the amplifier 3 is converted into a digital signal (4a) by the reception pulse generation circuit 4, and is input to the ultrasonic excitation frequency generation means/length measurement means 3o. The length measuring means measures the distance to the target based on the output timing of the pulse 5b and the reception timing of the received pulse 4a--. Further, the signal (3a) amplified by the amplifier 3 is input to a band pass filter 8 forming a second peak detection means 43 consisting of a peak hold circuit 7 and a first peak detection means 42.

The second peak detection means 43 receives the amplified received wave (3a
) hold and output the peak voltage value Vz (7a),
It will be reset with the next transmitted signal. In addition, the bandpass filter 8 has its center frequency FC programmed to be equal to its own excitation frequency F0, so that when it receives ultrasonic waves excited at its own excitation frequency, the attenuation of the peak voltage between its input and output is minimal. Become. Output of bandpass filter 8 (8a
) is input to the peak hold circuit 9 which also forms the second peak detection means 42. The peak hold circuit 9 holds and outputs the peak voltage V1 of the output of the band pass filter 8. On the other hand, the outputs from the first and second peak detection means 42, 43 are input to a comparison/judgment circuit 41, and the two are compared. In other words, in this specific example, the first and second peak detection means 42 and 43 and the comparison and judgment circuit 41 constitute a comparison and judgment means 4o. The comparison/judgment circuit 41 receives the peak voltage values (■) and (2) which are the outputs from the first and second peak detection means 42.43, and the ratio of both data, that is, the value of V+/Vz, is predetermined. It is determined whether or not the value is larger than the predetermined value RT. Since the gain of the bandpass filter 8 is l, V+/Vz takes a value of 1 or less, and is maximum when the received wave is due to its own excitation. Therefore, when it is greater than the predetermined determination level RT, it is determined that the received wave is due to its own excitation.

When it is determined that the reflected wave is due to its own excitation, the central control circuit 5 drives the display control means 60 to display on the display means 6 the distance to the reflecting target obtained from the received pulse 4a.

Further, when the ratio value V + /V z is smaller than RT, it is determined that the received wave is not due to self-excitation, and the distance is not displayed. Through the above basic operations, it is possible to determine whether or not the signal is a reflected signal due to its own excitation.

Now, the flow of the actual operation is shown in FIG. When the power is turned on, the control circuit operates from the terminal start in the flowchart. First, in step 301, the excitation frequency value F0 output from line 5A and the center frequency value Fc of the bandpass filter set from line 8B are set to be equal (Fo=F
c) Set to a predetermined value. Next, in step 302, a counter n on the software is reset. Next step 3
At step 03, reception is performed for a predetermined time in order to monitor whether or not other ultrasonic pulse devices are currently operating in the vicinity.

Next, in step 303, it is determined whether or not there is a received wave. If there is no received wave, the process proceeds to step 305, and if there is a received wave, a subroutine "determination 1" is performed in step 304. In "Judgment 1", in step 311, the received wave V+/
Vz is determined and compared with a predetermined value RT. and a predetermined value R
If it is larger than T, it is determined that the received ultrasonic wave is excited by a frequency equal to the frequency F0 that the user plans to use from now on, and the excitation frequency F is immediately set at step 312.

Then, the center frequency Fc is changed to another frequency, and the process returns to the main routine. When it is smaller than the predetermined value RT, it is determined that although another ultrasonic pulse device is currently operating, its excitation frequency is different from the own Fo, and the process returns to the main routine without doing anything.

Next, in step 305 of the main routine, transmission is performed at the predetermined excitation frequency F0. Next, in step 306, reception is performed for a predetermined period of time, and if there is no received signal, the process advances to step 308. If there is a received signal, step 307
The subroutine "Judgment 2" is executed. In "Judgment 2", first in step 321, L/V
z and a predetermined value RT are compared. Vl/V2 is a predetermined value RT
If it is larger than that, it is determined that the received signal is due to the reflection of the ultrasonic wave transmitted by the user, and in step 322, the distance to the target is determined from the timing of the transmitted pulse and the received pulse 4a as normal reflected reception. , transmits distance information to the display 6 and displays the distance.

When VI/Vz is smaller than the predetermined value RT, it is determined that the received signal is an interference wave from another device, and the process returns to the main routine without displaying anything. In the main routine, a counter n is incremented at step 308. Counter n is incremented every time it is transmitted. Next, in step 309, it is determined whether the counter n and the constant k are equal. Here, when n=, the process starts from step 302, and when n≠, the process starts from step 305. That is, every predetermined number of transmissions (k), only reception is performed without transmitting, and it can be determined whether or not other ultrasonic pulse devices that emit interference waves are currently operating in the vicinity. Therefore, distance measurement without malfunction is possible even when similar devices that emit ultrasonic pulses in the vicinity are operating.

