Abstract:
A vehicle mounted radar device operable to scan a transmission wave to detect a detection point representing a position of an object disposed around the vehicle on the basis of a reflected wave of the transmission wave from the object. The radar device includes a reading unit, a continuity determination unit, a setting unit, anti an object determination unit that are configured to prevent the radar device from erroneously determining different pieces of object information as a single object.

Description:
The disclosure of Japanese Patent Application No. 2010-036989 filed on Feb. 23, 2010, including specification, drawings and claims is incorporated herein by reference in its entirety. 
     BACKGROUND 
     The present invention relates to a technique for preventing a radar device from erroneously determining different pieces of object information as a single object. 
     In general, a radar device which is mounted in a vehicle continuously scans the periphery of the vehicle, when the same object has been detected multiple times, outputs object information (for example, the relative distance between the vehicle and the object, the relative speed, the lateral distance (angle), and the like) to a vehicle control section in accordance with the positional relationship between the object which has been detected multiple times and the host vehicle, and performs vehicle control (warning, brake, seat belt tightening, or the like). 
     In performing continuous scanning, with regard to a newly detected object, when the object is continuously detected a predetermined number of times or more, object information is output to the vehicle control section. That is, when the object is detected once only in scanning, object information is not output to the vehicle control section. When the object is detected multiple times, processing is performed in which changes in the positional relationship between the object and the host vehicle are calculated, and if the conditions for the output to the vehicle control section are satisfied, the object information of the target object is output to the vehicle control section. 
     The detection of an object is done on the basis of a signal which is received as a received wave by the radar device when a transmission wave from the radar device is reflected from the object. The radar device may receive a plurality of reflected waves from a single object. In this case, a signal processing section of the radar device sets a reflection point at the closest relative distance from the host vehicle as a representative detection point, and determines all of detection points within a predetermined distance range (coupling range) from the representative detection point as a single object. The object information is output from the radar device to the vehicle control section. 
     When a representative detection point which has been detected once is not detected in subsequent scanning, if there is a detection point second-closest to the host vehicle next to the representative detection point which has not been detected in current scanning, from among the detection points within the coupling range previously detected, the detection point is set as a new representative detection point, the coupling range is again set on the basis of the new representative detection point, and processing is performed assuming that the same object is continuously detected after previous scanning. JP-A-2006-38755 describes a technique related to the present invention. 
     However, when a coupling range is provided and a plurality of detection points are determined to be a single object, even though detection points of different objects fall within a single coupling range, it may be determined to be the detection points of a single object. For example, when a vehicle is traveling by closely following another vehicle, all reflection points of different vehicles may be determined as a single object. 
     For this reason, when a representative detection point which has been detected in past scanning is not detected in subsequent scanning, or when a detection point second-closest to the host vehicle next to the representative detection point which has not been detected, from among the detection points within the coupling range in past scanning is a detection point of another vehicle different from the vehicle which has previously been detected, the detection point of another vehicle may be erroneously set as a new representative detection point of the same vehicle which has previously been detected. In this case, the set representative detection point is intrinsically a detection point of a vehicle which is newly detected. In the vehicle control section to which object information is output, if an object is not detected as the same object multiple times, the object is not subjected to vehicle control, thus the object information of the representative detection point will not be subjected to vehicle control intrinsically. For this reason, the radar device erroneously recognizes different objects as a single object, such that the vehicle control section performs vehicle control on the basis of object information which is not intrinsically subjected to vehicle control, causing erroneous vehicle control. 
     SUMMARY 
     It is therefore an object of at least one embodiment of the present invention to provide a technique for preventing a radar device from erroneously determining different pieces of object information as a single object. 
     In order to achieve at least one of the above-described objects, according to a first aspect of the embodiments of the present invention, there is provided a radar device which is mounted on a vehicle and is operable to scan a transmission wave to detect a detection point representing a position of an object disposed around the vehicle on the basis of a reflected wave of the transmission wave from the object, the radar device comprising: a reading unit that reads information of detection points from a memory which stores the information of the detection points including a first representative detection point closest to the vehicle, which are detected in first scanning; a continuity determination unit that determines whether or not the detection points of the read information are continuously detected in second scanning after the first scanning; a setting unit that sets one of the detection points second-closest to the vehicle next to the first representative detection point from among detection points disposed within a predetermined range from the first representative detection point in the first scanning as a second representative detection point in the second scanning when the first representative detection point is not detected in the second scanning; and an object determination unit that determines the first representative detection point and the second representative detection point are information of different objects when the second representative detection point exists at a position distant from a position of the first representative detection point by equal to or more than a predetermined distance. 
     According to the first aspect, when the second representative detection point exists at a position distant from the position of the first representative detection point by equal to or more than a predetermined distance, it is determined that the first representative detection point and the second representative detection point are information of different objects. Therefore, it is possible to prevent different objects from being erroneously determined as a single object. 
     In the radar device according to the first aspect of the embodiments of the present invention, the object determination unit may determine that the first representative detection point and the second representative detection point are information of an object when the second representative detection point exists at a position distant from the position of the first representative detection point by less than the predetermined distance. 
