JP5846472B2 - Vehicle object detection device - Google Patents

Description

  The present invention relates to an object detection device used in a driving support device that controls a vehicle in order to prevent a rear-end collision or the like.

  Japanese Patent Application Laid-Open No. 5-142337 discloses a millimeter wave radar distance and velocity measuring device that obtains a distance and velocity with respect to a target from a beat signal of a continuous transmission signal of triangular wave modulation and a reception signal reflected by the target. ing. The distance to the target and the relative speed are obtained by combining the frequencies of the rising beat signal and the falling beat signal in the triangular wave modulation.

JP-A-5-142337

  In a driving support device that controls a vehicle to prevent a collision accident, an autonomous object detection device such as a radar sensor is used to detect vehicle approach information and the like. However, in the millimeter wave radar distance and velocity measuring apparatus described in Japanese Patent Laid-Open No. 5-142337, many continuous peak frequencies appear when there are structures such as roadside walls in the detection range. The combination is difficult. If the combination of peak frequencies is wrong, an accurate distance and speed cannot be obtained, the detection accuracy is lowered, and the target (object) may be erroneously detected. Moreover, it is difficult to specify whether the detected object is a vehicle, and the recognition accuracy is low.

  Accordingly, an object of the present invention is to provide an object detection device for a vehicle that can reduce the detection accuracy and detection errors of an object and can improve the recognition accuracy of the object.

In order to achieve the above object, the present invention is an object detection device for a vehicle, comprising: a vehicle speed detection means, an object detection means, an object information calculation means, another vehicle information acquisition means, a vehicle position sensor, Other vehicle information calculation means and determination means. The own vehicle speed detecting means detects the speed of the own vehicle. The object detecting means detects a plurality of objects existing ahead of the traveling direction of the host vehicle. The object information calculation means calculates the distances between the plurality of objects detected by the object detection means and the host vehicle. The other vehicle information acquisition means acquires the other vehicle position information specifying the position of the other vehicle and the speed of the other vehicle by at least one of inter-vehicle communication or road-to-vehicle communication. The own vehicle position sensor acquires the own vehicle position information for specifying the position of the own vehicle using GPS . The other vehicle information calculation means calculates the distance between the other vehicle and the own vehicle as a reference distance from the other vehicle position information acquired by the other vehicle information acquisition means and the own vehicle position information acquired by the own vehicle position sensor . The determining means determines whether or not the object detecting means has detected another vehicle as an object.
The object detection means emits a frequency-modulated electromagnetic wave as a transmission wave, detects an object by receiving a reflected wave of the emitted transmission wave, and generates a beat signal of the transmission wave and the reception wave for each detected object Then, by analyzing the frequency of the generated beat signal, the peak frequency of the beat signal is detected as a combination of two frequencies . The determination means calculates the beat frequency Fr corresponding to the reference distance , and increases the frequency Δf from zero in the peak frequency combination (Fr ± Δf) that is increased or decreased by the frequency Δf around the calculated beat frequency Fr. When the combination of the detected peak frequencies within the predetermined range is searched for the combination of peak frequencies (Fr ± Δf) and the combination of the detected peak frequencies within the predetermined range can be searched , object detection It is determined that the means has detected another vehicle as an object. When the determination unit determines that the object detection unit has detected the other vehicle as an object, the object information calculation unit is configured to search for the distance between the other vehicle and the host vehicle from among the detected peak frequencies. A peak calculated by using a combination of frequencies , and excluding a combination of a plurality of objects other than the other vehicle and the own vehicle from the detected peak frequency and a combination of the peak frequencies that can be searched by the determination unit Calculate using the frequency.

Other vehicle information acquisition means, the position of the other vehicle, since acquired by standardized communication means of the vehicle-to-vehicle communication or road-to-vehicle communication, development costs becomes possible to design a device along the standard reduction and development period Shortening is possible.

  ADVANTAGE OF THE INVENTION According to this invention, the fall of the detection accuracy of the object detection apparatus of a vehicle can be prevented, false detection can be reduced, and the recognition accuracy of an object can be improved.

