Patent Publication Number: US-2020290804-A1

Title: Automated storage and retrieval system

Description:
TECHNICAL FIELD 
     The present invention relates to an automated storage and retrieval system, a vehicle for lifting and transporting storage containers stacked in stack within the system and a method thereof. 
     BACKGROUND AND PRIOR ART 
       FIG. 1  discloses a typical prior art automated storage and retrieval system  1  with a framework structure  100  and  FIGS. 2 and 3  discloses two different prior art container handling vehicles  201 , 301  suitable for operating on such a system  1 . 
     The framework structure  100  comprises a number of upright members  102  and a number of horizontal members  103  which are supported by the upright members  102 . The members  102 ,  103  may typically be made of metal, e.g. extruded aluminum profiles. 
     The framework structure  100  defines a storage grid  104  comprising storage columns  105  arranged in rows, in which storage columns  105  storage containers  106 , also known as bins, are stacked one on top of another to form stacks  107 . Each storage container  106  may typically hold a plurality of product items (not shown), and the product items within a storage container  106  may be identical, or may be of different product types depending on the application. The storage grid  104  guards against horizontal movement of the stacks  107  of storage containers  106 , and guides vertical movement of the containers  106 , but does normally not otherwise support the storage containers  106  when stacked. 
     The automated storage and retrieval system  1  comprises a rail system  108  arranged in a grid pattern across the top of the storage columns  105 , on which rail system  108  a plurality of container handling vehicles  201 , 301  are operated to raise storage containers  106  from and lower storage containers  106  into the storage columns  105 , and also to transport the storage containers  106  above the storage columns  105 . The rail system  108  comprises a first set of parallel rails  110  arranged to guide movement of the container handling vehicles  201 , 301  in a first direction X across the top of the frame structure  100 , and a second set of parallel rails  111  arranged perpendicular to the first set of rails  110  to guide movement of the container handling vehicles  201 , 301  in a second direction Y which is perpendicular to the first direction X. In this way, the rail system  108  defines grid columns  112  above which the container handling vehicles  201 , 301  can move laterally above the storage columns  105 , i.e. in a plane which is parallel to the horizontal X-Y plane. 
     Each prior art container handling vehicle  201 , 301  comprises a vehicle body  201   a , 301   a , and first and second sets of wheels  201   b , 301   b , 201   c , 301   c  which enable the lateral movement of the container handling vehicles  201 , 301  in the X direction and in the Y direction, respectively. In  FIGS. 2 and 3  two wheels in each set are fully visible. The first set of wheels  201   b , 301   b  is arranged to engage with two adjacent rails of the first set  110  of rails, and the second set of wheels  201   c , 301   c  is arranged to engage with two adjacent rails of the second set  111  of rails. Each set of wheels  201   b , 301   b    201   c , 301   c  can be lifted and lowered, so that the first set of wheels  201   b , 301   b  and/or the second set of wheels  201   c , 301   c  can be engaged with the respective set of rails  110 ,  111  at any one time. 
     Each prior art container handling vehicle  201 , 301  also comprises a lifting device (not shown) for vertical transportation of storage containers  106 , e.g. raising a storage container  106  from, and lowering a storage container  106  into, a storage column  105 . The lifting device comprises one or more gripping/engaging devices (not shown) which are adapted to engage a storage container  106 , and which gripping/engaging devices can be lowered from the vehicle  201 , 301  so that the position of the gripping/engaging devices with respect to the vehicle  201 , 301  can be adjusted in a third direction Z which is orthogonal the first direction X and the second direction Y. 
     Conventionally, and also for the purpose of this application, Z=1 identifies the uppermost layer of the grid  104 , i.e. the layer immediately below the rail system  108 , Z=2 the second layer below the rail system  108 , Z=3 the third layer etc. In the embodiment disclosed in  FIG. 1 , Z=8 identifies the lowermost, bottom layer of the grid  104 . Consequently, as an example, and using the Cartesian coordinate system X, Y, Z indicated in  FIG. 1 , the storage container identified as  106 ′ in  FIG. 1  can be said to occupy grid location or cell X=10, Y=2, Z=3. The container handling vehicles  201 , 301  can be said to travel in layer Z=0 and each grid column  112  can be identified by its X and Y coordinates. 
     Each prior art container handling vehicle  201 , 301  comprises a storage compartment or space for receiving and stowing a storage container  106  when transporting the storage container  106  across the grid  104 . The storage space may comprise a cavity arranged centrally within the vehicle body  201   a  as shown in  FIG. 2  and as described in e.g. WO2015/193278A1, the contents of which are incorporated herein by reference. 
       FIG. 3  shows an alternative configuration of a container handling vehicles  301  with a cantilever construction. Such a vehicle is described in detail in e.g. NO317366, the contents of which are also incorporated herein by reference. 
     The central cavity container handling vehicles  201  shown in  FIG. 2  may have a footprint, i.e. an extent in the X and Y directions, which is generally equal to the lateral or horizontal extent of a grid column  112 , i.e. the extent of a grid column  112  in the X and Y directions, e.g. as is described in WO2015/193278A1, the contents of which are incorporated herein by reference. 
     Alternatively, the central cavity container handling vehicles  101  may have a footprint which is larger than the lateral extent of a grid column  112 , e.g. as is disclosed in WO2014/090684A1. 
     The rail system  108  may be a single rail system, as is shown in  FIG. 4 . Alternatively, the rail system  108  may be a double rail system, as is shown in  FIG. 5 , thus allowing a container handling vehicle  201 , 301  having a footprint generally corresponding to the lateral extent of a grid column  112  to travel along a row of grid columns even if another container handling vehicle  101  is positioned above a grid column neighboring that row. Both the single and double rail system forms a grid pattern in the horizontal plane P comprising a plurality of rectangular and uniform grid locations or grid cells  122 , where each grid cell  122  comprises a grid opening  115  being delimited by a pair of tracks  110   a , 110   b  of the first tracks  110  and a pair of tracks  111   a , 111   b  of the second set of tracks  111 . In  FIG. 5  the grid cell  122  is indicated by a dashed box. 
