Patent Publication Number: US-2021179088-A1

Title: Parking assistance device, parking assistance method, and computer program product

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2019-225910 filed Dec. 13, 2019, the entire contents of which are incorporated herein by reference. 
     BACKGROUND 
     Technical field 
     The disclosure relates to a parking assistance device, parking assistance method and computer program product. 
     Related Art 
     Patent Literature 1 (Japanese Unexamined Patent Application Publication No. 2018-83480) discloses a technology for setting an automatic parking location of a host vehicle within a parking region of a parking area when the parking area has parking regions for individual vehicles separated by boundary lines. According to the disclosed technology, the parking location within the parking region is set based upon positions of neighboring vehicles and is offset either to the left or right depending on these positions. 
     Patent Literature 2 (Japanese Unexamined Patent Application Publication No. 2017-213943) discloses a technology for recognizing a parking location in a parking area where parking regions for individual vehicles are not separated by boundary lines. According to the disclosed technology, the parking location is recognized based on a first corner location and second corner location of a parking region, wherein the first corner location is a near-side corner location of a vehicle entry part of the parking region and the second corner location is a rear-side corner location of the vehicle entry part that are based on an image taken by an on-board camera. 
     In the case where a parking area does not have a boundary line separating parking regions in which individual vehicles park, when a parking region is available for a host vehicle to park in and that parking region has a lot of space, by selecting a parking location of the host vehicle without taking into consideration a possibility that the parking region would be used by another vehicle after the host vehicle is parked, efficient utilization of space by individual vehicles within the parking area will be jeopardized. Furthermore, by parking the host vehicle in such a parking region with no consideration regarding efficient use of space, there is likelihood that the host vehicle would be left with unsatisfactory spaces on both its sides once an adjacently parked vehicle has left. 
     SUMMARY 
     One aspect of the disclosure provides a parking assistance device including a recognition part configured to acquire recognition information through recognition of surroundings of a host vehicle, a parking region determiner configured to determine a space between other vehicles as a parking region of the host vehicle based on the recognition information, an automatic parking controller configured to perform a parking operation to park the host vehicle in the parking region, and a parking location determiner, wherein in response to determining that an entry width of the parking region is less than a predetermined value, the parking location determiner is configured to determine a parking location of the host vehicle in the parking region that is at a central location as viewed from an entry side of the parking region, and in response to determining that the entry width is equal to or greater than the predetermined value, the parking location determiner is configured to determine the parking location that is closer to one of the other vehicles as viewed from the entry side of the parking region. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a block diagram of a system configuration in accordance with at least one embodiment centered on an automatic parking control unit according to at least one embodiment. 
         FIG. 2  is a top view of a vehicle installed with an automatic parking control unit according to at least one embodiment showing the positions of cameras and sonars installed on the vehicle. 
         FIG. 3A  is a top view of a parking area for explaining a situation where a vehicle installed with an automatic parking control unit according to at least one embodiment searches for a space to perform a parking maneuver. 
         FIG. 3B  is a top view of a parking area for explaining a situation where a vehicle installed with an automatic parking control unit according to at least one embodiment searches for a space to perform a parking maneuver. 
         FIG. 3C  is a top view of a parking area for explaining a situation where a vehicle installed with an automatic parking control unit according to at least one embodiment searches for a space to perform a parking maneuver. 
         FIG. 4  is a flowchart for explaining a process executed by an automatic parking control unit according to at least one embodiment. 
         FIGS. 5A and 5B  are flowcharts for explaining parts of a process executed by an automatic parking control unit according to at least one embodiment. 
         FIG. 6  is a top view of a parking area for explaining a process executed by an automatic parking control unit according to at least one embodiment. 
         FIG. 7  is a top view of a parking area for explaining a process executed by an automatic parking control unit according to at least one embodiment. 
         FIG. 8  is a top view of a parking area for explaining a process executed by an automatic parking control unit according to an embodiment. 
         FIG. 9  is a top view of a parking area for explaining a process executed by an automatic parking control unit according to at least one embodiment. 
         FIG. 10  is a plan view of a selection screen that is displayed on a touch panel by a process that is executed by an automatic parking control unit according to at least one embodiment. 
         FIG. 11  is a flowchart of a subroutine for a parking location determination process of  56  that is executed by an automatic parking control unit according to at least one embodiment. 
         FIG. 12  is a plan view of a parking area for explaining a parking location determination process of S 6  that is executed by an automatic parking control unit according to at least one embodiment. 
         FIG. 13  is a plan view of a parking area for explaining a parking location determination process of S 6  that is executed by an automatic parking control unit according to at least one embodiment. 
         FIG. 14  is a plan view of a parking area for explaining a parking location determination process of S 6  that is executed by an automatic parking control unit according to at least one embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     An object of the disclosure is to provide a parking assistance device that parks a vehicle at a parking location that allows an efficient use of space in a parking area. 
     One aspect of the disclosure provides a parking assistance device that is able to park a vehicle at a parking location that allows an efficient use of space in a parking area. 
     In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. It will be apparent, however, that one or more embodiments may be practiced without these specific details. In other instances, well-known structures and devices are schematically shown in order to simplify the drawing. 
     Embodiments according to the disclosure is described below with reference to drawings. Directions to the front, back, left, and right referred to in the description are in accordance with the arrows shown in the drawings. 
       FIG. 1  is a block diagram showing a system configuration of an embodiment centered on an automatic parking control unit  1 .  FIG. 2  is a top view of a host vehicle  100  equipped with the system of  FIG. 1 . 
