Patent Publication Number: US-2023158923-A1

Title: Position controlling device

Description:
BACKGROUND ART 
     The present disclosure relates to a position controlling device that controls the position of a loading platform provided in a mobile object. 
     A vehicle such as an automobile typically includes a seat configured to allow an occupant to sit thereon. A vehicle seat includes a backrest portion, against which an occupant rests their back, and a seat portion, on which the occupant sits down. A vehicle seat has a function of changing the angle of the backrest portion, a function of changing the angle of the seat portion, and the like (see Japanese Laid-Open Patent Publication No. 2021-146831). In a vehicle, it is possible to set the position of a seat and, thus, the seated position of an occupant, in accordance with the preference of the occupant or the use situation of the vehicle. 
     As vehicles incorporate advanced features, vehicle seats are also desired to incorporate advanced features, so as to improve ride comfort. Advanced features are desired to be incorporated into not only position controlling devices that control the position of a vehicle seat, but also a position controlling device that controls the position of a loading platform provided in a mobile object, such as a position controlling device that controls the position of a loading platform provided in an automatic guided vehicle. 
     SUMMARY OF THE DISCLOSURE 
     In a general aspect, a position controlling device is configured to control a position of a loading platform provided in a mobile object. The loading platform includes a loading portion that includes a portion capable of being loaded with a loaded object, a base portion that is provided below the loading portion in a manner of supporting the loading portion, and a coupling portion that includes a restoring member. The restoring member generates a restoring force for restoring the coupling portion to its original length when the coupling portion is extended. The coupling portion couples the base portion and the loading portion to each other with the restoring member between the base portion and the loading portion. The loading portion and the base portion are provided such that a lower part of the loading portion and an upper part of the base portion face each other. One of the upper part of the base portion and the lower part of the loading portion includes a spherical surface that is convex downward, and the other one of the upper part of the base portion and the lower part of the loading portion includes a guide portion. The guide portion guides the base portion and the loading portion such that the base portion and the loading portion are movable relative to each other in a direction along the spherical surface. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The features of the present disclosure that are believed to be novel are set forth with particularity in the appended claims. The disclosure, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which: 
         FIG.  1    is a schematic diagram showing a position controlling device according to a first embodiment. 
         FIG.  2    is a perspective view from obliquely below, showing a loading portion according to the first embodiment. 
         FIG.  3    is a perspective view from obliquely above, showing a base portion according to the first embodiment. 
         FIG.  4    is a schematic diagram of the position controlling device, showing a state in which the loading portion is moved forward with respect to the base portion. 
         FIG.  5    is a schematic diagram of the position controlling device, showing a state in which a seat body is moved forward with respect to a movable portion. 
         FIG.  6    is a schematic diagram showing a position controlling device according to a second embodiment. 
         FIG.  7    is a perspective view from obliquely below, showing a loading portion according to the second embodiment. 
         FIG.  8    is a schematic diagram showing a relative position changing mechanism according to the second embodiment. 
         FIG.  9    is a schematic diagram of a seat, showing a state in which the loading portion is moved forward with respect to the base portion. 
         FIG.  10    is a schematic diagram of the seat, showing a state in which the loading portion is moved leftward with respect to the base portion. 
         FIG.  11    is a schematic diagram showing a position controlling device according to another embodiment. 
         FIG.  12    is a schematic diagram showing the structure of a loading platform with which a position controlling device according to yet another embodiment is used. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
     A position controlling device according to a first embodiment will now be described with reference to  FIGS.  1  to  5   . 
     Vehicle  20   
     As shown in  FIG.  1   , a vehicle  20  includes a seat  21  configured to allow an occupant to sit thereon. The seat  21  is attached to a vehicle body  22 . In the present embodiment, the vehicle  20  corresponds to a mobile object, the seat  21  corresponds to a loading platform, the vehicle body  22  corresponds to a main body of the mobile object, and an occupant corresponds to a loaded object. 
     The seat  21  includes a loading portion  30 , on which an occupant is seated, and a base portion  40 , which supports the loading portion  30  from below. 
     Loading Portion  30   
     As shown in  FIGS.  1  and  2   , the loading portion  30  includes a seat portion  30 S, on which the occupant sits down, and a backrest portion  30 B, against which the occupant rests their back. The loading portion  30  has a structure in which the seat portion  30 S and the backrest portion  30 B are formed integrally. 
     The loading portion  30  includes a lower convex portion  33 . The lower convex portion  33  includes a lower part of the seat portion  30 S and a back part of the backrest portion  30 B. An outer surface (hereinafter, referred to as a support surface  33 A) of the lower convex portion  33  has a shape protruding in a direction away from the occupant seated on the loading portion  30 , that is, a shape bulging downward. In the present embodiment, the support surface  33 A of the lower convex portion  33  corresponds to a surface supported by the base portion  40 . Substantially the entire support surface  33 A forms a spherical surface that is convex downward in a direction away from the occupant seated on the loading portion  30 . 
     Base Portion  40   
     As shown in  FIGS.  1  and  3   , the base portion  40  is attached to the vehicle body  22 . The base portion  40  has a substantially columnar outer surface extending in an up-down direction Z of the vehicle  20 . The base portion  40  includes, at the upper end, an upper concave portion  41 , which is concave downward. The inner surface of the upper concave portion  41  is substantially spherical. 
     The upper concave portion  41  is provided with multiple (in the present embodiment, forty-six) guide portions  42 , which guide the base portion  40  and the loading portion  30  to allow the base portion  40  and the loading portion  30  to be movable relative to each other. The guide portions  42  are arranged at intervals in directions along the support surface  33 A of the loading portion  30 , which has a spherical surface.  FIG.  3    shows the base portion  40  in a state in which the guide portions  42  are yet to be attached. As shown in  FIG.  3   , the upper concave portion  41  includes attachment holes  42 A. The guide portions  42  ( FIG.  1   ) are attached to the attachment holes  42 A. 
