Patent Publication Number: US-2020298832-A1

Title: Parking support apparatus

Description:
TECHNICAL FIELD 
     Embodiments of the present invention relate to a parking support apparatus. 
     BACKGROUND ART 
     Conventionally, parking support apparatuses that perform parking support by automatic steering have been known. The parking support apparatuses guide a vehicle along a movement route specified based on the positional relation between a parking area and the vehicle. 
     CITATION LIST 
     Patent Literature 
     Patent Document 1: Japanese Patent Application Laid-open No. 2010-269707 
     SUMMARY OF INVENTION 
     Problem to be Solved by Invention 
     However, the vehicle may be deviate the specified movement route due to various factors, such as operations performed by a driver, parking environment, or difference in operations between vehicles. In such case of the conventional parking support apparatus, parking accuracy is lowered and turning-back operations to correct the parking position are increased. There is a demand for parking support apparatuses that can guide a vehicle to a target position with higher accuracy. 
     Means for Solving Problem 
     A parking support apparatus according to an embodiment of the present invention includes, for example: a storage unit configured to store in advance a plurality of movement routes having different turning radii of a vehicle; a selecting unit configured to select one movement route from the plurality of movement routes based on magnitude of difference between a direction of the vehicle to a target position at a turning-back position where the vehicle turns back and a direction of the vehicle to the target position when the vehicle is positioned on the movement route; and a movement control unit configured to move the vehicle based on the selected movement route. The parking support apparatus according to the embodiment can guide the vehicle to the target position with higher accuracy. 
     The parking support apparatus further includes, for example, an inclination calculating unit configured to calculate a vehicle inclination angle that is an intersection angle between a longitudinal direction of the vehicle at the turning-back position and a first direction extending along an entrance of a target parking area, and a movement route inclination angle that is an intersection angle between the first direction and the longitudinal direction of the vehicle at an intersection of the movement route and a reverse start reference line being parallel to a second direction perpendicular to the first direction and passing through the turning-back position. The target parking area includes the target position. The selecting unit selects the movement route having an absolute value of difference between the vehicle inclination angle and the movement route inclination angle equal to or smaller than a threshold. Consequently, the parking support apparatus according to the embodiment can reduce the number of movement routes stored in the storage unit while securing parking accuracy of a predetermined level or higher. 
     In the parking support apparatus, for example, the movement route that turns at a position closer to the target parking area out of the plurality of movement routes has a smaller turning radius. The selecting unit selects the movement route closer to the target parking area than the turning-back position is. Consequently, the parking support apparatus according to the embodiment can prevent the vehicle from passing on frame lines and the like surrounding the target parking area, thereby guiding the vehicle to the target parking area with higher accuracy. 
     In the parking support apparatus, when there are movement routes being selectable, the selecting unit selects the movement route having a smaller absolute value of difference between the vehicle inclination angle and the movement route inclination angle. Consequently, the parking support apparatus according to the embodiment can select the movement route closer to the present position and direction of the vehicle and shift the vehicle to the selected movement route more smoothly. 
     The parking support apparatus further includes a route correcting unit configured to translate the movement route selected by the selecting unit to the turning-back position in the second direction. Consequently, the parking support apparatus according to the embodiment can perform parking support along the selected movement route from the present position of the vehicle without moving the vehicle to shift it to the selected movement route. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is an exemplary perspective view illustrating part of a cabin of a vehicle according to an embodiment in a cutaway manner; 
         FIG. 2  is a diagram of an example of the hardware configuration of a vehicle control system including an ECU according to the embodiment; 
         FIG. 3  is a block diagram of an example of the functional configuration of the ECU according to the embodiment; 
         FIG. 4  is a view of an example of resetting routes according the embodiment; 
         FIG. 5  is a view of an example of offsetting the resetting route according to the embodiment; 
         FIG. 6  is a flowchart of an example of a process of selecting the resetting route according to the embodiment; and 
         FIG. 7  is a diagram for explaining an example of conventional techniques. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Exemplary embodiments of a parking support apparatus according to the present embodiment mounted on a vehicle  1  are described below. 
       FIG. 1  is an exemplary perspective view illustrating part of a cabin  2   a  of the vehicle  1  according to the present embodiment in a cutaway manner. The vehicle  1  provided with a vehicle control device according to the present embodiment may be a car including an internal combustion engine, which is not illustrated, as a driving source, that is, an internal combustion engine car, for example. Alternatively, the vehicle  1  may be a car including a motor, which is not illustrated, as a driving source, that is, an electric car or a fuel cell car, for example. Still alternatively, the vehicle  1  may be a hybrid car including an internal combustion engine and a motor as a driving source or a car including another driving source. The vehicle  1  may be provided with various transmissions and various devices, such as systems and parts needed for driving the internal combustion engine and the motor. 
     As illustrated in  FIG. 1 , a vehicle body  2  defines the cabin  2   a  in which a passenger, which is not illustrated, rides. The cabin  2   a  is provided with a steering unit  4 , an acceleration operating unit  5 , a braking operating unit  6 , and a transmission operating unit  7 , for example, facing a seat  2   b  for a driver serving as the passenger. 
     The steering unit  4  is a steering wheel (handle) protruding from a dashboard  24 , for example. The acceleration operating unit  5  is an accelerator pedal provided at the driver&#39;s feet, for example. The braking operating unit  6  is a brake pedal provided at the driver&#39;s feet, for example. The transmission operating unit  7  is a shift lever protruding from a center console, for example. The steering unit  4 , the acceleration operating unit  5 , the braking operating unit  6 , and the transmission operating unit  7  are not limited thereto. 
