JPH08278368A - Obstacle detection device - Google Patents

Abstract

PURPOSE: To prevent wrong obstacle detection caused by road surface reflection. CONSTITUTION: Ultrasonic wave is transmitted from a transducer 1, and the wave reflected on an obstacle is received by the transducer 1. The received signal is amplified according to reception time by an amplifier circuit 4. At this time, amplitude factor correction part 11 reduces amplification factor of the signal corresponding to road surface reflection wave. The distance from a vehicle to a point the road surface reflection wave is generated is calculated in advance, with road surface height at an installation place of the transducer 1, inclination angle of a central line of the ultrasonic wave against horizontal plane, and beam width of the ultrasonic wave as parameters, and stored into a storage part 14. The stored data is, when vehicle height is changed from reference height by a vehicle height adjustment device, compensated according to the change amount by a compensation part 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an obstacle detecting device mounted on a vehicle, and more particularly to an obstacle detecting device for transmitting radar waves such as ultrasonic waves.

[0002]

2. Description of the Related Art Conventionally, as an obstacle detecting device for a vehicle, a radar wave such as an ultrasonic wave is transmitted from a transmitting portion and an obstacle is hit, as disclosed in Japanese Patent Laid-Open No. 5-87911. It is known that the receiving unit receives the reflected wave that is reflected by the receiver and measures the distance between the vehicle and the obstacle and the relative speed from the difference between the receiving time and the transmitting time. . Further, in the above-mentioned publication, in consideration of the fact that the signal of the reflected wave becomes weaker as the distance to the obstacle increases, the reception time of the reflected wave is delayed when the signal of the reflected wave is amplified by the amplifier circuit. By increasing the amplification factor of the signal (that is, the distance to the obstacle is longer), the obstacle can be recognized as a reflected wave signal having a predetermined magnitude or more regardless of the distance to the obstacle. Is disclosed.

[0003]

By the way, in the above-mentioned conventional obstacle detecting device, the radar wave transmitted from the transmitting portion is reflected on the road surface and received by the receiving portion, and the signal of the road surface reflected wave is amplified by the amplifier circuit. There is a problem that it is erroneously recognized as an obstacle by being amplified.

The present invention has been made in view of the above points, and an object of the present invention is to properly remove a signal corresponding to a road surface reflected wave from a signal of a reflected wave so that an error caused by road surface reflection can be prevented. Another object of the present invention is to provide an obstacle detection device capable of preventing the obstacle detection.

[0005]

In order to achieve the above object, the invention according to claim 1 transmits a radar wave from a transmitter and receives a reflected wave reflected by an obstacle at a receiver. In the obstacle detection device for measuring at least the distance between the own vehicle and the obstacle from the difference between the reception time and the transmission time, the radar surface emitted from the transmission unit hits the road surface and is reflected on the road surface. A configuration is provided that includes identification means for identifying the reflected wave and signal processing means for removing a signal corresponding to the road surface reflected wave identified by the identification means from the signals of the reflected wave received by the receiving section.

According to a second aspect of the present invention, in the obstacle detection device according to the first aspect, a specific mode of identifying the road surface reflected wave by the identification means, which is one of the constituent elements, is shown. That is, the identification means is a point where a road surface reflected wave calculated in advance using as parameters the road surface height at the location where the transmitter is installed, the inclination angle of the center line of the radar wave transmitted from the transmitter with respect to the horizontal plane, and the beam width of the radar wave. The distance from the host vehicle is stored, and the reflected wave corresponding to the distance is identified as the road surface reflected wave.

According to a third aspect of the present invention, in the obstacle detection device according to the first or second aspect, the signal processing means, which is one of the components, amplifies the reflected wave signal according to the reception time. And an amplification factor correction unit that reduces the amplification factor of the signal corresponding to the road surface reflected wave when the amplification circuit performs amplification.