     As shown in  FIG.  1   , each guide portion  42  includes a case  42 B and a contact ball  42 C. The cases  42 B are supported by the support surface  33 A of the upper concave portion  41 . Each contact ball  42 C has a spherical shape in contact with the support surface  33 A of the lower convex portion  33 , and is rotatably accommodated in the corresponding case  42 B. Freebears (registered trademark) may be used as the guide portions  42 . The guide portions  42  are evenly arranged at intervals on the entire inner surface of the upper concave portion  41 . 
     In the present embodiment, when the loading portion  30  is supported by the base portion  40  (the state shown in  FIG.  1   ), the contact balls  42 C of the guide portions  42  provided in the upper concave portion  41  of the base portion  40  come into contact with the support surface  33 A of the lower convex portion  33  of the loading portion  30 . In the present embodiment, the guide portions  42  allow base portion  40  and the loading portion  30  to move relative to each other in directions along the support surface  33 A of the loading portion  30 , which has a spherical surface. 
     Coupling Portion  50   
     A coupling portion  50 , which is attached to the seat  21 , couples the base portion  40  and the loading portion  30  to each other. The coupling portion  50  extends in a first direction (in the present embodiment, the up-down direction Z), which is a direction in which the loading portion  30  and the base portion  40  are arranged. The base portion  40  includes a coupling recess  43  in a center in plan view. The coupling recess  43  extends in the up-down direction Z from the upper end to the vicinity of the lower end of the base portion  40 . The coupling portion  50  is arranged inside the coupling recess  43 . The coupling portion  50  includes a spring portion  51 , an upper coupling portion  52 , and a lower coupling portion  53 . 
     Spring Portion  51   
     The spring portion  51  is a middle part in the up-down direction Z of the coupling portion  50 . The spring portion  51  incorporates a compression coil spring. The axis of the compression coil spring extends in the up-down direction Z. The spring portion  51  is configured to extend and contract in the up-down direction Z. The spring portion  51  has a structure in which the compression coil spring therein is elastically deformed in a compression direction when the spring portion  51  is extended. In the present embodiment, the spring portion  51  corresponds to a restoring member that generates a restoring force for restoring the coupling portion  50  to its original length when the coupling portion  50  is extended. 
     Upper Coupling Portion  52   
     The upper coupling portion  52  is a part (specifically, an upper part) of the coupling portion  50  at the side closer to the loading portion  30  in the up-down direction Z. The upper coupling portion  52  is provided between the loading portion  30  and the spring portion  51  so as to connect the loading portion  30  and the upper part of the spring portion  51 . The upper coupling portion  52  has a function of a universal joint. 
     Lower Coupling Portion  53   
     The lower coupling portion  53  is a part (specifically, a lower part) of the coupling portion  50  at the side closer to the base portion  40  in the up-down direction Z. The lower coupling portion  53  is provided between the base portion  40  and the spring portion  51  so as to couple the base portion  40  (specifically, a bottom wall  45  of the coupling recess  43 ) and the lower end of the spring portion  51 . The lower coupling portion  53  has a function of a universal joint. 
     Operation of Coupling Portion  50   
     When the vehicle  20  travels, an inertial force acts on the seat  21  of the vehicle  20  and the occupant seated on the seat  21  as the vehicle  20  accelerates, decelerates, turns, or travels on a bumpy road. In such cases, the guide portions  42  in the seat  21  of the present embodiment allow for relative movement between the loading portion  30  and the base portion  40  of the seat  21 . In addition, when the loading portion  30  and the base portion  40  move relative to each other in the seat  21  of the present embodiment, the spring portion  51  of the coupling portion  50  extends or contracts so that the compression coil spring in the spring portion  51  is elastically deformed. This attenuates the inertial force acting on the loading portion  30  of the seat  21 . 
       FIG.  4    illustrates an example of a manner in which the coupling portion  50  operates during traveling of the vehicle  20 . 
     When the vehicle  20  decelerates, an inertial force acts on the seat  21  in such a manner that the loading portion  30  moves forward. In the example shown in  FIG.  4   , at the time of deceleration of the vehicle  20 , the guide portions  42  allow the seat portion  30 S of the loading portion  30  to be moved to the front side (left side in  FIG.  4   ) of the seat  21  with respect to the base portion  40 . At this time, the upper coupling portion  52 , which is coupled to the loading portion  30 , is pulled by the loading portion  30 , so that the spring portion  51  falls toward the front side of the seat  21  as indicated by arrow A in  FIG.  4   . Since the spring portion  51  extends, the compression coil spring inside the spring portion  51  is elastically deformed in the compression direction. Thereafter, when the inertial force acting on the loading portion  30  decreases, the compression coil spring in the spring portion  51  is restored to its original length (length prior to the compression deformation), and the spring portion  51  is restored to its original length (length prior to the extension). Accordingly, the relative positions of the loading portion  30  and the base portion  40  also return to their original positions (positions prior to the movement); specifically, the positions (the positions shown in  FIG.  1   ) before the inertial force associated with the deceleration of the vehicle  20  acts on the loading portion  30 . 
