Patent Publication Number: US-2012029766-A1

Title: Driving support device, driving support method, and driving support program

Description:
INCORPORATION BY REFERENCE 
     This application claims priority from Japanese Patent Application No. 2010-172412 filed on Jul. 30, 2010 including the specification, drawings and abstract thereof, the disclosure of which is incorporated herein by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     Aspects of the present invention relate to a driving support device, a driving support method, and a driving support program. 
     DESCRIPTION OF THE RELATED ART 
     According to the related art, a vehicle that includes a motor generator uses the motor generator as a power source during travel, and uses the motor generator as a regenerative brake during vehicle deceleration so as to regenerate electric power, which is stored in a battery. 
     Increasing the amount of electric power regenerated by the regenerative brake can contribute to increasing the energy efficiency of the vehicle. Therefore, in terms of energy efficiency, the regenerative brake should be used as much as possible during vehicle deceleration. However, the braking power of the regenerative brake has an upper limit, and a friction brake is also used for braking when a sudden brake operation by the driver or the like requires braking power that exceeds the upper limit of the regenerative brake. In such cases, part of the kinetic energy of the vehicle is converted into thermal energy by the friction brake, which reduces the amount of electric power that can be regenerated by the regenerative brake compared to deceleration using only the regenerative brake. 
     In view of this, a vehicle driving support device has been proposed that provides the driver with suitable brake operation guidance. This vehicle driving support device extracts map information for a deceleration-requiring point located in the advancing direction of the vehicle based on the current position of the vehicle. Using the extracted map information for the deceleration-requiring point, the vehicle driving support device sets a target vehicle speed at the deceleration-requiring point, and calculates a required deceleration distance for decelerating by a regenerative brake from a current vehicle speed to the target vehicle speed. Once the vehicle reaches a brake start point located before the deceleration-requiring point at the deceleration distance, the brake operation guidance is started (see Japanese Patent Application Publication No. JP-A-2007-221889, for example). 
     SUMMARY OF THE INVENTION 
     However, the device according to the related art as described above does not consider the fact that every driver has a unique driving style, and that there can be variations in the driving style of the same driver. Therefore, this device provides brake operation guidance based on the same brake start point for all drivers. As a consequence, depending on the driver, the timing at which the brake operation guidance is provided may feel delayed. This results in the driver performing a more sudden brake operation than necessary, which may require a braking force that exceeds the upper limit of the regenerative brake and reduce the amount of electric power regenerated by the regenerative brake. 
     The present invention was devised in view of the foregoing circumstances, and provides a driving support device, a driving support method, and a driving support program, which can take into account a driver&#39;s driving style and perform guidance such that electric power is efficiently regenerated by a regenerative brake. 
     According to a driving support device described in a first aspect of the present invention, a driving support method described in a seventh aspect of the present invention, and a driving support program described in an eighth aspect of the present invention, based on electric power regenerated by a regenerative brake in response to a brake operation performed after a guidance unit performs guidance and before a target feature is passed, a new timing at which to perform guidance is set, and guidance is performed anew at the set timing. Therefore, guidance can be performed such that electric power regeneration is efficiently performed by the regenerative brake in consideration of a driving style of a driver. 
     According to a second aspect of the present invention, the new timing at which to perform guidance may be set based on a brake operation performed after the guidance unit performs guidance and before the target feature is passed. Therefore, guidance can be performed such that a suitable brake operation is performed in consideration of the driving style of the driver. 
     According to a third aspect of the present invention, a setting unit may set a new timing at which to perform guidance for each of the target feature types specified by a type specification unit. The guidance unit may perform guidance at the new timing that corresponds to the target feature type specified by the type specification unit among a plurality of new timings set by the setting unit. Therefore, guidance can be performed such that electric power regeneration is efficiently performed by the regenerative brake at a suitable timing in accordance with the target feature type and in consideration of the driving style of the driver. 
     According to a fourth aspect of the present invention, the setting unit may set a new timing at which the guidance unit performs the guidance earlier if the electric power regenerated by the regenerative brake in response to the brake operation reaches a regenerative upper-limit electric power. Therefore, guidance can be performed at the new timing that allows the driver to perform a gentle brake operation without the regenerative electric power reaching the regenerative upper-limit electric power. Thus, guidance can be performed such that the regenerative brake efficiently regenerates electric power. 
     According to a fifth aspect of the present invention, the setting unit may set a new timing at which the guidance unit performs the guidance later if a brake operation is performed following an acceleration operation after the guidance unit performs the guidance and before the target feature is passed. Therefore, guidance can be performed at a new timing at which a vehicle approaches the target feature without requiring that the driver accelerate the vehicle after guidance is performed by the guidance unit. Thus, unnecessary acceleration operations and brake operations can be suppressed. 
