Description

TECHNICAL FIELD

[1] The present disclosure is directed to the field of automatic ware- house logistics, more particularly to self-driven carriages for automati- cally storing and accessing containers in a storage rack arrangement, an automatic storage system and a method for automatically storing and retrieving containers in racks of a storage rack arrangement. BACKGROUND

[2] Automatic storage systems with self-driven carriages are known in the prior art. Such arrangements comprise storage levels, which can be connected by a lift. A lift is comparably complex and limits the through- put of the storage and retrieval system. A storage system with a lift typi- cally comprises a number of moving and thus constructively demanding parts.

[3] US 2017/0050803A1 discloses an alternative storage system. To connect different storage levels with each other a belt conveyor instead of a lift is suggested. The belt conveyor conveys objects along ramped sections of the conveyor to interaction sites on a storage level, where the objects can be picked up by carriages that move along horizontal aisle tracks. [4] The carriages are bound to their storage level and cannot change the storage level. The object to be transported changes the storage level by means of the belt conveyor, The object to be transported needs to be handed over at least when the object is put on the belt conveyor to be moved from one storage level to another storage level, when the object is picked up by a carriage at the storage level where it is to be moved to, and potentially when the object is handed over from the carriage to the storage site. Handing over the object is time consuming, and the carriage or the belt conveyor could be idle, depending on the demand to move an object on a certain storage level.

[5] A track arrangement with a lift and/or a belt conveyor are limited in their efficiency by idle phases of the carriages, the belt conveyor, and/or the lift when handing over objects at the belt conveyor or the lift, respectively. Thus, the carriages, the belt conveyor, and/or the lift are lim- ited in their occupancy. The belt conveyor and the lift are constructively demanding and the cost-efficiency of such an arrangement can be im- proved. It is thus desirable to avoid the limitation of the complexity of a lift or a belt conveyor.

[6] EP 3370194 A1 discloses a warehouse management system with ramps instead of a lift. A plurality of carriages can traverse the track ar- rangement on any of the storage levels. The carriages can change the storage level of the rack arrangement by ramps which connect adjacent storage levels. The tracks and the ramps ore arranged so that each car- riage can follow a putative best route between its current position and, e.g., an object and/or a storage site. More than one carnage can choose a route with a driving direction opposite to the driving of another carriage. Therefore, carriages can potentially crash with each other. To avoid such a crash, a carriage can recalculate and change its route. The change of a route implies that the formerly chosen putative best route has potentially not been optimal and that the carriage has chosen a route which is longer than necessary. Due to the presence of a plurality of carriages and potential online scheduling of routes by the self-driven car- riages, such a potential crash can hardly be determined in advance. Due to the change of the route, the time-consumption to transport on object can increase in a manner that is hardly to be predicted. This can reduce the occupancy of the interaction site and the overall efficiency of the storage system.

[7] WO 2005/077789 A 1 and WO 2016/010429 A 1 disclose warehouse management systems with vehicles that are capable of driving on a two- dimensional horizontal track grid on a certain level, wherein the vehicles change the level by means of one or more lifts.

SUMMARY

[8] It is a problem of the present disclosure to transport objects se- curely and efficiently in a storage rack arrangement for automatically storing and accessing objects, which is cost-effective and avoids limita- tions of the occupancy when transporting, storing and retrieving ob- jects.

[9] The problem is solved by a self-driven carriage for automatically storing and accessing containers in a storage rack arrangement ac- cording to the present disclosure, a storage system according to the present disclosure, and a method for automatically storing and access- ing containers in a storage rack arrangement according to the present disclosure.

[10] According to a first aspect of the present disclosure, a self-driven carriage is provided for automatically storing and accessing containers in a storage rack arrangement, wherein the carriage comprises a first wheel set for driving along a first axis and a second wheel set for driving along a second axis extending transverse to the first axis, wherein at least one of the first wheel set and the second wheel set is essentially vertically movable between a driving position and on idle position, wherein the lower one of the first wheel set and the second wheel set is in the driving position and the upper one of the first wheel set and the second wheel set is in the idle position. The carriage further comprises a support surface for carrying a bottom surface of a container, wherein the carriage further comprises a centring and securing system for cen- tring and securing a container on the support surface, wherein the cen- tring and securing system comprises at least two engaging elements being simultaneously movable in opposite directions to each other be- tween an idle position and a securing position, wherein the engaging elements are configured to engage, in the securing position, with the container for securing the container on the support surface. [11] The carriage according to the first aspect of the present disclo- sure is thus able to securely and efficiently transport a container that may be empty or at least partly filled with one or more containers along ramps for changing between levels of the storage system. There is thus no need for complicated and costly lifts. Furthermore, the carriages con be designed to have a relatively flat shape so that the carriages can drive below the containers in the rack with a higher vertical ware- house density, because the carriage movement space below the con- tainers limiting the vertical warehouse density can be reduced. The se- curing system allows for the carnages to be designed without a recess to receive and secure the container in or lateral support walls to secure the container between. Therefore, the containers need not be secured laterally at a side wali, but can be solely secured at the bottom surface of the container. This has a further beneficial effect that the carriage can thus be much more compact not only in height, but also in length and width. This is particularly advantageous for exchange, repair and maintenance of the carriages that can be shipped easily and cost-effi- ciently. Preferably, the first wheel set and/or the second wheel set are embedded into the outer contour of the carriage for a most compact design. However, it may be advantageous in particular for the first wheel set if the wheels extend at least partially out of the outer contour of the carriage for securing the carriage against tipping over on sloped tracks. The centring and securing system effectively combines a secur- ing effect and a centring effect by the simultaneous motion of the en- gaging elements in opposite directions to each other. The container is thereby always centred on the carriage and securely fastened without lateral fixations.

[12] The simultaneous motion of the engaging elements in opposite directions to each other may be a translational or a rotational motion, or a combination thereof. Preferably, the motion of the engaging ele- ments is at least partly directed outward, i.e. away from a central verti- col symmetry axis and/or a central vertical symmetry plane of the car- riage. The centring effect of the simultaneous motion of the engaging elements in opposite directions is thus preferably achieved in a horizon- tal plane, i.e. along the first axis and/or along the second axis. The en- gaging elements are preferably arranged in a symmetric arrangement to each other, i.e. preferably plane-symmetric with respect to a vertical plane through the first axis or the second axis, or circular symmetric with respect to a central vertical symmetry axis of the carriage. Correspond- ingly, the engaging elements preferably move symmetrically between the idle position and the securing position.

[13] If the container is not centred on the support surface before the engaging elements have reached the securing position, an engaging element on one symmetry side will touch the container earlier than an engaging element on the opposite symmetry side. Thereby, the touch- ing engaging element moves the container towards the centre until the engaging element on the opposite symmetry side engages with the container so that both engaging elements secure the container in a central position on the support surface. In other words, the at least two engaging elements preferably form a mutually corresponding pair of symmetrically arranged and movable engaging elements. In an alter- native embodiment, the motion of the engaging elements may be at least parity directed inward, i.e. towards a central vertical symmetry axis and/or a central vertical symmetry plane of the carriage.

[14] Optionaiiy, the engaging elements may be positioned vertically below the support surface in the idle position and vertically above the support surface in the securing position. Therefore, the vertical position of the support surface may determine the total height of the carnage, at least in the idle position of the support surface. When an empty car- riage enters a rack to pick up a container, the carriage may thus be as flat as possible. Thereby, the vertical warehouse density con be in- creased. The containers may be significantly higher than the carriages, e.g. 1.5 times higher or more.

[15] Optionally, the support surface may hove a distance to the ends of the carriage along the second axis. This is particularly advantageous if the carriages enter the racks along the first axis and the containers are placed on rack fillets extending along the first axis. When a con- tainer is stored at a storage site, the ends of the bottom surface of the container along the second axis may rest on a pair the rack fillets ex- tending along the first axis, whereas the rest of the bottom surface may be freely accessible from below. Therefore, the distance of the support surface to the ends of the carriage along the second axis leaves space for the rack fillets. In other words, the length of the support surface along the second axis is preferably smaller than the distance between the pair of rack fillets in order to be able to fit between the rack fillets for lifting and/or lowering the container from below.

[16] Optionally, the engaging elements may be mechanically cou- pled with each other and driven by one securing motor. This is efficient in terms of space consumption and production cost. Furthermore, the mechanical coupling between the engaging elements may ensure that they are always simultaneously driven in opposite directions to each other between the idle position and the securing position. [17] Optionally, the support surface may comprise at least three con- tact points for securely supporting a bottom surface of a container from below. Optionally, the support surface may be essentially vertically movable relative to the lower one of the first wheel set and the second wheel set being in the driving position. The support surface may be movable relative to only one of the first wheel set and the second wheel set or both. Therefore, the support surface may be passively movable relative to only one of the first wheel set and the second wheel set by the movement of said wheel set. it may thus have a fixed position relative to the other wheel set. Preferably, the support surface is actively movable relative to both wheel sets and the rest of the car- riage. Thereby, the vertical positioning of the support surface is inde- pendent of the vertical positioning of any of the wheel sets.

[18] Optionally, the first wheel set and/or the second wheel set are essentially vertically movable by at least one lift motor. Preferably, only one of the wheel sets is vertically movable by the at least one lift motor relative to the rest of the carriage. Similarly, the support surface may be essentially vertically movable by the same or another one of the at least one lift motor. Preferably, there are two separate lift motors for the moving the wheel set(s) and for moving the support surface.

[19] Optionally, the first wheel set and the second wheel set are driven by one drive motor. Optionally, the first wheel set and second wheel set may be driven simultaneously when the lower one of the first wheel set and the second wheel set is in the driving position and the upper one of the first wheel set and second wheel set is in the idle posi- tion. This is particularly efficient in terms of space consumption and cost. The power consumption for driving the idle wheel set is marginal only. [20] Optionally, the first wheel set and the second wheel set may be mechanically coupled to first wheel set and the second wheel set may be by a gear system, wherein the gear system is operable with a first gear ratio and a second gear ratio, wherein the gear system is config- ured for driving the first wheel set with the first gear ratio and for driving the second wheel set with the second gear ratio, wherein the first gear ratio is at least two times, preferably at least three times, larger than the second gear ratio. This is a second aspect of the present disclosure that is particularly advantageous in combination with the first aspect, i.e. the centring and securing system of the carriage, because it allows to climb ramps along the first axis both efficiently and safely. However, this second aspect of the present disclosure is also advantageous inde- pendent from the first aspect, i.e. the centring and securing system of the carriage, because it may enable the carriage to climb steeper ramps along the first axis.

[21] Optionally, all wheels of the first wheel set and/or the second wheel set may be coupled to the drive motor to be driven simultane- ously. In particular a four-wheel drive for the first wheel set may be ben- eficial for climbing ramps.