     Each grid cell  122  has a width which is typically within the interval of 30 to 150 cm, and a length which is typically within the interval of 50 to 200 cm. Each grid opening  115  has a width and a length which is typically 2 to 10 cm less than the width and the length of the grid cell  122 . 
     In a storage grid  104 , a majority of the grid columns  112  are storage columns  105 , i.e. grid columns  105  where storage containers  106  are stored in stacks  107 . However, a grid  104  normally has at least one grid column  112  which is used not for storing storage containers  106 , but which comprises a location where the container handling vehicles  201 , 301  can drop off and/or pick up storage containers  106  so that they can be transported to an access station (not shown) where the storage containers  106  can be access from outside of the grid  104  or transferred out of or into the grid  104 . Within the art, such a location is normally referred to as a ‘port’ and the grid column  112  in which the port is located may be referred to as a port column  119 , 120 . 
     The grid  104  in  FIG. 1  comprises two port columns  119  and  120 . The first port column  119  may for example be a dedicated drop-off port column where the container handling vehicles  201 , 301  can drop off storage containers  106  to be transported to an access or a transfer station, and the second port column  120  may be a dedicated pick-up port column where the container handling vehicles  201 , 301  can pick up storage containers  106  that have been transported to the grid  104  from an access or a transfer station. 
     The access station may typically be a picking or a stocking station where product items are removed from or positioned into the storage containers  106 . In a picking or a stocking station, the storage containers  106  are normally never removed from the automated storage and retrieval system  1 , but are returned into the grid  104  once accessed. A port can also be used for transferring storage containers out of or into the grid  104 , e.g. for transferring storage containers  106  to another storage facility (e.g. to another grid or to another automated storage and retrieval system), to a transport vehicle (e.g. a train or a lorry), or to a production facility. 
     A conveyor system comprising conveyors is normally employed to transport the storage containers between the ports  119 , 120  and the access station. 
     If the ports  119 , 120  and the access station are located at different levels, the conveyor system may comprise a lift device with a vertical component for transporting the storage containers  106  vertically between the port  119 , 120  and the access station. 
     The conveyor system may be arranged to transfer storage containers  106  between different grids, e.g. as is described in WO2014/075937A1, the contents of which are incorporated herein by reference. 
     When a storage container  106  stored in the grid  104  disclosed in  FIG. 1  is to be accessed, one of the container handling vehicles  201 , 301  is instructed to retrieve the target storage container  106  from its position in the grid  104  and transport it to the drop-off port  119 . This operation involves moving the container handling vehicle  201 , 301  to a grid location above the storage column  105  in which the target storage container  106  is positioned, retrieving the storage container  106  from the storage column  105  using the container handling vehicle&#39;s  201 , 301  lifting device (not shown), and transporting the storage container  106  to the drop-off port  119 . If the target storage container  106  is located deep within a stack  107 , i.e. with one or a plurality of other storage containers  106  positioned above the target storage container  106 , the operation also involves temporarily moving the above-positioned storage containers prior to lifting the target storage container  106  from the storage column  105 . This step, which is sometimes referred to as “digging” within the art, may be performed with the same container handling vehicle that is subsequently used for transporting the target storage container to the drop-off port  119 , or with one or a plurality of other cooperating container handling vehicles. Alternatively, or in addition, the automated storage and retrieval system  1  may have container handling vehicles specifically dedicated to the task of temporarily removing storage containers from a storage column  105 . Once the target storage container  106  has been removed from the storage column  105 , the temporarily removed storage containers can be repositioned into the original storage column  105 . However, the removed storage containers may alternatively be relocated to other storage columns. 
     When a storage container  106  is to be stored in the grid  104 , one of the container handling vehicles  201 , 301  is instructed to pick up the storage container  106  from the pick-up port  120  and transport it to a grid location above the storage column  105  where it is to be stored. After any storage containers positioned at or above the target position within the storage column stack  107  have been removed, the container handling vehicle  201 , 301  positions the storage container  106  at the desired position. The removed storage containers may then be lowered back into the storage column  105 , or relocated to other storage columns. 
     For monitoring and controlling the automated storage and retrieval system  1 , e.g. monitoring and controlling the location of respective storage containers  106  within the grid  104 , the content of each storage container  106 ; and the movement of the container handling vehicles  201 , 301  so that a desired storage container  106  can be delivered to the desired location at the desired time without the container handling vehicles  201 , 301  colliding with each other, the automated storage and retrieval system  1  comprises a control system which typically is computerized and which typically comprises a database for keeping track of the storage containers  106 . 
     WO2016/120075A1, the contents of which are incorporated herein by reference, shows an example of an automated storage and retrieval system using vehicles with a central cavity. The disclosed container handling vehicles are dimensioned so that they have a footprint, i.e. a contact area against the track system, which has a horizontal extent that is equal to the horizontal extent of a grid cell. Within the art, such a container handling vehicle, i.e. a container handling vehicle having a footprint with a horizontal extent corresponding to the horizontal extent of a single grid cell, is sometimes referred to as a “single cell” container handling vehicle. Another single cell container handling vehicle is disclosed in WO2015/193278A1, the contents of which are incorporated herein by reference. 
     The single cell design disclosed in e.g. WO2016/120075A1 and WO2015/193278A1 reduces the space required for the container handling vehicles to travel on the track system, thus allowing more vehicles to operate on the track system without interfering with each other. Further, the stability of the vehicle operation is increased compared to a cantilever vehicle as disclosed in e.g. NO317366. 
     A problem with prior art automated storage and retrieval systems using storage container vehicles with single cell design is that these vehicles necessitate a vehicle body having a container receiving cavity that must be open towards the underlying storage grid. Strict space constraints are therefore set as to the locations and sizes of necessary vehicle components, e.g. lifting devices and wheel displacement means. To maximize the horizontal cross section of the cavity, at least some of the vehicle components of the prior art single cell vehicles are arranged above the cavity (see e.g. WO 2015/193278 A1) and/or within the wheels (see e.g. WO 2016/120075 A1), a solution that results in high complexity and cost compared with the earlier cantilever vehicle design disclosed in NO317366. Moreover, to minimize the height and the total weight of the vehicle, the size of components such as motors and batteries should in the ‘single cell’ vehicles be minimized in size and/or restricted to light weight materials, criteria that limit the maximum achievable operation efficiency of the vehicle such as the maximum lifting power available for the storage container lifting device. Bulky components may be arranged above the cavity by increasing the total height of the vehicle. However, such an increased height would result in an undesired decrease in overall vehicle stability in addition to increased cost. 