     The cabin  2   a  is also provided with a display device  8  serving as a display output unit and a sound output device  9  serving as a sound output unit. The display device  8  is a liquid crystal display (LCD) or an organic electroluminescent display (OELD), for example. The sound output device  9  is a speaker, for example. The display device  8  is covered with a transparent operation input unit  10 , such as a touch panel. The passenger can visually recognize an image displayed on a display screen of the display device  8  through the operation input unit  10 . The passenger can perform an operating input by contacting, pressing, and moving the operation input unit  10  with a finger or the like at a position corresponding to the image displayed on the display screen of the display device  8 . The display device  8 , the sound output device  9 , and the operation input unit  10 , for example, are provided to a monitor device  11  positioned at the center of the dashboard  24  in the vehicle width direction, that is, in the lateral direction. The monitor device  11  may include an operation input unit, such as a switch, a dial, a joystick, and a push button, which is not illustrated. The cabin  2   a  may be provided with a second sound output device, which is not illustrated, at another position different from the position of the monitor device  11 . Sound may be output from the sound output device  9  of the monitor device  11  and the second sound output device. The monitor device  11  can also be used as a navigation system and/or an audio system, for example. The cabin  2   a  may be provided with another display device different from the display device  8 . 
     As illustrated in  FIG. 1 , the vehicle body  2  is provided with four imaging units  15   a  to  15   d  as a plurality of imaging units  15 , for example. The imaging unit  15  is a digital camera including an imaging element, such as a charge-coupled device (CCD) and a CMOS image sensor (CIS). The imaging unit  15  can output video data at a predetermined frame rate. The imaging unit  15  successively photographs external environments around the vehicle body  2  including a road surface on which the vehicle  1  can move and an area in which the vehicle  1  can park, and outputs the obtained image as captured image data. 
     The imaging unit  15   a  is positioned at a rear end  2   e  of the vehicle body  2  and provided on a wall at a lower part of a door  2   h  of a rear trunk, for example. The imaging unit  15   b  is positioned at a right end of the vehicle body  2 , for example. The imaging unit  15   b  is provided on a right door mirror  2   g , for example. The imaging unit  15   c  is positioned at a front part of the vehicle body  2 , that is, at a front end in the vehicle longitudinal direction, for example. The imaging unit  15   c  is provided on a front bumper, for example. The imaging unit  15   d  is positioned at a left part of the vehicle body  2 , that is, at a left end in the vehicle width direction, for example. The imaging unit  15   d  is provided on a left door mirror  2   g  serving as a protrusion, for example. The number of imaging units  15  is not limited to four and may be five or more or one. 
     As illustrated in  FIG. 1 , the vehicle  1  is a four-wheel car, for example, and includes two left and right front wheels  3 F and two left and right rear wheels  3 R. All these four wheels  3  can be steered. The system, the number, the layout, and other aspects of the devices relating to driving the wheels  3  in the vehicle  1  may be appropriately determined. 
     As illustrated in  FIG. 1 , the vehicle body  2  is provided with a plurality of distance measuring units  16  and  17 . The distance measuring units  16  and  17  are sonars (sonar sensors or ultrasonic locators) that output ultrasonic waves and receives reflected waves, for example. The distance measuring units  17  are used to detect an object present in a relatively short distance, for example. The distance measuring units  16  are used to detect an object present in a relatively long distance compared with the distance measuring units  17 , for example. The distance measuring units  17  are used to detect an object in front of and behind the vehicle  1 , for example. The distance measuring units  16  are used to detect an object at sides of the vehicle  1 . The numbers and the positions of the distance measuring units  16  and  17  provided to the vehicle body  2  are not limited to those in the example illustrated in  FIG. 1 . 
       FIG. 2  is a diagram of an example of the hardware configuration of a vehicle control system  100  including an electronic control unit (ECU)  14  according to the present embodiment. As illustrated in  FIG. 2 , the vehicle control system  100  includes the ECU  14 , the monitor device  11 , a steering system  13 , the distance measuring units  16  and  17 , a brake system  18 , a steering angle sensor  19  (angle sensor), an accelerator sensor  20 , a shift sensor  21 , and a wheel speed sensor  22 , for example. These components are electrically connected via an in-vehicle network  23  serving as an electrical communication line. 
     The in-vehicle network  23  is a controller area network (CAN), for example. 
     The ECU  14  transmits control signals via the in-vehicle network  23 , thereby controlling the steering system  13 , the brake system  18 , and other components. The ECU  14  can receive detection results from a torque sensor  13   b , a brake sensor  18   b , the steering angle sensor  19 , the distance measuring units  16  and  17 , the accelerator sensor  20 , the shift sensor  21 , and the wheel speed sensor  22  and instruction signals (control signals, operating signals, input signals, and data) from the operation input unit  10 , for example, via the in-vehicle network  23 . The ECU  14  is an example of the parking support apparatus according to the present embodiment. 
     The ECU  14  includes a central processing unit (CPU)  14   a , a read only memory (ROM)  14   b , a random access memory (RAM)  14   c , a display control unit  14   d , a sound control unit  14   e , a solid state drive (SSD or flash memory)  14   f , for example. 
     The CPU  14   a  reads out a computer program installed and stored in a nonvolatile storage device, such as the ROM  14   b , and can perform arithmetic processing based on the computer program. The RAM  14   c  temporarily stores various kinds of data used in the arithmetic processing performed by the CPU  14   a.    
     The display control unit  14   d  mainly performs image processing using image data acquired by the imaging units  15  and composes image data to be displayed on the display device  8 , for example, in the arithmetic processing performed by the ECU  14 . The display control unit  14   d , for example, performs arithmetic processing and image processing based on the image data acquired by the imaging units  15 . The display control unit  14   d  thus can generate an image having a wider angle of view and a virtual overhead image of the vehicle  1  viewed from above. The overhead image is also referred to as a plan image. 
     The sound control unit  14   e  mainly performs processing on sound data to be output from the sound output device  9  in the arithmetic processing performed by the ECU  14 . 
     The CPU  14   a  acquires operating signals due to an operating input performed on an operating unit  14   g . The operating unit  14   g  is a push button and/or a switch, for example, and outputs the operating signals. 
     The SSD  14   f  is a rewritable nonvolatile storage unit and can store data even when the ECU  14  is turned off. The CPU  14   a , the ROM  14   b , and the RAM  14   c , for example, can be integrated in a single package. Instead of the CPU  14   a , the ECU  14  may include another logic arithmetic processor, such as a digital signal processor (DSP), or another logic circuit, for example. Instead of the SSD  14   f , a hard disk drive (HDD) may be provided. The SSD  14   f  and the HDD may be separated from the ECU  14 . 
