Patent Publication Number: US-2023150460-A1

Title: Driving assistance device and driving assistance method

Description:
TECHNICAL FIELD 
     The present disclosure relates to a driving assistance apparatus that assists the driving of a vehicle and a driving assistance method of assisting the driving of the vehicle. 
     BACKGROUND ART 
     In recent years, as one technology of assisting the driving of a vehicle, adaptive cruise control (hereinafter referred to as “ACC”) has been gathering attention (for example, see Patent Literature (hereinafter, referred to as PTL 1)). The ACC is a technology of obtaining the vehicle speed of a vehicle, the relative speed of a leading car with respect to the vehicle, the inter-vehicle distance between the vehicle and the leading car, and the like, and controlling a driving system and a braking system of the vehicle such that the vehicle speed and the inter-vehicle distance from the leading car are maintained to be constant. 
     CITATION LIST 
     Patent Literature 
     PTL 1 
     Japanese Patent Application Laid-Open No. HEI 7-17295 
     SUMMARY OF INVENTION 
     Technical Problem 
     A case where another car cuts into a place between a leading car serving as a target and the own car during the execution of the ACC is supposed. In this case, the target of the ACC changes to the other car, and the inter-vehicle distance suddenly becomes shorter as compared to a target inter-vehicle distance. At this time, the own car tries to increase the inter-vehicle distance from the other car to the target inter-vehicle distance by the ACC, and hence a rapid deceleration is performed. In particular, when the other car cuts in while decelerating, the degree of the rapid deceleration becomes even more greater. 
     The present disclosure has been made in view of the abovementioned points and provides a driving assistance apparatus and a driving assistance method capable of suitably ensuring the inter-vehicle distance from a leading car without performing an unnecessary rapid deceleration. 
     Solution to Problem 
     One aspect of a driving assistance apparatus of the present disclosure is an apparatus that assists driving of a vehicle, the driving assistance apparatus comprising: 
     an inter-vehicle-distance detection section that detects an inter-vehicle distance from own car to a leading car; 
     a speed detection section that detects a speed of the leading car; 
     a deceleration-speed detection section that detects a deceleration speed of the leading car; 
     a leading-car braking-distance estimation section that estimates a braking distance of the leading car on basis of the detected speed and deceleration speed; 
     a target-braking-distance calculation section that calculates a target braking distance of the own car on basis of the inter-vehicle distance from the leading car and the braking distance of the leading car; and 
     a braking control section that controls braking of the own car on basis of the target braking distance. 
     One aspect of a driving assistance method of the present disclosure is a method of assisting driving of a vehicle, the driving assistance method comprising: detecting an inter-vehicle distance from own car to a leading car; 
     detecting a speed of the leading car; 
     detecting a deceleration speed of the leading car; 
     estimating a braking distance of the leading car on basis of the speed and the deceleration speed of the leading car; 
     calculating a target braking distance of the own car on basis of the inter-vehicle distance from the leading car and the braking distance of the leading car; and 
     controlling braking of the own car on basis of the target braking distance. 
     Advantageous Effects of Invention 
     According to the present disclosure, it is possible to suitably ensure the inter-vehicle distance from the leading car without performing an unnecessary rapid deceleration. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is an external view illustrating an example of a vehicle to which a driving assistance apparatus according to an embodiment is applied; 
         FIG.  2    is a block diagram illustrating the configuration of the vehicle of the embodiment; 
         FIG.  3    is a view illustrating a state in which a cutting-in car cuts into a place ahead of own car; 
         FIG.  4    is a view illustrating a state of deceleration control when cutting-in occurs at the time of ACC according to the embodiment; 
         FIG.  5    is a block diagram illustrating the configuration of the driving assistance apparatus of the embodiment; and 
         FIG.  6    is a flowchart provided for the description of the operation of the driving assistance apparatus of the embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     One embodiment of the present invention is described in detail below with reference to the accompanying drawings. 
     &lt;1&gt; Configuration of Vehicle 
     First, the configuration of a vehicle including a driving assistance apparatus according to one embodiment of the present disclosure is described. 
