Patent Publication Number: US-2021179403-A1

Title: Omnidirectional Cart Transport Mechanism

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This nonprovisional application claims priority under 35 U.S.C. § 119(a) on Patent Application No. 2019-226567 filed in Japan on Dec. 16, 2019, the entire contents of which are hereby incorporated by reference. 
     FIELD 
     The present application relates to an omnidirectional cart transport mechanism capable of traveling while easily integrating a cart with an automatic guided vehicle (AGV) and easily uncoupling the cart from the AGV. 
     BACKGROUND 
     Japanese Patent Application Laid-Open No. 2019-89493 discloses a drive wheel with a simple structure and a cart. The drive wheel disclosed herein comprises a first input bevel gear, a first driving unit for rotating the first input bevel gear and a second input bevel gear disposed opposite the first input bevel gear and rotatable around a rotary shaft of the first input bevel gear. The drive wheel further comprises a second driving unit for rotating the second input bevel gear, a first output bevel gear meshing with each of the first input bevel gear and the second input bevel gear and a wheel positioned at a spacing from the first output bevel gear. It further comprises a connection part connecting the first output bevel gear and the wheel and transmitting rotation of the first output bevel gear to the wheel, and a steering arm for rotating the connection part around the rotary shaft of the first input bevel gear. 
     Japanese Patent No. 6578063 discloses a towing device for an automatic guided vehicle and an automatic guided vehicle with the towing device. The automatic guided vehicle is provided with the towing device for preventing a decline in steerability when the automatic guided vehicle tows a cart. The towing device includes a connecting member having one end that is connected to the automatic guided vehicle swivelably (pivotally, rotatably) around the swivel (pivot, rotary, rotating, turning) shaft of the drive wheels and the other end that is connected to the cart. 
     Japanese Patent No. 3791663 discloses a drive wheel and a cart, and further discloses an omnidirectional vehicle including a body, a steering shaft attached to the body, an actuator for driving the steering shaft, a drive wheel, and an actuator for driving a drive wheel shaft, and further discloses the omnidirectional moving vehicle that may also be called a single wheel omnidirectional moving caster for driving the drive wheel with two motors. 
     Japanese Patent No. 5376347 discloses a steerable drive mechanism and an omnidirectional moving vehicle and makes a single wheel steerable by differential driving. The steerable drive mechanism includes a rotatable steering unit and a drive member rotating about an axis extending along a center axis of the steering unit. The steerable drive mechanism further includes an output shaft located at a position eccentric from the center axis of the steering unit and transmitting rotational force obtained from the drive member to the wheel. 
     Japanese Patent Application Laid-Open No. 2018-2320 discloses a traveling type transfer device which enables normal transfer regardless of shapes of packages. Disclosed here is a placement part on which a package is placed, an arm device including base arms provided at the placement part and extension arms which extend from the base arms to lateral sides of the package, and hooks provided at the tips of the extension arms. 
     Japanese Patent Application Laid-Open No. 2019-177836 discloses an automated guided vehicle that allows an operator to manually connect an object to the automated guided vehicle and to automatically move the object and automatically release the connected sate with the object. 
     SUMMARY 
     An omnidirectional cart transport mechanism according to the present application relates to a technical concept disclosed in the above-described patent documents. For example, for a loading type AGV, dedicated equipment for loading or unloading is required. Meanwhile, for a tractor type AGV that tows a cart to be handled by an operator, a travel path with a wide area is required. 
     It is an object of the present application to provide a practical omnidirectional cart transport mechanism taking into account the dimensions of the cart that is currently used and the dimensions of a container to be loaded thereon, a housing box, a food tray, etc. while eliminating the need for a dedicated loading or unloading device and enabling the use of carts currently used by an operator as they are to carry various commodities and semi-finished products. Moreover, another object is to enable easy coupling (integration) of the cart to the AGV and uncoupling one from the other, and to further enable easy traveling and change of direction, for example, in a relatively narrow space. 
     In addition, another object is to provide an omnidirectional cart transport mechanism capable of securely and stably traveling even on a road surface with a puddle. 
     An omnidirectional cart transport mechanism according to one embodiment of the present application includes an automatic guided vehicle that includes a drive wheel and a drive mechanism for driving the drive wheel, and travels on a road surface by driving the drive wheel using the drive mechanism, a side guide mechanism that includes a pair of side plates movable in a first direction of approaching or separating from each other, and guides a cart to be coupled to the automatic guided vehicle to a coupled position by bringing the pair of side plates closer to each other with the cart positioned between the pair of side plates, and a cart lift mechanism that lifts a coupled portion of the cart guided to the coupled position. 
     In the omnidirectional cart transport mechanism according to the present application, it is possible to easily and surely integrate the automatic guided vehicle with the cart and release (uncouple) the integration regardless of their relatively simple structure and configuration. Furthermore, a turning radius during traveling that used to occur when an automatic guided vehicle tows a cart can be reduced, which eliminates the need for newly providing a wide travel lane specifically designed to the automatic guided vehicle and enables traveling in a relatively small passage through which a worker has conventionally passed for transporting a cart. 
     The above and further objects and features of the invention will more fully be apparent from the following detailed description with accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is an entire perspective view of an omnidirectional cart transport mechanism according to one embodiment of the present application. 
         FIG. 2  is a schematic diagram obtained when an automatic guided vehicle illustrated in  FIG. 1  is viewed from the back. 
         FIG. 3  is a schematic diagram obtained when the omnidirectional cart transport mechanism illustrated in  FIG. 1  is viewed from the bottom. 
         FIG. 4  is a top view of the omnidirectional cart transport mechanism illustrated in  FIG. 1  viewed from the top when a side guide mechanism as a part thereof does not hold a cart. 
         FIG. 5  is a top view of the omnidirectional cart transport mechanism illustrated in  FIG. 1  viewed from the top when the side guide mechanism as a part thereof holds the cart. 
         FIG. 6  is a schematic perspective view obtained when an automatic guided vehicle (AGV) as a part of the omnidirectional cart transport mechanism illustrated in  FIG. 1  is viewed from the bottom to the top. 
         FIG. 7  is a schematic perspective view depicting a positional relation between the side guide mechanism and a cart lift mechanism according to the present application when both of the mechanisms are not activated. 
         FIG. 8  is a schematic perspective view depicting a positional relation between the side guide mechanism and the cart lift mechanism illustrated in  FIG. 7  when the side guide mechanism is placed in an inactivated state while the cart lift mechanism is lifted and activated. 
         FIG. 9  is a schematic perspective view depicting a positional relation between the side guide mechanism and the cart lift mechanism illustrated in  FIG. 7  when both of the mechanisms are activated. 
         FIG. 10  is a schematic side view depicting a positional relation between the cart lift mechanism and the cart when the cart lift mechanism illustrated in  FIG. 7  is placed in an inactivated state. 
         FIG. 11  is a schematic side view depicting a positional relation between the cart lift mechanism and the cart when the cart lift mechanism illustrated in  FIG. 10  is activated. 
         FIG. 12  is a schematic perspective view of an omnidirectional travel caster to be used in one embodiment of the present application. 
         FIG. 13  is a detailed perspective view illustrating the side guide mechanism illustrated in  FIGS. 7 to 9 . 
         FIG. 14  is a detailed perspective view illustrating the cart lift mechanism illustrated in  FIGS. 7 to 11 . 