     In the seat  21  of the present embodiment, when the vehicle  20  travels, relative movement between the loading portion  30  and the base portion  40  is allowed in all directions. For example, when the vehicle  20  is accelerated, the seat portion  30 S of the loading portion  30  moves toward the rear side of the seat  21  with respect to the base portion  40 . Also, when the vehicle  20  turns right, the seat portion  30 S of the loading portion  30  moves toward the left side of the seat  21  with respect to the base portion  40 . When the vehicle  20  turns left, the seat portion  30 S of the loading portion  30  moves toward the right side of the seat  21  with respect to the base portion  40 . In the seat  21  of the present embodiment, even when the loading portion  30  and the base portion  40  move relative to each other in any direction during traveling of the vehicle  20 , the spring portion  51  of the coupling portion  50  extends or contracts to attenuate the inertial force acting on the loading portion  30  of the seat  21 . 
     Rotational Position Changing Mechanism  60   
     As shown in  FIGS.  1  and  3   , the vehicle  20  includes a rotational position changing mechanism  60 . The rotational position changing mechanism  60  operates to cause the seat  21  as a whole (the loading portion  30 , the base portion  40 , and the coupling portion  50 ) to integrally rotate relative to the vehicle body  22  about a rotation axis extending in the up-down direction Z. 
     The rotational position changing mechanism  60  includes a support portion  61 . The support portion  61  is provided on the vehicle body  22  and has a cylindrical shape that protrudes and extends upward. In the present embodiment, the lower part of the base portion  40  is accommodated inside the support portion  61  such that the inner peripheral surface of the support portion  61  and the outer peripheral surface of the base portion  40  of the seat  21  face each other. 
     The rotational position changing mechanism  60  includes multiple (in the present embodiment, six) bearing portions  62 . Each bearing portion  62  includes a rotation shaft  62 A, which extends in the up-down direction Z, and a cylindrical rotary portion  62 B, which is rotatably provided around the rotation shaft  62 A. The base portion  40  includes a groove (bearing groove  44 ) on the outer peripheral surface of the lower part. The bearing groove  44  extends over the entire circumference. In the present embodiment, the rotation shafts  62 A of the bearing portion portions  62  are fixed to the upper end of the support portion  61  in a state in which the outer peripheral part of the rotary portion  62 B of each bearing portion  62  is fit in the bearing groove  44  of the base portion  40 . In this manner, the bearing portions  62  are disposed between the support portion  61  and the base portion  40 . The bearing portions  62  attach the base portion  40  to the support portion  61  in a manner in which the base portion  40  is rotatable inside the support portion  61  and in a manner in which the base portion  40  cannot escape from the inside of the support portion  61 . 
     The rotational position changing mechanism  60  includes a rack  63 , which is provided on the base portion  40 , and a pinion  64 , which meshes with the rack  63 . The rack  63  is provided on the outer peripheral surface of the base portion  40  so as to extend in the circumferential direction. The pinion  64  is provided on the vehicle body  22  ( FIG.  1   ). The vehicle body  22  is provided with an electric motor (hereinafter, referred to as a rotational position changing motor  65 ) for rotating the pinion  64 , a controlling device  66  configured to control operation of the rotational position changing motor  65 , and a rotational operation switch  67 . The rotational operation switch  67  is operated by an occupant when rotating the seat  21 . Output signals of the rotational operation switch  67  are received by the controlling device  66 . The controlling device  66  may be circuitry including: 1) one or more processors that operate according to a computer program (software); 2) one or more dedicated hardware circuits (application specific integrated circuits: ASIC) that execute at least part of various processes; or 3) a combination thereof. The processor includes a central processing unit (CPU) and memories such as a random-access memory (RAM) and a read-only memory (ROM). The memories store program codes or commands configured to cause the CPU to execute processes. The memory, which is a computer-readable medium, includes any type of media that are accessible by general-purpose computers and dedicated computers. 
     Operation of Rotational Position Changing Mechanism  60   
     The rotational position changing mechanism  60  operates in the following manner. When the rotational operation switch  67  is operated by the occupant, the controlling device  66  causes the rotational position changing motor  65  to rotate. Accordingly, the rotational position changing mechanism  60  operates to cause the base portion  40  to rotate, relative to the vehicle body  22 , together with the coupling portion  50  and the loading portion  30 , which are integrated with the base portion  40 . 
     Coupling Position Changing Mechanism  70   
     As shown in  FIGS.  1  and  2   , the vehicle  20  includes a coupling position changing mechanism  70 . The coupling position changing mechanism  70  operates to change the coupling position at which the coupling portion  50  is coupled to the loading portion  30  of the seat  21  in a front-rear direction Y of the seat  21  (specifically, in the front-rear direction of the occupant seated on the seat  21 ). 
     Hereinafter, a specific structure of the coupling position changing mechanism  70  will be described. 
     The loading portion  30  of the seat  21  includes a seat body  31  and a movable portion  32 . 
     The seat body  31  forms a majority part of the loading portion  30 . The seat body  31  includes a receiving hole  34  at a position that corresponds to the support surface  33 A. The receiving hole  34  extends from the lower surface of the seat portion  30 S to the back surface of the backrest portion  30 B. The receiving hole  34  has an arcuate cross section and extends in the front-rear direction Y of the seat  21 . The depth and the width in the extending direction of the receiving hole  34  are substantially constant. 
     The movable portion  32  has an arcuate cross section and extends in the front-rear direction Y of the seat  21 . In the present embodiment, the movable portion  32  is received in the receiving hole  34  of the seat body  31  such that the outer surface of the movable portion  32  and the outer surface of the seat body  31  are substantially flush with each other, and these outer surfaces form the support surface  33 A. 
