Patent Description:
<FIG> discloses a typical prior art automated storage and retrieval system <NUM> with a framework structure <NUM> and <FIG> disclose prior art container handling vehicles <NUM>, <NUM> of such a system <NUM>.

The framework structure <NUM> comprises a plurality of upright members <NUM> and a plurality of horizontal members <NUM> which are supported by the upright members <NUM>.

The framework structure <NUM> defines a storage grid <NUM> comprising storage columns <NUM> arranged in rows, in which storage columns <NUM> storage containers <NUM>, also known as bins, are stacked one on top of another to form stacks <NUM>. Each storage container <NUM> may typically hold a plurality of product items (not shown), and the product items within a storage container <NUM> may be identical, or may be of different product types depending on the application. The storage grid <NUM> guards against horizontal movement of the containers in the stacks <NUM>, and guides vertical movement of the containers <NUM>, but does normally not otherwise support the storage containers <NUM> when stacked.

Some of the horizontal members <NUM> comprise a rail system <NUM> arranged in a grid pattern across the top of the storage columns <NUM>, on which rail system <NUM> a plurality of container handling vehicles <NUM> are operated to raise storage containers <NUM> from - and lower storage containers <NUM> into - the storage columns <NUM>, and also to transport the storage containers <NUM> above the storage columns <NUM>. The rail system <NUM> comprises a first set of parallel rails <NUM> arranged to guide movement of the container handling vehicles <NUM> in a first direction X across the top of the frame structure <NUM>, and a second set of parallel rails <NUM> arranged perpendicularly to the first set of rails <NUM> to guide movement of the container handling vehicles <NUM> in a second direction Y, which is perpendicular to the first direction X. In this way, the rail system <NUM> defines grid columns <NUM> above which the container handling vehicles <NUM> can move laterally above the storage columns <NUM>, i.e. in a plane which is parallel to the horizontal X-Y plane.

Each container handling vehicle <NUM> comprises a vehicle body 101a, and first and second sets of wheels 101b, 101c which enable the lateral movement of the container handling vehicle <NUM> in the X direction and in the Y direction, respectively. In <FIG> two wheels in each set are visible. The first set of wheels 101b is arranged to engage with two adjacent rails of the first set of rails <NUM>, and the second set of wheels 101c is arranged to engage with two adjacent rails of the second set of rails <NUM>. Each set of wheels 101b, 101c can be lifted and lowered, so that the first set of wheels 101b and/or the second set of wheels 101c can be engaged with the respective set of rails <NUM>, <NUM> at any one time.

Each container handling vehicle <NUM> also comprises a lifting device (not shown in <FIG>) for vertical transportation of storage containers <NUM>, e.g. raising a storage container <NUM> from, and lowering a storage container <NUM> into, a storage column <NUM>. The lifting device comprises a gripping device (not shown) which is adapted to engage a storage container <NUM>, and which gripping device can be lowered from the vehicle body 101a so that the position of the gripping device with respect to the vehicle body 101a can be adjusted in a third direction Z which is orthogonal the first direction X and the second direction Y.

Conventionally, and also for the purpose of this application, Z=<NUM> identifies the uppermost storage layer of the grid <NUM>, i.e. the layer immediately below the rail system <NUM>, Z=<NUM> the second layer below the rail system <NUM>, Z=<NUM> the third layer etc. In the exemplary prior art grid disclosed in <FIG>, Z=<NUM> identifies the lowermost, bottom layer of the grid <NUM>. Similarly, X=<NUM> identifies the first row of columns in the X direction from the corner chosen as the origin, and Y=<NUM> identifies the first row of columns in the Y direction from the corner chosen as the origin. Consequently, as an example, and using the Cartesian coordinate system X, Y, Z indicated in <FIG>, the storage container identified as <NUM>' in <FIG> can be said to occupy grid location or cell X=<NUM>, Y=<NUM>, Z=<NUM>. The container handling vehicles <NUM> can be said to travel in layer Z=<NUM> and each grid column <NUM> can be identified by its X and Y coordinates. Each container handling vehicle <NUM> comprises a storage compartment or space for receiving and stowing a storage container <NUM> when transporting the storage container <NUM> across the rail system <NUM>. The storage space may comprise a cavity arranged centrally within the vehicle body 101a, e.g. as is described in <CIT>.