     The cantilever vehicle disclosed in NO317366 may contain components such as motor and batteries being considerably larger than the ‘single cell’ vehicle. But the cantilever vehicles have the disadvantage of protruding beyond the footprint of the vehicle, i.e. into a neighboring grid cell. This will prevent other container handling vehicles from operating on the neighboring grid cell, thus limiting the space available for other container handling vehicles to operate on the track system. Due to the cantilever design, these prior art vehicles have the additional disadvantage that they may lift storage containers from one direction in the horizontal plane only, thereby necessitating a high degree of maneuvering on the track system during ‘digging’ operations and transport to port. Moreover, the cantilever design forces these vehicles to ports and/or boundary grid columns arranged at one particular side of the storage grid, thereby further reducing the overall efficiency of the system. 
     In view of the above, it is desirable to provide a vehicle operating on an automated storage and retrieval system, and a method thereof, that solves or at least mitigates one or more of the aforementioned problem related to use of prior art storage and retrieval systems. 
     SUMMARY OF THE INVENTION 
     The present invention is set forth and characterized in the main claims, while the dependent claims describe other characteristics of the invention. 
     In particular, the invention concerns an automated storage and retrieval system comprising a track system comprising a first set of parallel tracks arranged in a horizontal plane (P) and extending in a first direction (X) and a second set of parallel tracks arranged in the horizontal plane (P) and extending in a second direction (Y) which is orthogonal to the first direction (X). The first and second sets of tracks form a grid pattern in the horizontal plane (P) comprising a plurality of adjacent grid cells, each comprising a grid opening defined by a pair of neighboring tracks of the first set of tracks and a pair of neighboring tracks of the second set of tracks. The system further comprises a plurality of stacks of storage containers arranged in storage columns located beneath the track system, wherein each storage column is located vertically below a grid opening and one or more vehicles, each comprising a storage container lifting device for lifting and lowering storage containers stacked in the stacks, a drive system comprising a wheel arrangement, a base/Base onto which the wheel arrangement is connected, a rotational part rotationally connected via a swivel device to the base having a rotational axis (R) preferably directed perpendicular to the horizontal plane (P) and preferably a rotational drive system for rotating the rotational part relative to the base. The drive system is configured to drive the vehicle along the track system in the first direction (X), the second direction (Y) or both. The storage container lifting device is preferably connected to the rotational part. 
     The vehicle may advantageously also comprise one or more registration devices configured for acquiring any information related to content/items within a storage container situated on top of a stack during operation, for example any recording device such as a camera that allows acquisition of live and/or still images of contents within any storage containers. The registration device should be arranged such that free sight towards the track system is ensured at least part of the operational time of the vehicle, for example when the vehicle is void of any storage containers. 
     Alternatively, or in addition, the vehicle may further comprise one or more dedicated registration devices for acquiring data related to the position of the vehicle relative to the track system during operation. As for the registration device(s) for the content of the storage containers, positional registration device(s) should also be arranged on the vehicle such that free sight towards the track system is ensured at least part of vehicle&#39;s operational time. Example of locations for both type of registration devices is on the rotational part and/or the base and/or the wheel arrangement. A registration device is herein defined as any device that may acquire positional and/or visual information of the environment surrounding the vehicle. 
     The possibility to rotate the rotational part relative to the base and the wheel arrangements increases the possible registration/sweeping area of the vehicle. 
     The rotational part preferably further comprises a bulk section rotationally connected to the base and a protruding section extending horizontally in the first direction (X) from the bulk section to form a container receiving space confined in height by the vertical distance from the track system to the protruding section and in the horizontal plane (P) to the horizontal extent of the protruding section. In this particular configuration, the storage container lifting device is arranged at least partly below the protruding section. The above-mentioned registration device(s) may for this design be arranged on the sides and/or beneath the protruding section, for example connected to the storage container lifting device. The latter exemplary position is particularly relevant in case of registration device(s) such as a camera allowing live and/or still images of content within a storage container. 
     In addition to a protruding section extending horizontally in the first direction (X) from the bulk section the vehicle may also in another embodiment comprise a second protruding section extending horizontally in the first direction (X) from the bulk section opposite of the first protruding section, forming a second container receiving space with the same confined in height and in the horizontal plane (P) as for the first container receiving space. As for the first protruding section, the storage container lifting device may be arranged at least partly beneath the second protruding section. This particular embodiment including two or more protruding sections enables handling of a plurality of storage containers in each operation, thereby increasing the rate storage containers may be handled relative to the above mentioned prior art vehicles with cantilever design or ‘single cell’ design when operating the above-mentioned storage and retrieval system. 
     In an advantageous configuration the drive system comprises a first wheel arrangement configured to guide the vehicle along the track system in the first direction (X). The first wheel arrangement comprises preferably four wheels or two belts arranged with their rotational axes in the second direction (Y). Further, in order to increase the overall stability of the vehicle during operation, i.e. transport and storage container handling, the first wheel arrangement may have a length in the first direction (X) that is longer than the distance between a pair of neighboring track of the second set of tracks. 
     However, such an increased stability may also be achieved by adding additional weight to the bulk section. The latter alternative may be preferable in order keep the drive system within a footprint of grid cell, thereby allowing other vehicles to pass on all neighboring grid cells if there is synchronized rotation of the rotational part. For example, when a vehicle is approaching a neighboring grid cell into which another vehicle&#39;s protruding section is extended, the rotational part of the latter vehicle may rotate at least 90° in order to clear the drive path of the former vehicle. 
     The drive system may further comprise a second wheel arrangement configured to guide the vehicle along the track system in the second direction (Y). As for the first wheel arrangement, the second wheel arrangement comprises preferably four wheels or two belts arranged with their rotational axes in the first direction (X). The second wheel arrangement have preferably a length in the second direction (Y) being equal or shorter than the distance between a pair of neighboring track of the first set of tracks. 