     The automatic parking control unit  1  is an electronic control unit (ECU) for automatic parking that is installed on board the host vehicle  100 . The automatic parking control unit  1  is an embodiment of a parking assistance device of the disclosure and is configured mainly from a microcomputer and realizes the functions of the following various control parts through executing a process based on a control program, The automatic parking control unit  1  operates based on a program characteristic to the disclosure and carries out a parking assistance method of the disclosure through this operation. A recognition part  11  acquires recognition information including image data and sonar data by recognizing the surroundings with a camera group  21  and sonar group  22  (the camera group  21  and sonar group  22  are described later). Based on this recognition information, a parking region determiner  12  determines a space between other vehicles as a parking region of the host vehicle  100 . A “parking region” refers to a space within a parking area where the host vehicle  100  may be parked with appropriate spacing with an obstacle or another vehicle. Here, a parking area includes ones where parking spaces (parking regions) in which individual vehicles park are not separated, for example, with a boundary line such as a white line (in other words, a parking area with undefined parking spaces). An automatic parking controller  13  carries out control of a parking operation of the host vehicle  100  into a parking region. 
     A parking location determiner  14  determines a parking location of the host vehicle  100  in a parking region. When a width of the parking region on a side from which the host vehicle  100  enters the parking region (hereinafter an “entry width”) is less than a predetermined value, the parking location determiner  14  sets the parking location to a center of the parking region as viewed from an entry side thereof. A “parking location” is a specific location in a parking region where the host vehicle  100  is to be parked. When, on the other hand, the entry width is equal to or greater than the predetermined value, the parking location determiner  14  sets the parking location to a location that is closer to one of the other vehicles as viewed from the entry side of the parking region. 
     In some embodiments, when the parking location determiner  14  sets the parking location of the host vehicle  100  to a location that is closer to one of the other vehicles as viewed from the entry side of the parking region, that location is set so that there is a predetermined space with the other vehicle on which side the parking location is closer to. 
     In some embodiments, when the parking location of the host vehicle  100  is set to a location that is closer to one of the other vehicles as viewed from the entry side of the parking region, the parking location determiner  14  sets a “shift distance”, a distance by which the parking location is shifted to be closer to the one of the other vehicles, to a predetermined distance. This shift distance is a distance from a line extending from a central point of the parking region as viewed from the entry side thereof to the rear side of the parking region. 
     In some embodiments, the parking location determiner  14  sets reference points of the entry width of the parking region to corners of the other vehicles. 
     In some embodiments, to which of the other vehicles the parking location is to be closer to is decided by the parking location determiner  14  based on the position of the host vehicle  100 . 
     In some embodiments, the parking location determiner  14  may decide on which of the other vehicles the parking location is to be closer to by prioritizing a ground surface condition of a parking area where the host vehicle  100  performs the parking operation (ground surface condition precedence). 
     In some embodiments, the parking location determiner  14  may decide on which of the other vehicles the parking location is to be closer to by prioritizing a type of each of the other vehicles (other vehicles types precedence). 
     The automatic parking control unit  1  is connected to a camera group  21  and sonar group  22 . Note that each component that is connected to the automatic parking control unit  1  (with the connection as indicated by a line in the drawing of  FIG. 1 ) may have a wire connection with the automatic parking control unit  1  or may have a connection via a Controller Area Network (a CAN). 
     The camera group  21  is a group of cameras that the host vehicle  100  is installed with as shown in  FIG. 2 . The host vehicle  100  is equipped at the front thereof with a front camera  21 F that captures an image of a view in front of the host vehicle  100 . Furthermore, the host vehicle  100  is equipped at the rear thereof with a rear camera  21 R that captures an image of a view at the back of the host vehicle  100 . Yet further, the host vehicle  100  is equipped on the right side thereof towards the front with a side camera  21 RF that captures an image of a view to the right of the host vehicle  100 . Yet further, the host vehicle  100  is equipped on the left side thereof towards the front with a side camera  21 LF that captures an image of a view to the left of the host vehicle  100 . The side cameras  21 RF and  21 LF may each be installed on the tip of a side mirror or away from a side mirror to prevent the side mirrors from obstructing the views that are captured by the cameras. The side cameras  21 RF and  21 LF may each be installed somewhere at some distance away from a side mirror. 
     The sonar group  22  is a group of cameras that the host vehicle  100  is installed with as shown in  FIG. 2 . The host vehicle  100  is equipped at the front thereof with four front sonars  22 F that are arranged apart at substantially equal intervals. The four front sonars  22 F detect an obstacle in front of the host vehicle  100 . Furthermore, the host vehicle  100  is equipped at the rear thereof with four rear sonars  22 R that are arranged apart at substantially equal intervals. The four rear sonars  22 R detect an obstacle at the back of the host vehicle  100 . The front sonars  22 F detect an obstacle in the direction of travel when the host vehicle  100  is moving forward. The rear sonars  22 R detect an obstacle in the direction of travel when the host vehicle  100  is moving in reverse. 
     Furthermore, the host vehicle  100  is equipped with a single side sonar  22 RF on a front portion of the right side of the host vehicle  100 . The side sonar  22 RF detects an obstacle at the front right of the host vehicle  100  to the right of the host vehicle  100 . Yet further, the host vehicle  100  is equipped with a single side sonar  22 LF on a front portion of the left side of the host vehicle  100 . The side sonar  22 LF detects an obstacle at the front left of the host vehicle  100  to the left of the host vehicle  100 . Yet further, the host vehicle  100  is equipped with a single side sonar  22 RR on a back portion of the right side of the host vehicle  100 . The side sonar  22 RR detects an obstacle at the back right of the host vehicle  100  to the right of the host vehicle  100 . Yet further, the host vehicle  100  is equipped with a single side sonar  22 LR on a back portion of the left side of the host vehicle  100 . The side sonar  22 LR detects an obstacle at the back left of the host vehicle  100  to the left of the host vehicle  100 . Each of the side sonars  22 RF,  22 LF,  22 RR, and  22  LR detects an obstacle that may be in the path of the host vehicle  100 . In  FIG. 2 , a broken line S indicates a spatial range where the individual sonars detect an obstacle. The broken line V indicates a range of view of individual cameras. 