[22] Optionally, the centring and securing system comprises at least one securing motor for simultaneously moving the at least two engag- ing elements in opposite directions to each other between the idle po- sition and the securing position. The of least one securing motor is pref- erably one of three motors of the carriage in total, i.e. the drive motor, the lift motor and the securing motor. All motors of the carriage may be fed by the same rechargeable battery or different rechargeable bat- teries on board of the carriage.

[23] Optionally, the first wheel set may have a first wheel base and the second wheel set may have a second wheel base, wherein the second wheel base is significantly larger than the first wheel base. This is a third aspect of the present disclosure that is particularly advanta- geous in combination with the first and/or second aspect, because it provides a better ground clearance for entering and leaving ramps along the first axis and thereby allows for a more efficient and safer transport of the containers on romps along the first axis. However, this third aspect of the present disclosure is also advantageous independ- ent from the other aspects, because it may enable the carnage to en- ter/leave steeper ramps along the first axis. [24] Optionally, the length of the carriage along the second axis is significantly longer than the width of the carnage along the first axis. This is particularly advantageous in combination with the above-men- tioned third aspect of a larger wheel base of the second wheel set. [25] According to another dependent or independent aspect of the present disclosure, an automatic storage system is provided, comprising

- at least one self-driven carnage as described above, and

- a plurality of containers for being automatically stored and ac- cessed at storage sites in a storage rack arrangement extending over k storage levels, wherein each container comprises a bottom surface with receiving ele- ments corresponding to the engaging element of the at least one self- driven carriage, wherein the receiving elements of a container have the same arrangement to each other for all containers.

[26] It is particularly advantageous if all containers of the storage sys- tem have a standardised bottom surface with a defined arrangement of standardised receiving elements, so that a carriage con transport any of the carriages. The containers may have different heights, but have preferably the same lateral dimensions in length along the sec- ond axis and width along the first axis. [27] Optionally, the automatic storage system may further comprise a track arrangement comprising first rail tracks having a first track gauge and extending essentiaily along the first axis, and second rail tracks having a second track gauge and extending essentially along the second axis, wherein the first track gauge is significantly larger than the second track gauge. In order to reduce the risk for the carriages to lose the balance on the rail tracks, the track gauges are preferably as large as possible. This means that the wheels of both wheel sets are preferably located at the ends of the carriage along the first axis and the second axis, re- spectively. Thus, the difference between the track gouges is particularly beneficial in combination with the carriage being longer along the sec- ond axis than wide along the first axis.

[28] Optionally, the track arrangement may comprise at least z track levels, wherein z ³ k with k being the number of storage levels of the storage rack arrangement, an entry point on the track level for each interaction site, wherein m {1,....,z}, and an exit point on the n ^th track level for each interaction site, wherein n Î {1,....,z}. From the entry point, the interaction site can be reached by a carriage via tracks of the track arrangement. From the exit point, the interaction site can be left by a carriage via tracks of the track arrangement. The m ^th track level is called “entry point level" and the n ^th track level is called the “exit point level". The entry point level is the track level at which a track leads from the entry point to the interaction site. The exit point level is the track level at which a track leads from the interaction site to the exit point. The track level, at which the interaction site is arranged, is called "interaction site level". All track levels, or at least a subset of them, may correspond to the k storage levels of the storage rack arrangement. However, in some embodiments, the track arrangement may comprise auxiliary intermediate track levels in addition to the track levels that correspond to the storage levels. At an interaction site, a container car- ried by a carriage may be emptied and/or filled or otherwise pro- cessed. While the container is being processed, the one or more batter- ies of the carriage may be charged by charger module located at the interaction siie. The charging may be performed inductively or by an electrical connection with the charger module.

[29] According to the another dependent or independent aspect of the present disclosure, the track arrangement further comprises for each interaction site: z - m first one-way ramps directed downward to- wards the entry point, m - 1 second one-way romps directed upward towards the entry point, z - n third one-way ramps directed upward away from the exit point, and n - 1 fourth one-way ramps directed downward away from the exit point. Therein, a one-way ramp is a ramped track. A first one-way ramp is a ramped one-way track that ex- tends from track level z downward to z - 1, from z - 1 to z - 2. and from z - m + 1 to z - m. A second one-way ramp is a ramped one-way track that extends upward from track level 1 to 2, from 2 to 3, .... and from m - 1 to m. A third one-way ramp is a romped one-way track that extends upward from track level n to n + 1. from n 1 to n + 2, .... and from z - 1 to z. A fourth one-way ramp Is a ramped one-way track that extends downward from track ievel n to n - 1, from n - 1 to n - 2. and from 2 to 1. [30] The one-way ramps ensure that a carriage can change track levels effectively. A carriage on a track level can access any other track level by choosing a path along one or more of the one-way ramps which leads to the chosen storage level. A carriage can transport a container over one or more storage levels from the interac· tion site to a storage site, or from a storage site to the interaction site by the one-way ramps. i.e, a potentially time-consuming handing over of containers can be dispensed with. The throughput of the track arrangement is determined by the tracks and the carriages and is not limited by other transportation means, e.g. by a lift or a belt conveyor, and/or a carriage that is idle when waiting for said other transportation means. Thereby, the complexity and the construction of the track ar- rangement is comparably simple and comprises only one or more car- riages as movable parts which makes the track arrangement cost-ef- fective.

[31] The one-way ramps ensure that there is at least one first path, i.e. a route that a carriage can take, between a storage level and the in- teraction site so that a container can be moved from a storage site to the interaction site and at least one second path between the interac- tion site and any storage level so that a container can be moved from the interaction site to a storage site. This reduces the risk of a potential crash and therefore of a recalculation and change of a route.

[32] Optionally, for each interaction site, the entry point and the exit point may be arranged at an identical track level. In this embodiment, the interaction site can be reached from the same track level from where the interaction site can be left. This is particularly efficient, when a container is to be stored at and/or picked up from the storage level at which the interaction site is arranged. In this embodiment, the entry point level and the exit point level are identical per interaction site to improve the efficiency of the layout and construction of the track ar- rangement. in an alternative embodiment the entry point level can be different from the interaction site level. This can be particularly effective to provide a path without the risk of a coilision, e.g. when the track ar- rangement comprises exactly one route via one-way ramps between the entry point and the interaction site.

[33] Optionally, one or more of the first one-way ramps, of the sec- ond one-way ramps, of the third one-way ramps, and/or of the fourth one-way ramps may be arranged to connect adjacent track levels with each other. This embodiment provides a track arrangement that allows a carriage to move directly from one track level to an adjacent track level, i.e. from a track level n Î {1,....,z} to an upper track level n +

1 Î {1,....,z} and/or to a lower track level n - 1 Î {1,....,z}. This embodi- ment comprises shortest possible paths between adjacent storage lev- els.

(34] Optionally, one or more of the first one-way ramps, of the sec- ond one-way ramps, of the third one-way ramps, and/or of the fourth one-way ramps may be arranged to connect next-nearest track levels with each other and/or at least two track levels with each other having two or more track levels between said connected at least two track levels, i.e. such a one-way romp extends over at least three track levels but does not need to connect adjacent track levels. This embodiment provides a track arrangement that allows a carriage to move directly from one track level to a track level with at least one track level in be- tween, i.e. from a track level n Î {1,....,z} to on upper storage level n + s Î {1,....,z},s ³ 2 and/or to a lower storage level n - s Î {1,....,z}.s ³ 2. This embodiment can be particularly effective In providing a path to pre- vent a potential collision of carnages which improves the efficiency of transportation.

[35] Optionally, the first one-way ramps may comprise a first se- quence of first romps, the second one-way ramps may comprise a sec- ond sequence of second ramps, the third one-way ramps may com- prise a third sequence of third ramps and/or the fourth one-way romps may comprise a fourth sequence of fourth ramps. Preferably, a se- quence of ramps may be a plurality of one-way ramps, wherein an exit point of one one-way ramp is identical to or close to an entry point of a subsequent one-way ramp, i.e., a carnage con move along the se- quence of ramps while traversing sold one-way ramps without traversing longer tracks other than said one-way ramps. Advanta- geously, each subsequent pair of one-way ramps of a sequence of ramps is connected with each other by one or two horizontal connec- tion points. A sequence of ramps improves the efficiency of transport- ing a container from one level to another level by passing one or more levels in between.

[36] Optionally, the track arrangement may comprise a plurality of in- teraction sites to issue and/or retrieve a plurality of containers prefera- bly with a plurality of carriages simultaneously. The interaction sites can be arranged at an identical track level. Alternatively, at least two inter- action sites can be arranged at different track levels which can im- prove the performance of the automated storage and retrieval system, e.g. when one interaction site is arranged near storage sites which are accessed more frequently than other storage sites further away from said interaction site.

[37] Optionally, a first subset of first one-way romps, a second subset of second one-way ramps, a third subset of third one-way ramps, and/or a fourth subset of fourth one-way ramps may be configured to connect any one of the storage sites with exactly one interaction site. The first subset of first one-way ramps may comprise preferably z - m first one-way ramps directed downward towards the entry point of the Interaction that it connects to. it is possible that the track ar- rangement comprises a piura!ity of first subsets of first one-way ramps, wherein any two first subsets of first one-way ramps are configured to connect to different interaction sites. The second subset of second one- way ramps comprises preferably m - 1 second one-way ramps directed upward towards the entry point. The third subset of third one-way ramps comprises preferably z -n third one-way ramps directed upward away from the exit point. The fourth subset of fourth one-way ramps comprises preferably n - 1 fourth one-way romps directed downward away from the exit point. Similarly, as explained with reference to the first subset of first one-way ramps, the track arrangement can comprise a plurality of second subsets of second one-way tracks, third subsets of third one- way tracks and/or fourth subsets of fourth one-way tracks, wherein any two of said subsets of one-way ramps are configured to connect to dif- ferent interaction sites. This is particular effective since the risk of colli- sions of carriages on the routes from an entry point and its interaction site can be significantly reduced. [38] Optionally, for each interaction site, the first subset of first one- way ramps, the second subset of second one-way ramps, the third sub- set of third one-way ramps, and/or the fourth subset of fourth one-way ramps may be configured to connect any one of the storage sites with exactly one interaction site. This embodiment reduces the risk of coili- sions of carriages and provides the possibility of a modular arrange- ment of the track arrangement, i.e. the subsets of one-way ramps and the corresponding interaction sites can be repeated transversely to the aisle direction periodically along the rack arrangement, wherein each periodic repetition can comprise one or more of said subsets of one- way ramps and one or more interaction sites.