     According to a sixth aspect of the present invention, the guidance unit may perform guidance at a median value among the plurality of new timings that corresponds to timing information stored in a timing information storage unit. Therefore, guidance can be performed at the optimal timing in consideration of the driving style of the driver. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram that illustrates circumstances in which a driving support device according to a first embodiment is used; 
         FIG. 2  is a block diagram that illustrates a driving support system according to the first embodiment; 
         FIG. 3  is a table that illustrates information stored in a timing database; 
         FIG. 4  is a flowchart of a driving support process; 
         FIG. 5  is a flowchart continuing from  FIG. 4  of the driving support process; 
         FIG. 6  is a graph that illustrates a relationship between braking power and an elapsed time after a guidance unit starts guidance output; 
         FIG. 7  is a flowchart of a setting process; and 
         FIG. 8  is a table that illustrates information stored in the timing database according to a second embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS 
     Hereinafter, embodiments of a driving support device, a driving support method, and a driving support program according to the various aspects of the present invention will be described in detail with reference to the drawings. However, the scope of the present invention is not limited to such embodiments. Further note that, in the description below, the driving support device is installed in a vehicle that includes a motor generator and a battery, and uses the motor generator as a regenerative brake. 
     First Embodiment 
     First, a driving support device according to a first embodiment will be described. In the first embodiment, a timing at which to perform guidance is set based on a brake operation performed after a guidance unit performs guidance and before a target feature is passed, and electric power regenerated by a regenerative brake in response to the brake operation. 
     First, the driving support device according to the first embodiment will be described.  FIG. 1  is a schematic diagram that illustrates circumstances in which the driving support device according to the first embodiment is used. As shown in  FIG. 1 , when stopping the vehicle at an intersection, for example, the driving support device performs guidance that encourages a brake operation at a suitable timing in consideration of the driver&#39;s driving style, which allows electric power to be efficiently regenerated by the regenerative brake in accordance with the brake operation of the driver. In the description below, features for which the vehicle should be stopped such as intersections, stop lines, and railroad crossings, and features for which the vehicle should be decelerated such as curves, ETC toll booths, and expressway exits will be referred to as “target features”. 
       FIG. 2  is a block diagram that illustrates a driving support system according to the first embodiment. As shown in  FIG. 2 , a driving support system  1  is installed in a vehicle, and includes an electronic control unit (ECU)  10 , a current position detection processing unit  20 , a display  30 , a speaker  40 , and a driving support device  50 . 
     ECU 
     The ECU  10  controls an engine, a motor generator, a battery, and the like of a vehicle (all not shown in the drawings) based on the output of various types of sensors such as a vehicle speed sensor, an accelerator sensor, a brake sensor, and a shift position sensor (all not shown in the drawings). The ECU  10  inputs to the driving support device  50  various types of information such as a vehicle speed, an accelerator operation amount, a brake depression force, and a battery voltage, current, and chargeable electric power. 
     Current Position Detection Processing Unit 
     The current position detection processing unit  20  is a current position detection unit that detects the current position of the vehicle in which the drive support system  1  is installed. Specifically, the current position detection processing unit  20  has at least one of a GPS, a geomagnetic sensor, a distance sensor, and a gyroscopic sensor (all not shown in the drawings), and detects the current position (coordinates), heading, and the like of the vehicle using a commonly known method. 
     Display 
     The display  30  is an output unit that outputs and displays various types of information based on a control of the driving support device  50 . Note that the specific constitution of the display  30  may take on any form, and a flat panel display such as a commonly known liquid crystal display or organic EL display may be used. 
     Speaker 
     The speaker  40  is an output unit that outputs various types of audio based on a control of the driving support device  50 . The specific voice output from the speaker  40  may take on any form, and it is possible to output a synthetic voice that is generated as necessary or output a pre-recorded voice. 
     Driving Support Device 
     The driving support device  50  includes a control unit  51 , and a data storage unit  52 . 
     Driving Support Device—Control Unit 
     The control unit  51  controls the driving support device  50 . Specifically, the control unit  51  is a computer configured to include a CPU, various programs that are interpreted and executed in the CPU (including an OS and other basic control programs, and application programs that are activated in the OS to carry out specific functions), and an internal memory such as a RAM for storing the programs and various data. In particular, the driving support program according to the first embodiment is installed in the driving support device  50  through any storage medium or network, and configures various portions of the control unit  51  in substance. 
     The control unit  51  includes a regenerative electric power specification unit  51   a , a guidance unit  51   b , and a setting unit  51   c  in terms of functional concept. The regenerative electric power specification unit  51   a  determines the electric power regenerated by the regenerative brake. The guidance unit  51   b  performs guidance through the display  30  and the speaker  40  that encourages deceleration of the vehicle. The setting unit  51   c  sets the timing at which the guidance unit  51   b  performs guidance. In other words, the setting unit  51   c  sets a new timing at which the guidance unit  51   b  performs subsequent guidance, and after the vehicle passes a target feature the guidance unit  51   b  performs guidance anew at the new timing set by the setting unit  51   c , which is a timing based on the distance from the vehicle to a subsequent target feature. It should be noted that “setting” includes changing the timing (setting a new timing) at which the guidance unit  51   b  performs guidance depending on various conditions. The processes executed by the various portions of the control unit  51  will be described in detail later. 
     Driving Support Device—Data Storage Unit 
     The data storage unit  52  is a storage unit that stores programs and various data required for operation of the driving support device  50 , and has a configuration that uses a hard disk (not shown) as an external memory device, for example. However, any other storage mediums, including a magnetic storage medium such as a magnetic disk or an optical storage medium such as a DVD or Blu-ray disc, can be used in place of or in combination with the hard disk. 
     The data storage unit  52  has a map information database  52   a  and a timing database  52   b . (Note that database will be abbreviated to “DB” below.) 
