Object detection device for vehicle

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

Japanese Unexamined Patent Publication No. 5-142337 describes a millimeter-wave radar distance / velocity measuring device that obtains a distance and a speed with respect to a target from a beat signal of a continuous transmission signal of trigonal wave modulation and a reception signal reflected by a target. ing. The distance to the target and the relative velocity are obtained by combining the frequencies of the beat signal on the rising side and the frequency of the beat signal on the falling side of the trigonal wave modulation.

<p><patcit num="1"><text>Japanese Unexamined Patent Publication No. 5-142337</text></patcit></p>

<p num="0004"> 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 approach information of the vehicle. However, in the millimeter-wave radar distance / velocity measuring device described in Japanese Patent Application Laid-Open No. 5-142337, many continuous peak frequencies appear when there is a structure such as a roadside wall in the detection range, and the peaks in close proximity to each other appear. Difficult to combine. If the combination of peak frequencies is incorrect, the correct distance and speed cannot be obtained, the detection accuracy will decrease, and there is a possibility that the target (object) will be erroneously detected. In addition, it is difficult to identify whether the detected object is a vehicle, and the recognition accuracy is low.</p><p num="0005"> Therefore, an object of the present invention is to provide a vehicle object detection device capable of improving the object recognition accuracy while reducing the decrease in object detection accuracy and erroneous detection.</p>

<p num="0006"> In order to achieve the above object, the vehicle object detection device of the present invention includes an object detection means, an object information calculation means, another vehicle information acquisition means, another vehicle information calculation means, and a determination means. The object detection means detects a plurality of objects existing in front of the traveling direction of the own vehicle, and detects distance information between the detected plurality of objects and the own vehicle. The object information calculation means calculates the distance between a plurality of objects and the own vehicle from the distance information detected by the object detection means. The other vehicle information acquisition means acquires the other vehicle position information that identifies the position of the other vehicle by communicating with the outside. The own vehicle position acquisition means acquires the own vehicle position information that identifies the position of the own vehicle by communicating with the outside. 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 acquisition means. The determination means determines whether or not the object detection means has detected another vehicle as an object by comparing the reference distance with the distance information detected by the object detection means. When the determination means determines that the object detection means has detected another vehicle as an object, the object information calculation means refers to the distance between the own vehicle and another object other than the other vehicle among the plurality of objects. Calculate using the distance. In the above configuration, the distance information between a plurality of objects and the own vehicle obtained by the object detection means is compared with the reference distance between the other vehicle and the own vehicle based on the other vehicle position information obtained by the other vehicle information calculation means. Then, it is determined whether or not the object detecting means has detected another vehicle as an object. Therefore, it is possible to reliably recognize that the detected object is another vehicle, and the recognition accuracy of the detected object is improved. In addition, since the distance between the own vehicle and another object other than the other vehicle among a plurality of objects is calculated using the reference distance, it is possible to reduce erroneous detection due to erroneous calculation and improve the detection accuracy. it can.</p><p num="0007"> Further, the object detection means emits a frequency-modulated electromagnetic wave as a transmission wave, detects an object by receiving the reflected wave of the emitted transmission wave, and generates and generates a beat signal between the transmission wave and the reception wave. By frequency-analyzing the beat signal, the peak frequency of the beat signal is detected as distance information, and the determination means is used by the object detecting means when a peak frequency corresponding to the reference distance exists in the detected peak frequency. When it is determined that the other vehicle is detected as an object and the determination means determines that the object detection means has detected the other vehicle as an object, the object information calculation means detects the distance between the other object and the own vehicle. The calculation may be performed using the peak frequency obtained by subtracting the peak frequency corresponding to the reference distance from the peak frequency.</p><p num="0008"> In the above configuration, when the determination means determines that another vehicle is detected as an object, the object information calculation means uses the peak frequency obtained by subtracting the peak frequency corresponding to the reference distance from the detected peak frequency to use another vehicle. Calculate the distance between the object and your vehicle. Therefore, the number of peak frequencies to be calculated is reduced, the accuracy of the calculation is improved, the deterioration of the detection accuracy caused by using the wrong peak frequency is prevented, and the false detection is reduced.</p><p num="0009"> Further, the object detection device of the vehicle is provided with a vehicle speed detecting means for detecting the speed of the own vehicle, the other vehicle information acquisition means acquires the speed of the other vehicle by communication with the outside, and the other vehicle information calculation means , The reference relative speed between the other vehicle and the own vehicle is calculated from the speed of the other vehicle acquired by the other vehicle information acquisition means and the speed of the own vehicle detected by the own vehicle speed detection means. The reference peak frequency corresponding to the relative velocity is obtained, the detected peak frequency is compared with the reference peak frequency, and if there is a peak frequency corresponding to the reference peak frequency among the detected peak frequencies, the object detecting means It may be determined that another vehicle is detected as an object.</p><p num="0010"> In the above configuration, the determination means obtains a reference peak frequency corresponding to the reference distance and the reference relative velocity, and directly compares the detected peak frequency with the reference peak frequency. Therefore, the search for the peak frequency corresponding to the reference peak frequency becomes easy, and the calculation load of the object detection device is reduced.</p><p num="0011"> Further, when the determination means determines that the object detection means has detected another vehicle as an object, the object information calculation means may correct the distance between the other object and the own vehicle by using the reference distance.</p><p num="0012"> In the above configuration, the distance between the other object and the own vehicle is corrected by using the reference distance calculated by using the position information of the other vehicle and the own vehicle with relatively high accuracy. Therefore, the accuracy of detecting the distance between another object and the own vehicle is improved.</p><p num="0013"> Further, the other vehicle information acquisition means may acquire the position of the other vehicle by at least one of vehicle-to-vehicle communication or road-to-vehicle communication.</p><p num="0014"> In the above configuration, the other vehicle information acquisition means acquires the position of the other vehicle by the standardized communication means of vehicle-to-vehicle communication and road-to-vehicle communication. Therefore, it is possible to design the device according to the standard, reduce the development cost, and shorten the development period.</p>

