Patent Publication Number: US-2021188260-A1

Title: Driver assistance system and control method thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based on and claims priority under 35 U.S.C. § 119 to Korean Patent Application No. 10-2019-0172282, filed on Dec. 20, 2019 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND 
     1. Field 
     The present disclosure relates to a driver assistance system, and more particularly, to a driver assistance system capable of avoiding a collision with surrounding objects in a driving situation, and a control method thereof. 
     2. Description of the Related Art 
     Generally, a vehicle refers to a movement device or transportation device, designed to travel on a road or railway using fossil fuel, electric power, and the like as a power source. The vehicle may move to various positions mainly using one or more wheels installed on the vehicle body. Such a vehicle may include a three-wheeled or four-wheeled vehicle, a two-wheeled vehicle, such as a motorcycle, a construction machine, a bicycle, and a train traveling on a railway arranged on a track. 
     Recently, there have been active studies on a vehicle equipped with an advanced driver assist system (ADAS), which actively provides information about the state of a vehicle, the state of a driver, and the surrounding environment to reduce the burden on the driver while enhancing the convenience of the driver. Such a system may determine a risk of collision with an object in a driving situation of a vehicle, and provide collision avoidance and warning through emergency braking in a crash situation. 
     SUMMARY 
     An aspect provides a driver assistance system capable of recognizing information on nearby objects existing in a near or far distance in a driving situation of a vehicle and avoiding a collision with surrounding objects, and a control method thereof. 
     Therefore, it is an aspect of the present disclosure to provide a driver assistance system including: a camera disposed on the vehicle to have an external field of view of a vehicle and configured to obtain image data; a radar disposed on the vehicle to have a field of sensing outside the vehicle and configured to obtain radar data; and a controller including a processor configured to process the image data and the radar data, and the controller is configured to determine whether a rear vehicle changes direction based on the image data obtained by the camera, determine whether there is a risk of collision with the rear vehicle based on the radar data when the rear vehicle does not change direction and control at least one of a steering system or a vehicle velocity control system of the vehicle to avoid the rear vehicle when it is determined that there is a risk of collision with the rear vehicle. 
     The controller may be configured to identify an avoidance space for avoiding a collision with the rear vehicle based on at least one of the image data or the radar data when it is determined that there is a risk of collision with the rear vehicle and control at least one of the steering system or the vehicle velocity control system of the vehicle so that the vehicle moves to the identified avoidance space. 
     The controller may be configured to determine the steering time point based on the relative velocity of the rear vehicle driving the adjacent lane when the avoidance space exists in the adjacent lane and control the steering system of the vehicle based on the determined steering time point. 
     The controller may be configured to select one of the plurality of avoidance spaces based on detection information obtained based on at least one of the image data or the radar data when the identified avoidance space is plural and control at least one of the steering system or the vehicle velocity control system of the vehicle so that the vehicle moves to the selected avoidance space. 
     The controller may be configured to select one of the plurality of avoidance spaces based on at least one of the size of the identified avoidance space included in the detection information, the distance between the preceding vehicle and the vehicle, the velocity of the preceding vehicle, the distance between the rear vehicle and the vehicle or the velocity of the rear vehicle. 
     The controller may be configured to detect the on or off state of the direction indicator of the rear vehicle based on the image data and determine that the rear vehicle does not change direction when the direction indicator of the rear vehicle is off state. 
     The controller may be configured to determine that there is a risk of collision with the rear vehicle when the position or relative velocity of the rear vehicle obtained based on the radar data satisfies a predetermined condition. 
     The camera may include a rear camera disposed on the vehicle to have a rear field of view. 
     The radar may include a rear radar disposed on the vehicle to have a rear field of sensing. 
     It is another aspect of the present disclosure to provide a control method of a driver assistance system mounted on a vehicle, the method includes: obtaining image data by a camera disposed on the vehicle to have an external field of view of a vehicle; obtaining radar data by a radar disposed on the vehicle to have a field of sensing outside the vehicle; processing the image data and the radar data; determining whether a rear vehicle changes direction based on the image data; determining whether there is a risk of collision with the rear vehicle based on the radar data when the rear vehicle does not change direction; and controlling at least one of a steering system or a vehicle velocity control system of the vehicle to avoid the rear vehicle when it is determined that there is a risk of collision with the rear vehicle. 
     The controlling at least one of a steering system or a vehicle velocity control system may include: identifying an avoidance space for avoiding a collision with the rear vehicle based on at least one of the image data or the radar data when it is determined that there is a risk of collision with the rear vehicle; and controlling at least one of the steering system or the vehicle velocity control system of the vehicle so that the vehicle moves to the identified avoidance space. 
     The controlling at least one of the steering system or the vehicle velocity control system of the vehicle so that the vehicle moves to the identified avoidance space may include: determining the steering time point based on the relative velocity of the rear vehicle driving the adjacent lane when the avoidance space exists in the adjacent lane; and controlling the steering system of the vehicle based on the determined steering time point. 
     The controlling at least one of the steering system or the vehicle velocity control system of the vehicle so that the vehicle moves to the identified avoidance space may include: selecting one of the plurality of avoidance spaces based on detection information obtained based on at least one of the image data or the radar data when the identified avoidance space is plural; and controlling at least one of the steering system or the vehicle velocity control system of the vehicle so that the vehicle moves to the selected avoidance space. 