     The map information DB  52   a  is a map information storage unit that stores map information. The “map information” is configured to include link data (e.g. link numbers, connection node numbers, road coordinates, road types, number of lanes, travel restrictions), node data (node numbers and coordinates), feature data (e.g. traffic signals, road signs, guard rails, buildings), target feature data (e.g. intersections, stop lines, railroad crossings, curves, ETC toll booths, expressway exits), facility data (e.g. facility locations and facility types), topography data, and map display data for displaying a map on the display  30 . 
     The timing DB  52   b  is a timing information storage unit that stores timing information for specifying a plurality of timings set by the setting unit  51   c .  FIG. 3  is a table that illustrates information stored in the timing DB  52   b . As shown in  FIG. 3 , information that corresponds to the table items “Target Feature ID” and “Set Distance” is mutually associated and stored in the timing DB  52   b . Information stored as corresponding to the table item “Target Feature ID” is identification information that uniquely identifies a target feature for which the setting unit  51   c  sets a guidance timing (“0101” and so forth in  FIG. 3 ). Information that is stored corresponding to the table item “Set Distance” is timing information for specifying a plurality of timings set by the setting unit  51   c . In  FIG. 3 , the timing information is stored as a numerical value that indicates a distance set by the setting unit  51   c  (a “set distance” below), which is a distance between the vehicle and the target feature at the timing when guidance is performed (a “guidance distance” below). Note that in  FIG. 3 , nine set distances are stored in ascending order per target feature ID. 
     Processing: Driving Support Process 
     Next, a driving support process executed by the driving support system  1  thus configured will be described.  FIGS. 4 and 5  are flowcharts of the driving support process (steps in the description of each process below are abbreviated to “S”). The driving support process is executed, for example, after the driving support system  1  is powered on and the vehicle starts traveling. Note that, with regard to whether the vehicle has started traveling, it is determined that the vehicle has started traveling when the shift position changes from a parking position to a drive position, based on input from the ECU  10 , for example. 
     After the driving support process is started, the guidance unit  51   b  identifies the current position of the vehicle through the current position detection processing unit  20 , and based on the target feature data in the map information DB  52   a  searches for target features present ahead of the vehicle on a map (SA 1 ). 
     Next, the guidance unit  51   b  determines whether there is a target feature ahead of the vehicle as a result of searching for target features at SA 1  (SA 2 ). For example, the guidance unit  51   b  determines whether there is a target feature within a predetermined distance in the advancing direction of the road on which the vehicle is currently traveling. 
     If there is a target feature ahead of the vehicle (SA 2 : Yes), that is, if the vehicle has not yet passed the target feature, the guidance unit  51   b  determines whether the setting unit  51   c  has set a timing at which to perform guidance that encourages a brake operation for stopping or decelerating the vehicle before reaching the target feature (SA 3 ). If the target feature ID of a particular target feature ahead of the vehicle is stored in the timing DB  52   b , and if a predetermined quantity of timing information (nine in the example of  FIG. 3 ) is stored associated with that particular target feature ID in the timing DB  52   b , the guidance unit  51   b  determines that the setting unit  51   c  has set a timing at which to perform guidance that encourages a brake operation for stopping or decelerating the vehicle before reaching the target feature. 
     If the setting unit  51   c  has set a timing at which to perform guidance (SA 3 : Yes), based on the timing information stored in the timing DB  52   b  the guidance unit  51   b  sets a set distance as a guidance distance (SA 4 ). In this case, the guidance unit  51   b  sets the guidance distance such that guidance is performed at a median value among the plurality of timings that corresponds to the timing information stored in the timing DB  52   b . In other words, for example, if the target feature ID of a certain target feature ahead of the vehicle is “0101” according to the timing DB  52   b  in  FIG. 3 , 135 meters is the median value among the corresponding nine set distances, and thus set as the guidance distance. 
     Returning to  FIG. 4 , if the determination result at SA 3  is that the timing at which to perform guidance has not been set by the setting unit  51   c  (SA 3 : No), the guidance unit  51   b  sets a predetermined initial value as the guidance distance (SA 5 ). A distance of 150 meters is used as the initial value, which assumes a standard living area and is calculated as the approximate distance the vehicle travels from a vehicle speed of 60 km/h to a stop at a deceleration of 0.1 G on a downhill road with a 5% grade. 
     Following the processing at SA 4  or SA 5 , the guidance unit  51   b  determines whether the distance from the current position of the vehicle to the target feature is equal to or less than the guidance distance set at SA 4  or SA 5  (SA 6 ). Note that the guidance unit  51   b  specifies the distance from the current position of the vehicle to the target feature based on the current position of the vehicle as identified through the current position detection processing unit  20 , and the position of the target feature as acquired from the map information DB  52   a.    
     If the distance from the current position of the vehicle to the target feature is equal to or less than the guidance distance set at SA 4  or SA 5  (SA 6 : Yes), the guidance unit  51   b  turns on a setting start flag (SA 7 ). The setting start flag is a flag for specifying whether a condition for the setting unit  51   c  to start making a setting is satisfied, and stored in a RAM (not shown). 
     Next, the guidance unit  51   b  determines whether voice guidance has been output through the speaker  40  (SA 8 ). If the voice guidance has not been output (SA 8 : No), the guidance unit  51   b  outputs through the speaker  40  voice guidance that encourages deceleration of the vehicle (SA 9 ). For example, the guidance unit  51   b  outputs through the speaker  40  voice guidance such as “Slowly depress the brake pedal at a constant pressure and stop at the target feature.” 