     A slide mechanism (not shown) is provided between the receiving hole  34  of the seat body  31  and the movable portion  32 . The movable portion  32  is attached to the receiving hole  34  with the slide mechanism in a state in which the movable portion  32  can reciprocate in the front-rear direction Y inside the receiving hole  34 , but cannot escape from the inside of the receiving hole  34 . In the present embodiment, the upper end of the coupling portion  50  (specifically, the upper coupling portion  52 ) is fixed to the movable portion  32 . 
     The coupling position changing mechanism  70  includes a rack  71 , which is provided on the seat body  31 , and a pinion  72  ( FIG.  1   ), which meshes with the rack  71 . The rack  71  is provided on the bottom surface of the receiving hole  34  so as to extend in the front-rear direction Y of the seat  21 . The pinion  72  is provided inside the movable portion  32 . The movable portion  32  incorporates an electric motor (hereinafter, referred to as a coupling position changing motor  73 ) for rotating the pinion  72 , and a controlling device  74  configured to control operation of the coupling position changing motor  73 . The controlling device  74  may be circuitry including: 1) one or more processors that operate according to a computer program (software); 2) one or more dedicated hardware circuits (application specific integrated circuits: ASIC) that execute at least part of various processes; or 3) a combination thereof. The processor includes a central processing unit (CPU) and memories such as a random-access memory (RAM) and a read-only memory (ROM). The memories store program codes or commands configured to cause the CPU to execute processes. The memory, which is a computer-readable medium, includes any type of media that are accessible by general-purpose computers and dedicated computers. A coupling operation switch  75  is attached to a vehicle body  22 . The coupling operation switch  75  is operated by the occupant when changing the inclination angle (position) of the loading portion  30  of the seat  21  in the front-rear direction Y. Output signals of the coupling operation switch  75  are received by the controlling device  74 . 
     Operation of Coupling Position Changing Mechanism  70   
     The coupling position changing mechanism  70  operates in the following manner. 
     When the coupling operation switch  75  is operated by the occupant, the controlling device  74  causes the coupling position changing motor  73  to rotate. This causes the coupling position changing mechanism  70  to operate, so that the movable portion  32  and the seat body  31  move relative to each other in the front-rear direction Y of the seat  21 . The movable portion  32  is coupled to the base portion  40  by the coupling portion  50 . Therefore, when the movable portion  32  and the seat body  31  move relative to each other, the coupling portion  50  normally remains at the current position and the seat body  31  moves in the front-rear direction Y. This changes the position of the loading portion  30  (specifically, the seat body  31 ) of the seat  21  in the front-rear direction Y. 
       FIG.  5    illustrates an example of an operation of the coupling position changing mechanism  70  when the seat body  31  is moved forward (indicated by arrow B in the drawing) with respect to the movable portion  32  of the seat  21 . In this case, the front end of the seat portion  30 S is raised, and the backrest portion  30 B is tilted rearward as shown in  FIG.  5   . 
     When the seat body  31  is moved rearward with respect to the movable portion  32  of the seat  21 , the front end of the seat portion  30 S is lowered and the backrest portion  30 B is raised and moved forward. 
     In the present embodiment, the rotational position changing mechanism  60  operates to change the position of the seat  21  (specifically, the seat body  31 ) in a default state, in which no inertial force is acting on the loading portion  30 . 
     The present embodiment has the following advantages. 
     (1-1) The seat  21  includes the loading portion  30 , the base portion  40 , and the coupling portion  50 . The loading portion  30  is provided in the upper part of the base portion  40  such that the support surface  33 A of the lower convex portion  33  of the loading portion  30  faces the inner surface of the upper concave portion  41  of the base portion  40 . The coupling portion  50  includes the spring portion  51  and couples the base portion  40  and the loading portion  30  to each other with the spring portion  51  between them. The support surface  33 A of the lower convex portion  33  of the loading portion  30  has a spherical surface. The inner surface of the upper concave portion  41  of the base portion  40  includes the guide portions  42 . The guide portions  42  guide the base portion  40  and the loading portion  30  such that the base portion  40  and the loading portion  30  move relative to each other in a direction along the support surface  33 A of the lower convex portion  33 , which has a spherical surface. 
     As described above, when the vehicle  20  travels, an inertial force acts on the seat  21  and the occupant seated on the seat  21 . According to the present embodiment, when such an inertial force is generated, the guide portions  42  allow the loading portion  30  and the base portion  40  of the seat  21  to move relative to each other. When the loading portion  30  and the base portion  40  are moved relative to each other, the spring portion  51  of the coupling portion  50  extends or contracts so as to attenuate the inertial force acting on the loading portion  30  of the seat  21 . This reduces the shock acting on the loading portion  30 , stabilizing the position of the loading portion  30  and the position of the occupant seated on the loading portion  30 . 
     (1-2) The seat  21  is provided with the coupling position changing mechanism  70 , which is configured to change the coupling position at which the coupling portion  50  is coupled to the loading portion  30 . When the coupling position changing mechanism  70  operates through operation of the coupling operation switch  75  by the occupant, the relative positions of the base portion  40  and the loading portion  30  in the default state, in which no inertial force is acting on the loading portion  30 , is changed. 
     According to the present embodiment, the coupling position changing mechanism  70  operates to allow the position of the loading portion  30  in the default state (hereinafter referred to as a default position) to be set such that the seating surface of the seat portion  30 S is horizontal as shown in  FIG.  1   . Further, as shown in the example in  FIG.  5   , it is also possible to set the default position of the loading portion  30  such that the seating surface of the seat portion  30 S is inclined in the front-rear direction Y. In this manner, the present embodiment allows the default position of the loading portion  30  to be set flexibly. 
     (1-3) The vehicle  20  is provided with the rotational position changing mechanism  60 . The rotational position changing mechanism  60  operates to cause the seat  21  as a whole to integrally rotate relative to the vehicle body  22  about the rotation axis extending in the up-down direction Z. 
