Patent Publication Number: US-10319233-B2

Title: Parking support method and parking support device

Description:
TECHNICAL FIELD 
     The present invention relates to a parking assist method and a parking assist apparatus. 
     BACKGROUND 
     Heretofore, a parking space recognition apparatus has been known as below. The parking space recognition apparatus detects spaces into which a subject vehicle can spatially enter, prioritize the spaces on the basis of preregistered unique information of the subject vehicle and/or the driver, and outputs a candidate parking space (see Japanese Patent Application JP2009-205191A). 
     However, when attribute information of the subject vehicle or the unique information of the driver is not registered, an appropriate parking space cannot be presented to the driver and passengers. 
     A problem to be solved by the present invention is to provide a parking assist method or a parking assist apparatus with which an appropriate parking space can be presented to the driver and passengers. 
     SUMMARY 
     The present invention solves the above problem through setting a parking space suitable for parking of a subject vehicle among detected available parking spaces as a recommended available parking space in accordance with the traveling state of the subject vehicle, displaying the recommended available parking space on a display, setting the recommended available parking space displayed on the display as a target parking space for the subject vehicle on the basis of an operation by a driver or passenger, and performing automated control of the subject vehicle to park the subject vehicle into the target parking space. 
     The present invention has an effect that an appropriate available parking space can be presented to the driver and passengers because the recommended available parking space suitable for parking is displayed on the display while setting the recommended available parking space among the available parking spaces so that it matches estimation of the vehicle&#39;s behavior. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram illustrating an example of a parking assist system according to one or more embodiments of the present invention; 
         FIG. 2  is a flowchart illustrating an example of a control procedure in the parking assist system according to one or more embodiments of the present invention; 
         FIG. 3  is a view illustrating an example of positions at which on-board cameras are arranged according to one or more embodiments of the present invention; 
         FIG. 4A  is a first view for describing an example of a parking assist process according to an embodiment of the present invention; 
         FIG. 4B  is a second view for describing an example of the parking assist process according to the embodiment; 
         FIG. 4C  is a third view for describing an example of the parking assist process according to the embodiment; 
         FIG. 4D  is a fourth view for describing an example of the parking assist process according to the embodiment; 
         FIG. 4E  is a view for describing an example of the parking assist process according to the embodiment; 
         FIG. 4F  is a view for describing an example of the parking assist process according to the embodiment; 
         FIG. 5  is a graph illustrating the relationship between a vehicle speed (V [km]) and a gaze point distance (Y [m]); 
         FIGS. 6A-6C  are a set of views illustrating examples of parking patterns to which the parking assist process according to the embodiment is applied; 
         FIG. 7A  is a first view for describing an example of a display screen in the parking assist process according to the embodiment; 
         FIG. 7B  is a second view for describing an example of a display screen in the parking assist process according to the embodiment; 
         FIG. 7C  is a third view for describing an example of a display screen in the parking assist process according to the embodiment; 
         FIG. 7D  is a fourth view for describing an example of a display screen in the parking assist process according to the embodiment; 
         FIG. 7E  is a view for describing an example of a display screen in the parking assist process according to the embodiment; 
         FIGS. 8A and 8B  are a set of views for describing an example of a parking assist process according to another embodiment of the present invention; and 
         FIG. 9  is a graph illustrating the relationship between a vehicle speed (V [km]) and a gaze point distance (Y [m]). 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Hereinafter, embodiments of the present invention will be described with reference to the drawings. 
     First Embodiment 
     In this embodiment, the present invention will be described with reference to an example in which the parking assist apparatus according to the present invention is applied to a parking assist system equipped in a vehicle. The parking assist apparatus may also be applied to a portable terminal device (equipment such as smartphone and PDA) capable of exchanging information with onboard devices. The method of displaying parking assist information according to the present invention can be used in a parking assist apparatus. Parking assist information relating to the invention of the displaying method is specifically displayed using a display  21 . 
       FIG. 1  is a block diagram of a parking assist system  1000  having a parking assist apparatus  100  according to one or more embodiments of the present invention. The parking assist system  1000  according to the present embodiment assists an operation of moving (parking) a subject vehicle into a parking space. The parking assist system  1000  according to the present embodiment includes cameras  1   a  to  1   d , an image processing device  2 , a ranging device  3 , the parking assist apparatus  100 , a vehicle controller  30 , a drive system  40 , a steering angle sensor  50 , and a vehicle speed sensor  60 . The parking assist apparatus  100  according to the present embodiment includes a control device  10  and an output device  20 . The output device includes a display  21 , a speaker  22 , and a lamp  23 . These components are connected to one another via a controller area network (CAN) or other in-vehicle LAN to mutually exchange information. 
     The control device  10  of the parking assist apparatus  100  according to the present embodiment is a specific computer comprising a ROM  12  that stores a parking assist program, a CPU as an operation circuit that executes the program stored in the ROM  12  to serve as the parking assist apparatus  100  according to the present embodiment, and a RAM  13  that serves as an accessible storage device. 
     The parking assist program according to the present embodiment is a program for execution of a control procedure of presenting parking spaces, into which parking is possible, on the display  21  and assisting an operation to park the subject vehicle into a parking space set by a user. The parking assist apparatus  100  according to the present embodiment can be applied to automated parking in which all of the steering, accelerator, and brake are automatically operated thereby to park a vehicle automatically and can also be applied to semiautomated parking in which at least one operation of the steering, accelerator, and brake is manually performed and other operations are automatically performed for parking. In addition or alternatively, the parking assist apparatus  100  can be applied to a parking assist function with which a route to a parking space is presented to the user and the user operates the steering, accelerator, and brake to park the vehicle. 
     The control device  10  of the parking assist apparatus  100  according to the present embodiment has functions of executing an information acquisition process, an available parking space detection process, a recommended available parking space detection process, and a display control process. Each of the above processes is executed by cooperation of software for implementing the process and the above-described hardware. 
       FIG. 2  is a flowchart illustrating a control procedure of the parking assist process executed by the parking assist system  1000  according to the present embodiment. The trigger for starting the parking assist process is not particularly limited, and the parking assist process may be triggered by the operation of a start switch of the parking assist apparatus  100 . 
     The parking assist apparatus  100  according to the present embodiment has a function for automatically moving the subject vehicle to the parking space. In this process according to the present embodiment, a momentary-type switch such as a deadman switch is used. In the parking assist apparatus  100 , the automated driving of the subject vehicle is executed when the deadman switch is pressed and the automated driving of the subject vehicle is suspended when the pressing of the deadman switch is released. 
