Patent Publication Number: US-2023159021-A1

Title: Parking Assistance Device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2021-188385 filed on Nov. 19, 2021. The content of the application is incorporated herein by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a parking assistance device. 
     Description of the Related Art 
     Document 1 discloses a technology relating to selecting a route for use in automatic parking. The Abstract of Document 1 states, “Problem to be Solved” section, that “when there is a plurality of routes to a single parking space, it is not possible to park automatically using a route with short parking time.” In the Means for Solving the Problem” section in the Abstract there is the description of “A route candidate generating unit  301  varies the standard vehicle speed and route shape to search for a route that arrives at the parking destination from the parking starting location. A route travel time calculating unit  302  calculates the time required for traveling the route based on a standard vehicle speed and the length of the route for each individual candidate route. A state switching time calculating unit  303  calculates the time required, for each route candidate, to switch between forward and reverse vehicle travel and to turn the steering, to change to the predetermined steering angle in a state in which the vehicle is stationary. Based on the route travel times, the route selecting processing unit  305  selects a specific route, such as, for example, the route with the shortest parking time, from the routes that have been generated.” 
     PRIOR ART DOCUMENT 
     Patent Document 
     
         
         [Patent Document 1] Japanese Unexamined Patent Application Publication 2019-127112 
       
    
     SUMMARY OF THE INVENTION 
     Problem Solved by the Present Invention 
     However, when an object exists in the vicinity of the route that has been selected, a vehicle occupant, such as the driver, may feel anxiety when the vehicle passes by such an object. 
     The object of the present invention is to provide a parking assistance device that is able to reduce the anxiety of the vehicle occupants. 
     SUMMARY OF THE INVENTION 
     One aspect of the present invention includes: a vehicle location acquiring unit for acquiring the current location of a vehicle; an object information acquiring unit for acquiring object information that includes information relating to a location of an object in the vicinity of the vehicle; and a target route setting unit for setting a plurality of routes between the current location and a predetermined parking space, identifying the route, of the plurality of routes, with the longest distance to the object, and, based on the identified route, setting a target route for the vehicle to travel from the current location to the predetermined parking space. 
     Effects of the Invention 
     One aspect of the present invention is able to reduce anxiety of the vehicle occupants. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a diagram showing a structure of a parking assistance system according to an embodiment according to the present invention. 
         FIG.  2    is a flowchart of an automatic parking controlling process executed by the parking assistance device. 
         FIG.  3    is a flowchart of a route setting process. 
         FIG.  4    is an explanatory diagram regarding the route setting process. 
         FIG.  5    is a schematic diagram of the multiple paths used in the route setting process. 
         FIG.  6    is a schematic diagram showing identification of the route with the minimum route cost. 
         FIG.  7    is an explanatory diagram regarding the distance to the side of the vehicle. 
         FIG.  8    is an explanatory diagram of vehicle speed control depending on node costs. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     An embodiment according to the present invention will be explained below in reference to the drawings. 
       FIG.  1    is a diagram showing the structure of a parking assistance system  1  according to the present embodiment. 
     The parking support system  1  is a vehicle-mounted system that, when a parking area Pb ( FIG.  4   ) exists in a parking lot or the like, for example, when a start instruction is given by an occupant such as a driver, the vehicle  2  automatically travels from the current position Pa ( FIG.  4   ) to a predetermined parking area Pb, and the vehicle  2  automatically parks in the predetermined parking area Pb to assist the driver&#39;s driving when the vehicle  2  is parked. Automatic traveling and automatic parking refer to autonomous or semi-autonomous traveling and parking of the vehicle  2 . The parking assistance system  1 , as shown in  FIG.  1   , comprises a parking assistance device  10 , an automatic driving system  4 , an object detecting unit  6 , and a vehicle location detecting unit  8 , where these are either connected together through an in-vehicle network, such as a CAN, or the like, or are connected together directly. 
