Patent Publication Number: US-2017358209-A1

Title: Collision avoidance device

Description:
TECHNICAL FIELD 
     The present invention relates to a collision avoidance device. 
     BACKGROUND ART 
     In recent years, collision avoidance devices have been known which apply a brake to a vehicle by automatic braking, for example, to avoid colliding with a preceding vehicle ahead in traveling direction when an inter-vehicle distance to the preceding vehicle decreases to a certain distance or below. For example, such a conventional collision avoidance device is known to include a technique for ending control over the avoidance braking to prevent unnecessary intervention of avoidance braking when a driver operates the steering during the avoidance braking. 
     CITATION LIST 
     Patent Literature 
     Patent Document 1: Japanese Examined Patent Publication No. S55-015337 
     Patent Document 2: Japanese Patent Application Laid-open Publication No. 2004-224309 
     SUMMARY OF INVENTION 
     Problem to be Solved by the Invention 
     However, such a conventional collision avoidance device may not be able to sufficiently change the course of the vehicle depending on, for example, a road surface condition and a tire condition even when a detected steering amount by the steering is sufficient for avoiding collision during normal running. In such cases, the collision avoidance device determines the collision as avoidable from the detected steering amount and terminates the avoidance braking control, which may make it difficult for the vehicle to avoid the collision with the preceding vehicle, as a result. 
     Thus, it is an object of the present invention to provide a collision avoidance device that is capable of controlling a vehicle including a collision avoidance function to more reliably avoid collision. 
     Means for Solving Problem 
     A collision avoidance device according to the present invention comprises, for example, a collision avoidance executor that can execute a collision avoidance function for a vehicle to avoid collision with an object to be avoided; a determiner that determines, when a driver operates a steering, whether to be able to avoid the collision with the object to be avoided, based on a turning parameter related to a turning caused by the steering; and a collision avoidance controller that inhibits or ends the execution of the collision avoidance function when the collision with the object to be avoided is determined to be avoidable. 
     In the collision avoidance device, the determiner determines whether to be able to avoid the collision with the object to be avoided by determining whether a lateral acceleration or a yaw rate serving as the turning parameter is equal to or greater than a first threshold, and the collision avoidance controller inhibits or ends the execution of the collision avoidance function when the lateral acceleration or the yaw rate of a vehicle is equal to or greater than the first threshold. 
     In the collision avoidance device, the determiner determines, based on the steering of the driver, whether the driver has an intention of cancellation during the execution of the collision avoidance function, and the collision avoidance controller ends the execution of the collision avoidance function when the driver is determined to have the intention of cancellation during the execution of the collision avoidance function. 
     In the collision avoidance device, the determiner determines whether driver has the intention of cancellation, based on a determination on whether a steering speed by the steering is equal to or greater than a second threshold, and the collision avoidance controller ends the execution of the collision avoidance function when the steering speed is equal to or greater than the second threshold. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic diagram illustrating an exemplary schematic configuration of a vehicle according to an embodiment of the present invention; 
         FIG. 2  is a block diagram illustrating an exemplary functional configuration of a collision avoidance electronic control unit (ECU) according to the embodiment; 
         FIG. 3  is a flowchart of an exemplary procedure of execution of a collision avoidance function according to the embodiment; 
         FIG. 4  is a schematic diagram illustrating an example of overtaking a preceding vehicle in the embodiment; 
         FIG. 5  is a diagram illustrating an exemplary relation between a time to collision and a lateral acceleration necessary for collision avoidance in the embodiment; 
         FIG. 6  is a flowchart of an exemplary procedure of determination on inhibition or ending of execution of the collision avoidance function according to the embodiment; and 
         FIG. 7  depicts diagrams illustrating relations of a deceleration by avoidance braking with turning parameters in the embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENT 
     An exemplary embodiment of the present invention will be disclosed below. Configurations of the embodiment to be given below and operations and results (effects) provided by the configurations are merely examples. The present invention can also be carried out with other configurations than those disclosed in the following embodiment. The present invention can attain at least one of the various effects (including derivative effects) obtained by the configurations. 
       FIG. 1  is a schematic diagram illustrating an exemplary configuration of a vehicle according to the embodiment. In the present embodiment, a vehicle  100  may be, for example, an automobile (internal combustion engined automobile) using an internal combustion engine (engine  20 ) as a driving source, an automobile (such as an electric vehicle or a fuel-cell vehicle) using an electric motor (motor, which is not illustrated) as the driving source, or an automobile (hybrid automobile) using both an internal combustion engine and an electric motor as driving sources. The vehicle  100  can be equipped with various types of transmissions and various types of devices (such as systems and components) needed for driving the internal combustion engine or the electric motor. For example, systems, numbers, and layouts of devices for driving wheels on the vehicle can be variously set. In the present embodiment, as an example, the vehicle  100  is a four-wheel vehicle (four-wheel automobile), and includes two left and right front wheels FL and FR and two left and right rear wheels RL and RR. The front side in a vehicle front-rear direction (arrow FB) corresponds to the left side in  FIG. 1 . 
     As illustrated in  FIG. 1 , the vehicle  100  of the present embodiment includes an engine  20 , a brake controller  30 , an imaging device  51 , a radar  52 , a brake switch  42 , an accelerator pedal stroke sensor  44 , a acceleration sensor  43 , a steering system  50 , a steering angle sensor  45 , and a control device  40 . 
     The vehicle  100  also includes wheel cylinders Wfr and Wfl and wheel speed sensors  41   fr  and  41   fl  corresponding to the two front wheels FR and FL, respectively, and includes wheel cylinders Wrr and Wrl and wheel speed sensors  41   rr  and  41   rl  corresponding to the two rear wheels RR and RL, respectively. Hereinafter, the wheel speed sensors  41   fr ,  41   fl ,  41   rr , and  41   rl  may be collectively referred to as wheel speed sensors  41 , and the wheel cylinders Wfr, Wfl, Wrr, and Wrl may be collectively referred to as wheel cylinders W. 
     Although the vehicle  100  includes basic components as the vehicle  100  in addition to the components illustrated in  FIG. 1 , description will herein be given of only relevant configurations of the vehicle  100  and control over the configurations. 
     The imaging device  51  is, for example, a digital camera incorporating an image pickup device, such as a charge-coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS) image sensor (CIS). The imaging device  51  can output image data (moving image data or frame data) at a certain frame rate. In the present embodiment, the imaging device  51  is located at a front-side end (end in a plan view) (front side in the vehicle front-rear direction) of a vehicle body (not illustrated), and can be provided, for example, on a front bumper. The imaging device  51  outputs image data including an object to be avoided, such as a preceding vehicle  501  ahead of the vehicle. 
     The radar  52  is, for example, a millimeter-wave radar. The radar  52  can output, for example, distance data indicating the distance (separation or detected distance refer to) to the object to be avoided such as the preceding vehicle, and velocity data indicating relative speed (velocity) to the object to be avoided. The control device  40  updates results of measuring the distance by the radar  52  between the vehicle  100  and the object to be avoided as the preceding vehicle, and stores the updated results in a storage at appropriate times (for example, at certain time intervals). The updated distance measurements can be used for calculation. 
     Each of the wheel speed sensors  41  outputs a pulse signal upon every rotation of the corresponding wheel by a certain angle. 
     The accelerator pedal stroke sensor  44  is provided for an accelerator pedal AP to detect the stroke of the accelerator pedal AP by the driver. The brake switch  42  is provided for a brake pedal BP to output a brake operation signal indicating operation or non-operation to the brake pedal BP by the driver. Specifically, the brake switch  42  outputs an ON (High) brake operation signal when the brake pedal BP is operated, and outputs an OFF (Low) brake operation signal when the brake pedal BP is not operated. 
     The acceleration sensor  43  detects the acceleration of the vehicle body in the front-rear direction (front-rear acceleration), and outputs a signal representing a front-rear acceleration Gx. The acceleration sensor  43  also detects an acceleration in a lateral direction of the vehicle body (lateral acceleration), and outputs a signal representing a lateral acceleration Gy. The lateral acceleration Gy is also called a “lateral G”. 
     A yaw rate sensor  46  detects a yaw rate of the vehicle  100 . The yaw rate refers to a change speed of the rotational angle of the vehicle  100  in yaw direction (turning direction). 
     The steering system  50  is, for example, a steering wheel. The steering angle sensor  45  is a sensor that detects a steering amount of the steering system  50  (steering wheel). The steering angle sensor  45  includes, for example, a Hall element. 
     The engine  20  outputs power in accordance with the operation of the accelerator pedal AP by the driver. In response to a command from a brake electronic control unit (ECU)  12 , the brake controller  30  controls the wheels FR, FL, RR, and RL to generate braking forces with brake fluid pressure. The brake controller  30  produces the brake fluid pressure corresponding to an operating force applied to the brake pedal BP, and can adjust the supply of the brake fluid pressure to the wheel cylinders Wfr, Wfl, Wrr, and Wrl disposed for the wheels FR, FL, RR, and RL, respectively. 
     The control device  40  receives signals and data from the respective elements of the vehicle  100  to control them. As illustrated in  FIG. 1 , the control device  40  mainly includes a collision avoidance electronic control unit (ECU)  60 , the brake ECU  12 , and an engine ECU  13 . In the present embodiment, the control device  40  is an example of a collision avoidance device. 
     The engine ECU  13  handles various types of control of the engine  20 , including fuel injection control and air-intake adjustment control. 
     The brake ECU  12  handles, for example, braking torque adjustment control over the vehicle and each of the wheels FR, FL, RR, and RL. The brake ECU  12  calculates, for example, the vehicle-body speed of the vehicle based on a detection signal from at least one of the wheel speed sensors  41  provided for the respective wheels FR, FL, RR, and RL, and the deceleration of the vehicle based on a detection signal from the acceleration sensor  43 , and transmits the resultants to the other ECUs. The deceleration as calculated herein exhibits a positive value while the vehicle is decelerating and exhibits a negative value while the vehicle is accelerating. 
     The collision avoidance ECU  60  controls a collision avoidance function to execute. The details of the collision avoidance ECU  60  will be described later. Each of the ECUs is configured as a computer, and includes an arithmetic processor (not illustrated) such as a central processing unit (CPU), and a storage (storage  65  in the collision avoidance ECU  60 ) including a read-only memory (ROM), a random access memory (RAM), or a flash memory. 
     The arithmetic processor reads a program stored (installed) in a nonvolatile storage (such as a ROM or a flash memory), executes calculations according to the program, and serves as each of the ECUs. In particular, the collision avoidance ECU  60  functions (operates) as the respective elements illustrated in  FIG. 2  (to be described later). The storage can store, for example, data (such as tables (data groups) and functions) used in various calculations for the controls, and results of calculations (including values under calculation). 
     The configuration of the vehicle  100  described above is merely an example, and can be modified in various forms. Known devices can be used as the individual units of the vehicle  100 . The elements of the vehicle  100  can be shared with each other. The vehicle  100  can include a sonar to detect the object to be avoided. 
     The following describes the details of the collision avoidance ECU  60 .  FIG. 2  is a block diagram illustrating an exemplary functional configuration of the collision avoidance ECU  60  according to the present embodiment. The collision avoidance ECU  60  of the present embodiment can function (operate) as a determiner  61 , a collision avoidance controller  66 , an alarm controller  62 , a notification controller  63 , and an avoidance braking controller  64 , as illustrated in  FIG. 2 , through cooperation between hardware and software (program). That is, the program can include modules corresponding to the blocks excluding the storage  65 , illustrated in  FIG. 2 , as an example. The alarm controller  62 , the notification controller  63 , and the avoidance braking controller  64  are examples of a collision avoidance executor. The storage  65  stores, for example, various thresholds, and various flags (to be described later). 
     The collision avoidance controller  66  controls execution of the collision avoidance function. The collision avoidance function is a function to maintain a certain relative distance between the preceding vehicle as the object to be avoided and the vehicle so as to avoid collision with the preceding vehicle. The collision avoidance function specifically includes avoidance braking, notifying, and alarming. The avoidance braking is also called automatic braking to apply a brake to the vehicle  100  with the brake ECU  12  and the brake controller  30  to maintain the relative distance between the preceding vehicle and the vehicle  100 . The notifying is outputs of sound from a speaker (not illustrated) provided, for example, ahead of the driver&#39;s seat, indicating that the avoidance braking is to be activated. The alarming is outputs of sound from the speaker (not illustrated), urging the activation of the avoidance braking. The notifying and the alarming differ in output sound. 
     Processing in each step of the collision avoidance function is performed in the following manner.  FIG. 3  is a flowchart of a procedure of executing the collision avoidance function according to the present embodiment. 
     First, the collision avoidance controller  66  inputs a time to collision TTC as an estimated time to collide with the preceding vehicle calculated by the determiner  61  (S 11 ). The determiner  61  can calculate the time to collision TTC by Expression (2) based on equation of motion (1) given below. 
     
       
         
           
             
               
                 
                   
                     
                       
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                        
                       
                         t 
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                         V 
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                        
                       t 
                     
                     + 
                     
                       X 
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                   = 
                   0 
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
             
               
                 
                   t 
                   = 
                   
                     
                       
                         - 
                         
                           V 
                           AB 
                         
                       
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                             V 
                             AB 
                             2 
                           
                           - 
                           
                             2 
                              
                             
                               α 
                               AB 
                             
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                               X 
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     Here, t denotes the time to collision TTC. V AB  denotes the relative speed of the vehicle with respect to the preceding vehicle. X AB  denotes the relative distance from the vehicle to the preceding vehicle. α AB  denotes the relative acceleration of the vehicle with respect to the preceding vehicle. The determiner  61  calculates V AB  based on a result of the detection of any of the wheel speed sensors  41 , calculates α AB  based on a result of the detection of the acceleration sensor  43 , and calculates X AB  based on a result of the detection of the radar  52 . 
     If the value of t or the value in the square root operator in Expression (2) is negative, the collision avoidance controller  66  calculates t as the time to collision TTC by the following expression. 
     
       
      
       t=X 
       AB 
       /V 
       AB  
      
     
     Then, the collision avoidance controller  66  determines whether the input time to collision TTC is equal to or smaller than a certain avoidance braking threshold (S 12 ). When determining that the time to collision TTC is equal to or smaller than the avoidance braking threshold (Yes at S 12 ), the collision avoidance controller  66  transmits an avoidance braking command to the avoidance braking controller  64  to activate the avoidance braking (S 13 ). That is, upon receiving the command, the avoidance braking controller  64  instructs the brake ECU  12  to apply a brake. Thus, the brake controller  30  applies braking. 
     If the time to collision TTC is greater than the avoidance braking threshold (No at S 12 ), the collision avoidance controller  66  determines whether the time to collision TTC is equal to or smaller than a certain notification threshold (S 14 ). The notification threshold is lower than the avoidance braking threshold. Determining that the time to collision TTC is equal to or smaller than the notification threshold (Yes at S 14 ), the collision avoidance controller  66  transmits a notification command to the notification controller  63  to issue a notification (S 15 ). That is, the notification controller  63  outputs a message of activation of the avoidance braking from the speaker. 
     Determining that the time to collision TTC is greater than the notification threshold (No at S 14 ), the collision avoidance controller  66  determines whether the time to collision TTC is equal to or smaller than a certain alarm threshold (S 16 ). The alarm threshold is lower than the notification threshold. Determining that the time to collision TTC is equal to or smaller than the alarm threshold (Yes at S 16 ), the collision avoidance controller  66  transmits an alarm command to the alarm controller  62  to issue an alarm (S 17 ). That is, the alarm controller  62  outputs a message of an urgent need for the avoidance braking from the speaker. 
     Determining that the time to collision TTC is greater than the alarm threshold (No at S 16 ), the collision avoidance controller  66  determines whether to continue the alarm, the notification, or the avoidance braking (step S 18 ). The continuance determination on the alarm, the notification, or the avoidance braking is a process to determine whether to continue the control of the alarm, the notification, or the avoidance braking when the time to collision TTC is increased by, for example, a deceleration of the vehicle or an advance of the preceding vehicle. 
     After determining the continuance of the alarm, the notification, or the avoidance braking or after activating the alarm, the notification, or the avoidance braking, the collision avoidance controller  66  determines whether to inhibit or end the execution of the collision avoidance function (S 19 ). This determination is a process to determine whether to inhibit or end the execution of the collision avoidance function including alarming, notifying, and avoidance braking based on a turning parameter related to turning of the vehicle  100 . Examples of the turning parameter include, but are not limited to, the lateral acceleration Gy (lateral G), the yaw rate, and a differential value of the lateral acceleration during the turning of the vehicle  100 . 
     The following describes the inhibition or ending determination on the execution of the collision avoidance function of the present embodiment. 
     Referring back to  FIG. 2 , the determiner  61  determines whether the vehicle  100  can avoid collision with the object to be avoided as the preceding vehicle. Specifically, the driver operates the steering through the steering system  50  to avoid collision with the object to be avoided as the preceding vehicle and turn the vehicle  100 . The lateral acceleration Gy (or the yaw rate) that actually occurs by the turning of the vehicle  100  is the turning parameter. The determiner  61  determines whether the lateral acceleration Gy (or the yaw rate) is equal to or greater than a certain first threshold so as to determine whether the vehicle  100  can avoid collision with the object to be avoided. The lateral acceleration Gy is detected by the acceleration sensor  43 , and the yaw rate is detected by the yaw rate sensor  46 . The differential value of the lateral acceleration may alternatively be used as the turning parameter. 
     If the lateral acceleration Gy (or the yaw rate) of the vehicle  100  is equal to or greater than the first threshold, the collision avoidance controller  66  determines that the vehicle  100  can avoid collision with the object to be avoided and controls the relevant controllers to inhibit or end the execution of the collision avoidance function (alarm, notification, or avoidance braking). That is, in this case, the collision avoidance controller  66  does not transmit an activation command to any of the alarm controller  62 , the notification controller  63 , and the avoidance braking controller  64 , regardless of the value of the time to collision TTC. 
       FIG. 4  is a schematic diagram illustrating an example of overtaking the preceding vehicle in the present embodiment. Assumed that during traveling of the vehicle  100 , the driver steps on the accelerator pedal AP, aiming to overtake or slip by a preceding vehicle  501 . In this case, decreasing the inter-vehicle distance to the preceding vehicle  501  and the time to collision TTC, the vehicle  1  enters a collision unavoidable region  503  unless the collision avoidance function (alarm, notification, or avoidance braking) is activated. That is, the time to collision TTC falls to the threshold or less, which activates the collision avoidance function and hinders the driver from overtaking or slipping by the preceding vehicle  501  contrary to his/her intention, even if the driver operates the steering. 
     In view of this, in the present embodiment, when the lateral acceleration Gy (or the yaw rate) of the vehicle  100  when turned by steering is equal to or greater than the first threshold, the collision avoidance controller  66  determines that the vehicle  100  sufficiently turns for avoiding the collision, and refrains from activating the collision avoidance function (alarm, notification, or avoidance braking) so as to allow the vehicle  100  to overtake or slip by the preceding vehicle. 
     The determination on the sufficiency of the turning for avoiding the collision can be made based on the steering amount of the steering. However, depending on, for example, a road surface condition and a tire condition, the vehicle  100  may not be able to sufficiently change the course even when detecting a sufficient steering amount by the steering for the collision avoidance during normal running. Such a situation is exemplified by a driver&#39;s steering operation when the vehicle is traveling on a road surface with a low coefficient of friction during raining or snowing, or when temporary-use tires (spare tires) narrower than normal tires are fitted on the vehicle  100 . 
     That is, under such a situation the vehicle  100  may not be able to sufficiently change the course even when detecting, by the steering angle sensor  45 , a sufficient steering amount for the collision avoidance during normal running on a dry asphalt road surface. In such cases, the collision avoidance controller  66  determines from the detected steering amount that the vehicle  100  can avoid collision, and terminates the control of the avoidance braking, which may make it difficult for the vehicle  100  to avoid collision with the preceding vehicle, as a result. 
     In such cases, it is preferable not to end the avoidance braking in response to the steering operation. Because of this, in the present embodiment, the collision avoidance controller  66  determines the sufficient or insufficient turning of the vehicle for avoiding the collision, that is, execution, and inhibition and ending thereof, based not on the steering amount by the steering but on the turning parameter during the actual turning of the vehicle  100 . 
     The turning parameter representing an actual turning varies depending on, for example, a road surface condition or a tire condition. Hence, the collision avoidance controller  66  compares such a turning parameter reflecting the actual turning state of the vehicle with the certain first threshold, and determines whether the turning is sufficient for avoiding the collision, thereby more accurately activating the collision avoidance and ending or inhibiting thereof. 
     The first threshold is set according to the time to collision TTC of the vehicle  100  with respect to the object to be avoided, such as the preceding vehicle.  FIG. 5  is a diagram illustrating an exemplary relation between the time to collision TTC and a lateral acceleration necessary for the collision avoidance in the present embodiment. In  FIG. 5 , the horizontal axis represents the time to collision TTC of the vehicle  100  with respect to the object to be avoided, and the vertical axis represents a lateral acceleration G yth  necessary for the collision avoidance. As understood from  FIG. 5 , the lateral acceleration G yth  necessary for the collision avoidance decreases as the time to collision TTC increases. The lateral acceleration G yth  corresponding to the time to collision TTC represents the lateral acceleration Gy with which the lateral moving distance of the vehicle  100  is estimated to be sufficient for avoiding collision relative to the lateral width of the object to be avoided. 
     Such a relation between the time to collision TTC and the lateral acceleration G yth  necessary for the collision avoidance is stored in advance as a table in the storage  65 . The determiner  61  of the present embodiment calculates the time to collision TTC based on the relative speed V AB , the relative distance X AB , and the relative acceleration α AB  with respect to the preceding vehicle that are calculated based on the detection signals from the radar device  52 , the acceleration sensor  43 , and any of the wheel speed sensors  41 . The determiner  61  refers to the table stored in the storage  65  to determine the lateral acceleration G yth  corresponding to the time to collision TTC as the first threshold, and compares the first threshold with the lateral acceleration Gy of the vehicle  100 . 
     During the execution of the collision avoidance function, the determiner  61  determines, based on the steering of the driver, whether the driver clearly intends to cancel the collision avoidance function. Specifically, the determiner  61  determines whether a steering speed of the driver with the steering system  50  is equal to or greater than a certain second threshold. The steering speed matching or exceeding the certain second threshold signifies a large sudden steering unlike a normal steering. The determiner  61  determines such steering as exhibiting the driver&#39;s clear intention to cancel the execution of the collision avoidance function. 
     During the execution of the collision avoidance function, if the determiner  61  determines that the steering speed is equal to or greater than the certain second threshold, the collision avoidance controller  66  determines that the driver clearly intends to cancel, and ends the execution of the collision avoidance function. 
     When activating the collision avoidance function (alarm, notification, or avoidance braking), the collision avoidance controller  66  stores, as a flag, information indicating which item of the collision avoidance function, that is, alarm, notification, and avoidance braking is executed, in the storage  65 . The determiner  61  determines whether the avoidance braking is working with reference to the flag in the storage  65 . 
     For example, the collision avoidance function (alarm, notification, or avoidance braking) may be activated in a situation that the driver does not feel the need for the collision avoidance, upon erroneously identifying the object to be avoided in a closer distance than an actual distance due to a failure of the vehicle  100 . For another example, the minimum value of the first threshold is set taking an error and noise into account. However, during a very low-speed running of the vehicle  100 , a driver&#39;s minimum steering for avoiding collision may not reach the first threshold as expected because of a too small lateral acceleration Gy or yaw rate as the turning parameter. 
     In the present embodiment, upon recognizing an unusual situation, such as a failure of the vehicle  100 , through the alarm or notification, to forcibly stop the collision avoidance function, the driver largely operates the steering at an unusually higher speed to clearly show his/her intention to cancel the executed collision avoidance function. Thereby, the steering speed increases to the second threshold or above, and the determiner  61  determines the steering speed as being the second threshold or above, which enables cancellation of the execution of the collision avoidance function under the unusual situation described above. 
     The following describes a flow of such a determination on inhibition or ending of the execution of the collision avoidance function (S 19  of  FIG. 3 ) according to the present embodiment.  FIG. 6  is a flowchart of an exemplary procedure of the determination on inhibition or ending of the execution of the collision avoidance function according to the present embodiment. The process in  FIG. 6  is executed individually when the avoidance braking is activated at S 13  of  FIG. 3 , when the notification is issued at S 15 , and when the alarm is issued at S 17 . Although the process illustrated in  FIG. 6  uses the lateral acceleration G for the turning parameter by way of example, the same applies to the yaw rate or the differential value of the lateral acceleration as the turning parameter. 