It is a block diagram which shows the principal part of the vehicle carrying the driving assistance apparatus using the object detection apparatus of this invention. It is a schematic diagram which shows the object detection condition of the millimeter wave radar sensor of FIG. It is a wave form diagram of a transmission wave and a reflected wave of a millimeter wave radar sensor. It is a figure showing the result of the frequency analysis at the time of detecting one object. It is a figure showing the result of a frequency analysis at the time of detecting a plurality of objects. It is a schematic diagram which shows the method of searching a peak frequency using a reference distance and a reference frequency.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a main part of a vehicle equipped with a driving support device using the object detection device of the present invention. As shown in FIG. 1, a vehicle 1 according to this embodiment includes a millimeter wave radar sensor (object detection means) 4, a host vehicle position sensor (own vehicle position detection means) 5, and a host vehicle speed sensor (own vehicle speed detection means). ) 6, a communication device (other vehicle information acquisition means) 7, an alarm device 8, a brake actuator 9, and a CPU 10.

  The millimeter wave radar sensor 4 directs a transmission wave, which is a continuous electromagnetic wave (FM-CW) in a millimeter wave band subjected to frequency modulation of a triangular wave, within a predetermined angle range from the front end of the vehicle 1 in the traveling direction. Are emitted at regular intervals, receive a received wave that is a reflected wave from the object 2 existing in front of the vehicle 1, and detect the object 2 (see FIG. 2). Subsequently, the beat signal is generated by mixing the transmission wave and the reception wave, and the generated beat signal is subjected to frequency analysis by fast Fourier transform (FFT).

  Here, since the reception wave from the object 2 has a time delay due to reciprocating the distance L between the object 2 and the vehicle 1 with respect to the transmission wave (see FIG. 3), the frequency analysis of the beat signal is performed. The beat signals in the rising section (up side) and the falling section (down side) of the frequency modulation by the triangular wave have peak frequencies Fu (up side) and Fd (down side) having a peak at the beat frequency Fl corresponding to the distance L. Side) occurs.

Fu = Fd = Fl (1)
Fl = k1 · L (k1: constant) (2)

Further, when there is a relative velocity V between the object 2 and the vehicle 1, a frequency shift (Doppler shift) due to the Doppler effect occurs in the reflected wave (see FIG. 3), and therefore the peak frequency of the up-side beat signal The frequency of Fu decreases from the beat frequency Fl when the relative speed is zero by the beat frequency Fv corresponding to the relative speed V. The peak frequency Fd of the beat signal on the down side increases from the beat frequency Fl when the relative speed is zero by the beat frequency Fv corresponding to the relative speed V (see FIG. 4). That is,
Fu = Fl−Fv (3)
Fd = Fl + Fv (4)
Fv = k2 · V (k2: constant) (5)

When there are a plurality of detected objects 2, a plurality of peak frequencies Fu and Fd corresponding to the number of the objects 2 are generated in the up-side and down-side beat signals, respectively. FIG. 5 shows a case where three objects 2 are detected. Peak frequencies of Fu1 to Fu3 and Fd1 to Fd3 are generated in the beat signals on the up side and the down side, respectively.
The millimeter wave radar sensor 4 detects the plurality of up-side peak frequencies Fu and the down-side peak frequency Fd and outputs them to the CPU 10.

  The own vehicle position sensor acquires the position of the vehicle 1 at predetermined time intervals using a GPS (Global Positioning System) and outputs the position to the CPU 10.

  The own vehicle speed sensor 6 detects the vehicle speed of the vehicle 1 every predetermined time and outputs it to the CPU 10.

  The communication device 7 acquires the position and vehicle speed of the other vehicle 3 transmitted from the other vehicle 3 at predetermined time intervals and outputs the same to the CPU 10 by at least one communication method of vehicle-to-vehicle communication or road-to-vehicle communication.

  As shown in the block diagram of FIG. 1, the CPU 10 includes another vehicle information calculation processing unit (other vehicle information calculation means) 11, a determination processing unit (determination means) 12, and an object information calculation processing unit (object information calculation means). 13 and a collision prevention control unit 14 are provided. When a switch (not shown) of the driving support device is turned on, the CPU 10 executes these processes every predetermined time.

The other vehicle information calculation processing unit 11 receives the position and speed of the other vehicle 3 input from the communication device 7, the position of the vehicle 1 input from the own vehicle position sensor 5, and the vehicle 1 input from the own vehicle speed sensor 6. The speed is acquired, and a reference distance Lr that is a distance between the other vehicle 3 and the vehicle 1 and a reference relative speed Vr that is a relative speed between the other vehicle 3 and the vehicle 1 are calculated.

