Patent Publication Number: US-2023140476-A1

Title: Driving support device

Description:
TECHNICAL FIELD 
     The present disclosure relates to a driving assistance apparatus of assisting the driving of a 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 vehicle with respect to the vehicle, the inter-vehicle distance between the vehicle and the leading vehicle, 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 between the vehicle and the leading vehicle are maintained to be constant. 
     In the ACC, in general, cruise control that controls the speed of own car to a set vehicle speed that is preset is performed when there are no leading cars. 
     CITATION LIST 
     Patent Literature 
     Ptl 1 
     Japanese Patent Application Laid-Open No. HEI 7-17295 
     SUMMARY OF INVENTION 
     Technical Problem 
     The ACC of the related art is not actuated at 40 km/h or less, for example. However, a recent trend is to actuate the ACC even while the vehicle is stopped. Therefore, there is a need to realize ACC that also takes the stoppage of the vehicle into consideration. 
     Meanwhile, when brake control that stops the vehicle is performed, there is a risk that a jerk may occur. In particular, large cars have heavy vehicle weight, and hence need a strong brake force. As a result, a jerk easily occurs. 
     However, in the ACC of the related art, the relationship between the target deceleration speed and a jerk has not been sufficiently examined. 
     The present disclosure has been made in view of the abovementioned points and provides a driving assistance apparatus capable of suppressing a jerk by a simple configuration when ACC is performed. 
     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 between own car and a leading car;   a relative-speed detection section that detects a relative speed between the own car and the leading car; and   a target-acceleration/deceleration-speed output section that outputs a target acceleration/deceleration speed of the own car on basis of the inter-vehicle distance and the relative speed, wherein:   the target-acceleration/deceleration-speed output section includes: 
   an acceleration/deceleration-speed output section that outputs an acceleration/deceleration speed including a deceleration speed on basis of the inter-vehicle distance from the own car to the leading car and the relative speed between the own car and the leading car; and   a cancel section that cancels a deceleration speed that causes a jerk to occur from the deceleration speed output from the acceleration/deceleration-speed output section, and wherein   
   the target-acceleration/deceleration-speed output section outputs an acceleration speed output from the acceleration/deceleration-speed output section and a deceleration speed obtained by the cancel section, as a target acceleration/deceleration speed.   

     Advantageous Effects of Invention 
     According to the present disclosure, the target deceleration speed obtained by canceling the deceleration speed that causes a jerk to occur by the cancel section in advance is output. Therefore, it is possible to suppress a jerk by a simple configuration when the ACC is performed. 
    
    
     
       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    illustrates a situation where own vehicle during ACC approaches another vehicle that is being stopped; 
         FIGS.  4 A and  4 B  illustrate a state until the own vehicle stops by performing deceleration control in which  FIG.  4 A  illustrates the relationship between the own vehicle and the other vehicle until the own vehicle stops and  FIG.  4 B  is a graph showing the relationship between the travel distance and the own car speed from when vehicle-stopping control is started to when the vehicle stops; and 
         FIG.  5    is a block diagram illustrating the configuration of the driving assistance apparatus according to 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’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 . In particular, driving assistance apparatus  30  of the present embodiment obtains 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 performing ON/OFF control of the operation of the ACC. ACC operation section  41  includes setting switches for setting 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 switches. 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 from information output section  50 . For example, information output section  50  outputs that sound and display, to thereby indicate that the ACC is being executed or the ACC is being stopped. 
     &lt;2&gt; Deceleration Control at Time of ACC 
     Next, deceleration control at the time of the ACC according to the present embodiment is described. 
     In the present embodiment, as illustrated in  FIG.  3   , a situation where own vehicle  1  during the ACC approaches other vehicle  100  that is being stopped is supposed. The shaded pattern in the drawing indicates a detection range by the millimeter-wave radar. As can be seen from the drawing, other vehicle  100  is not a vehicle that own vehicle  1  has been following but is a vehicle that suddenly enters the detection range of the millimeter-wave radar when own vehicle  1  is traveling while the ACC is active. 
       FIGS.  4 A and  4 B  illustrate a state until own vehicle  1  stops by performing deceleration control with respect to such other vehicle  100 .  FIG.  4 A  illustrates the relationship between own vehicle  1  and the other vehicle until own vehicle  1  stops and  FIG.  4 B  is a graph showing the relationship between travel distance D and own car speed v from when vehicle-stopping control is started to when the vehicle stops. 
     Vehicle  1  starts deceleration control at time point t1. In other words, other vehicle  100  has entered the detection range of the millimeter-wave radar at time point t1. A zone from time point t1 to time point t2 is a zone referred to as a designated acceleration/deceleration zone, and vehicle  1  performs traveling at a certain speed or fuel cut in accordance with own vehicle speed v in the zone. 
     Vehicle  1  eventually outputs basic deceleration speed α0 at time point t2 at which inter-vehicle distance Dstart at which acceleration/deceleration is to be started is reached. Inter-vehicle distance Dstart can be expressed by the following expression, where a target stopping inter-vehicle distance is represented by Dstop, the own vehicle speed is represented by v, and the basic deceleration speed is represented by α0. 
     