     Specifically, in step  101 , the control device  10  of the parking assist apparatus  100  according to the present embodiment acquires images captured by the cameras  1   a  to  1   d  attached to multiple sites of the subject vehicle. The cameras  1   a  to  1   d  capture images of boundary lines of parking spaces around the subject vehicle and objects existing around the parking spaces. The cameras  1   a  to  1   d  may be CCD cameras, infrared cameras, or other appropriate imaging devices. The ranging device  3  may be provided at the same position as any of the cameras  1   a  to  1   d  or may also be provided at a different position. The ranging device  3  may be a radar device, such as a millimeter-wave radar, laser radar and ultrasonic radar, or a sonar. The ranging device  3  detects the presence or absence of objects, positions of the objects, and distances to the objects on the basis of the received signal of the radar device. Such objects correspond to obstacles, pedestrian, and other vehicles around the vehicle. The received signal is used to determine whether or not the parking space is empty (whether or not a vehicle is parked in the parking space). Obstacles may be detected using the motion stereo technique by the cameras  1   a  to  1   d.    
       FIG. 3  is a view illustrating an exemplary arrangement of the cameras  1   a  to  1   d  disposed on the subject vehicle. In the example illustrated in  FIG. 3 , the camera  1   a  is disposed on the front grille part of the subject vehicle, the camera  1   d  is disposed in the vicinity of the rear bumper, and the cameras  1   b  and  1   c  are disposed on the lower parts of the right and left door mirrors. The cameras  1   a  to  1   d  may each be a camera having a wide-angle lens with a wide view angle. 
     In step  101 , the control device  10  also acquires ranging signals from the ranging device  3 , which may be a plurality of modules attached to multiple sites of the subject vehicle. 
     In step  102 , the control device  10  of the parking assist apparatus  100  controls the image processing device  2  to generate an overhead image. On the basis of the acquired plurality of captured images, the image processing device  2  generates an overhead image in which the surrounding state including the subject vehicle and the parking space for the subject vehicle to park is viewed from a virtual viewpoint P (see  FIG. 3 ) above the subject vehicle. The image processing performed by the image processing device  2  may be conducted, for example, using a method as disclosed in “Development of Around View System, Proceedings of Society of JSAE Annual Congress, 116-07 (October 2007), pp. 17-22, SUZUKI Masayasu, CHINOMI Satoshi, TAKANO Teruhisa.” Examples of a generated overhead image  21 A are illustrated in  FIGS. 7A and 7B , which will be described later. These figures each illustrate a display example that simultaneously displays the overhead image (top view)  21 A around the subject vehicle and a monitoring image (normal view)  21 B around the subject vehicle. 
     In step  103 , available parking spaces Me are detected. The control device  10  detects the available parking spaces Me on the basis of the images captured by the cameras  1   a  to  1   d  and/or the data received by the ranging device  3 . The control device  10  stores a “parking possible condition” for extracting the available parking spaces Me. The “parking possible condition” is defined from the viewpoint of extracting a parking space into which parking is possible. The “parking possible condition” is preferably defined from the viewpoint of the distance from the subject vehicle, the viewpoint as to whether or not other vehicles are parked, and the viewpoint of presence or absence of obstacles. On the basis of the “parking possible condition,” the control device  10  detects the available parking spaces Me into which the subject vehicle can be parked. The available parking spaces Me are parking spaces into which the subject vehicle can be parked. The control device  10  detects the available parking spaces Me on the basis of the images captured by the cameras  1   a  to  1   d  and/or the data received by the ranging device  3 . In the above description, images of available parking spaces are captured by the on-board cameras and the available parking spaces Me are detected from the captured images, but information may be acquired from an external server and the available parking spaces may be specified from the acquired information. 
     A method of detecting the available parking spaces Me will be described below. The control device  10  determines whether or not the subject vehicle is traveling in an area that includes parking spaces (such an area will also be referred to as a “parking area,” hereinafter), on the basis of the vehicle speed or positional information from a navigation system (not illustrated). For example, when the vehicle speed of the subject vehicle is a predetermined vehicle speed threshold or less and this state continues for a predetermined time or more, the control device  10  determines that the subject vehicle is traveling in a parking area. In addition or alternatively, when the detected positional information has an attribute that represents a parking area such as an area including parking spaces of a highway, for example, the control device  10  determines that the subject vehicle is traveling in the parking area. In the present embodiment, a determination may be made as to whether or not the detected area is an area including available parking spaces, via communication with the outside of the vehicle, that is, via so-called road-to-vehicle communication or vehicle-to-vehicle communication. 
     When a determination is made that the subject vehicle is traveling in a parking area, the control device  10  detects white lines on the basis of the captured images acquired for generation of an overhead image. White lines represent boundary lines that define frames (regions) of parking spaces. The control device  10  performs edge detection on the captured images to calculate a luminance difference (contrast). The control device  10  specifies a pixel line having a luminance difference of a predetermined value or more from the overhead image and calculates the width and length of the line. The control device  10  also detects whether or not there are candidates of parking frame lines that have a higher possibility of being lines of parking frames than the specified line, around the portion in which the line is specified. For example, when a line having a larger luminance difference is newly specified, the newly specified line is detected as a line having a higher possibility of representing a parking frame line. In the present embodiment, frame lines representing parking spaces are not necessarily white, and other colors such as red may also be employed. 
     The ROM  12  of the control device  10  preliminarily stores information on the patterns of parking frames. The patterns of parking frames represent various shapes of parking spaces. For example, in the parking spaces of  FIG. 6A  which will be described later, the pattern of a parking frame is composed of three sides among the sides which form a rectangle. Examples of parking frame patterns include those for parallel parking as illustrated in  FIG. 6B , which will be described later, and those for oblique-parking as illustrated in  FIG. 6C , which will also be described later. 
     The control device  10  specifies lines located on the road surface from the overview image as candidates of parking frame lines using a known image processing technique such as pattern matching. When the specified candidates of parking frame lines satisfy all of the following three conditions (1) to (3), the control device  10  specifies the specified parking frame lines as those representing parking spaces. The following conditions are merely examples. 
     (1) Lines extracted as candidates of parking frame lines do not include a line having a length equal to or larger than a first line length threshold that is preliminarily set (e.g. a length corresponding to an actual distance of 15 [m]). 
     (2) Among lines extracted as candidates of parking frame lines, a set of adjacent two lines within a first line spacing range that is preliminarily set (e.g. a length corresponding to an actual distance of 3 to 5 [m]) does not include a set of lines having a length equal to or smaller than a second line length threshold that is preliminarily set (e.g. a length corresponding to an actual distance of 7 [m]). 
     (3) Among lines extracted as candidates of parking frame lines, a set of adjacent two lines within a second line spacing range that is preliminarily set (e.g. a length corresponding to an actual distance of 2.5 to 5 [m]) does not include a set of lines having a length equal to or smaller than a third line length threshold that is preliminarily set (e.g. a length corresponding to an actual distance of 15 [m]). 