     The parking assistance device  10  is a device that executes a process (an automatic parking controlling process ( FIG.  2   ) for setting a target route Q ( FIG.  4   ) from the current location Pa to a predetermined parking space Pb, and for causing the vehicle  2  to travel along the target route Q to complete parking in the predetermined parking space Pb. This parking assistance device  10  has a computer (which, in the present embodiment, is an ECU (Electric Control Unit) comprising a processor such as a CPU (Central Processing Unit) or MPU (microprocessor), or the like), a memory device (also termed a “main storage device”) such as a ROM (Read Only Memory) or a RAM (Random Access Memory), a storage device (also termed a “supplementary storage device”) such as an HDD (Hard Disk Drive) or an SSD (Solid State Drive), an interface circuit for connecting to sensors, peripheral devices, or the like, and an in-vehicle network communication circuit for communicating with other in-vehicle devices through an in-vehicle network. Through the processor executing a computer program that is stored in the memory device or the storage device, the parking assistance device  10  achieves a variety of functional structures relating to automatic parking control. These functional structures will be described below. 
     The automatic driving system  4  is a system for executing automatic driving of the vehicle  2 , and comprises an automatic driving ECU  4 A for executing control of the automatic driving, and various actuators  4 B for causing the vehicle  2  to travel. The automatic driving system  4  parks the vehicle  2  in a predetermined parking space Pb through the automatic driving ECU  4 A causing the vehicle  2  to travel automatically along a target route Q, through controlling the various actuators  4 B based on output signals from the parking assistance device  10 . 
     The actuators  4 B include, for example, a vehicle driving actuator, a brake actuator, and a steering actuator. The vehicle driving actuator is a device or system that includes a motive source (a motor or engine) for the vehicle  2 , and a control device (an ECU, or the like) for controlling the motive source. The brake actuator is a device or system for actuating the braking system equipped in the vehicle  2 . The steering actuator is a device or system for actuating assist motors for controlling the steering torque of an electric power steering system. 
     Note that the automatic driving system  4  may use, arbitrarily, a publicly known or well-known system that enables vehicle  2  to travel autonomously or semi-autonomously. 
     The object detecting unit  6  comprises an object detecting sensor  6 A for detecting an object K in the vicinity of the vehicle  2  ( FIG.  4   ), to output a detection signal (hereinafter termed the “object detection signal  6 S”) to the parking assistance device  10 . In the present embodiment, vehicle-mounted cameras (that is, CCD sensors) that image the vicinity of the vehicle  2  and output imaging data to the parking assistance device  10  are used as the object detecting sensor  6 A. These vehicle-mounted cameras include a front camera for imaging forward from the vehicle  2 , a rear camera for imaging rearward, a left side camera for imaging toward the left side, and a right side camera for imaging toward the right side, where the various data captured by these cameras are used to produce a captured image of the entire periphery (in a 360° range) of the vehicle  2 . 
     An object K may be any object that is indicated on the travel route of the vehicle  2 , and any object that would interfere with the travel of the vehicle  2 . The object K may be, for example, a passageway, a parking space, a stop line, a white line, another vehicle, a structure (a building, wall, signal, sign, or the like), a pedestrian, or the like. 
     Additionally, in addition to the vehicle-mounted cameras, a LiDAR (Light Detection and Ranging), radar, sonar, or the like, which may be used either singly or in combinations thereof, may be used appropriately as the object detecting sensor  6 A of the object detecting unit  6 . 
     The vehicle location detecting unit  8  comprises a location detector  8 A that detects the location of the vehicle  2  itself and outputs a detection signal (hereinafter termed the “vehicle location detection signal  8 S”) to the parking assistance device  10 . An arbitrary publicly known device such as, for example, a receiver for receiving a GNSS (Global Navigation Satellite System) signal, a gyro sensor, an acceleration sensor that is used in autonomous navigation, or another publicly known sensor may be used arbitrarily in the location detector  8 A. 
     The parking assistance device  10  comprises, as its functional structure, a vehicle location acquiring unit  20 , an object information acquiring unit  22 , a target route setting unit  24 , and an automatic travel directing unit  26 . 
     The vehicle location acquiring unit  20  acquires the current location Pa by calculating the current location Pa of the vehicle  2  based on the vehicle location detection signal  8 S of the vehicle location detecting unit  8 . 
     The object information acquiring unit  22  acquires information regarding objects K in the vicinity of the vehicle  2  (hereinafter termed “object information A”) by analyzing an object detection signal  6 S (which, in the present embodiment, is imaging data) from the object detecting unit  6 . 