     In another advantageous configuration the vehicle further comprises a replaceable power source coupled to the rotational part, for example a replaceable power source with a corresponding charging station as described and illustrated in patent publication WO 2015/104263 A2. 
     The invention also concerns a vehicle suitable for lifting and transporting storage containers stacked in stacks within the above disclosed automated storage and retrieval system. The inventive vehicle is configured to move on the track system above the storage columns and comprises a storage container lifting device for lifting storage containers stacked in the stacks, a drive system comprising a wheel arrangement, a base onto which the wheel arrangement is connected, a rotational part rotationally connected via a swivel device to the base and a rotational drive system for rotating the rotational part relative to the base. The drive system is configured to drive the vehicle along the track system in at least one of the first direction (X) and the second direction (Y). 
     The invention also concerns a method of operating an automated storage and retrieval system as described above, where method comprises the steps of:
         selecting/identifying, by for example entering one or more particular items in a dedicated software, a target storage container within a target storage column comprising the target storage container with the particular item(s) and at least one non-target storage container,   operating the drive system to maneuver the vehicle in the horizontal plane (P) such that the storage container lifting device is arranged directly above the grid opening of the target storage column into which the selected target storage container is arranged,   lifting the topmost storage container of the target storage column fully above the track system by use of the storage container lifting device.       

     If the topmost storage container is identified as a non-target storage container, the method further comprises the steps of:
         locating an available non-target storage column within the system onto or into which the non-target storage container may be arranged and   arranging the storage container lifting device with the non-target storage container directly above the grid opening of the non-target storage column by operating the drive system to maneuver the vehicle in the horizontal plane (P) or operating the rotational drive system to rotate the rotational part relative to the base or a combination thereof and   repeating the method steps involving the non-target storage container until the topmost storage container of the target storage column is the selected target storage container.       

     When the topmost storage container is identified as the target storage container, the method further includes transporting the topmost storage container, i.e. the target storage container, to a drop-off port within or adjacent to the track system. 
     In the following, numerous specific details are introduced by way of example only to provide a thorough understanding of embodiments of the claimed system, vehicle and method. One skilled in the relevant art, however, will recognize that these embodiments can be practiced without one or more of the specific details, or with other components, systems, etc. In other instances, well-known structures or operations are not shown, or are not described in detail, to avoid obscuring aspects of the disclosed embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Following drawings are appended to facilitate the understanding of the invention. 
         FIG. 1  is a perspective view of a grid of a prior art automated storage and retrieval system. 
         FIG. 2  is a perspective view of a prior art container handling vehicle having a centrally arranged cavity for containing storage containers therein. 
         FIG. 3  is a perspective view of a prior art container handling vehicle having a cantilever for containing storage containers underneath. 
         FIG. 4  is a top view of a prior art single rail grid. 
         FIG. 5  is a top view of a prior art double rail grid. 
         FIGS. 6( a )-( c )  shows in a perspective view, a side view and a top view, respectively, a container handling vehicle of a first embodiment of the invention operating on double rail grid cells of an automated storage and retrieval system. 
         FIG. 7  is a side view of the storage container filled automated storage and retrieval system seen along the X direction, where two container handling devices as shown in  FIG. 6  are arranged side by side on double rail grid cells. 
         FIGS. 8( a )-( c )  shows the container handling vehicle of  FIGS. 6 and 7  in a perspective view, a side view and a top view, respectively, where the rotational part of the container handling vehicle has been rotated 180°. 
         FIG. 9  is an exploded perspective view of the container handling vehicle of  FIG. 6-8 . 
         FIG. 10  is a perspective view of the container handling vehicle of  FIG. 6-9 , wherein the rotational part of the container vehicle has been rotated 45°. 
         FIG. 11  is a perspective view of the container handling vehicle of  FIG. 6-10 , wherein a lifting device of the container handling vehicle has been lowered into a storage column of an automated storage and retrieval system 
         FIGS. 12( a )-( c )  show in a perspective view, a side view and an end view, respectively, a container handling vehicle of a second embodiment of the invention operating on double rail grid cells of an automated storage and retrieval system. 
         FIGS. 13( a )-( b )  are perspective views from two different angles of a container handling vehicle of a third embodiment of the invention. 
         FIGS. 14( a )-( b )  are side views of the container handling vehicle in  FIG. 12  seen along the Y direction and the X direction, respectively. 
         FIG. 15  is an exploded perspective view of a lifting device capable of lifting a single storage containers in one lifting operation. 
         FIG. 16  is a perspective view of a lifting device capable of lifting a plurality of storage containers in one lifting operation. 
     
    
    
     In the drawings, like reference numerals have been used to indicate like parts, elements or features unless otherwise explicitly stated or implicitly understood from the context. 
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following, embodiments of the invention will be discussed in more detail by way of example only and with reference to the appended drawings. It should be understood, however, that the drawings are not intended to limit the invention to the subject-matter depicted in the drawings. 
     If not otherwise stated, the framework  100  of the automated storage and retrieval system  1  is constructed in accordance with the prior art framework  100  described above in connection with  FIGS. 1-5 , i.e. a number of upright members  102  and a number of horizontal members  103  which are supported by the upright members  103 , and further that the framework  100  comprise the track system  108  of parallel tracks  110 , 111  in X direction and Y direction arranged across the top of storage columns  105 /grid columns  112 . The horizontal area of a grid column  112 , i.e. along the X and Y directions, may be defined by the distance between adjacent rails  110  and  111 , respectively (see also  FIGS. 4 and 5 ). 
     In  FIG. 1  the grid  104  is shown with a height of eight cells. It is understood, however, that the grid  104  in principle can be of any size. In particular it is understood that grid  104  can be considerably wider and/or longer and/or deeper than disclosed in  FIG. 1 . For example, the grid  104  may have a horizontal extent of more than 700×700 grid cells and a depth of more than twelve grid cells. 
     One embodiment of a container handling vehicle  3  according to the invention will now be discussed in more detail with reference to  FIGS. 6 to 9 . 