Alternatively, the container handling vehicles <NUM> may have a cantilever construction as illustrated in <FIG> and is described in <CIT>.

The container handling vehicles <NUM> may have a footprint (i.e. a footprint that covers an area with dimensions in the X and Y directions), which is generally equal to the area defined by the lateral extension in the X and Y directions of a grid column <NUM>, e.g. as is described in <CIT>.

The term "lateral" used herein may mean "horizontal".

Alternatively, the container handling vehicles <NUM> may have a footprint which is larger than the lateral area defined a grid column <NUM>, e.g. as is disclosed in <CIT>.

The rail system <NUM> may be a single track system, as is shown in <FIG>. Alternatively, the rail system <NUM> may be a double track system, as is shown in <FIG>, thus allowing a container handling vehicle <NUM> having a footprint generally corresponding to the lateral area defined by a grid column <NUM> to travel along a row of grid columns even if another container handling vehicle <NUM> is positioned above a grid column neighboring that row. Both the single and double track systems, or systems using a combination of single and double tracks, form a grid pattern in the horizontal plane P comprising a plurality of rectangular and uniform grid locations or grid cells <NUM>, where each grid cell <NUM> comprises a grid opening <NUM> being delimited by a pair of rails 110a, 110b of the first set of rails <NUM> and a pair of rails <NUM><NUM>1a, <NUM>11b of the second set of rails <NUM>. In <FIG> the grid cell <NUM> is indicated by a dashed box.

Each grid cell <NUM> has a width which is typically within the interval of <NUM> to <NUM>, and a length which is typically within the interval of <NUM> to <NUM>. Each grid opening <NUM> has a width and a length which is typically <NUM> to <NUM> less than the width and the length of the grid cell <NUM>.

In a storage grid <NUM>, a majority of the grid columns <NUM> are storage columns <NUM>, i.e. grid columns <NUM> wherein storage containers <NUM> are stored in stacks <NUM>. However, a grid <NUM> normally has at least one grid column <NUM> which is used not for storing storage containers <NUM>, but which comprises a location where the container handling vehicles <NUM> can drop off and/or pick up storage containers <NUM> so that they can be transported to an access station (not illustrated herein) where the storage containers <NUM> can be accessed from outside of the grid <NUM> or transferred out of or into the grid <NUM>. Within the art, such a location is normally referred to as a "port" and the grid column <NUM> in which the port is located may be referred to as a "port column" <NUM>, <NUM>.

The grid <NUM> in <FIG> comprises two port columns <NUM> and <NUM>. The first port column <NUM> may for example be a dedicated drop-off port column where the container handling vehicles <NUM> can drop off storage containers to be transported to an access or a transfer station and the second port column <NUM> may be a dedicated pick-up port column where the container handling vehicles <NUM> can pick up storage containers <NUM> that have been transported to the grid <NUM> from an access or a transfer station.

The access station may typically be a picking or a stocking station where product items are removed from or positioned into the storage containers <NUM>. In a picking or a stocking station the storage containers <NUM> are normally never removed from the automated storage and retrieval system <NUM>, but are returned into the grid <NUM> once accessed. A port can also be used for transferring storage containers out of or into the grid <NUM>, e.g. for transferring storage containers <NUM> to another storage facility (e.g. to another grid or to another automated storage and retrieval system), to a transport vehicle (e.g. a train or a lorry), or to a production facility.

A conveyor system comprising conveyors is normally employed to transport the storage containers between the ports <NUM>, <NUM> and the access station If the port and the access station are located at different levels, the conveyor system may comprise a lift device for transporting the storage containers <NUM> vertically between the port <NUM>, <NUM> and the access station.

The conveyor system may be arranged to transfer storage containers <NUM> between different grids, e.g. as is described in <CIT>. <CIT>, discloses an example of a prior art access system having conveyor belts (Figs. 5a and 5b therein) and a frame mounted track (Figs. 6a and 6b therein) for transporting storage containers between ports and work stations where operators can access the storage containers.