     The object information A is information that is used in setting the target route Q. The target route Q in the present embodiment is set as a route wherein the vehicle  2  will not contact an object K and will not cause the vehicle occupant to feel anxiety when the vehicle  2  passes by the objects K. The object information A includes, as information for setting the target route Q, the locations and sizes (such as the outer dimensions, shapes, and the like) of the objects K. 
     Note that the object information acquiring unit  22  may be structured so that the object information acquiring unit  22  will acquire the object information A by generating object information A through analyzing information detected by the object detecting unit  6  or by other suitable devices, rather than structured to analyze the object information A itself. The techniques for analyzing and generating object information A based on the information detected by the object detecting unit  6  may use an appropriate publicly known or well-known technique such as, for example, an image recognition process. 
     The target route setting unit  24  sets the target route Q based on the current location Pa, the location of the predetermined parking space Pb, and the object information A. 
     Specifically, the target route setting unit  24 , based on the locations and sizes of objects K in the vicinity of the vehicle  2 , sets the target route Q to be a route from the current location Pa to the predetermined parking space Pb without the vehicle  2  contacting an object K, so is able to reduce the feeling of anxiety by the vehicle occupant when the vehicle  2  passes by the objects K. 
     Note that the target route setting unit  24  may reference map data that indicates a map of the vicinity, when setting the target route Q. The map data may be stored in advance in the parking assistance device  10 , or may be received through an electronic communication circuit (for example, the Internet) from a device (for example, a system for controlling a parking lot) that is external to the vehicle  2 . 
     Additionally, the technique for setting the predetermined parking space Pb is arbitrary, and may use, for example, a technique wherein the vehicle occupant provides direction, such as specifying a location on a map, or a technique wherein a publicly known or well-known technique is used to detect a space wherein the vehicle  2  can park, and setting that space as the parking space. 
     The automatic travel directing unit  26  generates output signals to direct the automatic travel of the vehicle  2  along the target route Q that has been set by the target route setting unit  24 , and outputs the output signals to the automatic driving system  4 . Additionally, the automatic travel directing unit  26  is equipped with a function for directing the automatic driving system  4  so as to park the vehicle  2  into a predetermined parking space Pb. Note that the technique for parking the vehicle  2  into the parking space Pb using the automatic driving system  4  may use an arbitrary publicly known or well-known technique. 
       FIG.  2    is a flowchart for an automatic parking controlling process executed by the parking assistance device  10 . 
     When a vehicle occupant inputs an instruction to execute automatic parking by operating a switch that is provided in the vehicle  2  or a mobile electronic device carried by the vehicle occupant (for example, a smart phone), the execution instruction is inputted into the parking assistance device  10 , and the parking assistance device  10  starts the automatic parking controlling process shown in this figure. 
     In the automatic parking controlling process, first the vehicle location acquiring unit  20  acquires the current location Pa of the vehicle  2 , and the object information acquiring unit  22  acquires object information A for objects K in the vicinity of the vehicle  2  (Step Sa 1 ). Next the target route setting unit  24  executes a route setting process ( FIG.  3   ), described below, to set the target route Q (Step Sa 2 ). Then, the automatic travel directing unit  26  outputs the above output signals to the automatic driving system  4 , to provide direction for automatic driving to the automatic driving system  4  (Step Sa 3 ). Through this, the vehicle  2  will travel automatically along the target route Q, under the control of the automatic driving system  4 , to complete parking in the predetermined parking space Pb. 
       FIG.  3    is a flowchart of the route setting process referenced above, and  FIG.  4    is an explanatory diagram regarding the route setting process.  FIG.  5    is a schematic diagram of multiple paths M used in the route setting process. 
     The target route setting unit  24  first sets (provisionally) a target route Q based on the object information A (Step Sb 1 ). In this case, the target route Q that has been set is a route that enables the vehicle  2  to travel from the current location Pa to the predetermined parking space Pb without contacting an object K, as shown in  FIG.  4   . That is, the target route setting unit  24 , in Step Sb 1 , identifies a surrounding region wherein the vehicle  2  can travel without contacting the objects K, based on the locations and sizes of the objects K in the vicinity of the vehicle  2 , to set a route from the current location Pa to the predetermined parking space Pb within the range of that surrounding region. 