     If voice guidance has been output through the speaker  40  (SA 8 : Yes) or following the processing at SA 9 , the guidance unit  51   b  outputs through the display  30  display guidance that encourages deceleration of the vehicle (SA 10 ). For example, the guidance unit  51   b  displays through the display  30  a message such as “Slowly depress the brake pedal to a set position and stop at the target feature.” The driver receiving the voice guidance output from the speaker  40  at SA 9  and the display guidance output from the display  30  at SA 10  thus performs a brake operation, and electric power is regenerated by the regenerative brake in response to the brake operation. 
     Next, the regenerative electric power specification unit  51   a  determines the electric power regenerated by the regenerative brake in response to the brake operation (SA 11 ). For example, the regenerative electric power specification unit  51   a  determines the regenerative electric power by multiplying the voltage and current of the battery as input from the ECU  10 . 
     Proceeding to  FIG. 5 , the setting unit  51   c  determines whether the regenerative electric power specified by the regenerative electric power specification unit  51   a  has reached a regenerative upper-limit electric power (SA 12 ). The regenerative upper-limit electric power is an upper limit value of electric power that can be regenerated by the regenerative brake, and the setting unit  51   c  performs the determination at SA 12  using the chargeable electric power input from the ECU  10  as the regenerative upper-limit electric power, for example. Note that the chargeable electric power is a value that may vary depending on the battery temperature. 
     If the regenerative electric power specified by the regenerative electric power specification unit  51   a  has reached the regenerative upper-limit electric power (SA 12 : Yes), the braking power required in accordance with the brake operation of the driver exceeds the regenerative upper-limit electric power, and braking by a friction brake is used in addition to the regenerative brake. Thus, the setting unit  51   c  counts up an upper limit time that indicates the time at which the regenerative electric power reached the regenerative upper-limit electric power (SA 13 ). The upper limit time is stored in the RAM, and the setting unit  51   c  adds to the upper limit time stored in the RAM an elapsed time since the previous determination at SA 12  until the current determination at SA 12 . 
       FIG. 6  is a graph that illustrates a relationship between braking power and an elapsed time after the guidance unit  51   b  starts guidance output. In order to facilitate understanding of the relationship between the braking power and the regenerative upper-limit electric power in  FIG. 6 , the braking power is shown in units of kilowatts. In  FIG. 6 , when the guidance distance is 43 meters and 64 meters and the regenerative upper-limit electric power is 20 kilowatts, the braking power exceeds the regenerative upper-limit electric power. In such case, braking by the friction brake is used in addition to the regenerative brake. Therefore, the amount of electric power regenerated by the regenerative brake is less than the amount regenerated when the regenerative brake alone is used to decelerate the vehicle. Accordingly, the time at which the braking power exceeds the regenerative upper-limit electric power (e.g. a time indicated by a double-headed arrow in  FIG. 6  when the guidance distance is 43 meters) is counted up by the setting unit  51   c  as the upper limit time. Meanwhile, when the guidance distance is 75 meters, the braking power does not exceed the regenerative upper-limit electric power, and the regenerative electric power does not reach the regenerative upper-limit electric power. Therefore, the upper limit time is not counted up by the setting unit  51   c.    
     Returning to  FIG. 5 , at SA 12 , if the regenerative electric power specified by the regenerative electric power specification unit  51   a  has not reached the regenerative upper-limit electric power (SA 12 : No) or following the processing at SA 13 , the setting unit  51   c  determines whether acceleration of the vehicle is being performed (SA 14 ). Specifically, the setting unit  51   c  determines whether acceleration of the vehicle is being performed based on the accelerator operation amount as input from the ECU  10 . Alternatively, the setting unit  51   c  may determine whether acceleration of the vehicle is being performed based on the vehicle speed as input from the ECU  10 . 
     If acceleration of the vehicle is being performed (SA 14 : Yes), the acceleration operation is performed despite the fact that the guidance unit  51   b  output guidance encouraging deceleration of the vehicle. The setting unit  51   c  thus counts up a re-acceleration time that indicates a time that acceleration of the vehicle is performed after the guidance unit  51   b  performs guidance and before the vehicle passes the target feature (SA 15 ). The re-acceleration time is stored in the RAM, and the setting unit  51   c  adds to the re-acceleration time stored in the RAM an elapsed time since the previous determination at SA 14  until the current determination at SA 14 . 
     At SA 14 , if acceleration of the vehicle is not being performed (SA 14 : No) or following the processing at SA 15 , the setting unit  51   c  determines whether the re-acceleration time stored in the RAM is counted up to a value greater than zero and whether deceleration of the vehicle is being performed (SA 16 ). Specifically, the setting unit  51   c  determines whether deceleration of the vehicle is being performed based on the brake depression force as input from the ECU  10 . Alternatively, the setting unit  51   c  may determine whether deceleration of the vehicle is being performed based on the vehicle speed as input from the ECU  10 . 
     If the re-acceleration time stored in the RAM is counted up to a value greater than zero and deceleration of the vehicle is being performed (SA 16 : Yes), a brake operation was performed after acceleration of the vehicle, and the setting unit  51   c  turns on a re-deceleration flag (SA 17 ). The re-deceleration flag is a flag for specifying whether a brake operation is performed after the guidance unit  51   b  performs guidance and before the vehicle passes the target feature, and stored in the RAM (not shown). 