The invention according to claim 4 shows a countermeasure in the obstacle detecting device according to claim 2 when the vehicle height is changed from a reference height by a vehicle height adjusting device mounted on the host vehicle. That is, the identifying means is configured to have a correction unit that corrects the distance from the vehicle at the point where the road surface reflected wave that is stored in advance is stored according to the amount of change in the vehicle height.

[0009]

With the above construction, in the invention according to claim 1, the road surface reflected wave is identified by the identifying means, and the signal corresponding to the road surface reflected wave identified by the identifying means is selected from the signals of the reflected wave received by the receiving section. The signal to be processed is removed by the signal processing means, which prevents erroneous obstacle detection due to road surface reflection.

According to the second aspect of the present invention, the identifying means stores in advance the distance from the vehicle at the point where the road surface reflected wave occurs, and identifies the reflected wave corresponding to the distance as the road surface reflected wave. Can be easily and quickly identified.

According to the third aspect of the present invention, when the amplification circuit of the signal processing means amplifies the signal of the reflected wave in accordance with the reception time, the amplification factor correcting section changes the amplification factor of the signal corresponding to the road surface reflected wave. Since the signal corresponding to the road surface reflected wave is removed by making it smaller, the obstacle can be recognized as a reflected wave signal of a predetermined size or more regardless of the distance to the obstacle, and the road surface reflected wave is generated. Even if there is an obstacle near the point, the signal of the reflected wave from the obstacle is recognized as a large signal even if it is not greatly amplified by the amplifier circuit,
The detection of the actual obstacle is not impaired.

In the invention according to claim 4, when the vehicle height is changed from the reference height by the vehicle height adjusting device mounted on the vehicle, the road surface reflection stored in advance in the discriminating means according to the change amount. Since the distance from the own vehicle at the point where the wave is generated is corrected by the correction unit, the road surface reflected wave can be properly identified regardless of the change in the vehicle height or the road surface height at the place where the transmission unit is installed.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a block configuration of an obstacle detecting device A according to an embodiment of the present invention. In this embodiment, the obstacle detection device A is installed in a vehicle equipped with a vehicle height adjustment device (not shown).

In FIG. 1, reference numeral 1 denotes an ultrasonic transducer mounted on the front portion of a vehicle body of a vehicle. The transducer 1 receives a transmission signal from a sensor drive circuit 2 and has a frequency of several tens of kHz as a radar wave. The transmission unit that transmits a sound wave and the reception unit that receives a reflected wave reflected by an ultrasonic wave hitting an obstacle are integrated. A reception signal (that is, a reflected wave signal) received by the transducer 1 is input to the distance calculation unit 5 via the sensor reception circuit 3 and the amplification circuit 4. The distance calculator 5 calculates at least the distance between the host vehicle and the obstacle from the difference between the signal reception time and the signal transmission time (specifically, the command time of the transmission command to the sensor drive circuit 2). .

When the ultrasonic transducer 1 is attached to the vehicle body, measures against running wind and waterproof as shown in FIGS. 2 and 3 are taken. That is, the ultrasonic horn 21 is attached to the ultrasonic transducer 1, and the ultrasonic horn 2 is attached.
Reference numeral 1 has a reflection wall surface 21a which is changed by the ultrasonic waves emitted from the ultrasonic transducer 1 to change its direction to a right angle, and an opening 21b through which the ultrasonic waves from the reflection wall surface 21a pass. A plurality of vertical fins 22 are provided in the opening 21b.
A louver 22 having a, 22a, ... Is attached.
The louver 22 is for reducing the pressure of water that enters the ultrasonic horn 21, but the width of each vertical fin 22a is less than or equal to the wavelength of the ultrasonic wave (6
mm). And the ultrasonic horn 21
The ultrasonic transducer 1 is installed in a position where the influence of traveling wind is small with the opening 21b of the ultrasonic transducer 1 facing the direction in which an obstacle is detected (for example, the front of the vehicle). We try to reduce the impact as much as possible. Further, a thin film 23 such as a polypropylene sheet or a polyester sheet is attached to the surface of the ultrasonic transducer 1, that is, the vibrating surface so as to prevent water from adhering to the vibrating surface and prevent high water pressure from being directly applied. Has become.

