Patent Publication Number: US-2021179093-A1

Title: Driving support apparatus

Description:
TECHNICAL FIELD 
     The present invention relates to a driving support apparatus capable of performing collision avoidance braking control and lane deviation suppressing control. 
     BACKGROUND ART 
     A driving support apparatus capable of performing collision avoidance braking control and lane deviation suppressing control as driving support control has been conventionally known. The collision avoidance braking control is control for automatically applying braking force to an own vehicle when a three-dimensional object with a high probability of the own vehicle colliding with has been detected in front of the own vehicle by means of sensors such as a camera and/or a radar etc. (hereinafter, such a three-dimensional object may be also referred to as a “target object”) (for example, refer to Japanese Patent Application Laid-Open (kokai) No. 2012-116403). 
     On the other hand, the lane deviation suppressing control is control for detecting a lane (hereinafter, may be also referred to as a “travelling lane”) on which the own vehicle is travelling by means of the camera and automatically change a steered angle of each of steered wheels of the own vehicle so that the own vehicle travels in (within) the travelling lane along the travelling lane when it is highly likely that the own vehicle deviates from the travelling lane or when the own vehicle has already deviated from the travelling lane (for example, refer to Japanese Patent Application Laid-Open (kokai) No. 2014-142965). 
     SUMMARY OF THE INVENTION 
     The collision avoidance braking control and the lane deviation suppressing control are independent controls with each other and are performed when each of performing conditions thereof has been satisfied. Therefore, when a performing condition of one control has been satisfied in a midst of the other control being performed after a performing condition thereof is satisfied (strictly, including a case when the performing conditions of both of the controls have been satisfied at the same time), one control is performed in addition to the other control. In this case, depending on a positional relationship between a target object and the travelling lane, there may be a case where the steered wheels are steered by the lane deviation suppressing control in such a manner that the own vehicle travels along the travelling lane, and as a result, the own vehicle travels toward the target object, causing to reduce collision avoidance effect by the collision avoidance braking control. 
     Hence, this type of driving support apparatus may be configured to stop (prohibit) the lane deviation suppressing control and perform the collision avoidance braking control under a situation where both of the lane deviation suppressing control and the collision avoidance braking control may be performed. According to such a driving support apparatus, the lane deviation suppressing control will not be performed while the collision avoidance braking control is being performed, and thus it can be suppressed that the collision avoidance effect reduces due to the lane deviation suppressing control. 
     However, depending on the positional relationship between a target object and a lane, there also may be a case where the collision avoidance effect improves when the lane deviation suppressing control is performed in combination with the collision avoidance braking control. The driving support apparatus mentioned above stops (prohibits) the lane deviation suppressing control even in such a case, and therefore it is impossible to make use of the lane deviation suppressing control in order to improve the collision avoidance effect. 
     The present invention is made to resolve the problem above. That is, one of objects of the present invention is to provide, for a driving support apparatus capable of performing collision avoidance braking control and lane deviation suppressing control, technique capable of make the lane deviation suppressing control properly cooperate with the collision avoidance braking control. 
     A driving support apparatus (hereinafter, referred to as a “present invention apparatus”) comprising: 
     an object information acquiring apparatus ( 11 ) configured to detect a three-dimensional object present in front of an own vehicle and a lane on which the own vehicle is travelling and to acquire information indicating the detected three-dimensional object and lane as object information; and 
     a controller ( 10 ) configured to perform collision avoidance braking control for automatically applying braking force to the own vehicle when it is determined, based on the object information, that the own vehicle is highly likely to collide with the detected three-dimensional object (S 530 : Yes) and lane deviation suppressing control for automatically changing a steered angle of steered wheels of the own vehicle such that the own vehicle travels in the lane when a deviation suppressing control performing condition is satisfied, the deviation suppressing control performing condition being a condition satisfied when it is determined, based on the object information, that the own vehicle is highly likely to deviate from the detected lane (w/2&lt;Ds&lt;Dsth) and/or a condition satisfied when it is determined, based on the object information, that the own vehicle has deviated from the detected lane (Ds≤w/2), 
     wherein, 
     the controller ( 10 ) is configured to:
         when the deviation suppressing control performing condition is satisfied (S 535 : Yes) in a case when it is determined that the own vehicle is highly likely to collide with the detected three-dimensional object (S 530 : Yes), execute direction determination processing (S 545 ) for determining whether or not a steered direction of the steered wheels by the lane deviation suppressing control is same as a collision avoidance direction toward which the own vehicle will avoid colliding with the three-dimensional object,   when it is determined that the steered direction is different from the collision avoidance direction (S 545 : No), stop the lane deviation suppressing control (S 550 ) and perform the collision avoidance braking control (S 540 ), and   when it is determined that the steered direction is same as the collision avoidance direction (S 545 : Yes), perform both of the collision avoidance braking control and the lane deviation suppressing control (S 540 ).       

     In the present invention apparatus, when the deviation suppressing control performing condition is satisfied in a case when it is determined that the own vehicle is highly likely to collide with the three-dimensional object detected by the object information acquiring apparatus (in other words, a case when the collision avoidance braking control is about to be performed), the direction determination processing is executed by the controller. The direction determination processing is processing for determining, provided that steered wheels are turned by the lane deviation suppressing control, whether or not the steered direction is same as a collision avoidance direction (a direction toward which the own vehicle will avoid colliding with the detected three-dimensional object). 
     Here, “the steered direction is different from the collision avoidance direction” in the present specification means that “provided that the steered wheels are turned by the lane deviation suppressing control, the own vehicle travels to a direction toward which the own vehicle will collide with the target object (hereinafter, may be also referred to as a “collision direction”)”. Therefore, when the steered direction is different from the collision avoidance direction, it is highly likely that the collision avoidance effect is reduced owing to the lane deviation suppressing control. According to the present invention apparatus, in such a case, the lane deviation suppressing control is stopped and the collision avoidance braking control is performed. Hence, it can be suppressed that the collision avoidance effect is reduced owing to the lane deviation suppressing control. 
     In addition, “the steered direction is same as the collision avoidance direction” in the present specification means that “provided that the steered wheels are turned by the lane deviation suppressing control, the own vehicle travels to the collision avoidance direction”. Therefore, when the steered direction is same as the collision avoidance direction, it is highly likely that the collision avoidance effect is improved thanks to the lane deviation suppressing control. According to the present invention apparatus, in such a case, both of the collision avoidance braking control and the lane deviation suppressing control are performed. Therefore, the collision avoidance effect can be improved thanks to the lane deviation suppressing control. 
     As mentioned above, according to the present invention apparatus, it becomes possible to make the lane deviation suppressing control properly cooperate with the collision avoidance braking control based on the direction determination processing. 
     Another aspect of the present invention further comprising a steering index value detector ( 12 ) for detecting steering related values (θs, ωs) having correlation with force input to a steering wheel by a driver of the own vehicle, 
     wherein, 
     the controller ( 10 ) is configured to, when a steering override condition where the steering related values (θs, ωs) are more than or equal to predetermined steering related thresholds (θsth, ωsth) while the collision avoidance breaking control and/or the lane deviation suppressing control are/is being performed becomes satisfied, perform steering override for finishing the corresponding collision avoidance braking control and/or lane deviation suppressing control to prioritize steering operation by the driver, 
     the controller further sets the steering related thresholds (θsth, ωsth) to first steering related thresholds (θs1th, ωs1th), and 
     when it is determined in the direction determination processing that the steered direction is same as the collision avoidance direction (S 545 : Yes), the controller is configured to change (S 560 ) the steering related thresholds (θsth, ωsth) to second steering related thresholds (θs2th, ωs2th) larger than the first steering related thresholds (θs1th, ωs1th). 