       FIG.  1    is an external view illustrating an example of vehicle  1  to which a driving assistance apparatus according to the present embodiment is applied.  FIG.  2    is a block diagram illustrating the configuration of vehicle  1 . Illustration and description are made by focusing on parts relating to the driving assistance apparatus. 
     As illustrated in  FIG.  1   , vehicle  1  is a tractor (traction vehicle) capable of towing trailer  2  as a result of coupling trailer  2  to the tractor. Vehicle  1  has vehicle main-body portion  3  including a power system such as an engine and driving wheels and a driver&#39;s seat, and trailer  2  coupled to vehicle main-body portion  3 . 
     As illustrated in  FIG.  2   , vehicle  1  has driving system  10  that causes vehicle  1  to travel, braking system  20  that decelerates vehicle  1 , driving assistance apparatus  30  that assists the driving of vehicle  1  by a driver, and the like. 
     Driving system  10  has engine  11 , clutch  12 , transmission  13 , propeller shaft  14 , differential gear  15 , drive shaft  16 , wheels  17 , engine ECU  18 , and motive power transmission ECU  19 . 
     Engine ECU  18  and motive power transmission ECU  19  are connected to driving assistance apparatus  30  by an in-vehicle network such as a controller area network (CAN) and are able to transmit and receive necessary data and control signals to and from each other. Engine ECU  18  controls the output of engine  11  in accordance with a drive command from driving assistance apparatus  30 . Motive power transmission ECU  19  controls the connection and disconnection of clutch  12  and the speed change of transmission  13  in accordance with a drive command from driving assistance apparatus  30 . 
     The motive power of engine  11  is transmitted to transmission  13  via clutch  12 . The motive power transmitted to transmission  13  is further transmitted to wheels  17  via propeller shaft  14 , differential gear  15 , and drive shaft  16 . As a result, the motive power of engine  11  is transmitted to wheels  17 , and vehicle  1  travels. 
     Braking system  20  has service brakes  21 , auxiliary brakes  22 ,  23 , a parking brake (not shown), and brake ECU  24 . 
     Service brake  21  is a brake that is generally referred to as a main brake, a friction brake, a foot brake, a foundation brake, or the like. Service brake  21  is a drum brake that obtains braking force by pressing a brake lining against the inner side of a drum that rotates with wheel  17 , for example. 
     Auxiliary brake  22  is a retarder (hereinafter referred to as “retarder  22 ”) that obtains braking force by directly giving load to the rotation of propeller shaft  14 , and is an electromagnetic retarder, for example. Auxiliary brake  23  is an exhaust brake (hereinafter referred to as “exhaust brake  23 ”) that increases an effect of an engine brake with use of rotational resistance of the engine. By providing retarder  22  and exhaust brake  23 , the braking force can be increased, and the frequency of usage of service brakes  21  is reduced. Therefore, the wear-out of brake lining and the like can be suppressed. 
     Brake ECU  24  is connected to driving assistance apparatus  30  by an in-vehicle network such as a CAN and is able to transmit and receive necessary data and control signals to and from each other. Brake ECU  24  controls the braking force of service brakes  21  (the brake fluid pressure of wheel cylinders of wheels  17 ) in accordance with a braking command from driving assistance apparatus  30 . 
     The braking operation of service brakes  21  is controlled by driving assistance apparatus  30  and brake ECU  24 . The braking operation of retarder  22  and exhaust brake  23  is controlled by on/off by driving assistance apparatus  30 . The braking force of retarder  22  and exhaust brake  23  is substantially fixed. Therefore, when a desired braking force is to be accurately generated, service brakes  21  that can fine-adjust the braking force are suitable. 
     Information from a millimeter-wave radar and a camera is input to driving assistance apparatus  30 . Information from the millimeter-wave radar and the camera is information indicating the traffic situation and the road situation ahead of the vehicle. Driving assistance apparatus  30  has ACC operation section  41 , accelerator-operation detection section  43 , brake-operation detection section  44 , and the like. 