<p num="0015"> According to the present invention, it is possible to prevent a decrease in the detection accuracy of the object detection device of the vehicle, reduce erroneous detection, and improve the recognition accuracy of the object.</p>

<figref num="1">It is a block diagram which shows the main part of the vehicle which carries the driving support device using the object detection device of this invention.</figref><figref num="2">It is a schematic diagram which shows the object detection state of the millimeter wave radar sensor of FIG.</figref><figref num="3">It is a waveform diagram of the transmitted wave and the reflected wave of a millimeter wave radar sensor.</figref><figref num="4">It is a figure which shows the result of the frequency analysis when one object is detected.</figref><figref num="5">It is a figure which shows the result of the frequency analysis at the time of detecting a plurality of objects.</figref><figref num="6">It is a schematic diagram which shows the method of searching the peak frequency using a reference distance and a reference frequency.</figref>

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, the vehicle 1 according to the present embodiment includes a millimeter-wave radar sensor (object detecting means) 4, a vehicle position sensor (vehicle position detecting means) 5, and a vehicle speed sensor (vehicle speed detecting 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 transmitted wave, which is a continuous electromagnetic wave (FM-CW) in the millimeter-wave band subjected to triangular wave frequency modulation, within a predetermined angle in the traveling direction from the front end of the vehicle 1. It fires at regular intervals, receives a received wave that is a reflected wave from the object 2 existing in front of the vehicle 1, and detects the object 2 (see FIG. 2). Subsequently, a beat signal is generated by mixing the transmitted wave and the received wave, and the generated beat signal is frequency-analyzed by a fast Fourier transform (FFT).

Here, since the received wave from the object 2 has a time delay due to the reciprocating distance L between the object 2 and the vehicle 1 with respect to the transmitted wave (see FIG. 3), the beat signal is frequency-analyzed. The beat signals in the ascending section (up side) and descending section (down side) of the frequency modulation by the triangular wave include peak frequencies Fu (up side) and Fd (down) having a peak at the beat frequency Fl corresponding to the distance L. Sides) occur respectively.