When a storage container <NUM> stored in the grid <NUM> disclosed in <FIG> is to be accessed, one of the container handling vehicles <NUM> is instructed to retrieve the target storage container <NUM> from its position in the grid <NUM> and transport it to the drop-off port <NUM>. This operation involves moving the container handling vehicle <NUM> to a grid location above the storage column <NUM> in which the target storage container <NUM> is positioned, retrieving the storage container <NUM> from the storage column <NUM> using the container handling vehicle's <NUM> lifting device (not shown), and transporting the storage container <NUM> to the drop-off port <NUM>. This step, which is sometimes referred to as "digging" within the art, may be performed with the same container handling vehicle that is subsequently used for transporting the target storage container to the drop-off port <NUM>, or with one or a plurality of other cooperating container handling vehicles.

When a storage container <NUM> is to be stored in the grid <NUM>, one of the container handling vehicles <NUM> is instructed to pick up the storage container <NUM> from the pick-up port <NUM> and transport it to a grid location above the storage column <NUM> where it is to be stored. After any storage containers positioned at or above the target position within the storage column stack <NUM> have been removed, the container handling vehicle <NUM> positions the storage container <NUM> at the desired position. The removed storage containers may then be lowered back into the storage column <NUM>, or relocated to other storage columns.

For monitoring and controlling the automated storage and retrieval system <NUM>, e.g. monitoring and controlling the location of respective storage containers <NUM> within the grid <NUM>; the content of each storage container <NUM>; and the movement and traffic flow of the container handling vehicles <NUM> so that a desired storage container <NUM> can be delivered to the desired location at the desired time without the container handling vehicles <NUM> colliding with each other, the automated storage and retrieval system <NUM> comprises a central control system which typically is computerized and which typically comprises a database for keeping track of the storage containers <NUM>.

The container handling vehicles comprise a vehicle control unit which is signally connected to the central control system for transmittal and receival of data signals. The vehicle control unit is connected to the driving means of the vehicle, the lifting means and any sensors on the vehicle, and may relay and/or process data signals between components of the vehicle and the central control system. For example, as is known from prior art document <CIT>, sensors on the container handling vehicle arranged near the track measure whenever a track crossing has been passed, and thus the vehicle control unit can keep track of its position on the grid which may further be relayed to a central control system.

A problem associated with known traffic flow management is that the area surrounding certain cells, such as ports <NUM>, <NUM> or other columns frequently visited by container handling vehicles, may become congested with the container handling vehicles <NUM> instructed to drop off or pick up storage containers <NUM>. As one container handling vehicle <NUM> is blocking access to a target cell <NUM>, which may be e.g. one of the grid cells <NUM> or one of the ports <NUM>,<NUM>, another container handling vehicle <NUM> may start queuing up on an adjacent cell awaiting access to the target cell <NUM>. Once the container handling vehicle <NUM> blocking access to the target cell <NUM> has moved away from its blocking position, it is desirable to move the queuing container handling vehicle into the target cell <NUM> as quickly as possible.

A problem with the prior art is that the position of a container handling vehicle is not known with certainty until it has passed a track crossing. The position of the container handling vehicle may then be transmitted to the central control system which processes this information to establish whether a queuing container handling vehicle can move into the target cell <NUM>. This results in a delay due to the command being relayed through, and processed in, the central control system. Moreover, delays will occur in situations where access to the target cell <NUM> is free, but the formerly blocking container handling vehicle has not yet established and transmitted its new position. Furthermore, the relaying of this information takes up limited capacity on the communications bandwidth between the container handling vehicles <NUM> and the control system.

In view of the above, it is desirable to provide an automated storage and retrieval system, and a method for operating such a system, that solves or at least mitigates one or more of the aforementioned problems related to use of prior art storage and retrieval systems.

<CIT> describes, according to its abstract, a method for fetching a target bin stored in a storage system (<NUM>), wherein the storage system includes a three-dimensional storage grid containing a plurality of bins stacked in vertical stacks, supporting rails (<NUM>) on the grid structure, and a plurality of vehicles (<NUM>), controllably arranged to move individually on the supporting rails. The method is performed by a control device in the system and comprises controlling at least one non-target vehicle to operate as intermediate storage for a bin located vertically above the target bin (<NUM>); controlling a target vehicle to pick up the target bin, and controlling the at least one non-target vehicle and the target vehicle to be positioned adjacent to each other in a linear manner on the supporting rails. A corresponding storage system has also been disclosed.

