JP2009288098A - Physical object detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a physical object detector for accurately determining whether an object is a vehicle or not in a case where three or more peaks exist of reflection intensity. <P>SOLUTION: In a case where three or more peaks exist of reflection intensity, a control circuit 11 extracts top three peaks in order of decreasing reflection intensity. Whether the physical object is a vehicle or not is determined based on two peaks at both ends among these three peaks and on the lowest intensity of hollows between these two peaks. Further, in cases where the intensity of the hollows are to some extent low as against the intensity of the peaks, the object is determined to be a stopped vehicle. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an object detection device that scans an electromagnetic wave such as a laser beam as an exploration wave and determines whether or not the object is a vehicle.

  2. Description of the Related Art Conventionally, there is an apparatus that measures whether or not an object is a vehicle and measures the distance to the object by irradiating the front of the vehicle with electromagnetic waves such as laser light and millimeter waves. Using this device, a distance between the preceding vehicle is measured, and a constant inter-vehicle distance following traveling (ACC: Adaptive Cruise Control) is performed to keep the inter-vehicle distance constant. In addition, safety control is performed such that a warning sound is emitted to the driver, the seat belt is tightened, and braking is performed when the inter-vehicle distance is equal to or less than a safe distance.

  The preceding vehicle that performs the control as described above is limited to a case where the vehicle is moving or stopped from a moving state. However, an attempt is also made to target a vehicle that has already stopped at the time of detection. ing. When control such as braking is performed assuming that an object that has already stopped at the time of detection is a vehicle, roadside structures (guardrail reflectors, etc.) and reflectors embedded in the road surface (white lines) are used to prevent malfunctions. It is necessary to distinguish between vehicles and sidewalks) and vehicles.

  Here, an object detection method will be described. The laser radar device scans the laser beam and detects the reflection intensity of the reflected wave due to the laser beam being applied to the object for each predetermined scanning direction. Then, a horizontal distribution of the reflection intensity of the reflected wave is created, and a point (peak) where the reflection intensity is maximized is extracted.

  For example, Patent Document 1 proposes an apparatus that determines whether an object is a vehicle based on a horizontal distribution of reflection intensity. In the apparatus of Patent Document 1, when two peaks exist in the horizontal distribution of reflection intensity, it is determined that the object is a vehicle.

  Japanese Patent Application Laid-Open No. H10-228561 shows that whether an object is a four-wheeled vehicle or a two-wheeled vehicle is determined based on a reflection intensity pattern. In the apparatus of Patent Document 2, it is determined whether the vehicle is a four-wheeled vehicle or a two-wheeled vehicle based on the number of peaks.

  Patent Document 3 discloses a technique for detecting the center position of an object based on a plurality of peaks. The apparatus of Patent Document 3 detects the center position of an object based on the peak shape. For example, when the reflection intensity has one peak, the angle of the peak is detected as the center position of the object. When there are multiple peaks and the number of peaks formed by these multiple peaks is one, the peak heights of the three peaks including the highest intensity peak and the peaks on both sides of the peaks are balanced. The angle to be detected is detected from the center position of the object. Furthermore, when there are a plurality of peaks and the number of peaks formed by the plurality of peaks is a plurality, the center of the peak angle at both ends is detected as the center position of the object.

Usually, one reflector is provided at each end of the vehicle. In addition to these reflectors, some have a reflector provided in the center of the vehicle. In addition, a license plate is attached to the center of the vehicle as an object having high reflectance such as light.
JP 2006-38698 A JP 2006-38697 A JP 2000-180532 A

  An object of the present invention is to provide an object detection apparatus that can accurately determine whether or not an object is a vehicle when there are three or more reflection intensity peaks.

