JPH1184001A - Vehicle-mounted radar device and automatic control system of vehicle using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a vehicle-mounted radar device capable of detecting the accuracy of information on a reflector by providing a means to determine and add the accuracy of information on the reflector measured on the basis of the level distribution of received reflected waves over detected directions of transmission and reception. SOLUTION: For example, in the case that a reflector R is present in front of a one's own vehicle V, the most part of the radiation power of a beam Be on the rightest end and the considerable part of that of a beam Bd are reflected by the reflector R, and beams Bb and Ba are not reflected. As a result, in the levels La to Le of beat signals obtained from the received reflected waves of the radiated five beams Ba to Be, the level Le of the beam Be becomes the maximum. A CPU computes the distance and direction to the reflector R by obtaining the weighted mean of the level of the beat signal on each radiation direction. Discontinuous accuracy is added to measured values from the distribution state of beat signals. As accuracy is added to the measured values of received reflected waves in this way in this constitution, it is possible to improve responsivity by changing the number of measurements and gains for averaging.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an on-vehicle radar device used for an alarm device for preventing collision or collision of a vehicle, and an automatic vehicle control system using the same. The present invention relates to an on-vehicle radar device provided with an accuracy determining / applying means for determining an accuracy based on a distribution of the level of a received reflected wave and adding the accuracy to a measurement result, and an automatic vehicle control system using the same.

[0002]

2. Description of the Related Art For the purpose of application to an alarm device for preventing rear-end collision or collision of a vehicle, a beam such as a radio wave or a laser beam is transmitted, a reflected wave is received, and information on a reflector which generates the reflected wave is received. An on-vehicle radar device has been developed for detecting a vehicle.
Various types of on-vehicle radar devices such as an FM radar, an AM radar, and a pulse radar for transmitting and receiving a frequency-modulated wave and an amplitude-modulated wave have been developed.

In an on-vehicle radar device, particularly a forward-looking on-vehicle radar device, a single beam having a sharp directivity is mechanically scanned over a certain angle range in front of the vehicle, or covers a certain angle range. In this way, by performing electronic scanning by sequentially transmitting sharp directivity beams from a plurality of antennas arranged in slightly different directions, the reflector exists not only in the distance to the reflector but also in any direction The azimuth resolution is also obtained.

[0004]

In the above-mentioned on-vehicle radar apparatus, it is expected that a false reflected wave is received due to interference with another on-vehicle radar apparatus. Conversely, a true reflected wave may disappear with a decrease in the SN ratio. For this reason, the on-vehicle radar device usually averages not only one measurement result but a large number of measurement results, so that the distance and azimuth to the reflector or the relative speed with respect to the reflector can be measured. Information is detected. Thus, if the number of measurement repetitions is increased in order to increase the accuracy of the reflector information, the time required to obtain one measurement value is prolonged, and as a result, the occurrence of an alarm is delayed or the use of this information is There is a problem that the responsiveness of control such as automatic cruise control to be performed is reduced.

One object of the present invention is to provide an on-vehicle radar device capable of detecting the accuracy of information on a reflector. However, the “accuracy” of the information referred to in the present invention is the “degree of certainty” of the information, and the “reliability (liab
ility) and "accuracy, precision" as subordinate concepts.

Another object of the present invention is to shorten the time until an alarm is generated by dynamically changing the number of repetitions of measurement for averaging in accordance with the accuracy of the detected information.
It is an object of the present invention to provide an on-vehicle radar device capable of improving responsiveness by dynamically increasing or decreasing a loop gain of an automatic control loop.

[0007]

According to the present invention, there is provided an on-vehicle radar apparatus for transmitting a beam in a different transmission direction and receiving a reflected wave of the beam, thereby receiving a reflected wave in the transmission / reception direction. In addition to the function of detecting the level distribution of the received reflected wave in the transmitting and receiving directions detected in addition to the function of measuring information about the reflector such as the distance to the reflector that generated the received reflected wave based on the detection result, There is provided an accuracy determining / applying means for determining and applying the accuracy of the measured information of the reflector based on the level distribution.