     As described above, the determiner  61  calculates the time to collision TTC based on the relative speed V AB , the relative distance X AB , and the relative acceleration α AB  (S 34 ), and determines the first threshold (S 30 ). When the driver operates the steering, the determiner  61  determines whether the lateral acceleration Gy of the turning vehicle  100  is equal to or greater than the first threshold (S 31 ). When the lateral acceleration is equal to or greater than the first threshold (Yes at S 31 ), the collision avoidance controller  66  inhibits and ends the issuances of the alarm and the notification, and inhibits the activation of the avoidance braking (S 33 ). 
       FIG. 7  depicts diagrams illustrating relations of the deceleration by the avoidance braking and the turning parameters in the present embodiment.  FIG. 7( a )  illustrates a temporal change in deceleration caused by the avoidance braking.  FIG. 7( b )  illustrates a temporal change in the lateral acceleration Gy, and  FIG. 7( c )  illustrates a temporal change in the differential value of the lateral acceleration Gy. 
     As illustrated in  FIG. 7( a ) , the deceleration rises by the activation of the avoidance braking and maintains at a constant value. At the time when the lateral acceleration Gy of the vehicle  100  reaches or exceeds the first threshold, the avoidance braking is ended, decreasing the deceleration. When the differential value dGy/dt of the lateral acceleration Gy of the vehicle  100  reaches or exceeds the first threshold as illustrated in  FIG. 7( c ) , the avoidance braking is ended as illustrated in  FIG. 7( a ) , decreasing the deceleration. 
     Referring back to  FIG. 6 , if at S 31  the lateral acceleration Gy is smaller than the first threshold (No at S 31 ), the collision avoidance controller  66  does not inhibit or end but continues the execution of the collision avoidance function. 
     The determiner  61  determines whether the steering speed of the driver is equal to or greater than the second threshold so as to determine whether the driver clearly intends to cancel the executed collision avoidance function (S 32 ). The determiner  61  sets the second threshold to a value greater than a normal value of the steering speed. 
     If the steering speed is equal to or greater than the second threshold (Yes at S 32 ), the determiner  61  determines that the driver&#39;s steering clearly shows his/her intention of cancellation. The collision avoidance controller  66  inhibits and ends the issuances of the alarm and the notification, and inhibits the activation of the avoidance braking (S 33 ). 
     If at S 32  the steering speed is smaller than the second threshold (No at S 32 ), the determiner  61  determines that the driver&#39;s steering does not show his/her clear intention of cancellation. The collision avoidance controller  66  does not inhibit and end but continues the executed collision avoidance function (alarm, notification, or avoidance braking). This is because at the timing at which the collision avoidance function is activated, the vehicle  100  faces an increased danger, reaching the region where the collision avoidance by the steering is physically difficult, thus, the collision avoidance function needs to be activated. Then, the process ends. 
     Thus, when the driver operates the steering with the steering system  50  to avoid the collision with the object to be avoided, the present embodiment determines as to whether the turning of the vehicle is sufficient for avoiding the collision, that is, as to whether to inhibit or end the execution of the collision avoidance function, based not on the steering amount by the steering, but on the turning parameter representing the actual turning of the vehicle  100  by the steering. Because of this, it is possible to determine whether the turning is sufficient for avoiding the collision, taking influences of road surface conditions and tire conditions into account, and to more accurately inhibit or end the collision avoidance than determining the sufficiency of the turning based on the steering amount by the steering. Thereby, the present embodiment can more reliably avoid collision. 
     The present embodiment determines a driver&#39;s clear intention to cancel the executed collision avoidance function from a driver&#39;s large steering at an unusual speed, and forcibly avoids the collision avoidance function such as the avoidance braking. As a result, the present embodiment can prevent unnecessary continuance of the collision avoidance function under the unusual situation such as the failure of the vehicle  100 . 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions. 
     EXPLANATIONS OF LETTERS OR NUMERALS 
     
         
         
           
               12  Brake electronic control unit (ECU) 
               13  Engine ECU 
               20  Engine 
               30  Brake controller 
               40  Control device 
               41  ( 41   fr ,  41   fl ,  41   rr , and  41   rl ) Wheel speed sensors 
               42  Brake switch 
               43  Acceleration sensor 
               44  Accelerator pedal stroke sensor 
               45  Steering angle sensor 
               46  Yaw rate sensor 
               60  Collision avoidance ECU 
               61  Determiner 
               62  Alarm control unit 
               63  Notification controller 
               64  Avoidance braking controller 
               65  Storage 
               66  Collision avoidance controller 
               100  Vehicle