     Driving assistance apparatus  30  forms control signals for controlling the operation of driving system  10  and braking system  20 . Specifically, driving assistance apparatus  30  obtains a target acceleration/deceleration speed for realizing ACC and outputs the target acceleration/deceleration speed to engine ECU  18 , motive power transmission ECU  19 , and brake ECU  24 , as appropriate. 
     Although not shown, each of engine ECU  18 , motive power transmission ECU  19 , brake ECU  24 , and driving assistance apparatus  30  has a central processing unit (CPU), a storage medium such as a read only memory (ROM) in which a control program is stored, a working memory such as a random access memory (RAM), and a communication circuit, for example. In this case, for example, the functions of sections described below constituting driving assistance apparatus  30  are realized by executing control programs by the CPU. All or some of engine ECU  18 , motive power transmission ECU  19 , brake ECU  24 , and driving assistance apparatus  30  may be integrated. 
     ACC operation section  41  includes an ACC ON/OFF switch for activating and removing the ACC. ACC operation section  41  includes a setting switch for performing various settings of the ACC. A driver can set a target inter-vehicle distance and a target own-vehicle speed, for example, by operating the setting switch. Those switches may be realized by a user interface displayed on a display with a touch screen. 
     Accelerator-operation detection section  43  detects the depression amount of an accelerator pedal and outputs the detection result to driving assistance apparatus  30 . Driving assistance apparatus  30  transmits drive commands to engine ECU  18  and motive power transmission ECU  19  on the basis of the depression amount of the accelerator pedal. 
     Brake-operation detection section  44  detects the depression amount of a brake pedal for operating service brakes  21 . Brake-operation detection section  44  detects whether an auxiliary brake lever that causes retarder  22  or exhaust brake  23  to operate has been operated. Brake-operation detection section  44  outputs the detection result relating to the brake pedal and the auxiliary brake lever to driving assistance apparatus  30 . Driving assistance apparatus  30  transmits a braking command to brake ECU  24  on the basis of the depression amount of the brake pedal. Driving assistance apparatus  30  controls the ON/OFF operation of retarder  22  or exhaust brake  23  on the basis of the operation of the auxiliary brake lever. 
     Driving assistance apparatus  30  outputs various information relating to traveling and the ACC from information output section  50 . For example, display and sound indicating that the ACC is active or the ACC is removed are output from information output section  50 . 
     &lt;2&gt; Deceleration Control when Cutting-In Occurs at Time of ACC 
     Next, deceleration control when cutting-in occurs at the time of the ACC according to the present embodiment is described. 
       FIG.  3    is a view illustrating a state in which cutting-in car  100  cuts into a place ahead of own car  1 . Cutting-in car  100  travels while decelerating. The expression of “cutting-in” in the present embodiment means that a vehicle different from a vehicle serving as a target enters a position at inter-vehicle distance d that is shorter than target inter-vehicle distance D of the ACC in the same lane as own car  1 . 
       FIG.  4    is a view illustrating a state of the deceleration control when cutting-in occurs at the time of the ACC according to the embodiment. 
     When cutting-in car  100  enters a position at inter-vehicle distance d, own car  1  detects speed v 1  and deceleration speed α 1  of cutting-in car  100 . Own car  1  estimates braking distance d 1  of cutting-in car  100  by the following expression with use of speed v 1  and deceleration speed α 1  of cutting-in car  100 . 
         d   1 =( v   1   2 )/(2α 1 )  (Expression 1)
 
     Next, own car  1  calculates target braking distance d t  of own car  1 . Target braking distance d t  is a braking distance required for the vehicle to stop at a position behind a vehicle-stop position of cutting-in car  100  by target inter-vehicle stopping distance d s . Target braking distance d t  can be calculated by the following expression. 
         d   t =( v   1   2 )/(2α 1 )+ d−d   s   (Expression 2)
 
     Own car  1  controls the braking of the own car such that own car  1  stops at a position at a target braking distance. 
     &lt;3&gt; Configuration of Driving Assistance Apparatus 
       FIG.  5    is block diagram illustrating the configuration of driving assistance apparatus  30  of the present embodiment. 