     Each container handling vehicle  3  comprises a rotational part  30  rotationally coupled onto a base  31  via a swivel device  32 . A drive system  18  is fixed to the base  3  enabling lateral/horizontal movement of the container handling vehicle  3 , i.e. the movement of the vehicle  3  in the X and Y directions on the track system  108  of the storage grid  104 . 
     The drive system  18  comprises a first set of wheels  19  arranged to engage with a pair of tracks  110   a , 110   b  of the first set of tracks  110 , and a second set of wheels  20  arranged to engage with a pair of tracks  111   a , 111   b  of the second set of tracks  111  (see  FIGS. 4 and 5 ). At least one of the set of wheels  19 ,  20  can be lifted and lowered so that the first set of wheels  19  and/or the second set of wheels  20  can be brought to engage with the respective set of tracks  110 ,  111  at any one time. 
     Each set of wheels  19 ,  20  comprises four wheels  19   a ,  19   b ,  19   c ,  19   d ;  20   a ,  20   b ,  20   c ,  20   d  arranged along the sides of the vehicle  3 . Wheels  19   a  and  19   b  are arranged in a first vertical plane, and wheels  19   c  and  19   d  are arranged in a second vertical plane which is parallel to the first vertical plane and arranged at a distance from the first vertical plane which corresponds to the distance between rails  110   a  and  110   b . Wheels  20   a  and  20   b  are arranged in a third vertical plane, which is orthogonal to the vertical planes in which wheels  19   a - 19   d  are arranged, and wheels  20   c  and  20   d  are arranged in a fourth vertical plane which is parallel to the third vertical plane and arranged at a distance from the third vertical plane which corresponds to the distance between rails  111   a  and  111   b.    
     At least one of the wheels in each set  19 ,  20  may be motorized in order to propel the vehicle  3  along the track system  108 . At least one motorized wheel in each set may include a hub motor, i.e. an electric motor that is coupled to, or incorporated into, the hub of a wheel and which drives the wheel directly. An example of a container handling vehicle with such a motor is disclosed in WO2016/120075A1, the contents of which are incorporated herein by reference. In an alternative example, at least one of the wheels  19   a - d ; 20   a - d  is a passive wheel propelled by one or more motors situated within the base  31  and/or the rotational part  30  and/or the swivel device  32  of the vehicle  3 . A drive system  18  involving a combination of hub motor(s) and external situated motor(s) may also be envisaged. 
     Each rotational part  30  comprises a bulk section  30   b  and a protruding section, hereinafter called cantilever  30   a , extending horizontally in the X direction. In the particular embodiment shown in  FIGS. 6-9  the cantilever  30   a  is formed by fixing cantilever beams  30   c  onto each vertical sides of a vehicle framework  30   d  at or near the vehicles  3  uppermost part. Both the vehicle framework  30   d , constituting part of the rotational part  30 , and the cantilever beams  30   c  are covered by two parallel vertical side covers  39  oriented along the direction of the cantilever beams  30   c , a vertical front cover  37  oriented perpendicular to the direction of the cantilever beams  30   b , a vertical back cover  38  oriented perpendicular to the direction of the cantilever beams  30   c  covering the rotational part  30  below the cantilever  30   a  and a horizontal top cover  36  covering the entire footprint of the vehicle  3 , i.e. the horizontal extent of the vehicle  3  seen from above. 
     The bulk section  30   b  may contain bulky components such as a vehicle battery  40 , a control panel  35 , and any motors  15   a  operating the vehicle  3 . 
     The vehicle battery  40  may be fixed into the bulk section  30   b  by fastening means. Further, the vehicle  3  may include a charging socket  41  coupled to the battery  40  in order to allow battery recharging at a dedicated charging station within the automated storage and retrieval system  1 . Alternatively, or in addition, the vehicle  3  may be equipped with a replaceable battery  40 , for example a replaceable battery having a corresponding battery slot  40   a  within the vehicle  3 , for example within the bulk section  30   b , and a battery opening  40   b  having a size allowing the replaceable battery  40  to be guided through. The battery opening  40   b  is for example in the front cover  37 . The corresponding charging stations and the battery exchange mechanisms may be the same as the charging stations and exchange mechanisms as disclosed in the international patent publication WO 2015/104263, which contents are incorporated herein by reference. Particular reference is made to the disclosure of the battery exchange mechanism in WO 2015/104263 referring to  FIGS. 7-9 . 
     Since the bulk section  30   b  of the rotational part  30  does not need to allocate any space for a storage container  106 , the design of the vehicle  3  allows larger batteries to be mounted/coupled in/to the vehicle  3 . 
     The rotation part  30  comprises a storage container lifting device  16  arranged within and/or below the cantilever  30   a  for vertical transportation of a storage container  106 , e.g. lifting a storage container  106  from a storage column  105  and bringing it to a position in a container receiving space  33  between the underlying rail system  108  and the cantilever  30   a , and also for lowering a storage container  106  from the container receiving space  33  into a storage column  105 . The lifting device  16  comprises one or more lifting shafts  15  connected to one or more lifting motors  15   a  ensuring rotational power to the lifting shafts  15 , one or more lifting belts  14  rotationally attached to the lifting shaft  15  and a lifting plate  13  attached at its upper face to the end of the lifting belts  14  not attached to the respective lifting shaft  15 . The lifting shafts  15 , the lifting motors  15 a and the lifting belts  14  are configured to allow winding on to/out from the lifting shaft  15  during operation by the lifting motors  15   a , thereby allowing lifting and lowering of the lifting plate  13 , i.e. adjusting the lifting plate  13  in a third direction Z which is orthogonal to the first direction X and the second direction Y. The lifting device  16  further comprises one or more engagement devices or gripping devices  12  and one or more guiding pins  17  arranged at the lower face of the lifting plate  13 . The engagement devices  12  are configured to grip or engage the storage container  106  for lifting/lowering, and the guiding pins  17  are configured to ensure sufficiently accurate positioning of the lifting device  16  in respect of the storage container  106  during lifting/lowering operations. 