     In case of specifying parking spaces that satisfy the above three conditions, the control device  10  determines whether or not obstacles are present in the specified parking spaces using the detection data from the ranging device  3 . In addition, the control device  10  determines whether or not the specified parking spaces are those into which parking is possible by automated driving, on the basis of a travel route in the automated driving. For example, parking spaces for which a travel route in the automated driving cannot be ensured, such as parking spaces facing a wall, do not correspond to parking spaces into which parking is possible by the automated driving. Then, the control device  10  detects parking spaces, from among the specified parking spaces, in which obstacles do not exist and into which parking is possible by the automated driving, as the available parking spaces Me. Thus, the control device  10  detects the available parking spaces Me. In the above description, the control device  10  detects the available parking spaces while detecting parking frame lines, but the parking frame lines may not necessarily be detected to detect the available parking spaces. In addition or alternatively, the control device  10  may detect empty spaces having a certain range and detect the empty spaces as the available parking spaces and may also detect the available parking spaces using information about past results of parking. In addition or alternatively, when parking spaces satisfy a predetermined condition, the control device  10  may detect the parking spaces satisfying the predetermined condition as the available parking spaces. 
       FIG. 4A  is a first view for describing an example of the parking assist process according to the present embodiment. It is assumed that, in  FIG. 4A , the position of the subject vehicle traveling is P 1  and the vehicle speed is V 1 . Arrows L represent a travel route when the vehicle is parked by automated driving. Dotted circles represent the available parking spaces Me detected at the position P 1 . 
     In  FIG. 4A  and in  FIGS. 4B to 4D  which will be described later, the movement of the subject vehicle is represented in a temporal sequence, and the position of the subject vehicle moves from  FIG. 4A  in the order of  FIG. 4B ,  FIG. 4C , and  FIG. 4D .  FIG. 4E , which will be described later, is not continuous with  FIGS. 4A to 4D  in the temporal sequence. 
     The travel route L is a route on which the subject vehicle moves from the current position G 1  to an intermediate position Mw located ahead of the subject vehicle and reverses to complete the parking maneuver into an available parking space PL. Such parking maneuver includes one or more turns for parking. In  FIG. 4A , an obstacle M 1  exists on the parking space PR 8 , and the control device  10  therefore does not detect the parking space PR 8  as an available parking space Me. With regard to the parking space PL 8 , a travel route cannot be ensured in the automated driving because a wall Wa interferes with the travel route (corresponding to dotted arrows in  FIG. 4A ), and the parking space PL 8  is therefore not a parking space suitable for the automated driving. Accordingly, the control device  10  does not detect the parking space PR  8  as an available parking space Me. Other vehicles are parked in the parking spaces PR 1 , PR 4 , PR 6 , and PL 3 , and the control device  10  therefore does not detect them as available parking spaces Me. The control device  10  detects the parking spaces PL 1 , PL 2 , PL 4  to PL 7 , PR 2 , PR 3 , PR 5 , and PR 7  as available parking spaces Me. 
     The control apparatus  10  sets a range that includes the parking spaces PL 2  to PL 5  and PR 2  to PR 5 , among the parking spaces included in the images captured at the position P 1  of the subject vehicle, as the detection range for available parking spaces Me. The detection range for available parking spaces Me during the vehicle&#39;s travel is not limited to the range of parking spaces PL 2  to PL 5  and PR 2  to PR 5 , and may also be the range of parking spaces PL 1  to PL 8  and PR 1  to PR 8 , for example. 
     Referring again to  FIG. 2 , in step  104 , a recommended available parking space Mr is detected. The recommended available parking space Mr is an available parking space suitable for parking the subject vehicle. The control device  10  detects the recommended available parking space Mr in accordance with the traveling state of the subject vehicle from among the detected plurality of available parking spaces. The control device  10  stores the “parking recommendation condition” for extracting the recommended available parking space Mr. The “parking recommendation condition” is defined from the viewpoint of extracting a parking space with which a parking-related cost required for parking is low. The “parking recommendation condition” is preferably defined from the viewpoint of a time required for parking (required time for parking). On the basis of the “parking recommendation condition,” the control device  10  extracts the recommended available parking space Mr, with which the parking-related cost is low, from among the available parking spaces. 
     A method of detecting the recommended available parking space Mr will be described below. The control device  10  evaluates the parking-related cost required for parking into each available parking space. The travel route used for evaluation of the cost is a route from the start position at which the parking assist process (automated driving) is started to the position of each available parking space Me. The control device  10  calculates the travel route when parking the subject vehicle into each available parking space Me. The control device  10  sets the start position for each available parking space Me. The control device  10  calculates a travel route from the start position to each available parking space Me. The number of travel routes for the automated driving is not limited to one, and the control device  10  may calculate a plurality of travel routes in accordance with the surrounding situations. 
     The parking-related cost for parking into each available parking space Me reflects a load such as the required time for parking which is required for moving the subject vehicle to the parking space by the automated driving. 
     The parking-related cost reflects a travel time for the subject vehicle to be parked into an available parking space Me by the automated driving and is obtained in accordance with the required time for parking. The required time for parking is a time when traveling by the automated driving along the travel route calculated for each available parking space Me. The parking-related cost may be obtained in accordance with the ease of entry into an available parking space Me. The ease of entry into an available parking space Me is determined in accordance with the travel distance, the number of operations (the number of turns for parking), the maximum steering angle, the vehicle speed, etc. For example, when the travel distance is long, when the number of turns for parking is large, when the maximum steering angle is large, and/or when the vehicle speed is high, it is not easy to enter an available parking space Me, and the parking-related cost is high. In other words, the ease of entry is evaluated for each available parking space, and on the assumption that an available parking space into which entry is easiest is the available parking space with which the parking-related cost is smallest, the available parking space may be set as the recommended available parking space. Factors of the parking-related cost may include not only the required time for parking but also other factors such as the certainty of parking in the automated driving. The parking-related cost may not necessarily be an index equivalent to the required time for parking and may also be calculated from the relative relationship with the number of turns for parking on a travel route, the length of a travel route, or the maximum steering angle. The parking-related cost may be calculated on the basis of each index, such as the required time for parking, the ease of entry into an available parking space Me, and the certainty of parking, or on the basis of a combination of two or more indices, or on the basis of a combination of all the indices. 
     In the following description of the present embodiment, the parking-related cost is calculated on the basis of the required time for parking. The travel route is different for each available parking space Me in accordance with the number of turns for parking, the travel distance, the maximum steering angle, etc. When the vehicle travels along a travel route by the automated driving, therefore, the required time for parking is different for each travel route. For example, the required time for parking will be shorter as the number of turns for parking is smaller, as the distance of a travel route is shorter, or as the maximum steering angle is smaller. As illustrated in  FIG. 4A , on the assumption of parking into the available parking space PL 6  or PL 7 , the distance from the vicinity of the parking space PL 7  to the wall Wa is shorter than the distance from the vicinity of the parking space PL 6  to the wall Wa. The number of turns for parking when parking into the parking space PL 7  is therefore larger than the number of turns for parking when parking into the parking space PL 6 , and the required time for parking into the parking space PL 7  is longer than the required time for parking into the parking space PL 6  (the parking-related cost is higher in the former case). 