According to another aspect of the present invention, in addition to the above-mentioned accuracy determining / applying means, the higher the accuracy given to the information on the reflector, the more the measurement for averaging the information over time. Measurement number changing means for reducing the number of times of measurement.

An automatic control system for a vehicle according to the present invention detects the distribution of the level of a received reflected wave in the transmitting and receiving directions by transmitting beams in different transmitting directions and receiving the reflected waves. An on-vehicle radar device that measures information about the reflector such as a distance to a reflector that has generated a received reflected wave based on the information, and an automatic vehicle that automatically controls traveling of the vehicle based on information detected by the on-vehicle radar device. A control device. The automatic control system further includes accuracy determination / assignment means for determining and applying the accuracy of the information on the measured reflector based on the distribution of the level of the received reflected wave in the transmission / reception direction detected by the on-vehicle radar device. In addition, a control means is provided for increasing the loop gain of the feedback loop based on this information as the accuracy of the automatic control device given to the information on the reflector increases.

[0010]

According to the preferred embodiment of the on-vehicle radar device of the present invention, the distribution of the level of the received reflected wave in the detected transmission / reception direction has a large spread in the transmission / reception direction in which the received reflected wave exists. The greater accuracy is given to the measured information.

According to another preferred embodiment of the present invention,
In the detected distribution of the level of the received reflected wave in the transmission / reception direction, the larger the width of the transmission / reception direction and the higher the level of the received reflected wave, the greater the accuracy is given to the measured information.

According to still another preferred embodiment of the present invention, if the distribution of the level of the received reflected wave in the detected transmission / reception direction is symmetrical or monotonically increased and decreased on both sides with the center as the maximum. , A large accuracy is given to the measured information, otherwise a small accuracy is given to the measured information.

According to still another preferred embodiment of the present invention, the accuracy judging / giving means includes an average value of the distribution of the level of the received reflected wave in the detected transmission / reception direction and a newly detected transmission / reception direction in the transmission / reception direction. The above-mentioned accuracy is added to the measured information in consideration of the degree of coincidence with the distribution of the level of the received reflected wave.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Before describing the features of the present invention, an example of a specific configuration and operation of an on-vehicle radar device to which the present invention is applied will be described with reference to a multi-beam FM radar device according to an embodiment of the present invention. To explain. Multi-beam F of this embodiment
As shown in the functional block diagram of FIG.
It comprises an FM radar module 10 and a main body 20.

The FM radar module 10 comprises a dielectric substrate 11 and five transmission / reception channels A, B... E formed on the dielectric substrate 11. The transmission / reception channels A to E are formed correspondingly to 5
The transmission / reception common antennas 12a to 12p and the corresponding five transmission / reception units.

Each of the transmitting and receiving units includes circulators 14a to 14a.
4e, transmission selection amplifiers 15a to 15e, reception selection amplifiers 16a to 16e, and mixers 17a to 17e. Each of the five transmission / reception channels A to E is a millimeter-wave band FM to be transmitted supplied from the FM signal generation circuit 23 in the main body unit 20 through the microstrip line MS.
Receive a signal.

The main unit 20 includes a CPU 21, a channel control circuit 22, an FM signal generation circuit 23, a sector 24, an A / D
Converter 25, fast Fourier transform circuit 26, and memory 27
It has.

The FM signal in the millimeter wave band output from the FM signal generating circuit 23 of the main body 20 has a so-called sawtooth shape in which the frequency increases linearly with time and then returns to the original frequency in a very short time. The frequency is changed. The signals are supplied to the transmission selection amplifiers 15a to 15e in each of the transmission and reception channels A to E and the reception selection amplification supplies 16a to 16e through the microstrip line MS, and are selectively amplified only within a predetermined period by the corresponding amplifiers. Receive. Each of the transmission selection amplification supply units 15a to 15e sequentially performs the amplification operation of the FM signal only in a predetermined period in the order of arrangement according to the channel control signal supplied from the channel control circuit 22 of the main body unit 20.