     The target route setting unit  24  then executes a route adjusting process to adjust the target route Q. The route adjusting process is a process for adjusting the target route Q to a route that is able to reduce the anxiety of the vehicle occupant when the vehicle  2  passes by an object K. 
     Specifically, first the target route setting unit  24  segments the target route Q, set in Step Sb 1 , into a plurality of route segments Qa, as shown in  FIG.  4    (Step Sb 2 ). In the present embodiment, the individual route segments Qa are segmented by predetermined travel distances. While the length of the predetermined travel distance is arbitrary, in the present embodiment it is set to between 10 and 20 m (to a multiple of the length of the vehicle  2 , for example). 
     Next the target route setting unit  24  adjusts the route for each route segment Qa. 
     Specifically, first the target route setting unit  24  sets multiple paths M to endpoints R on both ends of each route segment Qa (Step Sb 3 ). The multiple paths M, as shown in  FIG.  5   , are at least two routes MQ (which, in the illustrated example, is five routes) that connect the endpoints R on both ends of the route segment Qa, where routes MQ are set with mutually differing waypoints for the vehicle  2  in the crosswise direction Db (the vehicle width direction) that is perpendicular to the direction of travel Da. 
     The target route setting unit  24  in the present embodiment sets the multiple paths M as follows. 
     Specifically, as shown in  FIG.  5   , in a route segment Qa, the target route setting unit  24  specifies a midpoint Ro with equal distances Ta to the endpoints R on both ends, and sets a plurality of first nodes N 1 , with predetermined spacing Tb, on a straight line that extends in the crosswise direction Db that passes through the midpoint Ro. Note that the direction of travel Da is the direction that connects the endpoints R on both ends with a straight line, and the crosswise direction Db is the direction that is perpendicular to the travel direction Da. Following this, the target route setting unit  24  sets, for each of the first nodes N 1 , a route MQ that passes through the applicable first load N 1  from one end point R to arrive at the other end point R. Multiple paths M, that include multiple routes MQ, are set thereby. If object information A for an object K that is a marker for a travel route that is a road or a white line can be acquired, the target route setting unit  24  may reference the object information A to set the route MQ within the range of that travel route. 
     Returning to  FIG.  3   , referenced above, the target route setting unit  24  identifies a route, from among the individual routes MQ of the multiple paths M, that can reduce the anxiety felt by the vehicle occupant when the vehicle  2  passes by the object K. Describing this in detail, the anxiety felt by the vehicle occupant is anxiety regarding contact when the vehicle  2  passes by the object K, and is felt more strongly the shorter the distance between the object K and the vehicle  2  (hereinafter termed the vehicle-object distance). Because of this, from among the routes MQ in the multiple paths M, having the vehicle  2  travel a route MQ wherein the vehicle-object distance is long will reduce this anxiety. 
     The target route setting unit  24  in the present embodiment identifies a route MQ with a long vehicle-object distance as follows. 
     Specifically, first the target route setting unit  24  calculates a route cost C for each route MQ of the multiple paths M (Step Sb 4 ). The route cost C is a parameter calculated based on the vehicle-object distance for the target route MQ, and is a parameter whose value decreases as the vehicle-object distance increases. 
     The target route setting unit  24  next identifies the route MQ, from among the individual routes MQ of the multiple paths M, that minimizes the route cost C, that is, the longest vehicle-object distances (Step Sb 5 ). The target route setting unit  24  next sets the final target route Q by connecting together the routes MQ identified for each of the route segments Qa (Step Sb 6 ). 
     When the vehicle  2  travels along the target route Q, as shown in  FIG.  6   , the vehicle  2  travels along the route MQ farthest from the object K present in the target route segment Qa among the multipaths M in any of the route segments Qa, thereby reducing the anxiety of the occupant when the vehicle  2  passes by the object K. 
     A method for calculating the route cost C, described above, will be described in detail next. 
     The target route setting unit  24  according to the present embodiment calculates the route cost C, for each individual route MQ of the multiple paths M, as follows. Specifically, as shown in  FIG.  5   , for each individual route MQ of the multiple paths M, the target route setting unit  24  sets second nodes N 2 , at predetermined intervals, from the first nodes N 1 , and calculates a node cost Cn for each of the first nodes N 1  and second nodes N 2 . The node cost Cn is a parameter whose value becomes smaller as the vehicle-object distance becomes longer when the vehicle  2  is located at the first node N 1  and the second node N 2 . In this embodiment, the vehicle-side distance rs is used as the vehicle-object distance. 
