JP2820315B2 - Ultrasonic ranging device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to an ultrasonic ranging device that measures and displays a distance to a target (object) including an obstacle using an ultrasonic pulse. The present invention relates to a device for preventing a malfunction due to interference with another ultrasonic distance measuring device.

[Conventional technology]

Conventionally, a narrow-band piezoelectric vibrator having high acoustic-electric conversion efficiency has been used for the ultrasonic transducer of this type of device because of the need to obtain high sensitivity. Therefore, an increase in the number of users may cause a malfunction due to interference between devices using the same frequency. As a countermeasure, for example, as in Japanese Patent Publication No. 58-40148, the transmission time interval is sequentially changed at random, and based on the result of transmitting and receiving several pulses, the reflected wave due to its own transmission or another similar type nearby. There is known a method for identifying a transmission wave from a device, that is, an interference wave or noise. However, the above example is effective in the case of radio waves, but in the case of ultrasonic waves the sound speed is as slow as about 340 m / sec,
It takes a long time to send and receive, resulting in significant deterioration of responsiveness,
In addition, it is impractical because the number of users increases and the probability of malfunction increases.

[Problems to be solved by the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a ranging device using an ultrasonic wave which can solve such problems in the prior art and can improve the responsiveness and at the same time, prevent a malfunction due to interference and improve the ranging accuracy. Is what you do.

[Means for solving the problem]

The present invention basically employs the following technical configuration to achieve the above object. That is, while transmitting an ultrasonic pulse signal having a predetermined center frequency,
Ultrasonic pulse transmitting and receiving means for receiving the ultrasonic pulse signal reflected and returned from the target, measuring means for measuring a distance to the target based on information on transmission and reception of the pulse in the ultrasonic pulse transmitting and receiving means, Means for displaying the distance obtained, comparing the maximum value of the amplitude of the reception wave that is not band-pass filtered with the maximum value of the amplitude of the reception wave that is band-filtered, and determines whether the reception pulse signal wave is a reflected wave due to its own transmission. An ultrasonic ranging apparatus having comparison determining means for comparing and determining whether or not the distance is measured, and control means for determining whether or not a distance measured by the distance measuring means is displayed on the display means based on a result of the determining means. .

(Operation)

In the present invention, in order to prevent malfunction due to interference, or errors in the result of distance measurement, etc., a predetermined center frequency of an ultrasonic pulse signal transmitted by itself is set as a reference, and a received ultrasonic pulse signal is set. By analyzing the amplitude of the ultrasonic pulse signal and the center frequency thereof, if the center frequency of the received ultrasonic pulse signal matches the predetermined center frequency and indicates the maximum amplitude, the pulse transmitted by the subject itself is transmitted to the target. If it is determined that the reflected ultrasonic wave has returned, and if they do not match, 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〕

Hereinafter, a specific example of a distance measuring apparatus using an ultrasonic wave according to the present invention will be described with reference to the drawings.

That is, FIG. 1 is a view showing the basic principle of the distance measuring apparatus according to the present invention, in which an ultrasonic pulse signal having a predetermined center frequency is transmitted, and the ultrasonic pulse signal reflected from a target and returned. , An ultrasonic pulse transmitting / receiving means 20, a distance measuring means 30 for measuring a distance to a target based on information on transmission / reception of the pulse in the ultrasonic pulse transmitting / receiving means, a means 6 for displaying the measured distance, a band Comparing the maximum value of the amplitude of the non-filtered received wave with the amplitude of the band-filtered received wave, and comparing and judging whether or not the received pulse signal wave is a reflected wave due to its own transmission; and And control means 60 for determining whether or not the distance measured by the distance measuring means 30 based on the result is displayed on the display means 6.