     The steering system  13  steers at least two wheels  3 . The steering system  13  according to the present embodiment steers the front wheels  3 F of the vehicle  1 . The steering system  13  includes an actuator  13   a  and a torque sensor  13   b . The steering system  13  is electrically controlled by the ECU  14  and other components, thereby causing the actuator  13   a  to operate. The steering system  13  is an electric power steering system or a steer-by-wire (SBW) system, for example. The steering system  13  adds torque, that is, assist torque to the steering unit  4  by the actuator  13   a  to supplement the steering force or turns the wheels  3  by the actuator  13   a . In this case, the actuator  13   a  may turn one wheel  3  or a plurality of wheels  3 . The torque sensor  13   b  detects torque supplied to the steering unit  4  by the driver, for example. 
     The brake system  18  is an anti-lock brake system (ABS) that prevents the brake from locking, an electronic stability control (ESC) that prevents the vehicle  1  from skidding in cornering, an electric brake system that increases brake force (performs brake assist), and/or a brake-by-wire (BBW) system, for example. The brake system  18  supplies braking force to the wheels  3 , that is, the vehicle  1  via an actuator  18   a . The brake system  18  can detect signs of locking of the brake and spinning and skidding of the wheels  3  based on a difference in rotation between the left and right wheels  3 , and can perform various kinds of control. The brake sensor  18   b  detects the position of a movable part of the braking operating unit  6 , for example. The brake sensor  18   b  can detect the position of the brake pedal serving as the movable part. The brake sensor  18   b  includes a displacement sensor. The brake sensor  18   b  transmits detection signals based on an operating input performed on the braking operating unit  6 , such as the brake pedal, to the ECU  14  via the brake system  18 . Alternatively, the brake sensor  18   b  may be configured to transmit detection signals based on an operating input performed on the brake pedal to the ECU  14  not via the brake system  18 . 
     The steering angle sensor  19  detects a steering amount (angle of rotation) of the steering unit  4  and is a Hall element, for example. The ECU  14  acquires, from the steering angle sensor  19 , the steering amount of the steering unit  4  by the driver and the steering amount of the wheels  3  in parking support by automatic steering, for example, and performs various kinds of control. When the braking operating unit  6  is operated in automatic steering, for example, the ECU  14  can determine that the vehicle  1  is in a state not suitable for automatic steering and suspend or stop automatic steering. 
     The accelerator sensor  20  detects the position of a movable part of the acceleration operating unit  5 , for example. The accelerator sensor  20  can detect the position of the accelerator pedal serving as the movable part. The accelerator sensor  20  includes a displacement sensor. 
     The shift sensor  21  detects the position of a movable part of the transmission operating unit  7 , for example. The shift sensor  21  can detect the position of a lever, an arm, a button, or the like serving as the movable part. The shift sensor  21  may include a displacement sensor. The shift sensor  21  may be a switch. 
     The wheel speed sensor  22  detects the rotation amount and the rotation rate per unit time of the wheels  3 . The wheel speed sensor  22  transmits a wheel speed pulse number indicating the detected rotation rate to the ECU  14  as a sensor value. The wheel speed sensor  22  is a Hall element, for example. The ECU  14  calculates the movement amount and the vehicle speed of the vehicle  1 , for example, based on the sensor value acquired from the wheel speed sensor  22  and performs various kinds of control. The wheel speed sensor  22  may be provided to the brake system  18 . In this case, the ECU  14  acquires the detection results of the wheel speed sensor  22  via the brake system  18 . 
     The configurations, the positions, the forms of electrical connection, and other aspects of the various sensors and the actuators described above are given by way of example only and may be appropriately determined (changed). 
       FIG. 3  is a block diagram of an example of the functional configuration of the ECU  14  according to the present embodiment. As illustrated in  FIG. 3 , the ECU  14  includes a detecting unit  141 , a target position determining unit  142 , a route calculating unit  143 , a movement control unit  144 , an own vehicle position estimating unit  145 , an inclination calculating unit  146 , a selecting unit  147 , a route correcting unit  148 , and a storage unit  150 . 
     The detecting unit  141 , the target position determining unit  142 , the route calculating unit  143 , the movement control unit  144 , the own vehicle position estimating unit  145 , the inclination calculating unit  146 , the selecting unit  147 , and the route correcting unit  148  illustrated in  FIG. 3  are provided by the CPU  14   a  executing a computer program stored in the ROM  14   b . These units may be provided by a hardware circuit. 
     The storage unit  150  is a storage device, such as the SSD  14   f , for example. The storage unit  150  stores information indicating a plurality of resetting routes in parking support. 
     The resetting route is a movement route of the vehicle  1  from a position where the vehicle  1  turns back to a target position in a target parking area when the vehicle  1  moves backward to enter into the target parking area. The resetting route is an example of a movement route according to the present embodiment. 
     The turning-back position of the vehicle  1  is a position of the vehicle  1  at which the vehicle  1  stops and the movable part of the transmission operating unit  7  is set to the reverse position. In parking support according to the present embodiment, the vehicle  1  is assumed to move forward from a position near the target parking area to a predetermined position, turn back, and then move backward to enter into the target parking area. The turning-back position of the vehicle  1  is also referred to as a reverse start position. 
       FIG. 4  is a view of an example of resetting routes R according the embodiment. Resetting routes R 1  to R 5  illustrated in  FIG. 4  enable the vehicle  1  to park in a target parking area F. The resetting route R according to the present embodiment enables the vehicle  1  to move to a target position P in the target parking area F, for example. In the following description, the individual routes are referred to as the resetting routes R when they are not particularly specified. 
     The target parking area F is a rectangular area surrounded by white lines  50 , for example. The target position P is a position where the vehicle  1  is assumed to stop when parking support is completed. The target position P is set on the center line extending in the longitudinal direction of the target parking area F, for example. 
     In the present embodiment, the position of the vehicle  1  is indicated by the position of the center of a rear wheel shaft connecting the two left and right rear wheels  3 R of the vehicle  1 . Instead of the center of the rear wheel shaft of the vehicle  1 , the position of the center of gravity of the vehicle  1  may be employed. 