     At SA 16 , if the re-acceleration time stored in the RAM is zero or if deceleration of the vehicle is not being performed (SA 16 : No), or following the processing at SA 17 , the control unit  51  returns to SA 1 . 
     If there is no target feature ahead of the vehicle at SA 2  in  FIG. 4  (SA 2 : No) or the distance from the current position of the vehicle to the target feature at SA 6  is greater than the guidance distance set at SA 4  or SA 5  (SA 6 : No), the setting unit  51   c  executes a setting process (SA 18 ). After the setting process ends, the control unit  51  returns to SA 1 . 
     Processing: Setting Process 
     Here, the setting process will be described.  FIG. 7  is a flowchart of the setting process. 
     After the setting process is started, the setting unit  51   c  determines whether the setting start flag stored in the RAM is on (SB 1 ). If the setting start flag is not on (if the setting start flag is off) (SB 1 : No), a condition for starting to make a setting is not satisfied. Thus, the setting unit  51   c  ends the setting process and the processing returns to the main routine. 
     However, if the setting start flag is on (SB 1 : Yes), the setting unit  51   c  determines whether the re-deceleration flag stored in the RAM is on (SB 2 ). 
     If the re-deceleration flag is on (SB 2 : Yes), the setting unit  51   c  calculates a tentative set distance based on the guidance distance set at SA 4  or SA 5  in  FIG. 4  and the re-acceleration time stored in the RAM (SB 3 ). The tentative set distance is a tentative value for determining a set distance in the setting process. As shown in  FIG. 7 , for example, the setting unit  51   c  calculates as the tentative set distance a value that is found by subtracting the product of the re-acceleration time stored in the RAM and a tentative vehicle speed of 10/ms from the guidance distance set at SA 4  or SA 5  in  FIG. 4 . The tentative set distance thus calculated is proportional to the re-acceleration time and a shorter distance than the guidance distance. Therefore, by using this tentative set distance as the guidance distance, the new timing at which the guidance unit  51   b  performs guidance to encourage deceleration of the vehicle can be later than the previous guidance timing. 
     However, if the re-deceleration flag is not on (if the re-deceleration flag is off) (SB 2 : No), the setting unit  51   c  calculates the tentative set distance based on the guidance distance set at SA 4  or SA 5  in  FIG. 4  and the upper limit time stored in the RAM (SB 4 ). As shown in  FIG. 7 , for example, the setting unit  51   c  calculates as the tentative set distance a value that is found by adding the product of the upper limit time stored in the RAM and a tentative vehicle speed of 10/ms to the guidance distance set at SA 4  or SA 5  in  FIG. 4 . The tentative set distance thus calculated is proportional to the upper limit time and a longer distance than the guidance distance. Therefore, by using this tentative set distance as the guidance distance, the new timing at which the guidance unit  51   b  performs guidance to encourage deceleration of the vehicle can be earlier than the previous guidance timing. 
     Following the processing at SB 3  or SB 4 , the setting unit  51   c  determines whether the tentative set distance calculated at SB 3  or SB 4  is equal to or greater than 200 meters (SB 5 ). 
     If the tentative set distance calculated at SB 3  or SB 4  is equal to or greater than 200 meters (SB 5 : Yes), the setting unit  51   c  sets as the tentative set distance an approximate distance of 200 meters that the vehicle travels from a vehicle speed of 70 km/h to a stop at a deceleration of 0.1 G on a downhill road with a 5% grade (SB 6 ). 
     However, if the tentative set distance calculated at SB 3  or SB 4  is not equal to or greater than 200 meters (is less than 200 meters) (SB 5 : No), the setting unit  51   c  determines whether the tentative set distance calculated at SB 3  or SB 4  is equal to or less than 60 meters (SB 7 ). 
     If the tentative set distance calculated at SB 3  or SB 4  is equal to or less than 60 meters (SB 7 : Yes), the setting unit  51   c  sets as the tentative set distance an approximate distance of 60 meters that the vehicle travels from a vehicle speed of 40 km/h to a stop at a deceleration of 0.1 G on a downhill road with a 5% grade (SB 8 ). 
     Following the processing at SB 6  or SB 8 , or if the tentative set distance calculated at SB 3  or SB 4  is not equal to or less than 60 meters at SB 7  (SB 7 : No), the setting unit  51   c  sets the newest tentative set distance as the set distance (SB 9 ). The setting unit  51   c  also associates this set distance with the target feature ID of the target feature the vehicle last passed, and stores such associated information in the timing DB  52   b  as timing information. If the set distance set at SB 9  is larger than the smallest value and smaller than the largest value among the plurality of set distances stored corresponding to the table item “Set Distance” in the timing DB  52   b , and also smaller than the median value among the plurality of set distances, the setting unit  51   c  adds the set distance set at SB 9  to the timing DB  52   b  and deletes the largest value among the plurality of set distances stored in the timing DB  52   b . However, if the set distance set at SB 9  is larger than the smallest value and smaller than the largest value among the plurality of set distances stored corresponding to the table item “Set Distance” in the timing DB  52   b , and also larger than the median value among the plurality of set distances, the setting unit  51   c  adds the set distance set at SB 9  to the timing DB  52   b  and deletes the smallest value among the plurality of set distances stored in the timing DB  52   b . If the set distance set at SB 9  is equal to or smaller than the smallest value and equal to or larger than the largest value among the plurality of set distances stored corresponding to the table item “Set Distance” in the timing DB  52   b , the set distance set at SB 9  is an irregular value and the setting unit  51   c  does not add this set distance to the timing DB  52   b . Note that if the number of set distances stored in the timing DB  52   b  associated with the target feature ID of the target feature last passed by the vehicle is less than a predetermined number (nine in the example of  FIG. 3 ), the set distance set at SB 9  is added to the timing DB  52   b  without deleting a set distance stored in the timing DB  52   b.    