     Driving assistance apparatus  30  has ACC section  31 , inter-vehicle-distance detection section  32 , deceleration-speed detection section  33   a , speed detection section  33   b , leading-car braking-distance estimation section  34 , target-braking-distance calculation section  35 , and braking control section  36 . 
     ACC section  31  realizes automatic following control by outputting a target acceleration/deceleration speed for causing the own car to follow a leading car on the basis of the relative speed and the inter-vehicle distance between the own car and the leading car. When there are no leading cars, ACC section  31  realizes constant speed traveling control by outputting a target acceleration speed for causing the speed of the own car to be a set certain speed. 
     Automatic-following traveling control is control that operates driving system  10  and braking system  20  such that the inter-vehicle distance is within a predetermined target range and the relative speed approaches zero when a leading car is present in a predetermined range. The constant-speed traveling control is control that operates driving system  10  and braking system  20  such that the traveling speed of vehicle  1  approaches a predetermined target value when there are no leading cars in a predetermined range. 
     Inter-vehicle-distance detection section  32  measures (detects) inter-vehicle distance d between own car  1  and the leading car on the basis of information on a place ahead of own car  1  obtained by the millimeter-wave radar, the camera, and the like, and outputs the measurement result to ACC section  31  and target-braking-distance calculation section  35 . Inter-vehicle-distance detection section  32  may measure the inter-vehicle distance d on the basis of information from other sensors such as a laser radar. 
     Deceleration-speed detection section  33   a  detects deceleration speed al of the leading car (cutting-in car  100 ) on the basis of information obtained by the millimeter-wave radar. Specifically, the speed of cutting-in car  100  can be measured two times by the millimeter-wave radar, and deceleration speed al can be calculated on the basis of the difference thereof. 
     Speed detection section  33   b  detects speed v 1  of the leading car (cutting-in car  100 ) on the basis of information obtained by the millimeter-wave radar. Deceleration speed α 1  and speed v 1  of the leading car (cutting-in car  100 ) are detected every 50 [milliseconds], for example. 
     Leading-car braking-distance estimation section  34  estimates braking distance d 1  of the leading car (cutting-in car  100 ) on the basis of detected speed v 1  and deceleration speed α 1 . Specifically, braking distance d 1  is estimated by abovementioned expression 1. 
     Target-braking-distance calculation section  35  calculates target braking distance d t  of own car  1  on the basis of inter-vehicle distance d from the leading car (cutting-in car  100 ) and braking distance d 1  of the leading car (cutting-in car  100 ). Specifically, target braking distance d t  is calculated by abovementioned expression 2. 
     Braking control section  36  controls the braking of the own car such that own car  1  stops at a position at target braking distance d t . Specifically, braking control section  36  outputs a target deceleration speed with which own car  1  stops at a position at target braking distance d t . 
     &lt;4&gt; Operation of Driving Assistance Apparatus 
     Next, an operation of driving assistance apparatus  30  is described. Driving assistance apparatus  30  of the present embodiment is particularly characterized by deceleration control at the time of the ACC. Therefore, the deceleration control when cutting-in occurs at the time of the ACC is mainly described with reference to  FIG.  6   . 
     When driving assistance apparatus  30  detects cutting-in car  100  in Step S 11 , driving assistance apparatus  30  transitions to Step  12 . Cutting-in car  100  can be detected by information from the camera and the like. 
     Driving assistance apparatus  30  determines whether inter-vehicle distance d from the leading car (cutting-in car  100 ) is equal to or less than predetermined threshold value (target inter-vehicle distance) D in Step S 12  and determines whether the leading car (cutting-in car  100 ) is decelerating in Step S 13 . 
     When inter-vehicle distance d from the leading car (cutting-in car  100 ) is equal to or less than threshold value D and the leading car (cutting-in car  100 ) is decelerating, driving assistance apparatus  30  transitions to Step S 14  and performs special ACC. The special ACC is processing as that illustrated in  FIG.  4   , and is processing performed by deceleration-speed detection section  33   a , speed detection section  33   b , leading-car braking-distance estimation section  34 , target-braking-distance calculation section  35 , and braking control section  36 . 