     The control device  10  then calculates a gaze point distance on the basis of the vehicle speed of the subject vehicle. The gaze point distance refers to a distance from the position of the subject vehicle to the position which the driver of the subject vehicle gazes on. In general, the higher the vehicle speed, the farther the driver gazes on, and the lower the vehicle speed, the closer the driver gazes on. From the viewpoint of recommending an available parking space in accordance with the observing point of the driver, the control device  10  sets a longer gaze point distance as the vehicle speed of the subject vehicle is higher, and sets a shorter gaze point distance as the vehicle speed of the subject vehicle is lower. This allows the parking assist into the available parking space to be executed in accordance with the intention of the driver. The gaze point distance does not have to be linear and may also be defined along a curve. When the gaze point distance is defined along a curve, the curvature of the curve may be associated with the steering angle. 
       FIG. 5  is a graph illustrating the relationship between the vehicle speed (V [km/s]) and the gaze point distance (Y [m]). The solid line represents a characteristic when the vehicle speed increases while the broken line represents a characteristic when the vehicle speed decreases. As illustrated in  FIG. 5 , when the vehicle speed is Va or lower, the gaze point distance is Ya. When the vehicle speed increases from Va to Vc, the gaze point distance maintains Ya. Then, as the vehicle speed increases from the state of Vc, the gaze point distance increases in proportion to the vehicle speed within a range of Vc or higher and Vd or lower of the vehicle speed. When the vehicle speed is Vd or higher, the gaze point distance maintains Yb. On the other hand, when the vehicle speed lowers from the state of Vd, the gaze point distance maintains Yb until the vehicle speed returns to Vb from Vd. The gaze point distance decreases in proportion to the vehicle speed within a range of Va or higher and Vc or lower of the vehicle speed. Thus, the relationship between the vehicle speed and the gaze point distance has a hysteresis characteristic between the increasing direction and decreasing direction of the vehicle speed. 
     The ROM  12  of the control device  10  stores the relationship between the vehicle speed and the gaze point distance as a map. When acquiring the information on the vehicle speed from the vehicle speed sensor  60 , the control device  10  refers to the map to calculate the gaze point distance corresponding to the vehicle speed. 
       FIG. 4B  illustrates a state in which the subject vehicle moves forward from the position P 1  illustrated in  FIG. 4A  to a position P 2 . The speed of the subject vehicle at the position P 2  is V 2  (&lt;V 1 ). The control device  10  refers to the map to calculate the gaze point distance corresponding to the vehicle speed V 2 . The control device  10  specifies a point G 2  that is separate from the position P 2  by the gaze point distance, as a gaze point (G 2 ). The subject vehicle is in a state of selecting an available parking space with the lowered vehicle speed V 2  (&lt;V 1 ). The distance between the gaze point G 2  and the subject vehicle is shorter than the distance between the gaze point G 1  illustrated in  FIG. 4A  and the subject vehicle because the vehicle speed is lowered. 
     In the state illustrated in  FIG. 4B , the control device  10  detects a recommended available parking space from among the available parking spaces PL 2 , PL 4 , PL 5 , PR 2 , PR 3 , and PR 5  in the vicinity of the gaze point G 2 . The control device  10  detects the recommended available parking space on the basis of the parking-related cost for each of the parking spaces PL 2 , PL 4 , PL 5 , PR 2 , PR 3 , and PR 5 . 
     The control device  10  then assigns numbers for identification to the available parking spaces Me in the vicinity of the gaze point G 2 . For example, the identification numbers are given in the order of proximity to the gaze point G 2 . The control device  10  calculates the parking-related cost for parking into each available parking space Me (the parking-related cost represents an index of the ease of entry into each available parking space Me). The control device  10  may read out the parking-related cost for parking which is previously calculated. 
     To evaluate the parking-related cost, the control device  10  calculates the required time for parking into each available parking space Me. In the example of  FIG. 4B , the control device  10  calculates the parking-related cost (required time for parking) for each of the available parking spaces PL 2 , PL 4 , PL 5 , PR 2 , PR 3 , and PR 5  and stores the parking-related cost such that it is associated with each identification number. 
     The control device  10  compares the required time for parking into each available parking space Me with a predetermined required time threshold. The required time threshold is a value that is preliminarily set and an upper limit of the required time when parking by the automated driving. When the required time for parking into an available parking space Me is longer than the required time threshold, the control device  10  does not detect the available parking space Me as the recommended available parking space Mr. 
     After detecting the available parking spaces Me with which the required time for parking is shorter than the required time threshold, the control device  10  sets an available parking space Me that is closest to the gaze point among the detected available parking spaces Me as the recommended available parking space Mr. In the example of  FIG. 4B , the required time for parking into the parking space PL 4  is shorter than the required time threshold, and the parking space PL 4  is located closest to the gaze point. The control device  10  therefore sets the parking space PL 4  as the recommended available parking space Mr. In the above-described embodiment, among the available parking spaces Me with which the required time for parking is shorter than the required time threshold, the available parking space with the shortest gaze point distance is set as the recommended available parking space Mr, but another method may be employed to set the recommended available parking space Mr. For example, among the available parking spaces Me with which the required time for parking is shorter than the required time threshold, an available parking space Me with which the required time for parking is shortest may be set as the recommended available parking space Mr. In another embodiment, for example, it is assumed that, in the detection of the recommended available parking space Mr, available parking spaces Me can be set as the recommended available parking space Mr when the gaze point distance from the gaze point to the available parking space Me is within a predetermined distance. From among such available parking spaces Me, an available parking space with which the required time for parking is shortest may be detected as the recommended available parking space Mr. 
     As described above, in the present embodiment, the gaze point distance is calculated on the basis of the vehicle speed, and a position separate from the current position of the subject vehicle by the gaze point distance is specified as the gaze point. Further, among the available parking spaces, an available parking space closest to the gaze point is set as the recommended available parking space Mr. That is, the gaze point distance based on the vehicle speed is calculated to specify the gaze point of the user, thereby specifying the recommended available parking space with consideration for the intention of the user (driving operation by the user). In the present embodiment, the parking-related cost is calculated for each available parking space, and among the available parking spaces, an available parking space with which the parking-related cost is low is set as the recommended available parking space Mr. That is, cost evaluation is employed to determine the state of the vehicle in the automated driving before the automated driving is executed, and the recommended available parking space is specified. Through this operation, in the present embodiment, an available parking space suitable for parking the subject vehicle is set as the recommended available parking space in accordance with the traveling state of the subject vehicle. 
     The control device  10  executes the detection process for the recommended available parking space Mr at a predetermined period. As illustrated in  FIG. 4C , also when the subject vehicle moves forward to the position P 3  at a vehicle speed of V 3 , the control device  10  detects a new recommended available parking space Mr. The control device  10  calculates a new gaze point G 3  and the parking-related cost required for moving from the current position to each available parking space Me and detects the parking space PL 5 , with which the parking-related cost is lowest, as the recommended available parking space Mr. 
     In step  105 , the available parking spaces Me and the recommended available parking space Mr are presented. The control device  10  controls the display  21  to display the set available parking spaces Me and the set recommended available parking space Mr thereby to present them to the driver and passengers. The display form on the display  21  will be described later. 