     The selecting one of the plurality of avoidance spaces may include: selecting one of the plurality of avoidance spaces based on at least one of the size of the identified avoidance space included in the detection information, the distance between the preceding vehicle and the vehicle, the velocity of the preceding vehicle, the distance between the rear vehicle and the vehicle or the velocity of the rear vehicle. 
     The determining whether a rear vehicle changes direction may include: detecting the on or off state of the direction indicator of the rear vehicle based on the image data; and determining that the rear vehicle does not change direction when the direction indicator of the rear vehicle is off state. 
     The determining whether there is a risk of collision with the rear vehicle may include: determining that there is a risk of collision with the rear vehicle when the position or relative velocity of the rear vehicle obtained based on the radar data satisfies a predetermined condition. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects of the disclosure will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: 
         FIG. 1  is a diagram illustrating a configuration of a vehicle according to an embodiment; 
         FIG. 2  is a diagram illustrating a configuration of a driver assistance system according to an embodiment; 
         FIG. 3  is a diagram illustrating a camera and a radar included in a driver assistance system of a vehicle according to an embodiment; 
         FIG. 4  illustrates a camera and a radar included in a conventional driver assistance system. 
         FIGS. 5 to 9  are diagrams for illustrating an operation for avoiding a collision with a nearby object by the driver assistance system according to an embodiment. 
         FIGS. 10 and 11  are flowcharts illustrating a control method of a driver assistance system according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Like numerals refer to like elements throughout the specification. Not all elements of embodiments of the present disclosure will be described, and description of what are commonly known in the art or what overlap each other in the embodiments will be omitted. The terms as used throughout the specification, such as part“, module”, member“, block”, etc., may be implemented in software and/or hardware, and a plurality of parts“, modules”, members“, or blocks” may be implemented in a single element, or a single part“, module”, member“, or block” may include a plurality of elements. 
     It will be further understood that the term “connect” or its derivatives refer both to direct and indirect connection, and the indirect connection includes a connection over a wireless communication network. 
     It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof, unless the context clearly indicates otherwise. 
     Further, when it is stated that one member is “on” another member, the member may be directly on the other member or a third member may be disposed therebetween. 
     Although the terms “first,” “second,” “A,” “B,” etc. may be used to describe various components, the terms do not limit the corresponding components, but are used only for the purpose of distinguishing one component from another component. 
     As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. 
     Reference numerals used for method steps are just used for convenience of explanation, but not to limit an order of the steps. Thus, unless the context clearly dictates otherwise, the written order may be practiced otherwise. 
     Hereinafter, the principles and embodiments of the disclosure will be described with reference to the accompanying drawings. 
       FIG. 1  is a block diagram illustrating a configuration of a vehicle according to an embodiment. 
     Referring to  FIG. 1 , a vehicle  1  includes an engine  10 , a transmission  20 , a braking device  30 , and a steering device  40 . The engine  10  may include a cylinder and a piston, and generate power required for the vehicle  1  to travel. The transmission  20  may include a plurality of gears, and transmit the power generated by the engine  10  to wheels. The braking device  30  may decelerate or stop the vehicle  1  through friction with the wheels. The steering device  40  may change the heading direction of the vehicle  1 . 
     The vehicle  1  may include a plurality of machine parts. For example, the vehicle  1  may include an engine management system (EMS)  11 , a transmission control unit (TCU)  21 , an electronic brake control module (EBCM)  31 , an electronic power steering (EPS)  41 , a body control module (BCM)  51 , and a driver assistance system (DAS)  100 . 
     The EMS  11  may control the engine  10  in response to an acceleration intention of the driver through an accelerator pedal or a request of the DAS  100 . For example, the EMS  11  may control the torque of the engine  10 . 
     The TCU  21  may control the transmission  20  in response to a shift command of the driver through a shift lever and/or a travelling speed of the vehicle  1 . For example, the TCU  21  may adjust the gear ratio of the engine  10  to the wheels. 
     The EBCM  31  may control the braking device  30  in response to a braking intention of the driver through a braking pedal and/or a slip of the wheels. For example, the EBCM  31  may temporarily release the braking of the wheels in response to a slip of the wheels sensed at a time of braking the vehicle  1  (anti-lock braking systems: ABS). The EBCM  31  may selectively release braking of the wheels in response to over-steering and/or under-steering sensed at a time of steering the vehicle  1  (electronic stability control: ESC). In addition, the EBCM  31  may temporarily brake the wheels in response to a slip of the wheels sensed at a time of driving the vehicle  1  (traction control system: TCS). 
     The EPS  41  may assist the operation of the steering device  40  in response to a steering intention of the driver through the steering wheel such that the driver may easily operate the steering wheel. For example, the EPS  41  may assist the operation of the steering device  40  such that the steering force is reduced during low-speed travelling or parking and the steering force is increased during high-speed travelling. 
     The BCM  51  may control the operation of machine parts that provide convenience to the driver or ensure the safety of the driver. For example, the BCM  51  may control a head lamp, a wiper, a cluster, a multifunction switch, a direction indicator lamp, and the like. 
     The DAS  100  may assist the driver in manipulating (driving, braking, and steering) the vehicle  1 . For example, the DAS  100  may sense a surrounding environment of the vehicle  1  (e.g., another vehicle, a pedestrian, a cyclist, a lane, a road sign, and the like), and control driving and/or braking and/or steering of the vehicle  1  in response to the sensed environment. 