       FIG.  7    is an explanatory diagram for the distance rs to the side of the vehicle. Note that in this diagram, four other vehicles Ka 1  to Ka 4  are illustrated as examples of objects K. 
     The distance rs to the side of the vehicle is the shortest distance Lmin to the object K from an extension of the vehicle side face  2 SE. As shown in  FIG.  7   , the extensions of the vehicle side faces  2 SE are planes that extend, in the lengthwise direction of the vehicle  2 , the side faces  2 S on the left and right of the vehicle  2  at the applicable first node N 1  or second node N 2 , and are reference planes that serve as a metric for screening the objects K to be subject to the calculations of the distances rs in the direction to the side of the vehicle (the node cost Cn). 
     Specifically, in a range V, in the lengthwise direction of the vehicle, of the extension of the vehicle side face  2 SE, each object K (the other vehicles Ka 1  through Ka 4 ) that exists in the crosswise direction Db of the extension of the vehicle side face  2 SE is selected as the object for calculating the distance rs in the direction to the side of the vehicle. 
     In the example in  FIG.  7   , the target route setting unit  24  excludes, from being objects for calculating the distance rs in the direction to the side of the vehicle, the two other vehicles Ka 3  and Ka 4  that are outside of the range V, in the vehicle lengthwise direction, of the extension of the vehicle side face  2 SE, and selects, as objects for calculating the distances rs in the direction to the side of the vehicle, both of the remaining other vehicles Ka 1  and Ka 2 . 
     Note that the target route setting unit  24  sets the extension length, in the vehicle lengthwise direction, of the extension of the vehicle side face  2 SE, to a length that is proportional to the vehicle speed when the vehicle  2  passes through the applicable first node N 1  or second node N 2 . This causes the range V, in the vehicle lengthwise direction, of the extension of the vehicle side face  2 SE to be greater the faster the vehicle speed, so that objects K that are even farther away from the vehicle  2  will be selected as objects for the calculation of the distances rs in the direction to the side of the vehicle (the node costs Cn). 
     The target route setting unit  24 , upon selection of objects K for the calculation of distances rs in the direction to the side of the vehicle, identifies, based on the object information A, the nearest points U to the extension of the vehicle side face  2 SE for each of the outer dimensions (profiles) of these objects K, and defines, as the distance rs in the direction to the side of the vehicle, the shortest distance Lmin that is the shortest of all of the shortest distances Lmin between the extension of the vehicle side face  2 SE and each of the points U. In the example in  FIG.  7   , the other vehicle Ka 1  is closer than the other vehicle Ka 2 , and thus the target route setting unit  24  calculates the shortest distance Lmin from the point U on the outer shape of the other vehicle Ka 1  to the extension of the vehicle side face  2 SE as the distance rs in the direction to the side of the vehicle. 
     The target route setting unit  24  next calculates the node cost Cn using the following Equation (1) based on the distance rs in the direction to the side of the vehicle. Note that in Equation (1), α is a constant. 
         Cn =α/( rs×rs )  (1)
 
     Given this, the target route setting unit  24  uses the following Equation (2) to calculate the total cost value of the node costs Cn for each route MQ as the route cost C: 
       Route cost  C =Σnode cost  Cn   (2)
 
     This calculation enables reliable identification of the route MQ with the longest vehicle-object distances when the vehicle  2  passes by the objects K, based on the route cost C, because the value of the route cost C will be less for routes MQ that include many first nodes N 1  and second nodes N 2  that have long distances rs in the direction to the side of the vehicle. 
     Next the target route setting unit  24 , in calculating the node costs Cn using Equation (1), sets the value of the node cost Cn to be extremely large if there is an object K that exists on the extension of the vehicle side face  2 SE (that is, if the shortest distance Lmin is less than zero, meaning that there is an object K with which the vehicle  2  may collide). This makes it possible to prevent reliably the inclusion, in the final target route Q, of a route MQ wherein the vehicle  2  could collide with the object K. 
     Moreover, in the present embodiment, control is carried out so as to cause the vehicle occupant to have a greater sense of safety by having the vehicle speed be relatively slow when the distance rs in the direction to the side of the vehicle is relatively small when the vehicle  2  passes by an object K. 