     In the embodiment shown in  FIGS. 6-9  the lifting device  16  comprises two lifting shafts  15  arranged within the cantilever  30   a  in the direction of the cantilever beams  30   b  at or near each vertical sides of the vehicle, two lifting belts  14  arranged at or near the ends of each lifting shafts  15  for allowing winding thereon and where the ends of each belt  14  distal to the lifting shafts  15  is attached at or near the four corners on the upper face of the lifting plate  13 . Each lifting shaft  15  is operated by a dedicated lifting motor  15   a  arranged within the rotational part  30  outside the cantilever  30   a . The lifting shafts  15  may also be arranged immediately above and/or beneath the cantilever  30   a.    
     Conventionally, and also for the purpose of this application, Z=1 identifies the uppermost layer of the storage grid, i.e. the layer immediately below the track system  10 , Z=2 the second layer below the track system  10 , Z=3 the third layer etc. The container handling vehicles  3  can be said to travel in layer Z=0. Consequently, each storage column can be identified by its X and Y coordinates, and each storage position in the storage grid can be identified by its X, Y and Z coordinates. 
     When a storage container  106  stored in the storage grid  104  is to be accessed, one of the container handling vehicles  3  is instructed to retrieve the target storage container  106  from its position in the storage grid  104  and to transport the target storage container  106  to an access station (not shown) where it can be access from outside of the storage grid  104  or transferred out of the storage grid  104 . This operation involves moving the container handling vehicle  3  to a position where the cantilever  30   a  is positioned directly above a grid opening  115  of a storage column  105  in which the target storage container  106  is positioned and retrieving the storage container  106  from the storage column  105  using the container handling vehicle&#39;s lifting device  16 . This step involves using the lifting device  16  to lift the storage container  106  from the storage column  105  through the grid opening  115  and into the container receiving space  33  of the vehicle  3 . 
     If the target storage container  106  is located deep within a stack  107 , i.e. with one or a plurality of other storage containers positioned above the target storage container  106 , the operation also involves temporarily moving the above-positioned storage containers prior to lifting the target storage container  106  from the storage column  105 . This step, which is sometimes referred to as “digging” within the art, may be performed with the same container handling vehicle  3  that is subsequently used for transporting the target storage container  106  to the access station, or with one or a plurality of other cooperating container handling vehicles. Alternatively, or in addition, the automated storage and retrieval system  1  may have container handling vehicles specifically dedicated to the task of temporarily removing storage containers from a storage column. Once the target storage container  106  has been removed from the storage column  105 , the temporarily removed storage containers can be repositioned into the original storage column  105 . However, the removed storage containers may alternatively be relocated to other storage columns. 
     Once the target storage container  106  has been brought into the container receiving space  33  of the container handling vehicle  3  immediately below or partly into the cantilever  30   a , the vehicle  3  transports the storage container  106  to the access station where it is unloaded. The access station may typically comprise a grid location at the periphery of the storage grid  104  where the storage container  106  can be accessed manually or transported further using a suitable conveyor system. 
     When a storage container  106  is to be stored in the storage grid  104 , one of the container handling vehicles  3  is instructed to pick up the storage container  106  from a pick-up station (not shown), which may also double as an access station, and transport it to a grid opening  115  above the storage column  105  where it is to be stored. After any storage containers positioned at or above the target position within the storage column stack  107  have been removed, the container handling vehicle  3  positions the storage container  106  at the desired position. The removed storage containers may then be lowered back into the storage column  105 , or relocated to other storage columns within the storage grid  104 . 
     The cantilever  30   a  and/or the suspended lifting device  16  may also hold one more sensors  21  and/or one or more cameras  21 , preferably down-looking sensors  21  and/or cameras  21 . The sensors may be used to establish the position of the vehicle on the track system  108 , e.g. the alignment of the vehicle vis-à-vis a grid opening  115  or to establish the position of the vehicle  3  vis-à-vis other vehicles on the track system  108 , e.g. when operating the vehicles as a train of vehicles, an operation considered beneficial for a cantilever type vehicle with a rotational part since a train of vehicles may be easily formed with a uniform direction of the cantilevers by simple rotations. 
     A camera opens up additional possibilities such as visual inspection of the contents within a storage container, which images may be sent to the user/customer via the control system. Hence, when searching for one or more specific items, the user and/or customer may have access to an image of the position, orientation and size within a storage container  106 . The sensors and/or cameras may be arranged on the lower face of the cantilever  30   a  such that free sight to the underlying track system is ensured, at least part of the operational time. Further, the cameras may alternatively, or in addition, be arranged on the storage container lifting device  16  enabling free sight into at least the topmost storage container  106  within a storage column  105 . The ability to rotate the rotational part  30  further increases the usability of said sensors or cameras since it enables sweeping over larger areas within the system  1 . 
     Of course, one or more cameras and/or sensors may be mounted elsewhere on the vehicle  3 , for example in order to gain information of zones along and/or above the framework  100 . For example, a camera may be mounted on top of the vehicle  3  and/or on an antenna of the vehicle  3 . 
       FIG. 15  shows an example of a lifting device  16  comprising a lifting plate  13 , a plurality of gripping devices  12  for gripping/engaging with a storage container  106  and a plurality of guiding pins  17  for aligning the lifting device  16  with the storage container  106 . The lifting plate  13  further comprises a top cover  13   a , a base cover  13   b  and one or more cameras  21  installed on the lifting plate  13 , preferably within the base cover  13   b . The one or more cameras  12  are configured to record and register images of products arranged below the lifting device  16 , i.e. into the framework structure  100  and underlying storage containers  106 . 
     For monitoring and controlling the automated storage and retrieval system  1  so that a desired storage container  106  can be delivered to the desired location at the desired time without the container handling vehicles  3  colliding with each other, the automated storage and retrieval system comprises a control system (not shown), which typically is computerized and comprises a database for monitoring and controlling e.g. the location of the respective storage containers  106  within the storage grid  104 , the content of each storage container  106  and the movement of the container handling vehicles  3 . 
     The container handling vehicles  3  typically communicates with the control system from a control panel  35 , typically arranged on top of the vehicle  30  as shown in  FIGS. 6-9 , via wireless communication means, e.g. via a WLAN operating under an IEEE 802.11 (WiFi) standard and/or utilizing a mobile telecommunication technology such as 4G or higher. 