     As illustrated in  FIG. 4 , the resetting routes R 1  to R 5  each include a turning part and a straight movement part. The resetting routes R 1  to R 5  have different turning radii in the turning part. 
     As illustrated in  FIG. 4 , the resetting routes R 1  to R 5  stored in the storage unit  150  are set such that a route turning at a position closer to the target parking area F has a smaller turning radius. As the turning radius is smaller, the turning angle of the vehicle  1  is sharper. Typically, as the vehicle  1  turns at a position closer to the target parking area F, the vehicle  1  comes closer to the white lines  50 , for example. To prevent the vehicle  1  from passing over the white lines  50  or exceeding the range of the target parking area F, the resetting route R closer to the target parking area F has a smaller turning radius. While the target parking area F according to the present embodiment is surrounded by the white lines  50 , it may be surrounded by obstacles, such as other vehicles and poles, depending on the parking places. Setting the resetting routes R as described above can prevent the vehicle  1  from coming into contact with the objects or the like surrounding the target parking area F. 
     While the turning parts of the respective resetting routes R are partially illustrated in  FIG. 4 , they further extend in an X-direction illustrated in  FIG. 4 . While the turning parts are represented as circular arcs in  FIG. 4 , the storage unit  150  may store the turning parts of the respective resetting routes R as circular routes, for example. 
     The straight movement parts of the respective resetting routes R are parallel to the longitudinal direction of the target parking area F. The straight movement parts of the respective resetting routes R are also parallel to a Y-direction illustrated in  FIG. 4 . The standards for setting the X-direction and the Y-direction illustrated in  FIG. 4  will be described later. 
     The straight movement parts of the respective resetting routes R according to the present embodiment are set such that the vehicle  1  moves straight at at least a point where the vehicle  1  enters into the target parking area F. The start position of the straight movement parts of the resetting routes R is not limited thereto and simply needs to be a route that enables the vehicle  1  to park in the target parking area F without passing over the white lines  50 . The position shifting from the turning part to the straight movement part in each of the resetting routes R may be determined based on the turning radii of the respective resetting routes R, the model of the vehicle  1 , and other factors. 
     While the storage unit  150  according to the present embodiment stores five types of resetting routes R, the number of resetting routes R stored in the storage unit  150  is not limited thereto. 
     Referring back to  FIG. 3 , the detecting unit  141  detects obstacles, such as other vehicles and poles, and frame lines, such as parking section lines, from an image of the periphery of the vehicle body  2  taken by the imaging units  15 . The detecting unit  141  detects a parking allowable area in the peripheral area of the vehicle  1  based on the detected obstacles, frame lines, and section lines, for example. 
     The target position determining unit  142  determines the target parking area F and the target position P of the vehicle  1  based on the detection results of the detecting unit  141 . When the detecting unit  141  detects a plurality of parking allowable areas, the target position determining unit  142  may receive a selection operation indicating which parking allowable area is determined to be the target parking area F from the driver. The target position determining unit  142  receives, for example, the selection operation from the driver as the operating signals acquired from the operating unit  14   g . In the example illustrated in  FIG. 4 , the target position determining unit  142  determines the area surrounded by the white lines  50  to be the target parking area F. The target position determining unit  142  determines the target position P in the target parking area F to include the vehicle body  2  within the target parking area F. 
     Referring back to  FIG. 3 , the route calculating unit  143  calculates a movement route for moving the vehicle  1  from the present position to the target position P when parking support is started. When receiving an instruction for starting parking support by the operating signals acquired from the operating unit  14   g , the route calculating unit  143  calculates a guide route. The movement route of the vehicle  1  calculated by the route calculating unit  143  is referred to as an initial route according to the present embodiment. 
     While the target position determining unit  142  and the route calculating unit  143  receive operations performed by the driver as the operating signals acquired from the operating unit  14   g , the operating input performed by the driver is not limited thereto. The target position determining unit  142  and the route calculating unit  143  may receive operations performed by the driver through the operation input unit  10  and perform the processing described above. 
     The movement control unit  144  performs steering control to move the vehicle  1  based on the initial route calculated by the route calculating unit  143 . Specifically, the route calculating unit  143  controls the actuator  13   a  of the steering system  13  based on the position of the vehicle  1  such that the vehicle  1  moves along the initial route. At this time, the vehicle  1  is accelerated or decelerated (braked) based on the operation performed by the driver on the acceleration operating unit  5  or the braking operating unit  6 . The movement control unit  144  may instruct the driver to perform the operation on the acceleration operating unit  5  or the braking operating unit  6  by displaying guidance on the monitor device  11 . 
     When the vehicle turns back, the selecting unit  147  according to the present embodiment, which will be described later, reviews the movement route. When the selecting unit  147  selects any one of the resetting routes R, the initial route is replaced by the resetting route R. When the selecting unit  147  selects any one of the resetting routes R, the movement control unit  144  moves the vehicle  1  based on the selected resetting route R. Specifically, the movement control unit  144  acquires a result of offsetting (correcting), by the route correcting unit  148 , the resetting route R selected by the selecting unit  147 . The movement control unit  144  moves the vehicle  1  based on the resetting route R resulting from offsetting. Selecting and offsetting the resetting route R will be described later in detail. 
     While the movement control unit  144  performs automatic steering, and the driver performs the other operations in parking support according to the present embodiment, the embodiment is not limited thereto. The movement control unit  144  may be configured to automatically control the operation on the acceleration operating unit  5  besides steering, for example. Furthermore, the movement control unit  144  may be configured to automatically control the operation on the transmission operating unit  7 . 
     The own vehicle position estimating unit  145  estimates the position and the direction of the vehicle  1  based on wheel speed information acquired from the wheel speed sensor  22 . Specifically, the own vehicle position estimating unit  145  acquires, as a sensor value, the wheel speed pulse number indicating the rotation rate of the wheels  3  detected by the wheel speed sensor  22 . The own vehicle position estimating unit  145  calculates the movement amount and the movement direction of the vehicle  1  based on the rotation rates of the two left and right front wheels  3 F and the two left and right rear wheels  3 R provided on the left and right sides of the vehicle body  2 . 