  The present invention relates to an irradiating means for irradiating an exploration wave, a scanning means for scanning the exploration wave in a horizontal direction, and a reflected wave detecting means for detecting the reflection intensity of the reflected wave due to the exploration wave being applied to an object. Scanning direction detecting means for detecting the scanning direction of the scanning means, required time measuring means for measuring a required time from irradiation of the exploration wave to detection of the reflected wave, the reflection intensity, An object detection device comprising: a target detection unit configured to detect a distance to the target object and a direction of the target object based on a scanning direction and the required time, wherein the reflection intensity, the scanning direction, and A width detection unit that detects a width of the object based on the required time, and a vehicle determination unit that determines whether or not the object is a vehicle.

  When there are two reflection intensity peaks in the width, the vehicle determination means determines whether or not the object is a vehicle based on the intensity of the recess between these two peaks and the two peaks. If there are three reflection intensity peaks within the width, whether or not the object is a vehicle based on the minimum intensity of the two peaks at both ends and the depression between the two peaks. Determine. Thus, since vehicle determination is performed based on the intensity | strength of the hollow which shows two peaks on both ends and the minimum intensity | strength, it can be determined accurately whether a target object is a vehicle.

  In addition, when there are four or more reflection intensity peaks within the width, the vehicle determination means selects the top three peaks of the reflection intensity, out of these three peaks, two peaks at both ends, and both ends 2 It is characterized by determining whether the said target object is a vehicle based on the minimum intensity | strength among the hollows between two peaks.

  In this case, since the top three peaks of the reflection intensity are selected and the vehicle determination is performed based on the two peaks at both ends and the intensity of the depression indicating the minimum intensity, it is possible to accurately determine whether the object is a vehicle. it can.

  Further, it is desirable that the vehicle determining means further determines whether or not the object is a vehicle based on the strength of the dent and the strength of the peak.

  For example, the vehicle is determined to be a vehicle when the strength of the dent is somewhat reduced with respect to the peak strength. In a signboard or the like having the same width as that of a vehicle, the depression of the dent strength is small with respect to the peak strength. Therefore, it can be accurately determined whether the vehicle is a vehicle.

  According to the present invention, it can be accurately determined whether or not the object is a vehicle.

FIG. 1 is a block diagram of a laser radar apparatus according to an embodiment of the present invention.
The laser radar device of the present embodiment includes an LD (Laser Diode) drive circuit 10, a control circuit 11, an LD 12, a scanning device 13, a vertical scanning position detection device 14, a horizontal scanning position detection device 15, a PD (Photo Diode) 16, and light reception. A circuit 17, a memory 18, a vehicle speed sensor 19, and a yaw rate sensor 20 are provided.

  The LD drive circuit 10 controls the light emission of the LD 12 based on the drive signal generated by the control circuit 11. The scanning device 13 scans the laser beam generated by the LD 12 in a predetermined scanning range based on the control of the control circuit 11. The laser beam emitted from the scanning device 13 is emitted in the traveling direction (front) of the host vehicle through the light projecting lens. The reflected light that is reflected by the laser beam reflected on the front object (for example, vehicle or road surface) as the detection target is collected by the light receiving lens and received by the PD 16.

  FIG. 2 is a diagram illustrating a configuration of a portion that supports the light projecting lens and the light receiving lens of the scanning device 13. The light projecting lens 33 is provided on the front surface of the LD 12, and the light receiving lens 34 is provided on the front surface of the PD 16.

  The light projecting lens 33 and the light receiving lens 34 are integrally supported by a support member 36. The support member 36 is supported by a leaf spring 32 so as to be movable in the horizontal direction. A coil 31 is attached to the support member 36. The scanning device 13 moves the light projecting lens 33 of the LD 12 and the light receiving lens 34 of the PD 16 by the attractive force (or repulsive force) between the magnetic field generated in the coil 31 and the permanent magnet 35 and the reaction force generated in the leaf spring 32. Laser light is scanned.

  FIG. 3 is a diagram showing optical paths of the light projecting lens 33 and the light receiving lens 34. The laser light emitted from the LD 12 is collected by the light projection lens 33. When the position of the light projection lens 33 is in the neutral position of scanning, the laser light is irradiated to the front along the optical path from the light projection lens 33 as indicated by the solid line in FIG. The irradiated laser light is reflected by the object, enters the light receiving lens 34 through an optical path as indicated by a solid line in FIG. 3, and is received by the PD 16.

  Further, when the light projection lens 33 is moved upward in the figure by the scanning device 13, the laser beam is irradiated upward in the figure along the optical path as indicated by the dotted line in FIG. The irradiated laser light is reflected by an object in the upward direction in the drawing, enters the light receiving lens 34 through an optical path as indicated by a dotted line in FIG. 3, and is received by the PD 16.

  As described above, the scanning device 13 scans the laser light by moving the light projecting lens 33 and the light receiving lens 34 integrally to a predetermined position. In the above description, scanning in the horizontal direction has been described, but laser light can also be scanned in the same manner in the vertical direction.

  In FIG. 1, a vertical scanning position detection device 14 and a horizontal scanning position detection device 15 detect the scanning directions of the laser beam in the scanning device 13 in the horizontal direction and the vertical direction, respectively, and output them to the control circuit 11. Note that the vertical direction is not essential as a component of the present invention, and scanning may be performed only in the horizontal direction and only the horizontal scanning direction may be detected.

  A signal corresponding to the reflection intensity of the reflected light received by the PD 16 is input to the light receiving circuit 17. The light receiving circuit 17 digitizes the reflection intensity and outputs it to the control circuit 11. The control circuit 11 stores the input numerical value in the memory 18 corresponding to the scanning direction input from the vertical scanning position detection device 14 and the horizontal scanning position detection device 15. Such measurement of the reflection intensity is performed each time the scanning device scans in a predetermined scanning direction. At this time, the laser beam is scanned by a predetermined angle. An area where the laser radar device irradiates laser light at a predetermined angle and detects an object is referred to as a “predetermined area”.

  A vehicle speed sensor 19 and a yaw rate sensor 20 are connected to the control circuit 11. The vehicle speed sensor 19 detects the vehicle speed of the own vehicle. The yaw rate sensor 20 detects the yaw rate (turning speed when turning in the horizontal direction) of the host vehicle.

  The control circuit 11 measures the distance between the object and the own vehicle based on the required time from when the laser beam is irradiated until the reflected light is received. The distance is measured for each predetermined area. The control circuit 11 collects a set of objects whose distances and scanning directions are close to each other and makes the same object. The control circuit 11 determines whether the set of objects is a vehicle based on the reflection intensity, the scanning direction, and the required time (distance).

Hereinafter, a specific procedure for determining whether or not the vehicle is a vehicle will be described.
FIG. 4 is a flowchart showing the overall procedure.
The control circuit 11 measures the reflection intensity for each predetermined area as described above (s1). When the entire scanning range is measured (s2), a collection of objects whose distances and scanning directions are close are collected (s3). Next, the distance, direction, and width of each object are calculated (s4).

  FIG. 5 is a diagram showing an object and width detection method. The graph in the upper column of the figure is a horizontal distribution showing the distance to the object in the entire scanning range. As shown in the graph in the upper column of the figure, the control circuit 11 collects a set of objects whose distances and scanning directions are close to each other and sets them as the same object (objects M1 and M2 in the figure). The control circuit 11 creates a horizontal distribution of the reflection intensity of each object and extracts a point (peak) where the reflection intensity is maximum, as shown in the graph in the lower column of FIG. The control circuit 11 reads out the distance and direction at each extracted peak, and uses these average values as the distance and direction of the object. Also, areas where the reflection intensity is a predetermined multiple (for example, 0.5 times) with respect to the peaks at both ends (peak 1 and peak 2 in the figure) are extracted, and the width of the object is set with these areas as the edges of the object. To detect.

  In FIG. 4, after detecting the distance, direction and width of the object, the control circuit 11 determines whether or not the detected object is a stopped vehicle (s5). FIG. 6 is a flowchart illustrating the procedure of the stopped vehicle determination process. This process is performed for each detected object.

  The control circuit 11 first investigates the reflection intensity of each area constituting the object (s11). That is, a horizontal distribution of the reflection intensity of each object shown in the graph in the lower column of FIG. 5 is created. Further, the relative speed is calculated by referring to the time-axis change of the distance in each region. The time axis change is obtained by the difference between the distance measured in the current scan in the current scan and the distance measured in the previous scan. The control circuit 11 determines whether the object is a stop based on the relative speed (s12). If the object approaches at the same relative speed as the vehicle speed of the host vehicle, it is determined that the object is a stop. In other cases (in the case of a moving object), the stop vehicle determination flag is set to FALSE.

  If it is a stationary object, it is determined whether there is a peak in the horizontal distribution of the reflection intensity (s13). If there is a peak, the area and the reflection intensity are recorded in the peak list (s14). As shown in FIG. 7, the peak list is a list of region numbers (for example, A1, A2, A3... An in order from the left end in the horizontal direction) and the reflection intensity.

  Thereafter, the process is repeated until the investigation of all areas is completed. When the investigation of all areas is completed (s15), it is determined whether or not the number of stored peak lists (number of peaks) is 2 or more (s16). . If there is no peak or the number of peaks is 1, the stop vehicle determination flag is set to FALSE (s28).

  If the number of peaks is 2 or more, it is further determined whether or not the number of peaks is 3 or more (s17). If it is determined that the number of peaks is two, the left end peak and the right end peak are determined (s18). That is, the peak existing on the left side is the left end peak, and the peak existing on the right side is the right end peak. And based on the intensity | strength of the hollow between a left end peak and a right end peak, it is determined whether the detected object is a stop vehicle (S19).

  On the other hand, if it is determined that the number of peaks is three or more, the top three peaks are extracted in descending order of reflection intensity (s20). Then, among the top three, the left peak is the left peak and the right peak is the right peak (s21).

  Further, after determining the left end peak and the right end peak, the control circuit 11 investigates a recess having the lowest intensity among these peaks (s22). The control circuit 11 determines whether or not the detected object is a stopped vehicle based on the left end peak, the right end peak, and the strength of the depression.

  With reference to FIG. 9 and FIG. 10, the case where the number of peaks is 2 and 3 will be described. FIG. 9 shows the reflection intensity when the number of peaks is two, and FIG. 10 shows the reflection intensity when the number of peaks is three. As shown in the lower column of FIG. 9, when the vehicle ahead is located far away, a high reflection intensity can be obtained mainly from the reflector. Since two reflectors are provided at the left and right ends of the vehicle, the number of reflection intensity peaks is two as shown in the graph in the upper column of FIG. On the other hand, as shown in the lower column of FIG. 10, when the vehicle ahead is present at a short distance, high reflection intensity can be obtained not only from the reflector but also from the number plate provided at the center of the vehicle. As a result, the number of reflection intensity peaks is three as shown in the upper graph of FIG.

  In the present embodiment, as shown in FIG. 10, even when there are three peaks, the left end peak and the right end peak are determined, the object width and the like are calculated, and the vehicle determination is performed. Can be determined whether or not the object is a vehicle even if it is attached to the center of the vehicle or a high reflection intensity is obtained from the license plate. Even if there are four or more peaks, the top three peaks with the highest reflection intensity are extracted to determine the left and right peaks, and the vehicle width is determined by calculating the object width and the like. Even if the vehicle is equipped with a larger number of reflectors, it can be determined whether or not the object is a vehicle.

The control circuit 11 performs the following vehicle determination process based on these investigation results. That is, in the processing of s23 to s26 of FIG. 6, it is determined that the vehicle is a stopped vehicle only when all the following conditions are satisfied, and the stopped vehicle determination flag is set to TRUE (s27). On the other hand, if any one of the conditions is not satisfied, the stop vehicle determination flag is set to FALSE (s28).
(S23) Wmin <object width W <Wmax
(S24) Spreading width Ws <Ws_max
(S25) Wp_min <left and right end peak width Wp <Wp_max
(S26) Indentation reflection intensity A_HOL <A_P1 × αph
Here, various values will be described with reference to FIG. FIG. 8 is a diagram illustrating definitions of various values such as the object width.
The object width W is obtained from the width between regions that is a predetermined multiple (A_P1 × αp and A_P2 × αp, where αp = 0.5) of the reflection intensity of the left end peak and the right end peak. In the present embodiment, when the object width is within a range that can be determined as a vehicle (for example, Wmin = 1.0 [m], Wmax = 3.5 [m]), it is determined as a vehicle.

  The spread width Ws is calculated from a reference intensity that is a predetermined multiple of the hollow reflection intensity A_HOL (A_HOL × αh, where αh = 0.5), and from the left and right end peaks to the object end (left and right sides of the left and right end peaks). The area corresponding to this reference intensity (left reference direction and right reference direction) is determined toward the base, and is determined from the width between these reference directions. When the spread width Ws falls within a predetermined width Ws_max (for example, 5.0 [m]) that can be determined as a vehicle, it is determined that the vehicle seems to be a vehicle.

  The spread width will be described with reference to FIGS. 9 and 11. FIG. 11 is a diagram showing the reflection intensity when a guardrail is present in front. As shown in the lower column of the figure, the guardrail is provided with a reflector, and two peaks are detected at the same distance as that of the preceding vehicle shown in FIG.

  As shown in FIG. 9, when the detected object is a vehicle, the outside of the vehicle width (outside of the reflector) has no reflector, so the drop in reflection intensity is large and the spread width Ws is small. On the other hand, as shown in FIG. 11, when the detected object is a guard rail, the guard rail also extends outside the reflector, so that a reflection intensity comparable to the depression reflection intensity is widely detected, and the drop in the reflection intensity is small and widened. The width Ws is increased. Therefore, when the spread width Ws is extremely larger than the object width W (for example, 5 m or more), it is determined that the vehicle is not a vehicle.

  Next, as described above, the width Wp between the left and right end peaks is obtained from the widths of the left end peak and the right end peak. If this left-right peak-to-peak width Wp is within a range (for example, W_pmin = 0.5 [m], Wp_max = 3.5 [m]) that can be determined as the width of the reflector of the vehicle, it is determined that the vehicle seems to be. is there.

  Next, the depression reflection intensity A_HOL is the reflection intensity of a region (depression) having the lowest intensity between the left end peak and the right end peak. Whether or not the depression reflection intensity A_HOL has fallen to some extent with respect to the peak having the maximum intensity (for example, A_HOL <A_P1 × αph, where αph = 0.5) is determined.

  The hollow reflection intensity will be described with reference to FIGS. 10 and 12. FIG. 12 is a diagram showing the reflection intensity when a signboard having the same width as that of the vehicle is installed in front. As shown in the lower column of the figure, the signboard has three symbols showing high reflection intensity, and there are three peaks at the same distance as the reflector and license plate of the preceding vehicle shown in FIG.

  As shown in FIG. 10, when the detected object is a vehicle, there is nothing between the reflector and the license plate that shows high reflection intensity, and the reflection intensity of the dent greatly falls from the peak of maximum intensity (A_HOL < A_P1 × αph). However, as shown in FIG. 12, when the detected object is a signboard, a certain degree of reflection intensity is obtained even between symbols with high reflection intensity, so that the drop in the reflection intensity of the depression is small (A_HOL ≧ A_P1 × αph). ). Therefore, it can be accurately determined whether or not the vehicle is a vehicle.