The present invention is set forth and characterized in the main claims, while the dependent claims describe optional features of the invention.

Accordingly, the present invention relates in an aspect to a method of operating an automated storage and retrieval system, the automated storage and retrieval system comprising:.

Thus, the invention allows for more efficient and faster queuing of container handling vehicles accessing a target cell, as the first container handling vehicle does not have to wait for the second handling vehicle to transmit its new cell position to the central control unit, and/or for the central control unit to process this information and then command the first container handling vehicle to move into the target cell. The invention may be especially advantageous where container handling vehicles are operating on a rail system in the vicinity of port columns, and where container handling vehicles comprising container delivery vehicles are operating on a rail system for delivery of storage containers to be picked at an access point. The invention may be especially advantageous where the target cell is free, or it is considered acceptable for the first container handling vehicle to start moving into the target cell, but it would not move in the prior art as it requires a command to do so from the central control unit. The invention may therefore allow the first container handling vehicle to start moving towards the target cell whilst the second container handling vehicle is still partially within the target cell. The invention may also provide a more efficient use of bandwidth in the automated storage system, as unnecessary signals back and forth between the central control unit and the container handling vehicles are reduced. The processing power of the central control unit may also be used more efficiently as the first container handling vehicle does not require a separate command to move into the target cell when the control unit has computed that it is free, as is necessary in the prior art.

Transmitting a data signal from the central control unit to the vehicle control unit of the first container handling vehicle may comprise commanding the first container handling vehicle not to move into the target cell when the second container handling vehicle is within said predetermined distance. Thus, the first container handling vehicle may move if and only if the second container handling vehicle is distant enough.

The proximity sensor system may be configured to detect when another container handling vehicle is within a predetermined distance, i.e. by a Boolean value where the first container handling vehicle moves when the other container handling vehicle's distance is greater than the given value for the predetermined distance. The proximity sensor system may also be configured to detect another container handling vehicle when it is within a predetermined distance, i.e. the proximity sensor system does detect anything beyond said distance. The first container handling vehicle will thus only move if the proximity sensor system detects that the second vehicle is beyond the predetermined distance. To achieve redundancy in case of a failure to detect another container handling vehicle within the predetermined distance, the second container handling vehicle may have redundancy measures such as transmitting a signal that it has moved clear of blocking the target cell to the central control unit as is known in the prior art. Also, the first container handling vehicle may transmit that it has arrived at the target cell to the central control unit as is known in the prior art.

The proximity sensor system may typically be capable of measuring a target up to a given distance of e.g. <NUM> meters, as this may be length of a grid cell. However, the predetermined distance may be calculated and set by the central control unit according to the requirements and specification of the automated storage system, such as the size and travelling speed of the container handling vehicle and the size of the grid cells which may be dependent on the direction of travel of a container handling vehicle. Each vehicle control unit may also be able to calculate the predetermined distance based on parameters such as the size and travelling speed of the container handling vehicle and which direction it is travelling in. The predetermined distance may also be provided in the data signal sent from the central control system, such that the distance may vary depending on what the central control system has computed to be suitable. For example the predetermined distance may be shortened in periods of heavy traffic. The predetermined distance may be smaller than the size of a grid cell in either of the two perpendicular directions.

A target cell may be a cell which is frequently visited by container handling vehicles and therefore experiences a substantial amount of traffic, for example a grid cell located over a port column. However, the invention is not limited to port cells and may provide improved traffic handling for all kinds of cells, such as cells located over storage columns. The container handling vehicle may comprise container delivery vehicles, and accordingly a target cell may be located beneath a port column of the grid or at an access point, typically at the edge of the rail system, where the container delivery vehicle is to deliver a storage container to be picked.