     The own vehicle position estimating unit  145  detects that the vehicle  1  turns back during parking support. The own vehicle position estimating unit  145  detects, for example, that the vehicle  1  stops and that the movable part of the transmission operating unit  7  is set to the reverse position during parking support. In such case, the own vehicle position estimating unit  145  adds the movement amount and the movement direction of the vehicle  1  after the start of parking support to the position of the vehicle  1  at the start of parking support. The own vehicle position estimating unit  145  thus estimates the turning-back position and the direction of the vehicle  1 . 
     The inclination calculating unit  146  calculates the inclination angle of the vehicle  1  at the turning-back position and calculates the inclination angle of the vehicle  1  on an assumption that the vehicle  1  is positioned on the resetting route R. The calculation of the inclination angles is specifically explained with reference to  FIG. 4 . 
     The X-direction illustrated in  FIG. 4  extends along the entrance of the target parking area F. The X-direction is also referred to as the width direction or the short direction of the target parking area F. The X-direction is also referred to as a direction perpendicular to an entrance direction and an exit direction of the vehicle  1  to the target parking area F. The X-direction according to the present embodiment is an example of a first direction. 
     The Y-direction illustrated in  FIG. 4  is perpendicular to the X-direction. The Y-direction extends in the longitudinal direction of the target parking area F. The Y-direction is also referred to as the lengthwise direction of the target parking area F. The Y-direction is also referred to as the entrance direction and the exit direction of the vehicle  1  to the target parking area F. The Y-direction according to the present embodiment is an example of a second direction. 
     In the example illustrated in  FIG. 4 , the point of intersection of the X-direction and the Y-direction is the midpoint of the length of the target parking area F in the short direction, for example. In the present embodiment, it is assumed that the own vehicle position estimating unit  145  and the inclination calculating unit  146  calculate the X-coordinates and the Y-coordinates of the vehicle  1  and the resetting routes R with respect to the intersection as the origin. It is also assumed that a point positioned in the right direction of the X-direction in  FIG. 4  has a larger X-coordinate. It is also assumed that a point positioned in the upper direction of the Y-direction in  FIG. 4  has a larger Y-coordinate. The standards for calculating the positions of the vehicle  1 , the resetting routes R, and others are not limited thereto. 
     A point A illustrated in  FIG. 4  is the turning-back position of the vehicle  1 . The position of the point A is, for example, a position where the driver operates the movable part of the braking operating unit  6  according to the guidance displayed on the monitor device  11  to stop the vehicle  1  and sets the movable part of the transmission operating unit  7  to the reverse position. The position indicated by the point A is hereinafter referred to as a turning-back position A. 
     The turning-back position A of the vehicle  1  according to the present embodiment is a position where the vehicle  1  actually turns back. Thus, the turning-back position A may be beyond the position for turning-back in the initial route calculated by the route calculating unit  143  or fall short of the position for turning-back. Furthermore, the turning-back position A according to the present embodiment may deviate from the position for turning-back in the initial route due to various factors, such as operations performed by the driver, parking environment, and difference in operations between vehicles. As described above, the turning-back position A is estimated by the own vehicle position estimating unit  145 . 
     A line  900  illustrated in  FIG. 4  indicates the longitudinal direction of the vehicle  1  at the turning-back position A. The intersection angle between the line  900  and the X-direction is referred to as a vehicle inclination angle θA of the vehicle  1 . The longitudinal direction of the vehicle  1  at the turning-back position A is an example of the direction of the vehicle  1  to the target position P. 
     The inclination calculating unit  146  estimates the line  900  based on the turning-back position A estimated by the own vehicle position estimating unit  145  and the position of the target parking area F specified by the target position determining unit  142 . The inclination calculating unit  146  calculates the vehicle inclination angle θA that is the intersection angle between the line  900  and the X-direction. 
     A line L illustrated in  FIG. 4  is a reverse start reference line L of the vehicle  1 . The reverse start reference line L is parallel to the Y-direction and passes through the turning-back position A. 
     A point B illustrated in  FIG. 4  is an intersection point B of the resetting route R 2  and the reverse start reference line L. In other words, the intersection point B indicates a position where the X-coordinate of the resetting route R 2  is equal to that of the turning-back position A. 
     A line  800  illustrated in  FIG. 4  indicates the longitudinal direction of the vehicle  1  when the vehicle  1  is positioned at the intersection point B on the resetting route R 2 . The intersection angle between the line  800  and the X-direction is referred to as an inclination angle θB of the resetting route R 2 . The longitudinal direction of the vehicle  1  at the intersection point B is an example of the direction of the vehicle  1  to the target position P when the vehicle  1  is positioned on the resetting route R. 
     The inclination calculating unit  146  calculates the position of the intersection point B from the turning-back position A estimated by the own vehicle position estimating unit  145  and the track of the resetting route R 2  stored in the storage unit  150 . The inclination calculating unit  146  estimates the line  800  based on the position of the intersection point B and the position of the target parking area F. The inclination calculating unit  146  calculates the inclination angle θB of the resetting route R 2 , which is the intersection angle between the line  800  and the X-direction. 
     While the intersection point B of the resetting route R 2  is representatively illustrated in  FIG. 4 , the inclination calculating unit  146  also calculates positions of the intersection points B of the reverse start reference line L and the respective resetting routes R 1  and R 3  to R 5 . The inclination calculating unit  146  also calculates the intersection angles between the longitudinal direction of the vehicle  1  and the X-direction when the vehicle  1  is positioned on the resetting routes R 1  and R 3  to R 5 . In other words, the inclination calculating unit  146  calculates the inclination angle θB of each of the resetting routes R 1  to R 5 . The inclination angle θB of the resetting route R is an example of a movement route inclination angle according to the present embodiment. 
     The inclination calculating unit  146  calculates the difference between the vehicle inclination angle θA and the inclination angles θB of the respective resetting routes R. 