         FIG. 15  is a table depicting examples of the dimensions of container carts (platform carts) that are currently used. 
         FIG. 16  is a table depicting examples of the dimensions of handle carts that are currently used. 
         FIG. 17  is a table depicting examples of the dimensions of containers that are currently used. 
         FIG. 18  is a schematic view illustrating a schematic posture when the omnidirectional cart transport mechanism illustrated in  FIG. 1  goes straight and turns on a travel path. 
         FIG. 19  is a schematic diagram illustrating a behavior until the omnidirectional cart transport mechanism illustrated in  FIG. 1  places loads in a preset container housing area. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Before describing one embodiment of the present application, matters related to the present application are described in advance with reference to “vocabulary of automatic guided vehicle systems” defined by D6801:2019 Japanese Industrial Standards (JIS). 
     According to JIS D6801:2019, an “automatic guided vehicle” is defined as a vehicle that has a function of automatically traveling in a preset area and transporting products such as loads except for a person, and that is not used on a road defined by the Road Traffic Law.” 
     Furthermore, the “automatic guided vehicle” is classified into three: a general classification (1), a classification by a transfer system (2), and a classification by an automatic travel system (3). 
     Note that the above-described general classification (1) includes the following three types. 
     1101 Loader Type: this is a type of transporting a load placed on an automatic guided vehicle. 
     1102 Tractor Type: this is a type of transporting a load by towing a cart or a trolley on which a load is stacked. Some of the tractor types tow a cart like a train and others tow a cart from beneath. 
     1103 Fork Lift Truck Type: this is one of the loader type, and is provided with a fork for transfer and a mast for elevating or lowering the fork and is a type of transporting a load using them. The classification and the terms related to a forklift refer to JISD6201. 
     Moreover, the above-described classification by a transfer system (2) includes two types: an automatic transfer system and a manual transfer system while the above-described classification by an automatic travel system (3) includes three types: a path guide system, a self-navigation system and a target guided system. 
     The omnidirectional cart transport mechanism disclosed herein cannot be specified as any one of the three types of the above-described general classification (1) of the “automatic guided vehicle” and can be said to have all the functions of the three types as will be described later. Additionally, in terms of the above-described classification by an automatic travel system (3), this omnidirectional cart transport mechanism corresponds to the self-navigation system. 
     It is noted that a cart herein is “a platform with wheels for carrying products,” and the cart includes a platform cart without a hand-operated handle, a hand cart with a hand-operated handle, a foldable cart, a container cart on which a container for housing products therein is placed, a cage cart and the like. 
       FIG. 1  is an entire perspective view of an omnidirectional cart transport mechanism  1  according to one embodiment of the present application. Broadly speaking, the omnidirectional cart transport mechanism  1  includes an automatic guided vehicle (hereinafter referred to as an AGV)  10 , a cart  40  and an integration mechanism (side guide mechanism  20  and cart lift mechanism  30  to be described later) for integrating the AGV  10  with the cart  40 . The integration mechanism will be described later. The cart  40  illustrated in  FIG. 1  is generally called a platform cart or a container cart, which is a so-called cart without a hand-operated handle. Briefly discussing the structure and/or configuration of the cart  40 , the cart  40  is constructed by a combination of a frame member  40   f  and corner members  40   c  provided with cart casters  444 , and is substantially quadrangular in plan view. On the cart  40 , several number of stacked containers (including pallets, trays, food trays, or the like)  42  are loaded. Each of the container  42  contains various commodities such as foods and industrial products, semi-finished products thereof, raw materials, etc. 
     The AGV  10  includes an operation/display unit  102 , a control unit  104 , a controller  106 , a power supply unit  108 , an electromagnetic contactor  112 , a battery  114 , a laser distance sensor  116 , a bumper switch  118 , a power switch  122 , a drive wheel  164 , etc. The drive wheel  164  is a wheel rotated by transmission of power output from servo motors  160  (see  FIG. 12 ) to be described later to cause the AGV  10  to travel. The drive wheel  164  is an omnidirectional moving wheel, and is driven by the servo motors  160  to cause the AGV  10  to travel. 
     The operation/display unit  102  is disposed at the upper part of the AGV  10 , and is further provided with an antenna and a wireless module for performing wireless control as well as a battery gauge, a direction indicator, an emergency stop button and the like. The operation/display unit  102  is most often used by a worker or an operator of the AGV  10 . 
     The control unit  104  includes the controller  106 , the electromagnetic contactor  112 , etc. The controller  106  is constituted by a one-chip microcomputer, for example, and is provided with a microprocessor for processing information, a memory for storing information, an interface for exchanging information with an external device and the like. The controller  106  stores or registers map information and distance information previously storing information on a traveling route and a traveling distance, a traveling premises, a specific object within a building, etc. Furthermore, it can record or display the traveling route up to now and the current position of the omnidirectional cart transport mechanism  1 , and can further estimate a traveling route and a traveling distance up to a final destination. It is noted that the controller  106  has a function of issuing an instruction signal for controlling the rotation of the servo motors  160  (see  FIG. 12 ) as power sources of an omnidirectional moving caster  16  and for automatically coupling the AGV  10  to the cart  40  or uncoupling the AGV  10  from the cart  40  on the basis of detection information detected by the laser distance sensor (range sensor)  116  illustrated in  FIG. 1 , a detection signal detected by a sensor (laser distance sensor  116  between the AGV  10  and the cart  40  depicted in  FIG. 4 ) installed at the bottom of the omnidirectional cart transport mechanism  1 , and a signal output from an encoder  166  (see  FIG. 12 ) for detecting a rotational position (angle) of the omnidirectional moving caster  16  (see  FIG. 12 ). 
     The electromagnetic contactor  112  is used for starting or stopping the motor as a driving source of the AGV  10 . 
     The power supply unit  108  has a charging device (not illustrated) or the like other than the battery  114 . 
     The laser distance sensor  116  is also called a range sensor, and emits a laser beam during traveling to the surroundings, receives the light reflected from objects around it such as a wall, a pillar or various installations, and measures the distance with each of the objects around it based on the time of flight. 
     The bumper (cable) switch  118  is formed in a U shape, for example, at the lower part of the AGV  10 , and is one of pressure-sensitive switches with conductivity and resilience for detecting contact and collision. 
       FIG. 1  illustrates a positional relation between the AGV  10  and the cart  40 . Only the side plates  202  forming integral parts of the side guide mechanism  20  (see  FIG. 2 ) thus can be viewed out of the integration mechanism for integrating the AGV  10  with the cart  40 . The integration mechanism will be described later. 
       FIG. 1  illustrates the AGV  10  from which a housing is removed for representing the outline of the internal structure/configuration thereof. The housing has a substantially rectangular parallelepiped shape, and is, for example, 600 mm wide, 400 mm deep and 900 mm high. The width here indicates the length in the direction orthogonal to the direction of progress of the AGV  10 . The depth is the length in the direction the same as the direction of progress of the AGV  10 . The height of 900 mm indicates the length from the position where the drive wheel  164  contacts a travel path (road surface) to the highest position (the end of the antenna, for example) of the operation/display unit  102 . Especially, the dimensions of the width and the depth of the AGV  10  are decided by taking into account the dimensions of the cart  40  to be coupled and the dimensions of the container  42  to be loaded on the cart  40 . Alternatively, if the AGV  10  is accompanied by a worker, the width and the depth of the AGV  10  are selected such that the worker can easily recognize the surrounding condition of the AGV  10  and the surrounding condition of the cart  40  to be coupled to the AGV  10 . The details will be described later. Furthermore, the height of the AGV  10  is selected such that the worker/operator can easily operate or touch the region of the operation/display unit  102 . 