     Specifically, in Step Sa 3  of the automatic parking controlling process, shown in  FIG.  2   , presented above, the automatic travel directing unit  26  executes the following process when outputting the output signals to the automatic driving system  4 . Specifically, the automatic travel directing unit  26  determines whether or not a first node N 1  or second node N 2  with a node cost Cn that is greater than a predetermined value is included in the target route Q that was ultimately set by the target route setting unit  24 , that is, determines whether or not a first node N 1  or second node N 2  is included where the vehicle  2  will pass by the object K with a distance rs in the direction to the side of the vehicle that is less than the predetermined value. Given this, if such a first node N 1  or second node N 2  is included, the automatic travel directing unit  26  outputs output signals directing the automatic driving system  4  to have the vehicle speed be no greater than a predetermined speed that is slower than the normal vehicle speed (at a low speed) when passing through the applicable first node N 1  or second node N 2 . 
     Specifically, as shown in  FIG.  8   , for example, when the node cost Cn of a second node N 2 A exceeds a predetermined value, the automatic travel directing unit  26  outputs directions to decelerate the vehicle  2  from the normal vehicle speed (the vehicle speed that has been set in advance as the vehicle speed for automatic travel) from a second node N 2 A- 1  prior to passing through the second node N 2 A, and to accelerate so as to restore the vehicle  2  to the normal vehicle speed beginning with a second node N 2 A- 2  after passing through the second node N 2 A. 
     This makes it possible to cause the vehicle occupant to have a feeling of safety, given that the vehicle  2  will pass by the object K in an adequately low-speed state through decelerating the vehicle  2  prior to passing the object K, if the vehicle  2  is to pass by an object K with a distance rs in the direction to the side of the vehicle that is less than the predetermined value. 
     Note that if the node cost Cn is less than a predetermined threshold value, that is, if the vehicle  2  passes by an object K with a distance rs in the direction to the side of the vehicle that is greater than a predetermined threshold value, the automatic travel directing unit  26  outputs a direction to increase the speed of the vehicle  2  to greater than the normal vehicle speed. 
     The present embodiment has effects such as described below. 
     The parking assistance device  10  according to the present embodiment is equipped with a target route setting unit  24  that sets a plurality of routes MQ between the current location Pa of the vehicle  2  and a predetermined parking space Pb, identifies the route MQ, from among the plurality of routes MQ, that has the longest distance from the object K, and, based on the identified route MQ, sets the target route Q for the vehicle  2  to travel from the current location Pa to the predetermined parking space Pb. 
     According to this configuration, since the route MQ farthest from the object K is set to the target route Q, the occupant can be reduced the anxiety that feels when the vehicle  2  passes by the object K as compared with the case where the vehicle  2  passes near the object K. 
     In the parking assistance device  10  according to the present embodiment, the target route setting unit  24  sets a first node N 1  and a second nodes N 2  for each of the plurality of routes MQ, and calculates a node cost Cm for which the value becomes smaller as the distance between the first node N 1  and the second nodes N 2  and the object K is longer for each of the first node N 1  and the second nodes N 2 . Next, the target route setting unit  24  calculates, for each of the plurality of routes MQ, a route cost C that is a sum of the node costs Cn of the first node N 1  and the second nodes N 2  included in the route MQ. The target route setting unit  24  identifies a route MQ having the smallest route cost C among the plurality of routes MQ, and sets the target route Q based on the identified route MQ. 
     This structure makes it possible to quantify the distances between the routes MQ and the object K, for each of a plurality of routes MQ, to make accurate comparisons. 
     In the parking assistance device  10  according to the present embodiment, the node cost Cn is a parameter that becomes smaller as the shortest distance Lmin between the object K and a side face  2 S of the vehicle  2  that is located at the first node N 1  and the second nodes N 2  is longer. 
     This makes it possible to calculate the node cost Cn based on the shortest distance Lmin between the object K and the vehicle  2  when the vehicle  2  passes by the object K (that is, when the object K is located to the side of the vehicle  2 ). 