     Referring back to  FIG. 3 , when the vehicle  1  turns back, the selecting unit  147  selects the resetting route R that satisfies conditions from the resetting routes R 1  to R 5 . In other words, the selecting unit  147  reviews the movement route for parking the vehicle  1  in the target parking area F when the vehicle  1  turns back. 
     Specifically, concerning the first condition, the selecting unit  147  compares a predetermined threshold and an absolute value of the difference between the vehicle inclination angle θA and the inclination angles θB of the respective resetting routes R calculated by the inclination calculating unit  146 . The selecting unit  147  extracts resetting routes R having an absolute value of the difference between the vehicle inclination angle θA and the inclination angles θB of the respective resetting routes R equal to or smaller than the predetermined threshold. In the present embodiment, it is assumed that the resetting routes R 1  to R 4  in the resetting routes R 1  to R 5  illustrated in  FIG. 4  satisfy the first condition. 
     The threshold is a value indicating an allowable range of the difference in inclination between the vehicle inclination angle θA and the inclination angles θB of the respective resetting routes R. Even when the vehicle inclination angle θA and the inclination angle θB do not completely match, but the absolute value of the difference between the two angles is equal to or smaller than the threshold, the movement control unit  144  will be able to move the vehicle  1  toward the target parking area F along the resetting route R corresponding to the inclination angle θB. With the threshold, the number of resetting routes R stored in the storage unit  150  in advance can be reduced while securing parking accuracy of a predetermined level or higher. The threshold may be determined based on the model of the vehicle  1 , for example. The threshold may be stored in the storage unit  150  in advance. 
     Concerning the second condition, the selecting unit  147  compares the turning-back position A with the position of the intersection point B. The selecting unit  147  extracts a resetting route R having the Y-coordinate of the intersection point B smaller than that of the turning-back position A. 
     When the Y-coordinate of the intersection point B is smaller than that of the turning-back position A, the distance between the intersection point B and the target parking area F is shorter than that between the turning-back position A and the target parking area F. In other words, the selecting unit  147  extracts the resetting route R closer to the target parking area F than the turning-back position A is. In the example illustrated in  FIG. 4 , the resetting routes R 1  and R 2  satisfy the second condition because they are positioned closer to the target parking area F than the turning-back position A is. By contrast, the resetting route R 3  does not satisfy the second direction because it passes through a position in the Y-direction with respect to the center of the turning-back position A and is positioned farther away from the target parking area F than the turning-back position A is. 
     In the example illustrated in  FIG. 4 , the resetting routes R 1  and R 2  satisfy both the first condition and the second condition. When there are resetting routes R that satisfy the conditions, the selecting unit  147  selects the resetting route R having a smaller absolute value of the difference between the vehicle inclination angle θA and the inclination angle θB. In the example illustrated in  FIG. 4 , the resetting route R 2  has a smaller absolute value of the difference between the vehicle inclination angle θA and the inclination angle θB than that of the resetting route R 1 . In this case, the selecting unit  147  therefore selects the resetting route R 2  as an object to be reset. 
     When only one resetting route R satisfies both the first condition and the second condition, the selecting unit  147  selects this resetting route R satisfying the conditions as an object to be reset. 
     When no resetting route R satisfies both the first condition and the second condition, the selecting unit  147  selects none of the resetting routes R. In this case, the movement control unit  144  resumes parking support for the vehicle  1  based on the initial route. When the movement control unit  144  moves the vehicle  1  based on the initial route and then the vehicle  1  turns back again, selection of the resetting route R is carried out again based on the turning-back position A. When the initial route includes two or more times of turning-back, the selection of the resetting route R is carried out at each of timings of turning-back. When the resetting route R satisfying the conditions is selected at any one of the timings of turning-back included in the initial route, the vehicle  1  may possibly park in the target parking area F by a smaller number of times of turning-back than originally expected. 
     Furthermore, a case may arise, where it is difficult to continue parking support based on the initial route like a case where the turning-back position A of the vehicle  1  greatly deviates from the initial route. In such cases, the movement control unit  144  may display guidance on the monitor device  11 , for example, thereby notifying the driver of termination of parking support or instructing the driver to start manual operations. The driver may newly start parking support by operating the operating unit  14   g . When parking support is newly started, the route calculating unit  143  calculates another initial route. 
     In the present embodiment, both the first condition and the second condition are essential conditions. Alternatively, it is possible to adopt a configuration in which either the first condition or the second condition is essential. 
     As illustrated in  FIG. 4 , the target position P according to the present embodiment is included in the target parking area F. In other words, the selecting unit  147  selects one route from a plurality of resetting routes R based on the magnitude of difference between the direction of the vehicle  1  at the turning-back position A to the target position P and the direction of the vehicle  1  to the target position P when the vehicle  1  is positioned on the resetting route R. 
     Even when the vehicle  1  turns back at a position deviating from the set initial route, the vehicle can park at the target position P by selecting the resetting route R at the turning-back position A by the selecting unit  147 . Consequently, deterioration of the parking accuracy is suppressed. Even when errors are accumulated from the start of parking support, those errors can be eliminated by selecting the resetting route R at the turning-back position A by the selecting unit  147 . In other words, the ECU  14  according to the present embodiment can guide the vehicle  1  to the target position P with higher accuracy by the selecting unit  147  that selects the resetting route R at the turning-back position A. 
     Conventionally, when the vehicle is parked within the range of the target parking area, but the parking position of the vehicle deviates from the target position, turning-back operation for correcting the parking position tends to increase. By contrast, according to the present embodiment, the vehicle  1  can park at the target position P by the selecting unit  147  that selecting the resetting route R at the turning-back position A. Consequently, the present embodiment can suppress the increase in the number of turning-back operations. 
     The selecting unit  147  selects the resetting route R regardless of whether the turning-back position A of the vehicle  1  deviates from the initial route. The turning-back position A is closer to the target parking area F than the position of the vehicle  1  is at the timing when the initial route is calculated. The selecting unit  147  selects the resetting route R at the turning-back position A, thereby selecting the route more suitable for parking the vehicle  1  in the target parking area F. In other words, the selecting unit  147  reviews the movement route at the turning-back position A, thereby increasing the parking accuracy. 