     The DAS  100  may provide the driver with various functions. For example, the DAS  100  may include a lane departure warning (LDW), a lane keeping assist (LKA), a high beam assist (HBA), an automatic emergency braking (AEB), an autonomous emergency steering (AES), a traffic sign recognition (TSR), a smart cruise control (SCC), a blind spot detection (BSD), and the like. 
     The DAS  100  includes a camera module  101  that obtains image data of the surrounding of the vehicle  1  and a radar module  102  that obtains object data of the surrounding of the vehicle  1 . The camera module  101  may include a camera  101   a  and an electronic control unit (ECU)  101   b , and photograph at least one of the front or the lateral side of the vehicle  1  and recognize another vehicle, a pedestrian, a cyclist, a lane, a road sign, and the like. The radar module  102  may include a radar  102   a  and an ECU  102   b , and obtain a relative position, a relative velocity, and the like of an object of the surrounding of the vehicle  1  (e.g., another vehicle, a pedestrian, a cyclists, and the like). 
     The above described electronic components may communicate with each other through vehicle communication network NT. For example, the machine parts may transmit data through Ethernet, media oriented systems transport (MOST), Flexray, controller area network (CAN), local interconnect network (LIN), and the like. For example, the DAS  100  may transmit a driving control signal, a braking signal, and a steering signal to the EMS  11 , the EBCM  31 , and the EPS  41 , respectively. 
       FIG. 2  is a diagram illustrating a configuration of a driver assistance system according to an embodiment.  FIG. 3  is a diagram illustrating a camera and a radar included in a driver assistance system of a vehicle according to an embodiment. 
     Referring to  FIG. 2 , the vehicle  1  may include a vehicle velocity control system  200 , a braking system  32 , a steering system  300 , and a DAS  100 . 
     The vehicle velocity control system  200  may include at least one component for increasing or decreasing the vehicle velocity of the vehicle  1 . The vehicle velocity control system  200  includes the EBCM ( 31  in  FIG. 1 ) and the braking device ( 30  in  FIG. 1 ) described with reference to  FIG. 1 . In addition, the vehicle velocity control system  200  includes the engine ( 10  in  FIG. 1 ), the EMS ( 11  in  FIG. 1 ), the transmission ( 20  in  FIG. 1 ), and the TCU ( 21  in  FIG. 1 ). 
     The steering system  300  may include the EPS ( 41  in  FIG. 1 ) and the steering device ( 40  in  FIG. 1 ). 
     The DAS  100  may include a front camera  111 , a rear camera  112 , a front radar  120 , a plurality of corner radars  130 , and a rear radar  140 . 
     The front camera  111  may photograph the front of the vehicle  1  and obtain image data of the front of the vehicle  1 . The image data of the front of the vehicle  1  may include position information of another vehicle, a pedestrian, a cyclist, or a lane existing in front of the vehicle  1 . 
     In addition, as shown in  FIG. 3 , the front camera  111  may have a field of view  110   a  and  110   b  facing not only the front of the vehicle  1  but also toward the side of the vehicle  1 . 
     The front camera  111  may obtain external image data around the vehicle  1  including visual information on the side of the vehicle  1  as well as the front of the vehicle  1 . The external image data of the vehicle  1  may include position information about another vehicle, pedestrian, cyclist, or lane located in at least one of the front or side of the vehicle  1 . 
     The front camera  111  may include a plurality of lenses and an image sensor. The image sensor may include a plurality of photodiodes for converting light into electrical signals, and the plurality of photodiodes may be arranged in a two-dimensional matrix. 
     The front camera  111  may be electrically connected to the controller  150 . For example, the front camera  111  may be connected to the controller  150  through a vehicle communication network NT, may be connected to the controller  150  through a hard wire, or may be connected to the controller  150  through a printed circuit board (PCB). 
     The front camera  111  may transmit external image data around the vehicle  1  including at least one of the front or the side of the vehicle  1  to the controller  150 . 
     Meanwhile, the front camera  111  may be installed at a position to have a front view or a side view of the vehicle  1 , and may be installed, for example, on a front windshield of the vehicle  1 . 
     The rear camera  112  may photograph the rear of the vehicle  1  and obtain image data of the rear of the vehicle  1 . The image data of the rear of the vehicle  1  may include position information on another vehicle or pedestrian or cyclist or lane located at the rear of the vehicle  1 . 
     The rear camera  112  may obtain external image data around the vehicle  1  including visual information about the side of the vehicle  1  as well as the rear of the vehicle  1 . The external image data of the vehicle  1  may include position information about another vehicle, a pedestrian, a cyclist, or a lane positioned at least one of the rear or side of the vehicle  1 . 
     To this end, the rear camera  112  may be installed at a position to have a rear view or a side view of the vehicle  1 . For example, it may be installed on the rear windshield of the vehicle  1 . 
     In addition, the description of the front camera  111  described above may be equally applied to the rear camera  112 . 
     The front radar  120  may include a transmission antenna (or a transmission antenna array) that radiates transmission radio waves forward of the vehicle  1  and a reception antenna (or a reception antenna array) that receives reflected radio waves reflected from an object. The front radar  120  may obtain front radar data from the transmission radio waves transmitted by the transmission antenna and the reflected radio waves received by the reception antenna. Front radar data may include distance information and velocity information regarding another vehicle, a pedestrian, or a cyclist existing in front of the vehicle  1 . The front radar  120  may calculate the relative distance to the object on the basis of the phase difference (or time difference) between the transmission radio waves and the reflected radio waves, and calculate the relative velocity of the object on the basis of the frequency difference between the transmission radio waves and the reflected radio waves. 
     The front radar  120  may be connected to the controller  150  through a vehicle communication network NT, a hard wire, or a printed circuit board. The front radar  120  may transmit the front radar data to the controller  150 . 
     The front radar  120  may be installed at a position where information about the front of the vehicle  1  may be obtained, and for example, may be installed on a grille or bumper of the vehicle  1 . 
     The plurality of corner radars  130  includes a first corner radar  131  installed on the front right side of the vehicle  1 , a second corner radar  132  installed on the front left side of the vehicle  1 , a third corner radar  133  installed on the rear right side of the vehicle  1 , and a fourth corner radar  134  installed on the rear left side of the vehicle  1 . 
     The first corner radar  131  may have a field of sensing  131   a  directed toward the front right side of the vehicle  1  as shown in  FIG. 3 . The first corner radar  131  may be installed on the right side of the front bumper of the vehicle  1 , for example. The second corner radar  132  may have a field of sensing  132   a  directed toward the front left side of the vehicle  1 , and may be installed on the left side of the front bumper of the vehicle  1 , for example. The third corner radar  133  may have a field of sensing  133   a  directed toward the rear right side of the vehicle  1  and may be installed on the right side of the rear bumper of the vehicle  1 , for example. The fourth corner radar  134  may have a field of sensing  134   a  directed toward the rear left side of the vehicle  1  and may be installed on the left side of the rear bumper of the vehicle  1 , for example. 
     Each of the first, second, third and fourth corner radars  131 ,  132 ,  133 , and  134  may include a transmission antenna and a reception antenna. The first, second, third, and fourth corner radars  131 ,  132 ,  133  and  134  obtain first corner radar data, second corner radar data, third corner radar data, and fourth corner radar data, respectively. The first corner radar data may include distance information and velocity information regarding another vehicle, a pedestrian, or a cyclist (hereinafter referred to as “an object”) positioned on the front right side of the vehicle  1 . The second corner radar data may include distance information and velocity information regarding an object positioned on the front left side of the vehicle  1 . The third and fourth corner radar data may respectively include distance and velocity information regarding an object located on the rear right side of the vehicle  1  and distance and velocity information regarding an object located on the rear left side of the vehicle  1 . 
     Each of the first, second, third, and fourth corner radars  131 ,  132 ,  133  and  134  may be connected to the controller  150  through a vehicle communication network NT, a hard wire, or a printed circuit board, for example. The first, second, third, and fourth corner radars  131 ,  132 ,  133 , and  134  may respectively transmit the first corner radar data, the second corner radar data, the third corner radar data, and the fourth corner radar data to the controller  150 . 
     The radar  102   a  including the above-described front radar  120  and a plurality of corner radars  130  may transmit front radar data of the front radar  120  and corner radar data of the plurality of corner radars  130  to the controller  150 . 
     The controller  150  may include the ECU ( 101   b  in  FIG. 1 ) of the camera module ( 101  in  FIG. 1 ) and/or the ECU ( 102   b  in  FIG. 1 ) of the radar module ( 102  in  FIG. 1 ), and/or an integrated ECU. 
     The controller  150  includes a processor  151  and a memory  152 . 
     The processor  151  may process the external image data of the front camera  111 , the radar data of the radar  102   a  and the corner radar data of the plurality of corner radars  130 , and generate a driving signal, a braking signal and a steering signal for controlling the vehicle velocity control system  200  and the steering system  42 . For example, the processor  151  may include an image signal processor for processing external image data of the front camera  111  and/or a digital signal processor for processing radar data of the radars  102   a  and/or a micro control unit (MCU) for generating a driving signal, a braking signal and a steering signal. 
     The processor  151  may sense objects (e.g., another vehicle, a pedestrian, a cyclist, and the like) in front of or on the side of the vehicle  1  on the basis of the external image data of the front camera  111  and the front radar data of the front radar  102   a.    
     Specifically, the processor  151  may obtain position information (distance and direction) and velocity information (relative velocity) of objects in front or rear of the vehicle  1  based on the radar data of the radar  102   a . The processor  151  may obtain position information (direction) and type information (eg, whether the object is another vehicle, a pedestrian, or a cyclist) of objects in front or rear of the vehicle  1  based on the external image data of the front camera  111  or the rear camera  112 . In addition, the processor  151  allows the object sensed by the external image data to match the object sensed by the radar data, and obtains the type information, the position information, and the velocity information of the surrounding objects of the vehicle  1  on the basis of a result of the matching. 
     The processor  151  may generate a driving signal, a braking signal, and a steering signal based on type information, position information, and velocity information of surrounding objects. 
     For example, the processor  151  calculates a time to collision TTC between the vehicle  1  and the surrounding object on the basis of the position information (distance) and the velocity information (relative velocity) of the surrounding object, and warns the driver of a collision or transmits a braking signal to the vehicle velocity control system  200  on the basis of a result of comparing the TTC with a predetermined reference time. In response to the TTC less than a predetermined first reference time, the processor  151  may allow an alert to be output via audio and/or display. In response to the TTC less than a predetermined second reference time, the processor  151  may transmit a preliminary-braking signal to the vehicle velocity control system  200 . In response to the TTC less than a predetermined third reference time, the processor  151  may transmit an emergency braking signal to the vehicle velocity control system  200 . In this case, the second reference time is shorter than the first reference time, and the third reference time is shorter than the second reference time. 
     As another example, the processor  151  may calculate a distance to collision (DTC) on the basis of the relative velocity of surrounding objects, and warn the driver of a collision or transmit a braking signal to the vehicle velocity control system  200  on the basis of a result of comparing the DTC with distances to the surrounding objects. 
     The processor  151  may obtain position information (distance and direction) and velocity information (relative velocity) of the objects on the sides of the vehicle  1  (front right, front left, rear right, and rear left) on the basis of corner radar data of the plurality of corner radars  130 . 
     As such, the controller  150  may transmit a control signal to the vehicle velocity control system  200  or the steering system  300  based on whether a collision with a front or side object is predicted. 
     When a collision with a side object is predicted, the controller  150  may perform longitudinal avoidance by transmitting a braking signal to the vehicle velocity control system  200  in order to avoid a collision with the side object. When a collision with a side object is predicted even after transmitting a braking signal for longitudinal avoidance, the controller may perform lateral avoidance by transmitting a steering signal to the steering system  300  in order to avoid collision with a lateral object. 
     In addition, when the side object does not exist or the collision with the side object is not predicted, the controller  150  may transmit a steering signal to the steering system  300  in order to avoid a collision with the front object. When a collision with a side object is predicted after steering, the controller  150  may not transmit a steering signal to the steering system  300 . 
     When a collision with a rear object is predicted, the controller  150  may increase the vehicle velocity by transmitting a driving signal to the vehicle velocity control system  200  in order to avoid a collision with a rear object. That is, the controller  150  may perform longitudinal avoidance with respect to the rear object. When a collision with a lateral object is predicted even after transmitting the driving signal for longitudinal avoidance, the controller  150  may perform lateral avoidance by transmitting a steering signal to the steering system  300  in order to avoid collision with a lateral object. 
     The memory  152  stores programs and/or data for processing image data by the processor  151 , programs and/or data for processing radar data by the processor  151 , and programs and/or data for generating a driving signal, a braking signal and/or a steering signal by the processor  151 . 
     The memory  152  may temporarily store the image data received from the front camera  111  or the rear camera  112  and/or the radar data received from the radars  120 ,  130  and  140 , and may temporarily store a result of processing the image data and/or the radar data of the processor  151 . 
     The memory  152  may include a volatile memory, such as an S-RAM, a D-RAM, and the like, and a non-volatile memory, such as a flash memory, a read only memory (ROM), an erasable programmable read only memory (EPROM), and the like. 
     At least one component may be added or deleted corresponding to the performance of the components of the vehicle  1  shown in  FIGS. 1 and 2 . In addition, it will be readily understood by those of ordinary skill in the art that the mutual positions of the components may be changed corresponding to the performance or structure of the system. 
     Meanwhile, each of the components shown in  FIGS. 1 and 2  refers to software and/or hardware components such as a Field Programmable Gate Array (FPGA) and an Application Specific Integrated Circuit (ASIC). 
       FIG. 4  illustrates a camera and a radar included in a conventional driver assistance system. 
     Referring to  FIG. 4 , the front camera  110 ′ included in the conventional DAS may have a field of view  110   a ′ facing the front of the vehicle  1 ′. 
     Further, the front radar  120   may have a field of sensing  120   a ′ facing the front of the vehicle  1 ′ as shown in  FIG. 4 . 
     However, the field of view angles  110   a ′ and  120   a ′ of the front camera  110 ′ or the front radar  120 ′ are limited to the front. Accordingly, it is difficult to obtain information on surrounding objects located outside the range of the limited field of view angles  110   a ′ and  120   a′.    
     For example, when a rear vehicle located at a close distance from vehicle  1 ′ approaches vehicle  1 ′ to the extent that there is a risk of collision, the vehicle joining in such a short distance may not be detected due to the limited field of view angles  110   a ′ and  120   a ′. Therefore, it is important to prevent collisions with surrounding objects located outside the range of these limited field of view angles  110   a ′ and  120   a′.    
     Hereinafter, the operation of the DAS  100  according to an embodiment for preventing a collision with a rear vehicle by preventing collision due to the limited field of view angle  110   a ′,  120   a ′ of the conventional DAS described above, and by detecting the rear vehicle more quickly will be described in detail. 
       FIGS. 5 to 9  are diagrams for illustrating an operation for avoiding a collision with a nearby object by the driver assistance system according to an embodiment. 
     Referring to  FIG. 5 , a rear vehicle  2  may be located in a driving lane L 2  of a vehicle  1  equipped with a DAS  100  according to an embodiment. 
     The controller  150  may determine whether the rear vehicle  2  changes direction based on at least one of image data obtained by the camera  101   a  or radar data obtained by the radar  102   a.    
     For example, the controller  150  may detect an on state or an off state of the direction indicator of the rear vehicle  2  based on image data on the rear of the vehicle  1  obtained by the rear camera  112 . When the direction indicator of the rear vehicle  2  is off state, the controller  150  may determine that the rear vehicle  2  does not change direction. When the direction indicator of the rear vehicle  2  is on state, the controller  150  may determine that the rear vehicle  2  changes direction. 
     As another example, the controller  150  may detect a lateral movement of the rear vehicle  2  based on radar data obtained by the rear radar  140 . When the rear vehicle  2  maintains a predetermined lateral distance to both lines forming the driving lane L 2 , the controller  150  may determine that the rear vehicle  2  does not change direction. The controller  150  may determine that the rear vehicle  2  changes direction when the rear vehicle  2  approaches a specific line within a predetermined range. 
     In addition to the above-described example, the controller  150  may utilize image data by the front camera  111 , and may determine whether to change the direction of the rear vehicle  2  by using radar data obtained by the front radar  120  or the plurality of corner radars  130 . Description of this is the same as the description of the above-described example. 
     When it is determined that the rear vehicle  2  does not change direction, the controller  150  may determine whether there is a risk of collision with the rear vehicle  2 . 
     Specifically, the controller  150  may determine whether there is a risk of collision with the rear vehicle  2  based on at least one of image data obtained by the rear camera  112  or radar data obtained by the rear radar  140 . 
     For example, the controller  150  may detect the relative velocity of the rear vehicle  2  based on radar data obtained by the rear radar  140 . When the relative velocity of the rear vehicle  2  is more than or equal to a predetermined velocity threshold, the controller  150  may determine that there is a risk of collision with the rear vehicle  2 . 
     As another example, the controller  150  may detect a distance to the rear vehicle  2  based on radar data obtained by the rear radar  140 . When the distance between the rear vehicle  2  and vehicle  1  is less than or equal to a predetermined distance, the controller  150  may determine that there is a risk of collision with the rear vehicle  2 . 
     As another example, the controller  150  may detect the size of the rear vehicle  2  based on image data obtained by the rear camera  112 . When the size of the rear vehicle  2  is larger than or equal to a predetermined size, the controller  150  may determine that there is a risk of collision with the rear vehicle  2 . 
     In addition to the above-described example, the controller  150  may obtain various parameters necessary to determine the collision risk such as the position, distance, velocity, or relative velocity of the rear vehicle  2  based on the rear camera  112  or rear radar  140 . And determining whether there is a risk of collision based on these various parameters may be variously changed or substituted at the level of ordinary skill. 
     When it is determined that there is a risk of collision with the rear vehicle  2 , the controller  150  may identify an avoidance space (free space) for avoiding a collision with the rear vehicle  2  based on at least one of image data or radar data. The controller  150  may control at least one of the vehicle velocity control system  200  or the steering system  300  of the vehicle  1  so that the vehicle  1  moves to the identified avoidance space. 
     Image data used to identify the avoidance space may be obtained by at least one of the front camera  111  or the rear camera  112 , radar data used to identify the avoidance space may be obtained by at least one of the front radar  120 , the plurality of corner radars  130 , and the rear radar  140 . 
     For example, if the avoidance space S exists in the adjacent lane L 1  of the driving lane L 2 , the controller  150  may control at least one of the vehicle velocity control system  200  or the steering system  300  so that the vehicle  1  moves to a position  1 ′ corresponding to the avoidance space S. 
     As another example, as shown in  FIG. 6 , when the avoidance space S′ exists in the driving lane L 2 , the controller  150  may control the vehicle to move to a position  1 ″ corresponding to the avoidance space S′. 
     Specifically, the controller  150  may allow the relative position of the vehicle  1  with respect to the rear vehicle  2  to move forward by transmitting a drive signal to the engine management system  11  or the transmission control unit  21  to increase the vehicle speed. 
     Through this, an unexpected collision with the rear vehicle may be prevented, so that user convenience and safety may be increased. 
     On the other hand, when there are multiple lanes, a case in which a plurality of avoidance spaces may be identified may occur. 
     As shown in  FIG. 7 , when the first avoidance space S 1  present in the driving lane L 2  and the second avoidance space S 2  present in the adjacent lane L 3  are identified, the controller  150  may select one avoidance space from among a plurality of avoidance spaces. 
     Specifically, the controller  150  may select one of a plurality of avoidance spaces based on detection information obtained based on at least one of image data or radar data. 
     In this case, the detection information means information obtained by the camera  102   a  or the radar  102   a  to determine the driving environment of the vehicle  1 , and may include information on objects located around the vehicle  1 . The detection information may include information related to driving, such as relative velocity, distance, and location of the preceding vehicle  3 ,  4  and  5  or the following vehicle  2 . Such detection information may be obtained by at least one of the front camera  111 , the rear camera  112 , the front radar  120 , a plurality of corner radars  130 , and the rear radar  140 . 
     For example, detection information may include at least one of the size of the identified avoidance space, the distance between the preceding vehicle  3 ,  4  and  5  and vehicle  1 , the relative velocity of the preceding vehicle  3 ,  4  and  5 , the distance between the vehicles  1  and the rear vehicle  2  and the relative velocity of the rear vehicle  2 . 
     However, in the example of  FIG. 7 , a plurality of preceding vehicles and one rear vehicle have been described as an example, but the present disclosure is not limited thereto, and detection information may include information on at least one preceding vehicle or at least one rear vehicle. 
     The controller  150  may select an avoidance space having the largest avoidance space among a plurality of avoidance spaces, and may control at least one of the vehicle velocity control system  200  or the steering system  300  so that the vehicle  1  moves to the largest avoidance space. 
     The controller  150  may select a second avoidance space S 2  having a larger size among the first avoidance space S 1  located in the driving lane L 2  and the second avoidance space S 2  located in the adjacent lane L 3 , and may control at least one of the vehicle velocity control system  200  or the steering system  300  so that the vehicle  1  moves to the position  1   a  corresponding to the second avoidance space S 2 . 
     In addition, as another example, as shown in  FIG. 8 , the controller  150  may select an avoidance space having the smallest relative velocity of the rear vehicle  2 ,  3  and  4  among a plurality of avoidance spaces, and may control at least one of the vehicle velocity control system  200  or the steering system  300  so that the vehicle  1  moves to the selected avoidance space. 
     When the first avoidance space S 1 ′, the second avoidance space S 2 ′, and the third avoidance space S 3 ′ are identified and the relative velocity of the rear vehicle  4  located in the lane L 3  where the third avoidance space S 3 ′ exists is the lowest, the controller  150  may select a third avoidance space S 3 ′. The controller  150  may control at least one of the vehicle velocity control system  200  or the steering system  300  so that the vehicle  1  moves to a position  1   a ′ corresponding to the third avoidance space S 3 ′. 
     The controller  150  may determine the priority of each of the above-described detection information, and may select one avoidance space from among a plurality of avoidance spaces based on the determined priority. 
     Specifically, the controller  150  may determine the priority of each detection information based on the collision probability. To this end, the controller  150  may calculate a collision probability with the rear vehicle  2  located on the driving road based on image data or radar data. Alternatively, the priority of each detection information may be determined in advance, and may be stored in the memory  152 . Alternatively, the priority of each detection information may be input from a user through an input device (not shown), and may be received from an external device through a communication device (not shown). 
     For example, the controller  150  may preferentially consider the size of the avoidance space in selecting the avoidance space and then utilize the relative velocity of the rear vehicle. 
     Through this, since it is possible to more safely avoid a collision with the rear vehicle in consideration of the preceding vehicle, the user&#39;s convenience and safety may be increased. 
     Meanwhile, in controlling the vehicle  1  to move to the avoidance space, when the avoidance space exists in the adjacent lane of the driving lane, the behavior of the rear vehicle driving in the adjacent lane may also greatly affect the safety of the user. 
     As shown in  FIG. 9 , when the avoidance space is located in the adjacent lane L 1  of the driving lane L 2 , the controller  150  may control movement to the avoidance space based on the behavior of the rear vehicle  3  driving in the adjacent lane L 1 . 
     Specifically, the controller  150  may obtain the relative velocity of the rear vehicle  3  driving in the adjacent lane L 1  based on image data or radar data. When the relative velocity of the rear vehicle  3  located in the adjacent lane L 1  is more than or equal to a predetermined threshold, the controller  150  may control at least one of the vehicle velocity control system  200  or the steering system  300  so that the vehicle  1  moves to the avoidance space after the rear vehicle  3  passes the vehicle  1 . 
     That is, the controller  150  may determine a steering time point (the steering time point includes a lane change time point) according to the relative velocity of the rear vehicle  3  driving in the adjacent lane L 1  where the avoidance space exists, and may control at least one of the vehicle velocity control system  200  or the steering system  300  so that the vehicle  1  moves based on the determined steering time point. 
     Through this, the controller  150  may avoid a collision with the rear vehicle  2  located on the driving road L 2  as well as avoid a collision with the rear vehicle  3  located in the avoidance space. Therefore, user convenience and safety may be increased. 
       FIG. 10  is flowchart illustrating a control method of a driver assistance system according to an embodiment. 
     Referring to  FIG. 10 , the DAS  100  according to an embodiment may obtain detection information ( 911 ). 
     In this case, the detection information means information obtained by the camera  102   a  or the radar  102   a  to determine the driving environment of the vehicle  1 , and may include information on objects located around the vehicle  1 . The detection information may include information related to driving, such as relative velocity, distance, and location of the preceding vehicle or the following vehicle. Such detection information may be obtained by at least one of the front camera  111 , the rear camera  112 , the front radar  120 , a plurality of corner radars  130 , and the rear radar  140 . 
     The DAS  100  may confirm whether or not a direction change of the rear vehicle is detected based on the detection information ( 912 ). In this case, the rear vehicle means a rear vehicle located on the same driving road as vehicle  1 . 
     For example, the DAS  100  may detect an on state or an off state of the direction indicator of the rear vehicle  2  based on image data on the rear of the vehicle  1  obtained by the rear camera  112 . When the direction indicator of the rear vehicle  2  is off state, the DAS  100  may determine that the rear vehicle  2  does not change direction. When the direction indicator of the rear vehicle  2  is on state, the DAS  100  may determine that the rear vehicle  2  changes direction. 
     As another example, the DAS  100  may detect a lateral movement of the rear vehicle  2  based on radar data obtained by the rear radar  140 . When the rear vehicle  2  maintains a predetermined lateral distance to both lines forming the driving lane L 2 , the DAS  100  may determine that the rear vehicle  2  does not change direction. The DAS  100  may determine that the rear vehicle  2  changes direction when the rear vehicle  2  approaches a specific line within a predetermined range. 
     In addition to the above-described example, the DAS  100  may utilize image data by the front camera  111 , and may determine whether to change the direction of the rear vehicle  2  by using radar data obtained by the front radar  120  or the plurality of corner radars  130 . Description of this is the same as the description of the above-described example. 
     When the direction change of the rear vehicle is not detected (NO in  912 ), the DAS  100  may confirm whether there is a risk of collision with the rear vehicle ( 913 ). 
     Specifically, the DAS  100  may determine whether there is a risk of collision with the rear vehicle  2  based on at least one of image data obtained by the rear camera  112  or radar data obtained by the rear radar  140 . 
     For example, the DAS  100  may detect the relative velocity of the rear vehicle  2  based on radar data obtained by the rear radar  140 . When the relative velocity of the rear vehicle  2  is more than or equal to a predetermined velocity threshold, the DAS  100  may determine that there is a risk of collision with the rear vehicle  2 . 
     As another example, the DAS  100  may detect a distance to the rear vehicle  2  based on radar data obtained by the rear radar  140 . When the distance between the rear vehicle  2  and vehicle  1  is less than or equal to a predetermined distance, the DAS  100  may determine that there is a risk of collision with the rear vehicle  2 . 
     As another example, the DAS  100  may detect the size of the rear vehicle  2  based on image data obtained by the rear camera  112 . When the size of the rear vehicle  2  is larger than or equal to a predetermined size, the DAS  100  may determine that there is a risk of collision with the rear vehicle  2 . 
     In addition to the above-described example, the DAS  100  may obtain various parameters necessary to determine the collision risk such as the position, distance, velocity, or relative velocity of the rear vehicle  2  based on the rear camera  112  or rear radar  140 . And determining whether there is a risk of collision based on these various parameters may be variously changed or substituted at the level of ordinary skill. 
     When there is a risk of collision with a rear vehicle (YES in  913 ), the DAS  100  may confirm whether an avoidance space (free space) exists based on detection information ( 914 ). To this end, the DAS  100  may identify an avoidance space for avoiding a collision with the rear vehicle  2  based on at least one of image data or radar data included in detection information. 
     When there is an avoidance space (YES in  914 ), the DAS  100  may perform steering control or velocity control based on the avoidance space ( 915 ). Specifically, the DAS  100  may control the steering system  300  or the vehicle velocity control system  200  so that the vehicle  1  moves to a position corresponding to the avoidance space. 
     Through this, it is possible to provide information on an accurate position or expected behavior of an object around the vehicle, particularly an object present at the rear of the vehicle, thereby preventing an unexpected collision. Accordingly, user convenience and driving safety may be increased. 
       FIG. 11  is flowchart illustrating a control method of a driver assistance system according to an embodiment. 
     Referring to  FIG. 11 , the DAS  100  according to an embodiment may obtain detection information ( 921 ), and confirm whether a rear vehicle direction change is detected based on the detection information ( 922 ). 
     When it is determined that the rear vehicle does not change direction (YES in  922 ), the DAS  100  may confirm whether there is a risk of collision with the rear vehicle ( 923 ). When there is a risk of collision with the rear vehicle (YES in  923 ), the DAS  100  may confirm whether an avoidance space exists ( 924 ). 
     In this case, the descriptions of steps  911  to  914  of  FIG. 10  described above may be equally applied to each of steps  921  to  924 . 
     When there is an avoidance space ( 924 ), the DAS  100  may confirm whether a plurality of avoidance spaces exist ( 925 ). When a plurality of avoidance spaces exist (YES in  925 ), the DAS  100  may select one of the plurality of avoidance spaces based on detection information ( 926 ). 
     The detection information may include at least one of the size of the identified avoidance space, the distance between the preceding vehicle and vehicle  1 , the velocity of the preceding vehicle, the distance between the vehicles  1  and the rear vehicle and the velocity of the rear vehicle. 
     The DAS  100  may select an avoidance space having the largest avoidance space among a plurality of avoidance spaces, and may control at least one of the vehicle velocity control system  200  or the steering system  300  so that the vehicle  1  moves to the largest avoidance space. 
     In addition, as another example, the DAS  100  may select an avoidance space having the smallest relative velocity of the rear vehicle among a plurality of avoidance spaces, and may control at least one of the vehicle velocity control system  200  or the steering system  300  so that the vehicle  1  moves to the selected avoidance space. 
     The DAS  100  may determine the priority of each of the above-described detection information, and may select one avoidance space from among a plurality of avoidance spaces based on the determined priority. 
     Specifically, the DAS  100  may determine the priority of each detection information based on the collision probability. To this end, the DAS  100  may calculate a collision probability with the rear vehicle  2  located on the driving road based on image data or radar data. Alternatively, the priority of each detection information may be determined in advance, and may be stored in the memory  152 . Alternatively, the priority of each detection information may be input from a user through an input device (not shown), and may be received from an external device through a communication device (not shown). 
     For example, the DAS  100  may preferentially consider the size of the avoidance space in selecting the avoidance space and then utilize the relative velocity of the rear vehicle. 
     Through this, since it is possible to more safely avoid a collision with the rear vehicle in consideration of the preceding vehicle, the user&#39;s convenience and safety may be increased. 
     Meanwhile, the disclosed embodiments may be implemented in the form of a recording medium storing instructions that are executable by a computer. The instructions may be stored in the form of a program code, and when executed by a processor, the instructions may generate a program module to perform operations of the disclosed embodiments. The recording medium may be implemented as a computer-readable recording medium. 
     The computer-readable recording medium may include all kinds of recording media storing commands that may be interpreted by a computer. For example, the computer-readable recording medium may be ROM, RAM, a magnetic tape, a magnetic disc, flash memory, an optical data storage device, etc. 
     The exemplary embodiments of the disclosure have thus far been described with reference to the accompanying drawings. It will be obvious to those of ordinary skill in the art that the disclosure may be practiced in other forms than the exemplary embodiments as described above without changing the technical idea or essential features of the disclosure. The above exemplary embodiments are only by way of example, and should not be interpreted in a limited sense. 
     According to a driver assistance system and a control method thereof according to an aspect, information on an accurate location or expected behavior of an object around a vehicle, particularly an object existing at the rear of the vehicle, may be provided, thereby preventing unexpected collisions. Accordingly, user convenience and driving safety may be increased.