[39] Optionally, the track arrangement may comprise at least one bi- directional horizontal track connectable to all aisle tracks on each stor- age level. The bidirectional horizontal track can connect any aisle track with connection points, wherein a connection point connects the bidi- rectional horizontal track to one or more one-way ramps, i.e. a carriage can drive a path between a storage site and the interaction site by traversing the horizontal aisle track, the horizontal bidirectional track and one or more of the one-way ramps. The bidirectional horizontal track can connect one or more aisle tracks with one or more of the one-way ramps to provide a plurality of possible paths for the carnages. [40] Optionally, the track arrangement may comprise a first horizontal one-way track connectable to all aisle tracks on each storage level in a first driving direction. The first horizontal one-way track may prevent that carriages crash during traversing the horizontal one-way track. Therefore, a carriage can choose an optimal route, e.g, between the interaction site and the storage site. A recalculation and change of a route of a carriage can be dispensed with, which improves the effi- ciency of transportation of a container. [41] Optionally, the track arrangement may comprise a second hori- zontal one-way track connectable to all aisle tracks on each storage level in a second driving direction opposite to the first direction. The two horizontal one-way tracks of the track arrangement allow a movement of a carriage in any horizontal direction transverse to the aisle direction to move towards or away from an aisle efficiently on an optimal route.

[42] Optionally, on at least one storage level, the bidirectional hori- zontal track, the first horizontal one-way track and/or the second hori- zontai one-way track may extend transversely to the aisle direction to improve the construction of the track arrangement by providing a space-saving embodiment, which allows for short paths. This embodi- ment is particularly space saving in the aisle direction at a front face of the rack arrangement at which the track arrangement is arrangeable. [43] Optionally, the bidirectional horizontal track, the first horizontal one-way track and/or the second horizontal one-way track may be ar- ranged, in the aisle direction, between the aisle tracks and any of the first, second, third, and/or fourth one-way ramps. This embodiment comprises the minimum number of cross-sections of tracks and thereby provides a track arrangement with a minimum chance that two paths of carriages cross each other simultaneously. [44] Optionally, the first one-way ramps, the second one-way ramps, the third one-way ramps, and/or the fourth one-way ramps may have a driving direction transverse to the aisle direction to allow an effective arrangement of the one-way hacks that is space-saving and provides short paths.

[45] Optionally, the track arrangement may comprise at least one connection track, wherein the connection track extends in aisle direc- tion. The connection hack(s) may be bidirectional or unidirectional. The connection track may extend along the aisles to allow a carriage to drive towards and away from a storage site at the same section of the aisle track. In this embodiment, the track arrangement can be ar- ranged at one face, e.g., the front face, of the rack arrangement. The connection track can extend outside an aisle to provide an efficient change of different tracks.

[46] Optionally, the at least one connection track may comprise at least one connection point, wherein the connected point connects at least two of the following with each other: one or more horizontal tracks, one or more one-way romps, and/or the interaction site. i.e., a connection point is a horizontal track section, which connects different parts of the track arrangement, e.g., ramps and/or horizontal tracks, with each other. By aligning at least one connection point at a con- nection track an effective change of different tracks is possible. Prefer- ably, a connection track comprises a plurality of connection points to allow an effective change between a plurality of different hacks on a shortest path.

[47] Optionally, subsequent first one-way ramps may be connected to each other by one or two horizontal connection points and/or subse- quent second one-way ramps may be connected to each other by one or two horizontal connection points, and/or subsequent third one- way ramps may be connected to each other by one or two horizontal connection points, and/or subsequent fourth one-way ramps may be connected to each other by one or two horizontal connection points. A pair of subsequent ramps may be connected by means of the connec- tion point without any further horizontal track between said ramps in this embodiment, subsequent ramps are connected so that a path along subsequent ramps between multiple levels has a short length.

[48] Optionally, any connection point may be arranged on a three- dimensional grid, i.e. each connection point may define a grid point of the three-dimensional grid. This embodiment con improve the layout of the track arrangement and simplify the navigation and/or coordination of one or more carriages. The grid provides well defined coordinates at grid points where connection points can be located. Not any of the grid points needs to comprise a connection point. i.e., the grid con comprise a grid point without a connection point.

[49] Optionally, the grid may comprise 2 track levels, Y track rows, and X track columns, wherein C,U,Z e N, wherein each track row ex- tends horizontally and transverse to the aisle direction, and each track column extends vertically to provide an alignment of the grid and the track arrangement. Thus, a sequence of track rows extends horizontally along the aisle direction, whereas a sequence of track columns ex- tends horizontally transversely to the aisle direction. The track columns may be connected to each other by the ramps. If the length of the ramps is L and the slope angle of the ramps is a. the distance D be- tween the track columns may be D = L · sin a .

[50] Optionally, the number of track levels may equal the number of storage levels, i.e. Z = k, at each storage levei, at least one connection point is potentially arranged. However. In some embodiments, the track arrangement may comprise auxiliary intermediate track levels in addition to the track levels that correspond to the storage levels, i.e. Z > k. The number of track rows is preferably three to five to provide a space-saving embodiment. An embodiment with three track rows may comprise on each level a bidirectional horizontal track in a first track row closest to the storage rack arrangement, one-way ramps with a positive slope angle in a second track row, and one-way ramps with a negative slope angle in a third track row. Alternatively, the second track row may comprise one-way ramps with a negative slope angle, whereas the third track row may comprise one-way ramps with a posi- five slope angle. An embodiment with four track rows may comprise on each level a first unidirectional horizontal track in a first horizontal driv- ing direction transverse to the aisle direction yn the first track row and a second unidirectional horizontal track in a second horizontal driving di- rection opposite the first horizontal driving direction yn the second track row. The third track row may comprise one-way ramps with a posi- tive(negative) slope angle, whereas the fourth track row may comprise one-way ramps with a negative (positive) slope angle. An embodiment with five track rows may be similar to the embodiment with four track rows, but an additional track row may comprise on each level a bidi- rectional horizontal track for adapting the distance between track col- umns of the track arrangement (determined by the ramp length and the ramp slope angle) to the distance between aisles of the storage rock arrangement. Preferably, the number of track columns equals the number of levels in order to reduce the number directional changes of the carriages. If the number of track columns must be chosen to be less than the number of levels, for example due to lateral space limitations, a path along a sequence of ramps may include turns of 180 degrees via two adjacent connection points including a transfer to the adja- cent frock raw, Preferably, the entry point and exit point of an interac- tion site are arranged at adjacent track columns on the some level. A "180-degree turn" on a one-way path shall mean herein that the car- riage changes to the opposite driving directing by two subsequent 90- degree turns at two adjacent connection points to change to another unidirectional or bidirectional track allowing the opposite driving direc- tion. This means that the carriage must change the track row during a 180-degree turn on a one-way path.

[51] Optionally, between each pair of adjacent track columns one or more (up to Y-1 ) one-way ramps with a positive slope angle may be ar- ranged in one track row, and between the same pair of adjacent track columns the same number of ramps with a negative slope angle may be arranged in an adjacent track row. The ramps of the same track row may be preferably arranged essentially in parallel to each other. These embodiments each provide a track arrangement with an im- proved usage of constructive space in the aisle direction. [52] Optionally, at least one of the first one-way ramps, second one- way ramps, third one-way ramps, and/or fourth one-way romps may have a slope angle of 5 to 20 degrees, preferably 12 to 17 degrees. For example, at least one of the ramps may have a slope angle of 15 de- grees. This embodiment provides a slope angle so that each ramp is ef- fectively drivable by a carriage and requires a preferred amount of constructive space in horizontal direction to connect different storage levels. Preferably, the absolute amount of the slope angle of all ramps is essentially the same. Preferably, the sign of the slope angle is essentially the same for aii ramps of the same track row and different between ramps of adjacent track rows. Preferably, the oil ramps have essentially the same length. Thereby, the ramps may ail be identical to each other to reduce the diversity of parts the track arrangement is composed of.

[53] Optionally, the at least one interaction site may comprise a charger module for charging a battery of a carnage during automati- cally processing a stored container and/or automatically issuing a con- tainer to be stored, in this embodiment, a carriage can be charged during handing over a container to and/or from the carriage. The time during a stored container is processed and/or a container to be stored is issued is thereby used effectively. Preferably, this time is sufficient to charge the battery to last until the carriage returns to a charger module next time, so that the carriage does not any extra pauses to charge its battery.

[54] Optionally, the track arrangement may comprise a one-way in- teraction track to connect the entry point of the interaction site with the at least one interaction site and the at least one interaction site with the exit point of the interaction site. This embodiment improves the con- nection of the interaction site with other tracks of the track arrange- ment. The one-way interaction track prevents potential collision of car- riages that drive towards or away from the interaction site. Preferably, the interaction track is a loop which leads from the entry point via the interaction site to the exit point. The loop is preferably closed by the first horizontal one-way track and/or the second horizontal one-way track. Optionally, the one-way interaction track comprises and/or is a horizon- tal track.

[55] Optionally, the track arrangement may be arranged so that it can be scaled and extended as desired by one or more levels and/or track columns of the track arrangement. Thus, the track arrangement may be comprised of a modular construction kit comprising ramps, hor- izontal tracks and connection points. The size and layout of such a track arrangement can be adjusted to the storage rack arrangement by choosing the most appropriate number of track columns and ramps per track column. [56] Optionally, the track arrangement may comprise an optical marker, an electrical tag and/or a lane marking so that a carriage can detect its position and/or check/improve its position information. Preferably, the carnage may comprise a detection device which is adapted to detect a marker, tag and/or marking of any of the one way tracks. For example, the carnage may comprise a camera to de- tect an optical marker and/or lane marking, and/or on RFID reader to read an electrical tag. A marker, tag, and/or malting can be arranged in and/or at a track bed of a track which are configured to guide the carnages along said track.

[57] According to another dependent or independent aspect of the present disclosure, an automated storage and retrieval system is pro- vided comprising the aforementioned track arrangement and at least one self-driven carriage being configured to drive along a defined first path along one-way ramps of the track arrangement for automatically transporting a stored container from a storage site to an interaction site and/or to drive along a defined second path along one-way ramps of the track arrangement for automatically transporting a container from the interaction site to a storage site. The at least one carriage may comprise a battery to power a drive motor of the carriage and prefera- biy to be charged by a charging module which may be located at the interaction site; a detection device which is adopted to delect a marker, tag and/or marking of any of the one-way tracks; and a driving arrangement to interact with the tracks, e.g. the driving arrangement may comprise wheels with a iaterai distance and wheelbase that fits the tracks and romps of the track arrangement.

[58] Optionally, the at least one carriage may comprise a first wheel set of four wheels for driving fourth and bock in the aisle direction and a second wheel set of four further wheels for driving fourth and back transversely to the aisle direction and for driving the ramps up- ward/downward. The driving direction of the first wheel set differs from the driving direction of the second wheel set by 90 degrees. At least one of the first wheel set and the second wheel set may be vertically lowered and lifted relative to the other wheel set, so that the lower wheel set is the active wheel set for driving while the upper wheel set is the idle wheel set. The driving direction may be changed at connec- tion points of the track arrangement by changing the active wheel set, i.e. by lowering the idle wheel set and/or lifting the active wheel set.