     In step  106 , a determination is made as to whether or not a target parking space Mo is input. The target parking space Mo is a parking space into which the vehicle is parked by the automated driving, and represents a location to be the target in the automated driving. The target parking space Mo is set on the basis of the operation by the driver or a passenger. For example, when the display  21  is a touch panel-type display, the driver or a passenger touches a portion representing a desired parking space thereby to designate the target parking space Mo, and information on the target parking space Mo is input to the control device  10 . 
     When the target parking space Mo is input, the control flow proceeds to step  107 . On the other hand, when the target parking space Mo is not input, the control flow returns to step  104 , and the control flow from step  104  to step  106  is repeatedly executed. 
     When the target parking space Mo is input, this parking space is set as the target parking space Mo in step S 107 . 
     In step  108 , the control device  10  calculates a travel route for moving the subject vehicle to the target parking space Mo. 
       FIG. 4D  is a view illustrating a scene in which the available parking space PL 5  is designated as the target parking space Mo. The control device  10  calculates a travel route for parking on the basis of the positional relationship between the position P 4  of the subject vehicle at which the parking maneuver (movement) is started (automated parking start position) and the position of the target parking space Mo. Although not particularly limited, the control device  10  calculates the travel route to include two curves. The first curve lies from the stop position of the subject vehicle, that is, the start position (P 4 ) at which the parking assist is started, to the turning position Mw at which the turn for parking is performed. The second curve lies from the turning position Mw to the target parking space Mo (PL 5 ). 
     The control device  10  reads travel routes corresponding to the selected parking mode and calculates a travel route on the basis of the positional relationship between the position of the subject vehicle when starting the automated parking process and the position of the target parking space Mo. When the user presses the previously-described deadman switch during the operation of the automated parking mode, the control device  10  controls the vehicle controller  30  to execute the process of moving the subject vehicle to the target parking space Mo on the calculated travel route. 
     The control device  10  calculates the travel route corresponding to each of right-angle parking, parallel parking, and oblique parking illustrated in  FIGS. 6A-6C , respectively. In the present embodiment, the travel route has been described as being calculated, but the present invention is not limited to this. In an alternative embodiment, a travel route corresponding to the type of the parking space is stored in a memory (ROM), and the travel route may be read out when parking. The parking mode (such as right-angle parking, parallel parking, and oblique parking) may be selected by the driver of the subject vehicle. 
     In step  109 , the parking assist apparatus  100  according to the present embodiment executes the parking assist process or the automated parking process. The parking assist apparatus  100  according to the present embodiment controls the operation of the drive system  40  via the vehicle controller  30  so that the subject vehicle moves along the travel route. 
     The parking assist apparatus  100  according to the present embodiment includes a parking assist control unit. The parking assist control unit acquires shift range information from an AT/CVT control unit, wheel speed information from an ABS control unit, steering angle information from a steering angle control unit, engine speed information from an ECM, and other necessary information. On the basis thereof, the parking assist control unit calculates and outputs instruction information on the automated steering to the EPS control unit, instruction information such as warning to a meter control unit, etc. The control device  10  acquires information items, which are acquired by the steering angle sensor  50  of the steering apparatus of the vehicle and the vehicle speed sensor  60  and other sensors of the vehicle, via the vehicle controller  30 . 
     The drive system  40  according to the present embodiment allows the subject vehicle to be parked into the target parking space Mo by driving based on the control command signals acquired from the parking assist apparatus  100 . The steering apparatus according to the present embodiment is a drive mechanism that moves the subject vehicle in the right and left directions. The EPS motor included in the drive system  40  drives the power steering mechanism of the steering of the steering apparatus on the basis of the control command signals acquired from the parking assist apparatus  100  to control the steering amount and assists the operation when moving the subject vehicle to the target parking space Mo. The content of the parking assist and the scheme of operation are not particularly limited, and schemes known at the time of filing of this application can be appropriately applied. 
     When the parking assist apparatus  100  according to the present embodiment controls the subject vehicle to move to the target parking space Mo along the travel route calculated based on the position P 4  of the subject vehicle and the position of the target parking space Mo, the operation of the accelerator/brake is automatically controlled on the basis of the designated control vehicle speed (set vehicle speed), and the operation of the steering apparatus is also automatically controlled in accordance with the vehicle speed. The parking assist apparatus  100  calculates command signals to the drive system  40  of the subject vehicle, such as an EPS motor, while feeding back the output value of the steering angle sensor  50  of the steering apparatus so that the travel trajectory of the subject vehicle coincides with the calculated travel route, and sends the command signals to the drive system  40  or to the vehicle controller  30  which controls the drive system  40 . That is, during the parking assist according to the present embodiment, the steering operation and the accelerator/brake operation are automatically performed. It is also possible to perform a parking process by remote control that includes transmitting a setting command for the target parking space Mo, a parking process start command, a parking suspension command, etc. to the vehicle with no driver therein from the outside and performing the parking. 
     As will be understood, it is also possible for the driver to operate the accelerator/brake, and only the operation of the steering apparatus is automated. In this case, the parking assist apparatus  100  controls the drive system  40  on the basis of the set vehicle speed which is preliminarily calculated so that the subject vehicle follows the travel route to move, and controls the steering apparatus of the vehicle on the basis of the set steering angle which is also preliminarily calculated. 
     A method of presenting parking assist information in the parking assist apparatus  100  according to the present embodiment will be described below. 
       FIG. 7A  is a first view for describing an example of a display screen in the parking assist process according to the present embodiment.  FIG. 7B  is a second view for describing an example of a display screen in the parking assist process according to the present embodiment.  FIG. 7A  illustrates a display screen when the subject vehicle is traveling at the position P 2  of  FIG. 4B .  FIG. 7B  illustrates a display screen when the subject vehicle is traveling at the position P 3  of  FIG. 4C .  FIGS. 7A and 7B  represent the parking assist information displayed when searching for a parking space into which the subject vehicle is parked. What are illustrated in  FIGS. 7A and 7B  are situations in which the subject vehicle searches for a parking space into which the subject vehicle is parked, while moving along the arrows. 
     In the display screen of  FIG. 7A , an image (of boundary lines of parking spaces) that indicates the parking spaces PL 2  to PL 5  and PR 2  to PR 5  is displayed on the left-side overhead image (top view)  21 A on the screen of the display  21 . In the display screen of  FIG. 7B , an image (of boundary lines of parking spaces) that indicates the parking spaces PL 3  to PL 6  and PR 3  to PR 6  is displayed on the left-side overhead image (top view)  21 A on the screen of the display  21 . The center of the overhead image (top view)  21 A is displayed with an icon of the subject vehicle indicating the position of the subject vehicle. The monitoring image (normal view) can be displayed as any of images captured by different cameras  1   a  to  1   d  in accordance with the operation state of the subject vehicle. Examples illustrated in  FIGS. 7A and 7B  are each displayed as an image captured by the camera  1   a  which is disposed on the front grill part of the subject vehicle. When the subject vehicle moves back, the monitoring image may be displayed as an image captured by the camera  1   d  which is disposed in the vicinity of the rear bumper. The image  21 C is an image for messages. In these examples, the overhead image  21 A and the monitoring image  21 B are simultaneously displayed on the display  21 , but only the overhead image  21 A may be displayed on the display  21 , or only the monitoring image  21 B may be displayed on the display  21 . 