     According to the present embodiment, it is possible to freely change the orientation (specifically, the rotational position) of the seat  21  about the rotation axis extending in the up-down direction Z by operating the rotational position changing mechanism  60  through operation of the rotational operation switch  67  by the occupant. This allows the default position of the loading portion  30  of the seat  21  to be set in a highly flexible manner. 
     Second Embodiment 
     A position controlling device according to a second embodiment will now be described with reference to  FIGS.  6  to  10   . Differences from the first embodiment will mainly be discussed. In the following description, among the components of the position controlling device according to the present embodiment, the same components as those of the position controlling device according to the first embodiment are denoted by the same reference numerals or corresponding reference numerals, and redundant description of the components is omitted. 
     Unlike the position controlling device of the first embodiment, the position controlling device of the present embodiment is not provided with the coupling position changing mechanism  70  (see  FIG.  1   ) or its peripheral devices. The position controlling device of the present embodiment is different from the position controlling device of the first embodiment in that it has a relative position changing mechanism that is driven in accordance with the moving state of the vehicle. 
     The relative position changing mechanism and the structure surrounding it will be described. 
     Loading Portion  130   
     As shown in  FIGS.  6  and  7   , a loading portion  130  of a seat  121  has a structure in which a seat portion  130 S and a backrest portion  130 B are formed integrally. The loading portion  130  includes a lower convex portion  133 , which includes a lower part of the seat portion  130 S and a back part of the backrest portion  130 B. An outer surface (hereinafter, referred to as a support surface  133 A) of the lower convex portion  133  has a spherical surface bulging in a direction away from the occupant seated on the loading portion  130 . The loading portion  130  of the present embodiment does not include movable parts, and is formed as an integral component as a whole. 
     Relative Position Changing Mechanism  80   
     As shown in  FIGS.  6  and  8   , the seat  121  is provided with a relative position changing mechanism  80 . The relative position changing mechanism  80  is provided between a lower coupling portion  53  of the coupling portion  150  and a bottom wall  45  of a coupling recess  43  of the base portion  40  so as to form a middle part of the coupling portion  150  in the up-down direction Z. The relative position changing mechanism  80  operates to displace the bottom wall  45  of the coupling recess  43  of the base portion  40  and the lower end of the lower coupling portion  53  from each other in a second direction intersecting the up-down direction Z (specifically, the second direction extends along a plane orthogonal to the up-down direction Z). In the present embodiment, the bottom wall  45  of the coupling recess  43  of the base portion  40 , to which one end of the relative position changing mechanism  80  in the up-down direction Z is coupled, corresponds to a part closer to the base portion, and the lower end of the lower coupling portion  53 , to which the other end of the relative position changing mechanism  80  is coupled, corresponds to a part closer to the loading portion. 
     Specifically, the relative position changing mechanism  80  includes a front-rear direction changing mechanism  81  and a lateral direction changing mechanism  85 . The front-rear direction changing mechanism  81  operates to shift the bottom wall  45  of the base portion  40  and the lower end of the lower coupling portion  53  in the front-rear direction Y of the seat  121 . The lateral direction changing mechanism  85  operates to shift the bottom wall  45  and the lower end of the lower coupling portion  53  in a lateral direction X of the seat  121 . 
     As shown in  FIG.  8   , a guide rail  82  is provided on the bottom wall  45  of the base portion  40  so as to extend in the front-rear direction Y of the seat  121 . A rectangular plate-shaped guide table  83  is attached to the bottom wall  45  of the base portion  40  with the guide rail  82  between the bottom wall  45  and the base portion guide table  83 . The guide table  83  is guided by the guide rail  82  so as to reciprocate in the front-rear direction Y with respect to the base portion  40 . The guide rail  82  and the guide table  83  form the front-rear direction changing mechanism  81 . 
     An electric motor (hereinafter, referred to as a front-rear direction motor  84 ), which serves as a drive unit, is connected to the guide table  83  via a gear mechanism (not shown). In the present embodiment, the guide table  83  is moved in the front-rear direction Y by driving the front-rear direction changing mechanism  81  through an operation control of the front-rear direction motor  84 . 
     A guide rail  86  is provided on the upper surface of the guide table  83  so as to extend in the lateral direction X of the seat  121 . A rectangular plate-shaped guide table  87  is attached to the upper surface of the guide table  83  with the guide rail  86  between the guide table  87  and the upper surface of the guide table  83 . The guide table  87  is guided by the guide rail  86  so as to reciprocate in the lateral direction X with respect to the base portion  40  (specifically, the guide table  83 ). The guide rail  86  and the guide table  87  form the lateral direction changing mechanism  85 . 
     An electric motor (hereinafter, referred to as a lateral direction motor  88 ), which serves as a drive unit, is connected to the guide table  87  via a gear mechanism (not shown). In the present embodiment, the guide table  87  is moved in the lateral direction by driving the lateral direction changing mechanism  85  through an operation control of the lateral direction motor  88 . 
     Controlling Device  90   
     As shown in  FIG.  6   , the vehicle  20  includes a controlling device  90  configured to execute the operation control of the front-rear direction motor  84  and the operation control of the lateral direction motor  88 . The controlling device  90  may be circuitry including: 1) one or more processors that operate according to a computer program (software); 2) one or more dedicated hardware circuits (application specific integrated circuits: ASIC) that execute at least part of various processes; or 3) a combination thereof. The processor includes a central processing unit (CPU) and memories such as a random-access memory (RAM) and a read-only memory (ROM). The memories store program codes or commands configured to cause the CPU to execute processes. The memory, which is a computer-readable medium, includes any type of media that are accessible by general-purpose computers and dedicated computers. The vehicle  20  is provided with various sensors that detect the behavior of the vehicle  20 , such as a gyroscope sensor  91  and an acceleration sensor  92 . Detection signals of various sensors are delivered to the controlling device  90 . The vehicle  20  is also provided with a navigation system  93 . In the present embodiment, the navigation system  93  outputs location information and map information as output signals that are received by the controlling device  90 . 