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), so that the peak frequency of the beat signal on the up side is generated. The frequency of Fu decreases by the beat frequency Fv corresponding to the relative velocity V from the beat frequency Fl when the relative velocity is zero. 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 objects 2 are generated in the beat signals on the up side and the down side, respectively. FIG. 5 shows a case where three objects 2 are detected. The 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 frequency Fu and 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 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 at predetermined time intervals and outputs it to the CPU 10.

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

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 the switch (not shown) of the driving support device is turned on, the CPU 10 executes these processes at predetermined time intervals.

The other vehicle information calculation processing unit 11 includes 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 the reference distance Lr, which is the distance between the other vehicle 3 and the vehicle 1, and the reference relative speed Vr, which is the relative distance between the other vehicle 3 and the vehicle 1, are calculated.

The determination processing unit 12 determines whether or not the millimeter-wave radar sensor 4 has detected the other vehicle 3 for which the reference distance Lr and the reference relative velocity Vr with respect to the vehicle 1 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 velocity Vr calculated by the other vehicle information calculation processing unit 11 into the equations (2) and (5), and then the equations (3) and (3). Using 4), the peak frequency Fur of the beat signal on the up side and the peak frequency Fdr of the beat signal on the down side, which are the 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 has a difference from Fur within a predetermined range among the plurality of peak frequencies on the up side of the plurality of objects 2 detected by the millimeter wave radar sensor 4. The presence or absence of the peak frequency Fu of a certain object 2 is searched. Similarly, the presence or absence of the peak frequency Fd whose difference from the Fdr is within a predetermined range is searched for in the peak frequency on the down side. In the example shown in FIG. 6, among the peak frequencies Fu1 to Fu3 and Fd1 to Fd3 of the three detected objects 2, the pair of the peak frequencies of Fu2 and Fd2 is searched as the peak frequency corresponding to the reference peak frequencies Fur and Fdr. Will be done. When the pair of the 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 another vehicle 3. If the peak frequency pair whose difference between Fur and Fdr is within a predetermined range cannot be searched for in the peak frequency, the millimeter wave radar sensor 4 has a reference distance Lr and a reference relative velocity Vr. It is probable that it could not be detected. For example, there may be a case where a small vehicle is traveling in front of a large vehicle and it is difficult for the transmitted wave from the millimeter wave radar sensor 4 to reach.

The object information calculation processing unit 13 combines the peak frequency Fu on the up side and the peak frequency Fd on the down side of the plurality of objects 2 detected by the millimeter wave radar sensor 4 to form the object 2 and the vehicle 1, respectively. Calculate the distance L and the relative velocity V. Specifically, first, for the object 2 determined to be another vehicle 3 by the determination processing unit 12, the peak frequencies Fu and Fd in which the difference between the reference peak frequencies Fur and Fdr are within a predetermined range are determined. 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 in which the difference between the reference peak frequencies Fur and Fdr is within the predetermined range from the peak frequencies. Using the remaining peak frequencies excluding the combination of Fu and Fd, the peak frequency Fu on the up side and the peak frequency Fd on the down side 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, Fu1, Fu3 and Fd1, Fd3 are combined, 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 velocity V between all the detected objects 2 and the vehicle 1 are calculated.

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

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

The collision prevention control unit 14 calculates the 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 velocity V. When the TTC of the object 2 having the shortest TTC becomes less than or equal to the first predetermined time (for example, 3 seconds), it is output to the alarm device 8 to alert the driver. Further, when the TTC becomes the second predetermined time (for example, 0.8 seconds) or less, the brake actuator 9 is operated to decelerate the vehicle 1 and avoid a collision with the object 2.

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

Further, when the peak frequencies corresponding to the reference peak frequencies Fur and Fdr can be searched, the object information calculation processing unit 13 uses the peak frequencies Fu and Fd excluding the combination of the peak frequencies corresponding to the reference peak frequencies to obtain the other vehicle. The distance L and the relative distance V of the other object 2 excluding the object 2 determined to be 3 are calculated. Therefore, as shown in the example shown in FIG. 6, since the number of peak frequencies used for the calculation is reduced, the accuracy of the calculation is improved, and it is possible to prevent a decrease in detection accuracy and erroneous detection due to the combination of erroneous peak frequencies. ..