     Note that the number of cameras and sonars and their installed locations are not limited to the description given above. The number of cameras and sonars may be increased or decreased. The locations of the cameras and sonars may be changed. In some embodiments, the numbers and locations of one or more cameras and one or more sonars are selected so that the situation around the circumference of the host vehicle  100  is detectable. 
     Furthermore, a sensor other than a camera or a sonar may be used to detect the surrounding situation of the host vehicle  100 . For example, the host vehicle  100  may be equipped with a radar. The radar includes a function to acquire distribution information of a target by irradiating a target with a radar wave and receiving a radar wave reflected from the target, the target including another vehicle driving in front of the host vehicle  100 , and the distribution information of the target including a distance to the target and a direction of the target. For the radar wave, a laser, a microwave, a millimeter-wave, or an ultrasonic wave may for example be used as deemed appropriate. 
     Furthermore, the host vehicle  100  may be equipped with a LIDAR (Light Detection and Ranging). The LIDAR includes, for example, a function to detect a presence of a target and a distance to the target by measuring the time taken to detect scattered light in response to irradiation of light. 
     In the description that follows, an example is used where the host vehicle  100  detects its surrounding area through a combined used of the camera group  21  and sonar group  22 . 
     Referring back to  FIG. 1 , the automatic parking control unit  1  is connected to an inertial sensor  23  and a wheel speed sensor  24 . The inertial sensor  23  is a sensor that detects the acceleration of the host vehicle  100 . The wheel speed sensor  24  is a sensor that detects the wheel speed of each of the wheels of the host vehicle  100 . 
     Furthermore, the automatic parking control unit  1  is connected to an information input and output device  31 . The information input and output device  31  includes a touch panel  32  and a speaker  33 . The main body of the information input and output device  31  is arranged in the vicinity of a drivers seat to allow the driver to operate, for example, the touch panel  32 . The information input and output device  31  may display various information on the touch panel  32 , output various audio output with the speaker  33 , and accept various operations through the touch panel  32 . 
     In other words, through the use of the information input and output device  31 , car navigation information that has been prepared, for example, based on information from a satellite navigation system, may be displayed on the touch panel  32  or output as audio from the speaker  33  or both. This car navigation information may also include information received from the Vehicle Information and Communication System (VICS [a registered trademark]). 
     Furthermore, the information input and output device  31  may receive TV and radio broadcast and display images on the touch panel  32  and output audio from the speaker  33 . Yet further, the information input and output device  31  may include an optical disc drive (not shown) and read data from media such as a CD (a compact disc), DVD (a digital versatile disc or digital video disc), and BD (a Blu-ray Disc). Yet further, the information input and output device  31  may include an HOD (a hard disk drive, not shown) and play music recorded thereon. 
     Yet further, the information input and output device  31  may be used to output various messages from the host vehicle  100  or a device installed on the host vehicle  100  (e.g., an ETC [Electronic Toll Collection] in-vehicle device) and accept various operations for the installed device. 
     The automatic parking control unit  1  is connected to a brake system  41 , The brake system  41  is a system for performing the braking of the host vehicle  100 . The brake system  41  includes a brake device  42  that performs the braking of the host vehicle  100  and a brake controller  43  that controls the brake device  42 . The brake controller  43  includes a function of an automatic brake hold controller  44 . The automatic brake hold controller  44  realizes an automatic brake hold control part. The brake device  42  generates hydraulic pressure (oil pressure) thereby supplying hydraulic pressure to a wheel cylinder of each wheel to generate friction braking force. Note that the brake system  41  may use a regenerative brake in conjunction when the host vehicle  100  is, for example, a hybrid vehicle. The brake device  42  is, for example, a device where a brake-by-wire system is applied. Therefore, the brake device  42  may generate braking force irrespective of a brake pedal operation (a brake pedal is not shown in drawings). Furthermore, the brake device  42  may be a system installed with an electric brake booster. In this case, braking force may be generated with the electric brake booster irrespective of a brake pedal operation. The brake controller  43  is a controller for controlling the brake device  42 . 
     The automatic brake hold controller  44  is a function that is included as part of the brake controller  43  and controls an automatic brake hold function, The automatic brake hold function is a function for maintaining a braking state of the host vehicle  100  when the driver releases his foot from a brake pedal (not shown) after the brake pedal has been pressed. Note that with the automatic brake hold function, the host vehicle  100  is released from the automatic brake hold state when a predetermined condition is met, such as when an accelerator pedal (not shown) is operated. The automatic brake hold state may be turned on and off by operating a brake hold switch  45  installed close to the driver&#39;s seat of the host vehicle  100 . 
     The automatic parking control unit  1  is connected to a drive system  51 . The drive system  51  is a system to drive the host vehicle  100 . In the given example, the host vehicle  100  is a hybrid vehicle that includes as its driving source an engine  52  and a motor generator  53 . A hybrid controller  54  drives the host vehicle  100  by controlling the engine  52  and motor generator  53 . Note that the host vehicle  100  is not limited to a hybrid vehicle. When, for example, the host vehicle  100  is a gasoline-powered vehicle, the engine  52  is the driving source. When, as another example, the host vehicle  100  is an electric vehicle including a fuel-cell vehicle, a motor is the driving source. 
     A transmission system  61  is a system for carrying out, gear changes of the host vehicle  100 . The transmission system  61  includes a transmission  62  that performs a gear change of the host vehicle  100 , a transmission controller  63  that controls the transmission  62 , and a gearshift  64  that is connected to the transmission  62 . The transmission  62  may be an automatic transmission or a manual transmission, With the transmission system  61  described here, a gear change may be carried out without driver operation and through the transmission controller  63  controlling the transmission  62 , in which case the transmission controller  63  moves the position of the gearshift  64  in accordance with the gear change. 