     The controlling device  90  performs various calculations based on the output signals of the various sensors and the output signals of the navigation system  93 , and performs operation control of the front-rear direction motor  84  and operation control of the lateral direction motor  88  based on the calculation results. In the present embodiment, the various sensors and the navigation system  93  correspond to an acquisition unit, the output signals of the various sensors and the output signals of the navigation system  93  correspond to information regarding a moving state of a mobile object, and the controlling device  90  corresponds to a control unit. 
     Operation of Relative Position Changing Mechanism  80   
     The relative position changing mechanism  80  operates in the following manner. 
     When the controlling device  90  performs an operation control of the front-rear direction motor  84  to operate the front-rear direction changing mechanism  81 , the lower part of the coupling portion  150  moves in the front-rear direction Y with respect to the base portion  40 . At this time, the loading portion  130  of the seat  121  is pulled by the coupling portion  150 , which is coupled to the loading portion  130 , so as to move in the front-rear direction Y together with the coupling portion  150 . This moves the loading portion  130  of the seat  121  in a direction along the outer surface of the spherical lower convex portion  133 . 
       FIG.  9    illustrates an example of a manner in which the position of the loading portion  130  of the seat  121  is changed when the front-rear direction changing mechanism  81  operates to move the guide table  83  and the coupling portion  150  forward. The long-dash double-short-dash line in  FIG.  9    represents the default position of the loading portion  130  of the seat  121 , and the solid line in  FIG.  9    represents the position of the loading portion  130  of the seat  121  when the front-rear direction changing mechanism  81  operates. In  FIG.  9   , the amounts of movements of the guide table  83 , the coupling portion  150 , and the loading portion  130  are exaggerated in order to facilitate understanding. 
     As shown in  FIG.  9   , when the front-rear direction changing mechanism  81  operates to move the guide table  83  and the coupling portion  150  forward, the front end of the seat portion  130 S of the seat  121  is raised (the state represented by the solid line in the drawing) and the backrest portion  130 B is tilted rearward. 
     When the front-rear direction changing mechanism  81  operates to move the guide table  83  and the coupling portion  150  rearward with respect to the base portion  40 , the front end of the seat portion  130 S of the seat  121  is lowered and the backrest portion  130 B is raised in a forward direction. 
     In addition, when the operation control of the lateral direction motor  88  is performed by the controlling device  90  to operate the lateral direction changing mechanism  85 , the lower part of the coupling portion  150  moves in the lateral direction X with respect to the base portion  40 . At this time, the loading portion  130  of the seat  121  is pulled by the coupling portion  150  coupled to the loading portion  130  so as to move in the lateral direction X together with the coupling portion  150 . This moves the loading portion  130  of the seat  121  in a direction along the outer surface of the spherical lower convex portion  33 . 
       FIG.  10    illustrates an example of a manner in which the position of the loading portion  130  of the seat  121  is changed when the lateral direction changing mechanism  85  operates to move the guide table  87  and the coupling portion  150  forward. The long-dash double-short-dash line in  FIG.  10    represents the default position of the loading portion  130  of the seat  121 , and the solid line in  FIG.  10    represents the position of the loading portion  130  of the seat  121  when the lateral direction changing mechanism  85  operates. In  FIG.  10   , the amounts of movements of the guide table  87 , the coupling portion  150 , and the loading portion  130  are exaggerated in order to facilitate understanding. 
     As shown in  FIG.  10   , when the lateral direction changing mechanism  85  operates to move the guide table  87  and the coupling portion  150  leftward with respect to the base portion  40 , the seating surface of the seat portion  130 S is inclined such that the left side of the seat portion  130 S is raised. 
     When the lateral direction changing mechanism  85  operates to move the guide table  87  and the coupling portion  50  rightward with respect to the base portion  40 , the seating surface of the seat portion  130 S is inclined such that the right side of the seat portion  130 S is raised. 
     In the present embodiment, when the controlling device  90  simultaneously performs the operation control of the front-rear direction motor  84  and the operation control of the lateral direction motor  88 , the front-rear direction changing mechanism  81  and the lateral direction changing mechanism  85  operate in combination. In this case, the coupling portion  150  can be moved in any direction with respect to the base portion  40 . Thus, the loading portion  130  of the seat  121  can also be moved in any direction together with the coupling portion  150  by being pulled by the coupling portion  150  coupled to the loading portion  130 . 
     The controlling device  90  performs the operation control of the front-rear direction motor  84  and the operation control of the lateral direction motor  88  in the following manner. 
     Control Example 1 
     The loading portion  130  is moved in accordance with the actual behavior of the vehicle  20 , so as to cancel the shock applied to the seat  121 . 
     For example, when deceleration of the vehicle  20  is detected, the front-rear direction changing mechanism  81  operates in accordance with the deceleration to move the coupling portion  150  forward. In this case, since the loading portion  130  of the seat  121  is pulled and moved forward in accordance with the deceleration of the vehicle  20 , the shock applied to the seat  121  and the occupant on the seat  121  is reduced. 
     In addition, when a right turn of the vehicle  20  is detected, the lateral direction changing mechanism  85  operates in accordance with the right turn to move the coupling portion  50  leftward. In this case, since the loading portion  130  of the seat  121  is pulled and moved rightward in accordance with the right turn of the vehicle  20 , the shock applied to the seat  121  and the occupant is reduced. 