     The overhead image  21 A is displayed with the available parking spaces Me and the recommended available parking space Mr. In a scene in which the subject vehicle searches for a target parking space while moving in the parking lot, the available parking spaces Me and the recommended available parking space Mr change as the subject vehicle moves. The parking assist apparatus  100  displays the available parking spaces Me and the recommended available parking space Mr which are sequentially detected. The parking assist apparatus  100  displays the available parking spaces Me with parking available marks in a circular shape and displays the recommended available parking space Mr with a recommendation mark in a rectangular shape. 
     As illustrated in  FIGS. 7A and 7B , when the subject vehicle is moving, the available parking spaces Me and the recommended available parking space Mr sequentially change as the subject vehicle moves. When an available parking space Me or recommended available parking space Mr changes, the parking assist apparatus  100  changes the position of the parking available mark or recommendation mark and displays it. 
     Here, a display form of the recommended available parking space Mr when the subject vehicle moves while decelerating will be described. As described above, the control device  10  sets the recommended available parking space Mr for the available parking space Me which is closest to the gaze point. The gaze point distance varies in accordance with the vehicle speed of the subject vehicle. 
     The description will be made for a case in which the characteristic of the gaze point distance when the vehicle speed increases and the characteristic of the gaze point distance when the vehicle speed decreases follow the characteristic illustrated by the solid line of  FIG. 5  rather than the hysteresis characteristic as illustrated in  FIG. 5 . It is assumed that, in the example of  FIG. 4B , the recommended available parking space Mr set when the vehicle speed is Vd is the available parking space PL 5 . In such a case, as the vehicle speed becomes lower than Vd from the state of Vd, the gaze point distance becomes shorter than Yb, and the recommended available parking space Mr changes from the available parking space PL 5  to another available parking space PL 4 . That is, despite the fact that the subject vehicle travels toward the recommended available parking space Mr (PL 5 ) which is set before deceleration, the screen of the display  21  shows a movement such that the frame of the recommended available parking space Mr returns below on the screen (in the direction opposite to the travel direction of the subject vehicle, i.e. in the negative direction of the y-axis of  FIG. 7A ). To prevent such unnatural movement of the recommended available parking space Mr, in the present embodiment, hysteresis is given to the characteristic of the gaze point distance with respect to the vehicle speed. 
     With the hysteresis characteristic, the gaze point distance is maintained at Yb when the vehicle speed becomes lower than Vd from the state of Vd. The recommended available parking space Mr therefore remains at the position of the available parking space PL 5  or moves to the available parking space PL 6  on the travel direction side of the vehicle from the position of the available parking space PL 5 . That is, among a first available parking space (corresponding to the available parking space PL 5  of  FIG. 4A ) and a second available parking space (corresponding to the available parking space PL 4  of  FIG. 4A ) that are disposed side by side along a direction parallel to the travel direction of the subject vehicle (the y-axis direction of  FIG. 7A ), the first available parking space farther from the subject vehicle than the second available parking space is set as the recommended available parking space by the control device  10 . Then, in the state in which the vehicle speed of the subject vehicle decreases, the control device  10  prohibits the recommended available parking space (corresponding to the available parking space PL 5  of  FIG. 4A ) from moving from the first available parking space to the second available parking space (corresponding to the available parking space PL 4  of  FIG. 4A ) on the display screen of the display  21 . This can prevent the unnatural movement of the recommended available parking space Mr. 
     Next, in a display form of the recommended available parking space Mr, hunting in the lateral direction (the positive and negative directions of the x-axis of  FIG. 7A ) and control for preventing such hunting will be described. 
       FIGS. 4E and 4F  are views for describing an example of the parking assist process according to the present embodiment. As described above, the recommended available parking space Mr changes its position on the display screen of the display  21  in accordance with the position of the vehicle. For example, in the parking area illustrated in  FIG. 4E , it is assumed that the subject vehicle is traveling between a row of parking spaces on the left side and a row of parking spaces on the right side (the vicinity of the center in the lateral direction is indicated by a dashed-two dotted line). It is also assumed that, as illustrated in  FIG. 4E , a number of parking spaces are empty in the parking area. When the subject vehicle is traveling on the left side of the center line indicated by the dashed-two dotted line, the position of the gaze point is located on the left side of the center line. On the other hand, when the subject vehicle is traveling on the right side of the center line indicated by the dashed-two dotted line, the position of the gaze point is located on the right side of the center line. Accordingly, when the subject vehicle travels in the vicinity of the center in the lateral direction with respect to the direction in which the parking spaces are arranged, the position of the subject vehicle may swing laterally across the center line, and the position of the gaze point will also swing laterally. If the available parking space Me closest to the gaze point is set as the recommended available parking space Mr, the displayed frame of the recommended available parking space Mr will frequently move right and left. In the present embodiment, control is executed as below to prevent such hunting of the recommended available parking space Mr. 
     The control device  10  sets a fixed display mode for fixing the display region for the recommended available parking space Mr in accordance with the number of the available parking spaces Me. In the fixed display mode, the region in which the recommended available parking space Mr can be set is fixed to any of the left side and the right side. The control device  10  compares the number of the available parking spaces Me with a predetermined value. When the number of the available parking spaces Me is not smaller than the predetermined value, the control device  10  sets the display mode to the fixed display mode. 
     When the fixed display mode is set, the control device  10  selects one of right and left regions as a settable region for the recommended available parking space Mr in accordance with the traveling state of the subject vehicle. When the settable region is set, the control device  10  sets the recommended available parking space among the available parking spaces included in the settable region. The control device  10  calculates the distances from the parking spaces located on the sides of the subject vehicle to the subject vehicle as lateral distances (XL, XR). In the examples of  FIGS. 4E and 4F , XL represents the lateral distance on the left side and XR represents the lateral distance on the right side. The control device  10  compares XL with XR. When XL is shorter than XR, the control device  10  sets the region on the left side as the settable region for the recommended available parking space Mr. When XR is shorter than XL, the control device  10  sets the region on the right side as the settable region for the recommended available parking space Mr. 
     After setting the settable region for the recommended available parking space Mr to the right or left, the control device  10  adds a length XHIS to a length (W/2). The length (W/2) is a length obtained by halving the length of the lateral distance between the left-side parking spaces and the right-side parking spaces. The length XHIS is a length that defines a bias. When the left-side region is set as the settable region for the recommended available parking space Mr, the control device  10  compares the left-side lateral distance XL with a length (XHIS+W/2) to which the bias XHIS is added. When the left-side lateral distance XL is longer than the length (XHIS+W/2), the control device  10  changes the settable region for the recommended available parking space Mr from the left-side region to the right-side region. When the left-side lateral distance XL is not longer than the length (XHIS+W/2), the control device  10  maintains the state in which the left-side region is set as the settable region for the recommended available parking space Mr. 