  The determination processing unit 12 determines whether the millimeter wave radar sensor 4 has detected the other vehicle 3 for which the reference distance Lr to the vehicle 1 and the reference relative speed Vr have been calculated by the other vehicle information calculation processing unit 11. That is, the determination processing unit 12 first substitutes the reference distance Lr and the reference relative speed Vr calculated by the other vehicle information calculation processing unit 11 into the equations (2) and (5), and the equations (3) and ( 4), the peak frequency Fur of the up-side beat signal and the peak frequency Fdr of the down-side beat signal, which are reference peak frequencies corresponding to the reference distance Lr and the reference relative velocity Vr, are calculated.

Fur = k1, Lr-k2, Vr (6)
Fdr = k1 · Lr + k2 · Vr (7)

  Next, as shown in FIG. 6, the determination processing unit 12 determines that the difference from the Fur is within a predetermined range among the plurality of up-side peak frequencies for the plurality of objects 2 detected by the millimeter wave radar sensor 4. The presence / absence of the peak frequency Fu of a certain object 2 is searched. Similarly, a search is made for the presence or absence of a peak frequency Fd whose difference from Fdr is within a predetermined range among the peak frequencies on the down side. In the example shown in FIG. 6, a pair of peak frequencies Fu2 and Fd2 among the detected peak frequencies Fu1 to Fu3 and Fd1 to Fd3 is searched as a peak frequency corresponding to the reference peak frequencies Fur and Fdr. Is done. When the pair of peak frequencies Fu and Fd can be searched, the determination processing unit 12 determines that the object 2 corresponding to the peak frequencies Fu and Fd is the other vehicle 3. When the peak frequency pair whose difference from Fur and Fdr is within the predetermined range cannot be searched for in the peak frequency, the millimeter wave radar sensor 4 detects the other vehicle 3 having the reference distance Lr and the reference relative velocity Vr. It is conceivable that it was not detected. For example, there may be a case where a small vehicle is traveling in front of a large vehicle and a transmission wave from the millimeter wave radar sensor 4 is difficult to reach.

  The object information calculation processing unit 13 combines the up-side peak frequency Fu and the down-side peak frequency Fd of the plurality of objects 2 detected by the millimeter wave radar sensor 4, thereby obtaining the object 2 and the vehicle 1 respectively. The distance L and the relative speed V are calculated. Specifically, first, for the object 2 determined to be the other vehicle 3 by the determination processing unit 12, the peak frequencies Fu and Fd whose difference from the reference peak frequencies Fur and Fdr are within a predetermined range are obtained. combine. In the example shown in FIG. 6, Fu2 and Fd2 are combined. When there are a plurality of objects 2 determined to be other vehicles 3, a combination of a plurality of peak frequencies is created. Next, for the object 2 (other object) excluding the object 2 determined to be the other vehicle 3, the peak frequency at which the difference between the reference peak frequencies Fur and Fdr is within a predetermined range from the peak frequency. Using the remaining peak frequencies excluding the combination of Fu and Fd, the up-side peak frequency Fu and the down-side peak frequency Fd corresponding to the distance L and the relative speed V between the object 2 and the vehicle 1 are combined. In the example shown in FIG. 6, combinations are made using Fu1, Fu3 and Fd1, Fd3, excluding the combination of Fu2 and Fd2. Subsequently, the combined peak frequencies Fu and Fd are substituted into the equations (8) and (9), and the distance L and the relative speed V between all the detected objects 2 and the vehicle 1 are calculated.

L = (Fd + Fu) / 2k1 (8)
V = (Fd−Fu) / 2k2 (9)

  Further, in the determination processing unit 12, when there is an undetected other vehicle 3, the reference distance Lr and the reference relative speed Vr for the undetected other vehicle 3 are added to the calculation result of the object 2.

  The collision prevention control unit 14 calculates a collision margin time TTC (Time to Collision) obtained by dividing the distance L between the object 2 and the vehicle 1 calculated by the object information calculation processing unit 13 by the relative speed V. For the object 2 with the shortest TTC, when the TTC falls below a first predetermined time (for example, 3 seconds), it is output to the alarm device 8 to alert the driver. Further, when the TTC becomes equal to or shorter than a second predetermined time (for example, 0.8 seconds), the brake actuator 9 is operated to decelerate the vehicle 1 and avoid a collision with the object 2.