The FM signal in the millimeter wave band amplified by each of the transmission amplifiers 15a to 15e is supplied to the circulator 14a.
To 14e, and the transmitting / receiving antenna 1
It is supplied to the corresponding ones of 2a to 12e and radiated to the space outside the vehicle. Each of the transmission / reception shared antennas 12a to 12e includes a primary radiator formed of a planar array antenna formed on the dielectric substrate 11, a secondary radiator (not shown), and the like. The directivity of each of the common transmitting and receiving antennas 12a, 12b,.
According to the intensity distribution of e, as shown in FIG. 1, the directions of the centers of the beams are slightly shifted in the order of arrangement so that they are almost the same and the nearest neighbors overlap.

Some of the millimeter wave band FM signals radiated to the outside of the vehicle are reflected by an object such as a preceding vehicle in front, and follow a reverse route to that of radiation to transmit and receive the antenna 1.
2a to 12e. The reflected wave received by each transmitting / receiving antenna is transmitted to the corresponding circulator 14.
The signals are separated from the transmission system by a to e and input to the reception signal input terminal, which is one input terminal of the mixers 17a to 17e in the transmission / reception unit. The local selection input terminals, which are the other input terminals of the mixers 17a to 17e, are provided with reception selection amplifiers 16a to 16e that perform an intermittent amplification operation within a predetermined period only in a predetermined period according to the channel control signal supplied from the channel control circuit 22. , FM signals are sequentially supplied.

The beat signals output from the output terminals of the mixers 17a to 17e are supplied to an A / D converter 25 of the main unit 20 via a line such as a coaxial cable, and are converted into corresponding digital signals. The beat signal converted into the digital signal is supplied to the fast Fourier transform circuit 26, where it is converted into a frequency spectrum and supplied to the CPU 21.

The CPU 21 includes a fast Fourier transform circuit 26
The frequency of the beat signal (beat frequency) is analyzed by analyzing the frequency spectrum of the beat signal received from
And the level of this frequency component. The beat frequency is composed of a component proportional to the distance to the reflector and a Doppler shift component proportional to the relative speed with respect to the reflector. For simplicity, the latter Doppler shift component is compared with the former component. And can be ignored. In addition,
If necessary, a constant frequency signal or an FM signal that increases or decreases linearly with time is radiated, and the reflected wave is received to generate a beat signal, thereby separating the component proportional to the distance from the Doppler shift component. You can also.

The CPU 21 detects the distance from the beat frequency to the reflector for the transmission / reception channels A to E, and thus for the different directions of the beams Ba to Be. C
As illustrated in FIG. 5, the PU 21 creates a two-dimensional map of the level (amplitude) of the frequency component of the beat signal in a two-dimensional space of the distance and the azimuth in front of the own vehicle. Since the level of the beat signal is substantially proportional to the level of the received reflected wave, the level of the beat signal indicates the level of the received reflected wave.

Here, it is assumed that a reflector R such as a preceding vehicle exists in front of the own vehicle V as shown in FIG. In this case, for the central beam Bc, most of the emitted power is reflected by the reflector R, and for each of the two nearest neighbor beams Bb and Bd, a significant portion of the emitted power is reflected. Reflected by the body R and the two outer beams Ba and Be
, Only a small portion of the emitted power is reflected by reflector R.

As a result, the five emitted beams Ba ビ ー ム
The beat signal levels La to Le having substantially the same frequency obtained from the Be received reflected wave and the radiation direction θa of each beam
A typical relationship with .theta.e (azimuth) is as illustrated in FIG. 1B. That is, the central beam B
c, the beat signal level Lc becomes the maximum, the beat signal levels Lb and Ld become the next largest values for the two adjacent beams Bb and Bd, and the outer two
For the beams Ba and Be, the beat signal level L
a and Le are minimized. Then, the level distribution of each beat signal is symmetrical on both sides with the maximum being the center.

Next, as shown in FIG. 2A, it is assumed that a reflector R such as a preceding vehicle exists diagonally forward right of the host vehicle V. In this case, most of the emitted power is reflected by the reflector R for the rightmost beam Bf, and a considerable portion of the emitted power is reflected by the reflector R for the beam Bd immediately to the left. Receiving
Further, for the center beam Bc on the left side, only a part of the emitted power is reflected by the reflector R. Further, for the two left beams Bb and Ba, the emitted power is not reflected by the reflector R at all.

As a result, the five emitted beams Ba ビ ー ム
The beat signal levels La to Le having substantially the same frequency obtained from the Be received reflected wave and the radiation direction θa of each beam
A typical relationship with .theta.e (azimuth) is as shown in FIG. 2B. For the rightmost beam Be, the level Le of the beat signal becomes maximum, for the beam Bd immediately to the left, the level Ld of the beat signal becomes the next largest value, and for the beam Bc on the left, the level Lc of the beat signal becomes minimum. Become. Further, no beat signal is obtained for the two beams Bb and Ba on the left side. The level distribution of each beat signal is such that it monotonically increases toward the right side.

Similarly, assuming that a reflector R such as a preceding vehicle exists diagonally forward left of the host vehicle V, contrary to the case of FIG. 2A, the level distribution of each beat signal is as follows.
Contrary to the case of FIG. 2 (B), the voltage increases monotonically toward the left side.

The CPU 21 calculates the azimuth の of the reflector as viewed from the own vehicle by weighing and averaging the levels of beat signals having substantially the same frequency obtained in each radiation direction of the beat. Θ = (La · θa + Lb · θb + Lc · θc + Ld · θd + Le · θe) / (La + Lb + Lc + Ld + Le) ... (1)

The distribution of the level of the received reflected wave in the transmission direction, that is, the distribution of the level of the beat signal, described with reference to FIGS. 1 and 2, is free from interference from other on-vehicle radar devices. Further, it can be obtained only in an ideal case where the SN ratio is good because the distance between the reflectors is short. Actually, with the appearance of a false signal caused by interference from other on-vehicle radar devices and the disappearance of a true signal caused by a decrease in the SN ratio, the distribution of beat signal levels is shown in FIG. 1 and FIG. Various patterns appearing in FIG. 3 different from those illustrated in FIG.

FIG. 3A shows that despite the absence of a reflector such as a preceding vehicle in front of the own vehicle, interference from another radar device mounted on an oncoming vehicle or the like causes
This is an example in which a large-level beat signal is obtained only in a certain direction. FIGS. 3B and 3C show examples in which some of the low-level true signals are lost due to deterioration of the SN ratio or the like. Such deterioration of the S / N ratio also occurs because the level of the received reflected signal is reduced due to an increase in the distance to a reflector such as a preceding vehicle or an increase in propagation attenuation due to rainfall.

In the case of FIG. 3, the reliability (reliability) is used for information such as the detected value of the distance to the reflector calculated from the beat frequency and the measured value of the azimuth of the reflector calculated from equation (1).
abi-lity) and the level of the averaging object decrease, so that the accuracy (accu-racy, precision) also decreases.

Taking this point into consideration, the distance and azimuth measurement values obtained under various patterns relating to the state of the distribution of the beat signal are calculated in a continuous manner set in advance according to the pattern. Alternatively, several steps of discrete accuracy P are given. As an example, the totality of beat signal levels for all azimuths, P ₁ = ΣLi = La + Lb + Lc + Ld + Le (2), can be set as the accuracy P.

As another accuracy, P ₂ = n (3) can be set. Here, in the case of this embodiment, n is the number in the radiation direction where the level of the beat signal exceeds a predetermined threshold. When the beam is continuously changed over a certain angular range by mechanical scanning, n corresponds to the radial angular range where the beat signal level exceeds a predetermined threshold.

For the above-mentioned accuracy P ₁ and P ₂ , FIG.
2B, the presence or absence of symmetry about a certain maximum value of the beat signal level, and the monotonic increase and monotonic decrease of the beat signal level between adjacent beams as illustrated in FIG. By combining the discontinuous probabilities set based on the presence / absence, it is possible to set the overall accuracy.