     As illustrated in  FIG. 4E , after the settable region for the recommended available parking space Mr is set to the left side, when the left-side lateral distance XL is not longer than the length (XHIS+W/2), the control device  10  maintains the state in which the settable region for the recommended available parking space Mr is set at the left side. On the other hand, as illustrated in  FIG. 4F , after the settable region for the recommended available parking space Mr is set to the left side, when the subject vehicle travels on the right side of the center line and the left-side lateral distance XL is longer than the length (XHIS+W/2), the control device  10  changes the settable region for the recommended available parking space Mr from the left-side region to the right-side region. Through this operation, selection between the right side and the left side when set as the settable region can have a hysteresis characteristic with respect to the lateral position of the subject vehicle. For example, when the left-side region is set as the settable region for the recommended available parking space Mr, the recommended available parking space Mr is preferentially displayed on the left-side region as compared with the right side. This makes it possible to suppress the occurrence of hunting of the recommended available parking space Mr on the display screen of the display  21 . In the above description, the left-side region is set as the settable region for the recommended available parking space Mr and the settable region for the recommended available parking space Mr is changed in accordance with the comparison result between the lateral distance (XL) of the subject vehicle and the length (XHIS+W/2), but when the right-side region is set as the settable region for the recommended available parking space Mr, the settable region for the recommended available parking space Mr may be changed in accordance with the comparison result between the lateral distance (XR) of the subject vehicle and the length (XHIS+W/2). 
     When the number of the available parking spaces Me is less than the predetermined value, the control device  10  sets the display mode to a normal mode. In the normal mode, no settable region is set. When the parking area includes few empty parking spaces, prompt presentation of the empty parking spaces to the driver and passengers may be more important than preventing the hunting. Thus, the convenience of the system for the driver and passengers can be improved. 
     When the subject vehicle stops from the state of moving as illustrated in  FIGS. 7A and 7B , the display screen of the display  21  becomes a screen as illustrated in  FIG. 7C .  FIG. 7C  is a third view for describing an example of a display screen in the parking assist process according to the present embodiment. The display screen of  FIG. 7C  is a display screen when the vehicle stops at the position P 3  in  FIG. 4C . 
     As illustrated in the display screen of  FIG. 7C , the user finds the messages included in the image  21 C and can confirm that selection and input of the target parking space Mo are required. The user designates the available parking space PL 5 , which is presented as the recommended available parking space Mr, as the target parking space Mo. The user touches the available parking space PL 5 , which is displayed on the touch panel-type display  21 , thereby to designate this available parking space as the target parking space Mo. The display screen of the display is changed from the display screen of  FIG. 7C  to the display screen of  FIG. 7D . 
       FIG. 7D  is a fourth view for describing an example of a display screen in the parking assist process according to the present embodiment. The display screen of  FIG. 7D  is a display screen when the vehicle stops at the position P 4  in  FIG. 4D . 
     The control device  10  controls the display  21  to display the display screen as illustrated in  FIG. 7D  thereby to present the target parking space Mo to the driver and passengers. The driver and passengers find the messages included in the image  21 C and can confirm that the automated driving can be started. 
       FIG. 7E  is a fifth view for describing an example of a display screen in the parking assist process according to the present embodiment. When the automated driving is started, the display screen of the display  21  becomes a screen as illustrated in  FIG. 7E , and the subject vehicle moves forward. At this time, the image  21 C is displayed with messages informing that the subject vehicle is moving forward by the automated driving and that the driver and passengers should gaze around the subject vehicle. 
     In the present embodiment, a determination may be made as to whether or not the subject vehicle decelerates, and when the recommended available parking space is displayed in a state in which the subject vehicle decelerates, the recommended available parking space may be prohibited from changing to another available parking space. In general, the case in which a vehicle decelerates in the vicinity of the parking space may often be a case in which the driver or passenger determines the recommended available parking space as the target parking space and starts parking. If, at that time, the recommended available parking space changes, it will be difficult for the driver or passenger to select the recommended available parking space into which the driver or passenger intends to park. Thus, the recommended available parking space is prohibited from changing to another available parking space, and the recommended available parking space into which the driver or passenger intends to park can thereby be maintained and displayed. 
     As described above, according to the present embodiment, available parking spaces are detected, a recommended available parking space is set among the detected available parking spaces in accordance with the traveling state of the subject vehicle, and the set recommended available parking space is displayed on the display  21 . Through this operation, an available parking space suitable for the automated driving can be presented to the driver and passengers. 
     According to the present embodiment, the required time for parking when the subject vehicle is parked into each of the available parking spaces is calculated, and among the available parking spaces, an available parking space with which the required time for parking is shorter than a predetermined time is set as the recommended available parking space. Through this operation, an available parking space with which the required time for parking is short can be presented to the driver and passengers. 
     According to the present embodiment, the required time for parking when the subject vehicle is parked into each of the available parking spaces is calculated, and among the available parking spaces, an available parking space with which the required time for parking is shortest is set as the recommended available parking space. Through this operation, the available parking space with which the required time for parking is shortest can be presented to the driver and passengers. 
     According to the present embodiment, a position separate from the subject vehicle by a given gaze point distance is specified as a gaze point, and among the available parking spaces, an available parking space with which the distance from the gaze point to the available parking space is shorter than a predetermined distance threshold is set as the recommended available parking space. Through this operation, an available parking space suitable for the automated driving can be presented to the driver and passengers while reflecting the intention of the user. 
     According to the present embodiment, a position separate from the subject vehicle by a given gaze point distance is specified as a gaze point, and among the available parking spaces, an available parking space with which the distance from the gaze point to the available parking space is shortest is set as the recommended available parking space. Through this operation, an available parking space suitable for the automated driving can be presented to the driver and passengers while reflecting the intention of the user. 
     According to the present embodiment, the ease of entry when the subject vehicle is parked into each of the available parking spaces by the automated driving is evaluated, and among the available parking spaces, an available parking space into which entry is easiest is set as the recommended available parking space. Through this operation the available parking space into which the entry is easiest can be presented to the driver and passengers. 
     According to the present embodiment, among a first available parking space and a second available parking space that are disposed side by side along a direction parallel to the travel direction of the subject vehicle, the first available parking space farther from the subject vehicle than the second available parking space is set as the recommended available parking space. In a state in which the vehicle speed of the subject vehicle decreases, the recommended available parking space is prohibited from moving from the first available parking space to the second available parking space on the display screen of the display  21 . Through this operation, unnatural movement of the recommended available parking space Mr can be prevented. 
     According to the present embodiment, when the recommended available parking space is displayed in a state in which the subject vehicle decelerates, the recommended available parking space is prohibited from changing to another available parking space. Through this operation, the recommended available parking space can be maintained and displayed while making aware of the driver&#39;s intention (passengers&#39; intention) of parking. 
     According to the present embodiment, when parking spaces are present at the right and left with respect to the travel direction of the subject vehicle, one of the right and left regions is set as a settable region for the recommended available parking space in accordance with the traveling state of the subject vehicle, and a parking space included in the settable region is set as the recommended available parking space. This can suppress a phenomenon that the frame of the recommended available parking space is repeatedly displayed at the right and left on the display screen of the display  21  (hunting). 