  In the present embodiment, the reference peak frequencies Fur and Fdr corresponding to the reference distance Lr and the reference relative speed Vr between the other vehicle 3 and the vehicle 1 are selected from the peak frequencies of the plurality of objects 2 detected by the millimeter wave radar sensor 4. When the corresponding peak frequency can be searched, it is determined that the object 2 corresponding to the peak frequency is the other vehicle 3. Therefore, it can be surely recognized that the object 2 detected by the millimeter wave radar sensor 4 is the other vehicle 3. When there is a stopped vehicle on the roadside or the like, it is detected as a stationary object 2 by the millimeter wave radar sensor 4, but when the stopped vehicle is transmitting position information, the detected stationary object is detected. However, it can be recognized that the vehicle 3 is not a roadside structure or the like.

  In addition, when the peak frequency corresponding to the reference peak frequencies Fur and Fdr can be searched, the object information calculation processing unit 13 determines the other vehicle from the peak frequencies Fu and Fd excluding the combination of the peak frequencies corresponding to the reference peak frequency. The distance L and the relative distance V of other objects 2 excluding the object 2 determined to be 3 are calculated. Therefore, as in the example shown in FIG. 6, the number of peak frequencies used for the calculation is reduced, so that the accuracy of the calculation is improved, and a reduction in detection accuracy and an erroneous detection can be prevented by combining erroneous peak frequencies. .

  Even when the peak frequency corresponding to the reference distance Lr and the reference relative velocity Vr cannot be searched, that is, even when the millimeter wave radar sensor 4 cannot detect the object 2 determined as the other vehicle 3, the other vehicle information Since the information of the reference distance Lr and the reference relative speed Vr between the other vehicle 3 and the vehicle 1 obtained by the arithmetic processing unit 11 can be acquired, undetected about the other vehicle 3 is reduced.

  Further, the reference distance Lr and the reference relative speed Vr between the other vehicle 3 and the vehicle 1 obtained by the other vehicle information calculation processing unit 11 are based on position information obtained by GPS positioning and speed information such as a vehicle sensor. Is expensive. Accordingly, the distance L and the relative speed V between the object 2 and the vehicle 1 detected by the millimeter wave radar sensor 4 are used as the measurement values for the object 2 determined as the other vehicle 3. In addition, for the other object 2, the calculated values of the distance L and the relative speed V between the other object 2 and the vehicle 1 are corrected to be measured values using the reference distance Lr and the reference relative speed Vr as reference values. Thus, the accuracy of the measurement value of the millimeter wave radar sensor 4 can be improved.

  Thus, according to the present embodiment, the recognition accuracy and measurement accuracy of the object 2 detected by the millimeter wave radar sensor 4 are improved, and false detection and non-detection are reduced, so that driving caused by erroneous object information is performed. False alarms and malfunctions of the support device can be reduced.

  The determination processing unit 12 calculates reference peak frequencies Fur and Fdr corresponding to the distance Lr between the other vehicle 3 and the vehicle 1 and the reference relative speed Vr, and the peak frequencies Fu and Fd detected by the millimeter wave radar sensor 4. Compare directly with. Therefore, it becomes easy to search for the peak frequency of the object 2 corresponding to the reference peak frequency, and the calculation load of the object information calculation processing unit 13 is reduced.

  Moreover, since the information of the position and speed of the other vehicle 3 is acquired by the standardized communication method of vehicle-to-vehicle communication or road-to-vehicle communication, the communication device 7 can be designed according to the standard. Therefore, the development cost can be reduced and the development period can be shortened.

  The other vehicle information calculation processing unit 11 is based on the position of the vehicle 1 obtained from the own vehicle position sensor 5 and the position of the other vehicle 3 obtained from the communication device 7, and the reference distance Lr between the other vehicle 3 and the vehicle 1. The determination processing unit 12 searches the peak frequency Fur corresponding to the reference distance Lr from the peak frequency detected by the millimeter wave radar sensor 4 and determines whether the detected object 2 is the other vehicle 3 or not. May be determined. In this case, since the reference relative speed Vr is unknown, the beat frequency Fr corresponding to the reference distance Lr is calculated from the equation (2), and the frequency Δf corresponding to the unknown reference relative speed is increased or decreased around Fr. A combination of peak frequencies of Fr−Δf and Fr + Δf is made. Next, while increasing Δf from zero, a combination of peak frequencies of the object 2 detected by the millimeter wave radar sensor 4 existing within a predetermined range with respect to Fr ± Δf is searched. When a combination of peak frequencies of the object 2 can be searched within the predetermined range, it can be determined that the object 2 corresponding to the peak frequency is the other vehicle 3.