Typically, the second handling vehicle may block access to a target cell when it at least partially covers said target cell. However, the second handling vehicle may for example also block access to a target cell in cases where it occupies an adjacent cell to the target cell, and the first handling vehicle has an extent which is larger than the lateral area defined by a grid column. Thus, the term moving clear does not necessarily imply that the second container handling vehicle is above or covering the target cell, but rather that it obstructs a first container handling vehicle from entering the target given the movement constraints of the rail system.

The invention may thus be advantageous where container delivery vehicles operate on a rail system, as these rails systems can become heavily trafficked.

The target cell may be defined as a cell to which the first container handling vehicle has received a command to move to. A plurality of container handling vehicles may form queues, which may be typical around port cells. In such cases the invention may provide a more efficient and smooth movement of the container handling vehicles as access to the port cell is freed up and the first container handling vehicle in the queue moves in to the cell, whilst the other vehicles follow closely by the method disclosed herein, which allows them to move towards a target cell whilst another vehicle is still partially in the target cell.

The vehicle control system of the first container handling vehicle may derive which parts of the proximity sensor system require activation based on the command it receives from the central control system, which typically may be the part of the proximity sensor system arranged to measure in the direction in which the first container handling vehicle is commanded to drive to reach the target cell. In other aspects, the central control system may include instructions in the data signal as to which parts of the proximity sensor system is to be activated. The vehicle control system may further receive instructions in the data signal regarding the duration of activation for the proximity sensor system, which may depend on whether the first container handling vehicle is following the second container handling vehicle in a parallel direction, or the second container handling vehicle moves in an orthogonal direction. It may for example be advantageous to keep the proximity sensor system activated when the first container handling vehicle follows the second container handling vehicle to avoid collisions.

In aspects, the predetermined distance may be measured from a side surface of the first container handling vehicle in a direction of the tracks. Preferably, said side surface may form part of a vertical plane parallel to a direction of one of the sets of tracks and tangent to the an outermost lateral blocking extension in the X and Y directions of a container handling vehicle. Where the outermost lateral blocking extension may be defined as a physical part of a container handling vehicle which would limit another container handling vehicle to pass by the first container handling vehicle in an adjacent cell. Elastic antennas, brushes and other deformable objects not posing a physical barrier may therefore not be regarded as forming an outermost extension. It should however be noted that a container handling vehicle may comprise a lateral extension which does not constitute a lateral blocking section, for example container handling vehicles with a protruding section on one side may also comprise a complementary recessed section on an opposite side, or the protruding section may be arranged to extend above other container handling vehicles on the grid.

By defining a side surface as described above, the proximity sensor system may thus advantageously be arranged at different locations on the container handling vehicle with varying distance to a side surface, which may depend on the construction of the container handling vehicle and its outermost lateral blocking extensions.

In aspects, each container handling vehicle may comprise four side surfaces comprising:.

The rectangular zone of a container handling vehicle on the track system may thus define the area on the grid which a container handling vehicle takes up or the area which the vehicle obstructs other vehicles from entering, and where other container handling vehicles cannot pass by, and thus provide the central control system with an overview of whether it occupies a grid column or not. Each side surfaces may also define the lateral extent where the proximity sensor system is required to measure.

The method may comprise transmitting a data signal from the central control unit to the vehicle control unit of the second container handling vehicle commanding the second container handling vehicle to move clear of the target cell. The data signal to the second container handling vehicle may be transmitted before or after the data signal to the first container handling vehicle is transmitted. For example the data signal to the second container handling vehicle may have been transmitted before, but the second container handling vehicle is busy operating at its current location, and has therefore not yet moved when the first container handling vehicle arrives and is blocked from accessing the target cell.

The method may comprise transmitting a data signal from the central control unit to the vehicle control unit of the second container handling vehicle commanding the second load handling vehicle to move clear of the target cell and to another location of the rail system. The data signal commanding the second container handling vehicle to move clear of the target cell may be a normal command with a new task of for example retrieving or depositing a container at another location in the grid.

The method may comprise transmitting a data signal from the central control unit to the vehicle control unit of the second container handling vehicle commanding the second container handling vehicle to move in a direction parallel to the direction between the target cell and the first container handling vehicle. Thus, the first container handling vehicle and the second container handling vehicle may move in a parallel or the same direction.