  In addition, as shown in FIG. 13, white lines and sidewalks have a width larger than that of the vehicle, a wide reflection intensity similar to the reflection intensity of the dent, or a certain degree of reflection intensity between the reflectors. Since it exists, it shows the reflection intensity as shown in FIG. 11 and FIG. 12, and can be distinguished from a stopped vehicle.

  The stop vehicle determination process as described above is performed, and the determination result is output to another device such as a vehicle control unit (s6 in FIG. 4). The vehicle control unit performs safety control such as issuing a warning sound to the driver, tightening the seat belt, or performing braking using the determination result.

  In addition, although this embodiment demonstrated the laser radar apparatus, this invention is applicable to apparatuses using various electromagnetic waves, such as a millimeter wave radar. The millimeter wave radar mechanically scans electromagnetic waves (millimeter waves) and detects the reflection intensity for each predetermined angle. There is also a millimeter wave radar that detects the reflection intensity for each predetermined angle based on the phase difference of reflected waves detected by a plurality of receivers. In any case, the distance to the object is calculated based on the required time from the transmission of the millimeter wave to the reception of the reflected wave, and the direction of the object is calculated based on the reflection intensity and the scanning angle (scanning direction). Is. Further, the relative velocity is detected using the Doppler effect of the reflected wave. Therefore, the stop vehicle of the present invention detects the width of the object based on the required time, the reflection intensity, and the scanning direction, and determines whether the object is a vehicle based on the horizontal distribution (peak or depression) of the reflection intensity. It is possible to apply a determination process.

It is a block diagram which shows the structure of the laser radar apparatus which is embodiment of this invention. It is a figure which shows the structure of the part which supports the light projection lens and light receiving lens of a scanning device. It is a figure which shows the optical path of the light projection lens and the light reception lens which were driven by the scanning apparatus. It is a flowchart which shows the whole procedure. It is the figure which showed the method of the detection of an object and the detection of a width | variety. It is a flowchart which shows the procedure of a vehicle determination process. It is a figure which shows a peak list. It is a figure which shows the definition of various values. It is a figure which shows the reflection intensity about the case where the number of peaks is two. It is a figure which shows the reflection intensity about the case where the number of peaks is three. It is a figure which shows the reflection intensity when a guardrail exists ahead. It is a figure which shows the reflection intensity when the signboard which has a width | variety comparable as a vehicle is installed ahead. It is a figure which shows the case where a white line, a sidewalk, etc. exist.

Claims (3)

An irradiation means for irradiating the exploration wave;
Scanning means for scanning the exploration wave in a horizontal direction;
Reflected wave detection means for detecting the reflected intensity of the reflected wave caused by the object being irradiated with the exploration wave;
A scanning direction detecting means for detecting a scanning direction of the scanning means;
A required time measuring means for measuring a required time from irradiating the exploration wave to detecting the reflected wave;
Object detection means for detecting a distance to the object and a direction of the object based on the reflection intensity, the scanning direction, and the required time;
In an object detection apparatus comprising:
Width detecting means for detecting the width of the object based on the reflection intensity, the scanning direction, and the required time;
When two reflection intensity peaks exist within the width, it is determined whether or not the object is a vehicle based on the intensity of the depression between the two peaks and the two peaks,
When there are three reflection intensity peaks within the width, it is determined whether the object is a vehicle based on the minimum intensity of the two peaks at both ends and the depression between the two peaks. Vehicle determination means for
An object detection apparatus comprising:   When there are four or more reflection intensity peaks within the width, the vehicle determination means selects the top three peaks of the reflection intensity, and among these three peaks, the two peaks at both ends and the interval between the two peaks at both ends The object detection device according to claim 1, wherein whether or not the object is a vehicle is determined based on a minimum strength among the depressions.   3. The object according to claim 1, wherein the vehicle determination unit further determines whether the object is a vehicle based on the strength of a depression and the intensity of a peak. Detection device.

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