     When it is determined in the direction determination processing that the steered direction is the same as the collision avoidance direction, the lane deviation suppressing control is cooperatively performed with the collision avoidance braking control, and thus the steered wheels are steered. When the steered wheels are turned, the driver tends to rotate (operate) the steering wheel to a direction corresponding to the steered direction of the steered wheels in order to avoid colliding with the target object. In this case, if the steering related thresholds remain as the first steering related thresholds, the steering override condition may become satisfied by the steering operation by the driver, and as a result, the collision avoidance braking control and the lane deviation suppressing control may be finished halfway (in the middle). In such a case, if the steering operation by the driver is insufficient, a possibility that the own vehicle cannot avoid the collision with the target object becomes high, and thus it is likely that the collision avoidance effect by the collision avoidance braking control and the lane deviation suppressing control cannot be adequately obtained. 
     Therefore, in another aspect of the present invention, when it is determined in the direction determination processing that the steered direction is the same as the collision avoidance direction, the steering related thresholds are increased from the first steering related thresholds to the second steering related thresholds. Accordingly, the steering override condition becomes harder to be satisfied even when the driver conducts the steering operation, and the collision avoidance braking control and the lane deviation suppressing control are highly likely to be performed to the end. Therefore, it can be suppressed that the collision avoidance effect is reduced owing to the steering operation by the driver. 
     In another aspect of the present invention, 
     the controller ( 10 ) is configured to, in the direction determination processing:
         determine, based on the object information, whether or not the detected three-dimensional object is positioned in the detected lane,   when it is determined that the detected three-dimensional object is positioned in the lane (S 545 : No), determine that the steered direction is different from the collision avoidance direction, and   when it is determined that the detected three-dimensional object is positioned outside the lane (S 545 : Yes), determine that the steered direction is same as the collision avoidance direction.       

     When the target object is positioned in the lane, there is a possibility that the own vehicle travels to the collision direction if the lane deviation suppressing control is performed. Therefore, in another aspect of the present invention, when it is determined in the direction determination processing that the target object is positioned in the lane, it is determined that the steered direction is different from the collision avoidance direction. That is, the lane deviation suppressing control is stopped and the collision avoidance braking control is performed. On the other hand, when the target object is positioned outside the lane, the own vehicle is highly likely to travel to the collision avoidance direction if the lane deviation suppressing control is performed. Therefore, in another aspect of the present invention, when it is determined in the direction determination processing that the target object is positioned outside the lane, it is determined that the steered direction is same as the collision avoidance direction. That is, the lane deviation suppressing control is cooperatively performed with the collision avoidance braking control. As described above, the direction determination processing is executed by determining whether or not the steered direction is the same as the collision avoidance direction based on the determination result of whether or not the target object is positioned in the lane. Therefore, the direction determination processing can be properly executed. 
     In addition, whether or not the target object is positioned in the lane can be precisely determined based on the object information. Therefore, the direction determination processing can be executed based on a clear criterion. 
     In the above description, references used in the following descriptions regarding embodiments are added with parentheses to the elements of the present invention, in order to assist in understanding the present invention. However, those references should not be used to limit the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic configuration diagram of a driving support apparatus according to an embodiment of the present invention. 
         FIG. 2  is a plan view showing a left white line LL, a right white line LR, a side distance Ds, and a yaw angle θy when lane deviation suppressing control is performed. 
         FIG. 3  is a graph showing a target steered angle conversion map regulating a relationship between a target lateral acceleration Gy and a target steered angle θtgt. 
         FIG. 4A  is a diagram used to describe about a direction determination when a target object is positioned in a lane. 
         FIG. 4B  is a diagram used to describe about the direction determination when the target object is positioned outside the lane. 
         FIG. 5  is a flowchart showing a routine executed by CPU of driving support ECU of the driving support apparatus. 
         FIG. 6  is a flowchart showing a routine executed by the CPU. 
         FIG. 7  is a flowchart showing a routine executed by the CPU. 
         FIG. 8  is a diagram used to describe an effect brought by cooperative control. 
         FIG. 9  is a diagram used to describe an effect brought by the cooperative control. 
     
    
    
     DESCRIPTION OF THE EMBODIMENT 
     A driving support apparatus according to an embodiment of the present invention (hereinafter, may be also referred to as a “present embodiment apparatus”) will be described below, referring to figures. As shown in  FIG. 1 , the present embodiment apparatus comprises driving support ECU  10 , brake ECU  20 , steering ECU  30 , and warning ECU  40 . Each of the ECUs  10 ,  20 ,  30 , and  40  comprises a microcomputer as a main component and is connected to each other in such a manner that they can mutually exchange data (communicate) via a non-illustrated CAN (Controller Area Network). It should be noted that ECU is an abbreviation of Electronic Control Unit. The microcomputer includes CPU, ROM, RAM, interfaces, and the like. The CPU realizes (performs) various functions (mentioned later) by executing instructions (i.e. programs, routines) stored in the ROM. Some of or all of the ECUs  10 ,  20 ,  30 , and  40  may be integrated to one ECU as a controller. Hereinafter, a vehicle to which the present embodiment apparatus is applied may be referred to as an “own vehicle”. 
     The driving support ECU  10  is connected to a surrounding sensor  11 , a steering angle sensor  12 , a yaw rate sensor  13 , a vehicle speed sensor  14 , and an acceleration sensor  15 , and is configured to receive an output signal and a detection signal from each of these sensors every time a predetermined interval elapses. Hereinafter, the driving support ECU may be also simply referred to as “ECU  10 ”. 
     The surrounding sensor  11  has function for acquiring information at least on “a road in front of the own vehicle and a three-dimensional object(s) present on the road”. The three-dimensional object includes a moving object (a vehicle, a pedestrian, a bicycle, and the like) and a fixed object (a guardrail, a sidewall, a medial divider, a street tree, and the like). 
     The surrounding sensor  11  comprises a radar sensor and a camera sensor. The radar sensor emits an electric wave in a millimeter waveband to a surrounding of the own vehicle (including at least a front region thereof), and when a three-dimensional object exists, receives a reflected wave from this three-dimensional object, and calculates, based on an emitting timing and a receiving timing of the electric wave, and the like, whether or not a three-dimensional object exists and a relative relationship between the own vehicle and the three-dimensional object (a distance from the own vehicle to the three-dimensional object, a direction of the three-dimensional object with respect to the own vehicle, a relative speed of the three-dimensional object with respect to the own vehicle, and the like). The camera sensor comprises a stereo camera. The camera sensor takes an image of scenery of a left side region and a right side region in front of the own vehicle and calculates, based on left and right image data captured, a shape of a road (includes a curvature of the road), whether or not a three-dimensional object exists, and a relative relationship between the own vehicle and the three-dimensional object. The camera sensor recognizes, based on the image data mentioned above, a lane marker including left and right white lines of a road. A shape of a road can be calculated based on this lane marker. That is, the surrounding sensor  11  detects a three-dimensional object present in front of the own vehicle as well as a lane(s) (a region(s) defined by the left and right white lines). It should be noted that the lane detected by the surrounding sensor  11  also includes a lane on which the own vehicle is travelling (travelling lane). The surrounding sensor  11  corresponds to one example of an “object information acquiring apparatus”. 