     With this configuration, when the second representative detection point exists at a position distant from the position of the first representative detection point by less than a predetermined distance, it is determined that the first representative detection point and the second representative detection point are information of the same object. Therefore, it is possible to correctly determine the same object as a single object. 
     In the radar device according to the first aspect of the embodiments of the present invention, the object determination unit may determine that the first representative detection point and the second representative detection point are information of an object when the second representative detection point exists at a position close to the vehicle from the position of the first representative detection point. 
     With this configuration, when the second representative detection point exists at a position close to the vehicle from the position of the first representative detection point, it is determined that the first representative detection point and the second representative detection point are information of the same object. Therefore, when a detection point which is newly detected is a detection point from the same object which has not been detected in past scanning, it is possible to correctly recognize the same object as a single object. 
     The radar device described above may further comprising an information transmission unit that, when a comparison result of a position of the first representative detection point and a position of the second representative detection point satisfies a predetermined condition, in a case where the object determination unit determines that the first representative detection point and the second representative detection point are information of an object, transmits information of the object to a control device that controls the vehicle. 
     With this configuration, when the comparison result of the positions of the first representative detection point and the second representative detection point which are determined to be the same object by the object determination unit satisfies a predetermined condition, the information of the object is transmitted to the control device which controls the vehicle. Therefore, it is possible to prevent erroneous control of the vehicle when different objects are erroneously determined as a single object, and the positions of the representative detection points satisfy a predetermined condition. 
     The information transmission unit, when the position of the second representative detection point is closer to the vehicle in a lateral direction than the position of the first representative detection point, in the case where the object determination unit determines that the first representative detection point and the second representative detection point are information of the object, may transmit the information of the object to the control device. 
     With this configuration, at the first representative detection point and the second representative detection point which are determined to be the same object, when the position of the second representative detection point is closer to the vehicle in the lateral direction than the position of the first representative detection point, the information transmission unit transmits the information of the object to the control device. Therefore, it is possible to prevent erroneous vehicle control when different objects are erroneously determined as a single object and it is determined that the vehicle is close to the object. 
     According to a second aspect of the embodiments of the present invention, there is provided a object detection system, comprising: the radar device described above; and a control device that controls the vehicle on the basis of the information of the object, transmitted from the information transmission unit of the radar device. 
     According to a third aspect of the embodiments of the present invention, there is provided an object detection method which scans a transmission wave to detect a detection point representing a position of an object disposed around the vehicle on the basis of a reflected wave of the transmission wave from the object, and detects information of the object on the basis of the detection point, the object detection method comprising: reading information of detection points from a memory which stores the information of the detection points including a first representative detection point closest to the vehicle, which are detected in first scanning; determining whether or not the detection points of the read information are continuously detected in second scanning after the first scanning; setting one of the detection points second-closest to the vehicle next to the first representative detection point from among detection points disposed within a predetermined range from the first representative detection point in the first scanning as a second representative detection point in the second scanning when the first representative detection point is not detected in the second scanning; and determining the first representative detection point and the second representative detection point are information of different objects when the second representative detection point exists at a position distant from a position of the first representative detection point by equal to or more than a predetermined distance. 
     According to the second and third aspects, when the second representative detection point exists at a position distant from the position of the first representative detection point by equal to or more than a predetermined distance, it is determined that the first representative detection point and the second representative detection point are information of different objects. Therefore, it is possible to prevent different objects from being erroneously determined as a single object. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings: 
         FIG. 1  is an overall view of a vehicle; 
         FIG. 2  is a block diagram of an object detection system; 
         FIG. 3  is a diagram showing an FM-CW signal and a beat signal; 
         FIG. 4  is a flowchart of object detection processing; 
         FIG. 5  is a flowchart of detection point coupling processing of object information which is output in accordance with first detection point coupling processing; 
         FIG. 6  is a diagram illustrating a specific example of detection point coupling processing of object information which is output in accordance with first detection point coupling processing; 
         FIG. 7  is a flowchart showing detection point coupling processing of object information which is output in accordance with second detection point coupling processing; 
         FIG. 8  is a diagram illustrating representative detection point resetting processing in the same object; 
         FIG. 9  is a diagram showing determination of the same object within a coupling range; 
         FIG. 10  is a diagram illustrating representative detection point resetting processing in a new object; and 
         FIG. 11  is a diagram showing determination of a new object within a coupling range. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     &lt;1. Configuration&gt; 
       FIG. 1  is an overall view of a vehicle  1 . In the vehicle  1 , an object detection system  10  of this embodiment includes a radar device  2  and a vehicle control section  3 . The radar device  2  is provided in the front portion of the vehicle. The radar device  2  scans a detection range RE to calculate the relative distance between the vehicle  1  and an object and the relative speed and to calculate the lateral distance (angle) of an object when viewed from the vehicle  1 . The mounting position of the radar device  2  is not limited to the front portion of the vehicle, and may be the rear portion or the lateral portion of the vehicle  1 . 
     The vehicle control section  3  performs vehicle control of the vehicle  1  in accordance with the detection result of an object of the radar device  2 . Examples of vehicle control include acceleration control or brake control when the vehicle is traveling by following a preceding vehicle, and brake control for collision prevention. A passenger being fastened in a seat by a seat belt is prepared for a time of collision, or a headrest is fixed such that at the time of collision injury to the body of a passenger is reduced. 