       
         
           
             Dstart= 
             
               
                 
                   
                     
                       v 
                       2 
                     
                   
                 
               
               / 
               
                 
                   
                     2 
                     α0 
                   
                 
               
             
             + 
             Dstop 
           
         
       
     
     Thus, as indicated by dotted line in  FIG.  4 B , own vehicle speed v becomes smaller as travel distance D becomes greater, and own vehicle speed v is supposed to reach 0 at time point t4 when target stopping inter-vehicle distance Dstop is reached. 
     However, in practice, the brake does not start to work from time point t2 at which first basic deceleration speed α0 is output, and starts to work from time point t3 at which a predetermined amount of time has elapsed. This is because there is a mechanical delay before the brake actually starts to work after a control signal is input. For example, in a disc brake, a certain amount of time (normally, an amount of time of about several milliseconds) is needed for the brake to start working as a result of a brake pad being pressed against a disc rotor by oil pressure after a control signal based on the target deceleration speed is input. 
     As a result, when the ACC control of the related art is performed, the relationship between actual travel distance D and own vehicle speed v will not be the relationship indicated by the dotted line in  FIG.  4 B , and a jerk occurs in many cases as indicated by the solid line. 
     In other words, as indicated by the solid line, the brake is not practically working from time point t2 to time point t3. Therefore, at time point t3 at which the brake starts to work, own vehicle speed v hardly changes from time point t2 and only the inter-vehicle distance becomes shorter. Therefore, at time point t3, vehicle  1  outputs deceleration speed α1 greater than basic deceleration speed α0 as the deceleration speed of the ACC. 
     When an instruction of basic deceleration speed α0 is given when the brake is starting to work, the speed of vehicle  1  slowly decreases as indicated by the dotted line. However, when an instruction of deceleration speed α1 greater than basic deceleration speed α0 is given when the brake is starting to work, own vehicle speed v rapidly decreases as indicated by the solid line. When own vehicle speed v rapidly decreases, the stop position of own vehicle  1  becomes a position behind the target vehicle-stop position. Therefore, in order to prevent the above, a value of which deceleration is small is output as the next deceleration speed, and a zone in which the deceleration is gentle is provided as illustrated by the solid line. In this way, a change in the deceleration speed, that is, a so-called jerk occurs at the time of deceleration. 
     &lt;3&gt; Configuration and Operation of Driving Assistance Apparatus of Embodiment 
       FIG.  5    is a block diagram illustrating the configuration of driving assistance apparatus  30  of the present embodiment. 
     Driving assistance apparatus  30  has inter-vehicle-distance detection section  101 , relative-speed detection section  102 , and target-acceleration/deceleration-speed output section  110 . 
     Inter-vehicle-distance detection section  101  and relative-speed detection section  102  respectively measure (detect) the inter-vehicle distance and the relative speed between own vehicle  1  and a leading car on the basis of information obtained by the millimeter-wave radar, the camera, and the like, and output the measurement results to target-acceleration/deceleration-speed output section  110 . Inter-vehicle-distance detection section  101  and relative-speed detection section  102  may measure inter-vehicle distance and the relative speed on the basis of information from other sensors such as a laser radar. 
     Target-acceleration/deceleration-speed output section  110  outputs the target acceleration/deceleration speed for causing own car to follow the leading car on the basis of the inter-vehicle distance and the relative speed between the own car and the leading car. As a result, automatic following traveling control is realized. When there are no leading cars, target-acceleration/deceleration-speed output section  110  outputs a target acceleration speed for causing the speed of the own car to be a set certain speed. As a result, constant-speed traveling control is realized. 
     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 vehicle 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 vehicles in a predetermined range. 
     Target-acceleration/deceleration-speed output section  110  performs the vehicle-stopping control as that illustrated in  FIG.  4 A  when other vehicle  100  that is being stopped is present ahead. The features of target-acceleration/deceleration-speed output section  110  of the present embodiment are mainly in parts relating to the vehicle-stopping control. Therefore, configurations and operations relating to the vehicle-stopping control are mainly described below. 
     Target-acceleration/deceleration-speed output section  110  of the present embodiment has acceleration/deceleration-speed output section  111  that outputs the acceleration/deceleration speed including the deceleration speed on the basis of the inter-vehicle distance from the own car to the leading car and the relative speed between the own car and the leading car, and cancel section  112  that cancels at least a deceleration speed that causes a jerk to occur from the deceleration speed output from acceleration/deceleration-speed output section  111  when roughly divided. 
     In this way, a rapid deceleration when the brake starts to work (time point t3) as that indicated by the solid line in  FIG.  4 B  can be suppressed. As a result, a jerk can be suppressed. 
     In the case of the present embodiment, cancel section  112  has jerk map  113  and subtraction section  114 . 
     In jerk map  113 , the deceleration speed for canceling a jerk that occurs in association with the deceleration speed and the own vehicle speed is stored. 
     Subtraction section  114  subtracts the deceleration speed output from jerk map  113  from the deceleration speed output from acceleration/deceleration-speed output section  111 . 