     The information acquired by the surrounding sensor  11  may be referred to as object information. The surrounding sensor  11  transmits the object information to the ECU  10 . It should be noted that the surrounding sensor  11  does not necessarily have to comprise the radar sensor as well as the camera sensor. For example, the surrounding sensor  11  may comprise only the camera sensor. The camera sensor may be a monocular (single-lens) camera. In addition, the information on a shape of a road may be acquired by means of navigation system (illustration omitted). 
     The steering angle sensor  12  detects a steering angle of a steering wheel of the own vehicle (in other words, a rotation angle of a steering shaft to which the steering wheel is directly connected) and transmits a detection signal to the ECU  10 . The yaw rate sensor  13  detects a yaw rate of the own vehicle and transmits a detection signal to the ECU  10 . The vehicle speed sensor  14  detects a travelling speed of the own vehicle (hereinafter, referred to as a “vehicle speed”) and transmits a detection signal to the ECU  10 . The acceleration sensor  15  detects a front-rear acceleration which is an acceleration acting in a front-rear direction of the own vehicle as well as a lateral acceleration which is an acceleration acting in a left-right direction of the own vehicle (a vehicle width direction), and transmits those detection signals to the ECU  10 . It should be noted that the vehicle speed sensor  14  calculates a vehicle speed based on a count value calculated by counting a number of pulse signals of a wheel speed sensor provided at each of wheels of the own vehicle, and thus the signal of the wheel speed sensor instead of the vehicle speed sensor  14  may be transmitted to the ECU  10 . The steering angle sensor  12  corresponds to one example of a “steering index value detector”. 
     The brake ECU  20  is connected to a brake actuator  21 . The brake actuator  21  is provided in a hydraulic circuit between a non-illustrated master cylinder to compress operating fluid with a pedaling force of a brake pedal and a friction brake mechanism  22  provided at each wheel. Each of the friction brake mechanisms  22  comprises a brake disc  22   a  fixed to the wheel and a brake caliper  22   b  fixed to a vehicle body. Each of the friction brake mechanisms  22  operates a wheel cylinder which is built in the brake caliper  22   b  by a hydraulic pressure of the operating fluid that is supplied from the brake actuator  21 , and thereby presses a brake pad onto the brake disc  22   a  to generate friction braking force. 
     The ECU  10  is configured to be capable of transmitting a braking instruction (described later) to the brake ECU  20 . When receiving the braking instruction, the brake ECU  20  drives (controls) the brake actuator  21  in response to this instruction. Accordingly, the ECU  10  can automatically applying the braking force to the own vehicle via the brake ECU  20 . 
     The steering ECU  30  is a control apparatus of a well-known electrically-driven power steering system and is connected to a motor driver  31 . The motor driver  31  is connected to a steered motor  32 . The steered motor  32  is incorporated into a steering mechanism (illustration omitted). The steered motor  32  generates torque with electric power supplied from the motor driver  31  and with the torque, can generate steering assist torque or can turn left-and-right steered wheels. 
     Specifically, the steering ECU  30  drives the steered motor  32  based on steering torque detected by steering operation (operation of the steering wheel) by a driver, and thereby applies the steering assist torque to the steering mechanism to assist the driver in the steering operation. 
     In addition, the ECU  10  is configured to be capable of transmitting a steering instruction (described later) to the steering ECU  30 . When receiving the steering instruction, the steering ECU  30  drives (controls) the steered motor  32  in response to this instruction. Accordingly, the ECU  10  can automatically change the steered angle of the steered wheel via the steering ECU  30  (that is, without the steering operation by the driver). 
     The warning ECU  40  is connected to a buzzer  41  and a display  42 . The display  42  is a multi-information display and is provided at a position recognizable for the driver. 
     The ECU  10  is configured to be capable of transmitting a warning instruction (described later) to the warning ECU  40 . When receiving the warning instruction, the warning ECU  40 , in response to this instruction, sounds the buzzer  41  as well as display on the display  42  a message and/or a mark peculiar to each driving support control (mentioned later). Accordingly, the ECU  10  can warn the driver via the warning ECU  40 . 
     Next, a description regarding the ECU  10  will be made. The present embodiment apparatus is configured to be capable of performing collision avoidance control, lane deviation suppressing control, and steering override as driving support control. The ECU  10  functions as a main part to determine whether or not to perform these controls. 
     First, processing of the ECU  10  concerning the collision avoidance control will be described. The collision avoidance control is control for warning the driver when a three-dimensional object with a probability of the own vehicle colliding with has been detected in front of the own vehicle, and for warning the driver as well as automatically applying the braking force to the own vehicle when a three-dimensional object with a “high” probability of the own vehicle colliding with has been detected in front of the own vehicle. The ECU  10  generates, based on the object information, the information on a three-dimensional object and a lane every time a predetermined time elapses. Specifically, the ECU  10  sets an origin at a central position of a front edge of the own vehicle, and generates coordinate information (positional information) of the three-dimensional object and the lane using a coordinate system expanding in the left-right direction and in a front direction from the origin. Accordingly, the ECU  10  calculates a shape of the travelling lane defined by the left and right white lines, a position and an orientation (direction) of the own vehicle in the travelling lane, and a relative position of the three-dimensional object with respect to the own vehicle. 
     The ECU  10  calculates a turning radius of the own vehicle based on a yaw rate detected by the yaw rate sensor  13  and a vehicle speed detected by the vehicle speed sensor  14 , and calculates a trajectory of the own vehicle based on this turning radius. The ECU  10  makes a collision determination for determining, based on the position of the three-dimensional object and the trajectory of the own vehicle, whether or not the own vehicle will collide with the three-dimensional object when the own vehicle keeps travelling under a current travelling state. It should be noted that when the three-dimensional object is a moving object, the ECU  10  calculates a trajectory of the three-dimensional object, and makes the collision determination based on the trajectory of the three-dimensional object and the trajectory of the own vehicle. 
     When the ECU  10  determines that the own vehicle will collide with the three-dimensional object by the collision determination, the ECU  10  calculates a time to collision (hereinafter, may be also simply referred to as a “TTC”) in accordance with a following expression (1) based on a distance L from the own vehicle to the three-dimensional object and a relative speed Vr of the three-dimensional object with respect to the own vehicle, where TTC is an expected time (a remaining time to a collision) for the own vehicle to collide with a three-dimensional object. 
         TTC=L/Vr   (1)
 
     When the TTC is less than or equal to a predetermined warning determination threshold TTCath, the ECU  10  determines that it is likely that the own vehicle collide with the three-dimensional object, and when the TTC is less than or equal to a predetermined braking determination threshold TTCbth, the ECU  10  determines that it is highly likely that the own vehicle collides with the three-dimensional object. That is, when the TTC is less than or equal to the braking determination threshold TTCbth, the ECU  10  detects a “three-dimensional object with a high probability of the own vehicle colliding with (i.e., a target object)”. The braking determination threshold TTCbth is smaller than the warning determination threshold TTCath. Hereinafter, they will be described in order. 