       FIG. 2  is a block diagram of the object detection system  10 . The object detection system  10  is configured such that the radar device  2  and the vehicle control section  3  are electrically connected to each other. The vehicle control section  3  of the object detection system  10  is electrically connected to various sensors provided in the vehicle  1 , such as a vehicle speed sensor  30 , a steering sensor  31 , and a yaw rate sensor  32 . The vehicle control section  3  is also electrically connected to various devices, such as a brake  40 , a throttle  41 , and an alarm  42 , which are provided in the vehicle  1 . 
     The radar device  2  includes a signal processing section  11 , a modulation section  12 , a VCO (Voltage Controlled Oscillation)  13 , a directional coupler  14 , a planer antenna  15 , a mixer  16 , a filter  17 , an A/D (analog-to-digital) converter  18 , a motor driving section  19 , a motor  20 , and an encoder  21 . The planar antenna  15  has a transmitting antenna  15   a  and a receiving antenna  15   b . Although in the following embodiment, a case will be described where the antenna scanning method of the radar device  2  is a mechanical scanning method in which an antenna is driven in a predetermined direction, the invention may be applied to an electronic scanning method in which DBF (Digital Beam Forming) or the like is used in estimating the direction of an object without driving an antenna. 
     With regard to object detection by the radar device  2 , the modulation section  12  generates a modulated signal in a frequency band set in advance on the basis of a signal from the signal processing section  11 . The modulated signal is converted to a transmission signal by the VCO  13  and output as a transmission wave from the transmitting antenna  15   a  of the planar antenna  15  through the directional coupler  14 . 
     The transmission wave output from the planar antenna  15  is reflected from an object and received as a reflected wave by the planar antenna  15 . The received reflected wave and an oscillation signal are mixed by the mixer  16  through the directional coupler  14 . 
     A received signal mixed with the transmission signal is a beat signal including information of the relative distance from the object or the relative speed. The beat signal is filtered by the filter  17 , such that a beat signal in a band including information of the relative distance between the vehicle  1  having the radar device  2  and the object or the relative speed is detected. 
     The beat signal which is filtered in a predetermined frequency band by the filter  17  is converted from an analog signal to a digital signal by the A/D converter  18  and then input to the signal processing section  11 . 
     The radar device  2  moves the planar antenna  15  within a predetermined angle range to scan transmission waves. When the radar device  2  is provided in the front bumper portion of the vehicle  1  and a preceding vehicle is located directly in front of the vehicle  1 , if the planar antenna  15  is at a position perpendicular to the preceding vehicle, the angle of the planar antenna  15  is set to 0 degrees. For example, the planar antenna  15  carries out scanning by 15 degrees left and right from the state of 0 degrees. The state where the angle is 0 degrees refers to a case where the lateral distance between the vehicle  1  and the preceding vehicle is 0 m. The scanning of the planar antenna  15  is carried out by the motor driving section  19  and the motor  20 , information of the number of passages through a slit (not shown) of the encoder  21  and the passage direction according to the scanning of the planar antenna  15  is output to the signal processing section  11 . 
     The signal processing section  11  includes a CPU  11   a  which controls the respective sections of the radar device  2  and performs information processing when data is transmitted and received to and from the vehicle control section  3 , and a memory  11   b  which stores a program to be used for processing in the CPU  11   a . Various functions of the CPU  11   a  are realized by executing the program. The relative distance between the vehicle  1  and an object or the relative speed is detected on the basis of a signal output from the A/D converter  18 . The lateral distance (angle) between the vehicle  1  and the object is detected on the basis of information output from the encoder  21 . In this way, these are detected as the parameter values of object information. 
     Although a case has been described where the memory  11   b  of the signal processing section  11  is provided inside the signal processing section  11 , the memory  11   b  is not limited as being provided inside the signal processing section  11  and may be provided inside the radar device  2  or outside the radar device  2 . 
     In this embodiment, information of an object detected by the radar device  2  is referred to as object information, and as the parameter values of the object information, there are the relative distance, the relative speed, and the lateral distance (angle) of an object when viewed from the vehicle  1 . The memory  11   b  of the signal processing section  11  also stores multiple pieces of data, such as object information detected through past object detection processing. 
     The vehicle control section  3  which is electrically connected to the signal processing section  11  includes a CPU  3   a  and a memory  3   b . The CPU  3   a  controls the respective sections of the vehicle  1  and performs information processing when data is transmitted and received to and from the signal processing section  11 . The memory  3   b  stores a program to be used for processing in the CPU  3   a  and also stores object information transmitted from the signal processing section  11 . Various functions of the CPU  3   a  are realized by executing the program. 
     Although a case has been described where the memory  3   b  of the vehicle control section  3  is provided inside the vehicle control section  3 , the memory  3   b  is not limited as being provided inside the vehicle control section  3  and may be provided outside the vehicle control section  3 . 
     The brake  40 , the throttle  41 , and the alarm  42  are electrically connected to the vehicle control section  3 . The vehicle control section  3  controls the brake  40 , the throttle  41 , and the alarm  42  in accordance with object information, such that the operation of the vehicle  1  is controlled. For example, when the vehicle  1  comes close to an object, the alarm  42  issues a warning to notify an abnormality to a driver as a user. When the vehicle  1  is likely to collide against an object, the brake  40  is operated to reduce the speed of the vehicle  1 , or the throttle  41  is narrowed to reduce the number of rotations of the engine. 