     Each container handling vehicle  3  comprises a battery  40  which provides power to onboard equipment, including the lifting motor  15   a , the drive system  18  for the first and second wheel arrangements  19 ,  20  and onboard control and communications systems. 
     The wheels  19   a - 19   d ,  20   a - 20   d  are arranged around the periphery of the base  31  of the vehicle  3 , below the rotational part  30 . The vertical side walls  37 - 39  (see  FIG. 9 ) covering the sides of the rotational part  30  are in the first embodiment co-planar to the vertical planes in which the wheels  19   a - 19   d ;  20   a - 20   d  are arranged. Consequently, the bulk section  30   b , that is, the rotational part  30  excluding the cantilever  30   a , has a generally cuboid shape. 
     As is most apparent in  FIGS. 6( b ) and ( c ) ,  FIG. 7  and  FIGS. 8( b ) and ( c ) , the vehicle  3  of the first embodiment has a footprint in the X direction, i.e. the horizontal extent in the X direction seen from above, covering two grid openings  115  and a footprint in the Y direction, i.e. the horizontal extent in the Y direction seen from above, covering a single grid opening. 
     The consequence of the cantilever design described above is that, when the vehicle  3  is positioned above a grid opening  115 , e.g. to access a container  106  in the storage column  105  located vertically below the grid opening  115 , the cantilever  30   a  will extend over a neighboring grid opening  115 . Normally this would prevent a second vehicle from travelling over this neighboring grid cell, i.e. the grid cell into which the protruding section  27  of the first vehicle  3  extends, thereby potentially reducing the overall capacity of the automated storage and retrieval system  1 . 
     However, with the novel configuration of vehicle  3  other vehicles may be allowed to pass over a neighboring grid opening by rotating the rotation part  30 , and thereby the cantilever  30   a , 180° or more in respect of the base  31 , prior to, and/or during, the passing of the other vehicle(s). Proper timing of the rotation may be set by the control system. This embodiment is not shown in the accompanied figures. However, it may be implemented by simply removing a wheel arrangement protrusion  22  further explained below, see  FIGS. 6, 8, 9 and 11 , and reconfiguring the affected wheels  19   b ,  19   c  in order to ensure a footprint in both X and Y direction below the cantilever  30   a  laying within the size of a grid opening  115 . 
     A rotation of the rotating part  30  relative to the base  31  is illustrated in  FIGS. 6 and 8  showing a vehicle  3  initially in a position where the cantilever  30   a  is directed in a negative X-direction ( FIG. 6( a ) ) and after rotation of the rotational part  30  180°, resulting in a direction of the cantilever  30   a  along a positive X direction ( FIG. 8( a ) ). The rotation of the rotating part  30  is achieved by operating the swivel device  32  by a rotor activating motor  34 , preferably arranged within the base  31  ( FIG. 9 ). 
     To achieve further stability of the vehicle  3 , the first wheel arrangement  19  directed in the X direction has on each side of the vehicle  3 —a wheel arrangement protrusion  22  extending the total length of the first wheel arrangement  19 , and in particular the distance between each wheel pairs  19   a ,  19   b  and  19   c ,  19   d , beyond the footprint of the bulk section  30   b.    
     For both configurations, i.e. both without and with the wheel arrangement protrusion  22 , the possibility of rotating the cantilever  30   a  has significant advantages over the prior art cantilever design disclosed in NO317366. For example, due to the possibility to rotate the rotating part  30  180° or more, each vehicle  3  may transport storage columns  106  from/to port columns  119 ,  120  and/or conveyor belts situated at two facing vertical sides at the outer boundaries of the storage grid  104 . If the port columns and/or the conveyor belts are situated within the storage grid  104  as illustrated in  FIG. 1 , each vehicle  3  may transport storage containers  106  from/to ports/conveyor belts situated at all vertical sides at the outer boundaries of the storage grid  104 , i.e. vertical sides oriented both in X direction and Y direction. Another advantage in respect of the prior art cantilever design is that all novel vehicles  3  operating on the system  1  may access all storage columns  105 , also the storage columns  105  located at the outer boundaries of the storage grid  104 . 
       FIG. 10  shows the container handling vehicle  3  where the rotational part  30  has been rotated approximately 45° in the horizontal plane (P) relative to the X direction. 
     Further,  FIG. 11  shows the container handling vehicle  3  having the cantilever  30   b  directed along the positive X-direction and where the lifting device  16  has been lowered into the underlying framework  100 , towards the topmost storage container  106  of a stack  107 . 
       FIG. 12  shows a second embodiment of the invention where the rotational part  30  of the vehicle  3  comprises a bulk section  30   b  and two protruding sections  30   a  extending horizontally from the uppermost part of the bulk section  30   b . With the exception of having protruding sections  30   a  in both positive and negative X directions, the configuration of the vehicle  3  in the second embodiment is identical or near identical to the first embodiment, that is, with a storage container lifting device  16  arranged beneath the lower face of each protruding sections  30   a , where each lifting device  16  comprises one or more lifting shafts  15  connected to one or more lifting motors  15   a , one or more lifting belts  14  and a lifting plate  13 , and where the lifting plate  13  further comprises one or more engagement devices  12  and one or more guiding pins  17 . As is most apparent in  FIGS. 12( b ) and ( c ) , the vehicle  3  of the second embodiment has a footprint in the X direction covering three grid openings  15  and a footprint in the Y direction covering a single grid opening. As for the first embodiment, the vehicle battery  40  may either be fixed within the bulk section  30   b  or replaceable as exemplified in the patent publication WO 2015/104263 incorporated herein by reference. 
     In addition to the advantage concerning arrangement of ports and access to storage cells at storage grid boundaries, the vehicle  3  of the second embodiment also have the advantage of allowing simultaneous or sequential handling of a plurality of storage containers  106 , for example lowering a storage container at one side of the vehicle  3  while raising another storage container at the opposite side of the vehicle  3 . Or lowering/raising two storage containers simultaneously. Or lowering/raising two storage containers from/to the same storage column by rotating the rotational part 180°. 