[59] Optionally, the track arrangement is arranged at a front face of the storage rack arrangement to provide a space-saving construction of the automated storage and retrievai system. [50] Optionally, the at least one carriage may comprise a sensor ar- rangement and the track arrangement comprises on optical marker, an electrical tag and/or a lane marking, wherein the sensor arrange- ment is configured to identify the optical marker, the electrical tag and/or the lane marking for determining the position of the at least one carriage in the track arrangement.

[61] According to another dependent or independent aspect of the present disclosure, a method for automatically storing and/or retrieving containers in racks of a storage rack arrangement is provided. The method comprising the steps of: driving a self-driven carriage on a first rail track having a first track gauge and extending along a first axis for positioning the carriage at on aisle between the racks, wherein the carriage is driven with a first gear ratio. driving the carriage on a second rail track having a second track gauge and extending along a second axis transverse to the first axis for positioning the carriage along the aisle, wherein the carriage is driven with a second gear ratio, driving the carriage on a first rail track having the first track gauge and extending along the first axis for positioning the carriage within a rack below a container, wherein the carriage is driven with the first gear ratio, lifting a support surface of the carriage for carrying a bottom sur- face of the container, securing and centring the container on the support surface by simultaneously moving at least two engaging elements in opposite di- rections to each other from an idle position into a securing position for engaging, in the securing position, with corresponding receiving ele- ments at the bottom surface of the container, driving the carnage carrying the container on the first rail track for leaving the rack towards an aisle, wherein the carriage is driven with the first gear ratio. lowering the support surface, and driving the carriage on a second rail track having a second track gauge and extending along the second axis for leaving the aisle to- wards an interaction site for processing the container, wherein the car- riage is driven with the second gear ratio.

[62] The above steps may preferably be steps for retrieving a con- tainer from the storage rack arrangement. The steps above may be typically performed after the carriage has stored another container in the storage rack arrangement is now available for a new task. For in- stance, the carriage may be already on the desired storage level of the new task and may, in the first step, drive on a horizontal track being a first rail track to find the desired aisle. As a second step, the carriage may enter the aisle along an aisle track being a second rail track with a narrower track gauge than the horizontal track being a first rail track. In the second step, the carriage may drive with a lower gear ratio for driv- ing faster at a certain motor speed compared to driving on a first rail track with a higher gear ratio at the same motor speed. This is particu- larly advantageous to reduce the time for storing and/or retrieving the container if the storage rack arrangement is longer along the second axis than along than along the first axis. [63] in the second step, the carriage may find the desired position along the aisle for entering the rack. In the third step, the carriage may enter the rack to find the desired posiiion beiow a desired container. The containers may be placed on rack fillets extending along the first axis and having a vertical distance to the first rail tracks within the stor- age rack arrangement. The vertical distance is preferably larger than the height of the carriage so that the carriages can enter the storage rock arrangement below the rack fillets. There may be one or more than one container placed above the same first rail track within the storage rack arrangement. An embodiment with only one container per first rail track may be advantageous for a quick retrieving and stor- ing time, because there is no need for rearranging other containers be- fore retrieving or storing the desired container. A first rail track may con- nect to the adjacent first rail track of the neighbouring track accessible from the neighbouring aisle, so that a carriage may enter a first rail track from one aisle and leave it via the connected first rail track at the other aisle, or vice versa. In case of more than one container stored over one first raii track, it may be necessary to rearrange containers to other free, preferably close-by, storage sites before the desired con- tainer or storage site can be accessed. An embodiment of more than one container per first rail track may be thus slower in terms of retrieving and storing time, but advantageous in terms of lateral warehouse den- sity, because fewer aisles are needed. Preferably, the position along a first rail track within the storage rack arrangement may depend on the expected time for next access of the container. For iess frequently ac- cessed containers, a "deeper” position within the rack may be pre- ferred, whereas more frequently accessed containers may be placed closer to an aisle. [64] Once the path between the desired container and an aisle is free and the carriage is placed below the desired container, the sup- port surface of the carriage may be lifted for carrying a bottom surface of the container in the fourth step. The container may thus be lifted off the rack fillets on which it stood. The support surface therefore prefera- bly fits between the rack fiiiets. In a fifth step, the container may be se- cured and centred on the support surface by simultaneously moving at least two engaging elements in opposite directions to each other from an idle position into a securing position for engaging, in the securing position, with corresponding receiving elements at the bottom surface of the container. There is thus no need for the carriages to have secur- ing side walls, which would be detrimental to the desired compact de- sign of the carriages.

[65] In a sixth step, the carriage carrying the container from below may either drive to the same aisle it came from or via a connected first rail track to the neighbouring aisle, depending on which path is free and/or shortest to the destination, i.e. the desired interaction site.

[66] Once the carriage has left the rack and is positioned on an aisle track being a second rail track, the carriage may lower the support sur- face again to tower the centre-of-gravity of the carriage carrying the container in a seventh step. This reduces the risk of the carriage falling over at ramps or bumps or during quickly breaking and accelerating.

[67] In the last eighth step, the carriages may drive quickly with the second gear ratio along the aisle track back towards the horizontal track at the front face of the storage rock arrangement. The horizontal track may be part of a track arrangement at the front face of the stor- age rack arrangement for accessing other track leveis and finally enter- ing the interaction site via first or second one-way ramps as described above.

[68] Optionally, preferably for storing a container in the storage rack arrangement, the method may further comprise: driving the carriage carrying the container on a first rail track having the first track gauge and extending along the first axis for posi- tioning the carriage at an aisle between the racks, wherein the car- riage is driven with the first gear ratio, driving the carriage carrying the container on a second rail track having the second track gauge and extending along the second axis transverse to the first axis, tor positioning the carriage along the aisle, wherein the carriage is driven with the second gear ratio, lifting the support surface of the carriage together with the con- tainer. driving the carriage carrying the container on the first rail track for positioning the carriage within a rack at an empty storage site, wherein the carriage is driven with the first gear ratio, unsecuring the container by simultaneously moving the at least two engaging elements in opposite directions to each other from the securing position into the idle position for disengaging, in the idle posi- tion. the receiving elements at the bottom surface of the container, lowering the support surface for placing the container at the storage site, and driving the carriage on the first rail track for leaving the rack to- wards an aisle, wherein the carriage is driven with the first gear ratio.

[69] The steps above may be performed independently of the steps for retrieving a container, but preferably performed in combination for retrieving and storing containers. The steps above may be typically per- formed after the container has been issued at the interaction site and left the interaction site via third or fourth one-way ramps to reach the desired storage level.

[70] For instance, the carriage may be already on the desired stor- age level and may. in the first step, drive on a horizontal track being a first rail track to find the desired aisle. As a second step, the carriage may enter the aisle along an aisle track being a second rail track with a narrower track gauge than the horizontal track being a first rail track. in the second step, the carriage may drive with a lower gear ratio for driv- ing faster at a certain motor speed compared to driving on a first roil track with a higher gear ratio at the same motor speed. This is particu- iarly advantageous to reduce the time for storing and/or retrieving the container if the storage rack arrangement is longer along the second axis than along than along the first axis.

[71] Once the carnage has found the desired rack, the carriage may lift the support surface to lift the container above the rack fillets in order to be able to enter the rack in a third step. The carnage may drive on the first rail track below rack fillets while it is carrying the container above the rack fillets. Driving with a lifted support surface only when necessary reduces the risk of the carriage falling over at ramps or bumps or during quickly breaking and accelerating.

[72] In the fourth step, the carnage may enter the rack to find the de- sired storage site along the first rail track for storing the container. The containers may be placed on rack fillets extending along the first axis and having a vertical distance to the first rail tracks within the storage rack arrangement. The vertical distance is preferably larger than the height of the carriage so that the carriage can enter the storage rack arrangement below the rack fillets and carry the container above the rack fillets. There may be one or more container already stored in the way between the aisle and the desired storage site. In such a case, the carriage must park the container it is actually carrying at another close- by free storage site for rearranging the other containers until the path to the storage site is free. An embodiment with only one container per first rail track may be advantageous for a quick retrieving and storing time, because there is no need for rearranging other containers before re- trieving or storing the desired container. A first rail track may connect to the adjacent first rail track of the neighbouring track accessible from the neighbouring aisle, so that a carriage may access a storage site from two neighbouring aisles. An embodimenl of more than one con- tainer per first rail track may be slower in terms of retrieving and storing time, but advantageous in terms of lateral warehouse density, because fewer aisles are needed. Preferably, the position of a storage site along a first rail track within the storage rack arrangement may depend on the expected time for next access of the container at issue. For less fre- quently accessed containers, a “deeper” position within the rack may be preferred, whereas more frequently accessed containers may be placed closer to on aisle.

[73] Once the path between the desired container and an aisle is free and the carriage carrying the container at issue below the desired free storage site, the support surface of the carriage may be lowered for placing a bottom surface of the container on the rack fillets in the fourth step. The support surface therefore preferably fits between the rack fillets. In a fifth step, the container may be unsecured by simultane- ously moving the at least two engaging elements in opposite directions to each other from the securing position into the idle position for disen- gaging, in the idle position, the receiving elements at the bottom sur- face of the container. There is thus no need for the carriages to have securing side wails, which would be detrimental to the desired com- pact design of the carriages. Securing side wails of the carriages would also reduce the warehouse density along the first axis and/or the sec- ond axis, because the containers would need to be stored with a larger horizontal distance to each other along the first axis and/or the second axis.

[74] in a sixth step, the carriage without the container may either drive to the some aisle it came from or via a connected first rail track to the neighbouring aisle, depending on which path is free and/or shortest to the destination, i.e. the desired container of the next task. [75] Once the carriage has left the rack and is positioned on an aisie track being a second rail track, the carriage may lower the support sur- face again to lower the centre-of-gravity of the carriage carrying the container in a last seventh step. This reduces the risk of the carriage fall- ing over at ramps or bumps or during quickly breaking and accelerot- ing.

[76] In an optional eighth step, the carriages may drive quickly with the second gear ratio along the aisle track back towards the horizontal track at the front face of the storage rack arrangement for the next task. The horizontal track may be part of a track arrangement at the front face of the storage rack arrangement for accessing other track levels and finally accessing the storage level of the next task. [77] Optionally, the first gear ratio is at ieast two times, preferably at least three times, larger than the second gear ratio. This is particularly useful for driving efficiently on ramps for changing between track levels and driving quickly along the aisie tracks. [78] Optionally, the first track gauge is significantly larger than the second track gauge. This is particularly advantageous, because the carriages may have a first wheel set for driving along the first axis, wherein the first wheel set may have a relatively short first wheel base for driving along the ramps. For driving safely and more quickly, the car- riages may have a second wheel set for driving along the second axis, wherein the second wheel set may have a relatively long second wheel base for driving along the aisle frocks. As the wheels of the wheel sets ore preferably positioned at the most lateral positions as possible for the sake of driving stability, the first track gauge is preferably signifi- cantly larger than the second track gauge.