     The automatic parking control unit  1  is connected to a driver presence determiner  65 . The driver presence determiner  65  determines whether a driver is present in the driver&#39;s seat. 
     The automatic parking control unit  1  is connected o an electric power steering system  71  (an EPS system  71 ). The EPS system  71  is a system configured to assist the steering of the driver. The EPS system  71  includes a steering axle  73  with a steering wheel  72 , a drive motor  74  that drives the rotation of the steering axle  73 , and an EPS controller  75  that controls the drive motor  74 . The EPS system  71  rotates the steering axle  73  using the drive motor  74  as a driving source thereby assisting the steering operation of the driver turning the steering wheel  72 . 
     Next, the effect of the system centered on the automatic parking control unit  1  is described. 
     In the subsequent description, the phrase “automatic parking operation” refers to a series of operations described in the flowcharts of  FIGS. 4 and 5  (described later) that involves the automatic parking control unit  1  performing automatic operation of the host vehicle  100  through the control of individual systems and driving the host vehicle  100  to perform automatic parking. The phrase “automatic parking function” refers to the entire process indicated by the flowcharts of  FIGS. 4 and 5  concerning automatic parking that the automatic parking control unit  1  takes a central role executing (note that the entire process includes the “automatic parking operation”). 
     The automatic parking control unit  1  carries out the control of automatic parking. To do this, the automatic parking control unit  1  detects a space to perform a parking maneuver in a place such as a parking area by using the camera group  21  and sonar group  22 .  FIGS. 3A-3C  are top views of the host vehicle  100  for explaining a situation where the host vehicle  100  searches for a space to perform a parking maneuver. 
       FIG. 3A  is a top view showing a situation where the host vehicle  100  searches for a space to carry out a parking maneuver in a parking area  200  through the use mainly of the front camera  21 F of the camera group  21 . To the host vehicle  100  that has entered the parking area  200 , there are multiple parking spaces  202  (parking regions) separated by white lines  201  (boundary lines) that are arranged on the left and right. Some parking spaces  202  are already in use by other vehicles  203  but some are vacant. A driver of the host vehicle  100  drives the host vehicle  100  to advance slowly along a passage  210  of the parking area  200  in a direction of travel  208 . Although the parking area  200  of the drawing shows parking spaces  202  on both sides of the passage  210 , there are cases where parking spaces  202  are available on one side and not on the other. 
     From an image captured by the front camera  21 F (Ha  2 ), a region  211  may be recognized as a space that is available for the host vehicle  100  to perform a parking maneuver. By performing predetermined image processing on the image captured by the front camera  21 F, a difference in luminance levels may be recognized, and in this way, the host vehicle  100  may recognize the region  211  that is available for use to perform a parking maneuver. Camera recognition is good at recognizing a white line  201 . Camera recognition also includes a space recognition function. However, camera recognition is not good at recognizing objects such as snow, a white wall, and another vehicle close by. For this reason, control of the brake to avoid colliding with obstacles when performing automatic parking is difficult with only the image captured by the front camera  21 . 
     The sonar group  22  is therefore used in combination.  FIG. 3B  is a top view showing a situation where all the sonars of the sonar group  22  are used to search for a space to perform a parking maneuver in the parking area  200 . Sonars are capable of detecting an obstacle by transmitting and receiving sound waves and, in comparison to a camera, is good at detecting an obstacle close by. Therefore, a sonar may be used to accurately perform brake control against an obstacle. Furthermore, because a sonar has a higher space recognition function than a camera, the sonar group  22  is useful when deriving various parking patterns.  FIG. 3B  shows a region  261  that is available for use when performing a parking maneuver as recognized by the sonar group  22 . 
     FIG,  3 C is a top view showing both the region  211  and region  261 . Through the combined use of the front camera  21 F and sonar group  22 , a wide space may be recognized as a space available for use to perform a parking maneuver. Furthermore, the combined use enables a better brake control for avoiding an obstacle. In the example of  FIG. 3C , a parking space  202   a  is decided as a parking region in which the host vehicle  100  is to park through automatic parking. A space further down on the right as viewed from the host vehicle  100  is unoccupied and this location is decided as a location (“a change-to-reverse location”) where the host vehicle  100  stops before moving in reverse. The example shows how the host vehicle  100  may be parked through automated parking by (a) moving and steering the host vehicle  100  forward to the right (as shown by an arrow  263 ), (b) stopping the host vehicle  100  temporarily at the change-to-reverse location  262 , and (c) turning back the steering wheel and moving the host vehicle  100  in reverse so that the host vehicle  100  enters the parking space  202   a  (a parking region) (as shown by an arrow  264 ). 
     The above has been an outline of automated parking in which the front camera  21 F is used in combination with the sonar group  22 . A detailed description of a process of automated parking now follows. 
       FIGS. 4, 5A, and 5B  are flowcharts that explain a process carried out by the automatic parking control unit  1 .  FIGS. 6-9  are top views of a parking area for describing the process that the automatic parking control unit  1  carries out. Note that the flowcharts illustrate an outline of a series of operational steps described below and does not include every detail of the operational steps that the automatic parking control unit  1  perform. Operations not included in the flowcharts are included in the below description as deemed appropriate. 
     To begin with, as shown in  FIG. 6 , a driver of the host vehicle  100  drives the host vehicle  100  into a parking area  200  as shown by an arrow indicating a direction of travel  208 . During this time, the driver instructs the automatic parking function to be activated by, for example, operating the touch panel  32  (“Yes” of S 1 ). The instruction to activate the automatic parking function is received by the automatic parking controller  13 . Upon receiving the instruction, the automatic parking controller  13  displays a predetermined screen for the automatic parking function on the touch panel  32  (S 2 ). Note that during the series of operational steps, various types of automatic parking function screens are displayed as deemed appropriate. 