     A specific description is made. With regard to the example of  FIGS.  4 A and  4 B  described above, at time point t3, deceleration speed α1 is output as the target deceleration speed at the time of own vehicle speed v. As a result, a jerk occurs. Difference Δα between the greatest deceleration speed (the expression of “great” in this case means to be great in the deceleration direction) at which a jerk does not occur at the time of own vehicle speed v and deceleration speed α1 is stored in jerk map  113 . Difference Δα can be obtained by a test in advance. Difference Δα can also be obtained from an equation of motion and the like. 
     In other words, jerk map  113  outputs difference Δα when own vehicle speed v is input from a speed sensor (not shown) and deceleration speed α1 is input from acceleration/deceleration-speed output section  111  at time point t3. 
     Subtraction section  114  subtracts difference Δα output from jerk map  113  from deceleration speed α1 output from acceleration/deceleration-speed output section  111 . The expression of “subtract” herein means to remove (cancel). As a result, the greatest deceleration speed (the expression of “great” in this case means to be great in the deceleration direction) at which a jerk does not occur at the time of own vehicle speed v is output from subtraction section  114  as the target deceleration speed. The target deceleration speed is transmitted to brake ECU  24  ( FIG.  2   ). 
     The acceleration speed output from acceleration/deceleration-speed output section  111  is transmitted to brake ECU  24  ( FIG.  2   ) as it is without being subtracted by subtraction section  114 . 
     &lt;4&gt; Effects of Embodiment 
     As described above, according to the present embodiment, target-acceleration/deceleration-speed output section  110  includes: acceleration/deceleration-speed output section  111  that outputs the acceleration/deceleration speed including the deceleration speed on the basis of the inter-vehicle distance from the own car to the leading car and the relative speed between the own car and the leading car; and cancel section  112  that cancels deceleration speed (difference) Δα that causes a jerk to occur from the deceleration speed output from acceleration/deceleration-speed output section  111 , and target-acceleration/deceleration-speed output section  110  outputs the acceleration speed output from acceleration/deceleration-speed output section  111  and the deceleration speed obtained by cancel section  112  as the target acceleration/deceleration speed. 
     As a result, a speed obtained by canceling deceleration speed (difference) Δα that causes a jerk to occur by cancel section  112  in advance is output as the target deceleration speed. Therefore, it is possible to suppress a jerk by a simple configuration when the ACC is performed. 
     The abovementioned embodiment is characterized in that the deceleration speed is adjusted in consideration of the jerk amount. In particular, when stopped vehicle  100  is present ahead during the ACC, for example, a strong brake based on target deceleration speed α1 is excessively applied when the brake starts to work (time point t3), thereby causing a jerk to occur. Thus, in the present embodiment, by removing (canceling) deceleration speed (difference) Δα from target deceleration speed α1, the initial brake force is weakened. 
     &lt;5&gt; Other Embodiments 
     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. 
     &lt;5-1&gt; In the abovementioned embodiment, a case where cancel section  112  is configured by jerk map  113  and subtraction section  114  is described, but the configuration of cancel section  112  is not limited to the above. In short, cancel section  112  only needs to be able to remove the deceleration speed that causes a jerk to occur from the deceleration speed output from acceleration/deceleration-speed output section  111 . For example, a certain value may be subtracted from the deceleration speed output from acceleration/deceleration-speed output section  111  such that the deceleration becomes smaller (in other words, the deceleration becomes slower). 
     &lt;5-2&gt; In addition to the abovementioned embodiment, cancel section  112  may be prohibited from performing cancel processing in case of a downhill slope. In other words, when it is detected by the acceleration speed sensor (not shown) and the like that own vehicle  1  is traveling on a downhill slope, target deceleration speed α1 may be output as it is without removing (canceling) deceleration speed (difference) Δα from target deceleration speed α1. In other words, at the time of a downhill slope, even when a strong brake based on target deceleration speed α1 is applied at time point t3, a possibility of a jerk occurring thereby is small. Therefore, target deceleration speed α1 is transmitted to brake ECU  24  as it is. In particular, when deceleration speed (difference) Δα is removed (canceled) from target deceleration speed α1 on a downhill slope, there is a risk that own vehicle  1  cannot be stopped at a target position. Therefore, the prohibition processing is effective. In particular, in large cars such as trucks, the vehicle weight is also heavy. Thus, it is preferred that the cancellation of deceleration speed (difference) Δα be prohibited at the time of a downhill slope. 
     &lt;5-3&gt; In the present embodiment, a case where vehicle  1  to which the driving assistance apparatus 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. 2020-033765) filed on Feb. 28, 2020, the entire content of which is incorporated herein by reference. 
     INDUSTRIAL APPLICABILITY 
     The driving assistance apparatus of the present disclosure is suitable for use as a driving assistance apparatus capable of suppressing a jerk by a simple configuration when ACC is performed. 
     REFERENCE SIGNS LIST 
     
         
           1  Vehicle 
           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 
           101  Inter-vehicle-distance detection section 
           102  Relative-speed detection section 
           110  Target-acceleration/deceleration-speed output section 
           111  Acceleration/deceleration-speed output section 
           112  Cancel section 
           113  Jerk map 
           114  Subtraction section