The method may comprise continuously monitoring with the proximity sensor system of the first container handling vehicle as it moves into the target cell to detect if the second container handling vehicle is within a predetermined distance. Thus, the first container handling vehicle may monitor whether the second container handling vehicle unexpectedly stops, such that it may itself stop moving and avoid a collision. Continuous monitoring may thus be advantageous when the container handling vehicles move in the same or a parallel direction. The data signal transmitted to the first container handling vehicle may thus command it to continuously monitor the predetermined distance in its direction of travel.

When the container handling vehicles move in a parallel direction, the predetermined distance may be set to slightly above the length or width of a grid cell in the direction of travel. For example between <NUM> and <NUM> centimeters, or between <NUM> and <NUM> centimeters depending on the direction of travel. However, the predetermined distance may vary depending on the speed of the container handling vehicles. The predetermined distance may also be set to slightly below the length or width of a grid cell in the direction of travel, this may be advantageous e.g. during periods of heavy traffic and where queues of multiple container handling vehicles line up. However, the distance between the side surfaces of the first container handling vehicle and the second container handling vehicle, once the first container handling vehicle is located on the grid cell adjacent the target cell, may also be taken into account.

The method may comprise transmitting a data signal from the central control unit to the vehicle control unit of the second container handling vehicle commanding the second container handling vehicle to move in a direction orthogonal to the direction between the target cell and the first container handling device.

Typically, when the container handling vehicles move in an orthogonal direction to each other, the predetermined distance may be set to slightly above the width of the rails, i.e. between <NUM>-<NUM> centimeters. The data signal transmitted to the first container handling vehicle may also command it to only monitor the predetermined distance until the second container handling vehicle is no longer within the predetermined distance. The data signal may also comprise details regarding the direction of travel of the second container handling vehicle, such that the vehicle control unit of the first container handling vehicle may decide which parts of the proximity sensor system needs to monitor the predetermined distance. However, the distance between the side surfaces of the first container handling vehicle and the second container handling vehicle, once the first container handling vehicle is located on the grid cell adjacent the target cell, may also be taken into account.

The proximity sensor system of the first container handling vehicle may measure the predetermined distance from a side surface of a plurality of side surfaces of the first container handling vehicle and wherein the predetermined distance is defined in a direction of the rails. Preferably, said side surface may form part of a vertical plane perpendicular to the plane defined by both of the rails and parallel to a direction of one of the sets of rails, and tangent to an outermost lateral blocking extension in the X and Y directions of a container handling vehicle, where the outermost lateral blocking extension may be defined as a physical part of a container handling vehicle which would limit another container handling vehicle to pass by the first container handling vehicle in an adjacent cell. Elastic antennas, brushes and other deformable objects not posing a physical barrier may therefore not be regarded as forming an outermost extension. It should however be noted that a container handling vehicle may comprise a lateral extension which does not constitute a lateral blocking section, for example container handling vehicles with a protruding section on one side may also comprise a complementary recessed section on an opposite side, or the protruding section may be arranged to extend above other container handling vehicles on the grid.

The method may comprise determining with the vehicle control unit from which side surface of the first container handling vehicles to detect the second container handling vehicle. Typically, the first container handling vehicle may monitor in its direction of intended travel. The central control unit may further provide the direction of travel of the second container handling vehicle such that the vehicle control unit can determine with which parts of the proximity sensor system to monitor.

The method may comprise transmitting a data signal from the central control unit to the vehicle control unit of the first container handling vehicle to specify the predetermined distance.

In an aspect, the invention relates to an automated storage and retrieval system comprising:.

Alternatively, not all container handling vehicles of an automated storage and retrieval system may comprise proximity sensors. It may be conceivable that only a portion of the plurality of container handling vehicles comprise proximity sensors. This may be because only a certain portion of the container handling vehicles are required to operate in heavily trafficked areas, or it could be because a portion of the plurality of container handling vehicles belong to a generation of vehicles of the prior art which did not require proximity sensors and not all vehicles have been replaced.

The predetermined distance may be measured from a side surface of a container handling vehicle in a direction of the rails.