     The recognition part  11  makes a combined use of the front camera  21 F and the sonar group  22  with a method such as that described above with reference to  FIGS. 3A-3C . The recognition information acquired by the recognition part  11  is used by the parking region determiner  12  to search for a parking maneuver space that the host vehicle  100  is able to use when performing a parking maneuver (S 3 ). 
     Furthermore in S 3 , based on the result of the search, the following operations are carried out. First, the parking region determiner  12  determines a parking region (a parking space  202 ) where the host vehicle  100  is possible to park. In the example of  FIG. 7 , parking spaces  202   a  and  202   b  are candidates for a parking-target parking region. Furthermore, based on the detection results of the front camera  21 F and sonar group  22 , the automatic parking controller  13  calculates paths that avoid an obstacle for the host vehicle  100  to park in the parking space  202   a  and in the parking space  202   b.    
     Next, the automatic parking controller  13  estimates the current location of the host vehicle  100  based on the detection results of the inertial sensor  23  and wheel speed sensor  24 , Using this location as reference, the automatic parking controller  13  calculates each of the target movement paths of the host vehicle  100  to park in the parking space  202   a  and in the parking space  202   b.  The automatic parking controller  13  provides a display on the touch panel  32  of relative locations of the host vehicle  100  and the parking spaces  202   a  and  202   b  such as that shown in  FIG. 7 . For ease of recognition by the driver, the parking spaces  202   a  and  202   b  are indicated on a displayed image with a mark such as a frame  205 . 
     Since the “Yes” of S 1 , the driver has been driving the host vehicle  100  to move through the parking area  200 , and during this time the operations of S 3  continue to be performed (“No” of S 4 ). However, when the brake pedal (not shown) is operated by the driver (“Yes” of S 4 ) and the host vehicle  100  stops, the parking region determiner  12  performs the following operations. When the driver operates the touch panel  32  and selects one candidate (in this example, the parking space  202   a  or  202   b ) as the parking-target parking region (“Yes” of S 5 ), the parking region determiner  12  determines that the selected candidate is the parking-target parking region. The selection may, for example, be carried out by touching a region indicated by a frame  205  mentioned above. When the selection is not made (“No” of S 5 ), the abovementioned operations of  53  are continued. Note that the operational steps of S 4  and S 5  may be reversed in order. 
     When the parking-target parking region is determined as above (“Yes” of S 5 ), the parking region determiner  12  displays a mark  271 , such as the one shown in  FIG. 8 , on an image of the parking region (in this example, the parking space  202   a ) displayed on the touch panel  32 . 
     The automatic parking controller  13  instructs the automatic brake hold controller  44  to turn on the automatic brake hold function (S 6 ). As a result of turning on the automatic brake hold function, the brake state of the host vehicle  100  is automatically maintained when a foot of the driver is removed from the brake pedal (not shown). 
     Furthermore, a travel route indicated by arrows  263  and  264  in  FIG. 3C  and a change-to-reverse location indicated by the number “ 262 ” also in  FIG. 3C  are determined by the parking location determiner  14 . When the travel route and change-to-reverse location are determined, a parking location within the parking-target parking region that was selected in S 5  is determined (S 6 ). The determination process of the parking location is described later. 
     Subsequently, the automatic parking controller  13  starts measuring an elapsed time, a first length of time, with a timer (S 7 ). Then, the automatic parking controller  13  displays a message on automatic parking on the touch panel  32  and outputs an audio message with the speaker  33  (S 8 ). In some embodiments, the message on automatic parking is output on the touch panel  32  only. The message notified to the driver contains information to the following effect: “The automatic brake hold has been turned on. To begin automatic parking, press the brake hold switch, release your hands from the steering wheel, and remove your foot from the brake pedal”. 
     If the driver follows all the instructions given in the message, the brake hold switch  45  will be pressed thereby releasing the brake hold switch  45  (i.e., the brake hold switch  45  will be released from a “pressed” state: “Yes” of S 9 ). When the brake hold switch  45  is not released (“No” of S 9 ), the abovementioned message continues to be displayed on the touch panel  32 . 
     Note that when a predetermined operation is performed during the operational steps S 2 -S 8  that have been described, the series of operational steps for automatic parking is terminated. This may occur, for example, when the driver operates the automatic parking function screen displayed on the touch panel  32  to terminate the operation of the automatic parking function, or when the driver intentionally operates the gearshift  64 . 
     When the brake hold switch  45  is released (“Yes” of S 9 ), the operations of S 10  are carried out. That is, the automatic parking controller  13  instructs the automatic brake hold controller  44  to turn off the automatic brake hold function (S 10 ). This causes the brake on the host vehicle  100  to be released. Furthermore, the automatic parking controller  13  stores a record of operation of the automatic brake hold function in  86  in storage such as a non-volatile memory (S 10 ). Yet further, the automatic parking controller  13  starts the automatic parking operation ( 810 ). (Details of the automatic parking operation is described later.) Yet further, the automatic parking controller  13  starts measuring another elapsed time, a second length of time, with a timer ( 810 ). Note that when the brake pedal (not shown) is not released, the automatic parking controller  13  performs control as follows. Even when the brake hold switch  45  is released ( 59 ), the automatic parking controller  13  does not start the automatic parking operation (S 10 ). The automatic brake hold function (S 6 ) remains turned on. 
     The automatic parking operation started by the automatic parking controller  13  includes the following operations. As shown in  FIG. 9 , the automatic parking controller  13  controls the host vehicle  100  to travel along the target movement path that has been decided in  53 . That is, the automatic parking controller  13  controls the brake system  41 , drive system  51 , transmission system  61 , and EPS system  71 , Through this control, the host vehicle  100  reverse parks in the parking space  202   a,  the parking-target parking region. 