The CPU 21 gives an accuracy set in advance based on one of the above-mentioned several methods or a combination thereof to the measured values of the distance and azimuth of the reflector. CP
U21 sets the number of measurements for averaging to a small value when the assigned accuracy is high, and sets the number of measurements for averaging to a large value when the assigned accuracy is low. . As described above, the CPU 21 dynamically changes the number of measurements for averaging in accordance with the accuracy given to the measured information.

The CPU 21 determines that the level distribution of the new beat signal obtained by the new measurement for averaging substantially coincides with the averaged level distribution of the beat signal obtained so far. Reduces the number of times of averaging by giving a new type of accuracy resulting from the coincidence in the time axis direction to the measured values of distance and azimuth obtained so far. As described above, the CPU 21 compensates for the lack of accuracy provided based on the distribution of the level of the beat signal by increasing the number of times of the averaging process, thereby detecting a measurement value of approximately the same accuracy.

When the shortage of accuracy provided based on the distribution of the level of the beat signal in the transmission direction is not compensated for by increasing the number of measurements for averaging,
Various measured values (information on the reflector) such as a distance, an azimuth, and a relative speed with respect to the reflector are added to the accuracy that fluctuates over a certain range, and are transmitted to an alarm device (not shown), an automatic traveling control device, or the like.

If the accuracy added to the distance from the reflector transferred from the CPU 21 is high, the alarm device issues an alarm about a rear-end collision with the preceding vehicle as soon as this distance exceeds the first threshold. Conversely, if the accuracy added to the distance from the reflector transferred from the CPU 21 is low, the alarm device will not send the preceding vehicle to the vehicle until the distance exceeds the second threshold higher than the first threshold. Does not issue a warning about rear-end collision.

If the accuracy added to the distance to the reflector transmitted from the CPU 21 is high, the automatic cruise control device such as the inter-vehicle distance maintaining device considers this distance to be the inter-vehicle distance from the preceding vehicle. If the accuracy added to the distance from the reflector transferred from the CPU 21 is low, the loop gain of the feedback control loop is decreased. 0

The example in which the level of the beat signal forming the distribution of the level of the received reflected wave in the transmission direction is used as the criterion for accuracy has been described. However, instead of the beat signal level, a ratio (SN ratio) of the beat signal level to the separately measured noise level may be used as the accuracy criterion.

The on-vehicle radar device according to the present invention has been described by taking as an example a case where a reflected wave of a beam transmitted from an arbitrary antenna is received by the same antenna. However, as disclosed in Applicant's Patent No. 2,567,332,
By adding an operation to receive a beam transmitted from an arbitrary antenna with another antenna such as an adjacent antenna, a virtual antenna with directivity equivalent to multiplying the directivity of different transmitting and receiving antennas is added and azimuth resolution The present invention can also be applied to improve In this case, the "transmission side
The expression level of the received reflected wave "over the counter," sending and receiving
The level of the received reflected wave over the transmission direction may be expanded.

Further, the present invention has been described by taking the case of FM radar as an example. However, the on-vehicle radar device of the present invention is not limited to the FM radar, and can be applied to other appropriate radar devices such as an AM radar and a pulse radar that transmit and receive a radio wave beam or a laser beam.

Also, a configuration in which a plurality of antennas are installed so as to emit beats in different directions and time-divisionally operated to scan a beam has been exemplified. However, it is clear that the present invention can be applied to a configuration in which the scanning of the beam is continuously performed by mechanical scanning of an antenna, a reflecting mirror, or the like.

[0045]

As described in detail above, the on-vehicle radar device according to the present invention has the following characteristics: the width of the transmitting direction in which the received reflected wave exists, the product of the width of the transmitting direction and the amplitude of the received reflected wave, and the center. Since the accuracy is given to measured values such as distance and direction according to the presence or absence of symmetry to be maximized or monotonous increase / decrease, the number of measurements and loop gain for averaging can be dynamically adjusted. It is possible to increase the responsiveness by changing to.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram for explaining the principle of the present invention.