     Here, as an example, the target feature ID of the target feature last passed by the vehicle is “0101”. At SA 4  in  FIG. 4 , the guidance distance is set as the median value of 135 meters among the nine set distances corresponds to the target feature ID “0101” in the timing DB  52   b  of  FIG. 3 , and guidance is output by the guidance unit  51   b  at SA 9  and SA 10 . In this example, if 122 meters is calculated as the tentative set distance at SB 3  in  FIG. 7  and 122 meters is set as the set distance at SB 9 , the set distance of 122 meters is larger than the smallest value of 105 meters and smaller than the largest value of 148 meters among the plurality of set distances stored associated with the target feature ID “0101” in the timing DB  52   b  of  FIG. 3 . In addition, the set distance of 122 meters is smaller than the median value of 135 meters among the plurality of set distances. Therefore, the setting unit  51   c  adds the set distance of 122 meters to the set distances stored associated with the target feature ID “0101” in the timing DB  52   b  of  FIG. 3 , and deletes the largest value of 148 meters among the set distances stored associated with the target feature ID “0101” in the timing DB  52   b . Accordingly, the median value among the nine set distances corresponding to the target feature ID “0101” is changed from 135 meters to 124 meters. In other words, the set distance that the guidance unit  51   b  sets as the guidance distance at SA 4  in  FIG. 4  becomes shorter, and therefore, the new timing at which the guidance unit  51   b  performs guidance anew to encourage deceleration of the vehicle can be made later than the previous guidance timing. 
     Alternatively, if 138 meters is calculated as the tentative set distance at SB 4  in  FIG. 7  and 138 meters is set as the set distance at SB 9 , the set distance of 138 meters is larger than the smallest value of 105 meters and smaller than the largest value of 148 meters among the plurality of set distances stored associated with the target feature ID “0101” in the timing DB  52   b  of  FIG. 3 . In addition, the set distance of 138 meters is larger than the median value of 135 meters among the plurality of set distances. Therefore, the setting unit  51   c  adds the set distance of 138 meters to the set distances stored associated with the target feature ID “0101” in the timing DB  52   b  of  FIG. 3 , and deletes the smallest value of 105 meters among the set distances stored associated with the target feature ID “0101” in the timing DB  52   b . Accordingly, the median value among the nine set distances corresponding to the target feature ID “0101” is changed from 135 meters to 138 meters. In other words, the set distance that the guidance unit  51   b  sets as the guidance distance at SA 4  in  FIG. 4  becomes longer, and therefore, the new timing at which the guidance unit  51   b  performs guidance anew to encourage deceleration of the vehicle can be made earlier than the previous guidance timing. 
     In addition, if the target feature ID of the target feature last passed by the vehicle is “0101” and the set distance set at SB 9  is 98 meters, the set distance of 98 meters is smaller than the smallest value of 105 meters among the plurality of set distances stored associated with the target feature ID “0101” in the timing DB  52   b  of  FIG. 3 . Therefore, the setting unit  51   c  does not add the set distance of 98 meters to the timing DB  52   b.    
     Returning to  FIG. 7 , following the processing at SB 9 , the setting unit  51   c  clears the setting start flag, the re-deceleration flag, the upper limit time, and the re-acceleration time stored in the RAM (SB 10 ), and ends the setting process. The processing then returns to the main routine. 
     Effects 
     According to the first embodiment described above, based on the electric power regenerated by the regenerative brake in response to a brake operation performed after the guidance unit  51   b  performs guidance and before a target feature is passed, a new timing at which to perform guidance is set, and guidance is performed anew at the set timing. Therefore, guidance can be performed such that electric power regeneration is efficiently performed by the regenerative brake in consideration of the driving style of the driver. 
     The new timing at which to perform guidance is based on a brake operation performed after the guidance unit  51   b  performs guidance and before a target feature is passed. Therefore, guidance can be performed such that a suitable brake operation is performed in consideration of the driving style of the driver. 
     The setting unit  51   c  sets the new timing at which the guidance unit  51   b  performs guidance earlier if the electric power regenerated by the regenerative brake in response to the brake operation has reached the regenerative upper-limit electric power. Therefore, guidance can be performed at a new timing that allows the driver to perform a gentle brake operation without the regenerative electric power reaching the regenerative upper-limit electric power. Thus, guidance can be performed such that the regenerative brake efficiently regenerates electric power. 
     If a brake operation is performed following an acceleration operation after the guidance unit  51   b  performs guidance and before the vehicle passes the target feature, the setting unit  51   c  sets the new timing at which the guidance unit  51   b  performs guidance later. Therefore, guidance can be performed at a new timing at which the vehicle approaches the target feature without requiring that the driver accelerate the vehicle after guidance is performed by the guidance unit  51   b . Thus, unnecessary acceleration operations and brake operations can be suppressed. 