     Described in more detail, the automatic parking controller  13  controls these systems so that the host vehicle  100  travels forward in D range as shown by the arrow  263  until the change-to-reverse location  262  is reached, at which point the host vehicle  100  stops temporarily. Next, the automatic parking controller  13  controls these systems so that the host vehicle  100  (i) travels backwards in R range and into the parking space  202   a,  the parking-target parking region, and (ii) stops when the host vehicle  100  has entered the parking space  202   a.    
     Once the automatic parking operation has been started (S 10 ), the automatic parking controller  13  judges whether a condition to suspend the automatic parking function is met while the automatic parking operation is taking place (S 11 ). 
     In S 11 , an operation of the steering wheel  72  is one action that meets the condition to suspend the automatic parking function and a shifting of the gearshift  64  to the N range is another action that meets the condition to suspend the automatic parking function. 
     Furthermore, in S 11 , the automatic parking controller  13  determines whether the first length of time, whose measurement started in S 7 , has reached a predetermined length of time. The first length of time is a period of time from when the parking-target parking region is decided (S 5 , S 7 ) to when the operation to remove the automatic brake hold with the brake hold switch  45  is received (“Yes” of S 9 ), The condition to suspend the automatic parking function is also met if the first length of time is equal to or greater than the predetermined length of time. Yet further, in S 11 , the automatic parking controller  13  determines whether the second length of time whose measurement started in S 10  has reached a predetermined length of time. The second length of time is a period of time from when the brake hold switch  45  is operated (“Yes” of S 9 ) to when a released state of the brake pedal (not shown) is detected. The condition to suspend the automatic parking function is also met if the second length of time is equal to or greater than the predetermined length of time. 
     Furthermore, the condition to suspend the automatic parking function is also met if, through the driver presence determiner  65 , it is determined that a driver seat is without a driver. The driver presence determiner  65  may be configured from a device such as a seating sensor that detects whether a driver is seated in the driver&#39;s seat, an on-board camera that takes an image of the vehicle interior (the presence of a seated driver may be determined through image processing), or a door-opening sensor that detects whether the door next to the driver&#39;s seat is opened or closed. Yet further, various other conditions under which suspending the automatic parking function is considered sensible may be used as a criterion to meet the condition to suspend the automatic parking function. 
     When the automatic parking operation is completed with the condition to suspend the automatic parking function not being met (“Yes” of S 12 ), the automatic parking controller  13  outputs a message to notify the completion of the automatic parking operation. The message may be output through the touch panel  32 , speaker  33 , or the like. The next operational step becomes S 13 . If the condition to suspend the automatic parking function has been met during the automatic parking operation (“No” of S 12 ), the next operational step becomes S 16 .The automatic parking operation is complete (“Yes” of S 12 ) when the host vehicle  100  comes to a stop inside the parking-target parking region (in this example, the parking space  202   a ). The location within the parking region that is selected as the parking location of the host vehicle  100  is based on the decision made in S 6  (to be described later). 
     In S 13 , the automatic parking controller  13  determines whether a record of an automatic brake hold operation has been stored in S 10 . If there is a stored record of an automatic brake hold operation (“Yes” of S 13 ), the brake system  41  is controlled to turn on the automatic brake hold function once again. The operational step then advances to S 15 . Therefore, even if the driver is not pressing down on the brake pedal (not shown), the host vehicle  100  is applied with a brake and stops. If there is no stored record (“No” of S 13 ), the process advances to S 15 . In this case, the automatic brake hold function stays turned off. An example of when a record of an automatic brake hold operation is not stored is when, even though the automatic brake hold function is turned on in S 6 , the driver operates the brake hold switch  45  to turn off the function. In S 15 , the automatic parking controller  13  controls the gearshift  64  so that gearshift position shifts to the P range to end the automatic parking. 
     In S 16 , on the other hand, because the condition to suspend the automatic parking function has been met (“Yes” of S 11 ), the automatic parking controller  13  suspends the automatic parking function. Then, the automatic parking controller  13  determines whether a condition to resume the automatic parking function exists (S 17 ) A condition to resume exists if a predetermined criterion is met, The predetermined criterion may be met if a predetermined operation is carried out on a selection screen  81  of  FIG. 10 , the selection screen  81  being one type of automatic parking function screens that are displayed on the touch panel  32 . The selection screen  81  displays a “Resume” button  82  and “Terminate” button  83 . If the driver operates the “Resume” button  82 , the predetermined criterion is met and the condition to resume the automatic parking function exists. If the “Terminate” button  83  is operated, then a termination of the automatic parking function is selected. 
     If the condition to resume the automatic parking function exists (“Yes” of S 17 ), the process returns to S 2  and the automatic parking function resumes. If a predetermined amount of time elapses without the condition to resume the automatic parking function arising (“No” of S 17  and “Yes” of S 18 ), the automatic parking controller  13  makes a decision to terminate the automatic parking function (S 19 ), and the series of operational steps comes to an end. If the predetermined amount of time has not yet elapsed and the condition to resume the automatic parking function has not arisen (“No” of S 17  and “No” of S 18 ), the automatic parking controller  13  returns to S 16 . Note that if the “Terminate” button  83  is operated, the automatic parking controller  13  may terminate the automatic parking function without waiting for the predetermined amount of time referred to in S 18  to elapse. 
     Note that when the condition to suspend the automatic parking function exists (“Yes” of S 11 ), the automatic parking controller  13  may resume the automatic parking function from S 2  if the condition to resume the automatic parking function is met (“Yes” of S 17 ). On the other hand, if a condition to terminate is met during the series of operations of the automatic parking function, the automatic parking controller  13  terminates the process of  FIGS. 4 and 5  and does not resume the process, When the automatic parking function is to start again, the automatic parking controller  13  begins the operational steps from S 1 . The “condition to terminate” may be met if, for example, one of the following criteria is met during the series of operations of the automatic parking function: (a) the gearshift  64  is shifted to a P range; (b) an electric park brake comes into operation; and (c) an instruction to operate the parking brake function has been input via the touch panel  32 . Furthermore, if a condition to halt the automatic parking function is met during the series of operations of the automatic parking function, the series of operations of the automatic parking function is brought to a halt. However, in this case, the series of operations of the automatic parking function is resumed from the point at which the operation has been halted if the condition to halt is removed. The “condition to halt” exists if a criterion is met such as an operation of the brake pedal (not shown). 