Further, the ultrasonic ranging device shown in FIG. 1 according to the present invention will be specifically described. FIG. 1 shows an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a pulse receiving a transmission signal for excitation from an analog switch 2 via a line 2A, transmitting a pulse ultrasonic wave, receiving a reflected wave from a reflection target (not shown), and receiving the signal. Signal line 2A
This is an ultrasonic vibrator for outputting to an ultrasonic transducer.

Reference numeral 2 denotes a switch whose switching is controlled by a digital input signal 5b output to a line 5B, which is an ultrasonic excitation frequency generating means when transmitting an ultrasonic wave, and which is connected to a distance measuring means 30 having a distance measuring function to be described later. 5A, which transmits the excitation frequency signal of the ultrasonic transducer 1 to the 2A for a predetermined time, and which is connected to the amplitude means 3 via the line 2B when receiving the ultrasonic wave, and which is received from the ultrasonic transducer 1 Signal line 2A
An analog switch for transmitting the signal from the line 5B to the line 2B. The analog switch is controlled to switch to the transmitting side when the digital input of the line 5B is at the "H" level and to switch to the receiving side when the digital input of the line 5B is at the "L" level.

Reference numeral 3 denotes an amplifier for amplifying a reception signal input from the line 2B. 4 receives the output of the amplifier 3 from the line 3A, envelope-detects the signal, and then compares the signal with a predetermined voltage level to output a digital pulse at the reception timing of the ultrasonic pulse to the line 4A. , A reception pulse generation circuit.

Reference numeral 5 denotes a signal for controlling the timing of transmission and reception of ultrasonic waves, for example, generated from the above-described excitation frequency generating means and distance measuring means 30 and output via a line 5B.
The excitation frequency is set to a predetermined value, the signal is output via a line 5A, the output of the reception pulse generation circuit 4 is input from a line 4A, and the digital signal generation time on the line 5B and the input time From the timing, the distance to the target is measured, and on the other hand, the bandpass filter 8 having the predetermined center frequency to which the received pulse signal is input and the peak value of the pulse signal passing through the bandpass filter 8 are stored. A first peak detecting means 42 comprising a peak hold circuit 9 which performs the above-mentioned operation, and a second peak comprising a peak hold circuit 7 which directly stores the peak value of the received pulse signal without passing the received pulse signal through a band filter. Detecting means 43, and said first and second peak detecting means.
The comparison and judgment means 40 which has comparison judgment means 40 for comparing each output of 42 and 43, and judges whether or not the compared and received signal is due to the ultrasonic wave transmitted by itself based on the center frequency. And a control means 60 for transmitting the measured distance information to the display 6 based on the result.

Reference numeral 6 denotes a display for inputting distance information from the control means 60 in the central control circuit 5 and displaying the distance.

For such a comparing and judging means 40, the received pulse signal is applied to the output of the amplifier 3 via the line 3A '.
And the second peak detecting means 42 and 43 are simultaneously inputted, and the respective peak value voltage values output from the respective peak detecting means 42 and 43 are, for example, ratios. Determine whether it is due to the transmitted ultrasound,
The result Te also DOO stamen, center frequency F ₀ is the signal to be set equal to their excitation frequency of the display unit 6 transmits the information of the distance measured in the respect, also band-pass filter 8 the ultrasonic excitation frequencies It is supplied from the generating means 30 to the filter 8 via the line 8B.

That is, the center frequency of the filter can be appropriately changed.

On the other hand, reference numeral 7 denotes a peak hold circuit which forms second peak detection means for detecting the peak value of the output of the amplifier 3 and transmitting the detected value to the control circuit 5.

Reference numeral 8 denotes a band-pass filter which receives the output of the amplifier 3 from the line 3A 'and performs filter tongue at a predetermined center frequency set by the ultrasonic excitation frequency generating means 30. A peak hold circuit that detects and holds the peak value of the output, and forms first peak detection means integrally with the bandpass filter 8;
The detection value is transmitted to the comparison and determination circuit 41. As described above, in the present invention, in addition to the above-described technical configuration, a band filter having at least the predetermined center frequency for inputting the received ultrasonic pulse signal and a peak of the pulse signal having passed through the band filter are provided. A second peak hold circuit for storing the peak value of the input pulse signal directly without passing the input signal through a band-pass filter; And a comparison / judgment circuit comprising a comparison / judgment circuit which receives an output from the first and second peak detection means and compares and judges the peak values. In the above, for example, a ratio of peak voltage values output from the first and second peak detecting means is taken, and it is confirmed that the value of the ratio is equal to or more than a predetermined value. If the received pulse signal is received, it is determined that the received pulse signal is transmitted by itself, the result measured by the distance measuring means 30 is displayed on the display means 6, and the value of the ratio is equal to or less than a predetermined value. In this case, it is an ultrasonic distance measuring device comprising a control means 60 for judging that the received pulse signal is not transmitted by itself and controlling the measurement result not to be displayed on the display means 6. .

The operation of the present invention will be described below with reference to FIGS. FIG. 2 is a timing chart showing signal timing in each line in FIG. 1, and FIG. 3 is a flowchart showing the operation of this embodiment. In FIG. 3, a portion starting with a terminal and a start is a main routine of the present embodiment, and a routine starting with a determination 1 and a terminal 2 is a subroutine accessed from the main routine. F _{0 in} FIG. 3 indicates the excitation frequency value output on line 5A in FIG. F _c denotes a signal for determining the output to the first drawing line 8B, the center frequency value of the band-pass filter 8. That is to adjust the same center frequency as the center frequency F ₀ of the oscillation frequency of the ultrasonic pulses to be transmitted so as to have the band-pass filter 8 in this example.

Also, n is a counter on the software, which is reset before the start of the measurement, and is incremented by one for each transmission of the ultrasonic pulse signal. Hereinafter, the basic operation of this embodiment will be described with reference to FIG. 2, and the flow of the operation will be described with reference to FIG.

From the center control circuit 5, a predetermined center frequency for the analog switch 2 outputs the excitation frequency is F ₀ (5a), the excitation signal (5b) is between pulse modulation level "H" An excitation frequency signal is applied to the ultrasonic transducer 1. The ultrasonic vibrator 1 thereby transmits an ultrasonic pulse signal (2a-) into the air. The transmitted ultrasonic pulse signal is reflected when the reflective target exists, is received again by the ultrasonic transducer 1 (2a-), and is input to the amplifier 3 via the analog switch 2. The signal amplified by the amplifier 3 (3a) is converted into a digital signal (4
a) is input to the ultrasonic excitation frequency generating means and length measuring means 30. The length measuring means measures the distance to the target from the output timing of the pulse 5b and the reception timing of the reception pulse 4a-. The signal (3a) amplified by the amplifier 3 is input to the band-pass filter 8 forming the second peak detecting means 43 and the first peak detecting means 42 comprising the peak hold circuit 7. The second peak detection means 43 holds and outputs the amplified peak voltage value V ₂ (7a) of the received wave (3a), and is reset by the next transmission signal.
Further, the band-pass filter 8 whose center frequency F _c which is equal programmed to their excitation frequency F _0, the attenuation of the peak voltage between the input and output when receiving the ultrasonic wave excited by their excitation frequency Will be minimal. The output (8a) of the band pass filter 8 is input to a peak hold circuit 9 which also forms the second peak detecting means 42. The peak hold circuit 9 holds and outputs the output peak voltage V ₁ of the band pass filter 8. On the other hand, the outputs from the first and second peak detecting means 42 and 43 are input to a comparison / judgment circuit 41, which compares them. That is, in this specific example, the first and second peak detecting means 42 and 43 and the comparing and judging circuit 41 constitute the comparing and judging means 40. Peak voltage value V ₁ and V ₂ is the output from the comparison determination circuit first and second peak detecting means 42, 43 at 41 is input, the ratio i.e. the value of V ₁ / V ₂ of the two data previously It is determined whether or not the value is greater than a predetermined value RT. Since the gain of the band-pass filter 8 is 1, V ₁ / V ₂ takes a value of 1 or less and becomes maximum when the received wave is due to its own excitation. Therefore, when it is larger than the predetermined determination level RT, it is determined that the received wave is the one received by the self-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 the distance to the reflection target obtained from the received pulse 4a on the display means 6.

When the ratio value V ₁ / V ₂ is smaller than RT, it is determined that the received wave is not a received wave due to its own excitation, and the distance is not displayed. With the basic operation described above, it can be determined whether or not the signal is a reflection signal due to its own excitation.

FIG. 3 shows an actual operation flow. When the power is turned on, the control circuit operates from the terminal start in the flowchart. First, it sets the excitation frequency value F ₀ equal to the center frequency value Fc of the bandpass filter is set from the line 8B (F ₀ = F _c) a predetermined value to be outputted from the line 5A in step 301. Next, at step 302, the counter n on the software is reset. Next, at step 303,
The reception is performed for a predetermined time to monitor whether or not another ultrasonic pulse device is operating in the vicinity. Then 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. If the received wave is present, the subroutine "determination 1" is performed in step 304. It is compared with a predetermined value RT seeking V ₁ / V ₂ of the received wave at "determination 1" in step 311.
And when greater than a predetermined value RT is received ultrasonic is determined that what he is excited by a frequency equal to the frequency F ₀ of the plan to use from now, immediately excitation frequency F ₀ and the center at step 312 make changes to the other frequency of the frequency F _c returns to the main routine. When smaller than the predetermined value RT, although the other ultrasonic pulse device is currently operating, its excitation frequency is determined to be different from its own F ₀ ,
Do nothing and return to the main routine. Next At a step 305 of the main routine, performs the transmission already at the excitation frequency F ₀ which is determined. Next, reception is performed for a predetermined time in step 306, and if there is no reception signal, the process proceeds to step 308. If there is a received signal, a subroutine "determination 2" is executed in step 307. In “determination 2”, first, in step 321, V ₁ / V ₂ is compared with a predetermined value RT, similarly to “determination 1”. When V ₁ / V ₂ is larger than the predetermined value RT, it is determined that the received signal is due to the reflection of the ultrasonic wave transmitted by itself, and step 322
As a regular reflection reception, transmit pulse and receive pulse 4a
The distance to the target is obtained from the timing of (1), and distance information is transmitted to the display 6 to display the distance. When V ₁ / V ₂ is less than the predetermined value RT is the received signal is determined to be interference from another device, returns to the main routine without performing the display. In the main routine, at step 308, the counter n
Is incremented. The counter n is incremented each time transmission is performed. Next, at step 309, it is determined whether or not the counter n and the constant k are equal. Here, when n = k, the processing is executed from step 302, and when n ≠ k, step 305 is executed.
Run from That is, for every predetermined number (k) of transmissions,
Only reception is performed without transmission, and it can be determined whether or not another ultrasonic pulse device that emits an interference wave in the vicinity is currently operating. Therefore, even when a similar device that emits an ultrasonic pulse in the vicinity operates, a distance measurement without malfunction can be performed.

In the present embodiment, the control circuit 5 may perform its operation on software, but may also have 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 generating circuit 4, a display 6, a peak hold circuit 7 constituting second peak detecting means, and a band pass forming first peak detecting means. Filter 8 and peak hold circuit 9
Are the same as those in the first embodiment, except that the amplifier has a two-stage cascade configuration including a first amplifier (3 ') and a second amplifier (3 "). The same circuits 7, 8, 9 and 7 ', 8', 9 'for determining the ratio V ₁ / V ₂ of peak voltage values are arranged in parallel, that is, the first and second peak detecting means 42. A separate set of the same detection means corresponding to the set of R and 43 is provided separately.With such a configuration, it is possible to prevent the accuracy of V ₁ / V ₂ from deteriorating due to the saturation of the receiving amplifier. the circuit configuration of the central control circuit 5 'in are those equivalent to the configuration of the central control circuit 5 of FIG. 1. that is, when the second amplifier 3 "If saturated, the ratio V ₁ / V ₂ by its output in, As an erroneous value, as a countermeasure, when the signal is saturated, the output of the first amplifier 3 'having a low gain stage is output. Toggles Te, it is possible to wide the determination of the dynamic range by a configuration for determining the ratio V ₁ / V _2.