     In both the first and second embodiment of the invention, the base  31  of the vehicle  3  is arranged fully within both the vertical and horizontal extent of the wheel arrangement  18 . Further, the vehicle battery  40  is arranged within, onto or under the bulk section  30   b  of the rotational part  30 .  FIGS. 13-14  shows a third embodiment of the invention where the base  31  extends above, or is arranged above, the wheel arrangement  18 . In this particular embodiment, at least some bulky components such as the vehicle battery  40  may advantageously be arranged onto or within the base  31  instead of the rotational part  30 . In  FIGS. 13-14 , a battery receiving structure  40   a  is shown on the vertical wall  37  of the vehicle&#39;s base  31  facing the negative X direction. When the vehicle battery  40  is to be replaced, the vehicle  3  moves to a dedicated charging station (not shown) and perform the battery exchange similar or equal to the battery exchange disclosed in WO 2015/104263 incorporated herein by reference. In order to avoid or reduce interference with the cantilever  30   a , the rotational part  30  may optionally rotate 90° relative to the base  31  prior to battery exchange with the charging station. Alternatively, the vehicle battery  40  may be mounted on the side walls. 
     As schematically illustrated in  FIG. 16 , a single storage container lifting device  16  may also handle a plurality of storage containers  106  may equipping the lifting device  16  with a number of engagement devices  12  such as claws or clips that corresponds to the total number of upper horizontal corner of the storage containers  106  to be picked by the vehicle  3  in the same picking operation.  FIG. 16  shows a specific example of 4×4 clips allowing up to four storage containers  106  to be picked in the same operation, assuming a 2×2 storage container configuration within a storage column. Each, some or all the clips in each lifting unit  6  may be remotely operated by a control system. As explained above, each corner of the lower face of the lifting plate  13  is preferably arranged with one or more guiding pins  17  to ensure adequate guiding of the engagement devices  12  on or into corresponding engagement device receiving structures. 
     In the preceding description, various aspects of an automated storage and retrieval system, a vehicle and a method according to the invention have been described with reference to the illustrative embodiment. However, this description is not intended to be construed in a limiting sense. Various modifications and variations of the illustrative embodiment, as well as other embodiments of the system, the vehicle and the method which are apparent to persons skilled in the art, are deemed to lie within the scope of the present invention as defined by the following claims. As an example, an automated storage and retrieval system may be envisaged where the above mentioned inventive cantilever vehicles operates in conjunction with prior art vehicles such as the central cavity vehicles disclosed in WO2014/090684A1, the single cell vehicles disclosed in WO2015/193278A1 and/or the non-rotational cantilever vehicles disclosed in NO317366, and where the cantilever of each inventive cantilever vehicles is high enough above the rail system to allow one or more of the prior art vehicles to drive under during operation. 
     REFERENCE NUMERALS 
     
         
           1  Automated storage and retrieval system 
           3  Vehicle, first embodiment 
           12  Gripping device/engagement device/claw/clip 
           13  Lifting plate 
           13   a  Top cover of lifting plate  13   
           13   b  Base cover of lifting plate  13   
           14  Lifting belt 
           15  Lifting shaft 
           15   a  Lifting motor 
           16  Storage container lifting device 
           17  Guiding pins 
           18  Drive system/wheel arrangement of vehicle  3   
           19  First wheel arrangement/first set of wheels/first drive system, first direction X 
           19   a  First wheel of first wheel arrangement  19   
           19   b  Second wheel of first wheel arrangement  19   
           19   c  Third wheel of first wheel arrangement  19   
           19   d  Fourth wheel of first wheel arrangement  19   
           20  Second wheel arrangement/second set of wheels/first drive system, second direction Y 
           20   a  First wheel of second wheel arrangement  19   
           20   b  Second wheel of second wheel arrangement  19   
           20   c  Third wheel of second wheel arrangement  19   
           20   d  Fourth wheel of second wheel arrangement  19   
           21  Registration device/camera/sensor 
           22  Wheel arrangement protrusion for the first wheel arrangement  19   
           30  Rotational part of vehicle  3   
           30   a  Cantilever of rotational part  30 /protruding section 
           30   b  Bulk section 
           30   c  Cantilever beams 
           30   d  Vehicle framework 
           31  Base/stationary part of vehicle  3   
           31   a  Top cover to base 
           32  Swivel device 
           33  Container receiving space 
           34  Rotational drive means/rotation activating motor 
           35  Control panel/transmission means 
           36  Top cover of rotational part 
           37  Front cover of rotational part  30 /end section of the rotational part opposite the protruding section  30   a    
           37  Back cover of rotational part  30   
           39  Vertical side covers of rotational part  30   
           40  Vehicle battery 
           40   a  Slot for replaceable vehicle battery 
           40   b  Battery opening in front cover for access to battery  40   
           41  Charging socket/coupling point for replaceable battery 
           100  Framework structure 
           102  Upright members of framework structure 
           103  Horizontal members of framework structure 
           104  Storage grid 
           105  Storage column 
           106  Storage container 
           106 ′ Particular position of storage container 
           107  Stack 
           108  Rail system/track system 
           110  Parallel tracks in first direction (X) 
           110   a  First track of neighboring tracks  110   
           110   b  Second track of neighboring tracks  110   
           111  Parallel tracks in second direction (Y) 
           111   a  First track of neighboring tracks  111   
           111   b  Second track of neighboring tracks  111   
           112  Grid column 
           115  Grid opening 
           119  First port column/first port 
           120  Second port column/second port 
           122  Grid cell/storage cell 
           201  Prior art single cell storage container vehicle 
           201   a  Vehicle body of the storage container vehicle  101   
           201   b  Drive means/wheel arrangement, first direction (X) 
           201   c  Drive means/wheel arrangement, second direction (Y) 
           301  Prior art cantilever storage container vehicle 
           301   a  Vehicle body of the storage container vehicle  101   
           301   b  Drive means in first direction (X) 
           301   c  Drive means in second direction (Y) 
         X First direction 
         Y Second direction 
         Z Third direction 
         P Horizontal plane 
         R Rotational axis