       FIG. 11  is a flowchart of a subroutine for the determination process of a parking location of S 6  in  FIG. 4 . Words expressing directions such as “front” and “rear” are used to describe directions from the viewpoint of the host vehicle  100  that is pausing at the change-to-reverse location  262  (see  FIG. 9 ). The process of  FIG. 11  is performed based on a situation of the surroundings of the host vehicle  100  as recognized by the recognition part  11 . The operational steps of  FIG. 11  is executed when individual parking regions of the parking area  200  is not separated by a white line  201  (a boundary line, see  FIG. 3C ). The parking location determiner  14  determines whether the parking area  200  has parking regions that are separated by a white line  301  (a boundary line) (S 21 ). If the parking area  200  does not have parking regions separated by a white line (a boundary line) (“No” of S 21 ), the following operational steps are executed. 
     As shown in  FIG. 12 , even when the parking area  200  does not have a white line  201  (a boundary line) separating parking regions, the parking region determiner  12  finds a parking space  202   a  based on the surrounding situation of the host vehicle  100  as recognized by the recognition part  11  so that the driver may select this parking space  202   a  as the parking-target parking region. In this case, an entry width H 1  of the parking space  202   a  may be detected from the recognition result of the recognition part  11 , Other vehicles  203  are parked on the left and right sides of the parking space  202   a.  When a space is found between the pair of other vehicles  203  and when, from the width of entry and depth of the space, it is determined that there is appropriate space for parking the host vehicle  100 , then that space becomes selectable as a parking space  202   a  (a parking region) for parking the host vehicle  100  (“Yes” of S 5 ). 
     When the parking space  202   a  of  FIG. 12  is selected as the parking-target parking region for the “Yes” of S 5 , the parking location determiner  14  determines whether the entry width H 1  of the parking space  202   a  (a parking region) is less than a predetermined value (S 22 ). This predetermined value may, for example, be 1.5 times the width of the host vehicle  100 . When the entry width H 1  of the parking space  202   a  is less than the predetermined value (“Yes” of S 22 ), the parking location determiner  14  determines that the parking location of the host vehicle  100  within the parking space  202   a  (a parking region) is at a central location as viewed from the entry side of the parking space  202   a  (a parking region) (S 23 ). Therefore, as shown in  FIG. 13 , the central location of the parking space  202   a  (a parking region) as viewed from the entry side thereof (i.e., a location that is equally distanced from the other vehicle  203  on the left side and the other vehicle  203  on the right side of the parking space  202   a ) is decided as the parking location of the host vehicle  100 . 
     When determining whether the entry width H 1  of the parking space  202   a  (a parking region) is less than the predetermined value in S 22 , the parking location determiner  14  uses an outer edge part of a side of the other vehicle  203  on the left side of the parking space  202   a  and an outer edge part of a side of the other vehicle  203  on the right side of the parking space  202   a  (in the given example, corners  203   a ) as reference points of the entry width H 1 . 
     When the entry width H 1  of the parking space  202   a  is equal to or greater than the predetermined value (“No” of S 22 ), then as shown in  FIG. 14 , the parking location determiner  14  determines that the parking location of the host vehicle  100  is at a location that is closer to one of the other vehicles  203  on the left and right sides of the parking space  202   a  (a parking region) as viewed from the entry side of the parking space  202   a  (S 24 ). 
     In some embodiments, the parking location determiner  14  sets a distance by which the parking location of the host vehicle  100  is shifted (hereinafter also a “shift distance”) to a predetermined distance H 2 , the predetermined distance H 2  being a distance from a line L extending lengthways from a central point of the parking space  202   a  (a parking region) as viewed from the entry side thereof to the rear side of the parking region. (In other words, the predetermined distance H 2  is a distance away from the center of the parking space  202   a  in the direction of width of the parking region.) In some embodiments, the parking location is selected so that there is a predetermined space between the host vehicle  100  and the other vehicle  203  that the host vehicle  100  is parked closer to, the predetermined space providing enough space to enable doors to be opened and passengers to get in and out of within that predetermined space. 
     In the example of  FIG. 14 , a stopping location of the host vehicle  100  is determined to be at a location closer to the other vehicle  203  on the right as viewed from the driver of the host vehicle  100 . In some embodiments, the parking location determiner  14  decides on which of the other vehicles  203  on the left and right sides of the parking space  202   a  the host vehicle  100  is to park closer to based on a position of the host vehicle  100 . For example, the parking location may be determined so that the host vehicle  100  parks closer to the other vehicle  203  that is closest to a position of the host vehicle  100  when the automatic brake hold is turned on and the host vehicle  100  has stopped (S 6 ). 
     In some embodiments, when the parking location determiner  14  decides on which of the other vehicles  203  on the left and right sides of a parking region the host vehicle  100  is to park closer to, a decision according to a ground surface condition of the parking area  200  in which the host vehicle  100  performs the parking operation may be prioritized (priority to a ground surface condition). In this case, a parking location does not have to be closer to the other vehicle  203  that is closest to the position that the host vehicle  100  has stopped. To be more specific, when the camera group  21  ( FIG. 1 ) detects that the ground on which the host vehicle  100  travels has an uneven surface and when a means of better avoiding uneven parts of the ground for the travel route or parking location that are determined in S 6  is to park the host vehicle  100  closer to a particular one of the other vehicles  203 , then a parking location that is closer to the particular one of the other vehicles  203  is selected as the parking location of the host vehicle  100 . 