The sensor drive circuit 2 outputs a transmission signal to the ultrasonic transducer 1 based on a transmission command from the distance calculator 5. As shown in FIG. 4, the sensor receiving circuit 3 includes a band pass filter 6 that passes only a signal in a predetermined frequency band of the received signal,
The Doppler effect is provided with a frequency detection unit 7 that detects the frequency of the received signal and sets the band of the filter 6 so that the signal of the detected frequency passes through the band pass filter 6, Is removed from the received signal to enhance the sensitivity and selectivity of the receiving circuit 3.

The amplification circuit 4 amplifies the reception signal input through the sensor reception circuit 3 by a predetermined amplification factor, and the amplification factor is indicated by the solid line ST in FIG.
According to the C (sensitivity time control) curve, it is preset such that the larger the reception time is (the later), that is, the larger the distance to the obstacle is, the larger the correction time is corrected based on the command from the amplification factor correction unit 11. It has become so. The amplification factor correction unit 11 outputs a command signal to the amplification circuit 4 so as to reduce the amplification factor of the signal corresponding to the road surface reflected wave identified by the identification unit 13 (state shown by the broken line in FIG. 5). Therefore, the amplification circuit 4 and the amplification factor correction unit 11 constitute a signal processing means 12 for removing a signal corresponding to a road surface reflected wave.

The identifying means 13 is a distance from the vehicle at the point where the road surface reflected wave occurs (hereinafter referred to as road surface reflection distance).
And a storage unit 14 that calculates and stores
The correction unit 15 corrects the road surface reflection distance stored in FIG. The correction unit 15 receives a signal from a vehicle height sensor 16 that detects a vehicle height and a signal from a vehicle speed sensor 17 that detects a vehicle speed, and corrects the road surface reflection distance according to the vehicle height and the vehicle speed. Has become.

Here, a method for calculating the road surface reflection distance and its strength will be described. This calculation method is performed by the following procedures (1) to (3).

A beam pattern (intensity level) of ultrasonic waves transmitted from the ultrasonic transducer 1 is set.
This beam pattern is assumed to have a Gaussian distribution (normal distribution). The Gaussian distribution formula is as follows.

[0022]

[Equation 1] In this formula, the pulse width is 25.3% of -1 to 1
Since it is (0.47), it is adjusted to the full width at half maximum of the actual ultrasonic wave. That is, if the beam width is 10 °, 0.47 is 1
Convert the angle so that it becomes 0 °.

The angle θ (= tan ⁻ ) between the ultrasonic beam and the road surface at a position separated from the vehicle (specifically, the installation location of the ultrasonic transducer 1) by a predetermined distance L from the road surface height H of the installation location of the ultrasonic transducer 1. ¹ (H / L)) is calculated for each distance.

The intensity of the ultrasonic beam emitted for each distance is calculated from and.

What percentage of the ultrasonic beam hits the road surface
Calculates whether the ultrasonic wave returns to the ultrasonic transducer 1. In this case, the influence of the angle θ and the influence of the distance L are considered respectively. The effect of the angle theta, component fleeing regularly reflected on the road surface is smaller as theta is large, and because the retro-reflected high as component theta greater come back to the transducer 1 to the road surface, reflected sin ² theta Assume that the intensities are proportional. Regarding the influence of the distance L, if the ultrasonic waves reflected and returned to the road surface spread like a sphere, the surface area of the sphere is proportional to the square of the distance, and therefore the reflection intensity is inversely proportional to the square of the distance. Assume weakening.