     When the ECU  10  determines that it is likely that the own vehicle collides with the three-dimensional object (that is, TTC≤TTCath is satisfied), the ECU  10  transmits the warning instruction to the warning ECU  40 . When receiving the warning instruction, the warning ECU  40  sounds the buzzer  41  as well as displays on the display  42  a predetermined message and/or mark. Accordingly, the warning to the driver is conducted. Hereinafter, among the collision avoidance control, the above-mentioned control which is performed via the warning ECU  40  when the TTC is less than or equal to the warning determination threshold TTCath will be especially referred to as “collision avoidance warning control”. The collision avoidance warning control is performed by the ECU  10  transmitting the warning instruction to the warning ECU  40  and the warning ECU  40  controlling the buzzer  41  and the display  42  in response to this instruction. Therefore, hereinafter, a description of “the ECU  10  performs the collision avoidance warning control” may be used for convenience sake. 
     On the other hand, when the ECU  10  determines that it is highly likely that the own vehicle collides with the three-dimensional object (that is, TTC≤TTCbth is satisfied), the ECU  10  calculates a target deceleration for decelerating the own vehicle. For example, in a case when the target object is under a stopping state, regulate that a current relative speed (equal to the vehicle speed in this example) is V, a current deceleration (acceleration with a negative value) of the own vehicle is a, and a time for the own vehicle to stop is t, and then a travelling distance X for the own vehicle to stop can be expressed by a following expression (2). 
         X=V·t +(½)· a·t   2   (2)
 
     In addition, the time t can be expressed by a following expression (3). 
         t=−V/a   (3)
 
     When substituting the expressing (2) with the expression (3), a deceleration areq required for the own vehicle to stop at a travelling distance D can be expressed by a following expression (4). 
         a req=− V   2 /2 D   (4)
 
     In order to stop the own vehicle before the target object by a distance β, this travelling distance D may be set to a distance (L−β) which is acquired by subtracting the distance β from the distance L. It should be noted that when the target object is a moving object, the deceleration areq may be calculated by using a relative speed and a relative deceleration (a relative acceleration with a negative value) of the own vehicle with respect to the target object. 
     The ECU  10  sets the deceleration areq calculated in this way as a target deceleration. However, in general, a deceleration generated by a vehicle has a limit (for example, around −1G), and thus when an absolute value of the deceleration areq exceeds an upper limit value, the ECU  10  sets a predetermined upper limit value as the target deceleration. The ECU  10  transmits the braking instruction indicating the target deceleration to the brake ECU  20 . When receiving the braking instruction, the brake ECU  20  controls the brake actuator  21  in accordance with the target deceleration to generate the friction braking force at each wheel. Accordingly, the braking force is automatically applied to the own vehicle (that is, the automatic brake is operated), and the own vehicle is decelerated. Hereinafter, among the collision avoidance control, the above-mentioned control which is performed via the brake ECU  20  when the TTC is less than or equal to the braking determination threshold TTCbth will be especially referred to as “collision avoidance braking control”. That is, the collision avoidance control includes the collision avoidance warning control and the collision avoidance braking control. The collision avoidance braking control is performed by the ECU  10  transmitting the braking instruction to the brake ECU  20  and the brake ECU  20  controlling the brake actuator  21  in response to this instruction. Therefore, hereinafter, a description of “the ECU  10  performs the collision avoidance braking control” may be used for convenience sake. 
     Next, processing of the ECU  10  concerning the lane deviation suppressing control will be described. The lane deviation suppressing control is control for warning the driver as well as automatically change a steered angle of each of the steered wheels of the own vehicle so that the own vehicle travels in (within) the travelling lane (along this travelling lane) when a deviation suppressing control performing condition is satisfied, where the deviation suppressing control performing condition includes a condition satisfied when it is determined that the own vehicle is highly likely to deviate from the travelling lane and a condition satisfied when it is determined that the own vehicle deviates from the travelling lane. The ECU  10  calculates, based on the object information, a shape of the travelling lane, and a position and an orientation (direction) of the own vehicle in the travelling lane. For example, as shown in  FIG. 2 , the ECU  10  determines a line passing through a center of left and right white lines LL, LR in a lane width direction as a reference line Ld. The ECU  10  calculates a yaw angle θy and a side distance Ds every time the predetermined time elapses. The yaw angle θy is an angle formed by a direction of the reference line Ld and a travelling direction of the own vehicle V. Hereinafter, among the left white line LL and the right white line LR, a white line from which the own vehicle is highly likely to deviate and a white line from which the own vehicle has deviated may be also referred to as a “target white line”. The side distance Ds is a distance between a front edge central position P (hereinafter, referred to as a “position P”) of the own vehicle V and the target white line (the right white line LR in  FIG. 2 ) in the lane width direction. 
     When the position P is positioned inside the target white line, the side distance Ds is calculated as a positive value. In this case, the side distance Ds increases as the position P moves inward from the target white line. When the position P is positioned on and outside the target white line, the side distance Ds is calculated as a value less than or equal to zero. In this case, the side distance Ds decreases as the position P moves outward from the target white line. Consider a case when the side distance Ds becomes less than a predetermined deviation determination threshold Dsth. In this case, when the side distance Ds is larger than a half of a vehicle width w of the own vehicle V (w/2&lt;Ds&lt;Dsth), the ECU  10  determines that the own vehicle is highly likely to deviate from the travelling lane, and when the side distance Ds is less than or equal to the half of the vehicle width w (Ds≤w/2), the ECU  10  determines that the own vehicle has already deviated from the travelling lane. That is, the performing condition of the lane deviation suppressing control is satisfied when Ds&lt;Dsth is satisfied. 
     When the ECU  10  determines that the own vehicle is highly likely to deviate from the travelling lane and when the own vehicle has already deviated from the travelling lane, the ECU  10  calculates a target lateral acceleration Gy in accordance with a following expression (5). 
         Gy=K 1× Ds′+K 2×θ y   (5)
 
     Here, the target lateral acceleration Gy is a lateral acceleration set in such a manner that the own vehicle will not deviate outside from the white line. When the own vehicle turns in a clockwise direction, the target lateral acceleration Gy is calculated as a positive value, and when the own vehicle turns in an anticlockwise direction, the target lateral acceleration Gy is calculated as a negative value. K 1  and K 2  represents control gains, respectively. The control gain K 1  is positive and the control gain K 2  is negative. Ds′ is set based on the side distance Ds. Specifically, when the target white line is the left white line LL, Ds′ is set so as to increase as the side distance Ds becomes smaller, and when the target white line is the right white line LR, Ds′ is set so as to decrease as the side distance Ds becomes smaller. For example, when the target white line is the left white line LL, Ds′ is set as a value acquired by subtracting the side distance Ds from the deviation determination threshold Dsth (Ds′=Dsth−Ds&gt;0), and when the target white line is the right white line LR, Ds′ is set as a value acquired by reversing a sign of a value acquired by subtracting the side distance Ds from the deviation determination threshold Dsth (Ds′=Ds−Dsth&lt;0). It can be said that each of Ds′ and the yaw angle θy is an index indicating a degree of deviation from the travelling lane. When the travelling direction of the own vehicle V is on a right side of the reference line Ld, the yaw angle θy is calculated as a positive value, and when the travelling direction of the own vehicle V is on a left side of the reference line Ld, the yaw angle θy is calculated as a negative value. 