     Referring back to  FIG. 3 , the route correcting unit  148  offsets the resetting route R selected by the selecting unit  147 . Specifically, the route correcting unit  148  translates the resetting route R selected by the selecting unit  147  to the turning-back position A in the Y-direction. 
       FIG. 5  is a view of an example of offsetting the resetting route R according to the present embodiment. As illustrated in  FIG. 5 , the route correcting unit  148  translates the resetting route R 2  selected by the selecting unit  147  to the turning-back position A in the Y-direction. Since the X-coordinate of the turning-back position A is equal to that of the intersection point B, the intersection point B shifts to the turning-back position A by the route correcting unit  148  translating the resetting route R 2  in the Y-direction. The route resulting from offsetting the resetting route R 2  is referred to as a resetting route R 2 ′. 
     More specifically, as illustrated in  FIG. 5 , the route correcting unit  148  translates the turning part of the resetting route R 2 . The straight movement part of the resetting route R 2  extends in parallel with the Y-direction by translating the turning part of the resetting route R 2  by the route correcting unit  148 . 
     When selection of the resetting route R is carried out, the vehicle  1  stops at the turning-back position A. Thus, the vehicle  1  can move toward the target parking area F from the turning-back position A that is the current stop position by the route correcting unit  148  offsetting the resetting route R 2 . 
     The following describes selection of the resetting route R according to the present embodiment explained above.  FIG. 6  is a flowchart of an example of a process of selecting the resetting route R according to the present embodiment. The processing of the flowchart is started when the parking support is being performed by the ECU  14 . It is assumed that the processing of the flowchart is started when, for example, the movement control unit  144  starts to move the vehicle  1  along the initial route calculated by the route calculating unit  143 . 
     The own vehicle position estimating unit  145  determines whether the vehicle  1  stops and whether the movable part of the transmission operating unit  7  is set to the reverse position during the parking support (S 1 ). When the vehicle  1  does not stop or when the vehicle  1  stops but the movable part of the transmission operating unit  7  is not set to the reverse position (No at S 1 ), the own vehicle position estimating unit  145  performs the processing at S 1  again. 
     When the own vehicle position estimating unit  145  detects that the vehicle  1  stops and that the movable part of the transmission operating unit  7  is set to the reverse position during parking support (Yes at S 1 ), the own vehicle position estimating unit  145  estimates the position and the direction of the vehicle  1  (S 2 ). The position of the vehicle  1  at this timing corresponds to the turning-back position A of the vehicle  1 . 
     The inclination calculating unit  146  calculates the vehicle inclination angle θA (S 3 ). Specifically, the inclination calculating unit  146  estimates the line  900  indicating the longitudinal direction of the vehicle  1  at the turning-back position A based on the turning-back position A estimated by the own vehicle position estimating unit  145  and the position of the target parking area F specified by the target position determining unit  142 . The inclination calculating unit  146  then calculates the vehicle inclination angle θA that is the intersection angle between the line  900  and the X-direction extending along the entrance of the target parking area F. 
     The inclination calculating unit  146  calculates the inclination angles θB of the respective resetting routes R (S 4 ). Specifically, the inclination calculating unit  146  calculates the position of the intersection point B from the turning-back position A estimated by the own vehicle position estimating unit  145  and the track of the resetting route R 2  stored in the storage unit  150 . The inclination calculating unit  146  estimates the line  800  indicating the longitudinal direction of the vehicle  1  when the vehicle  1  is positioned at the intersection point B on the resetting route R 2 , based on the position of the intersection point B and the position of the target parking area F. The inclination calculating unit  146  calculates the inclination angles θB of the respective resetting routes R, which is the intersection angle between the line  800  and the X-direction extending along the entrance of the target parking area F. 
     The inclination calculating unit  146  calculates the difference between the vehicle inclination angle θA and the inclination angles θB of the respective resetting routes R. 
     The selecting unit  147  determines whether there is a resetting route R that satisfies both the first condition and the second condition. Specifically, the selecting unit  147  determines whether there is a resetting route R having an absolute value of the difference between the vehicle inclination angle θA and the inclination angle θB of the resetting route R equal to or smaller than the predetermined threshold and having the Y-coordinate of the intersection point B smaller than that of the turning-back position A (point A) (S 5 ). 
     When there is no resetting route R that satisfies both the first condition and the second condition (No at S 5 ), the selecting unit  147  selects none of the resetting routes R. In this case, the movement control unit  144  continues parking support for the vehicle  1  based on the initial route (S 6 ). When it is difficult to continue parking support based on the initial route, the movement control unit  144  may display guidance on the monitor device  11 , for example, thereby notifying the driver of termination of parking support or instructing the driver to start manual operations. 
     When there is a resetting route R that satisfies both the first condition and the second condition (Yes at S 5 ), the selecting unit  147  determines whether the number of resetting routes R satisfying the both conditions is two or more (S 7 ). 
     When the number of resetting routes R satisfying the both conditions is not two or more (No at S 7 ), that is, when the number of resetting routes R satisfying the conditions is one, the selecting unit  147  selects the resetting route R satisfying the conditions as an object to be reset (S 8 ). 
     When the number of resetting routes R satisfying the both conditions is two or more (Yes at S 7 ), that is, when there two or more resetting routes R that satisfy the both conditions, the selecting unit  147  selects the resetting route R having a smaller absolute value of the difference between the vehicle inclination angle θA and the inclination angle θB as an object to be reset (S 9 ). 
     The route correcting unit  148  offsets the resetting route R selected by the processing at S 8  or S 9  to the turning-back position A in the Y-direction (S 10 ). The offsetting performed by the route correcting unit  148  causes the intersection point B on the resetting route R to shift to the turning-back position A. 
     The movement control unit  144  resumes parking support for the vehicle  1  based on the resetting route R resulting from the offsetting (S 11 ). 
     At this point, processing of the flowchart is terminated. When parking support is resumed by the processing at S 6  or S 11 , the processing of the flowchart is performed again. 
     In some conventional parking support apparatuses, when the position of the vehicle deviates from the initial route set at the start of parking support, it may be difficult to guide the vehicle to the target parking area, or parking accuracy may be deteriorated, or turning-back operations for correcting the parking position may increase. 