     In some embodiments, when the parking location determiner  14  decides on which of the other vehicles  203  on the left and right sides of a parking region the host vehicle  100  is to park closer to, a decision according to types of the other vehicles  203  may be prioritized (priority to vehicle types). In this case, a parking location does not have to be closer to the other vehicle  203  that is closest to the position that the host vehicle  100  has stopped. To be more specific, a parking location that is closer to a smaller sized one of the other vehicles  203  on the left and right sides is selected so that a larger sized vehicle is avoided. 
     Note that in, the above description of the process of  FIG. 11 , operational steps when the parking area  200  does not have a white line  201  (a boundary line) separating parking regions have been described. In cases where the parking area  200  has a white line  201  (a boundary line) separating parking regions, various algorithms may be used to determine a parking location. in some embodiments, a parking location within a parking region is decided so that the host vehicle  100  is equally distanced from the left and right white lines  201  that demarcate the parking region. Furthermore, the parking location determination described above has been concerned with determining a parking location in a direction to the left or right as viewed from the driver of the host vehicle  100 . To determine the parking location in a direction to the front or back (as viewed from the driver), various algorithms may be used such as (a) selecting a location that avoids an obstacle at the back of the host vehicle  100  such as another vehicle, or (b) selecting a location so that the rear end of the host vehicle  100  is aligned with the rear ends of the other vehicles  203  on the left and right. 
     In the example that has been described, a process in which the host vehicle  100  enters the parking space  202   a  (a parking region) from the rear end of the host vehicle  100  first (i.e., reverse parking). In some embodiments, the host vehicle  100  may enter the parking space  202   a  (a parking region) from the front end of the host vehicle  100  first (i.e., forward parking). 
     According to the automatic parking control unit  1  described above, when the entry width H 1  of the parking space  202   a  is less than a predetermined value (“Yes” of S 22 ), a location at the center of the parking space  202   a  as seen from the entry side thereof is determined by the parking location determiner  14  as the parking location of the host vehicle  100  within the parking space  202   a  (a parking region). In this way, when parking in a parking region with confined space to the left and right relative to the host vehicle  100 , the host vehicle  100  is able to park with adequate distance from other vehicles  203  on the right and the left. 
     In this case, during the decision of S 22 , the parking location determiner  14  is able to measure an entry width H 1  of the parking space  202   a  (a parking region) appropriately by using two reference points. One reference point is set to an outer edge part of a side of one of the other vehicles  203  on the left and right (a corner  203   a  for this example). The other reference point is set to an outer edge part of a side of the other one of the other vehicles  203  on the left and right (another corner  203   a  for this example). 
     When the entry width H 1  of the parking space  202   a  is equal to or greater than a predetermined value (“No” of S 22 ), the parking location, determiner  14  determines a parking location of the host vehicle  100  that is closer to one of the other vehicles  203  on the left and right of the parking space  202   a  (a parking region) as viewed from the entry side thereof (S 24 ). In this way, a wider space is made available between the host vehicle  100  and the other one of the other vehicles  203  on the left and right (i.e., the other vehicle  203  from which the parking location is shifted away). When this other one of the other vehicles  203  on the left and right leaves, a different other vehicle may use the wide space to park reasonably closely to the host vehicle  100  (with enough space between the different other vehicle and the host vehicle  100  to allow vehicle doors to open and for passengers to get in and out). In this way, the parking location of the host vehicle  100  that is determined by the automatic parking control unit  1  allows efficient use of space that is available for parking in the parking area  200 . 
     In one or more embodiments, the parking location determiner  14  sets the distance by which the parking location of the host vehicle  100  is shifted to a predetermined distance H 2  from a line L that is extended from a central point of the parking space  202   a  (a parking region) as viewed from the entry side thereof to the rear side of the parking region (hence the predetermined distance H 2  is a distance in the direction of a vehicle width from a midsection as shown in  FIG. 14 ). Therefore, a location may be selected as the parking location of the host vehicle  100  that is not too close to the other vehicle  203  to which side the host vehicle  100  is shifted. In one or more embodiments, the parking location is selected so that there is a predetermined space between the host vehicle  100  and the other vehicle  203  that the host vehicle  100  is shifted closer to so that the predetermined space allows doors to be opened and passengers to get into and out of vehicles in the predetermined space. 
     In one or more embodiments, when deciding on which of the other vehicles  203  on the left and right the host vehicle  100  is to park closer to, the parking location determiner  14  bases the decision on the current position of the host vehicle  100 . More specifically, for example, a parking location is determined so that the host vehicle  100  parks closer to the other vehicle  203  that is closest to a position at which the host vehicle  100  has stopped. In this way, the distance the host vehicle  100  is driven while performing a parking operation is minimized, reducing the disturbance the parking operation may cause to other vehicles and pedestrians and contributing to reducing the consumption of fuel (or electricity). 
     In one or more embodiments, when the parking location determiner  14  decides on which of the other vehicles  203  on the left and right the host vehicle  100  is to park closer to, a decision according to a ground surface condition of the parking area  200  in which the host vehicle  100  performs the parking operation may be prioritized. Therefore, by avoiding a path with an uneven surface, the automatic parking control unit  1  may avoid a decline in the quality of ride on the host vehicle  100  during the parking operation. 
     In one or more embodiments, when the parking location determiner  14  decides on which of the other vehicles  203  on the left and right the host vehicle  100  is to park closer to, a decision according to types of the other vehicles  203  may be prioritized. More specifically, a parking location may be determined so that a larger vehicle is avoided by parking the host vehicle  100  closer to a smaller one of the other vehicles  203 . Large sized vehicles require wider space to maneuver and are more likely to come into contact with the host vehicle  100  when they leave a parking space compared to smaller sized vehicles. Parking closer to a smaller vehicle, therefore, reduces the likelihood of such a collision with a large sized vehicle.