(Effect)

As described above, in the present invention, even if there is an ultrasonic oscillator having the same or approximate center frequency as the center frequency transmitted by itself, it is detected and changed to a different center frequency for transmission. As a result, there is no malfunction due to interference, and the distance to the target can be measured and displayed at high speed and accurately.

[Brief description of the drawings]

FIG. 1 is a block diagram schematically showing an ultrasonic distance measuring apparatus according to the present invention. FIG. 2 is a diagram showing a pulse waveform used in the present invention. FIG. 3 is a diagram showing a routine of a program used in the present invention. FIG. 4 is a diagram showing another specific example of the present invention. DESCRIPTION OF SYMBOLS 1 ... Ultrasonic vibrator, 2 ... Analog switch, 3 ... Amplifier, 4 ... Reception pulse generation means, 5 ... Central control circuit, 6 ... Display means, 7, 9 ... Peak hold circuit, 8 ... band-pass filter 42 first peak detecting means 43 second peak detecting means 20 transmitting / receiving means 30 distance measuring means and excitation pulse generating means 40 comparing / determining means 41 …… Comparative judgment circuit, 60 …… Display means control means.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takeo Tsuzuki 1-1-1, Showa-cho, Kariya-shi, Aichi Japan Inside Denso Co., Ltd. (56) References JP-A-4-175682 (JP, A) JP-A-2-296174 (JP, A) JP-A-55-112692 (JP, A) JP-A-63-128279 (JP, A A) JP-A-1-152382 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01S 3/80-3/86 G01S 5/18-5/30 G01S 7/52- 7/64 G01S 15/00-15/96

Claims (2)

(57) [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 back from a target, and said ultrasonic pulse transmitting / receiving means. Distance measuring means for measuring the distance to the target based on the information of pulse transmission / reception, means for displaying the measured distance, the maximum value of the amplitude of the reception wave that is not band-pass filtered and the amplitude of the reception wave that is band-filtered Comparing and judging means for judging from the maximum value whether or not the received pulse signal wave is a reflected wave by its own transmission, and displaying the distance measured by the distance measuring means based on the result of the judging means. An ultrasonic distance measuring device comprising a control means for determining whether or not to display an image. 2. An ultrasonic pulse transmitting / receiving means for transmitting an ultrasonic pulse signal having a predetermined center frequency and receiving the ultrasonic pulse signal reflected from a target and returned,
Distance measuring means for measuring a distance to a target based on information on transmission and reception of the pulse in the ultrasonic pulse transmitting and receiving means, means for displaying the measured distance, and at least the predetermined signal for inputting a received ultrasonic pulse signal First peak detecting means comprising a bandpass filter having a center frequency of the following, and a peak hold circuit for storing the peak value of the pulse signal passed through the bandpass filter, and the pulse signal of the pulse signal directly without passing through the bandpass filter. A second peak detecting means comprising a peak hold circuit for storing a peak value;
Comparing and judging means for comparing the outputs from the peak detecting means,
If the comparison value by the comparison determination means is equal to or greater than a predetermined value, the received pulse signal is determined to have been transmitted by itself, and the result measured by the distance measurement means is displayed on the display means. When the comparison value is equal to or less than a predetermined value, the reception pulse signal is determined not to have been transmitted by itself, and control means for controlling so that the measurement result is not displayed on the display means. An ultrasonic ranging device.