     The guidance unit  51   b  performs guidance at a median value among the plurality of timings that corresponds to the timing information stored in the timing DB  52   b . Therefore, guidance can be performed at the optimal timing in consideration of the driving style of the driver. 
     Second Embodiment 
     A second embodiment of the present invention will be explained here. In the second embodiment, a setting unit sets new timings at which to perform guidance for each of the target feature types, and guidance is performed at a new timing that corresponds to a target feature type among the new timings set by the setting unit. The configuration of the second embodiment is generally identical to the configuration of the first embodiment unless otherwise noted. For configurations generally identical to the configuration of the first embodiment, the same reference symbols and/or names as used in the first embodiment are assigned as necessary and accompanying explanations are omitted. 
     First, the constitution of the driving support system device  1  according to the second embodiment will be described. Note that, excluding the constitution of the control unit  51  of the driving support device  50  and the content of the timing DB  52   b , the constitution of the driving support system  1  according to the second embodiment is identical to that of the driving system  1  in the first embodiment. Therefore, the constitution of the driving support system  1  according to the second embodiment is not shown in a drawing. 
     Driving Support Device—Control Unit 
     The control unit  51  of the driving support device  50  according to the second embodiment includes a type specification unit in a constitution that is identical to that of the control unit  51  in the first embodiment. The type specification unit specifies a target feature type. The processes executed by the various portions of the control unit  51  that includes the type specification unit will be described in detail later. 
     Driving Support Device—Data Storage Unit 
     As described with reference to  FIG. 3  in the first embodiment, the timing DB  52   b  according to the second embodiment stores timing information that specifies a plurality of timings per target feature ID, and also stores timing information that specifies a plurality of timings per target feature type.  FIG. 8  is a table that illustrates information stored in the timing DB  52   b  according to the second embodiment. As shown in  FIG. 8 , similar to the table shown in  FIG. 3 , the timing DB  52   b  according to the second embodiment stores a feature table, which stores timing information that specifies a plurality of timings per target feature ID, and also stores a feature type table, which stores timing information that specifies a plurality of timings per target feature type. Information that corresponds to the table items “Target Feature Type” and “Set Distance” is mutually associated and stored in the feature type table. Information stored as corresponding to the table item “Target Feature Type” is type information that specifies a target feature type for which the setting unit  51   c  sets a guidance timing (“Stop” and so forth in  FIG. 8 ). 
     Processing: Driving Support Process 
     Next, a driving support process executed by the driving support system  1  of the second embodiment will be described. Note that, excluding the processing content at SA 3  and SA 4  in  FIG. 4 , the driving support process according to the second embodiment is identical to the driving support process in the first embodiment. Therefore, a flowchart of the driving support process according to the second embodiment is not provided. 
     At SA 2  in  FIG. 4 , if there is a target feature ahead of the vehicle (SA 2 : Yes), the guidance unit  51   b  determines whether the setting unit  51   c  has set a timing at which to perform guidance that encourages a brake operation for stopping or decelerating the vehicle before reaching the target feature (SA 3 ). At such time, the type specification unit specifies the type of a particular target feature ahead of the vehicle based on the feature data stored in the map information DB  52   a.    
     Here, similar to the first embodiment, if the target feature ID of a particular target feature ahead of the vehicle is stored in the feature table of the timing DB  52   b , the guidance unit  51   b  determines that the setting unit  51   c  has set a timing at which to perform guidance that encourages a brake operation for stopping or decelerating the vehicle before reaching the target feature. In addition, even though the target feature ID of a particular target feature ahead of the vehicle may not be stored in the feature table of the timing DB  52   b , if the type information that corresponds to that particular type of target feature is stored in the feature type table, the guidance unit  51   b  determines that the setting unit  51   c  has set a new timing at which to perform guidance that encourages a brake operation for stopping or decelerating the vehicle before reaching the target feature. 
     If the determination result at SA 3  is that the setting unit  51   c  has set a timing at which to perform guidance (SA 3 : Yes), based on the timing information stored in the timing DB  52   b  the guidance unit  51   b  sets a set distance as a guidance distance (SA 4 ). If the target feature ID of a particular target feature ahead of the vehicle is stored in the feature table of the timing DB  52   b , and if a predetermined quantity of timing information (nine in the example of  FIG. 8 ) is stored associated with that particular target feature ID, the guidance unit  51   b  sets a guidance distance such that guidance is performed at a median value among the plurality of timings that corresponds to the timing information stored in the feature table associated with the target feature ID, similar to the first embodiment. In other words, for example, if the target feature ID of a certain target feature ahead of the vehicle is “0101” according to the feature table of the timing DB  52   b  in  FIG. 8 , 135 meters is the median value among the corresponding nine set distances, and thus set as the guidance distance. 
     In addition, even though the target feature ID of a particular target feature ahead of the vehicle may not be stored in the feature table of the timing DB  52   b , if the type information that corresponds to that particular type of target feature is stored in the feature type table, and if a predetermined quantity of timing information (nine in the example of  FIG. 8 ) is stored associated with that particular type information, the guidance unit  51   b  sets a guidance distance such that guidance is performed at a median value among the plurality of timings that corresponds to the timing information stored in the feature type table associated with the target feature type. In other words, for example, if the type of a certain target feature ahead of the vehicle is “Stop” according to the feature type table of the timing DB  52   b  in  FIG. 8 , 137 meters is the median value among the corresponding nine set distances, and thus set as the guidance distance. 
