JPH1082856A - Distance measuring equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the distance measuring accuracy without being influenced by dispersion or the like of the levels of transmitted-received wave by detecting the respective waveform peaks of transmitted direct wave and received wave, making the peak of the direct wave the transmit time while making the peak of the received wave the receive time, and measuring the distance on the basis of time difference between both time. SOLUTION: In this distance measuring device, wave motion is transmitted in a pulse state directing in a prescribed detecting direction by a transmitting device 5, the wave motion reflected by a subject 6 is received by a receiving device 7 to convert it into an electric signal, and the distance to the subject 6 is measured on the basis of time difference between the transmitted wave and received wave. In this case, each waveform peak of transmitted direct wave and received wave is detected by a peak detecting circuit 11, and the peak of the direct wave is made transmit time, while the peak of the received wave is made receive time to measure the distance on the basis of time difference between both time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention measures the distance to an obstacle (object to be inspected) when parking or other necessity, such as a corner sensor mounted on the front side or rear side of a vehicle, or a back sonar, for example. To such a distance measuring device.

[0002]

2. Description of the Related Art Conventionally, as a distance measuring apparatus of the above-described example, there is an apparatus having a circuit configuration as shown in FIG. That is,
A transmission trigger is output from the system control unit 51 to a transmission unit 52 (a circuit that forms a transmission waveform). The transmission unit 52 drives a transmission unit in the transducer 53 to generate a wave (eg, an ultrasonic wave). , And the wave reflected by the test object 55 is received by the wave receiving unit 56 in the transducer 53, and the wave received is converted into an electric signal, and then converted into an electric signal. Amplification is performed at 57, and a detection process is performed to extract the envelope of the amplified reception signal at a detector 58, and the reception level is set to a threshold value at a comparator 59 whose threshold value is set in advance. When the stop trigger is reached, a stop trigger is output to the distance counting unit 60 (so-called counter), and the time between the start trigger output to the distance counting unit 60 at the same time as the output of the previous transmission trigger and the stop trigger (wave transmission and Receiving waves Vehicle 61 (FIG. 6 based on the time difference), it is a device for measuring the distance between the see FIG. 7) and the test object 55.

However, the transmission level fluctuates due to the influence of the ambient temperature on the protection member such as rubber for protecting the oscillator of the transducer 53 described above.
In the case where the vehicle 61 is parked while moving backward as shown in FIG. 5, even if the distance between the vehicle 61 and the test objects 55A and 55B is the same, the form of the test objects 55A and 55B (the wall surface 55A as an example in the drawing). And the illumination light pole 55B), the reflection intensity varies, and the levels of the waves (received waves) reflected by the two test objects 55A and 55B are different. That is, since both the transmission level and the reception level vary, there has been a problem that it is not possible to secure high-accuracy distance measurement accuracy due to variations in the level of each of these waves.

In particular, when an ultrasonic wave is used for the above-mentioned wave, the accuracy of the distance measurement is further deteriorated due to the above-described variation because the fluctuation of the transmission wave is large and the distance measurement range is short in addition to the influence of reverberation. There was a problem to do.

On the other hand, as described in Japanese Patent Application Laid-Open No. 5-100026, in a distance measuring apparatus for laser distance measurement, a plurality of threshold values are set, and a received signal is compared with the plurality of threshold values. Determine the timing near the peak value of the received wave,
There is also a configuration in which the propagation time is determined based on the transmission timing and the reception timing, but a complete peak cannot be detected, and the circuit configuration is complicated, and in addition, it is disclosed in the publication. However, when the ultrasonic wave is used as the wave, there is a problem that the adverse effect on the transmitting side cannot be compensated.

[0006]

SUMMARY OF THE INVENTION The invention according to claim 1 of the present invention detects peaks of respective waveforms of a transmitted direct wave and a received wave, and detects the peak of the direct wave at the transmission time and the received wave. By measuring the distance based on the time difference between these two times with the peak as the receiving time, the distance measuring device can improve the distance measuring accuracy without being affected by the variation in the level of the transmitting and receiving waves. For the purpose of providing.

According to a second aspect of the present invention, in addition to the object of the first aspect of the present invention, a differential type peak detection circuit is used for peak detection, so that a change rate can be detected by a differential processing, and It is an object of the present invention to provide a distance measurement value capable of performing accurate peak detection with a simple circuit configuration.

According to a third aspect of the present invention, in addition to the object of the first or second aspect of the present invention, the use of ultrasonic waves as waves makes it possible to reduce the effects of reverberation and fluctuations in transmission and reception levels. An object of the present invention is to provide a distance measuring device that can achieve accurate distance measurement even with a large ultrasonic wave and is suitable for the ultrasonic wave.

[0009]

According to the first aspect of the present invention, a wave is transmitted in a pulsed manner in a predetermined detection direction by a transmitting device, and the wave reflected by an object to be detected is received. A distance measuring device that receives a wave by a wave device, converts the signal into an electric signal, and measures a distance to a test object based on a time difference between the transmitted wave and the received wave. It is a distance measuring device that detects a peak of each waveform with a peak detection circuit, sets a peak of a direct wave as a transmission time and a peak of a reception as a reception time, and measures a distance based on a time difference between the two. I do.

According to a second aspect of the present invention, in addition to the object of the first aspect, the present invention is a distance measuring apparatus in which the peak detection circuit is set as a differential peak detection circuit. .

According to a third aspect of the present invention, in addition to the object of the first or second aspect, the present invention is a distance measuring apparatus in which the wave is set to an ultrasonic wave.

[0012]

According to the first aspect of the present invention, the above-described wave transmitting device transmits a wave in a pulse shape in a predetermined detection direction, and the above-described wave receiving device transmits the object to be measured. The peak detection circuit detects the peak of the waveform of the transmitted direct wave and the peak of the waveform of the received wave, respectively, and detects the peak of the direct wave detected by the peak detection circuit. Since the peak is the transmission time and the reception peak is the reception time, distance measurement is performed based on the time difference between these two times, so that even if there is a variation in the level of the transmission and reception, these variations are not affected at all. Thus, there is an effect that the ranging accuracy can be improved.

According to the invention described in claim 2 of the present invention,
In addition to the effect of the first aspect of the present invention, since the peak detection circuit is set as a differential type peak detection circuit, the rate of change can be detected by differential processing. There is an effect that peak detection can be performed.

According to the third aspect of the present invention,
Since the above-mentioned wave is set to the ultrasonic wave in addition to the effect of the invention of claim 1 or 2, the above-described peak detection is performed even for an ultrasonic wave which is particularly susceptible to reverberation or fluctuations in the transmission / reception level. By this means, accurate ranging can be achieved, and there is an effect that it is suitable for ultrasonic waves having a short ranging range.

That is, since the peak of each waveform is detected by the peak detecting means, the detection of the received signal itself can be easily and accurately performed even during reverberation. However, in the method of performing detection by simply setting a threshold or the like, it is particularly difficult to detect a received signal during reverberation.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the drawings. The drawing shows a distance measuring device. In FIG. 1, the distance measuring device 1 is connected to a transmitting unit 5 of an ultrasonic transducer 4 via a transmitting unit 3 which forms a transmitting waveform at the next stage of the system control unit 2. ing.

The above-mentioned wave transmitting unit 5 is a wave transmitting device for transmitting a wave, that is, an ultrasonic wave in a pulse direction toward the object 6 (predetermined detection direction). The wave is received by the wave receiving unit 7 as a wave receiving device, and is converted into an electric signal. In this embodiment, the above-mentioned wave transmitting unit 5 and wave receiving unit 7 are integrated, but are separately shown in FIG. 1 for convenience of explanation.

An amplifier 8, a detector 9, an LPF (low-pass filter) 10, a differentiator 11 as a differential peak detection circuit, a comparator 12, and a first falling counter are provided at a stage subsequent to the above-described wave receiving unit 7. 13, the second falling counter 14 is connected in this order. Also, the above-mentioned system control unit 2 line 1
Each of the falling counters 13 and 14 is connected to the first falling counter 1 via a start trigger line 17, and the falling counters 13 and 14 are connected to the first falling counter 1 via a start trigger line 17. The second falling counter 14 is also connected to 18 via a stop trigger line 19.

Here, the above-mentioned amplifier 8 amplifies the received signal after being converted into an electric signal, and the above-mentioned detector 9 executes a detection process such as extracting the envelope of the amplified received signal. The above-described LPE 10 removes noise from the detection wave type, and the above-described differentiator 11 differentiates the LPF output to obtain a peak P1 of the waveform of the transmitted direct wave a (see FIG. 2) (see a point x1 at which zero crosses in FIG. 2). ) And the peak P2 of the waveform of the received wave b (FIG. 2).
At point x2 at which zero crossing occurs).
The comparator 12 forms a comparator output as shown in FIG. 2, the first falling counter 13 starts counting at the first falling d1 of the output of the comparator 12, and counting at the second falling d2. , And the second falling counter 14 outputs the comparator 12
The counting is started at the second falling d2, and the counting is finished at the third falling d3.

Further, the peak P1 (see point x1) of the direct wave a is set as a transmission time t1, and the transmission time t1
In FIG. 1, the first falling counter 13 is a distance counter 18
, A peak P2 of the received wave b (see point x2) is set as a received time t2, and the received time t
2, the second falling counter 14 is a distance counter 18
The distance counter 18 executes distance measurement based on the time difference Δt between both times t1 and t2. That is, the above-described distance counter 18 converts the time difference Δt and the propagation speed of the wave into distance information.

The illustrated embodiment is constructed as described above, and the operation will be described below. Upon receiving a transmission trigger from the system control unit 2, the transmission unit 3 forms a transmission waveform, and the transmission unit 5
Transmits an ultrasonic wave in the direction of the test object 6 in a pulse form. The ultrasonic wave reflected by the test object 6 is received by the wave receiving unit 7 and converted into an electric signal. The differentiator 11 as a peak detection circuit performs LP detection after amplification, detection, and noise removal.
By detecting the rate of change by differentiating the F output, the peak P1 of the waveform of the direct transmission wave a shown in FIG. 2 (see point x1)
And the peak P2 (see point x2) of the waveform of the received wave b, respectively, and the peak P1 of the direct wave a detected by the differentiator 11 is transmitted at the transmission time t1 and the peak P2 of the received wave b.
Is the reception time, the distance counter 18
The time difference (Δt = t2−t1) is counted by a start trigger (applied at time t1) and a stop trigger (applied at time t2) from 3 and 14, and the product of the time difference Δt and the propagation speed of the ultrasonic wave is counted. To convert to distance information.

As described above, the peaks P1 and P2 of the two waves a and b are obtained.
Is detected and the distance is measured based on the time difference Δt. Therefore, even if there is a variation in the level of the transmitted and received waves, the variation is not affected at all and there is an effect that the ranging accuracy can be improved. . Further, since the differential type 11 is used as the differential type peak detection circuit, the rate of change can be detected by the differential processing, and there is an effect that accurate peak detection can be performed with a simple circuit configuration.

Furthermore, even if an ultrasonic wave which is easily affected by reverberation or fluctuations in the level of transmitted / received waves is used as a wave, accurate distance measurement can be achieved by the peak detecting means as described above. There is an effect that is suitable for sound waves.
In addition, the received wave can be extracted from the reverberation area c of the direct wave a shown in FIG. 2, and the circuit configuration of the entire apparatus is simple and inexpensive. Further, since the transmission time t1 and the reception time t2 can be detected by the single differentiator 11, there is an effect that the system is simplified.

FIG. 3 shows a distance measuring device 1 having the above-described configuration,
0 is arranged at a plurality of locations on the front side and the rear side to secure the sensor detection areas A to F shown in FIG. 3. And a rear display 22 is attached to a pillar member such as a center pillar so that the driver can see the distance when the vehicle is moving backward, and the rear display 22 performs distance display.

The display mode of each of the indicators 21 and 22 is set to one of the following six types. Display Mode 1 The front display 21 displays the shortest distance detected in all the areas A to F and its position (position indicating which area), and the rear display 22 displays the areas D, E, and F. Displays the shortest distance of the longest. With this setting, it is possible to grasp the approaching situation in all areas while the driver is basically facing the front, and when checking the rear side, the driver is facing the rear. The display 22 can automatically visually confirm the rear area.

Display Mode 2 The front display 21 displays the shortest distance detected in the areas A, C, D, and F and its position.
For 2, the distance of the area E is displayed. With this setting, the areas A, C, D, and F also have a detection area in the horizontal direction. Therefore, when the vehicle is parked in parallel, the horizontal distance is displayed on the front display 21 and the rear display is displayed. The distance in the backward direction is displayed on the container 22, and the positional relationship of the vehicle 20 can be easily grasped.

Display Mode 3 The front display 21 displays the shortest distance detected in the areas A, B, and C and its position, and the rear display 22 detects the distance D in the areas D, E, and F. Shows the shortest distance you have. With this setting, the front display 21 displays the distance on the front side, and the rear display 22 displays the distance on the rear side. Even if there is, it is easy to understand intuitively by visual observation.

Display Mode 4 For the front display 21, a mode for switching the area for displaying the distance at regular intervals is added to each of the previous display modes 1 to 3, and the rear display 22 is similarly displayed in the previous display mode. A mode for switching the area in which the distance is displayed at regular intervals is added to each of 1 to 3. With this setting, not only the sign distance but also the distances of all the areas A to F can be confirmed.

Display Mode 5 For the front display 21, an area selected by the driver from all of the front and rear areas A to F (for example, a touch switch is previously installed in the instrument panel, and this switch is included in each of the display modes 1 to 3). A mode for displaying the distance of the selected area is added, and the rear display 22 is set in the same manner as in the display modes 1 to 3. With this setting, for example, in the case where the vehicle 20 is moved backward while being brought close to a wall, it is possible to effectively cope with the case where the information is not information that the driver wants to know.

Display mode 6 The LED for displaying the position of the front display 21 is set so that the LED is turned on, and the LED of the shortest distance area is turned on and off, and only the lights detected for other areas are turned on. I do.

With this setting, not only the shortest distance but also other detected areas can be recognized, so that it is possible to prevent the vehicle 20 from hitting an object in an area that is not the shortest but has a short distance. An example of the distance display in each of the display modes 1 to 6 is as shown in FIG.

On the other hand, there is provided an alarm means for generating an alarm sound (buzzer sound, electronic sound, etc.) depending on the distance measured by the above-mentioned distance measuring device 1, large, medium, and small (shortest distance) to detect an obstacle. When the distance is large in the distance, a long intermittent sound is emitted,
It may be configured such that when the distance is short, an intermittent sound is emitted at short intervals, and when the distance is short, a continuous sound in which intermittent is prohibited is emitted.

As still another embodiment, ON and O for manual operation for operating and stopping the operation of the distance measuring device 1 shown in FIG.
In addition to the FF switch, the system has a mode for automatically turning on and off the device 1 to reduce the frequency of forgetting to turn on the ON / OFF switch for manual operation and the frequency of false alarms. ON, OF for
A configuration may be adopted to prevent the life of the transducer 4 from being shortened due to forgetting to turn off the F switch.

Here, the conditions for automatically operating (ON) the above-mentioned system are when the engine is started or when the reverse gear is selected. In general, when the engine is started, a sensor operation is often required when the vehicle 20 is out of the garage or when the vehicle is moved from parking on the road. Also, when the reverse gear is selected, it is often necessary to operate the system such as entering the garage and changing directions, so the system is turned on. The system is automatically operated by the OR logic between the start of the engine and the selection of the reverse gear. It is effective when activated.

On the other hand, the above system is automatically stopped (O
The condition for FF) is after a certain time (for example, about 1 to 10 minutes) has elapsed after the system is turned on. In other words, generally, the time required for garage storage is about 3 minutes at the longest, and it is considered that there is almost no case where the operation needs to be continuously performed for 10 minutes or more. Further, even if the power is automatically turned off, when the vehicle is put in the garage after driving, the vehicle is normally parked from the back, so that the system is turned on, and no problem occurs. On the other hand, there is a case where the vehicle is parked from the front. In this case, however, there is no problem when the system does not operate because the parking space has ample space or the vehicle is almost straight into the parking space. As described above, by controlling the ON / OFF of the system, the system is automatically operated when necessary, and the power OFF control can be performed when the system is not needed, such as during traveling.

In the correspondence between the configuration of the present invention and the above-described embodiment, the wave of the present invention corresponds to the ultrasonic wave of the embodiment, and similarly, the predetermined detection direction corresponds to the direction of the test object 6. The wave transmitting device corresponds to the wave transmitting unit 5, and the wave receiving device is
The peak detection circuit and the differential peak detection circuit corresponding to the wave receiving unit 7 correspond to the differentiator 11, but the present invention is not limited to the configuration of the above-described embodiment. For example, another wave such as an electromagnetic wave or a laser may be used instead of the ultrasonic wave.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a distance measuring device according to the present invention.

FIG. 2 is a time chart showing the operation of the device.

FIG. 3 is a schematic plan view showing a mounting position of a sensor and a display.

FIG. 4 is an explanatory diagram showing an example of distance display.

FIG. 5 is a block diagram showing a conventional distance measuring device.

FIG. 6 is an explanatory diagram illustrating an example of a test object.

FIG. 7 is an explanatory view showing another example of the test object.

[Explanation of symbols]

 5: transmitting section 6: object to be tested 7: receiving section 11: differentiator

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Satoshi Morioka 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Co., Ltd.

Claims (3)

[Claims] 1. A wave transmitting device in which a wave is directed in a predetermined detection direction in a pulse form by a wave transmitting device, and the wave reflected by a test object is received by a wave receiving device, converted into an electric signal, and transmitted. A distance measuring device for measuring a distance to a test object based on a time difference between a wave and a received wave, wherein a peak detection circuit detects a peak of each of the transmitted direct wave and the received wave by a peak detection circuit, and A distance measuring device that measures a distance based on a time difference between the peak of the transmission time and the peak of the reception as the transmission time and the reception time. 2. The distance measuring apparatus according to claim 1, wherein said peak detecting circuit is set as a differential peak detecting circuit. 3. The distance measuring apparatus according to claim 1, wherein the wave is set to an ultrasonic wave.