       FIG. 2  is a schematic diagram obtained when the AGV  10  illustrated in  FIG. 1  is viewed from the back. The cart  40  is coupled to the back side of the AGV  10 . The same parts as  FIG. 1  are denoted by the same reference codes. 
     The operation/display unit  102  is provided with an emergency stop button  152  and direction indicators  154  that are not denoted by reference codes in  FIG. 1 . The emergency stop button  152  is prepared so as to allow the accompanying operator to urgently stop the operation when the omnidirectional cart transport mechanism  1  itself has any trouble, or if the omnidirectional cart transport mechanism  1  has a trouble in traveling due to the change in the surrounding environment. The direction indicators  154  display the direction of travel of the omnidirectional cart transport mechanism  1  or the quality of the traveling condition. The direction indicator  154  can be constituted by LEDs of a single color or multiple colors, for example. 
     In  FIG. 2 , fans  156  are mounted on the back side of the control unit  104  illustrated in  FIG. 1  while speakers  158  are mounted on the reverse side of the power supply unit  108  illustrated in  FIG. 1 . The fan  156  is prepared to be used for ventilating and cooling the entire interior of the AGV  10 . The speaker  158  is one of the sound transmission means for reporting a situation in which another AGV or a device approaches the omnidirectional cart transport mechanism  1  with sounds such as a beeper, a chime, a melodic pattern or the like. 
       FIG. 2  illustrates integral parts of the members forming the side guide mechanism  20  and the cart lift mechanism  30  that fail to be displayed in  FIG. 1 . The side guide mechanism  20  includes a pair of side plates  202  and a gear mechanism  218 . The cart lift mechanism  30  includes hooks  302 , slide shafts  304  and a servo motor  360 . Each mechanism is configured to organically connect these members with other members, though the details thereof will be described later. 
       FIG. 2  depicts a servo driver  162  for controlling the pair of servo motors  160  to drive the drive wheel  164  and driven casters  144 , etc. other than the side guide mechanism  20  and the cart lift mechanism  30 . Unlike the drive wheel  164 , the driven caster  144  is a wheel to which power from the servo motor or the like is not transmitted and rotated in accordance with traveling of the AGV  10 . 
       FIG. 3  is a schematic diagram when the omnidirectional cart transport mechanism  1  illustrated in  FIG. 1  is viewed from the bottom. In  FIG. 3 , the members the same as those in  FIGS. 1 and 2  are denoted by the same reference codes. The AGV  10  is provided with a pair of omnidirectional moving casters  16 , and the drive wheels  164  are integral components of the respective omnidirectional moving casters  16 . The omnidirectional moving caster described herein is one of the holonomic vehicles suggested in Japanese Patent No. 3791663 described before. The vehicle is capable of simultaneously and independently controlling the traveling velocity in the direction of progress and the lateral direction of the vehicle as well as the angular velocity about a vertical axis of the vehicle (change of the posture of the vehicle). The outline of the structure and configuration of the omnidirectional moving caster  16  will be illustrated in  FIG. 12  to be described later. 
     The AGV  10  is slightly rounded on the front, that is, on the bumper switch  118  side while being substantially flat on the back opposite to the front, and thus the contour of the AGV  10  can be said to be substantially quadrangular in plan view. 
     In  FIG. 3 , the side guide mechanism  20  is attached to the AGV  10  as illustrated in  FIGS. 7-9  to be described later. The pair of side plates  202  as integral parts of the side guide mechanism  20  extend to the both side portions of the cart  40  extending in the direction the same as the traveling direction X 3  of the AGV  10 . The side plates  202  are applied to a part of the corner members  40   c  in a longitudinal direction (long length direction) of the cart  40 , and abut against the both side portions of the cart  40  so as to hold the side portions therebetween during traveling and uncouple the parts of the both side portions of the cart  40  during non-traveling. 
     In  FIG. 3 , a cart lift connection base  330  being a base portion of the cart lift mechanism  30  is attached to the central edge of the AGV 10  in an orthogonal direction Y 3  orthogonal to the traveling direction X 3 . The main body of the cart lift mechanism  30  is installed upright on the cart lift connection base  330  from the near side to the far side of the paper of the drawing (see  FIGS. 14 and 8 ). Hooks  302  forming integral parts of the cart lift mechanism  30  extend from the side edges of the cart lift connection base  330  toward a central portion (coupled portion) of the frame member  40   f  of the cart  40 . Upon starting or traveling of the omnidirectional cart transport mechanism  1 , the hooks  302  of the cart lift mechanism hook and slightly lift the coupled portion (not depicted) constituted by an aperture or a groove as a part of the frame member  40   f . If lifting by the hooks  302  is made too high, the tilt between a leading end portion  40 L (coupled portion) and a trailing end portion  40   t  of the cart  40  is steep, to thereby cause an unfavorable difference in height between the front and rear cart casters  444 . Accordingly, the hooks  302  have to lift the cart  40  high enough to absorb the difference in height that can be caused between the front and rear wheels by resilience the cart casters  444  originally have. It is noted that the cart does not necessarily travel with the leading end portion  40 L of the cart  40  ahead, but the cart may travel with the trailing end portion  40   t  ahead of the leading end portion  40 L. In any event, the hooks  302  lift a region of the cart  40  close to the AGV  10 . 
     The cart  40  depicted in  FIG. 3  is substantially quadrangular in plan view, though having some projections and depressions when partially viewed. The cart  40  depicted in  FIG. 3  is long along the traveling direction X 3  while being short along the orthogonal direction Y 3 . Generally, the cart have different length in the longitudinal and lateral directions to often have a substantially quadrilateral shape, though such length is dependent on the container to be loaded thereon. The cart  40  is constituted by the corner members  40   c  that connect both of the frame members  40   f  in a quadrilateral shape, the four cart casters  444  pivotally supported on the corner members  40   c , etc. 
       FIG. 4  is a top view obtained when the omnidirectional cart transport mechanism  1  illustrated in  FIG. 1  is viewed from a side opposite to that in  FIG. 3 , that is, from the top (operation/display unit  102  side) to the bottom (drive wheel  164  side), and when the pair of side plates  202  do not hold the side surfaces of the cart  40 . The members the same as those in  FIGS. 1-3  are denoted by the same reference codes.  FIG. 4  depicts the electromagnetic contactor  112 , a battery gauge  124  for displaying remaining voltage of a battery, an operation start button  126 , a reset button  128 , a wireless module  134 , the emergency stop button  152 , the direction indicators  154 , etc.  FIG. 4  depicts a state in which the side plates  202  are slightly spaced apart from the corner members  40   c  of the cart  40  without abutting against them. This situation depicts a non-transportation state in which the integration function of the AGV  10  with the cart  40  is released. 
       FIG. 5  is a top view obtained when the omnidirectional cart transport mechanism illustrated in  FIG. 1  is viewed from the side opposite to that in  FIG. 3  similarly to  FIG. 4 , that is, from the top. The members the same as those in  FIGS. 1-4  are denoted by the same reference codes.  FIG. 5  is different from  FIG. 4  in that the pair of side plates  202  abut against the side surfaces of the cart  40 . This is a state where the AGV  10  and the cart  40  are integrated with each other, and this situation is brought about when the omnidirectional cart transport mechanism  1  travels. 
       FIG. 6  is a schematic perspective view obtained when the omnidirectional cart transport mechanism  1  illustrated in  FIG. 1  is viewed from the bottom to the top.  FIG. 6  is also a perspective view when the omnidirectional cart transport mechanism  1  illustrated in  FIG. 3  is viewed from the near side to the much farther side of the paper of the drawing. In  FIG. 6 , the members the same as those in  FIGS. 1-5  are denoted by the same reference codes. The overlapped members will not be described while the members only displayed in  FIG. 6  will be described here. 
     The pair of servo drivers  162  are used for the pair of servo motors  160  to be described later respectively, and drive the servo motors  160  in accordance with an instruction from the controller  106 . It is noted that the servo motors  160  are motors as power sources for driving the drive wheels  164  (omnidirectional moving casters  16 ). A base plate  132  is a platform for being mounted with the laser distance sensor  116  or for supporting a bracket mounted with the controller  106 , the electromagnetic contactor  112 , the battery  114 , etc. The slide shafts  304  are sliding shafts that allow the hooks  302  (see  FIG. 7 ) forming integral parts of the cart lift mechanism  30  to move upward or downward. A bearing  308  is a support member that allows a feed screw  306  (see  FIG. 14 ) forming a part of the cart lift mechanism  30  to rotate. The feed screw  306  extends or shortens the distance between the pair of side plates  202  in the right-left direction. The servo motor  360  (see  FIGS. 7 and 14 ) is a driving source for the cart lift mechanism  30 . 
       FIG. 7  is a schematic perspective view of the AGV  10  illustrated in  FIG. 1  when viewed from the back (see  FIG. 2 ) to the front, that is, the bumper switch  118  side. The schematic perspective view is partially overlapped with that in  FIG. 2 . The members the same as those in  FIGS. 1-6  are denoted by the same reference codes.  FIG. 7  more clearly depicts the integration mechanism for integrating the AGV  10  with the cart  40 , that is, the positional relation between the side guide mechanism  20  and the cart lift mechanism  30 . It is noted that the positional relation in  FIG. 7  depicts a state in which the integration function is released, specifically, the distance between the pair of side plates  202  is farthest in the right-left direction while the hooks  302  are moved downward to the lowest position and are not coupled to the cart  40  or do not lift the cart  40 . 
     The side guide mechanism  20  is separately disposed on both sides of the cart lift mechanism  30  such that the side plates  202  are applied to the both side surface portions in the longitudinal direction of the cart  40  as illustrated in  FIGS. 3-5 .  FIG. 7  depicts the side plates  202 , slide shafts  204 , feed screws  206 , bearings  208 , the gear mechanism  218 , nut portions  220  and a servo driver  262  that form parts of the side guide mechanism  20 . The servo driver  262  controls the servo motor  260  (see  FIG. 13 ). The members directly abut against the cart  40  among the side guide mechanism  20  are the pair of side plates  202  and  202 . The feed screw  206 , the nut portion  220  and the like are prepared in order to perform conversion to a linear-motion for extending or shortening the distance between the pair of side plates  202  in the lateral direction (short length direction) of the cart  40 . 
     It is noted that  FIG. 7  does not depict all the members forming the side guide mechanism  20 . The entirety of the side guide mechanism  20  will be illustrated in  FIG. 13  to be described later. The control of the movement of the side plates  202  in the right-left direction (direction in which the pair of side plates  202  and  202  approach or depart from each other) is performed by controlling the servo driver  262  in accordance with an instruction from the controller  106  and driving the servo motor  260  by the servo driver  262 . Here, the side guide mechanism  20  illustrated in  FIG. 7  is in an inactivated state in which the side plates  202  do not abut against the cart  40 . 
     Now,  FIG. 7  illustrates the hooks  302 , the servo motor  360  and a servo driver  362  that form integral parts of the cart lift mechanism  30 . The servo driver  362  is used with the servo motor  360  in a pair, and drives the servo motor  360  in accordance with an instruction from the controller  106 . It is noted that the cart lift mechanism  30  also includes the slide shafts  304 , etc. depicted in  FIG. 6 , which are not denoted by the reference codes in  FIG. 7  for the sake of brevity. The entirety of the side guide mechanism  20  will be illustrated in  FIG. 13  to be described later. 
       FIG. 8  is a schematic perspective view when only the hooks  302  forming the cart lift mechanism  30  are lifted upward in the side guide mechanism  20  and the cart lift mechanism  30  illustrated in  FIG. 7 , that is, when the cart lift mechanism  30  is activated. In  FIG. 8 , the members the same as those in  FIG. 7  are denoted by the same reference codes. 
       FIG. 8  is different from  FIG. 7  in the region denoted by a reference code Y 8  in which the hooks  302  slightly move upward in comparison with  FIG. 7 . This is a state where the hooks  302  are hooked on the central edge of the cart  40  to integrate the AGV  10  with the cart  40 . The control of the upward and downward movement of the hooks  302  is performed by controlling the servo driver  362  in accordance with an instruction from the controller  106  and driving the servo motor  360  by the servo driver  362 . 
     The cart lift mechanism  30  slightly lifts the AGV  10  side of the cart  40 , not the entire cart  40 , relative to the road surface while hooking in the vicinity of the central edge (not illustrated) of the short length direction of the cart  40  with the hooks  302 . This causes a part of the entire weight including the cart  40  and the container  42  to be loaded thereon to be applied to the cart lift mechanism  30  as a reaction force. This application of the reaction force increases the frictional force between the drive wheels  164  and the road surface. In other words, the grip force of the drive wheels  164  on the road surface is increased, which can reduce or eliminate skidding of the omnidirectional cart transport mechanism  1  on a travel path. 
     Assuming that the entire weight including the cart  40  and the container  42  to be loaded thereon is 200 kg, for example, the weight to be applied to the cart lift mechanism  30  as reaction force is a maximum of approximately 40 kg, for example. That is, approximately 20% of the entire weight may be used as a guide. 
     Generally, in the case where an AGV is configured to carry multiple containers containing commodities, semi-finished products or the like placed on the cart, the drive wheels of the AGV may be skidded if the weight of the transported products is great relative to the weight of the AGV. The cart lift mechanism  30  according to the present application can avoid such a problem. In addition, lifting up by the hooks  302  enables secure coupling to the cart  40 , which enhances the integration function of the AGV  10  with the cart  40 . 
     In other words, the cart lift mechanism  30  has two functions of the integration mechanism of integrating the AGV  10  with the cart  40  and a skid prevention mechanism. 
     Now, when the two wheels of the cart casters  444  positioned closer to the AGV  10 , that is, on the leading end portion  40 L side illustrated in  FIG. 3  are completely separated from the road surface, the load of the transported products is concentrated on the two wheels of the cart casters  444  positioned farthest from the AGV  10 , that is, closer to the trailing end portion  40   t , so that these two wheels may be easily damaged or have difficulties in traveling. Therefore, the cart lift mechanism  30  is set such that reaction force of approximately 20% of the weight of the transported products is applied to the drive wheels  164  as described above. More specifically, the lifting force by the cart lift mechanism  30  is provided based on a target torque set value or a set value of the limitation of torque of the servo motor  360  moving the cart lift mechanism  30 . These set values can be set on the basis of the weight of the AGV  10  itself, the total transport weight including the cart  40 , the structure, the material property and the dimensions of the servo motor  360  or the drive wheel  164 , or a towing force with which the AGV  10  can tow, or the like. 
     The cart lift mechanism  30  including the hooks  302  is positioned at an intermediate portion between the pair of side plates  202 . The pair of side plates  202  are members for being brought into abutment against the both side surfaces of the cart  40 . This requires a certain amount of spaced portion between the pair of side plates  202 . The cart lift mechanism  30 , especially the hook  302  moving upward and downward, is positioned in the spaced portion, which can make the AGV  10  compact. 
       FIG. 9  is a schematic perspective view depicting regions when the side guide mechanism  20  illustrated in  FIG. 7  is placed in an activated state, and the pair of side plates  202  hold the both side portions of the cart  40  therebetween, and further depicting a state where the hooks  302  of the cart lift mechanism  30  are raised upward to lift the cart  40 . In  FIG. 9 , the members the same as those in  FIGS. 7 and 8  are denoted by the same reference codes.  FIG. 9  is different from  FIG. 8  in that the side plates  202  are slightly closer to the hook  302  side as depicted by the regions denoted by a reference code X 9 . 
     The horizontally movable distance of the pair of side plates  202  is approximately several tens of mm, and the actual travel distance is decided by the length of the cart  40  in the short side direction. Meanwhile, the vertically movable distance of the hook  302  is decided by the distance from the road surface to the frame member  40   f  of the cart  40  illustrated in  FIG. 10 . As described before, the hooks  302  slightly lift one side of the cart  40  closer to the short length direction until the torque of the servo motor  360  reaches the set value, so that the reaction force is applied to drive wheels  164  of the AGV  10 . This offers advantages of increasing the frictional force with the road surface of the travel route and preventing a skid of the drive wheels  164 . Moreover, the hooks  302  are placed a little higher than a region of the cart  40 , and thus even if the cart  40  and the AGV  10  swing during traveling of the omnidirectional cart transport mechanism  1 , the hooks  302  and the cart  40  are securely coupled to each other. 
       FIG. 10  is a schematic view depicting a positional relation between the cart lift mechanism  30  and the cart  40  according to the present application when the cart lift mechanism  30  does not lift the cart  40 , that is, when the hooks  302  of the cart lift mechanism  30  move downward.  FIG. 10  is a drawing illustrating the cart lift mechanism  30  illustrated in  FIG. 7  plus the cart  40  to be coupled thereto, and viewed from an angle different from that in  FIG. 7 . The members the same as those in  FIGS. 1-9  are denoted by the same reference codes. 
     The members forming the cart lift mechanism  30  illustrated in  FIG. 10  include the hook  302 , the feed screw  306 , the bearings  308 , a shaft coupling  316 , and the servo motor  360 . 
     The rotational motion generated by the servo motor  360  is converted into linear-motion for moving the hook  302  upward and downward by the feed screw  306  via the shaft coupling  316 .  FIG. 10  depicts a state in which neither the frame member  40   f  nor the corner member  40   c  of the cart  40  abuts against a hook concavity  302   h  of the hook  302 . In  FIG. 10 , the presence of another corner member  40   c  on the far side of the paper of the drawing other than the corner member  40   c  on the near side of the paper of the drawing is apparent from  FIG. 3 , etc. The hooks  302  generally hook the central portion of the frame member  40   f , and it is observed that neither the hook concavity  302   h  nor the both side surfaces of the concavities abut against the central portion of the frame member  40   f.    
     It is noted that the region depicted by a reference code Y 10  is prepared to compare the upward and downward movement of the hook  302  with that in  FIG. 11  to be described later.  FIG. 10  depicts that the hook  302  is closer to the lower bearing  308  side. 
       FIG. 11  is a schematic view depicting a positional relation between the cart lift mechanism  30  and the cart  40  according to the present application when the cart lift mechanism  30  lifts the cart  40 , that is, when the cart lift mechanism  30  is activated. The omnidirectional cart transport mechanism  1  starts and travels in the state illustrated in  FIG. 11  when carrying transported products. 
       FIG. 11  depicts a state in which the hook  302  hooks the central portion of the frame member  40   f . Here, in  FIG. 11 , though the hook  302  appears to abut against the corner member  40   c  at a first glance, the object to be hooked is in the vicinity of the central portion (coupled portion) of the frame member  40   f  of the cart  40  positioned at the back of the AGV  10  as can be understood from  FIG. 3 . 
       FIG. 11  is different from  FIG. 10  only in the region denoted by a reference code Y 11 .  FIG. 11  depicts that the hook  302  is moved upward to a substantially intermediate position between the upper bearing  308  and the lower bearing  308  as compared with  FIG. 10 . In any event, the distance to be moved upward or downward by the hook  302  is equal to or less than several tens of millimeters. 
       FIG. 12  is a schematic perspective view of the omnidirectional travel caster  16  to be used in one embodiment of the present application. As illustrated in  FIG. 3 , the omnidirectional moving caster  16  illustrated in  FIG. 12  is prepared in a pair (two wheels), and each of the moving casters  16  is secured to the base plate  132  (see  FIGS. 7 and 8 ) of the AGV  10  via a mounting plate  172 . 
     The respective servo motors  160  are used with the servo drivers  162  depicted in  FIG. 6  and  FIG. 7  in pairs and are operated in accordance with an instruction from the controller  106 . 
     In  FIG. 12 , an axis ax 1  and an axis ax 2  are virtual axes provided for illustrative purpose, and the axis ax 1  coincides with the axis of rotation of the bearing attached inside a bearing box  187 . Meanwhile, the axis ax 2  coincides with the rotation shaft of the drive wheel  164 . The omnidirectional moving caster  16  has the pair of servo motors  160 , and the rotational operation of both of the servo motors can provide change in orientation (steering) of the drive wheel around the axis ax 1  and rotational force of the drive wheel around the axis ax 2 . Then, the axis ax 1  and the axis ax 2  are spaced with a certain distance and do not intersect each other, and thus if the amount of change in orientation (steering) and the amount of rotation of the drive wheel  164  are appropriately provided, the axis ax 1  can be translated in the direction of rotation of the drive wheel  164  while the axis ax 1  can be steered in any direction with reference to the position where the drive wheel  164  is set on the road surface. The omnidirectional cart transport mechanism  1  has the pair of the omnidirectional moving casters  16 , and thus, the respective axes ax 1  as virtual axes are present in determined positions on the vehicle. The relative movements of these two axes ax 1  allow the omnidirectional cart transport mechanism  1  to immediately move in any direction as well as to rotate at that position. 
     The encoder  166  detects a rotation angle around the axis ax 1  of the drive wheel  164 . A signal indicating the rotation angle detected by the encoder  166  is transmitted to the controller  106  through an output cable not denoted by a reference code. Meanwhile, the servo motor is generally provided with an encoder for detecting a rotation angle of the rotation shaft of the motor. By the pair of servo motors  160  depicted in  FIG. 12  as well, the rotation angles of the rotation shafts are detected and transmitted to the controller  106 . The controller  106  calculates the rotation angles around the axis ax 1  and the axis ax 2  of the drive wheel  164  per preset time from the rotation angles of the rotation shafts of these two servo motors  160 . The controller  106  can obtain the direction around the axis ax 1  of the drive wheel  164  from moment to moment based on the signal received from the encoder  166 , and thus can estimate the distance and direction of the translational movement of the axis ax 1  relative to a reference point on the vehicle of the AGV  10  at the previous time point in combination with these information. In addition, by taking into account the estimated values obtained from the pair of omnidirectional moving casters  16  and the information on the distances from the surrounding installation and equipment obtained by the laser distance sensor  116 , the position of the AGV  10  itself can be presumed. The controller  106  calculates a command to be provided to the servo motors  160  so as to follow a virtual route based thereon to drive the servo motors  160  via the servo driver  162 . 
     A gear housing portion  168  is a housing to house a reduction gear mechanism for reducing the rotation speed in the servo motors  160 . 
     The omnidirectional moving caster  16  includes a first pulley  176 , and a rotational force of a bevel gear (not illustrated), for example, that is housed in the gear housing portion  168  is transmitted to the first pulley  176 . A second pulley  178  is attached to a shaft portion of the drive wheel  164 . A timing belt  182  transmits a rotational force of the first pulley  176  to the second pulley  178 . The second pulley  178  is fixed and pivotally supported on the drive wheel  164 , and the drive wheel  164  is rotated by a rotational force of the second pulley. 
     A wheel bracket  186  pivotally supports the drive wheel  164  and the second pulley  178  fixedly supported on the drive wheel  164  via a bearing (not illustrated) about the axis  2 . A suspension  184  supports the space between a gear housing portion  174  and wheel bracket  186  with a spring and absorbs the irregularities of the road surface. 
     In the omnidirectional moving caster  16  illustrated in  FIG. 12 , the gear mechanisms contained in the gear housing portions  168  and  174  are not especially depicted. The gear housing portion  168  contains a pair of reduction gear mechanisms that are respectively driven by the pair of servo motors  160 . Typical example of the reduction gear mechanism is a mechanism in which spur gears of different number of teeth are combined. It is noted that the deceleration mechanism is not limited to the mechanism using gears and may be the mechanism using a timing belt and a chain. However, the gear mechanism is suitable to compactly configure the deceleration mechanism. Moreover, the gear housing portion  174  houses a so-called differential gear mechanism that uses rotation outputs of the pair of reduction gear mechanisms as inputs and extracts the differential output between them. The first pulley  176  is fixed and pivotally supported on the output shaft of the differential gear mechanism (not illustrated). 
     In  FIG. 12 , the two servo motors  160  for activating the pair of drive wheels  164  are both attached above the mounting plate  172  at the positions vertical to the road surface. Generally, the servo motors  160  are disposed near the drive wheels  164  to thereby achieve the compact structure. The servo motors  160 , however, disposed near the drive wheels  164  are easily affected by the environment of the travel route. In the case where the omnidirectional cart transport mechanism  1  travels on a floor with puddles of wash water especially in a food factory, the servo motors  160  are wet, which may cause electrical fault such as short circuit. Hence, in the present application, the servo motors  160  are disposed at the highest positions of the omnidirectional moving caster  16 . 
     It is noted that as a system for controlling the omnidirectional moving caster  16 , a well-known differential gear system and a system in which the wheel axle and the steering shaft of the caster are controlled by separate actuators can be adopted. 
     In addition, so-called mecanum wheels may be employed as omnidirectional moving mechanism  1  instead of the omnidirectional moving caster  16 . A mecanum wheel is equipped with several freely rotatable rollers by motor output attached to the whole circumference of the rim of the wheel at 45 degrees. Alternatively, so-called omni-wheels with small discs around the circumference which are perpendicular to the turning direction may be employed. 
       FIG. 13  is a schematic perspective view roughly illustrating the entirety of the side guide mechanism  20  as one component of the present application. The output to be finally provided by the side guide mechanism  20  is a function (opening and closing function) of setting or releasing the integration of the AGV  10  with the cart  40  by extending or shortening the distance between the pair of side plates  202  as can be understood from the description up to now. The driving force for opening or closing the space between the side plates  202  is exerted by the servo motor  260 . The driving shaft of the servo motor  260  is connected to a rotation shaft  216  via a shaft coupling  214 . The rotation shaft  216  is attached with the gear mechanisms  218  (spur gears, for example) on both ends. 
     In  FIG. 13 , the pair of side plates  202  are disposed on both sides of the main body of the side guide mechanism  20 . The respective side plates  202  are driven in a direction parallel to the feed screws  206  by separate linear-motion mechanisms each composed of the feed screw  206  and the nut portion  220 . 
     The individual side plates  202  on both sides are integrally connected to the nut portions  220  forming the individual linear-motion mechanisms on both sides. Thus, when a rotational force is provided to each of the feed screws  206 , the nut portion  220  and the side plate  202  connected thereto move in a direction parallel to the feed screw  206  in accordance with the direction of rotation. Here, the individual feed screws  206  on both sides have central axes placed on the same line while being disposed to have helixes of the screws wound in opposite directions. Thus, even if rotational force in the same direction is applied to the respective screws from the servo motor  260  via the gear mechanism  218 , the nut portions  220  on both sides move in the opposite directions to each other. This makes it possible to shorten or extend the distance between the side plates  202  and make the side plates  202  abut against the side surfaces of the cart  40  or uncouple the side plates  202  from the side surfaces of the cart  40 . 
     The motion of each side plate  202  is limited to axial slidable motion by the two slide shafts  204  arranged in parallel to the feed screw  206 . Thus, even if a rotational force is provided to the feed screw  206 , the side plate  202  does not rotate around the feed screw  206  together with the nut portions  220  connected thereto. The both ends of the feed screws  206  are pivotally supported to side guide frames  209  by the bearings  208 . 
       FIG. 14  is a schematic perspective view roughly illustrating the entirety of the cart lift mechanism  30  as one component of the present application. The output to be finally provided by the cart lift mechanism  30  moves the hook  302  upward and downward to thereby integrate the AGV  10  with the cart  40  or release the integration as can be understood from the description up to now. The driving force for moving the hook  302  upward and downward is exerted by the servo motor  360 . The rotational motion of the servo motor  360  is decelerated by a reduction gear  314  and transmitted to the feed screw  306  via the shaft coupling  316 . The hook  302  is integrally connected to a nut portion  320  forming the linear-motion mechanism constructed by the feed screw  306  and the nut portion  320 . When the feed screw  306  is rotated by the servo motor  360 , the nut portion  320  and the hook  302  connected thereto are moved upward or downward depending on the direction of rotation of the servo motor  360 . When the hook  302  is moved upward, the hook concavity  302   h  and the side surface are applied to an aperture portion or an inverted U-shaped groove (not depicted) of the frame member  40   f  of the cart  40  (see  FIGS. 3 and 11 ) to integrate the AGV  10  with the cart  40 . In contrast, when the hook  302  is moved downward, the hook concavity  302   h  and the side surface are uncoupled from the aperture or the groove provided at the frame member  40   f  to release the integration. 
       FIG. 15  is a table depicting the dimensions including the width and depth of container carts/platform carts that are currently used. The container carts/platform carts (hereinafter referred to as “cart”) indicate carts without a hand-operated handle. Eight types of carts in total sold by A-Company to F-Company are depicted, and the maximum load weight for all the carts is 300 kg. For example, the cart with a product number A-1 sold by A-Company is 505 mm wide and 800 mm deep. Here, when the width and the depth of the platform cart are defined herein, the length in the short length direction is assumed as a width while the length in the long length direction (longitudinal direction) is assumed as a depth. Now, when the cart with the product number A-1 is coupled to the AGV according to the present application (width (AW)≈600 mm, and depth (AD)≈400 mm), the omnidirectional cart transport mechanism  1  is formed to have an overall length of 1,200 mm (800 mm+400 mm) and an overall width of 600 mm. 
     The cart with a product number B-2 sold by B-Company is 600 mm wide and 900 mm deep. The width of the cart with the product number B-2 is 600 mm, that is, the same as the width AW of the AGV  10 . Accordingly, when this cart is coupled to the AGV  10  according to the present application (600 mm wide and 400 mm deep), the overall length is 1,300 mm (900 mm+400 mm) while the overall width is 600 mm. Thus, it is observed that the cart with the product number B-2 has an overall length greater than the cart with the product number A-1 by 100 mm. 
     The cart with a product number C-1 sold by C-Company is 605 mm wide and 935 mm deep. The cart with the product number C-1 has a width greater than the width AW of the AGV  10  by 5 mm. Accordingly, when this cart is coupled to the AGV  10  according to the present application (600 mm wide and 400 mm deep), the overall length is 1,335 mm (935 mm+400 mm) while the overall width is 605 mm. Thus the cart with the product number C-1 has an overall length greater than the cart with the product number B-2 by 35 mm and has an overall width greater than the width AW of the AGV  10  by 5 mm. 
     The width and depth of the cart with a product number D-1 sold by D-Company and the cart with a product number E-1 sold by E-Company are the same as those of the cart with the product number B-2 of B-Company. Accordingly, the overall length of the omnidirectional cart transport mechanism  1  is 1,300 mm (900 mm+400 mm) while the overall width is 600 mm. 
     The cart with a product number F-1 sold by F-Company is 610 mm wide and 910 mm deep. The width of the cart with the product number F-1 is greater than the width AW of the AGV  10  by 10 mm. Accordingly, when this cart is coupled to the AGV  10  according to the present application (600 mm wide and 400 mm deep), the overall length is 1,310 mm (910 mm+400 mm) while the overall width is 610 mm. 
     As can be understood from  FIG. 15 , the width of the cart ranges from 450 mm to 610 mm while the depth of the cart ranges from 800 mm to 935 mm. Accordingly, the difference between the maximum value and the minimum value of the width is 160 mm (610 mm−450 mm) while the difference between the maximum value and the minimum value of the depth is 135 mm (935 mm−800 mm). These values are values to be reflected when the vehicle dimensions of the AGV  10  according to the present application are decided. The standard dimensions adopted by the AGV  10  herein is approximately 600 mm wide and approximately 400 mm deep as described before, and more details will be described below. 
       FIG. 16  depicts investigation results of hand carts, that is, carts with a hand-operated handle sold by eight companies. The maximum load weight is 300 kg similarly to  FIG. 15 . It is observed that the width of the carts offered by the eight companies are commonly approximately 600 mm, and the depth thereof is commonly approximately 900 mm. These numerical values are thus approximately the same as those in the container carts/the platform carts as illustrated in  FIG. 15 . Thus, the dimensions of the AGV  10  according to the present application can also be applied to the handle carts by referring to the dimensions of the container carts/the platform carts. 
       FIG. 17  depicts investigation results of the dimensions of containers that are currently used. The containers are sold by G-Company and H-Company. Seven types of containers are investigated for especially G-Company, though containers of similar dimensions are offered from H-Company as well. 
     For example, the container with the container number 1 (product number G-1 sold by G-Company) is 193 mm wide, 342 mm deep and 99 mm high, and can have a relatively small capacity to contain commodities and semi-finished products. The container of the product number G-1 can be loaded on the cart with the product number B-1 sold by the B-Company having the smallest dimensions among those depicted in  FIG. 15 . 
     Now, the width of containers with product numbers G-1, G-2, G-3, G-4 and G-5 ranges from 193 mm to 425 mm while the depth thereof ranges from 342 mm to 716 mm. The containers with such dimensions are not apparently projected from the contour of the cart if they are loaded on the cart with the product number B-1 sold by the B-Company having the smallest dimensions (450 mm wide and 800 mm deep) among those depicted in  FIG. 15 . 
     A container with a container number 6 (product number G-6 of G company) is 503 mm wide and 838 mm deep. When the container is loaded on the cart with the cart number B-1, the container is projected in the depth direction by 38 mm. This problem can be solved by substituting the cart with the cart number 3 (product number B-2) for this cart. 
     The container with a container number 7 (product number G-7) is 503 mm wide and 1,005 mm deep. There is no carts depicted in  FIG. 15  that can load the container with the container number 7 having a depth of 1005 mm without projection from the contour of the cart. This container, however, can be transported by almost all of the carts depicted in  FIG. 15 , though a large turning radius may occur. 
     The container with a container number 8 (product number H-1) is 500 mm wide and 700 mm deep while the container with a container number 9 (product number H-2) is 595 mm wide and 820 mm deep. The dimensions of these containers fall within the dimension of the carts with the cart numbers B-2, C-2, D-1, E-1, etc. which allows these containers to be transported without projection from the carts. 
     Hence, as understood from  FIG. 15 ,  FIG. 16  and  FIG. 17 , the dimension of the cart and the dimension of the container carried by hand without using another equipment such as a hand forklift or the like by a worker are selected to receive each other, not decided independent of each other. This is natural in terms of practicality, usability and safety. Furthermore, since the cart and the container are used by a person, these dimensions have to ensure operability and safety for one person. The dimensions of the omnidirectional cart transport mechanism  1  according to the present application are decided in view of these matters. 
       FIG. 18  is a schematic view illustrating a situation in which the omnidirectional cart transport mechanism  1  according to the present application travels on a relatively narrow travel path  50  with corners. The omnidirectional cart transport mechanism  1  travels in a self-navigation system with the cart  40  and the AGV  10  integrated with each other by the side guide mechanism illustrated in  FIG. 13  and the cart lift mechanism  30  illustrated in  FIG. 14 . In other words, the AGV  10  can travel to a destination without a guide material, steering by a person or the like by using a map information storing function, a map creating function, a self-position recognition function and a travel route setting function, etc. that the AGV  10  itself has. 
     The width AW and the depth AD of the AGV  10  forming the omnidirectional cart transport mechanism  1  are assumed to be 600 mm and 400 mm, respectively, as described before. For convenience of description, the width SW and the depth SD of the cart  40  are assumed to be SW=600 mm and SD=900 mm, respectively. The cart  40  is a cart currently used, not a dedicated cart particularly prepared so as to be suited to the AGV  10  according the present application, and corresponds to the cart with the product number C-2 illustrated in  FIG. 15 , for example. 
     The overall length L of the omnidirectional cart transport mechanism  1  including the cart with the cart number C-2 and the AGV  10  in combination is AD+SD=400 mm+900 mm=1300 mm. The overall width D is AW=SW=600 mm. In other words, the ratio between the length and the width of the omnidirectional cart transport mechanism  1  is approximately 2:1. 
     Here, assuming that the total weight obtained when only eight to twelve tiered containers  42  are loaded on the cart  40 , or when a container  42  housing various commodities and semi-finished products is loaded on the cart  40  is, for example 150 kg-300 kg, the center of gravity 1 cg of the omnidirectional cart transport mechanism  1  moves toward the central part of the cart  40 , not the side closer to the AGV  10 . The closer the turning center of the omnidirectional cart transport mechanism  1  is to the center of gravity 1 cg, the smaller the rotational inertia is, which makes it possible to change the posture (travel direction) of the cart on which transported products are loaded stably and safely with a little driving force though the travel distance is long. In contrast thereto, when the transported products and the cart having a total weight of 150 kg-300 kg swing around a partial region of the AGV  10  within, large rotary inertia occurs, which requires a great driving force at a start of movement. In addition, not only a great driving force is required to stop the transported products and the cart that gain impetus once, but also such a movement cannot be controlled. Hence, if heavy products placed on a cart are transported, the AGV preferably travels while shifting the turning center to the cart. Here, the omnidirectional cart transport mechanism  1  can literally travel in all directions and can immediately move directly horizontally, and thus can turn the cart around a turning center at any position. As the distance from center of gravity 1 cg of the turning center to the rear end of the AGV  10  is shorter, the cart  40  and the AGV  10  are less likely to collide with a wall and equipment around them if the cart  40  and the AGV  10  are rotated in an integrated state with reference to the turning center on the cart  40 . Thus, it is desirable that the width AW and the depth AD of the AGV  10  are made as small as possible. 
     Now, it is said that the shoulder width of an ordinary person is 450 mm-460 mm. It is also said that the width of a passage that allows one person to pass is 520 mm-600 mm at minimum. It may be considered that the width of a passage and an entrance through which an ordinary person commonly transports the transported good using a cart as well as the size of the turning space are decided roughly based on these values including an empirical rule. 
     As described above, the present inventors obtain such findings that the width AW and the depth AD of the AGV  10  are respectively selected as AW=520 mm-700 mm and AD=340 mm-480 mm, more preferably approximately AW≈600 mm and approximately AD≈400 mm in view of the miniaturization of the omnidirectional cart transport mechanism  1 , traveling on a relatively narrow passage through which a person currently passes for transportation with a cart, and the dimensions of the container carts and the container that are currently used. 
     The width AW of the AGV  10  can be made shorter than 600 mm. The AGV  10 , however, is required to be mounted with a motor, a reduction gear, a secondary battery, communication equipment, etc. and is thus required to ensure some extent of capacity. Hence, if the width of the AGV  10  is narrowed down to 460 mm that approaches the length of a person&#39;s shoulder, the depth AD thereof has to be increased to ensure a certain amount of capacity. If the depth AD is made larger, a turning radius upon traveling also becomes larger, resulting in provision of a wide passage. 
       FIG. 19  is a schematic diagram illustrating a behavior until the omnidirectional cart transport mechanism  1  illustrated in  FIG. 1  places loads in a preset container housing area. In the premises  400  illustrated in  FIG. 19 , structures such as various devices, mechanical equipment, pillars, etc. are assumed to be installed. The two-dimensional or the three-dimensional shapes/dimensions of the structures of various equipment or the like installed in the premises  400  are important sources of information for traveling of the omnidirectional cart transport mechanism  1 . For the convenience of description herein, such devices are objects to be detected and recognized for the omnidirectional cart transport mechanism  1 , and referred to as objects to be recognized, and denoted by reference codes  452 ,  454 ,  456 ,  458  and  462 . 
       FIG. 19  depicts a state where the omnidirectional cart transport mechanism  1  has already been finished to store cart containers  402 ,  404 ,  406 ,  408 ,  412  and  414  including the cart  40  and containers to be loaded in a housing area  410  and is about to store a cart container  416 . 
     The omnidirectional cart transport mechanism  1  travels to a predetermined position within the housing area  410  while detecting and confirming the presence of the objects to be recognized  452 ,  454 ,  456 ,  458  and  462  following map information/location information, etc. previously stored in the controller  106 . 
     When the omnidirectional cart transport mechanism  1  stores the cart container  416  in the housing area  410 , the controller  106  has information on the completion of storing the cart containers  402  to  414  and information on the cart container  416  as a next object to be stored. 
     It is further possible to recognize that the cart container  416  is to be stored adjacent to the cart container  414  and in front of the cart container  406  based on the number of cart containers and the housing state in the housing area  410  by the laser distance sensor  116 . 
     In  FIG. 19 , the omnidirectional cart transport mechanism  1  travels along a traveling route  52 . The two-dimensional information on the traveling route  52  has previously been stored in the controller  106 . However, the omnidirectional cart transport mechanism  1  performs self-navigation control during traveling by measuring distances between the objects to be recognized  454 ,  456 , etc. and the housing area  410  or the distance from the cart containers  412 ,  414 , etc. that have already been stored by the laser distance sensor  116 . 
     When traveling to a position between the object to be recognized  462  and the cart container  412 , the omnidirectional cart transport mechanism  1  stops at once and moves back to the position where the cart container  416  is easily stored along a traveling route  54 . The AGV  10  is generally followed by the cart  40 , though this order is reversed on the traveling route  54 . When the cart container  416  is stored in a predetermined position, the AGV and the cart  40  are uncoupled from each other, and only the AGV returns to the starting point through a traveling route  58 . It is noted that uncoupling of the AGV  10  from the cart  40  is performed by the controller  106  detecting that the cart container  416  has arrived at a predetermined position based on the data from the laser distance sensor  116  (see  FIG. 5 ) and issuing a signal for releasing the integration of the AGV  10  with the cart  40  to the side guide mechanism  20  and the cart lift mechanism  30 . 
     As described above, the side guide mechanism and the cart lift mechanism with a relatively simple structure according to the present application enable automatic coupling of the AGV to the cart to establish integration, and automatic uncoupling of the AGV from the cart to easily release the integration. The carts currently used by a person can be used as they are, which eliminates the need for newly providing a loading device for loading a container from a cart to an AGV or an unloading device for unloading a container from the AGV. Furthermore, the AGV is suited to the dimensions of the carts and the containers that are daily used frequently, which is very practical. Moreover, since the projected dimensions of the AGV  10  on the road surface are set to values suited to footprints when a person walks, the AGV  10  can travel on the existing passages and entrances conventionally used to transport products by pushing or drawing carts as they are without providing wide travel path and turning space specifically designed to the AGV. 
     In addition, even if transporting heavy products placed on a cart, the AGV can shift the turning center to the cart, or move the turning center during traveling by an omnidirectional traveling capability, which makes it possible to turn the cart and the AGV in an integrated manner with a little driving force in a relatively small space even at a cranked corner of the passage. 
     It is to be understood that the embodiments disclosed here is illustrative in all respects and not restrictive. The scope of the present invention is defined by the appended claims, and all changes that fall within the meanings and the bounds of the claims, or equivalence of such meanings and bounds are intended to be embraced by the claims.