     To the vehicle control section  3  are also connected the vehicle speed sensor  30  which detects the speed of the vehicle  1 , the steering sensor  31  which detects the steering angle of the steering wheel, and the yaw rate sensor  32  which detects the turning speed of the vehicle  1 . With the use of both the steering sensor  31  and the yaw rate sensor  32 , it becomes possible to detect the turning direction of the vehicle  1  and the turning speed of the vehicle  1  according to steering manipulation. For this reason, it is preferable that both sensors are provided, but either the steering sensor  31  or the yaw rate sensor  32  may be used to detect the turning direction of the vehicle  1 . 
     The transmission waves and the received waves which are transmitted and received by the planar antenna  15  may be signals, such as electric waves, laser, or ultrasonic waves. Any signal may be used insofar as the signal is transmitted from the planar antenna  15 , reflected from an object, and received as a reflected wave, detecting object information. 
     Although in this embodiment, an antenna is the planar antenna  15 , in addition to the planar antenna  15 , a lens antenna, a reflecting mirror antenna, or the like may be used insofar as the antenna can output a transmission wave and receive a reflected wave of the transmission wave from the object. Although a case has been described where the transmitting antenna  15   a  and the receiving antenna  15   b  are provided separately, a transmission/reception antenna may be used such that a single antenna can carry out both transmission and reception. 
     Next, as an example of signal processing which is used for object detection processing, an FM-CW (Frequency Modulated Continuous Wave) method will be described. Although in this embodiment, the FM-CW method will be described as an example, the signal processing method is not limited to the FM-CW method and any method may be used insofar as object information is calculated in a combination of a plurality of periods including an up period and a down period. 
     The symbols for an FM-CW signal and a beat signal in the following expression or in  FIG. 3  are denoted as follows: fb: beat frequency, fs: frequency, fr: distance frequency, fd: speed frequency, f 0 : center frequency of transmission wave, Δf: frequency shift width, fm: repetition frequency of modulated wave, C: light speed (speed of electric wave), T: reciprocation time of electric wave to object, R: distance to object, and v: relative speed to object. 
     An upper view of  FIG. 3  is a diagram showing the signal waveforms of an FM-CW transmission signal and a received signal. A lower view of  FIG. 3  is a diagram showing a beat frequency which is generated by a differential frequency between a transmission signal and a received signal. In the upper view of  FIG. 3 , the horizontal axis represents time and the vertical axis represents frequency. In the drawing, a transmission signal indicated by a solid line has the nature that the frequency changes in a predetermined cycle. The transmission signal has an up period in which the frequency rises and a down period in which the frequency rises to a predetermined frequency and then falls to a predetermined frequency. The transmission signal repeatedly undergoes a predetermined change such that the frequency rises to a predetermined frequency, falls to a predetermined frequency, and again rises to a predetermined frequency. The transmission signal is reflected from an object and received, and becomes a received signal indicated by a broken line in the drawing. Similarly to the transmission signal, the received signal has a down period and an up period. As a frequency band which is used in this embodiment, a frequency in a band of 76 Ghz is exemplified. 
     The received signal has a temporal delay (T=2R/C) depending on the distance between the vehicle  1  and the object compared to the transmission signal. When there is a difference in speed between the vehicle  1  and an object, the received signal is shifted in parallel to the axis of the frequency fs compared to the transmission signal. The Doppler shift amount becomes fd. 
     In the lower view of  FIG. 3  in which the horizontal axis represents time and the vertical axis represents beat frequency, the beat frequency is calculated by Expression (1).
 
 fb=fr±fd =(4 ·Δf·fm/C ) R +(2 ·f 0 /C ) v   (1)
 
     The beat signal expressed by Expression (1) is subjected to FFT processing described below, such that a frequency spectrum is detected. Within the detected frequency spectrum, a frequency spectrum which exceeds a predetermined threshold value is detected as a peak signal, and processing described below is performed for the peak signal. Thus, the relative distance between the vehicle  1  and an object, the relative speed, and the lateral distance (angle) from an object are calculated. 
     &lt;2. Operation&gt; 
     &lt;2-1. Object Information Output Processing&gt; 
       FIG. 4  is a flowchart of object detection processing. This processing is repeatedly performed each time scanning in front of the vehicle is completed. A beat signal which is generated by mixing a transmission signal and a received signal is A/D converted by the A/D converter (analog-to-digital converter)  18  and loaded on the signal processing section  11 , such as a microcomputer. The signal processing section  11  performs FFT (Fast Fourier Transform) processing for the beat signal (Step S 101 ). 
     The beat signal subjected to the FFT processing is detected as a frequency spectrum. In general, the frequency spectrum of an object has a relative power level greater than a frequency spectrum, such as noise. Thus, a frequency spectrum which exceeds a threshold value at a predetermined power level is extracted as a peak signal (Step S 102 ). 
     With regard to the peak signal which is extracted for each angle of the antenna, a plurality of peak signals are grouped as a single group on the basis of information of the speed of the vehicle  1 , the signal intensity of the peak signal, and the angle of the peak signal (Step S 103 ). As a result, a plurality of groups each including a plurality of peak signals are generated in each of the up period and the down period. The grouping processing is performed such that received signals which are received in a predetermined reflection range of an object are detected as a plurality of peak signals at each of the continuous angles of the object, a plurality of peak signals in a predetermined angle range at each of the continuous angles are grouped as a single group, and this group is set as a single reflection point. 
     The peak signals in a plurality of groups which are generated in the up period and a plurality of groups which are generated in the down period are paired on the basis of information of the speed of the vehicle  1 , the signal intensity of the grouped peak signals, and the angle of the grouped peak signals (Step S 104 ). Through the pairing processing, a reflection point from a single object is determined as a detection point. 
     Continuity determination is performed to determine whether or not a detection point which is the same as a detection point, which has been detected in past scanning, is continuously detected in current scanning (Step S 105 ). As an example of determination, from object information of a past detection point stored in the memory  11   b  and speed information of the vehicle  1  from the vehicle speed sensor  30 , it can be predicted in advance at which position in a current scanning range a detection point in past scanning will be detected. If there is a detection point within the predicted range, it is determined that the detection point which has been detected in the past is continuously detected in current scanning. 
     If the continuity determination is performed, the signal processing section  11  increases the count of the number of times of continuity by +1 for a detection point which is determined as being continuously detected, and applies only a detection point, which has been determined to have multiple-times (for example, three-times) continuity, to subsequent processing after Step S 107 . In Step S 107 , it is determined whether or not object information of detection point coupling processing described below in past (for example, previous) scanning is stored in the memory  11   b  (Step S 107 ). 
     When object information based on detection point coupling processing in past scanning is not stored in the memory  11   b  (No in Step S 107 ), first detection point coupling processing of Step S 108  is performed. When object information based on detection point coupling processing of past scanning is stored in the memory  11   b  (Yes in Step S 107 ), second detection point coupling processing of Step S 109  is performed. 
     In Step S 105 , a detection point which is determined to be not continuously detected, for example, a detection point which is newly detected is continuously detected in subsequent scanning and will be thus subjected to processing after Step S 107 . 
     The detection point coupling processing of Step S 108  or S 109  is mainly performed such that, as described above, a detection point at the closest distance from the vehicle  1  from among detection points, which are determined in multiple-times scanning to have multiple-times continuity, is set as a representative detection point, and detection points which fall within a predetermined range (within a coupling range) substantially centered on the representative detection point are coupled as a single object. Specifically, processing is performed in which detection points based on a plurality of reflection points from one of mobile objects, such as an automobile, a truck, and a motorcycle, or stationary objects, such as a guardrail and a railroad bridge, are coupled as single object information. The first detection point coupling processing and second detection point coupling processing will be described below. 
     After the first detection point coupling (Step S 108 ) or the second detection point coupling (Step S 109 ), object information in which detection points are coupled is output to the vehicle control section  3  (Step S 110 ). The vehicle control section  3  performs vehicle control, such as manipulation of the brake  40 , manipulation of the throttle  41 , and manipulation of the alarm  42 , on the basis of the output object information. 
     After the object information is output in Step S 110 , when the ACC of the vehicle  1  is not in the OFF state (No in Step S 111 ), the process returns to the initial step (Step S 101 ) and the object detection processing based on subsequent scanning is repeatedly performed. When the ACC of the vehicle  1  is in the OFF state, the object detection processing ends. 
     In the second detection point coupling processing, if predetermined determination described below is made (No in Step S 305  of  FIG. 7 ), Step S 110  is not performed and the process progresses to Step S 111 . 
     &lt;2-2. First Detection Point Coupling&gt; 
     Next, the first detection point coupling processing in the signal processing section  11  will be described in detail.  FIG. 5  is a flowchart showing detection point coupling processing of object information, which is output to the vehicle control section  3  in accordance with the first detection point coupling processing, at the time of the first detection point coupling processing in  FIG. 4 . That is,  FIG. 5  is a flowchart illustrating processing which is performed when object information with detection points coupled in past (for example, previous) detection point coupling processing is not stored in the memory  11   b.    
       FIG. 6  is a diagram illustrating a specific example of detection point coupling processing of object information which is output to the vehicle control section  3  in accordance with the first detection point coupling processing. The xy coordinate axes shown in  FIG. 6  or later are relatively fixed with respect to the vehicle  1 . The lateral direction of the vehicle  1  corresponds to the x-axis direction and the longitudinal direction (traveling direction) of the vehicle  1  corresponds to the y-axis direction. 
     As the result of Step S 106  of  FIG. 4 , as shown in  FIG. 6 , as the detection points having multiple-times continuity, a detection point JP 1  of a vehicle  100   a  on a road R 1  on which the vehicle  1  is traveling, a detection point KP 1  of a vehicle  100   b  on the road L 1  in the lateral direction (+x-axis direction) of the vehicle  1 , and a detection point LP 1  of a vehicle  100   c  are detected. These detection points fall within the detection range RE of the radar device  2  of the vehicle  1 . 