       FIG. 7  is a diagram for explaining an example of conventional techniques. it is assumed that the initial route is set such that the vehicle moves forward, turns back, and then moves backward to park in the parking area, as illustrated in  FIG. 7( a ) . When the vehicle moves along the initial route, the driver stops the vehicle at the position illustrated in  FIG. 7( b )  and sets the movable part of the transmission operating unit  7  to the reverse position. 
     It is assumed, however, that the driver causes the vehicle to go beyond the turning-back position (position of the vehicle illustrated in  FIG. 7( b ) ) set in the initial route, stops the vehicle at the position illustrated in  FIG. 7( c ) , and then sets the movable part of the transmission operating unit  7  to the reverse position. Some conventional techniques have difficulty in correcting the initial route when the vehicle turns back at a position different from the turning-back position set in the initial route. In this case, the vehicle moves to a position different from the original target position because the vehicle follows a route having the same turning radius as that of the initial route but moves from a turning-back position different from that of the initial route. As a result, the vehicle is parked at a position deviating from the center of the target parking area, as illustrated in  FIG. 7( c ) . In other words, in the example illustrated in  FIG. 7( c ) , a difference arises between the actual parking position and the target parking position, thereby resulting in lower parking accuracy. When the parking support apparatus or the driver in the above state performs alignment operation for parking the vehicle at the center of the target parking area, the number of turning-back operations may increase. 
     Some conventional parking support apparatuses have lower parking accuracy and other disadvantages not only when the driver causes the vehicle to go beyond the turning-back position set in the initial route and then stops the vehicle but also when the driver stops the vehicle before the turning-back position. Furthermore, some conventional parking support apparatuses have lower parking accuracy and other disadvantages when the vehicle does not follow the initial route due to various factors, such as parking environment and difference in operations between vehicles, other than the operations performed by the driver. With the vehicle deviating from the initial route, some conventional parking support apparatuses have difficulty in continuing parking support and switch to manual driving. 
     By contrast, in the ECU  14  according to the present embodiment, the selecting unit  147  selects the resetting route R at the turning-back position A. Thus, even when the vehicle  1  does not follow the initial route, the ECU  14  according to the present embodiment can park the vehicle  1  at the target position P with higher accuracy and suppress the increase in the number of turning-back operations. 
     As described above, in the ECU  14  according to the present embodiment, the storage unit  150  stores in advance a plurality of resetting routes R having different turning radii of the vehicle  1 . The selecting unit  147  selects, at the turning-back position A, one of the resetting routes R. At that time, the selecting unit  147  selects one resetting route R based on the magnitude of difference between the direction of the vehicle  1  at the turning-back position A to the target position P and the direction of the vehicle  1  to the target position P when the vehicle  1  is positioned on the movement route. Consequently, even when the vehicle  1  turns back at the turning-back position A different from the position set on the initial route, the ECU  14  according to the present embodiment can shift the vehicle  1  to the resetting route R for moving the vehicle  1  to the target position P. Therefore, the ECU  14  according to the present embodiment can guide the vehicle to the target position P with higher accuracy. Since the ECU  14  according to the present embodiment can guide the vehicle to the target position P along the resetting route R, it is possible to suppress the increase in the number of alignment and turning-back operations. As described above, in the ECU  14  according to the present embodiment, the storage unit  150  stores in advance a plurality of resetting routes R. Thus, it is possible to lower the processing load in comparison with a case where another movement route is newly calculated. 
     The inclination calculating unit  146  of the ECU  14  according to the present embodiment calculates the vehicle inclination angle θA and the inclination angles θB of the respective resetting routes R. The selecting unit  147  selects the movement route having an absolute value of the difference between the vehicle inclination angle θA and the inclination angle θB of the resetting route R equal to or smaller than the threshold. Consequently, the ECU  14  according to the present embodiment can reduce the number of resetting routes R stored in the storage unit  150  while securing parking accuracy of a predetermined level or higher. 
     Among the resetting routes R stored in the storage unit  150  of the ECU  14  according to the present embodiment, a resetting route R turning at a position closer to the target parking area F has a smaller turning radius. The selecting unit  147  selects the movement route closer to the target parking area F than the turning-back position A is. Consequently, the ECU  14  according to the present embodiment can prevent the vehicle  1  from passing over the frame lines and the like surrounding the target parking area F, thereby guiding the vehicle  1  to the target parking area F with higher accuracy. 
     When there are two or more resetting routes R that are selectable, the selecting unit  147  of the ECU  14  according to the present embodiment selects the resetting route R having a smaller absolute value of the difference between the vehicle inclination angle θA and the inclination angle θB of the resetting route R. As a result, the ECU  14  according to the present embodiment can select the resetting route R closer to the present position and direction of the vehicle  1 . Consequently, the ECU  14  can shift the vehicle  1  to the selected resetting route R more smoothly. 
     The route correcting unit  148  of the ECU  14  according to the present embodiment translates the resetting route R selected by the selecting unit  147  to the turning-back position A in the Y-direction. Consequently, the ECU  14  according to the present embodiment can perform parking support from the present position of the vehicle  1  without moving the vehicle  1  to shift it to the selected resetting route R. 
     Modifications 
     While the vehicle  1  according to the foregoing embodiment moves backward to enter into the target parking area F, it may move forward to enter into the target parking area F. 
     While the parking support performed by the ECU  14  according to the foregoing embodiment supports the vehicle  1  in entry to the parking area, the parking support is not limited thereto. The parking support performed by the ECU  14  may include supporting exit of the vehicle  1  from the parking area, for example. In this case, the target position P may be set on a road outside the parking area, for example. When the vehicle  1  turns back under the support of exit, the ECU  14  may carry out selection of the resetting route R. 
     While exemplary embodiments according to the present invention have been described, the embodiments and the modifications thereof are given by way of example only and are not intended to limit the scope of the invention. The embodiments and the modifications may be implemented in a variety of other forms. Various omissions, substitutions, combinations, and changes may be made without departing from the spirit of the invention. The configuration and the shape of the embodiments and the modifications may be implemented by being partially replaced.