By calculating the above items, the relative road surface reflection intensity at each distance L is calculated. FIG. 6 shows a calculation example (correlation between the distance L and the road surface reflection intensity) when the road surface height H at the installation location of the ultrasonic transducer 1 is 0.4 m and the beam width is 10 °. However, in FIG. 6, the downward inclination angle α of the transmission center line of the ultrasonic transducer 1 with respect to the horizontal plane is 0 °, 0.5 °, 1.0 °, 1.5 °, respectively.
The case of 2.0 ° is described. In the case of this calculation example, the road surface reflection distance is in the range of 1.5 to 5.0 m. The storage unit 14 stores a distance within a predetermined range as in this calculation example as a road surface reflection distance.

FIG. 7 shows a control flow for amplifying the received signal by the amplifier circuit 4. In this figure, after the start, first, in step S1,
The distance from the host vehicle at the point where the road surface reflected wave is stored in advance, that is, the road surface reflection distance B is read out, and the current vehicle height is determined as the reference vehicle height based on the vehicle height signal from the vehicle height sensor 16 in step S2. It is judged whether or not there is, and the judgment is YE.
When the reference vehicle height is S, the process immediately proceeds to step S4, while when the determination is NO, the road surface reflection distance B is corrected according to the difference between the current vehicle height and the reference vehicle height.
This vehicle height correction is performed because the road surface reflection distance B is calculated based on the reference vehicle height, and when the current vehicle height is higher than the reference vehicle height, the current road surface reflection distance B is increased. When the vehicle height is lower than the reference vehicle height, the road surface reflection distance B is corrected so as to decrease. In step S4, the road surface reflection distance B is corrected based on the vehicle speed signal from the vehicle speed sensor 17. This vehicle speed correction is for removing the influence of the Doppler effect due to the movement of the own vehicle,
The ultrasonic transducer 1 is transmitted in the front direction of the vehicle, and when traveling forward, the higher the vehicle speed, the lower the road reflection distance B is corrected. The execution of steps S1 to S4 is performed by the correction unit 15 of the identification means 13.

Subsequently, in step S5, the STC curve shown by the solid line in FIG. 5 is corrected so as to reduce the amplification factor in the band corresponding to the road surface reflection distance B after the vehicle height correction and the vehicle speed correction described above. The curve shown by the broken line is corrected. After a while
In step S6, the received signal is amplified according to the modified STC curve, and the process returns.

Thus, the obstacle detection device A of this embodiment
In, when the signal of the reflected wave received by the ultrasonic transducer 1 is amplified by the amplifier circuit 4 according to the reception time, that is, the distance to the obstacle, according to the STC curve,
By correcting the STC curve so as to reduce the amplification factor in the band corresponding to the road surface reflection distance B at the point where the road surface reflected wave is generated, that is, the signal corresponding to the road surface reflected wave in the received signal. Therefore, it is possible to prevent erroneous obstacle detection due to road surface reflection.
Moreover, even if an obstacle is actually present near the point where the road surface reflected wave is generated, the signal of the reflected wave from the obstacle is recognized as a large signal even if it is not greatly amplified by the amplifier circuit. Detection is not compromised. FIG.
FIG. 8A is a waveform diagram of a received signal in the case of the conventional example amplified according to the solid line STC curve, and FIG. 8B is a broken line STC.
It is a wave form diagram of the received signal in the case of the example of this invention amplified according to the C curve. As can be seen from FIG. 8, in the case of the present invention example, the signal pulse m1 of the obstacle close to the own vehicle and the signal pulse m3 of the obstacle far from the own vehicle both become large as in the case of the conventional example, and the road surface reflection The signal pulse m2 of the wave is kept small.

The road surface reflection distance B is calculated in advance using as parameters the road surface height H at the installation location of the ultrasonic transducer 1, the inclination angle α of the transmission center line of the ultrasonic transducer 1 with respect to the horizontal plane, and the ultrasonic beam width. Since it is stored in the storage unit 14 and is not calculated at the time of detecting an obstacle, the obstacle detection will not be hindered. Further, since the vehicle height correction and the vehicle speed correction are performed on the road surface reflection distance B stored in the storage unit 14, the road surface reflected wave signal can be properly identified.
The removal can be performed accurately.

(Modification) FIG. 9 shows a modification of the sensor receiving circuit 3. In the case of this modification, the sensor receiving circuit 3 allows the band-pass filter 31 to pass only a signal of a predetermined frequency band among the received signals. And the band pass filter 31
Is provided so as to receive the vehicle speed signal from the vehicle speed sensor 17, estimate the frequency of the received signal by itself from the vehicle speed, and pass the signal of the estimated frequency. Also in the case of this modification, the sensitivity and selectivity of the receiving circuit 3 can be increased by removing the influence of the Doppler effect due to the movement of the host vehicle or the obstacle from the received signal.

FIG. 10 shows another modification of the sensor receiving circuit 3. In this modification, the sensor receiving circuit 3 is adapted to obtain high selectivity and high sensitivity by heterodyne detection. That is, the sensor receiving circuit 3 determines that the high frequency signal f2
A local oscillator 3 for generating (for example, f2 = 505 kHz)
2, a mixer 33 for mixing the received signal f1 (for example f1 = 50 KHz) and the high frequency signal f2 to convert the received signal f1 into a high frequency signal f1 '(for example f1' = 455 KHz), and a mixer 33 near the high frequency received signal f1 ' And a ceramics filter 34 that passes only the frequency signal. In the case of this modification, since the received signal f1 is converted into the high frequency received signal f1 ', the ceramic filter 34 for a commercially available AM radio can be used as a band pass filter, and the cost can be reduced. Have.

11 to 15 show first to fourth modifications for waterproofing the ultrasonic transducer 1.

That is, in the case of the first modification shown in FIG. 11, a cylindrical horn 41 is attached to the surface side of the ultrasonic transducer 1, and a rotary blade 42 having a plurality of radial fins at the tip of the horn 41. Is rotatably attached.

In the case of the second modified example shown in FIG. 12, by mounting a cannonball-shaped cover 43 made of porous sponge on the surface side of the ultrasonic transducer 1, the traveling wind pressure applied to the surface of the ultrasonic transducer 1 can be controlled. Weaken,
The generation of noise such as wind noise that is generated when the traveling wind directly hits the surface of the transducer 1 is suppressed.

In the case of the third modified example shown in FIG. 13, a cover frame body 44 formed by weaving a wire or the like into a net-like shape is attached to the surface of the ultrasonic transducer 1.
By attaching a waterproof thin film (not shown) such as a polypropylene sheet or a polyester sheet to the entire cover frame 44, the same effect as in the case of the second modified example is exhibited.

Further, in the case of the fourth modification shown in FIGS. 14 and 15, a cylindrical horn 45 is attached to the surface side of the ultrasonic transducer 1. While the tip of the horn 45 is closed by a waterproof thin film 46, an inlet 47 for taking in air is formed in the horn 45, and a louver 48 for preventing water droplet entry is provided in the inlet 47. As a result, running wind and waterproofing measures are taken against the ultrasonic transducer 1, and the thin film 4 is moved by the running wind.
The pressure applied to 6 is made equal inside and outside the membrane to reduce the burden.

[0038]

As described above, according to the obstacle detecting device of the present invention, since the signal corresponding to the road surface reflected wave can be removed from the signal of the reflected wave received by the receiver, the road surface reflected wave can be removed. It is possible to prevent erroneous obstacle detection due to.

In particular, according to the second aspect of the invention, the road surface height at the location where the transmitter is installed, the inclination angle of the center line of the radar wave emitted from the transmitter with respect to the horizontal plane, and the beam width of the radar wave are used as parameters. The calculated distance from the vehicle at which the road surface reflected wave occurs is stored, and the reflected wave corresponding to the distance is identified as the road surface reflected wave. Therefore, the road surface reflected wave can be easily and quickly identified. It also has the effect that it can be performed.

According to the third aspect of the invention, when the signal of the reflected wave is amplified according to the reception time, the amplification factor of the signal corresponding to the road surface reflected wave is reduced to correspond to the road surface reflected wave. Signal is removed, the obstacle can be recognized as a reflected wave signal of a predetermined magnitude or more regardless of the distance to the obstacle, and even if there is an obstacle near the point where the road surface reflected wave occurs, the obstacle can be recognized. Objects can be detected.

Further, according to the invention of claim 4,
Even if the vehicle height is changed from the reference height by the vehicle height adjusting device, the distance from the own vehicle at the point where the road surface reflected wave stored in advance is corrected according to the change amount,
The road surface reflected wave can be properly identified, and the removal can be accurately performed.

[Brief description of drawings]

FIG. 1 is a block configuration diagram of an obstacle detection device according to an embodiment of the present invention.

FIG. 2 is an exploded perspective view of a structure of an ultrasonic transducer in which running wind and waterproofing measures are taken.

FIG. 3 is a cross-sectional view of the above structure.

FIG. 4 is a block diagram of the vicinity of a sensor receiving circuit.

FIG. 5 is a diagram showing an STC (sensitivity time control) curve.

FIG. 6 is a diagram showing a correlation between distance and road surface reflection intensity.

FIG. 7 is a flowchart of control when amplifying a received signal by an amplifier circuit.

8A and 8B are waveform diagrams of a reception signal amplified according to an STC curve, where FIG. 8A shows the case of the conventional example and FIG. 8B shows the case of the present invention example.

FIG. 9 is a view corresponding to FIG. 4 showing a modification of the sensor receiving circuit.

FIG. 10 is a view corresponding to FIG. 4 and showing another modification of the same.

FIG. 11 is a perspective view showing a first modification for applying a waterproofing measure to an ultrasonic transducer.

FIG. 12 is a perspective view showing a second modification of the same.

FIG. 13 is a perspective view showing a third modification of the same.

FIG. 14 is a perspective view showing a fourth modification of the same.

FIG. 15 is a vertical sectional view of the same.

[Explanation of symbols]

A Obstacle detection device 1 Ultrasonic transducer (reception unit, transmission unit) 4 Amplification circuit 5 Distance calculation unit 11 Amplification factor correction unit 12 Signal processing unit 13 Identification means 14 Storage unit 15 Correction unit

Claims (4)

[Claims] 1. A radar unit transmits a radar wave, and a reception unit receives a reflected wave reflected by an obstacle, and at least the host vehicle and the obstacle are detected from the difference between the reception time and the transmission time. In an obstacle detection device for measuring the distance between, an identification means for identifying a road surface reflected wave in which the radar wave transmitted from the transmission section hits the road surface and is reflected, and a signal of the reflected wave received in the reception section An obstacle detection device, which includes a signal processing means for removing a signal corresponding to the road surface reflected wave identified by the identification means. 2. The road surface reflected wave calculated in advance by using the height of the road at the location where the transmitter is installed, the inclination angle of the center line of the radar wave transmitted from the transmitter with respect to the horizontal plane, and the beam width of the radar wave as parameters. The obstacle detection device according to claim 1, wherein the obstacle detection device stores the distance from the host vehicle at the point where the occurrence of. 3. The signal processing means includes an amplifier circuit for amplifying a signal of a reflected wave according to a reception time of the signal, and an amplifier for reducing an amplification factor of a signal corresponding to a road surface reflected wave when the signal is amplified by the amplifier circuit. Claim 1 or Claim 2 which consists of a rate correction part.
The obstacle detection device described. 4. The identifying means, when the vehicle height is changed from a reference height by a vehicle height adjusting device mounted on the host vehicle,
The obstacle detection device according to claim 2, further comprising a correction unit that corrects a distance, which is stored in advance, of a point where the road surface reflected wave occurs from the host vehicle, according to the change amount.