     When the performing condition of the lane deviation suppressing control is satisfied, the ECU  10  may calculate the target lateral acceleration Gy using a following expression instead of the expression (5) mentioned above. 
         Gy=K 3× Dc+K 4×θ y+K 5× v  
 
     Here, K 3 , K 4 , and K 5  represent control gains, respectively. The control gain K 3  is positive, the control gain K 4  is negative, and the control gain K 5  is positive. Dc represents a distance between the position P of the own vehicle V and the reference line Ld in the lane width direction. When the position P is positioned on the left side of the reference line Ld, Dc is calculated as a positive value, and when the position P is positioned on the right side of the reference line Ld, Dc is calculated as a negative value. v represents a curvature. When a road is curving toward a right side with respect to the reference line Ld, the curvature v is calculated as a positive value, and when a road is curving toward a left side with respect to the reference line Ld, the curvature v is calculated as a negative value. 
       FIG. 3  is a target steered angle conversion map regulating a relationship between the target lateral acceleration Gy and a target steered angle θtgt. This target steered angle conversion map is prepared for every vehicle speed in advance and is stored in the ROM of the ECU  10 . The ECU  10  calculates, based on the target lateral acceleration Gy and the vehicle speed, a target steered angle θtgt, referring to the target steered angle conversion map, and transmits to the steering ECU  30  the steering instruction indicating this target steered angle θtgt. When the steered wheels are turned to the right with respect to the travelling direction of the own vehicle, the target steered angle θtgt is calculated as a positive value, and when the steered wheels are turned to the left with respect to the travelling direction of the own vehicle, the target steered angle θtgt is calculated as a negative value. When receiving the steering instruction, the steering ECU  30  controls the steered motor  32  in accordance with the target steered angle θtgt to steer the steered wheels. Accordingly, the steered angle of each of the steered wheels is automatically changed (that is, the steering torque is applied to the steering mechanism), and the own vehicle travels in such a manner that the own vehicle will not deviate outside from the white lines of the travelling lane (in other words, the own vehicle travels along the travelling lane). 
     In addition, when the ECU  10  determines that the own vehicle is highly likely to deviate from the travelling lane and when the ECU  10  determines that the own vehicle has already deviated from the travelling lane, the ECU  10  transmits the warning instruction to the warning ECU  40 . When receiving the warning instruction, the warning ECU  40  sounds the buzzer  41  and displays on the display  42  the predetermined message and/or mark. Accordingly, the warning to the driver is conducted. 
     As is clear from the description above, the performing condition of the lane deviation suppressing control becomes satisfied when Ds&lt;Dsth is satisfied. When the performing condition of the lane deviation suppressing control is satisfied, the ECU  10  executes following processing as the lane deviation suppressing control. 
     The ECU  10  transmits the steering instruction to the steering ECU  30  such that the steering ECU  30  controls the steered motor  32  in response to the steering instruction. 
     The ECU  10  transmits the warning instruction to the warning ECU  40  such that the warning ECU  40  controls the buzzer  41  and the display  42  in response to the warning instruction. 
     Hereinafter, action of the ECU  10  executing the processing above when the performing condition of the lane deviation suppressing control is satisfied may be also referred to as “the ECU  10  performs the lane deviation suppressing control” for convenience sake. 
     It should be noted that the performing condition of the lane deviation suppressing control is not limited to a case when the side distance Ds is less than the deviation determination threshold Dsth. For example, the ECU  10  may determine that the performing condition of the lane deviation suppressing control becomes satisfied during a predetermined period from a timing when an index value (a deviation index value) is estimated to be larger than a first threshold where the index value is a value which increases as a probability of the own vehicle deviating from the target white line becomes higher. The deviation index value can be calculated as a value which increases as a deviation remaining time becomes shorter, for example. The deviation remaining time can be calculated by dividing a “distance between an edge of the own vehicle at a target white line side and the target white line” by a “speed toward the target white line of the own vehicle in the vehicle width direction”. 
     Subsequently, processing of the ECU  10  concerning the steering override will be described. The steering override is control for, when a steering override condition (described later) becomes satisfied in a case when the driver conducts the steering operation while the collision avoidance braking control and/or the lane deviation suppressing control are/is being performed, finishing a corresponding collision avoidance braking control and/or lane deviation suppressing control to prioritize the steering operation by the driver. The steering override condition becomes satisfied when at least one of following expressions (6) or (7) becomes satisfied. 
       |θ s|≥θsth   (6)
 
       |ω s|≥ωsth   (7)
 
     Here, θs represents a steering angle based on the steering operation by the driver. This steering angle θs can be calculated by subtracting a “steered angle acquired based on a rotation angle of the steered motor  32  (or a steered angle detected by a steered angle sensor)” from a “steering angle detected by the steering angle sensor  12 ”. θsth is a threshold (a steering angle threshold) of the steering angle θs, where θsth determines whether the steering override condition is satisfied or not. θsth is set to either an “initial value under an initial state” or a “varied value after cooperative control (mentioned later) is started, where the cooperative control is control for making the lane deviation suppressing control cooperate with the collision avoidance braking control”. The initial value of the steering angle threshold θsth is a first steering angle threshold θs1th (θsth=θs1th). ωs is a steering angular speed based on the steering operation by the driver and can be calculated by differentiating the steering angle θs with respect to time. ωsth is a threshold (a steering angular speed threshold) of the steering angular speed ωs, where ωsth determines whether the steering override condition is satisfied or not. ωsth is set to either an “initial value under an initial state” or a “varied value after the cooperative control is started”. The initial value of the steering angular speed threshold ωsth is a first steering angular speed threshold ωs1th (ωsth=ωs1th). It should be noted that the steering angle θs and the steering angular speed ωs correspond to one example of “steering related values”, the steering angle threshold θsth and the steering angular speed threshold ωsth correspond to one example of “steering related thresholds”, and the first steering angle threshold θs1th and the first steering angular speed threshold ωs1th correspond to one example of “first steering related thresholds”. 
     During a period when the collision avoidance braking control and/or the lane deviation suppressing control are/is being performed, the ECU  10  calculates an absolute value of the steering angle θs and an absolute value of the steering angular speed ωs every time the predetermined time elapses and determines whether or not the steering override condition is satisfied. When it is determined that the steering override condition becomes satisfied, the ECU  10  finishes a corresponding control (i.e., a control which is being performed) to prioritize the steering operation by the driver. It should be noted that the first steering angle threshold θs1th and the first steering angular speed threshold ωs1th are both set to relatively small values. Therefore, under the initial state, the steering override condition becomes satisfied relatively easily by the steering operation by the driver. It should be noted that the steering override condition may become satisfied when a condition that a steering torque detected by a steering torque sensor is more than or equal to a predetermined steering torque threshold becomes satisfied. 
     When the lane deviation suppressing control is being performed in a case when the collision avoidance braking control is about to be performed, the ECU  10  determines whether or not to perform the lane deviation suppressing control in addition to the collision avoidance braking control (strictly, the collision avoidance control) (in other words, to perform the cooperative control). This determination is made based on a result of a direction determination (direction determination processing). 