     According to the present embodiment, the distance from the parking space located on a side of the subject vehicle to the subject vehicle is calculated as a lateral distance, and one of the right and left regions is set as the settable region for the recommended available parking space in accordance with the length of the lateral distance. The characteristic when one of the right and left regions is selected is a hysteresis characteristic with respect to the length of the lateral distance. This can suppress a phenomenon that the frame of the recommended available parking space is repeatedly displayed at the right and left on the display screen of the display  21  (hunting). 
     According to the present embodiment, when a predetermined number or more of the available parking spaces are present, an available parking space located at one of the right and left is set as the recommended available parking space in accordance with the traveling situation of the subject vehicle. This can suppress a phenomenon that the frame of the recommended available parking space is repeatedly displayed at the right and left on the display screen of the display  21  (hunting). 
     In the present embodiment, the number of recommended available parking spaces set by the control device  10  is not limited to one and may be two or more. The number of recommended available parking spaces displayed on the display  21  is also not limited to one and may be two or more. 
     In the present embodiment, to prevent the display screen of the display  21  from showing an unnatural movement such that the frame of the recommended available parking space Mr returns below on the screen, a hysteresis characteristic is given to the relationship between the vehicle speed and the gaze point distance, but the control may be modified as below. As illustrated in  FIG. 4C , the control device  10  sets the available parking space PL 5  as the recommended available parking space and controls the display  21  to display the recommended available parking space. As the subject vehicle decelerates, the control device  10  sets the available parking space PL 4  as the recommended available parking space. The control device  10  controls the display  21  to continue to display the available parking space PL 5  as the recommended available parking space rather than displaying the set available parking space PL 4 . That is, in the setting control for the recommended available parking space, even when the position of an available parking space relatively moves in the direction of approaching the subject vehicle due to decrease of the vehicle speed, the display position of the recommended available parking space is fixed on the display screen of the display  21 . This can prevent the unnatural movement of the recommended available parking space Mr. 
     In the present embodiment, the available parking space Me closest to the gaze point is set as the recommended available parking space Mr, but the available parking space Me with which the distance from the gaze point to the available parking space Me is shorter than a predetermined distance threshold may be set as the recommended available parking space Mr. When there is a plurality of recommended available parking spaces Mr that can be set in accordance with the distances from the gaze point to the available parking spaces Me, an available parking space with which the parking-related cost is low may be set as the recommended available parking space Mr. 
     Second Embodiment 
     The parking assist system according to another embodiment of the present invention will be described. This embodiment is different from the above-described first embodiment in that the length of the gaze point distance is changed in accordance with the travel direction of the subject vehicle. Other configuration is the same as that of the first embodiment, and the description is borrowed herein. 
       FIGS. 8A-8B  are a set of views for describing an example of the parking assist process according to the present embodiment.  FIG. 8A  illustrates a view when the subject vehicle is parked into the target parking space Mo from a state in which the subject vehicle is traveling forward (forward state).  FIG. 8B  illustrates a view when the subject vehicle is parked into the target parking space Mo from a state in which the subject vehicle is traveling backward (backward state). 
     In  FIG. 8A , it is assumed that the current position of the subject vehicle is P 6 , the gaze point when the position of the subject vehicle is P 6  is G 6 , and the turning point is P 7 . In  FIG. 8B , it is assumed that the gaze point when the position of the subject vehicle is P 6  is Gb. The gaze point Ga is a gaze point when set from the same gaze point distance as that in the forward state. 
     In a state in which the subject vehicle is traveling forward as illustrated in  FIG. 8A , when the subject vehicle is parked into the available parking space PL 5  in the backward parking (a parking state in which the subject vehicle can move forward to exit from the available parking space), the subject vehicle stops in the vicinity of the gaze point, then moves forward to the turning point P 7 , turns for parking at the point P 7 , moves backward to the available parking space PL 5 , and parks into the available parking space PL 5 . On the other hand, in a state in which the subject vehicle is traveling backward as illustrated in  FIG. 8B , when the subject vehicle is parked into the available parking space PL 5  in the backward parking, the subject vehicle stops at the start position of the automated driving and then moves backward from the start position of the automated driving to the available parking space PL 5  to park into the available parking space PL 5  without turning for parking. 
     When the subject vehicle is traveling forward, the distance between the start position of the automated driving and the target parking space Mo is short. On the other hand, when the subject vehicle is traveling backward, the distance between the start position of the automated driving and the target parking space Mo is longer than that when the subject vehicle is traveling forward because the subject vehicle does not turn for parking. 
       FIG. 9  is a graph illustrating a relationship between the vehicle speed (V [km]) and the gaze point distance (Y [m]). The solid line indicates a characteristic in the backward state while the dotted line indicates a characteristic in the forward state. In the forward state, when the vehicle speed is lower than Vc, the gaze point distance is Ya. When the vehicle speed is within a range of Vc or higher and lower than Vd, the gaze point distance increases in proportion to the vehicle speed. When the vehicle speed is not lower than Vd, the gaze point distance is Yb. In the backward state, when the vehicle speed is lower than Ve (Vc&lt;Ve&lt;Vd), the gaze point distance is Yc (Ya&lt;Yc&lt;Yb). When the vehicle speed is within a range of Ve or higher and lower than Vd, the gaze point distance increases in proportion to the vehicle speed. When the vehicle speed is not lower than Vd, the gaze point distance is Yb. The gaze point distance Yc is preliminarily set in accordance with the length of the travel route when the automated operation is performed from the state in which the vehicle moves backward. 
     As illustrated in  FIG. 9 , when the vehicle speed becomes lower than Ve in a state in which the subject vehicle is traveling backward, the gaze point distance is set to Yc which is longer than the gaze point distance (Ya) in the forward state. The gaze point (corresponding to the start position of the automated driving) located behind the subject vehicle is therefore set to be far. The recommended available parking space set in the vicinity of the gaze point is set at a position separate from the subject vehicle accordingly. That is, in the present embodiment, an appropriate length of the gaze point distance can be set to match each of the travel route when parking by the automated driving from the forward state and the travel route when parking by the automated driving from the backward state. 
     As described above, according to the present embodiment, the length of the gaze point distance is set in accordance with whether the travel direction of the subject vehicle is forward or backward. Through this operation, a parking space suitable for the automated driving can be presented to the driver and passenger in accordance with the travel direction of the subject vehicle in the parking area. 
     REFERENCE SIGNS LIST 
     
         
           1000  Parking assist system 
           100  Parking assist apparatus 
           10  Control device 
           11  CPU 
           12  ROM 
           13  RAM 
           20  Output device 
           21  Display 
           22  Speaker 
           23  Lamp 
           1   a - 1   d  On-board cameras 
           2  Image processing device 
           3  Ranging device 
           30  Vehicle controller 
           40  Drive system 
           50  Steering angle sensor 
           60  Vehicle speed sensor 
         V Vehicle 
         Me Available parking space 
         Mr Recommended available parking space 
         Mo Target parking space