     In the first detection point coupling, first, representative detection point extraction shown in  FIG. 5  from a plurality of detection points is performed (Step S 201 ). In the representative detection point extraction, a detection point at the closest relative distance from the vehicle  1  is extracted from a plurality of detection points JP 1 , KP 1 , and LP 1 . In  FIG. 6 , the detection point JP 1  is extracted as a representative detection point. 
     Next, the coupling range of object information is set on the basis of the extracted representative detection point (Step S 202 ). As shown in  FIG. 6 , a coupling range CE 1  is set within a predetermined range substantially centered on the representative detection point JP 1 . The detection points which fall within the coupling range CE 1  are coupled as single object information (Step S 203 ). In  FIG. 6 , the detection points within the coupling range CE 1  include only the representative detection point JP 1 . Thus, the position or the like of the representative detection point JP 1  is output to the vehicle control section  3  as object information of a single object. 
     The coupling range CE 1  has a shape in which all the detection points as the reflection points from a single vehicle are included, and has a rectangular shape shown in  FIG. 6  which has the sides in the x-axis direction and the y-axis direction. The coupling range CE 1  may have a polygonal shape, instead of the rectangular shape, insofar as all the detection points as the reflection points from a single vehicle are included. 
     Next, it is determined whether or not there is a detection point other than the coupled detection point JP 1  from among the detection points detected within the detection range RE (Step S 204 ). As the result of determination, when there is another detection point (Yes in Step S 204 ), the representative detection point extraction starts for the remaining detection points which are not coupled in the previous coupling processing (Step S 201 ). When there is no another detection point which is not coupled (No in Step S 204 ), the coupled object information is output to the vehicle control section  3  as information of a single object. 
     In  FIG. 6 , there are the detection point KP 1  of the vehicle  100   b  and the detection point LP 1  of the vehicle  100   c  other than the representative detection point JP 1  which is coupled in the previous coupling processing. For this reason, it is determined in Step S 204  of  FIG. 5  that there is another detection point (Yes in Step S 204 ), and the representative detection point extraction (Step S 201 ) is again performed. A detection point at the closest relative distance from the vehicle  1  other than the coupled detection point is the detection point KP 1  of the vehicle  100   b . Thus, the detection point KP 1  is extracted as a representative detection point (Step S 201 ). 
     A coupling range CE 2  substantially centered on the representative detection point KP 1  is set (Step S 202 ). The representative detection point KP 1  and the detection point LP 1  fall within the coupling range CE 2 . For this reason, the representative detection point KP 1  and the detection point LP 1  are coupled as a single object (Step S 203 ). The object information of the coupling range CE 1  and the object information of the coupling range CE 2  which are coupled on the basis of the representative detection point are determined to be different pieces of object information. 
     Although the coupling range CE 2  is intrinsically set to couple the detection points as the reflection points from a single vehicle, as described above, when the detection point KP 1  of the single vehicle  100   b  is close to the detection point LP 1  of another vehicle  100   c , the detection points of different vehicles may be coupled as the detection points of a single vehicle. 
     After the detection point coupling, in  FIG. 6 , there is no another detection point (No in Step S 204 ). Thus, in Step S 110  of  FIG. 4 , the object information is output to the vehicle control section  3 , and the object information representing the representative detection point and the detection points coupled to the representative detection point is stored in the memory  11   b.    
     &lt;2-3. Second Detection Point Coupling&gt; 
     Next, the second detection point coupling processing in the signal processing section  11  will be described.  FIG. 7  is a flowchart showing detection point coupling processing of object information which is output in accordance with the second detection point coupling processing. In describing the processing of  FIG. 7 ,  FIG. 8  which is a diagram illustrating representative detection point resetting processing in the same object and  FIG. 9  which is a diagram showing determination of the same object within a coupling range are used. In describing the processing of  FIG. 7 ,  FIG. 10  which is a diagram illustrating representative detection point resetting processing in a new object and  FIG. 11  which is a diagram showing determination of a new object within a coupling range are used. 
     First, the signal processing section  11  reads object information from the memory  11   b  which stores object information of past scanning (Step S 301 ). When a detection point corresponding to a representative detection point in past scanning (for example, previous scanning) exists in current scanning (Yes in Step S 302 ), as described with reference to  FIG. 6 , the detection point corresponding to the representative detection point is set as a representative detection point in current scanning, a coupling range is set within a predetermined range substantially centered on the representative detection point (Step S 303 ), and the detection points which fall within the coupling range are coupled as single object information (Step S 304 ). The position or the like of the representative detection point is output to the vehicle control section  3  as object information of a single object. 
     Returning to Step S 302 , when a detection point corresponding to a representative detection point in past scanning does not exist in current scanning (No in Step S 302 ), it is determined whether or not there is a detection point at a close relative distance from the vehicle  1  next to the representative detection point in past scanning (Step S 305 ). When there is a detection point at a close relative distance from the vehicle  1  next to the representative detection point (Yes in Step S 305 ), it is determined whether or not the detection point exists within the same object determination range in past scanning (Step S 306 ). 
     Processing related to the same object determination range will be described with reference to  FIGS. 8 and 9 . In Step S 305 , when there is no detection point close to the host vehicle next to the representative detection point in past scanning (No in Step S 305 ), the processing ends and progresses to Step S 111  of  FIG. 4  to determine the state of the ACC of the vehicle  1 . 
     Scanning SC 1  on the upper side of  FIG. 8  represents object information which has been detected in past scanning. In this case, the vehicle  1  having the radar device  2  is going straight through a road R 1  (is traveling in the +y direction). Within a scanning range RE of the vehicle  1 , a detection point SP 1  and a detection point SP 2  of a vehicle  101   a  which is traveling on the road L 1  in a direction (−y direction) toward the vehicle  1  and a detection point TP 1  of a vehicle  101   b  in a direction (−y direction) toward the vehicle  1  fall within a coupling range CE 3 . Within the coupling range CE 3 , the detection point SP 1  at the closest relative distance from the vehicle  1  is substantially at the center and becomes a representative detection point. 
     In subsequent scanning SC 2 , the representative detection point SP 1  which has been detected in the scanning SC 1  is not detected. Thus, within the coupling range CE 3  of the previous scanning SC 1 , the detection point SP 2  at a close relative distance from the vehicle  1  next to the representative detection point SP 1  is set as a new representative detection point in the scanning SC 2 . 
     A coupling range CE 3  centered on the new representative detection point SP 2  is set, the representative detection point SP 2  and the detection point T 1  within the coupling range CE 3  are coupled as a single object, and the position or the like of the representative detection point SP 2  is output to the vehicle control section  3  as object information of a single object. The new representative detection point SP 2  exists within the same object determination range described below in the past scanning SC 1 . Thus, it is determined to be the same object as the past object information.  FIG. 9  shows this processing in detail. 
     In scanning SC 1  on the upper side of  FIG. 9 , a rectangular coupling range CE 3  of 30 m vertically (y-axis) and 4 m horizontally (x-axis) substantially centered on the representative detection point SP 1  is provided. A detection point SP 2  exists in the lateral direction (+x direction) distant (+y direction) from the representative detection point SP 1 . In other words, the detection point SP 2  exists at a position distant (+y direction) from the position of the representative detection point SP 1  by less than a predetermined distance (for example, less than 3 m). 
     A detection point TP 1  exists distant (+y direction) from the representative detection point SP 1 . In other words, the detection point TP 1  exists at a position distant (+y direction) from the position of the representative detection point SP 1  by equal to or more than a predetermined distance (for example, equal to or more than 3 m). 
     Within a coupling range in the lateral direction (2 m in the +x direction and 2 m in the −x direction) from the position of the representative detection point SP 1 , a range surrounded by a position (a position distant from the position of the representative detection point SP 1  in the +y direction by 3 m) distant (+y direction) from the position of the representative detection point SP 1  in the longitudinal direction (y-axis direction) by less than a predetermined distance (for example, less than 3 m) is set as a same object determination range AR 1 . Within a coupling range in the lateral direction from the position of the representative detection point SP 1 , a range surrounded by a position (a position distant from the position of the representative detection point SP 1  in the −y direction by 15 m) close to the vehicle from the position of the representative detection point SP 1  is set as a same object determination range AR 2 . The detection point SP 2  of the scanning SC 1  exists within the same object determination range AR 1 . A detection point which exists within the same object determination range in the scanning SC 1  is determined as the detection point of the same object as the representative detection point SP 1  in the scanning SC 1  which has not been detected in the scanning SC 2 . 
     In the current scanning SC 2 , there is no representative detection point SP 1  in the past scanning SC 1 . Thus, the detection point SP 2  at a close relative distance from the vehicle  1  next to the representative detection point SP 1  in past scanning becomes a new representative detection point in the scanning SC 2 . The new representative detection point exists within the same object determination range in past scanning. Thus, it is determined to be the same object as the representative detection point SP 1 . 
     In the scanning SC 2 , the coupling range CE 3  of the same object as the past scanning SC 1  based on the newly set representative detection point SP 2  is set, and the representative detection point SP 2  and the detection point T 1  which exist within the coupling range are coupled to be a single object, and information of the position of the like of the representative detection point SP 2  is output to the vehicle control section  3  as object information of a single object. Thus, the same object can be correctly determined as a single object. 
     Next, returning to Step S 306  of  FIG. 7 , when there is no detection point within the same object determination range (No in Step S 306 ), a detection point at a close relative distance from the vehicle  1  next to the representative detection point from among the detection points within the coupling range in past scanning and out of the same object determination range is reset as a new representative detection point (Step S 308 ), a coupling range is set on the basis of the new representative detection point (Step S 303 ), the detection points within the coupling range are coupled (Step S 304 ), and information of the position or the like of the representative detection point is output to the vehicle control section  3  as new object information. 
     Scanning SC 1  on the upper side of  FIG. 10  represents object information which has been detected in past scanning. In this case, the vehicle  1  having the radar device  2  is going straight through a road R 1  (is traveling in the +y direction). Within a scanning range RE of the vehicle  1 , a detection point MP 1  of a vehicle  102   a  which is traveling on the road L 1  in a direction (−y direction) toward the vehicle  1  and a detection point NP 1  of a vehicle  102   b  in a direction (−y direction) toward the vehicle  1  are within a coupling range CE 4 . Within the coupling range CE 4 , the detection point MP 1  at the closest relative distance from the vehicle  1  is substantially at the center and becomes a representative detection point. 
     In subsequent scanning SC 2 , the representative detection point MP 1  which has been detected in the scanning SC 1  is not detected. Thus, within the coupling range CE 4  of the previous scanning SC 1 , the detection point NP 1  at a close relative distance from the vehicle  1  next to the representative detection point MP 1  is set as a new representative detection point in the scanning SC 2 . 
     A coupling range CE 5  substantially centered on the new representative detection point NP 1  is newly set, the representative detection point NP 1  within the coupling range is coupled as a single object, and the position or the like of the representative detection point NP 1  is output to the vehicle control section  3  as object information of a single object. Within the coupling range CE 5 , there is no detection point other than the representative detection point NP 1 . Thus, detection point coupling processing is performed using a single detection point. 
     The new representative detection point NP 1  exists out of the same object determination range in the past scanning SC 1 , such that it is determined to be an object different from past object information. That is, the new representative detection point NP 1  exists at a position distant (+y direction) from the position of the representative detection point MP 1  in the past scanning SC 1  by equal to or more than a predetermined distance (for example, equal to or more than 3 m). For this reason, the representative detection point MP 1  in the scanning SC 1  and the representative detection point NP 1  in the scanning SC 2  are determined as different pieces of object information. With regard to the coupling range, the coupling range CE 5  is used as the coupling range of object information different from the coupling range CE 4  of the scanning SC 1 .  FIG. 11  shows this processing in detail. 
     In scanning SC 1  on the upper side of  FIG. 11 , a rectangular coupling range CE 4  of 30 m vertically (y axis) and 4 m horizontally (x axis) substantially centered on the representative detection point MP 1  is provided. A detection point NP 1  exists distant (+y direction) from the representative detection point MP 1 . In other words, the detection point NP 1  exists at a position distant from the position (+y direction) of the representative detection point MP 1  by equal to or more than a predetermined distance (for example, equal to or more than 3 m). 
     With regard to the detection point NP 1 , within a coupling range in the lateral direction (2 m in the +x direction and 2 m in the −x direction) from the position of the representative detection point MP 1 , a range surrounded by a position (a position distant from the position of the representative detection point MP 1  in the +y direction by 3 m) distant (+y direction) from the position of the representative detection point SP 1  in the longitudinal direction (y-axis direction) by less than a predetermined distance (for example, less than 3 m) is set as a same object determination range AR 1 . Within a coupling range in the lateral direction from the position of the representative detection point MP 1 , a range surrounded by a position (a position distant from the position of the representative detection point MP 1  in the −y direction by 15 m) from the position of the representative detection point MP 1  close to the vehicle is set as a same object determination range AR 2 . The detection point NP 1  of the scanning SC 1  exists within the coupling range CE 4 , not within the same object determination ranges AR 1  and AR 2 . 
     In current scanning SC 2 , there is no representative detection point MP 1  of the past scanning SC 1 . Thus, the detection point NP 1  at a close relative distance from the vehicle  1  next to the representative detection point SP 1  in past scanning becomes a new representative detection point in the scanning SC 2 . The new representative detection point exists out of the same object determination range in past scanning, such that it is determined to be information of an object different from the representative detection point MP 1 . That is, in the past scanning SC 1 , the representative detection point NP 1  exists at a position distant (+y direction) from the position of the representative detection point MP 1  in the scanning SC 1  by equal to or more than a predetermined distance (for example, equal to or more than 3 m). Thus, it is determined to be object information different from the representative detection point MP 1  of the scanning SC 1  and the representative detection point NP 1  of the scanning SC 2 . 
     In the scanning SC 2 , a coupling range CE 5  of object information different from the past scanning SC 1  based on the newly set representative detection point NP 1  is set, the representative detection point NP 1  within the coupling range is coupled as object information, and information of the position or the like of the representative detection point NP 1  is output to the vehicle control section  3  as object information. For this reason, it is possible to prevent erroneous determination of the movement direction of an object due to erroneous recognition of different objects as a single object. 
     On the condition that the representative detection points in multiple-times scanning are determined to be the same object, in comparison of object information based on the position or the like of the representative detection point in the past scanning SC 1  and object information based on the position or the like of the representative detection point in the subsequent scanning SC 2 , when a predetermined condition is satisfied, the object information is transmitted to the vehicle control section  3 . Thus, it is possible to prevent erroneous vehicle control when different objects are erroneously determined as a single object and, in Step S 110  of  FIG. 4 , the positions of the representative detection points satisfy a predetermined condition. 
     As an example where a predetermined condition is satisfied, a case is exemplified where the position of the representative detection point in the subsequent scanning SC 2  is closer to the vehicle  1  in the lateral direction than the position of the representative detection point in the past scanning SC 1 . In other words, a case is exemplified where object information based on the representative detection point in the past scanning SC 1  and object information based on the representative detection point in the subsequent scanning SC 2  are the same object information, and the position of the representative detection point in the subsequent scanning SC 2  is closer to the vehicle  1  than the position of the representative detection point in the past scanning SC 1 . Thus, it is possible to prevent erroneous control of the vehicle  1  when different objects are erroneously determined as a single object and it is determined that the vehicle  1  is close to the object.