     The direction determination is a determination for determining, provided that the steered wheels are turned by the lane deviation suppressing control, whether the own vehicle travels to a direction (collision direction) toward which the own vehicle will collide with the target object or whether the own vehicle travels to a direction (collision avoidance direction) toward which the own vehicle will avoid colliding with the target object. In other words, the direction determination is a determination for determining whether a steered direction of the steered wheels is different from or the same as the collision avoidance direction. When it is determined by the direction determination that the own vehicle travels to the collision direction (that is, the steered direction is different from the collision avoidance direction), the ECU  10  determines that the collision avoidance effect by the collision avoidance braking control may be reduced due to the lane deviation suppressing control, and finishes (stops) the lane deviation suppressing control to perform the collision avoidance braking control. That is, the ECU  10  does not perform the cooperative control. On the other hand, when it is determined by the direction determination that the own vehicle travels to the collision avoidance direction (that is, the steered direction is the same as the collision avoidance direction), the ECU  10  determines that the collision avoidance effect may be improved thanks to the lane deviation suppressing control, and perform both of the collision avoidance braking control and the lane deviation suppressing control. That is, the ECU  10  performs the cooperative control. 
     Here, “whether or not the steered direction of the steered wheels is the same as the collision avoidance direction” in the direction determination is determined based on a positional relationship between the target object and the travelling lane. A specific description will be made referring to  FIG. 4A  and  FIG. 4B . A three-dimensional object A shown in  FIG. 4A  and a three-dimensional object B shown in  FIG. 4B  are both three-dimensional objects determined by the collision determination that the own vehicle will collide with, and TTCs to the three-dimensional object A and to the three-dimensional object B are both less than or equal to the braking determination threshold TTCbth. That is, the three-dimensional objects A and B are both target objects, and  FIG. 4A  and  FIG. 4B  are diagrams showing situations where the collision avoidance braking control for avoiding collision with the target objects A and B is performed, respectively. In addition, the side distance Ds shown in each of  FIG. 4A  and  FIG. 4B  is less than the deviation determination threshold Dsth, and the performing condition of the lane deviation suppressing control is satisfied. 
     An arrow R 1  shown in  FIG. 4A  and an arrow R 2  shown in  FIG. 4B  both indicate trajectories of the own vehicle V, provided that the cooperative control has been performed. When the lane deviation suppressing control is performed by the cooperative control, the steered wheels are turned in such a manner that the own vehicle V will not deviate outside from the left white line LL. Therefore, according to the trajectory R 1  in  FIG. 4A , when the target object A is positioned in the travelling lane, the own vehicle V is highly likely to travel to the collision direction. On the other hand, according to the trajectory R 2  in  FIG. 4B , when the target object B is positioned outside the travelling lane, the own vehicle V is highly likely to travel to the collision avoidance direction. 
     Thus, the ECU  10  determines, based on the object information, whether or not the target object is positioned in the travelling lane. When it is determined that the target object is positioned in the travelling lane, the ECU  10  determines that the steered direction of the steered wheels is different from the collision avoidance direction, and when it is determined that the target object is positioned outside the travelling lane, the ECU  10  determines that the steered direction of the steered wheels is the same as the collision avoidance direction. 
     When it is determined by the direction determination that the steered direction is the same as the collision avoidance direction, the lane deviation suppressing control is cooperatively performed with the collision avoidance braking control, and thus the steered wheels are steered. When the steered wheels are turned, the driver tends to rotate (operate) the steering wheel to a direction corresponding to the steered direction of the steered wheels in order to avoid colliding with the target object. In this case, if the steering angle threshold θsth and the steering angular speed threshold ωsth remain as the initial values, respectively, the steering override condition may become satisfied relatively easily by the steering operation by the driver as described above, and as a result, the collision avoidance braking control and the lane deviation suppressing control may be finished halfway (in the middle). In such a case, if the steering operation by the driver is insufficient, a possibility that the own vehicle cannot avoid the collision with the target object becomes high, and thus it is likely that the collision avoidance effect by the collision avoidance braking control and the lane deviation suppressing control cannot be adequately obtained. 
     Therefore, when it is determined by the direction determination that the steered direction is the same as the collision avoidance direction, the ECU  10  increases the steering angle threshold θsth from the first steering angle threshold θs1th to a second steering angle threshold θs2th (θs2th&gt;θs1th) as well as increases the steering angular speed threshold ωsth from the first steering angular speed threshold ωs1th to a second steering angular speed threshold ωs2th (ωs2th&gt;ωs1th). Accordingly, the steering override condition becomes harder to be satisfied even when the driver conducts the steering operation, and the collision avoidance braking control and the lane deviation suppressing control are highly likely to be performed to the end. Therefore, it can be suppressed that the collision avoidance effect is reduced owing to the steering operation by the driver. The steering angle threshold θsth and the steering angular speed threshold ωsth are initialized after the collision avoidance control or the collision avoidance braking control is finished. It should be noted that the second steering angle threshold θs2th and the second steering angular speed threshold ωs2th correspond to one example of “second steering related thresholds”. 
     When it is determined by the direction determination that the own vehicle travels to the collision direction, the ECU  10  sets a value of a performance stop flag Xk to 1. The performance stop flag Xk is a flag for determining whether or not to stop the lane deviation suppressing control. When a value of the performance stop flag Xk is 1, the ECU  10  does not perform the lane deviation suppressing control even when the performing condition of the lane deviation suppressing control is satisfied (that is, finishes (stops) the lane deviation suppressing control). When a value of the performance stop flag Xk is 0, the ECU  10  performs the lane deviation suppressing control when the performing condition of the lane deviation suppressing control is satisfied (that is, does not finish (stop) the lane deviation suppressing control). However, when the steering override condition mentioned above is satisfied, the ECU  10  finishes the lane deviation suppressing control to prioritize the steering operation by the driver. Once the ECU  10  sets a value of the performance stop flag Xk to 1, the ECU  10  keeps the value of the performance stop flag Xk as 1 until the collision avoidance control or the collision avoidance braking control is finished. 
     (Actual Operation) 
     The CPU of the ECU  10  is configured to execute routines shown by flowcharts in  FIG. 5  to  FIG. 7  in parallel every time the predetermined time elapses during a period where an ignition switch of the own vehicle has been turned on. A description will be made below in order. 
     When a predetermined timing arrives, the CPU initiates processing from a step  500  in  FIG. 5  and proceeds to a step  505  to make the collision determination to determine, based on the position(s) of the three-dimensional object(s) and the trajectory of the own vehicle, whether or not a three-dimensional object exists with which the own vehicle will collide. When the three-dimensional object with which the own vehicle will collide does not exist, the CPU makes a “No” determination at the step  505 , and proceeds to a step  510  to determine whether or not the collision avoidance braking control had been performed when the present routine was executed the predetermined time before. When the collision avoidance braking control had not been performed when the present routine was executed the predetermined time before, the CPU makes a “No” determination at the step  510 , and proceeds to a step  595  to tentatively terminate the present routine. 
     On the other hand, when the three-dimensional object with which the own vehicle will collide exists, the CPU makes an “Yes” determination at the step  505 , and proceeds to a step  515  to calculate TTC to the three-dimensional object. Thereafter, the CPU proceeds to a step  520  to determine whether or not the TTC is less than or equal to the warning determination threshold TTCath. When the TTC is larger than the warning determination threshold TTCath, the CPU makes a “No” determination at the step  520 , and proceeds to the step  510  to make the determination mentioned above. 