     Control Example 2 
     The moving state of the vehicle  20  is predicted based on information (location information and map information) acquired from the navigation system  93 , and the position of the loading portion  30  is controlled in accordance with the predicted moving state. 
     For example, at a time at which the vehicle  20  is predicted to reach a corner, the lateral direction changing mechanism  85  operates to move the coupling portion  50  outward with respect to the turning direction. In this case, when the vehicle  20  is about to turn, the position of the seat  121  and the position of the occupant seated on the seat  121  are set to positions tilted inward with respect to the turning direction in advance in preparation for the turn of the vehicle  20 . 
     The present embodiment has the following advantages. 
     (2-1) The seat  121  is provided with the relative position changing mechanism  80 . The relative position changing mechanism  80  operates to displace the bottom wall  45  of the coupling recess  43  of the base portion  40  and the lower end of the lower coupling portion  53  from each other in the second direction, which intersects the up-down direction Z. The vehicle  20  is provided with the front-rear direction motor  84  and the lateral direction motor  88 , which drive the relative position changing mechanism  80 , and the controlling device  90 , which performs the operation control of the motors  84 ,  88 . The vehicle  20  is provided with the various sensors and the navigation system  93 , which are used to acquire information regarding the moving state of the vehicle  20 . The controlling device  90  performs the operation control of the motors  84 ,  88  based on information regarding the moving state of the vehicle  20 , which is acquired from the various sensors and the navigation system  93 , thereby causing the relative position changing mechanism  80  to operate. 
     According to the present embodiment, it is possible to control the position of the loading portion  130  of the seat  121  in a highly flexible manner. For example, the position of the loading portion  130  can be controlled in accordance with the actual traveling state of the vehicle  20 . Also, the position of the loading portion  130  can be controlled in advance in accordance with a predicted moving state of the vehicle  20 . Therefore, it is possible to finely control the position of the seat  121  and the position of the occupant seated on the seat  121  in accordance with the situation. 
     (2-2) The present embodiment achieves the same advantages as the advantages described in the above-described items (1-1) and (1-3). 
     Other Embodiments 
     The above-described embodiments may be modified as follows. The above-described embodiments and the following modifications can be combined as long as the combined modifications remain technically consistent with each other. 
     In the first embodiment, the coupling position changing mechanism  70  is not limited to a rack-and-pinion mechanism including the rack  71  provided on the seat body  31  and the pinion  72  provided on the movable portion  32 , but may be any mechanism. That is, any mechanism can be used as a coupling position changing mechanism as long as it has a structure capable of changing the coupling position at which the coupling portion  50  is coupled to the loading portion  30 . 
       FIG.  11    shows a coupling position changing mechanism  270  as an example. As shown in  FIG.  11   , a hook  276  in this example is provided at an end portion of the upper coupling portion  52  of a coupling portion  250  at the side closer to a loading portion  230 . The loading portion  230  includes a through-hole  235 . The coupling portion  250  is inserted into the through-hole  235 . The loading portion  230  includes recesses (hereinafter referred to as locking recesses  236 ) at the upper edge of the through-hole  235 . The hook  276  is hooked to any of the locking recess  236 . The locking recesses  236  are provided at multiple locations (seven locations in this example) so as to be arranged at intervals in the front-rear direction Y. In the coupling position changing mechanism  270  of the present example, the hook  276  of the coupling portion  250  is hooked to selected one of the locking recesses  236 , so as to adjust the position of the loading portion  230  in the front-rear direction Y in multiple stages. 
     In the first embodiment, the coupling position changing mechanism  70  has a structure capable of changing the coupling position at which the coupling portion  50  is coupled to the loading portion  30 . However, the present disclosure is not limited thereto. For example, a mechanism may be used that is capable of changing the coupling position at which the coupling portion  50  is coupled to the base portion  40 . 
     In the first embodiment, the base portion  40  of the seat  21  may be fixed to the vehicle body  22 . In this case, as a rotational position changing mechanism, it is possible to provide a mechanism that causes the coupling position changing mechanism  70 , the loading portion  30 , and the coupling portion  50  to integrally rotate relative to the base portion  40  about a rotation axis extending in the up-down direction Z. With this configuration, the loading portion  30  of the seat  21  can be rotated with respect to the vehicle body  22  about a rotation axis extending in the up-down direction Z by causing the rotational position changing mechanism to operate. 
     In the second embodiment, the operation control of the rotational position changing motor  65 , which corresponds to the rotational position changing mechanism  60 , may be performed together with the operation control of the motors  84 ,  88 , which correspond to the relative position changing mechanism  80 , based on information regarding the moving state of the vehicle  20 . With this configuration, it is possible to control the orientation of the seat  121  about the rotation axis extending in the up-down direction Z in addition to controlling the position of the seat  121  in the front-rear direction Y and the lateral direction X. This allows the position of the loading portion  130  of the seat  121  to be controlled in a highly flexible manner. 
     In the second embodiment, any suitable device, for example, a camera, a radar sensor, or a LiDAR sensor may be used as the acquisition unit for acquiring the information regarding the moving state of the vehicle  20 . 
     In the second embodiment, the arrangement position of the relative position changing mechanism  80  may be set to any position as long as the relative position changing mechanism  80  forms a middle part of the coupling portion  50  in the up-down direction Z. For example, the relative position changing mechanism  80  may be provided between the lower coupling portion  53  and the spring portion  51  or between the upper coupling portion  52  and the loading portion  130 . 