  In addition, the object information calculation processing unit 13 stores the calculated distance L and relative speed V for the object 2 as time series data, and uses it in the combination of the peak frequencies Fu and Fd for the object 2 detected this time. Also good. Using the distance and relative speed of the object 2 stored in the time series data before the previous time, the distance and relative speed of the object 2 detected this time are estimated and referred to, so that the peak frequencies Fu and Fd are more accurate. Combinations are possible.

  The object detection means is not limited to the millimeter wave radar of the present embodiment, and may be, for example, an image sensor that images the object 2 with a camera or the like and detects the distance to the object 2 by a known triangle method or the like. May be. That is, the determination processing unit 12 includes at least one of the distance L and the relative speed V between the plurality of objects 2 and the vehicle 1 detected by the image sensor, the other vehicle 3 and the vehicle calculated by the other vehicle information calculation processing unit 11. 1 is compared with at least one of the reference distance Lr and the reference relative speed Vr, the object 2 corresponding to the reference distance Lr can be determined to be the other vehicle 3. Therefore, it can be surely recognized that the determined object 2 is the other vehicle 3. Further, the reference distance Lr is used as a measured value of the determined distance L of the object 2, and the distance L of the other object 2 is corrected by using the reference distance Lr as a reference value to obtain a measured value. The accuracy of the measured value of the sensor can be improved.

  In the present embodiment, one CPU 10 executes the detection of the object 2 and the collision prevention control process. However, the processing device that executes the detection of the object 2 is different from the processing device that executes the collision prevention control. You may comprise as another unit. Therefore, a device (unit) that performs detection of the object 2 may be added to the existing vehicle 1 that includes a device that executes the collision prevention control process. On the other hand, the present invention can be easily applied.

  As mentioned above, although the embodiment to which the invention made by the present inventor is applied has been described, the present invention is not limited by the discussion and the drawings that form part of the disclosure of the present invention according to this embodiment. That is, it is needless to say that other embodiments, examples, operation techniques, and the like made by those skilled in the art based on this embodiment are all included in the scope of the present invention.

  The present invention is widely applicable to vehicle driving support devices.

DESCRIPTION OF SYMBOLS 1 Vehicle 2 Object 3 Other vehicle 4 Millimeter wave radar sensor 5 Own vehicle position sensor 6 Own vehicle speed sensor 7 Communication apparatus 10 CPU
11 Other vehicle information calculation processing unit 12 Determination processing unit 13 Object information calculation processing unit

Claims (1)

Own vehicle speed detecting means for detecting the speed of the own vehicle;
Object detection means for detecting a plurality of objects present ahead of the traveling direction of the host vehicle;
Object information calculation means for calculating distances between the plurality of objects detected by the object detection means and the host vehicle;
Other vehicle information acquisition means for acquiring other vehicle position information for specifying the position of another vehicle and the speed of the other vehicle by at least one of vehicle-to-vehicle communication or road-to-vehicle communication;
A vehicle position sensor for acquiring the vehicle position information for specifying the position of the vehicle by using GPS ;
Other vehicle information calculation means for calculating the distance between the other vehicle and the own vehicle as a reference distance from the other vehicle position information acquired by the other vehicle information acquisition means and the own vehicle position information acquired by the own vehicle position sensor. When,
Determination means for determining whether or not the object detection means has detected the other vehicle as the object,
The object detecting means emits a frequency-modulated electromagnetic wave as a transmission wave, detects an object by receiving a reflected wave of the emitted transmission wave, and beats the transmission wave and the reception wave for each detected object. By generating a signal and analyzing the frequency of the generated beat signal, the peak frequency of the beat signal is detected as a combination of two frequencies ,
The determination means calculates a beat frequency Fr corresponding to the reference distance , and increases the frequency Δf from zero in a combination of peak frequencies (Fr ± Δf) increased or decreased by a frequency Δf around the calculated beat frequency Fr. However, the combination of the detected peak frequencies within the predetermined range was searched for the combination of the peak frequencies (Fr ± Δf), and the combination of the detected peak frequencies within the predetermined range could be searched. In the case, it is determined that the object detection means has detected the other vehicle as the object,
The object information calculation means, when the determination means determines that the object detection means has detected the other vehicle as the object, determines the distance between the other vehicle and the own vehicle among the detected peak frequencies. the determination means calculates a combination of peak frequency was searched, the distance between the host vehicle and other objects, except the other vehicles of the plurality of objects, the determination means from the detected peak frequency There object detection device for a vehicle, characterized by calculation using the peak frequency excluding the combination of peak frequency can explore.

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