     In the parking assistance device  10  according to the present embodiment, the target route setting unit  24  calculates the node cost Cn for an object K that exists in a range V from an extension of the vehicle side face  2 SE wherein the side face  2 S of the vehicle  2  that is located at the first node N 1  or a second node N 2  is extended in the vehicle lengthwise direction depending on the speed of the vehicle  2 . 
     This makes it possible to calculate the node cost Cn for only the object K that is present by the vehicle  2  when the vehicle  2  passes through the first node N 1  or the second node N 2 . 
     The parking assistance device  10  according to the present embodiment includes the automatic travel directing unit  26 . When a first node N 1  and a second node N 2  having a node cost Cn of a predetermined value or more are included in a target route Q set by a target route setting part  24 , the automatic travel directing unit  26  instructs the automatic driving system  4  to set a vehicle speed when passing through the first node N 1  and the second node N 2  having a node cost Cn of a predetermined value or more to a predetermined speed or less. 
     This structure decelerates the vehicle  2  so as to be no more than a predetermined speed when the vehicle  2  passes by the object K with a short distance rs in the direction to the side of the vehicle such that the node cost Cn will be higher than a predetermined value. This will cause the vehicle occupant to have a feeling of safety, despite the distance rs in the direction to the side of the vehicle being relatively short, given that the vehicle  2  will pass by the object K in a state wherein it is traveling adequately slowly. 
     In the parking assistance device  10  according to the present embodiment, the target route setting unit  24  segments a target route Q from the current location Pa to a predetermined parking space Pb into a plurality of route segments Qa, and sets a plurality of routes MQ (multiple paths M) for each route segment Qa, identifies the routes MQ with the longest distances from the object K for each of the route segments Qa, and sets the target route Q based on the individual routes MQ that have been identified. 
     This structure makes it possible to set accurately a target route Q that secures distances from each of the objects K such that the vehicle occupant will not feel anxiety, given that the target route Q is segmented into a plurality of route segments Qa and the route MQ that has the longest distance from each object K in each of the route segments Qa is identified, even in a case wherein, for example, the route length of the target route Q is relatively long, and the route extends past a large number of objects K. 
     The above embodiment is no more than an illustration of one aspect of the present invention, and can be modified and applied suitably in a range that does not deviate from the spirit and intent of the present invention. 
     For example, in the automatic parking control process shown in  FIG.  2   , presented above, after the automatic travel directing unit  26  has outputted directions to the automatic driving system  4  (Step Sb 3 ), the parking assistance device  10  may monitor whether or not there is an object K (for example, another vehicle, a pedestrian, or the like) that is moving toward the target route Q, based on an object detection signal  6 S of the object detecting unit  6 , and, upon detection of said object K, the automatic travel directing unit  26  may provide direction to the automatic driving system  4  to stop the vehicle  2 . 
     Additionally, for example, the target route setting unit  24  may also reflect the movement speed of the object K into the node cost Cn. For example, the target route setting unit  24  may increase the value of the node cost Cn more greatly with faster speeds of movement of objects K toward the first node N 1  or a second node N 2 . 
     In the above embodiment, the functional blocks shown in  FIG.  1    are schematic diagrams indicating classifications depending on the main processing details of the structural elements of the parking assistance system  1  and the parking assistance device  10 , to facilitate understanding of the invention according to the present application. 
     Consequently, the structural elements of the parking assistance system  1  and the parking assistance device  10  can be partitioned into a greater number of structural elements (functional blocks) depending on the processing details. Moreover, the partitioning may be such that a single structural element will execute a greater number of processes. 
     In addition, the processes of each of the structural elements of the parking assistance device  10  shown in  FIG.  1    may instead be executed in a single hardware element, or in a plurality of hardware elements. Additionally, the processes of each of the structural elements may be achieved through a single program or achieved through a plurality of programs. 
     Unless stated explicitly otherwise, directions, such as horizontal and vertical directions, and various other types of numeric values, shapes, materials, and the like, in the embodiment set forth above include ranges that produce the same effects in operation as those directions, numeric values, shapes, and materials (so-called “scope of equivalency”). 
     EXPLANATIONS OF REFERENCE SYMBOLS 
     
         
           1 : Parking assistance system 
           2 : Vehicle 
           10 : Parking assistance device 
         K: Object 
         Lmin: Shortest distance 
         M: Multiple paths 
         Q: Target route 
         rs: Distance in the direction of the side of the vehicle