     In contrast, when the TTC is less than or equal to the warning determination threshold TTCath, the CPU makes an “Yes” determination at the step  520 , and proceeds to a step  525  to perform the collision avoidance warning control. Subsequently, the CPU proceeds to a step  530  to determine whether or not the TTC is less than or equal to the braking determination threshold TTCbth. When the TTC is larger than the braking determination threshold TTCbth, the CPU makes a “No” determination at the step  530 , and proceeds to the step  510  to make the determination mentioned above. 
     On the other hand, when the TTC is less than or equal to the braking determination threshold TTCbth, the CPU makes an “Yes” determination at the step  530  (that is, determines that the three-dimensional object is a target object), and determines at a step  535  whether or not the lane deviation suppressing control is being performed. When the lane deviation suppressing control is not being performed, the CPU makes a “No” determination at the step  535 , and proceeds to a step  540  to perform the collision avoidance braking control. In other words, the CPU performs the collision avoidance control along with the collision avoidance warning control. Thereafter, the CPU proceeds to the step  595  to tentatively terminate the present routine. 
     In contrast, when the lane deviation suppressing control is being performed, the CPU makes an “Yes” determination at the step  535 , and proceeds to a step  545  to make the direction determination. That is, the CPU determines whether or not the steered direction of the steered wheels is the same as the collision avoidance direction. Specifically, the CPU determines whether or not the target object is positioned in the travelling lane based on the object information. When it is determined that the target object is positioned in the travelling lane, the CPU makes a “No” determination at the step  545  (that is, determines that the collision avoidance effect will be reduced owing to the lane deviation suppressing control), and proceeds to a step  550  to set a value of the performance stop flag Xk to 1 and finish (stop) the lane deviation suppressing control. Subsequently, the CPU proceeds to the step  540  to perform the collision avoidance braking control. That is, the cooperative control is not performed. Thereafter, the CPU proceeds to the step  595  to tentatively terminate the present routine. 
     On the other hand, when it is determined at the step  545  that the target object is positioned outside the travelling lane, the CPU makes an “Yes” determination at the step  545  (that is, determines that the collision avoidance effect will be improved thanks to the lane deviation suppressing control), and proceeds to a step  555  to determine whether or not the steering angle threshold θsth and the steering angular speed threshold ωsth are the initial values (θsth=θs1th, ωsth=ωs1th). When the steering angle threshold θsth and the steering angular speed threshold ωsth are the initial values, the CPU makes an “Yes” determination at the step  555 , and at a step  560 , increases the steering angle threshold θsth to the second steering angle threshold θs2th as well as increases the steering angular speed threshold ωsth to the second steering angular speed threshold ωs2th. Subsequently, the CPU proceeds to the step  540  to perform the collision avoidance braking control. That is, the cooperative control is performed. Thereafter, the CPU proceeds to the step  595  to tentatively terminate the present routine. 
     In contrast, when the steering angle threshold θsth and the steering angular speed threshold ωsth are not the initial values, the CPU makes a “No” determination at the step  555  (that is, determines that the processing to increase θsth and ωsth (refer to the step  560 ) has been already finished), and directly proceeds to the step  540  to perform the collision avoidance control without proceeding to the step  560 . That is, the cooperative control is performed. Thereafter, the CPU proceeds to the step  595  to tentatively terminate the present routine. 
     While the cooperative control is being performed, when the trajectory of the own vehicle has changed by the lane deviation suppressing control, or when the three-dimensional object with which the own vehicle will collide comes not to be detected as a result of the target object having moved, the CPU makes a “No” determination in the collision determination at the step  505 , and makes the determination at the step  510 . At this point, the cooperative control is being performed and thus the CPU makes an “Yes” determination at the step  510 , and proceeds to a step  565  to finish the collision avoidance control. Subsequently, the CPU initializes at a step  570  the steering angle threshold θsth and the steering angular speed threshold ωsth, and proceeds to a step  575  to set a value of the performance stop flag Xk of the lane deviation suppressing control to 0. At this time, when the performing condition of the lane deviation suppressing control is satisfied as well as the steering override condition is not satisfied, the CPU performs the lane deviation suppressing control. Thereafter, the CPU proceeds to the step  595  to tentatively terminate the present routine. 
     In addition, while the cooperative control is being performed, when a three-dimensional object with which the own vehicle will collide has been detected (step  505 : Yes), but the TTC to this three-dimensional object becomes larger than the warning determination threshold TTCath as a result of the cooperative control having been performed or the target object having moved, the CPU makes a “No” determination at the step  520 , and makes the determination at the step  510 . Thereafter, the CPU executes the processing as mentioned above. 
     On the other hand, while the cooperative control is being performed, when the collision avoidance warning control is being performed (refer to S 525 ) for a three-dimensional object identified in the collision determination at the step  505 , but the TTC to this three-dimensional object becomes larger than the braking determination threshold TTCbth as a result of the cooperative control having been performed or the target object having moved, the CPU makes a “No” determination at the step  530 , and makes the determination at the step  510 . The CPU makes an “Yes” determination at the step  510 , and proceeds to a step  565  to finish the collision avoidance braking control. That is, the CPU continues to perform the collision avoidance warning control. Thereafter, the CPU tentatively terminates the present routine at the step  595 , via the step  570  and the step  575 . 
     It should be noted that when a “No” determination is made at the step  505 , the step  520 , or the step  530  in a case when only the collision avoidance braking control (strictly, the collision avoidance control) is being performed, the CPU makes an “Yes” determination at the step  510 , and finishes at the step  565  the collision avoidance control or the collision avoidance braking control. Thereafter, the CPU tentatively terminates the present routine at the step  595 , via the step  570  and the step  575 . 
     In parallel with the routine mentioned above, when a predetermined timing arrives, the CPU initiates processing from a step  600  in  FIG. 6  and proceeds to a step  605  to determine whether or not the performing condition of the lane deviation suppressing control is satisfied. When the performing condition is not satisfied (Ds≥Dsth), the CPU makes a “No” determination at the step  605 , and proceeds to a step  610  to finish the lane deviation suppressing control when this control is currently being performed or to continue not to perform the lane deviation suppressing control when this control is not currently being performed. Thereafter, the CPU proceeds to a step  695  to tentatively terminate the present routine. 
     On the other hand, when the performing condition of the lane deviation suppressing control is satisfied (Ds&lt;Dsth), the CPU makes an “Yes” determination at the step  605 , and proceeds to a step  615  to determine whether or not a value of the performance stop flag Xk is 0. When the value of the performance stop flag Xk is 1, the CPU makes a “No” determination at the step  615 , and proceeds to a step  610  to finish the lane deviation suppressing control when this control is currently being performed or to continue not to perform the lane deviation suppressing control when this control is not currently being performed. Thereafter, the CPU proceeds to the step  695  to tentatively terminate the present routine. 
     In contrast, when the value of the performance stop flag Xk is 0, the CPU makes an “Yes” determination at the step  615 , and proceeds to a step  620  to determine whether or not the steering override condition is satisfied. When the steering override condition is satisfied, the CPU makes an “Yes” determination at the step  620 , and proceeds to a step  610  to finish the lane deviation suppressing control when this control is currently being performed or to continue not to perform the lane deviation suppressing control when this control is not currently being performed. Thereafter, the CPU proceeds to the step  695  to tentatively terminate the present routine. 
     On the other hand, when the steering override condition is not satisfied, the CPU makes a “No” determination at the step  620 , and proceeds to a step  625  to perform the lane deviation suppressing control. Thereafter, the CPU proceeds to the step  695  to tentatively terminate the present routine. 
     In parallel with the routine mentioned above, when a predetermined timing arrives, the CPU initiates processing from a step  700  in  FIG. 7  and proceeds to a step  705  to determine whether or not the collision avoidance braking control is being performed. When the collision avoidance braking control is not being performed, the CPU makes a “No” determination at the step  705 , and proceeds to a step  795  to tentatively terminate the present routine. 
     On the other hand, when the collision avoidance braking control is being performed, the CPU makes an “Yes” determination at the step  705 , and proceeds to a step  710  to determine whether or not the steering override condition is satisfied. When the steering override condition is satisfied, the CPU makes an “Yes” determination at the step  710  to finish the collision avoidance braking control currently being performed. Thereafter, the CPU proceeds to the step  795  to tentatively terminate the present routine. 
     In contrast, when the steering override condition is not satisfied, the CPU makes a “No” determination at the step  710 , and proceeds to the step  795  to tentatively terminate the present routine. That is, the CPU continues to perform the collision avoidance braking control currently being performed. 
     Effects of the present embodiment apparatus will be described. In the present embodiment apparatus, when the lane deviation suppressing control is being performed in a case when the collision avoidance braking control is about to be performed, the direction determination is made, and based on a determination result thereof, whether or not to perform the cooperative control is determined. Specifically, when it is determined by the direction determination that the steered direction is different from the collision avoidance braking control, the cooperative control is not performed, whereas when it is determined that the steered direction is the same as the collision avoidance braking control, the cooperative control is performed. According to this configuration, the collision avoidance effect can be improved by making use of the lane deviation suppressing control while suppressing a possibility that the collision avoidance effect is reduced owing to the lane deviation suppressing control, and it becomes possible to make the lane deviation suppressing control properly cooperate with the collision avoidance braking control. 
     Especially, in the present embodiment apparatus, the direction determination is made by determining whether or not the steered direction of the steered wheels is the same as the collision avoidance direction based on the determination result of whether or not the target object is positioned in the travelling lane. Therefore, the direction determination can be properly made. 
     In addition, whether or not the target object is positioned in the travelling lane can be precisely determined based on the object information. Therefore, the direction determination can be made based on a clear criterion. 
     Moreover, the present embodiment apparatus is especially useful when avoiding the collision or reducing the impact of the collision with a fixed object (for example, a guardrail or a sidewall) extending along the lane on the outside of the lane. A specific description will be made referring to  FIG. 8  and  FIG. 9 . As shown in  FIG. 8  and  FIG. 9 , on the outside of the travelling lane of the own vehicle V (on the outside of the left white line LL), a guardrail  100  is extending along the travelling lane. In addition, the performing condition of the lane deviation suppressing control is satisfied in both cases (Ds&lt;Dsth). 
     In  FIG. 8 , the present embodiment apparatus recognizes a part  100   a  of the guardrail  100  as a target object (hereinafter, may be also referred to as a “target object  100   a ”), and is about to perform the collision avoidance braking control for avoiding the collision with the target object  100   a . A dashed line R 3  is a trajectory of the own vehicle V calculated based on the yaw rate and the vehicle speed at a current timing. A length of the trajectory R 3  is substantially equal to the shortest distance from the own vehicle V to the target object  100   a . According to a conventional configuration to prioritize the collision avoidance braking control over the lane deviation suppressing control, the own vehicle V travels straightforward along the trajectory R 3 , and thus the target deceleration becomes relatively large, resulting in a possible burden on the driver and other passengers. 
     In contrast, the present embodiment apparatus performs the cooperative control because the target object  100   a  is positioned outside the travelling lane. A dashed line R 4  is a trajectory of the own vehicle V when the cooperative control is performed. When the lane deviation suppressing control is performed by the cooperative control, the yaw angle θy (illustration is omitted in  FIG. 8 ) becomes small, and therefore the present embodiment apparatus comes to recognize a part  100   b  positioned farther from the part  100   a  as a target object. That is, a trajectory of the own vehicle V changes from the trajectory R 3  to the trajectory R 4  by the cooperative control, and thereby a distance to the target object becomes longer. Hence, compared with the conventional configuration, the target deceleration in the collision avoidance braking control becomes moderate, resulting in reducing a burden on the driver and the passengers. Besides, even in a situation where a vehicle could only reduce the impact of the collision according to a conventional configuration, a possibility that the own vehicle can avoid the collision becomes higher. 
     In  FIG. 9 , the present embodiment apparatus recognizes a part  100   c  of the guardrail  100  as a target object (hereinafter, may be referred to as a “target object  100   c ”), and is about to perform the collision avoidance braking control for avoiding the collision with the target object  100   c . A dashed line R 5  is a trajectory of the own vehicle V calculated based on the yaw rate and the vehicle speed at the current timing. According to the conventional configuration, the own vehicle V travels straightforward along the trajectory R 5 , and thus the own vehicle V is highly likely to cross the left white line LL in the middle of the collision avoidance braking control. 
     In contrast, the present embodiment apparatus performs the cooperative control because the target object  100   c  is positioned outside the travelling lane. A dashed line R 6  is a trajectory of the own vehicle V when the cooperative control is performed. The lane deviation suppressing control is performed along the trajectory R 6  by the cooperative control, and thereby it becomes possible that the own vehicle V avoids the collision with the target object  100   c  without crossing the left white line LL. 
     As described above, according to the present embodiment apparatus, the lane deviation suppressing control is made to properly cooperate with the collision avoidance braking control, and thereby it becomes possible to especially efficiently avoid the collision or reduce the impact of the collision with the guardrail, the sidewall, and the like. 
     The driving support apparatus according to the present embodiment has been described. However, the present invention is not limited thereto and may adopt various modifications within a scope of the present invention. 
     For example, in the present embodiment, when it is determined by the direction determination that the steered direction of the steered wheels is the same as the collision avoidance direction, the processing of increasing θsth and ωsth is executed. However, this processing may be omitted. That is, the processing at the step  555  and the step  560  is not mandatory in the routine shown in  FIG. 5 , and the CPU may directly proceed to the step  540  when an “Yes” determination is made at the step  545 . According to this configuration as well, it becomes possible to make the lane deviation suppressing control properly cooperate with the collision avoidance braking control. 
     In addition, in the present embodiment, the direction determination is made by determining whether or not the steered direction is the same as the collision avoidance direction based on whether or not a target object is positioned in the travelling lane. However, the direction determination may be made based on other criteria. For example, calculate a trajectory of the own vehicle when the cooperative control is assumed to be performed, and based on a position of the target object and this trajectory, the direction determination may be made. 
     Further, at the step  535  in  FIG. 5 , the CPU may determine whether or not the performing condition of the lane deviation suppressing control (Ds&lt;Dsth) is satisfied.