[79] Optionally, driving the carriage with or without the container on a first rail track comprises driving on a ramp for changing between storage levels of the storage rack arrangement. Preferably, these ramps are the first, second, third and fourth one-way ramps of a track ar- rangement at the front face of the storage rack arrangement. So, the first rail tracks ore preferably not only used within the storage rack ar- rangement for accessing and storing containers in a rack, but also on the ramps and on the horizontal tracks along the first axis.

SUMMARY OF THE DRAWINGS [80] Embodiments of the present disclosure will now be described by way of example with reference to the following figures of which;

Figs. 1a,b show two examples of an automated storage system ac- cording to an embodiment of the present disclosure;

Fig. 2 shows a perspective view of an embodiment of a car- riage carrying a container according to the present dis- closure; Fig, 3 shows a side view along the second axis of the carriage carrying a container shown in Fig. 2;

Figs. 4a,b shows perspective views on the carriage shown in Figs. 2 and 3 with a lowered support surface (Fig. 4a) and a lifted support surface (Fig. 4b), respectively;

Fig. 5 shows a perspective view on the carriage shown in Figs. 2- 4 with a casing shown transparently; Fig. 6 shows a top view on the carriage shown in Figs. 2-5 with a casing and support surface shown transparently; Fig. 7 shows a side view olong the second axis of the carriage shown in Figs, 2-6 with a casing transparently;

Fig. 8 shows a side view along the first axis of the carriage shown in Figs. 2-7 with a casing transparently;

Figs. 9a, b shows perspective views on the support surface and the securing and centring system of a carriage shown in Figs.

2-8;

Figs. 10a,b show a perspective view and a front view, respectively, of another embodiment of a carriage according to an em- bodiment of the present disclosure on a ramp; and

Fig. 11 shows a schematic diagram of a control system of a car- riage shown in Figs. 2-9.

[81] Figure 1 shows an automated storage system 25 according to an embodiment of the present disclosure. The automated storage system 25 comprises a track arrangement 1 arranged in and/or at a rack ar- rangement 3, in particular at a front face 32 of the rack arrangement 3, and a plurality of self-driven carriages 2. The track arrangement 1 is con- figured so that a plurality of self-driven carriages 2 can drive along the track arrangement 1 , e.g. by comprising tracks having a track width that allows an efficient and stable driving of the carriages 2. The storage rack arrangement 3 is here relatively wide along a first axis x with nine rocks 9 and eight aisles 9 between the racks 6. The storage rack arrangement 3 is also quite along a second axis y with 15 storage sites 6 arranged along the aisles 9. The storage rack arrangement 3 is thus arranged on a grid with 15 storage rows along the second axis y. As six of the racks 9 com- prises two storage sites 6 along the first axis x and three of the racks 9 comprises four storage sites 6 along the first axis x, there are in total 24 storage rows along the first axis x and five storage levels along the verti- cal axis z, i.e. k - 5. The total number of storage sites 6 is thus 1 ,800. [82] The storage rack arrangement 3 for automatically storing and ac- cessing containers 4 comprises a plurality of storage sites 5 being ar- ranged in a plurality of rocks 6 extending over a plurality of k storage levels. The storage sites 5 ore accessible by horizontal aisle tracks 8 on each storage level, wherein the aisle tracks 8 extend in on aisle direction y along aisles 9 between the racks 6. The racks 6, the aisles 9, and the aisle tracks 8 extend parallel to each other so that the aisle directions y of any pair of adjacent aisles 9 are parallel to each other. Preferably, the storage sites 5 are arranged on a three-dimensional grid. All figures com- prise a right-handed Cartesian coordinate system with a vertical z-axis, a forward y-axis, and a lateral x-axis. Therefore, the aisle direction y is di- rected along the y-axis. The positive y-axis shall mean herein a “forward” longitudinal direction, whereas the negative y-axis shall mean a “back- ward” longitudinal direction. Analogously, the positive x-axis shall mean a lateral direction “to the left”, whereas the negative x-axis shall mean a lateral direction “to the right”. Analogously, the positive z-axis shall mean an “upward” vertical direction, whereas the negative z-axis shall mean a “downward” vertical direction. [83] The track arrangement 1 connects each storage site 5 with an in- teraction site 10 for automatically processing stored containers 4 and/or automatically issuing containers 4 to be stored. The track arrangement comprises in this embodiment as many track levels as storage levels, i.e. Y = k, wherein the track levels correspond to the storage levels. The interaction site 10 is arranged dt a track level that may be denoted as “interaction site level”. In an alternative embodiment, the track arrange- ment I can comprise a plurality of interaction sites 10 and/or can con- nect each storage site 5 with a plurality of interaction sites 10. This can improve the throughput of the automated storage system 25 and pro- vide shorter paths between an interaction site 10 and any of the storage sites 5.

[84] As shown in Figure 1 , the track arrangement 1 comprises first one- way romps 14, second one-way romps 16, third one-way romps 20, and fourth one-way romps 22 so that any pair of adjacent storage levels is connected with each other. Advantageously, the first, second, third, and fourth one-way ramps 14, 16, 20, 22 connect all Y track levels of the rack arrangement 3. Thereby, a carriage 2 can reach any storage level from an adjacent storage level 7.

[85] The track arrangement 1 comprises a horizontal bi-directional track 11 connectable to ail aisle tracks 8 on each storage level along a first axis x. Alternatively, instead of one horizontal bi-directional track 11 there may be two parallel horizontal one-way tracks with mutually oppo- site driving directions along the first axis x. The aisle tracks 8 are bidirec- tional tracks extending along a second axis y extending transverse to the first axis x. In an alternative embodiment, instead of one bi-directional aisle track 8, the track a rangement 1 may comprise two parallel one- way aisle tracks 8 with mutually opposite driving directions along the sec- ond axis y.

[86] The track arrangement 1 comprises a plurality of connection tracks 31 providing connections between the aisle tracks 8 and the first horizontal one-way track 11 and/or the second horizontal one-way track 12. The connection track 31 serves as a track junction at one or more connection points 24 and is configured to being traversed by a carriage 2, wherein the carriage 2 can keep and/or change its driving direction, preferably by 90 degrees. 180 degrees and/or 270 degrees at any of the connection points 24. The connection tracks 31 are in this embodiment unidirectional, but one or more of the connection tracks 31 may be bidirectional in other embodiments. The connection hacks 31 may be composed of a plurality of connection points 24.

[87] The connection tracks 31 each comprise a plurality of connection points 24 to connect the horizontal tracks 11, 12 and/or the one-way ramps 14, 16, 20, 22 with each other. One of the connection tracks 31 extends along the second axis y from the horizontal t rack 11 and the exit point 28 to the entry point 27. Thereby, the connection track 31 connects the first horizontal track 11, the exit point 28, and the entry point 27, so that a carriage 2 can move from one of said tracks 11 and/or one-way ramps 14, 16, 20, 22 to another.

[88] Ail first one-way ramps 14 and second one-way ramps 16 lead to- ward an entry point level 17 (not indicated in Figure i a) of the at least one interaction site 10. All third one-way ramps 20 and fourth one-way ramps 22 lead away from an exit point level 18 (not indicated in Figure 1a) of the at least one interaction site 10. The interaction site 10 can be accessed from the entry point level 17 and left from the exit point level 18. The entry point level 17 is the track level at which the interaction site 10 con be reached by a carriage 2. in this embodiment, a carriage 2 can reach the interaction site 10 from the entry point level 17 without changing the track level on which it drives, i.e. the entry point level 17 is the interaction site level. The entry point level 17 and the exit point level 18 are here identical for the interaction site 10, i.e. the entry point 27 and the exit point 28 are arranged at the same track level, namely at the track level at which the interaction site 10 is arranged, i.e. the interaction site level.

[89] In this embodiment, the exit point level 18 is the track level from where the track level, at which the interaction site 10 is arranged, can be left via a third one-way ramp 22 and a fourth one-way ramp 22. The first one-way ramp 14 and the second one-way ramp 16 that leads to the entry point levei 17 connects an adjacent track level with the entry point level 17 at on entry point 27 of the interaction site 10 from which the interaction site 10 can be reached by a carriage 2. The entry point 27 is arranged at the entry point level 17. The exit point level 18 is con- nected at on exit point 28 of the interaction site 10 via a third one-way ramp 20 and a fourth one-way ramp 22 to an adjacent track level 7, wherein the exit point 28 is arranged in the exii point level 18.

[90] As also shown in Figure 1 a, the first one-way ramps 14 comprise a first sequence of first ramps 13, the second one-way ramps 16 comprise a second sequence of second ramps 15, the third one-way ramps 20 comprise a third sequence of third ramps 19 and/or the fourth one-way ramps 22 comprise a fourth sequence of fourth ramps 21. Subsequent one-way ramps 14. 16, 20, 22 of the first, second, third or fourth sequence of ramps 13, 15, 19, 21, respectively, are connected to each other by one or two horizontal connection points 24. In this embodiment, the third or fourth sequence of ramps 19, 21 is arranged so that a carriage 2 can traverse any of said sequence of romps 19, 21 without turns of 180 de- grees between ramps. The some applies for the second sequence up- ward to the entry point 27. However, the first sequence downward to- ward the entry point includes a turn of 180 degrees at the fourth track level. This is. because the available lateral space does not allow for a wider track arrangement, i.e. for another track column at the right end.

[91] The self-driven carriages 2 ore configured to drive a defined first path along horizontal track 1 1and first and second one-way romps 14, 16 of the track arrangement 1 for automatically transporting a stored container 4 from a storage site 5 to an interaction site 10. The self-driven carriages 2 are configured to drive a defined second path along the one-way tracks 11 and third and fourth one-way ramps 20, 22 of the track arrangement 1 for automatically transporting a container 4 from the in- teraction site 10 t o a storage site 5. Therein, the first path and the second path can comprise common tracks 11 but no common ramps. Prefera- bly, the automated storage system 25 comprises a one or a plurality of carriages 2. [92] At any storage level 7, the horizontal track 11 enables a carriage

2 to move, on the same storage level 7, from any aisle track 8 to another aisle frock 8, The bidirectional horizontal track 11 extends transversely to the aisle direction y. The bidirectional horizontal track 11 is arranged, in the aisle direction y, between the aisle tracks 8 and the first, second, third. and/or fourth one-way ramps 14, 16, 20, 22. In the aisle direction y, the track arrangement 1 extends with a depth in y-direction of three track widths, i.e. the width of three connection points 24.

[93] The bidirectional horizontal track 11 is bidirectional to provide short paths between the interaction site 10 and any of the storage sites 5. In an alternative embodiment, the track arrangement 1 comprises first and second horizontal one-way tracks instead of one bidirectional horizontal track 11 to prevent any potential collision of carnages 2 when moving along the said track and/or to provide a unique first path and/or second path.