     Meanwhile, driving assistance apparatus  30  transitions to Step S 15  and performs normal ACC by ACC section  31  when inter-vehicle distance d from the leading car is greater than threshold value D or when the leading car is not decelerating. In other words, the braking of the own car is controlled such that inter-vehicle distance d from the leading car reaches target inter-vehicle distance D. 
     Driving assistance apparatus  30  performs the processing of Step S 14  or Step S 15  for a certain predetermined period of time (for example, one second), and then returns to Step S 12  again and repeats similar processing. When cutting-in car  100  starts to travel at a constant speed or starts to accelerate as such processing is repeated, target inter-vehicle distance D is ensured. Therefore, the processing of Step S 14  is not performed, and the processing of Step S 15  is performed. 
     The special ACC of the present embodiment ensures the inter-vehicle distance while supposing the worst case in which cutting-in car  100  is stopped. In other words, the processing of the present embodiment is processing supposing the worst case, but the amount of time for the vehicle to stop can be ensured. Therefore, rapid deceleration can be decreased as compared to a case where inter-vehicle distance d that has become shorter by the cutting-in is increased to target inter-vehicle distance D in a rush as in the normal ACC. 
     &lt;5&gt; Effects of Embodiment 
     As described above, according to the present embodiment, driving assistance apparatus  30  includes: inter-vehicle-distance detection section  32  that detects inter-vehicle distance d from own car  1  to the leading car; speed detection section  33   b  that detects speed v 1  of the leading car; deceleration-speed detection section  33   a  that detects deceleration speed α 1  of the leading car; leading-car braking-distance estimation section  34  that estimates braking distance d 1  of the leading car on the basis of detected speed v 1  and deceleration speed α 1 ; target-braking-distance calculation section  35  that calculates target braking distance d t  of own car  1  on the basis of inter-vehicle distance d from the leading car and braking distance d 1  of leading car  1 ; and braking control section  36  that controls braking of own car  1  on the basis of target braking distance d t . 
     As a result, the inter-vehicle distance from the leading car can be suitably ensured without performing an unnecessary rapid deceleration (that is, a rapid deceleration caused when inter-vehicle distance d is tried to be increased to target inter-vehicle distance D). 
     The abovementioned embodiment is merely an example of a realization for carrying out the present invention, and the interpretation of the technical scope of the present invention is not to be limited by those embodiments. In other words, the present invention can be carried out in various forms without departing from the gist or the main features of the present invention. 
     In the present embodiment, a case where vehicle  1  to which the driving assistance apparatus and method of the present invention is applied is a tractor capable of towing trailer  2  as a result of coupling trailer  2  to the tractor is described. However, the vehicle to which the present invention is applicable is not limited thereto and may be a vehicle such as a passenger car. 
     The present application is based on Japanese Patent Application (Japanese Patent Application No. 2020-33763) filed on Feb. 28, 2020, the entire content of which is incorporated herein by reference. 
     INDUSTRIAL APPLICABILITY 
     The driving assistance apparatus and the driving assistance method of the present disclosure are suitable for use as a driving assistance apparatus and a driving assistance method capable of suitably ensuring the inter-vehicle distance from a leading car without performing an unnecessary rapid deceleration. 
     REFERENCE SIGNS LIST 
     
         
           1  Vehicle (own car) 
           2  Trailer 
           3  Vehicle main-body portion 
           10  Driving system 
           11  Engine 
           12  Clutch 
           13  Transmission 
           14  Propeller shaft 
           15  Differential gear 
           16  Drive shaft 
           17  Wheel 
           18  Engine ECU 
           19  Motive power transmission ECU 
           20  Braking system 
           21  Service brake 
           22  Retarder 
           23  Exhaust brake 
           24  Brake ECU 
           30  Driving assistance apparatus 
           31  ACC section 
           32  Inter-vehicle-distance detection section 
           33   a  Deceleration-speed detection section 
           33   b  Speed detection section 
           34  Leading-car braking-distance estimation section 
           35  Target-braking-distance calculation section 
           36  Braking control section 
           41  ACC operation section 
           43  Accelerator-operation detection section 
           44  Brake-operation detection section 
           50  Information output section