     Processing: Setting Process 
     Next, the setting process of the second embodiment will be described. Note that, excluding the processing content at SB 9  in  FIG. 7 , the setting process according to the second embodiment is identical to the setting process in the first embodiment. Therefore, a flowchart of the setting process according to the second embodiment is not provided. 
     At SB 9  in  FIG. 7 , the setting unit  51   c  sets the newest tentative set distance as the set distance (SB 9 ). The setting unit  51   c  then associates the set distance with the target feature ID of the target feature last passed by the vehicle, and stores the set distance as timing information in the feature table of the timing DB  52   b . The setting unit  51   c  also associates the set distance with the type of the target feature last passed by the vehicle, and stores the set distance as timing information in the feature type table of the timing DB  52   b.    
     Effects 
     According to the second embodiment described above, the setting unit  51   c  sets a timing at which to perform guidance per the target feature type specified by the type specification unit. The guidance unit  51   b  performs guidance at a timing that corresponds to the target feature type specified by the type specification unit among the timings set by the setting unit  51   c . Therefore, guidance can be performed such that electric power regeneration is efficiently performed by the regenerative brake at a suitable timing in accordance with the target feature type and in consideration of the driving style of the driver. 
     Modifications of Embodiments 
     Embodiments of the present invention were explained above. However, the specific configuration and units for implementing the present invention may be modified and improved in any manner or form within the scope of the technical ideas of the present invention as set forth in the claims thereof. Examples of such modifications are explained below. 
     Problems to be Solved by the Invention and Effects of the Invention 
     The problems to be solved by the present invention and the effects of the present invention are not limited to the content described above and may vary depending on the environment in which the present invention is practiced and the detailed configuration thereof. The above problems may be only partially solved, and the above effects only partially achieved. 
     Timing Database 
     In the second embodiment described above, as an example, the feature type table of the timing DB  52   b  stores timing information per type, with target feature types including stops, left-right turn intersections, and railroad crossings. However, as another example, the speed limit range of the road on which the vehicle is traveling, number of lanes, road curvature, and road grade may be set as target feature types, and timing information may be stored associated with these types. Further, timing information may be stored per combinations of a plurality of types of target features. 
     Driving Support Process 
     In the embodiments described above, at SA 3  of the driving support process shown in  FIG. 4 , if it is determined that the timing at which to perform guidance has not been set by the setting unit  51   c  (SA 3 : No), the guidance unit  51   b  sets the predetermined initial value as the guidance distance (SA 5 ). However, as explained in the second embodiment, if a target feature type is specified by the type specification unit, the initial value may be changed depending on the specified type. 
     Further, in the embodiments described above, at SA 14  of the driving support process shown in  FIG. 5 , if it is determined that vehicle acceleration is being performed (SA 14 : Yes), the setting unit  51   c  counts up the re-acceleration time (SA 15 ). However, if an on-vehicle radar or the like discovers an obstacle in the vehicle surroundings (e.g. a stopped vehicle ahead or traffic work zone), the obstacle may be an external disturbance behind the vehicle acceleration. Thus, counting up of the re-acceleration time may not be performed in such case. At SA 16 , if the re-acceleration time stored in the RAM is counted up to a value greater than zero and it is determined that vehicle deceleration is being performed (SA 16 : Yes), the setting unit  51   c  turns on the re-deceleration flag (SA 17 ). However, if the on-vehicle radar or the like discovers an obstacle in the vehicle surroundings, the obstacle may be an external disturbance behind the vehicle brake operation. Thus, the re-deceleration flag may not be turned on in such case. 
     Setting Process 
     In the embodiments described above, at SB 2  of the setting process shown in  FIG. 7 , if it is determined that the re-deceleration flag is not turned on (SB 2 : No), the setting unit  51   c  calculates the tentative set distance based on the guidance distance set at SA 4  or SA 5  in  FIG. 4  and the upper limit time stored in the RAM (SB 4 ). However, if it is determined that the re-deceleration flag is not turned on (SB 2 : No), a determination may be made as to whether the upper limit time stored in the RAM is counted up to a value greater than zero. If the upper limit time is counted up to a value greater than zero, the tentative set distance may be calculated based on the guidance distance set at SA 4  or SA 5  and the upper limit time. In such case, the execution sequence of the process at SB 2  to determine whether the re-deceleration flag is turned on and the process to determine whether the upper limit time is counted up to a value greater than zero may be reversed. 
     In the embodiments described above, the set distance set at SB 9  of the setting process shown in  FIG. 7  is stored in the timing DB  52   b  as timing information. However, if the timing information that corresponds to the target feature ID of the target feature passed by the vehicle is not stored in the timing DB  52   b  (that is, if this is the first time the vehicle has passed the target feature), a predetermined quantity of the set distance set at SB 9  (nine in the example of  FIG. 3 ) may be stored in the timing DB  52   b.    
     In the embodiments described above, as an example, a timing at which to perform guidance is set based on a brake operation performed after the guidance unit  51   b  performs guidance and before a target feature is passed, and electric power regenerated by the regenerative brake in response to the brake operation. However, the timing at which to perform guidance may be set based on only the electric power regenerated by the regenerative brake.