[94] The track arrangement 1 comprises a plurality of first sequences 13 of first one way ramps 14, a plurality of second sequences 15 of sec- ond one-way ramps 16, a plurality of third sequences 19 of third one-way ramps 20, and a plurality of fourth sequences 21 of fourth one-way ramps 22. Thereby, the track arrangement 1 comprises a plurality of first paths from any of the storage sites 5 to the interaction site 10, and a plurality of second paths from the interaction site 10 to any of the storage sites 5. This can increase the possible throughput of the automated storage and re- trieval system 25. [95] In Fig. 1 a, the interaction level is the third level with the entry point 27 and an exit point 28 on the third level. The track arrangement 1 com- prises a plurality of first, second, third, and fourth sequences of one-way ramps 13, 15, 19, 21. wherein each sequence comprises two one-way ramps 14, 16, 20, 22 to reach ail five levels of the track arrangement. The second sequence 15 comprises two second one-way ramps 16 directed upward to the right and arranged in the same track row below and left of the entry point 27. The third sequence 19 comprises two third one-way ramps 20 directed upward to the right and arranged in the same track row track row above and right of the exit point 28. The fourth sequence 21 comprises two fourth one-way ramps 22 directed downward to the left and arranged in the same track row below and right of the exit point 28. The first sequence 13 differs from the other sequences 15, 19, 21 in that there is not sufficient latera! space to right from the ehtry point for the carriage to descend from the fifth top level. Therefore, one first one- way ramp 14 of the first sequence 1 between the fourth and third level is directed downward to the ieft and arranged above ond right of the en- try point 27 in the some track row of the entry point 27. The other first one- way ramp 14 of the first sequence 13 between the fifth and fourth level is directed downward to the right and arranged in a different track row than the entry point 27. Therefore, the path of a carnage along the first sequence 13 implies a 180-degree turn between the two first one-way ramps 14. The available lateral space and the position of the entry point 27 and/or exit point 28 in the track arrangement 1 determine if and how many such 180-degree turns may be needed in which sequence. The layout of the track arrangement 1 may be chosen to minimise the num- ber of 180-degree turns as much as possible. However, if need be, the first, second, third, and/or fourth sequences 13, 15. 19, 21 may comprise a plurality of 180-degree turns and may thus define a zig-zag-shaped path. [96] in the embodiments of Figs. 1 a,b, the track arrangement 28 is ar- ranged on a three-dimensional grid, wherein the connection points 24, entry point 27 and/or exit point 28 define grid points. The grid comprises Z track levels, Y track rows, and X track columns. The track rows extend transverse to the aisle direction y (along x-axis), so that a sequence of track rows extends in the aisle direction (along y-axis). The track columns are defined by a sequence of connection points 24 vertically arranged above each other (along z-axis), so that a sequence of track columns extends transverse to the aisle direction (along x-axis). The one-way ramps 14, 16, 20, 22 connect adjacent track columns and levels which each other. The number Z of track levels equals here the number k of storage levels 7, i.e. k = 5 in Fig. 1a. The number of track rows Y equals the maximum number of connection points 24 of a connection track 31 in aisle direction y, i.e. Y - 3 in Fig. 1a. Additionally, some space in aisle direction y, may be provided for arranging the interaction track 26 and the interaction site 10. In Fig. 1a the number X of track columns equals the number Z of track levels. This is particularly advantageous to reduce the number of needed 180-degree turns. However, the carriages 2 may only be able to securely climb/descend ramps with a siope angle of less than a _ma , so that a minimum track column distance D _min may be needed to climb one level height H, wherein If the available iat- eral space does not allow a layout of the track arrangement with at least Z track columns, the number X of track columns can be reduced down to a minimum number X of 2 at the cost of more 180-degree turns. Pref- erably, the driving direction of ramps of the same track row connecting the same track columns alternates between adjacent levels. Preferably, the driving direction of ramps between the same levels and connecting the same track columns differs between the track rows. Preferably, the driving direction of ramps connecting the same levels in the same track row alternates between adjacent track columns. [97] The number Y of trock rows is counted from the front face 32 of the rack arrangement 3 forward in x-direction, so that the bidirectional horizontal track 11 in Fig. 1a is arranged in track row number one. The number Z of track levels equals the number k of the storage levels 7, wherein the bottom storage level has level number one and the top level has level number five in Fig. 1 a. In Fig. 1 a, the number of track columns X is five, wherein the first track column on the fight is track column number one, the entry point 27 is in track column number two, and the exit point 28 is in the central third track column. Preferably, the entry point 27 and the exit point 28 are arranged in adjacent track columns. Preferably, the entry point 27 and the exit point 28 are arranged on the same track level.

[98] In all shown embodiments, the ramps of the same track row are arranged essentially in parallel to each other, i.e. each extending from bottom left to top right or vice versa, or each leading from top left to bottom right or vice versa, in Fig. 1a, all ramps of the second track row lead from top left to bottom right between adjacent levels and track columns. Analogously, all ramps of the third track row lead from bottom left to top right between adjacent levels and track columns. In Fig, 1a, only 8 one-way ramps 14, 16, 20. 22 in total would at least be required to connect the entry point 27 and the exit point 28 with any track level. Seven of those one-way ramps 14, 16, 20, 22 are arranged in the third track row and one first one-way ramp 14 between the fifth and the fourth track level and the first and second track column. If there was enough lateral space for another track column right to the first track column, all 8 one-way ramps 14, 16, 20, 22 could have been arranged in the same track row, so that the second track row would not be necessary alto- gether. Fig. 1 a shows 32 ramps in total, of which 16 ramps are arranged in the second track row and 16 ramps are arranged in the third track row. Therefore, the embodiment of Fig. 1 a comprises a redundancy of 24 ad- ditional ramps that provide alternative options for paths to the entry point 27 or from the exit point 28. This may reduce the risk of congestions ond allow for more traffic, i.e. for more carriages 2 to be operated simultane- ously. Moreover, the track arrangement 1 of Fig. 1a could allow for up to three more interaction sites 10 to be served in parallel. For instance, an- other interaction site could be arranged on the third track level between the fourth and fifth track column, and/or on the first and/or fifth track level between the second and third track column and/or between the fourth and fifth track column.

[99] Figure 1 b shows a perspective view of another embodiment of an automated storage system 25 according to the present disclosure. The storage rack arrangement 3 is here relatively narrow along the first axis x with only two racks 6 and one aisle 9 between the racks 6. The storage rack arrangement 3 is relatively long along the second axis y with 20 stor- age sites 6 arranged along the aisle 9. Analogous to the track arrange- ment 1 , the storage rack arrangement 3 is arranged on a grid with 20 storage rows along the second axis y, eight storage rows along the first axis x and five storage levels along the vertical axis z, i.e. k = 5. The total number of storage sites 6 is thus 800. [100] The track arrangement 1 as shown in Figure 1b has nine track lev- els, three track columns and two track rows to serve one interaction site 10 at the second track level via interaction track 26. The track arrange- ment 1 is particularly useful for narrow storage rack arrangements 3 with limited lateral space. The storage rack arrangement 3 has only 5 storage levels, but the track arrangement 1 comprises four additional auxiliary intermediate track levels between the track levels 1 -2, 3-4, 5-6 and 7-8. The frock arrangement 1 thus comprises 16 relatively short one-way ramps 14, 16, 20, 22 that each climb only half a storage level to keep the slope angle below the maximum slope angle α _ma , i.e. the track levei dis- tance of the track arrangement 1 is here haif the storage level height. Five first ramps 14 connect track levels 8-3 downward, three second ramps 16 connect track levels 1-3 upward, five third ramps 20 connect track levels 3-8 upward, and three fourth ramps 22 connect track levels 3- 1 downward. The path aiong a sequence of ramps 14, 16, 20, 22 may include a zig-zag sequence with one or more 180-degree turns at the lateral ends, i.e. at the first and third column, A central connection track 31 at the second track column leads into central aisle tracks 8. The first and third track column are auxiliary track columns with connection points 24 at the auxiliary intermediate track levels, where the carriages 2 can make a 180-degree turn to climb or descend a track level upward or downward. In this embodiment, horizontal tracks 11, 12 with a driving direction transverse to the aisle direction y can be dispensed with, be- cause the storage rack arrangement has only one aisle 9. At any storage level 7, the aisle tracks 8 are connected by the one-way ramps 14, 16, 20, 22 to the interaction track 26. in the aisle direction y, the track ar- rangement 1 extends by the width of two connection points 24 away from the front face 32 of the rack arrangement 3.

[101] Any of the described track arrangements 1 is arranged so that the track arrangement 1 can be extended arbitrarily by reproducing the shown track arrangement 1 and/or a section thereof aiong the first axis X, periodically. This makes the track arrangement 1 modular and adapt- able to the size of the storage rack arrangement 3.

[102] Fig. 2 shows a carriage 2 carrying a container 4 on a connection point 24 in more detail. The carriage 2 has essentially a box shape with a certain width W along the first axis x, a certain length L along the second axis y and a certain height H along the vertical axis z. The container 4 has only slightly smaller dimensions along the first axis x and the second arris y, but is significantly higher along the z-axis. The container 4 is placed on top of the carriage 2 which thereby carries the container 4. The container is secured and centred on a top support surface 39 of the carriage 2 by means of a securing and centring system comprising engaging elements 41 described in more detail with reference to Figs. 9a, 9b. The top sup- port surface 39 of the carriage 2 is vertically movable to lift and lower the container 4. Fig. 2 shows the support surface 39 in a lifted position. [103] The carnage 2 is able to drive “laterally"' on first rail tracks 36 ex- tending along the first axis x by using a first wheel set 37 of four wheels and “longitudinally” on second rail tracks 42 extending along the second axis y by using a second wheel set 43 of four wheels. Thus, the carriage 2 comprises eight wheeis in total. The wheels of the first wheel set 37 ore arranged at a front side 47 and a back side 49 (not visible in Fig. 2) of the carriage 2. The wheels of the second wheel set 43 ore arranged at a left side 51 (not visible in Fig. 2) and a right side 53 of the carriage 2. The carriage 2 is significantly longer along the second oxis y than wide along the first oxis x. Similarly, the wheel base of the first wheel set 37 is signifi- cantly shorter than the wheel base of the second wheel set 43. Accord- ingly, a first track gauge 55 of the first rail tracks 36 is significantly larger than a second track gauge 57of the second rail tracks 38. The first rail tracks 36 may be part of the ramps 14, 16, 20, 22, the horizontal tracks 11 and installed within the racks 8 along the x-axis for the carriages 2 to en- ter the racks 8. The second rail tracks 38 may be part of the aisle tracks 8. The connection points 24 may comprise both first rail tracks 36 and second rail tracks 38 crossing each other.

[104] In the shown embodiment, the first wheel set 37 is mounted on a first chassis 59 of the carriage 2, whereas the second wheel set 43 is ver- tically movable between a driving position and an idle position relative to the first chassis 59 of the carriage 2. Thus, the second wheel set 43 is vertically movable relative to the first wheel set 37. The lower one of the first wheel set 37 and the second wheel set 43 is in the driving position and the upper one of the first wheel set 37 and the second wheel set 43 is in the idle position. In fact, the first wheel set 37 is lifted together with the first chassis 59 when the second wheel set 43 is in the driving position and moved downward. In an alternative embodiment, only the first wheel set 37 or both wheel sets 37, 43 may be vertically movable relative to the first chassis 59 of the carriage 2. The second wheel set 43 is preferably mounted to a second chassis 60, wherein the first chassis 59 and the second chassis 60 are movable relative to each other (see Fig.

5). [105] The carriage 2 further comprises guiding elements 61 in form of a plurality of pulleys that ore rotatable about a vertical axis z and arranged at the front side 47, the back side 49, the left side 51 and the right side 53 of the carriage 2. At least a subset of the pulleys may be arranged at the four vertical edges of the carriage 2 to serve as a guiding element 61 for both driving along the first axis x and driving along the second axis y. The guiding elements 61 partly protrude outwardly relative to the respective front side 47, back side 49, left side 51 or right side 53 they are arranged at, so that the pulleys can roll along vertical guiding Surfaces provided by the first rail tracks 36 and second rail tracks 38, respectively. Thereby. the carnage 2 is able to smoothly and efficiently drive along the first rail tracks 36 and the second rail tracks 38, respectively. The pulleys may be spring-loaded outwardly to centre the carriage 2 on the first rail tracks 36 and the second rail tracks 38, respectively. [106] The first wheel set 37 has a relatively short first wheel base 63. This is advantageous for entering and leaving, with a sufficient ground clear- ance, the ramps 14, 16, 20, 22 that extend laterally along the first axis x. The second wheel set 43 has a relatively long second wheel base 65. This is advantageous for driving quickly on the aisle tracks 8 that extend Ion- gitudinally along the second axis y between the racks 6.

[107] Fig. 3 shows a view on the back side 49 of the carriage 2 carrying the container 4 on the lifted support surface 39. The carriage 2 has a height H when the support surface 39 is lowered. The support surface 39 is essentially vertically movable by a range d above the height H. The container has height h, wherein h > H. Therefore, the maximal height of the carriage 2 carrying the container 4 is H + d + h, when the support surface 39 is lifted. Therefore, the minimal height of the carriage 2 carrying the container 4 is H + h, when the support surface 39 is lowered. The vertical position of the support surface 39 defines the total height H + d of the carriage 2 by comprising at least three contact points for sup- porting the container 4 from below. In Fig.3. the first wheel set 37 is lower than the second wheel set 43. i.e. the first wheel set 37 is in the driving position for driving laterally along the first axis x.

[108] Figs. 2 and 3 also show how the securing and centring system of the carriage 2 works. The securing and centring system comprises in this embodiment two pairs of corresponding engaging elements 41. They are arranged at the support surface 39 in such a way that they are able to engage with receiving elements 41 at the bottom of the container 4. The engaging elements 41 of each pair are rotatable about the second axis y in mutually opposite directions, i.e. clockwise and counter-clockwise, respectively, (see dashed arrows in Fig.3) so that they outwardly engage with the receiving elements 67. Engaging of the engaging elements 41 with the receiving elements 67 may include hooking the engaging ele- ments 67 into the receiving elements 67. On the path between the idle position (see Figs. 4a, b) and the securing position (as shown in Fig. 3), in case the container 4 is not exactly centred with respect to a symmetry plane yz of the carriage 2, one engaging element 41 of a pair may con- tact the container 4 before the other engaging element 41 of a pair. Further motion of the engaging elements 41 will push the container to- wards a laterally central position on the support surface 39. The container 4 is thereby both centred with respect to the symmetry plane yz of the carriage 2 and secured downwardly to the support surface 39.

[109] The carriage 2 also comprises a sensor arrangement 69 arranged at the back-left edge of the carnage 2 and directed horizontally at an angle, e.g. 45 degrees, between the positive first axis x and the negative axis y. The track arrangement 1 may comprise optical markers, electrical tags and/or lane markings that the sensor arrangement 69 is configured to identify for determining the position of the carriage 2 in the track arrangement 1. The position of the sensor arrangement 69 at an edge of the carriage 2 and its angled directed orientation are advantageous to use a single sensor arrangement 69 for both determining the position along the first axis x and the position along the second axis y.

[110] In Fig. 4a, the second wheel set 43 is lower than the first wheel set 37, i.e. the second wheel set 43 is in the driving position for driving longi- tudinally along the second axis y. The first wheel set 37 is in the idle posi- tion, but the wheels of the first wheel set 37 may be driven simultaneously to the wheels of the second wheel set 43. The support surface 39 is low- ered and the engaging elements 41 ore in the idle position. As can be better seen in Fig. 7, the engaging elements 41 are, in the idle position, fully positioned below the support surface 39, whereas they at least partly protrude above the support surface 39 when they are in the securing position (see Fig. 3).

[111] In Fig. 4b, the first wheel set 37 is lower than the second wheel set 43, i.e. the first wheel set 43 is in the driving position for driving longitudi- nally along t he first axis x. The second wheel set 43 is in the idle position, but the wheels of the second wheel set 43 may be driven simultaneously to the wheels of the first wheel set 37. The support surface 39 is lifted and the engaging elements 41 are in the idle position. It should be noted that the support surface 39 has a distance S to the longitudinal ends of the carriage 2 along the second axis y, i.e. to the front side 47 and to the back side 49. As shown in Fig. 2, the container 4 is longer along the sec- ond axis y that the support surface 39, so that a forward end portion of the bottom of the container 2 and a backward end portion of the bot- tom of the container 2 is not supported by the support surface 39. When the container 4 is stored at a storage site 5 of a rack 6, the container 4 preferably rests, with the forward end portion of the bottom of the con- tainer 2 and the backward end portion of the bottom of the container 2, on a pair of corresponding rack fillets extending along the first axis x. The corresponding rock fillets hove a distance to each other that is greater than the length of the support surface 39. Thereby, the support surface 39 is able to pass between the rock fillets when it is lifted from a lowered position to a lifted position by the range d in order to lift the con- tainer 4 off the rack fillets for transport.

[ 112] Some of the inferior parts of the carriage 2 are visible in Fig. 5. The carriage 2 comprises a drive motor 71 for driving both the first wheel set 37 and the second wheel set 43. Both, the first wheel set 37 and the second wheel set 43 may be coupled to the drive motor 71 irrespective whether they are in the idle or driving position. This means that both wheel sets of the carriage 2 may be driven simultaneously, wherein the power consumption of driving the idle wheel set is marginal. However, the first wheel set 37 and the second wheel set 43 are preferably cou- pled to the drive motor 43 via a gear system providing different trans- mission ratios or gear ratios for the two wheel sets 37, 43. The carriage 2 thus comprises a gear system 73 (see Fig. 6), wherein the gear system 73 is operable with a first gear ratio and a second gear ratio. The gear sys- tem 73 is configured for driving the first wheel set 37 with the first gear ratio and for driving the second wheel set 43 with the second gear ra- tio, wherein the first gear ratio is significantly larger than the second gear ratio. This means that the wheels of the second wheel set 43 run significantly faster than the wheels of the first wheel set 37 at a given speed of the drive motor 71. This is particularly advantageous for quickly driving along the long aisle tracks 8 along the second axis y by driving with the second wheel set 37. Accordingly, the output torque of the wheels of the first wheel set 37 is significantly higher than the output torque of the wheels of the second wheel set 43. This is particularly ad- vantageous for climbing the ramps 14, 16, 20, 22 along the first axis x by driving with the first wheel set 37. Preferably, the first wheel set 37 and/or the second wheel set 43 are driven as a four-wheel drive. [113] The second chossis 60. on which the second wheel set 43 is mounted, is vertically movable by four vertically extending ieadscrews 75 arranged close to the four vertical edges of the carriage 2. The lead- screws 75 are mechanically coupled via transmission belts 77 to a pair of lift motors 79 (see Fig. 6) for simultaneously driving all four Ieadscrews 75. The Ieadscrews 75 are mounted on the first chassis 59 and the second chassis 60 is mounted to the Ieadscrews 75 by lifting elements 81 engag- ing with an outer thread of the Ieadscrews 75 and thereby vertically mov- ing upon rotation of the Ieadscrews 75. The carriage 2 further comprises vertically acting springs 83 that are expanded upon a downward move- ment of the second chossis 60 relative to the first chassis 59 and released upon an upward movement of the second chassis 60 relative to the first chassis 59. The springs 83 thus preloaded for pulling the second chassis 60 upward. The carriage 2 further comprises at least one detector element 85 for detecting other carriages 2 or obstacles in the path along the first axis X and for avoiding collisions.

[114] As shown in Fig. 6. a first output of the gear system 73 is mechani- cally coupled to the two wheels of first wheel set 37 arranged on the left- hand side of the carriage 2 by at least one first drive shaft 87 extending along the second axis y. Analogously, a second output of the gear sys- tem 73 is mechanically coupled to the two rear wheels of the second wheel set 43 by at least one second drive shaft 89 extending along the first axis x.

[115] The rear wheels of the second wheel set 43 are coupled to the second drive shaft 89 by means of a transmission belt 91 so that the sec- ond wheel set 43 con be driven at any vertical position of the second chassis 60 relative to the first chassis 59. The carriage 2 further comprises a rechargeable battery 93 in form of a stack of battery modules for sup- plying the carriage 2 with electrical power. The carriage 2 further com- prises a control system 94 comprising hardware in form of control elec- tronics on one or more printed circuits boards (PCBs) and software configured to control the carriage 2. The details of how the control sys- tem 94 works and is connected for executing the method for automaii- caily storing ond/or retrieving containers 4 in the racks 6 of the storage rack arrangement 3 is schematically displayed in Fig. 10.

[116] Fig.6 also shows the securing and centring system with the engag- ing elements 41. The carriage 2 comprises a securing motor 95 for actu- ating at least one first actuator shaft 97 extending essentially along the first axis x. The first actuator shaft 97 is mechanically coupled to a pair of second actuator shafts 99 extending along the second axis y. The sec- ond actuator shafts 99 is configured to drive the engaging elements be- tween the idle position and the securing position by rotating about the second axis y, wherein one of the pair of actuator shafts 99 rotates clock- wise while the other one of the pair of actuator shafts 99 rotates counter- clockwise. The details of the securing and centring system are better vis- ible in Fig. 9a,b.

[117] As shown in Figs. 6 and 7, the support surface 39 is mounted on four vertical columns 101 that are vertically movable in parallel to each other. The lift motors 79 are used to drive the lifting motion of the support surface 39. The total vertical path of the lifting elements 81 along the leadscrews 75 has two path sections, i.e. a lower path section and an upper path section. In the lower path section, the lifting elements 81 are used for lifting/lowering of the second wheel set 43, and, in the upper paih section, they are used for lifting/lowering of the support surface 39. Therefore, the lifting elements 81 mounted on the leadscrews 75 have a dual functionality, i.e. for pushing the second wheel set 43 downward against the springs 83 in the lower path section and for pushing the sup- port surface 39 upward in the upper path section. The upper end of the springs 83 is mounted to a spring bracket 102, wherein the vertical loca- tion of the spring bracket 102 defines the transition between the lower path section and the upper path section. When the lifting elements 81 move upward from the lower path section towards the upper path sec Hon, the springs 83 are contracting and pulling the second wheel set 43 upward. When the springs 83 ore fully contracted, the second wheel set 43 has reached the idle position. The lifting elements 81 enter the up- per path section upon further upward movement after the second wheel set 43 has reached the idle position. In the upper path section, the lifting elements 81 push the support surface 39 upward into a lifted position. This is particularly advantageous, because the lifted position of the support surface 39 is only needed when the second wheel set 43 is in the idle position.

[118] Figs. 9a, b show only the support surface 39 having a width W ₃ and a length L ₅ together with the securing and centring system, wherein Fig. 9a shows the engaging elements 41 being in the idle position and Fig. 9b shows the engaging elements 41 being in the securing position. The length L of the carriage 2 thus relates to the length of the support surface

39 by the formula L = L _s + 2 · S , wherein S is the distance of the support surface 39 to the longitudinal ends of the carriage 2, i.e. the front side 47 and the back side 49. The width W _s of the support surface 39 is only slightly smaller than the width W of the carriage 2. The engaging elements 41 are arranged in two corresponding pairs of a left-hand side engaging element 41 and a right-hand side engaging element 41. The left-hand side engaging elements 41 are rotatable simultaneously to the right- hand side engaging elements 41, but in the opposite direction. This is achieved by a pair of first actuator shafts 97 acting as connection rods being hinged at diametrically opposite sides to a rotor axle of the secur- ing motor 95 in a way similar to a crank shaft. The rotation of the securing motor 95 is thereby transformed into a mutually opposite pushing and pulling motion of the first actuator shafts 97 essentially along the first axis x. The laterally outer end of each first actuator shaft 97 is hinged from below to one of the pair of second actuator shafts 99 being rotatably mounted to the support surface 39 from below by brackets 103. The mu- tually opposite pushing and pulling motion of the first actuator shafts 97 rotates the second actuator shafts 99 in opposite directions (as indicted by the dashed arrows). The engaging eiements 41 extend radially from the second actuator shafts 99 in form of hooks that are configured to project through openings in the support surface 39 when they are moved from the idle position into the securing position. Preferably, in the securing position, the hooks 41 hook into a corresponding recess in the receiving elements 67 to secure the container 4 safely against tipping over and slipping off the support surface 39. The engaging elements 41 do not pro- ject through the openings in the support surface 39 when they are in the idle position as shown in Fig. 9a. They are thus “stowed away” in the idle position (Fig. 9a), A mutually opposite pulling motion of the first actuator shafts 97 results in a simultaneous securing motion of the engaging ele- ments 41 of about 90 degrees outward from the idle position (Fig. 9a) towards the securing position (Fig. 9b). A mutually opposite pushing mo- tion of the first actuator shafts 97 results in a simultaneous unsecuring mo- tion the engaging elements 41 of about 90 degrees inward from the se- curing position (Fig.9b) towards the idle position (Fig.9a). Preferably, the securing motor 95 is a step motor configured to drive selectively in two directions about a defined rotation angle of up to 180 degrees. [119] In the securing position of the engaging elements 41 shown in Fig.

9b, the hooks 41 are hooked into recesses 67 at the bottom of the con- tainer 4 (not shown in Fig. 9b) for securing the container 4 on the support surface 39. On the way from the idle position (Fig. 9a) towards the secur- ing position (Fig. 9b), the hooks move essentially laterally outward after they have moved essentially upward to pass through the openings in the support surface 39. The outward movement of the hooks is used to centre the container 4 relative to the central symmetry plane yz before it is se- cured on the support surface 39. [120] Figs. 10a, b show another embodiment of a carriage 2, wherein the wheels of the first wheel set 37 and the wheels of the second wheel set 43 extend at least partially out of the outer contour of the carriage 2, i.e. they are not fully embedded in the oute contour of the carriage 2 as shown in the embodiments of Figs. 2-8. This is particularly useful for the first wheel set 37, because the ramps 14, 16, 20, 22 extend predominantly along the first axis x to climb a track level between two connection points

24.

[121] The ramps 14, 16, 20, 22 may be shaped as shown in Figs. 10a,b comprising a maximum slope angle of approximately 15 degrees. The ramps 14, 16, 20, 22 may comprise a lower concave portion 104 with a smoothly upwardly rising slope angle and an upper convex portion 106 with a smoothly upwardly falling slope angle. There may be a straight portion 108 with a constant maximum slope angle arranged between the lower concave portion 104 and the upper convex portion 106. Pref- erably, the lateral end points of the ramps 14, 16, 20, 22 have essentially zero slope angle where they connect to the connection points 24. This shape allows for a smooth change of the track level and reduces the risk of tipping over for the carriage 2 carrying the container 4.

[122] The ramps 14, 16, 20, 22 may further comprise securing rails 110 comprising a securing surface 112 facing essentially downward and ar- ranged at a distance to a running surface 114 of the first rail tracks 36. The distance is slightly larger than the diameter of the wheels of the first wheel set 37, so that the wheels of the first wheel set 37, that extend for- wardly and backwardly out of the contour of the of the carriage 2, are able to run on the running surface 114 below the securing surface 112. The securing rails 110 have here a C-profiie partly embracing the wheels of the first wheel set 37. The securing rails 110 here extend along the straight portion 108 having the constant maximum slope angle so that tipping over of the carriage 2 is prevented where the slope angle is larg- est. If the carnage 2 carrying the container 4 starts tipping over, for in- stance due to momentum of container load sliding downwards within the container 4, the wheels ot the first wheel set 37 may shortly lift off from the running surface 114 of the first rail tracks 36 to abut against the secur- ing surface 112. The wheels of the first wheel set 37 will then return downwards to run on the running surface 114 again. Thus, the securing rails 110 secure the carnage 2 on steep portions of the ramps 14, 16, 20,

22. [ 123] Fig. 11 shows how the control system 94 is connected to other components and modules for controlling the carriage 2. The other com- ponents and modules may be implemented by hardware inside and/or outside the carriage 2. Alternatively, or in addition, the other compo- nents and modules may be implemented by executable software in- stalled inside and/or outside the carriage 2. For instance, the control sys- tem 94 may be signal connected to an interface module 105 for com- municating with an external main control system of the storage system 25. The control system 94 may receive commands and/or information from the main control system of the storage system 25 via the interface module 105. The control system 94 may send status reports, position infor- mation, warnings, failures or other information to the main control system of the storage system 25 via the interface module 105. The interface module 105 preferably provides for a wireless communication connec- tion.

[124] The control system 94 is further signal connected to a drive module 107 for controlling the drive motor 71, one or more lift modules 109 for controlling the one or more lift motors 79, and a securing module 111 for controlling the securing motor 95. The control system 94 is further signal connected to a detector module 113 for communicating with the at least one detector element 85 and/or the sensor arrangement 69. The control system 94 may thus receive signals from the detector element 85 and/or the sensor arrangement 69 indicative of information about the own position of the carriage 2 and the position and/or driving direction and/or speed of other carnages in the vicinity.

[125] Where, in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents. then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present disclosure, which should be construed so as to en- compass any such equivalents. It will also be appreciated by the reader that integers or features of the disclosure that ore described os optional, preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims.

[126] The above embodiments are to be understood as illustrative ex- amples of the disclosure, It is to be understood that any feature de- scribed in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodi- ments, or any combination of any other of the embodiments. While at least one exemplary embodiment has been shown and described, it should be understood that other modifications, substitutions and alter- natives ore apparent to one of ordinary skill in the art and may be changed without departing from the scope of the subject matter de- scribed herein, and this application is intended to cover any adapta- tions or variations of the specific embodiments discussed herein.

[127] In addition, "comprising” does not exclude other elements or steps, and "a" or "one” does not exclude a plural number. Furthermore, characteristics or steps which have been described with reference to one of the above exemplary embodiments may also be used in combi- nation with other characteristics or steps of other exemplary embodi- ments described above. Method steps may be applied in any order or in parallel or may constitute a part or a more detailed version of an- other method step. It should be understood that there should be em- bodied within the scope of the patent warranted hereon ail such modi- fications as reasonably and properly come within the scope of the con- tribution to the art. Such modifications, substitutions and alternatives can be made without departing from the spirit and scope of the disclosure, which should be determined from the appended claims and their legal equivalents. [128] List of reference numerals:

1 track arrangement 2 carnage

3 storage rack arrangement

4 container

5 storage site

6 rack 8 aisle track

9 aisle

10 interaction site

1 1 horizontal track

13 first sequence of first one-way ramps 14 first one-way ramp

15 second sequence of second one-way romps

16 second one-way ramp

19 third sequence of third one-way ramps

20 third one-way ramp 21 fourth sequence of fourth one-way ramps

22 fourth one-way ramp

24 connection point

25 automated storage system

26 interaction track 27 entry point

28 exit point

11 horizontal track

31 connection track

32 front face 36 first rail tracks

37 first wheel set

38 second rail tracks 39 support surface

41 engaging element

43 second wheel set

47 front side of carriage 49 back side of carriage

51 left side of carriage

53 right side of carriage

55 first track gauge

57 second track gauge 59 first chassis

60 second chassis

61 guiding element

63 first wheel base

65 second wheel base 67 receiving element

69 sensor arrangement

71 drive motor

73 gear system

75 leadscrew 77 transmission belt

79 lift motor

81 lifting element

83 spring

85 detector element 87 first drive shaft

89 second drive shaft

91 transmission belt

93 battery

94 control system 95 securing motor

97 first actuator shaft

99 second actuator shaft 101 vertical column

102 spring bracket

103 bracket

104 lower concave portion 105 interface module

106 upper convex portion

107 drive module

108 straight portion

109 lift module 110 securing rails

111 securing module

112 securing surface

113 detector module

114 running surface X first axis y second axis z vertical axis

X number of track columns

Y number of track rows Z number of track levels h height of container

H height of carriage d range of support surface lift

S distance of support surface to longitudinal ends of carriage W _s width of support surface

Ls length of support surface