Further, even if the peak frequency corresponding to the reference distance Lr and the reference relative velocity Vr cannot be searched, that is, even if the millimeter wave radar sensor 4 cannot detect the object 2 determined to be the other vehicle 3, the other vehicle information. Since the information of the reference distance Lr and the reference relative velocity Vr of the other vehicle 3 and the vehicle 1 obtained by the arithmetic processing unit 11 can be acquired, the undetection of 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 relatively accurate because they are based on the position information obtained by GPS positioning and the speed information of the vehicle sensor or the like. Is high. Therefore, the distance L and the relative velocity V between the object 2 and the vehicle 1 detected by the millimeter-wave radar sensor 4 are used as the measured values, and the reference distance Lr and the reference relative velocity Vr are used as the measured values for the object 2 determined to be another vehicle 3. Further, for the other object 2, the calculated values of the distance L and the relative velocity V between the other object 2 and the vehicle 1 are corrected using the reference distance Lr and the reference relative velocity Vr as reference values to obtain the measured values. Therefore, the accuracy of the measured value of the millimeter wave radar sensor 4 can be improved.

As described above, according to the present embodiment, the recognition accuracy and the measurement accuracy of the object 2 detected by the millimeter wave radar sensor 4 are improved, and false detection and undetection are reduced, so that the operation caused by the incorrect object information is performed. It is possible to reduce false alarms and malfunctions of the support device.

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

Further, since the information on 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 for 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 or not the detected object 2 is another vehicle 3. May be determined. In this case, since the reference relative velocity 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 velocity is increased or decreased around Fr. Create a combination of peak frequencies of Fr-Δf and Fr + Δf. Next, while increasing Δf from zero, the 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 for. When the combination of the peak frequencies of the object 2 can be searched within a predetermined range, it can be determined that the object 2 corresponding to the peak frequency is another vehicle 3.

Further, the object information calculation processing unit 13 stores the calculated distance L and relative velocity V of the object 2 as time series data, and uses them when combining the peak frequencies Fu and Fd of the object 2 detected this time. May be good. By estimating and referring to the distance and relative velocity of the object 2 detected this time using the distance and relative velocity of the object 2 stored in the time series data before the previous time, the peak frequencies Fu and Fd are more accurate. Combination is possible.

Further, the object detection means is not limited to the millimeter wave radar of the present embodiment, and is, for example, an image sensor or the like that captures 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. You may. That is, the determination processing unit 12 includes at least one of the distance L and the relative velocity V between the plurality of objects 2 and the vehicle 1 detected by the image sensor, and the other vehicle 3 and the vehicle calculated by the other vehicle information calculation processing unit 11. By comparing at least one of the reference distance Lr and the reference relative velocity Vr with 1, the object 2 corresponding to the reference distance Lr can be determined to be another vehicle 3. Therefore, it is possible to reliably recognize that the determined object 2 is another vehicle 3. Further, the reference distance Lr is used as the 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 the reference value to obtain the measured value. The accuracy of the measured value of the sensor can be improved.

Further, in the present embodiment, one CPU 10 executes the detection of the object 2 and the collision prevention control process, but the processing device that executes the detection of the object 2 and the processing device that executes the collision prevention control are different. It may be configured as a separate unit. Therefore, for the existing vehicle 1 provided with the device for executing the collision prevention control process, a device (unit) for executing the detection of the object 2 may be additionally installed, and the existing vehicle 1 may be provided with the device (unit). On the other hand, the present invention can be easily applied.

Although the embodiment to which the invention made by the present inventor is applied has been described above, the present invention is not limited by the essay and the drawings which form a part of the disclosure of the present invention according to this embodiment. That is, it goes without saying that all other embodiments, examples, operational techniques, and the like made by those skilled in the art based on this embodiment are included in the category of the present invention.

The present invention is widely applicable to a vehicle driving support device.

1 vehicle 2 object 3 Other vehicles 4 mm wave radar sensor 5 Own vehicle position sensor 6 Own vehicle speed sensor 7 Communication equipment 10 CPU 11 Other vehicle information calculation processing unit 12 Judgment processing unit 13 Object information calculation processing unit