In this embodiment, the control circuit 5 may perform its operation on software, but it is also possible to use only a hardware logic configuration.

FIG. 4 shows another specific example according to the present invention. In FIG. 4, an ultrasonic transducer 1, an analog switch 2, a reception pulse generation circuit 4, a display 6, a peak hold circuit 7 forming a second peak detection means, and a bandpass forming a first peak detection means. The filter 8 and peak hold circuit 9 are
Both are the same as the first embodiment, but the amplifier is the same as the first embodiment.
It has a two-stage cascade configuration consisting of an amplifier (3') and a second amplifier (3'), and the same circuits 7, 8, 9 that calculate the peak voltage value ratio L/Vz for each output. ．．
and 7', 8', and 9' are arranged in parallel. In other words, a set of identical detection means corresponding to the set of first and second peak detection means 42 and 43 is separately provided. With this configuration, L/Vz due to reception amplifier saturation can be reduced.
It is possible to prevent deterioration of accuracy. The circuit configuration within the central control circuit 5' in this specific example is similar to the configuration of the central control circuit 5 in FIG. In other words, if the second amplifier 3'' is saturated, the ratio V+/Vz based on its output will be an incorrect value, so as a countermeasure, when the second amplifier 3'' is saturated, the output is switched to the output of the first amplifier 3', which has a lower gain stage. , by determining the ratio V r /V z, it is possible to make a determination with a wide dynamic range.

〔effect〕

As described above, in the present invention, even if there is an ultrasonic oscillator with a center frequency that is the same as or similar to the center frequency emitted by itself, it is detected, and the center frequency is changed to a different center frequency and then the ultrasonic oscillator transmits. Therefore, there is no malfunction due to interference, and the distance to the target can be measured and displayed quickly and accurately.

[Brief explanation of drawings]

FIG. 1 is a block diagram schematically showing an ultrasonic distance measuring device according to the present invention. FIG. 2 is a diagram showing pulse waveforms used in the present invention. FIG. 3 is a diagram showing a program routine used in the present invention. FIG. 4 is a diagram showing another specific example of the present invention. 1... Ultrasonic transducer, 2... Analog switch,
3... Amplifier, 4... Reception pulse generating means, 5... Central control circuit, 6... Display means, 7.
9...Peak hold circuit, 8...Band filter, 42...First peak detection means, 43...Second peak detection means, 20...Transmission/reception means, 30...-Distance measurement means, and excitation pulse ordering means, 40.
... Comparison and judgment means, 41... Comparison and judgment circuit, 60.
...Display means control means.

Claims (1)

[Claims] 1. An ultrasonic pulse transmitting/receiving means for transmitting an ultrasonic pulse having a predetermined center frequency and receiving the ultrasonic pulse signal reflected and returned from a target object; A distance measuring means for measuring the distance to the target based on information on the transmission and reception of the pulse in the means, a means for displaying the measured distance, a maximum amplitude value of the received wave that is not band-filtered, and a maximum value of the amplitude of the received wave that is not band-pass filtered. Comparison/determination means for comparing and determining whether the received pulse signal wave is a reflected wave from its own transmission based on the maximum value of the amplitude, and a distance measured by the distance measuring means based on the result of the determination means. An ultrasonic ranging device characterized by having a control means for determining whether or not to display information on a display means. 2. Ultrasonic pulse transmitting/receiving means for transmitting an ultrasonic pulse signal having a predetermined center frequency and receiving the ultrasonic pulse signal reflected and returned from a target object, and transmitting/receiving the pulse in the ultrasonic pulse transmitting/receiving means. a distance measuring means for measuring the distance to the target based on information on the object, a means for displaying the measured distance, a bandpass filter having at least the predetermined center frequency into which the received ultrasonic pulse signal is input, and the bandpass filter. a first peak detecting means consisting of a peak hold circuit that stores the peak value of the pulse signal that has passed through the input signal; a second peak detection means and a comparison judgment means for comparing the outputs from the first and second peak detection means, and if the comparison value by the comparison judgment means is greater than a predetermined value, the received pulse signal is It is determined that the received pulse signal has been transmitted, and the result measured by the distance measuring means is displayed on the display means, and if the comparison value is less than a predetermined value, the received pulse signal is not transmitted by the receiver itself. an ultrasonic distance measuring device comprising: a control means that determines that the measured result is displayed on the display means;