     In the second embodiment, the drive unit that drives the relative position changing mechanism  80  may be a hydraulic actuator, a pneumatic actuator, or the like, instead of an electric motor. 
     In the second embodiment, one of the front-rear direction changing mechanism  81  and the lateral direction changing mechanism  85  may be omitted. 
     In the second embodiment, the relative position changing mechanism  80 , that is, both of the front-rear direction changing mechanism  81  and the lateral direction changing mechanism  85 , may be omitted. In this case, the lower end of the lower coupling portion  53  may be coupled to the bottom wall  45  of the base portion  40 . 
     In the second embodiment, the base portion  40  may be fixed to the vehicle body  22 . In this case, as a rotational position changing mechanism, it is possible to provide a mechanism that causes the loading portion  130  and the coupling portion  150  (including the relative position changing mechanism  80 ) to integrally rotate relative to the base portion  40  about a rotation axis extending in the up-down direction Z. With this configuration, the loading portion  130  of the seat  121  can be rotated with respect to the vehicle body  22  about a rotation axis extending in the up-down direction Z by causing the rotational position changing mechanism to operate. 
     In each of the embodiments, a part of the outer surface of the lower convex portion  33 ,  133  may have a shape other than a spherical surface. For example, an edge portion of the lower convex portion  33 ,  133  of the loading portion  30 ,  130  may have a shape other than a spherical surface. That is, the outer surface shape of the lower convex portion  33 ,  133  may be changed as long as all portions of the outer surface of the lower convex portion  33 ,  133  that are in contact with the respective guide portions  42  form the same spherical surface. 
     In each embodiment, the inner surface of the upper concave portion  41  of the base portion  40  is not limited to a substantially spherical surface, but may be formed in any shape. In addition, it is also possible to use a base portion  40  having a structure without the upper concave portion  41 . That is, the upper structure of the base portion  40  may be changed as long as the guide portions  42  can be arranged such that the portions of the guide portions  42  in contact with the lower convex portion  33 ,  133  are aligned on the same spherical surface. 
     In each of the embodiments, the guide portions  42  may be provided in the lower convex portion  33  of the loading portion  30  instead of being provided in the upper concave portion  41  of the base portion  40 . In this configuration, the inner surface of the upper concave portion  41  of the base portion  40  may be formed into a substantially spherical surface. In this configuration, the inner surface of the upper concave portion  41  corresponds to a surface that supports the loading portion  30 . Further, in the above-described configuration, the guide portions  42  may be disposed in the lower part of the loading portion  30  such that portions of the guide portions  42  that are in contact with the upper concave portion  41  are arranged on the same spherical surface. In this case, the part of the outer surface of the loading portion  30  below the seat portion  30 S and the back part of the backrest portion  30 B are not limited to being substantially spherical, but may be formed into any shape. 
     In each of the embodiments, the guide portions  42  are not limited to including the case  42 B and the contact ball  42 C, but may have any suitable structure. For example, the inner surface of the upper concave portion  41  of the base portion  40  may be formed into a spherical surface, and the inner surface of the upper concave portion  41  may be used as a guide portion. In this case, the loading portion  30 ,  130  may be provided on the base portion  40  such that the lower convex portion  33 ,  133  of the loading portion  30 ,  130  is received by the upper concave portion  41  of the base portion  40 . In this case, in order to improve sliding, it is preferable to supply (apply) a lubricant (oil, grease) or supply compressed air between the inner surface of the upper concave portion  41  of the base portion  40  and the outer surface of the lower convex portion  33 ,  133  of the loading portion  30 ,  130 . 
     In each of the embodiments, the spring portion  51  may be a shock absorber in which the damping force in a compression direction is smaller than the damping force in an extension direction, in place of a type incorporating a compression coil spring. 
     In each of the embodiments, the structure of the rotational position changing mechanism  60  may be changed as long as the structure causes the seat  21 ,  121  to integrally rotate relative to the vehicle body  22 . For example, a rotational position changing mechanism may be used that includes a rack provided on the inner peripheral surface of the support portion  61  and a pinion rotatably provided on the base portion  40  to mesh with the rack. 
     In each of the embodiments, a manually operated type may be provided as the rotational position changing mechanism  60 . 
     In each of the embodiments, the rotational position changing mechanism  60  may be omitted. 
     The position controlling device according to each of the embodiments can also be used as a position controlling device for a mobile object other than an automobile, such as a position controlling device for controlling the position of a seat provided in a wheelchair and a position controlling device for controlling the position of a loading platform provided in an automatic guided vehicle. 
     If the position controlling device according to each of the embodiments is used in a wheelchair, the position of the seat (specifically, the loading portion thereof) and thus the position of the user seated on the seat are stabilized. 
       FIG.  12    illustrates an example of the structure of a loading platform in a case in which the position controlling device according to each of the embodiments is used in an automatic guided vehicle. As shown in  FIG.  12   , a loading platform  321  includes a base portion  40  and a loading portion  330 . An upper part of the loading portion  330  is a flat plate portion  330 S having a flat plate shape. A lower part of the loading portion  330  is a lower convex portion  333 , which has a spherical outer surface. The loading portion  330  is provided on the upper part of the base portion  40  such that the outer surface of the lower convex portion  333  of the loading portion  330  and the inner surface of the upper concave portion  41  of the base unit  40  face each other. With this configuration, the shock acting on the loading portion  330  is reduced, the position of the loading portion  330  and thus the position of the cargo loaded on the loading portion  330  are stabilized. 
     Although the multiple embodiments have been described herein, it will be clear to those skilled in the art that the present disclosure may be embodied in different specific forms without departing from the spirit of the disclosure. The disclosure is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims.