Patent Publication Number: US-2023145455-A1

Title: Collision avoidance system and vehicle equipped with it

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The disclosure of Japanese Patent Application No. 2021-181107 filed on Nov. 5, 2021, including the specification, drawings and abstract is incorporated herein by reference in its entirety. 
     BACKGROUND 
     The present invention relates to a collision avoidance system and a vehicle on which it is mounted, for example, to a collision avoidance system having a surrounding monitoring system for monitoring the surrounding area of the vehicle using a sensor and detecting the approaching vehicle, and a vehicle on which it is mounted. 
     For example, Japanese Unexamined Patent Application No. 2012-226635 (Patent Document 1) discloses a technique for preventing a vehicle collision. Patent Document 1 discloses describes a safety device for collision avoidance capable of contributing to low power consumption without degradation of the collision avoidance function. 
     SUMMARY 
     The surrounding monitoring system uses, for example, a camera or a radar using radio waves as a sensor to receive an image or reflected radio waves of a vehicle approaching an own vehicle. The surrounding monitoring system detects the presence of a vehicle approaching or the distance between the vehicle and the own vehicle, and notifies the driver of the own vehicle. However, the detection accuracy of the surrounding monitoring system depends on the environment around the own vehicle. Therefore, in a specific surrounding environment, the detection accuracy of the surrounding monitoring system may deteriorate, and it may become difficult to smoothly perform collision avoidance. For example, in an environment where there is a building between the own vehicle and the approaching vehicle, radio waves are weakened by the building, and the detection accuracy of detecting the approaching vehicle may deteriorate. Also, even in environment where sunlight or streetlight enters into the camera, the detection accuracy of the surrounding monitoring system may deteriorate. 
     Incidentally, the collision avoidance system may include a system having an approaching vehicle notification system in addition to the surrounding monitoring system. The approaching vehicle notification system performs wireless communication (inter-vehicle communication) between the own vehicle and other vehicles, to inform each other&#39;s position. The approaching vehicle notification system calculates the distance between the own vehicle and the approaching vehicle based on the obtained location information, and notifies the driver of the own vehicle of information of the approaching vehicle. By providing the approaching vehicle notification system, the own vehicle can detect the vehicle that is outside the detection range of the sensor with the inter-vehicle communication and notify the driver of the own vehicle. However, in certain surrounding environments, inter-vehicle communication may be difficult. In such an area, for example, it may become difficult to detect a vehicle moving from outside the detection range of the sensor into the detection range within a time required for collision avoidance. Thus, it may be difficult to perform the collision avoidance smoothly. 
     Patent Document 1 neither describes nor suggests such a problem. Other objects and novel features will become apparent from the description of this specification and the accompanying drawings. 
     The typical ones of the embodiments disclosed in the disclosure will be briefly described as follows. 
     According to one aspect of the present invention, a collision-avoidance system includes a sensor, a surrounding monitoring system that outputs monitoring detection information based on information acquired by the sensor, an surrounding area information acquisition system that outputs surrounding area information related to a current location, and an assistance system that generates assistance information for controlling the surrounding monitoring system based on the surrounding area information and outputs the generated assistance information to the surrounding monitoring system. 
     According to the present embodiments, it is possible to provide a collision avoidance system capable of improving the detection accuracy of vehicles requiring collision avoidance. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a block diagram showing a configuration of a collision avoidance system according to the first embodiment. 
         FIG.  2    is a diagram for explaining an operation example of the collision avoidance system according to the first embodiment. 
         FIG.  3    is a schematic diagram for explaining an operation example of the collision avoidance system according to the first embodiment. 
         FIG.  4    is a schematic diagram for explaining an operation example of the collision avoidance system according to the first embodiment. 
         FIG.  5    is a diagram for explaining an operation example of the collision avoidance system according to the first embodiment. 
         FIG.  6    is a diagram for explaining an operation example of the collision avoidance system according to the first embodiment. 
         FIG.  7    is a diagram for explaining an operation example of the collision avoidance system according to the first embodiment. 
         FIG.  8    is a circuit diagram showing a configuration of a range control circuit according to the first embodiment. 
         FIG.  9    is a diagram for explaining a problem to be solved in the second embodiment. 
         FIG.  10    is a diagram for explaining a problem to be solved in the second embodiment. 
         FIG.  11    is a block diagram showing a configuration of a collision avoidance system according to the second embodiment. 
         FIG.  12    is a diagram for explaining a first operation example of the collision avoidance system according to the second embodiment. 
         FIG.  13    is a diagram for explaining the first operation example of the collision avoidance system according to the second embodiment. 
         FIG.  14    is a diagram for explaining a second operation example of the collision avoidance system according to the second embodiment. 
         FIG.  15    is a diagram for explaining the second operation example of the collision avoidance system according to the second embodiment. 
         FIG.  16    is a diagram for explaining the second operation example of the collision avoidance system according to the second embodiment. 
         FIG.  17    is a diagram for explaining the second operation example of the collision avoidance system according to the second embodiment. 
         FIG.  18    is a diagram for explaining the second operation example of the collision avoidance system according to the second embodiment. 
         FIG.  19    is a block diagram showing a configuration of a collision avoidance system according to the third embodiment. 
         FIG.  20    is a diagram for explaining the collision avoidance system according to the third embodiment. 
         FIG.  21    is a diagram for explaining the collision avoidance system according to the third embodiment. 
         FIG.  22    is a schematic diagram showing a vehicle having the collision avoidance system of the present embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, embodiments of the present invention are described in detail with reference to the drawings. It is to be noted that the disclosure is merely an example, and those skilled in the art can easily conceive of appropriate changes while maintaining the gist of the invention are naturally included in the scope of the invention. 
     In this specification and each drawing, the same or corresponding components are denoted by the same reference numerals, and a repetitive description thereof may be omitted. 
     First Embodiment 
     In the following description, a collision avoidance system mounted on a vehicle is described as an example, but the present invention is not limited thereto.  FIG.  22    is a schematic diagram showing a vehicle having the collision avoidance system according to the first embodiment.  FIG.  22    shows a vehicle  100 . An automobile is described as an example of the vehicle, but the present invention is not limited thereto. The vehicle  100  also includes a collision avoidance system  1 . The collision avoidance system  1  detects a vehicle approaching the vehicle  100  and notifies the driver (not shown) of the vehicle  100  of the detected vehicle information. The notified driver operates, for example, the vehicle  100  to avoid a collision with the notified vehicle. Here, an example will be described in which the collision avoidance system  1  notifies the driver of an approaching vehicle, but the present invention is not limited thereto. For example, the vehicle  100  may be configured to operate to automatically avoid a collision based on the notification of the collision avoidance system  1 . 
       FIG.  1    is a block diagram showing a configuration of a collision avoidance system according to the first embodiment. In  FIG.  1   , a block diagram of a collision avoidance system  1  is shown. The collision avoidance system  1  includes various systems, but only what is required in the following description is depicted in  FIG.  1   . 
     The collision avoidance system  1  of  FIG.  1    includes a surrounding monitoring system  2 , a surrounding area information acquisition system  3 , and an assistance system  4 . The surrounding monitoring system  2  includes a sensor. The surrounding monitoring system  2  detects the vehicle present in the detection range of the sensor based on the sensor information detected by the sensor (signal or data), and outputs information about the detected vehicle as a monitoring detection information  2 DB. In  FIG.  1   , a radar  2 _ 1  is illustrated as sensor. The radar  2 _ 1  transmits radio waves and receives radio waves reflected by an approaching vehicle (object). The object detection processing, which is a signal processing, is performed based on the radio waves (receiving signals) received by the radar  2 _ 1 , so that information about the direction or distance to the object is acquired. The area in which the reflected radio waves can be received becomes the detection range of the radar  2 _ 1 . Instead of the radar  2 _ 1 , for example, a camera or the like may be used as a sensor. In the case, the area that can be captured by the camera is the detection range of the camera. Then, image processing is performed on the image captured by the camera, so that information on the direction or distance to the object is acquired. 
     The surrounding area information acquisition system  3  identifies the location of the vehicle (own vehicle)  100  having the collision avoidance system  1 , which is current location of the own vehicle. The surrounding area information acquisition system  3  outputs information of surrounding area associated with the identified location as a surrounding area information  3 DB. The surrounding area information acquisition system  3  according to the first embodiment includes a device using Global Navigation Satellite System (hereinafter, also referred to as GNSS)  3 _ 1  and an area information storing unit  3 _ 2  for storing information of a surrounding area of the location identified by the GNSS  3 _ 1 . 
     The monitoring detection information  2 DB and the surrounding area information  3 DB are transferred to the assistance system  4 . The assistance system  4  generates assistance information  4 DH for assisting detection operations of the surrounding monitoring system  2  based on the monitoring detection information  2 DB and the surrounding area information  3 DB. The generated assistance information  4 DH is supplied to the surrounding monitoring system  2 . The assistance information  4 DH may be referred to as first assistance information  4 DH. The detection operations of the surroundings monitoring systems  2  are controlled by the assistance information  4 DH. In  FIG.  1   , the assistance system  4  generates the assistance information  4 DH based on the monitoring detection information  2 DB and the surrounding area information  3 DB. However, the information for generating the assistance information is not limited to the monitoring detection information  2 DB and the surrounding area information  3 DB. For example, the assistance system  4  may generate the assistance information  4 DH based on the surrounding area information  3 DB without using the monitoring detection information  2 DB. In the first embodiment, the assistance system  4  assists the surrounding monitoring system  2 . The assistance system  4  can be regarded as an assistance system for the surrounding monitoring system  2 . 
     In the collision avoidance system  1  according to the first embodiment, the surrounding monitoring system  2  is controlled by the assistance information  4 DH based on the surrounding area information  3 DB which is the information of the surrounding area obtained by the surrounding area information acquisition system  3 . That is, the surrounding monitoring system  2  is controlled in accordance with a surrounding area specific situation obtained by the surrounding area information acquisition system  3 . As a result, the surrounding monitoring system  2 , in accordance with the surrounding area specific situation, is possible to improve the detection accuracy of the vehicle present within the detection range of the sensor. Therefore, it becomes possible to detect vehicles requiring collision avoidance in a short time, it becomes possible to smoothly perform the actions for collision avoidance. 
     &lt;Operation of the Collision Avoidance System&gt; 
     Next, an operation example of the collision avoidance system  1  will be described with reference to the drawings.  FIGS.  2  to  7    are diagrams for explaining an operation example of the collision avoidance system  1  according to the first embodiment. Here, as an example, a case will be described in which a relatively large metal fence is installed at a so-called T-shaped intersection, and the radar  2 _ 1  in the collision avoidance system  1  is affected by the metal fence. 
     In  FIG.  2   , roads  10 _ 1  and  10 _ 2  are indicated. A straight-ahead road  10 _ 1  and a straight-ahead road  10 _ 2  intersect at a T-shaped intersection  10 _T. At the intersection  10 _T, a relatively large metal fence  12  is installed in the traveling direction of the road  10 _ 2 . 
     In  FIG.  2   , the own vehicle is indicated as reference numeral A. The own vehicle A is driven on the road  10 _ 2  in the direction indicated by the direction  10 _ 2 A toward the intersection  10 _T. The reference numeral B denotes a vehicle approaching the own vehicle A. The vehicle B is driven on the road  10 _ 1  in the direction indicated by the direction  10 _ 1 B toward the intersection  10 _T. The own vehicle A includes the collision avoidance system  1  described above. The collision avoidance system  1  detects the presence of the vehicle B so as to avoid a collision with the vehicle B and notifies the driver of the own vehicle A. 
     In  FIG.  2   , walls  11  are installed along roads  10 _ 1  and  10 _ 2 . It is difficult for the driver of the own vehicle A to see the vehicle B because of the walls  11 . Furthermore, the presence of the vehicle B is not detected by the surrounding monitoring system  2 , because the radio wave of the radar  2 _ 1  in the collision avoidance system  1  is blocked by the walls  11  and does not reach the vehicle B. That is, the vehicle B is to be present outside the detection range of the sensors in the collision avoidance system  1  of the own vehicle A. 
       FIGS.  3  and  4    are schematic diagrams showing  FIG.  2    three-dimensionally, taking the case where the vehicle B of  FIG.  2    is a bicycle as an example. In  FIGS.  3  and  4   , a part of the walls  11  and the own vehicle A are omitted. In the following description, the bicycle will also be described using the reference symbol B. 
     As shown in  FIG.  3   , the bicycle B moves toward the intersection  10 _T. As shown in  FIG.  4   , The bicycle B passes in front of the metal fence  12  installed facing the road  10 _ 2 , that is, between the metal fence  12  and the road  10 _ 2 . In other words, the bicycle B moves from outside the detection range of the sensors in the surrounding monitoring system  2  in the collision avoidance system  1  of the own vehicle A within the detection range. 
     The radar  2 _ 1  in the surrounding monitoring system  2  in the collision avoidance system  1  mounted on the own vehicle A receives a reflected wave from an object such as a vehicle existing within the detection range of the radar  2 _ 1 . The radar  2 _ 1  has a dynamic range DRG that indicates a range within which signal processing of the received signal can be performed. 
     Therefore, the radar  2 _ 1  can detect an object if a reflected wave from the object is within a range between the minimum level (min) and the maximum level (max) of the dynamic range DRG. 
     The surrounding monitoring system  2  outputs the distance to the object detected by the radar  2 _ 1  as the monitoring detection information  2 DB. The surrounding monitoring system  2  typically dynamically changes the dynamic range DRG of radar  2 _ 1  over time in order to detect objects generating reflected waves of various intensities. That is, the surrounding monitoring system  2 , while maintaining the range width between the minimum level (min) and the maximum level (max), moves the dynamic range DRG shown in  FIG.  5   , for example, up and down periodically. 
     As shown in  FIGS.  2  and  3   , a relatively large metal fence  12  is installed at the intersection  10 _T. That is, there is an object having a large radar reflection cross-section area in the front side of the radar  2 _ 1 . In this case, the surrounding monitoring system  2  typically controls the dynamic range DRG to maintain a status capable of detecting the reflected wave from the metal fence  12  for detecting the metal fence  12  having a large radar reflection cross-section area. 
     The intensity of the reflected wave of the bicycle B is smaller than that of the metal fence  12 . Therefore, as shown in  FIG.  6   , the reflected wave from the bicycle B may fall outside the dynamic range DRG set to detect the reflected wave from the metal fence  12 . In this case, as shown in  FIG.  4   , even if the bicycle B moves within the detection range of the radar  2 _ 1 , the bicycle may not be detected by the surrounding monitoring system  2 . Therefore, it may be difficult to smoothly avoid the collision. 
     In the collision avoidance system  1  according to the first embodiment, the surrounding area information acquisition system  3  specifies the surrounding area of the own vehicle A. For example, the surrounding area AR 1  identified by the surrounding area information acquisition system  3  is shown as a hatched area in  FIG.  2   . In the surrounding area information acquisition system  3 , the location of the vehicle A is acquired by the GNSS  3 _ 1 , and the information of the surrounding area AR 1  is acquired based on the acquired location information and the map data registered in advance, and the like. That is, by referring to the acquired location information, the information of the surrounding area AR 1  recorded in the map data is acquired. For example, in  FIG.  2   , information of the surrounding area AR 1  includes a T-shaped intersection  10 _T and the metal fence  12  that is installed facing the road  10 _ 2  at the T-shaped intersection  10 _T. The information of the surrounding area AR 1  is stored in the area information storing unit  3 _ 2 . The information stored in the area information storage unit  3 _ 2  is output as the surrounding area information  3 DB. 
     As described above, the assistance system  4  may generate the assistance information  4 DH based on the surrounding area information  3 DB without using the monitoring detection information  2 DB. First, the assistance information  4 DH is generated based only on the surrounding area information  3 DB. 
     In the situation shown in  FIG.  3   , as described above, since the bicycle B is outside the detection range of the radar  2 _ 1 , the surrounding monitoring system  2  cannot detect the bicycle B. In the situation shown in  FIG.  4   , the bicycle B moves forward and is within the detection range of the radar  2 _ 1  of surrounding monitoring system  2 . However, since the metal fence  12  having a large radar reflection cross-section area is installed in the front side of the radar  2 _ 1 , the dynamic range of the radar  2 _ 1  is set so as to detect the metal fence  12  (as shown in  FIG.  6   ). Therefore, the reflected wave from the bicycle B having a small radar reflection cross-section area as compared to the metal fence  12  falls below the minimum level (min) of the set dynamic range DRG, it is difficult for the radar  2 _ 1  to detect the bicycle B. 
     The assistance system  4  recognizes, based on the surround area information  3 DB, the T-shaped intersection  10 _T and the metal fence  12 . Then, the assistance system  4  outputs (notifications) the assistance information  4 DH indicating that an object having a large radar reflection cross-sectional area, that is, an object having a large reflected wave, such as a metal fence, is installed within the radar detection range, to the surrounding monitoring system  2 . For example, the assistance system  4  may output the assistance information  4 DH based on the surrounding area information  3 DB, when it is determined that the object generating a reflected wave of a predetermined intensity or more is included in the detection range of the radar  2 _ 1 . 
     Upon receiving this notification, the surrounding monitoring system  2  controls the radar  2 _ 1  so that it is possible to also detect objects having a small radar reflection cross-section area. In the first embodiment, as shown in  FIG.  7   , the surrounding monitoring system  2  controls the radar  2 _ 1  so as to widen the dynamic range as the dynamic range DRG_e. That is, the assistance information  4 DH is an instruction information to dynamically control the radar  2 _ 1 . This allows the surrounding monitoring system  2  to detect objects having small radar reflection cross-section area. As shown in  FIG.  7   , the reflected wave from the metal fence  12  and the reflected wave from the bicycle B are in the expanded dynamic range DRG_e, both of the presence of the metal fence  12  and the presence of the bicycle B are detected. Therefore, even if the vehicle moves into the viewable range of the own vehicle from outside of the viewable range, the surroundings monitoring system  2  detects the vehicle. As a result, the distance from the bicycle A to the bicycle B can also be obtained. 
     Thus, even if there is an object having a large radar reflection cross-sectional area within the detection range of the radar, for example, it is possible to detect a vehicle (bicycle) crossing the front, it is possible to smoothly avoid the collision. 
     Next, an example of a configuration for controlling the dynamic range of the radar  2 _ 1  will be described with reference to the drawings.  FIG.  8    is a circuit diagram showing a configuration of a range control circuit according to the first embodiment.  FIG.  8    shows the range control circuit  2 _DRG provided in the surrounding monitoring system  2 . The range control circuit  2 _DRG includes a gain variable amplifier GCA, a DC offset adjuster OFS, and an analog-to-digital converter ADC. The reflected wave from the object is input as an analog signal RF to the gain variable amplifier GCA. The DC offset of the analog signal RF amplified by the gain variable amplifier GCA is adjusted by the DC offset adjuster OFS including the resistor R 1  and the variable resistor R 2  that are connected in series between the bias voltage Vb and the ground voltage Vs. Then, the analog signal RF is converted by the analog-to-digital converter ADC to the digital signal DT. The digital signal DT becomes a signal indicating the presence or the like of the object. 
     In the surrounding monitoring system  2 , the gain variable amplifier GCA and the DC offset adjuster OFS is controlled by the assistance information  4 DH. Briefly, the gain variable amplifier GCA adjusts the amplitude, and the DC offset adjuster OFS adjusts the DC offset, so that the dynamic range of the radar relative to the reflected wave is changed. 
     In  FIG.  7   , the dynamic range DRG is expanded to DRG_e by decreasing the resolution as compared with  FIGS.  5  and  6   , but the present invention is not limited thereto. For example, by changing the bit-width of the analog-to-digital converter ADC shown in  FIG.  8    according to the assistance information  4 DH, while maintaining the resolution with high accuracy, it is also possible to expand the dynamic range DRG. 
     As shown in  FIG.  1   , the assistance system  4  may generate the assistance information  4 DH based on the monitoring detection information  2 DB and the surrounding area information  3 DB. In this case, the assistance system  4 , for example, based on the monitoring detection information  2 DB, detects the presence of the metal fence  12 , and determines, based on the surrounding area information  3 DB, that the own vehicle has entered the surrounding area AR 1 . The assistance system  4  generates the assistance information  4 DH when both conditions are satisfied. The detection accuracy can be improved by the assistance information  4 DH generated when both conditions are satisfied. 
     In  FIG.  1   , the case where the surroundings monitoring system  2  uses the radar  2 _ 1  as a sensor has been described, but the present invention is not limited thereto. For example, a camera or the like may be used as a sensor. 
     According to the collision avoidance system  1  of the first embodiment, the surrounding monitoring system  2  is controlled in accordance with the information specific to the surrounding area detected by the surrounding area information acquisition system. As a result, it becomes possible to detect vehicles that need to avoid collisions in a short time, and it is possible to smoothly perform actions of collision avoidance. 
     Second Embodiment 
     In the second embodiment, a collision avoidance system is provided in which the surrounding monitoring system comprises different types of sensors and uses sensors suitable for the detected surrounding area. 
     Before describing the details of the second embodiment, first, a problem to be solved in the second embodiment will be described with reference to the drawings.  FIGS.  9  and  10    are diagrams for explaining the problem to be solved in the second embodiment. Here, the surrounding monitoring system provided in the collision avoidance system mounted on the own vehicle (not shown) will be described with reference to a case where a camera is used as a sensor. 
     In  FIG.  9   , reference numeral  13  denotes a building that installs along a road, and reference numeral C denotes a vehicle that exists behind the building  13  and is driven in the direction  10 _ 1 C when viewed from the own vehicle. In  FIG.  9   , reference numeral  20  denotes a detection range that can be detected by the camera of the surrounding monitoring system. In this case, the camera captures the detection range  20 . The image of the detection range  20  obtained by capturing is divided into a plurality of processing unit ranges  20 _S (5×3=15 in  FIG.  9   ). The surrounding monitoring system performs image processing for detecting a moving object, such as a vehicle, and the like for each divided processing unit range  20 _S. In  FIG.  9   , the sun SN is shown in the image of the detection range  20 . 
     The vehicle C is hidden behind the building  13  and it is outside the detection range of the camera of the surrounding monitoring system. Therefore, the camera or the like of the surrounding monitoring system mounted on the own vehicle dose not detect the vehicle C. The vehicle C moves forward, as shown in  FIG.  10   , a part of the vehicle C appears from the building  13 . It is possible to photograph the vehicle C by the camera. However, at this time, as shown in  FIG.  10   , the sunlight from the sun SN is included in the detection range  20 . That is, a situation in which very strong light is incident on the camera. Therefore, the vehicle C is photographed in the situation of so-called backlight, so that the vehicle C is recognized as a shadow. Even in the situation of backlight, if the exposure or the like of the camera are adjusted, it is possible to detect the details of the vehicle C, such as the shape and speed including the vehicle type of the vehicle C. However, it may be difficult to detect the details of the vehicle C in a short time. 
       FIG.  11    is a block diagram showing a configuration of a collision avoidance system according to the second embodiment.  FIG.  11    shows a collision avoidance system  1   a . Since  FIG.  11    is similar to  FIG.  1   , the main differences will be explained. 
     The surrounding monitoring system  2   a  shown in  FIG.  11    is different from the surrounding monitoring system  2  of  FIG.  1    in that it includes a plurality of sensors of different types from each other. That is, the surrounding monitoring system  2   a  of FIG.  11  includes a radar  2 _ 1  and a camera  2 _ 2  as sensors. The surroundings monitoring system  2   a  outputs vehicle information detected based on information detected by the radar  2 _ 1  and/or information detected by the camera  2 _ 2  as monitoring detection information  2 DB_ 1 . 
     The surrounding area information acquisition system  3   a  is different from the surrounding area information acquisition system  3  of  FIG.  1    in that the surrounding area information acquisition system  3   a  further includes the time information generating unit  3 _ 3  and the notification determination unit  3 _ 4 . The time information generation unit  3 _ 3  includes, for example, a clock, and generates time information indicating the current time. The notification determination unit  34  generates the surrounding area information  3 DB_ 1  based on the information of the location detected by the GNSS 3 _ 1 , the unique information of the surrounding area acquired based on the map data, and the time information. That is, the surrounding area information  3 DB_ 1  is time-dependent information. 
     The assistance system  4   a  differs from the assistance system  4  shown in  FIG.  1    in that it further comprises a sensor switching unit  4 _ 1 . The assistance system  4   a  generates assistance information based on the surrounding area information in the same manner as in  FIG.  1   . The assistance information  4 DH_ 1  according to the second embodiment is output from the assistance system  4   a  to the surrounding monitoring system  2   a . The assistance information  4 DH_ 1  includes sensor switching information generated by the sensor switching unit  4 _ 1  based on the surrounding area information  3 DB_ 1 . The sensor switching information is information for switching a plurality of sensors (radar  2 _ 1  and camera  2 _ 2 ) included in the surrounding monitoring system  2   a . The surrounding monitoring system  2   a  is controlled based on the assistance information  4 DH_ 1 . In addition, the surrounding monitoring system  2   a  selects information obtained from a sensor suitable for the surrounding area among information obtained from a plurality of sensors based on the assistance information  4 DH_ 1 . The surrounding monitoring system  2   a  generates the monitoring detection information  2 DB_ 1  based on information from the selected sensors. 
     &lt;Operation of the Collision Avoidance System&gt; 
     Operation Example 1 
     In the surrounding area information acquisition system, unique information of the surrounding area of the own vehicle is generated based on the GNSS 3 _ 1  and the map data. In this case, information such as whether or not the moving direction of the own vehicle, that is, the sensor of the surrounding monitoring system  2   a  is directed in the direction of the sun SN, is generated as unique information of the surrounding area. At this time, the position of the sun SN in the sky is obtained by the time information generated by the time information generating unit  3 _ 3 . The notification determination unit  3 _ 4  specifies whether or not the sun SN appears within the detection range  20  of the camera  2 _ 2 . The notification determination unit  3 _ 4  further specifies the position (detection range) of the sun SN within the detection range  20  based on the time information and unique information of the surrounding area, and outputs the specified information as the surrounding area information  3 DB_ 1 . 
     Based on the surrounding area information  3 DB_ 1 , the sensor switching unit  4 _ 1  in the assistance system  4   a  generates sensor switching information for switching the sensors, and outputs the assistance information  4 DH_ 1  including the sensor switching information to the surrounding monitoring system  2   a . The surrounding monitoring system  2   a , based on the sensor switching information, performs signal processing of the signal obtained from the sensor. 
       FIGS.  12  and  13    are diagrams for explaining an operation example 1 of the collision avoidance system according to the second embodiment. For example, in  FIGS.  12  and  13   , it is assumed that the surrounding area information  3 DB_ 1  indicates that the sun SN is photographed in the detection range  20 _SN filled with hatching pattern. Based on the surrounding area information  3 DB_ 1 , the sensor switching unit  4 _ 1  notifies the surrounding monitoring system  2   a  of the assistance information  4 DH_ 1 . The detection range  20 _SN is detected by using the radar  2 _ 1  and the detection range other than the detection range  20 _SN, which is not filled with hatching pattern, is detected by using the camera  2 _ 2 . In accordance with this notification, the surrounding monitoring system  2   a  performs object detection processing on the detection range  20 _SN based on the information obtained by the radar  2 _ 1 , and performs object detection processing (image processing) on the detection range other than the detection range  20 _SN based on the information (video) obtained by the camera  2 _ 2 . That is, the surrounding monitoring system  2  switches the sensor information to be subjected to the object detection processing in each processing unit range based on the surrounding area information  3 DB_ 1 . In this manner, the surrounding monitoring system  2   a  generates the monitoring detection information  2 DB_ 1  based on the information obtained from the plurality of sensors. As a result, the vehicle C can be detected using not only by using the information detected by the camera  2 _ 2  but also the information detected by the radar  2 _ 1 , and smooth collision avoidance can be performed. 
     Alternatively, when the surrounding area information  3 DB_ 1  indicates that the sun SN appears on the detection range  20 , the sensor switching unit  4 _ 1  may instruct the surrounding monitoring system  2   a  to detect on the entire area of the detection range  20  by using the radar  2 _ 1  in place of the camera  2 _ 2 . In this case, detection by the camera  2 _ 2  may be stopped. In addition, until the exposure of the camera  2 _ 2  is adjusted, the detection by the radar  21  may be performed. After the adjustment of the exposure is completed, the sensor may be switched so as to use the camera  2 _ 2 . 
     Operation Example 2 
       FIG.  14    to  FIG.  18    is a diagram for explaining an operation example 2 of the collision avoidance system according to the second embodiment. 
     In  FIG.  14   , reference numeral  14  denotes a streetlight installed on the road  10 _ 2 .  FIG.  14    shows a situation in which the bicycle D, which is a vehicle, enters toward the intersection of the road  10 _ 1  and the road  10 _ 2  (in direction  10 _ 1 D). Further,  FIG.  14    is a situation at night, streetlights  14  are on, and although not shown, the own vehicle is moving toward the intersection on the road  10 _ 2 . 
     The own vehicle includes the collision avoidance system  1   a  shown in  FIG.  11   , and it is necessary to avoid a collision with the bicycle D. However, in the situation shown in  FIG.  14   , the bicycle D is difficult to detect by the radar  2 _ 1  and the camera  2 _ 2  because it is hidden by the wall  11 , i.e. it is outside the detection range of the surrounding monitoring system  2   a.    
     The detection range  20  of the camera  2 _ 2  at this time is shown in  FIG.  15   . In  FIG.  15   , reference numeral  14 _R indicates an area lightened by the streetlight  14 . The image captured by the camera  2 _ 2  includes bright areas  14 _R and an area outside the area  14 _R where the lights of the streetlights  14  do not reach and darkens. The image thus captured is processed and detected for each processing unit range  20 _S. 
     The situation in which the bicycle D has progressed and entered the intersection is shown in  FIG.  16   . The detection range  20  of the camera  2 _ 2  at this time is shown in  FIG.  17   . The bicycle D enters the intersection and move into the detection range  20  of camera  2 _ 2 . As shown in  FIG.  17   , the bicycle D appears between bright areas  14 _R that are brightened by streetlights  14 . That is, since the bicycle D appears in an area which is not lighted by the streetlights  14 , it is difficult to detect the bicycle D based on information from the camera  2 _ 2  in a short time. 
     In the surrounding area information acquisition system  3   a  according to the second embodiment, based on the GNSS 3 _ 1  and the map data, unique information of the surrounding area including information specifying the streetlights  14  is generated. Further, it is specified that the time is at night by the time information generated by the time information generating unit  3 _ 3 . When it is specified that the night, the notification determination unit  3 _ 4  identifies an area to be brightened by the streetlights  14  and a dark area based on the information identifying the streetlight  14 . The surrounding area information acquisition system  3   a  outputs the surrounding area information  3 DB_ 1  including information for specifying a bright area and a dark area. The assistance system  4   a  generates sensor switching information based on information identifying bright area and dark area. Based on the sensor switching information, the surrounding monitoring system  2   a  switches which of the information detected by the radar  2 _ 1  and the information detected by the camera  2 _ 2  is used for each processing unit range. 
     In  FIG.  18   , the area  20 _R filled with hatching pattern is a portion shown as a bright area by the sensor switching information. The area other than the area  20 _R in the detection range  20  is a portion shown as a dark area by the sensor switching information. In the surrounding monitoring system  2   a , the detection operations on the area  20 _R are performed by using the information (video image) detected by the camera  2 _ 2 , the detection operations of the area other than the area  20 _R is performed by using the information detected by the radar  2 _ 1 . 
     In the second embodiment, as in the first embodiment, the assistance system  4   a  may generate the assistance information  4 DH_ 1  based on the monitoring detection information  2 DB_ 1  and the surrounding area information  3 DB_ 1 . In this case, the assistance system  4   a  detects backlight by, for example, the monitoring detection information  2 DB_ 1 , and determines sensor switching by the surrounding area information  3 DB_ 1 . The assistance system  4   a  generates the assistance information  4 DH_ 1  when both conditions are met. Since the assistance information  4 DH_ 1  generated when both conditions are met is used, it is possible to improve the accuracy. 
     According to the second embodiment, the sensors for detecting the object are switched on the basis of the information specific to the surrounding area. Switching sensors makes it possible to detect objects that need to avoid collisions in a short time, making it possible to smoothly perform actions for collision avoidance. 
     Third Embodiment 
     In the third embodiment, in order to detect a vehicle that is present outside the detection range of the surrounding monitoring system, a collision avoidance system is provided with an approaching vehicle notification system for performing inter-vehicle communication with the vehicle that is present outside the detection range of the surrounding monitoring system. The collision avoidance system also includes an assistance system with a communication environment determination unit that determines the environment of inter-vehicle communication and outputs assistance information that controls the approaching vehicle notification system. 
       FIG.  19    is a block diagram showing a configuration of a collision avoidance system according to the third embodiment. 
     Since  FIG.  19    is similar to  FIG.  11   , the differences will be mainly explained. The difference is that the collision avoidance system  1   b  of  FIG.  19    further comprises an approaching vehicle notification system  15 , and the assistance system  4   b  further comprises a communication environment determination unit  4 _ 2 . In the collision avoidance system  1   b  according to the third embodiment, functions achieved by the approaching vehicle notification system  15  and the communication environment determination unit  4 _ 2  are added in addition to the functions of the collision avoidance system described in the second embodiment. Incidentally, the assistance system  4   b  shown in  FIG.  19   , to assist both the surrounding monitoring system  2   b  and the approaching vehicle notification system  15 , can be regarded as an assistance system for the surrounding monitoring system and the approaching vehicle notification system. 
     The approaching vehicle notification system  15  includes a plurality of units. However, in  FIG.  19   , only those necessary for description is shown. That is, the approaching vehicle notification system  15  includes a GNSS  15 _ 1 , a communication unit  15 _ 2 , a vehicle information storing unit  15 _ 3 , and an out-of-sight vehicle information storing unit  15 _ 4 . 
     Like the GNSS  3 _ 1  of the surrounding area information acquisition system, the GNSS  15 _ 1  detects the location or the like of the own vehicle on which the collision avoidance system  1  is mounted. Therefore, one GNSS may be used for both GNSS  15 _ 1  and GNSS  3 _ 1 . The communication unit  15 _ 2  is a communication device for performing communication (inter-vehicle communication) between the own vehicle and other vehicle (e.g., a vehicle approaching the own vehicle). The vehicle information storing unit  15 _ 3  stores information on the vehicle, such as the vehicle type. The out-of-sight vehicle information storing unit  15 _ 4  stores the information of the approaching vehicle received by the inter-vehicle communication. 
     The approaching vehicle notification system  15  performs inter-vehicle communication with the approaching vehicle to detect the approaching vehicle, and outputs information of the detected approaching vehicle as the approaching detection information  15 DB_ 1  to the assistance system  4   b . Further, the approaching vehicle notification system  15 , through inter-vehicle communication, transmits the information of the own vehicle and the location of the own vehicle detected by GNSS  15 _ 1  to the approaching vehicle. 
     As described in the second embodiment, the assistance system  4   b  generates the assistance information  4 DH_ 1  that controls the surrounding monitoring system  2   a  based on the surrounding area information  3 DB_ 1  from the surrounding area information acquisition system  3   a . At this time, the sensor switching unit  4 _ 1 , as described above, generates a sensor switching information for switching between the sensors in the surrounding monitoring system  2   a . With the surrounding area information  3 DB_ 1 , the sensors in the surrounding monitoring system  2   a  are switched so as to be suitable for the information specific to the surrounding area. 
     Further, the communication environment determination unit  4 _ 2  in the assistance system  4   b , based on the surrounding area information  3 DB_ 1 , generates the assistance information  4 DH_ 2  corresponding to the specific information of the surrounding area indicated by the surrounding area information  3 DB_ 1 , and outputs the assistance information to the approaching vehicle notification system  15 . The assistance information  4 DH_ 2  may be referred to as second assistance information. The communication unit  15 _ 2  of the approaching vehicle notification system  15  is controlled by the assistance information  4 DH_ 2 . For example, the communication interval, modulation method, transmission power, and the like of the inter-vehicle communication performed by the communication unit  15 _ 2  are changed based on the assistance information  4 DH_ 2 . 
       FIGS.  20  and  21    are diagrams for explaining a collision avoidance system according to the third embodiment. Here,  FIG.  20    is a schematic plan view of the surrounding area. In other words, the situation when the surrounding area is viewed from the sky is shown in  FIG.  20   . In  FIG.  20   , reference numeral  10  denotes a road, and reference numeral  13  denotes a building constructed along the road  10 . Further, in  FIG.  20   , the reception power of the radio wave received on the road  10  is indicated by the shading pattern, when the radio wave is emitted at the position Snd_P.  FIG.  21    shows the correspondence between the shade patterns shown in  FIG.  20    and the value of the received power. As shown in  FIG.  21   , the darker the shading pattern, the greater the received power. 
     The received power of the radio waves used in the vehicle-to-vehicle communication is affected by the building  13  and the multipath, as shown in  FIG.  20   , and varies depending on the position. For example, in certain communication intervals or specific modulation method, the inter-vehicle communication is possible with vehicles located at a position of −110 dBm or more of the received power, and may not be possible with vehicles at a position of lower received power than this. In  FIG.  20   , the specific areas in which the received power is lower than −110 dBm are denoted by the reference numerals DF_P 1  and DF_P 2 . In this case, when the own vehicle A is located at the position Snd_P, it is difficult to perform inter-vehicle communication with the vehicles located in the specific areas DF_P 1  and DF_P 2 . That is, communications with the vehicles located in the specific area DF_P 1 , DF_P 2  are not established. 
     In the third embodiment, information unique to the surrounding area is provided to the communication environment determination unit  4 _ 2  by the surrounding area information  3 DB_ 1 . The communication environment determination unit  4 _ 2  determines whether or not the specific areas DF_P 1  and DF_P 2  as shown in  FIG.  20    exist based on the unique information of the surrounding area. When it is determined that the specific areas DF_P 1  and DF_P 2  exist in the surrounding area, the communication environment determination unit  4 _ 2  instructs the communication unit  15 _ 2  to change the communication interval, modulation method, transmission output, and/or the like of the inter-vehicle communication based on the assistance information  4 DB_ 2 . 
     By this instruction, the communication unit  15 _ 2  shortens the communication interval, increases the demodulation gain by changing the modulation method, and increases the transmission output. This modification enables inter-vehicle communication with the vehicles located in the specific areas DF_P 1  and DF_P 2 . 
     That is, the communication environment is improved. 
     The communication environment determination unit  42  may generate the assistance information  4 DB_ 2  not only based on the surrounding area information  3 DB_ 1  but also based on both of the approaching detection information  15 DB_ 1  and the surrounding area information  3 DB_ 1 . For example, when the communication environment determination unit  4 _ 2  determines that the specific areas DF_P 1  and DF_P 2  based on the surrounding area information  3 DB_ 1  and determines that the communication with the vehicle located in the specific areas DF_P 1  and DF_P 2  has not been performed by using the approaching detection information  15 DB_ 1 , the assistance information  4 DH_ 2  for changing the communication interval, the modulation method, and/or the transmission output may be generated. By using the assistance information  4 DH_ 2 , it is possible to improve the accuracy. Depending on the communication environment, the communication interval, the modulation scheme and/or the transmission output or the like is changed. When the communication environment is good, for example, it is possible to increase the communication interval and to lower the transmission power. As a result, it is possible to reduce the power consumption of the collision avoidance system  1 . 
     According to the third embodiment, it is possible to further improve the communication environment and improve the detection of out-of-sight vehicles, as compared with the collision avoidance system according to the second embodiment. 
     Although the invention made by the present inventor has been specifically described based on the embodiment, the present invention is not limited to the embodiment described above, and it is needless to say that various modifications can be made without departing from the gist thereof.