FIG. 2 is a conceptual diagram for explaining the principle of the present invention.

FIG. 3 is a conceptual diagram for explaining the principle of the present invention.

FIG. 4 is a functional block diagram illustrating a configuration of an on-vehicle FM radar device according to an embodiment of the present invention.

FIG. 5 is a conceptual diagram showing an example of a two-dimensional map created by the on-vehicle FM radar device of FIG. 4;

[Explanation of symbols]

V Self-vehicle R Reflector such as preceding vehicle Ba-Be Beam that is superimposed little by little and emitted in slightly different directions θa-θe Azimuth angle of each radiation beam La-Le Beat obtained from received reflected wave of each radiation beam Signal level 10 FM radar module AE transmission / reception channel 20 Main unit 21 CPU

Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI G08G 1/16 G01S 13/34 // G01S 13/34 17/88 A

Claims (7)

[Claims] 1. A distribution of the level of the received reflected wave in the transmitting and receiving directions is detected by transmitting a beam in a different transmitting direction and receiving the reflected wave, and generating the received reflected wave based on the detection result. An in-vehicle radar device having a function of measuring information about the reflector such as a distance to the reflector, wherein the accuracy of the information of the measured reflector is based on the distribution of the level of the received reflected wave in the detected transmission and reception direction. An in-vehicle radar device comprising: an accuracy determining / giving means for judging and giving a judgment. 2. The method according to claim 1, wherein in the level distribution of the received reflected wave in the detected transmission / reception direction, the greater the spread of the transmission / reception direction in which the received reflected wave exists, the greater the accuracy is given. In-vehicle radar device. 3. The method according to claim 1, wherein in the distribution of the level of the received reflected wave in the detected transmission / reception direction, a greater accuracy is given as the width of the transmission / reception direction is larger and the level of the received reflected wave is larger. Characteristic on-vehicle radar device. 4. The method according to claim 1, wherein if the distribution of the level of the received reflected wave in the detected transmission / reception direction is symmetrical or monotonically increased or decreased on both sides with the center being the maximum, great accuracy is given. In the case of (1), a small accuracy is provided. 5. A distribution of the level of the received reflected wave in the transmitting and receiving directions by transmitting a beam in a different transmitting direction and receiving the reflected wave, and generating the received reflected wave based on the detection result. An in-vehicle radar device having a function of measuring information about the reflector such as a distance to the reflected reflector, the accuracy of the information about the measured reflector based on the distribution of the level of the received reflected wave in the detected transmission / reception direction. Accuracy determining / applying means for determining and applying, and the number of measurement changing means for reducing the number of measurements for time averaging of this information, as the accuracy given to the information on the reflector increases, An in-vehicle radar device characterized in that: 6. The method according to claim 5, wherein the accuracy determination / assignment unit calculates an average value of the distribution of the level of the received reflected wave in the detected transmission / reception direction and a distribution of the level of the received reflected wave in the newly detected transmission / reception direction. The in-vehicle radar device is characterized in that the accuracy is given in consideration of the degree of coincidence of the radar. 7. Transmitting a beam in a different transmission direction and receiving the reflected wave to detect a distribution of the level of the received reflected wave in the transmitting and receiving directions, and generating the received reflected wave based on the detection result. A vehicle equipped with an on-vehicle radar device for measuring information about the reflector such as a distance to the reflected reflector, and an automatic control device for automatically controlling travel of the vehicle based on information detected by the on-vehicle radar device In the automatic control system of the above, the on-vehicle radar device, the accuracy determining and providing means for determining and providing the accuracy of the information about the measured reflector based on the detected distribution of the level of the received reflected wave over the transmission and reception direction, The automatic control device, the higher the accuracy given to the information about the reflector, the higher the loop gain of the feedback loop based on this information Automatic control system for a vehicle, characterized in that it comprises a control means for pressurizing.