Each container handling vehicle may comprise four vertical side surfaces:.

The rectangular cross section of a container handling vehicle on the track system may thus define the area on the grid which a container handling vehicle takes up, or the area which the vehicle obstructs other vehicles from entering given the movement constraints of the rail system, and where other container handling vehicles cannot pass by. The rectangular cross section thus provides the central control system with an overview of whether it occupies a grid cell or not. Each side surfaces may also define the lateral extent where the proximity sensor system is required to measure.

The proximity sensor system may comprise at least any of:.

Thus, a container handling vehicle may comprise only one, two, three or four part sensor systems. In some storage systems, it may be apparent that a container handling vehicle only requires one part sensor system in a certain direction and therefore it may be cheaper to provide container handling vehicles with a minimal number of sensor systems. Likewise, some systems may only require container handling vehicles to comprise sensor systems in two or three directions, and the number of part sensor systems are accordingly provided.

The proximity sensor system may comprise at least two proximity sensors, wherein each of the at least two proximity sensors are arranged to detect another container handling vehicle at the boundaries of any of the side surfaces in the horizontal plane. Thus, the at least two proximity sensors of first container handling vehicle may detect when a second container handling vehicle has moved away from a blocking position in a direction orthogonal to the direction of which the first container handling vehicle has been commanded to move.

The proximity sensors may be of any kind which are known in the art, for example optical, radar, acoustic, magnetic, capacitive or a combination of these.

In other configurations, only one proximity sensor may be arranged per part sensor system, yet the one proximity sensor may be arranged such that it can detect along part of or the entire side surface, for example one sensor may be arranged which extends along an entire side surface. In some configurations, one proximity sensor may be arranged at a corner of two side surfaces and arranged to detect another container handling vehicle directed outward from at least one of the two side surfaces, in which case the proximity sensor may be regarded as part of both proximity sensor systems of the two sides, i.e. two part sensor systems share one common proximity sensor.

The rectangular cross section of any of the first or second container handling vehicles may correspond to an integer of grid cells. For example, both container handling vehicles may have a rectangular cross section corresponding to only one grid cell, in which case the second container handling vehicle may only block access to a target cell when it at least partially covers a target cell. In other examples, any of the container handling vehicles may have a rectangular cross section corresponding to an integer multiple of grid cells. For example, the first container handling vehicle may have a rectangular cross section corresponding to two whole grid cells, and the second container handling vehicle may have a rectangular cross section corresponding to only one grid cell. In this example, the second container handling vehicle may block access to the target cell even if it only partially covers a cell adjacent to the target cell.

The rectangular cross section of any of the first or second container handling vehicles may correspond to more than one grid cell. For example, the first container handling vehicle may have a rectangular cross section corresponding to only one grid cells, and the second container handling vehicle may have a rectangular cross section corresponding to one by one and a half grid cells.

As will be apparent to the person skilled in the art based on the disclosure of the invention herein, the system according to any of the aforementioned aspects may be configured to perform the method according to any of the aforementioned aspects.

In the following, numerous specific details are introduced by way of example only to provide a thorough understanding of embodiments of the claimed, method of operating an automated storage and retrieval system and an automated storage and retrieval system. One skilled in the relevant art, however, will recognize that these embodiments can be practiced without one or more of the specific details, or with other components, systems, etc. In other instances, well-known structures or operations are not shown, or are not described in detail, to avoid obscuring aspects of the disclosed embodiments.

Following drawings are appended by way of example only to facilitate the understanding of the invention.

In the drawings, like reference numerals have been used to indicate like parts, elements or features unless otherwise explicitly stated or implicitly understood from the context.

In the following, embodiments of the invention will be discussed in more detail by way of example only and with reference to the appended drawings.

The framework <NUM> of the automated storage and retrieval system <NUM> is constructed in accordance with the prior art framework <NUM> described above in connection with <FIG>, i.e. a number of upright members <NUM> and a number of horizontal members <NUM>, which are supported by the upright members <NUM>, and further that the framework <NUM> comprises a rail system <NUM> of parallel rails <NUM>,<NUM> in X direction and Y direction arranged across the top of storage columns <NUM> / grid columns <NUM>. The horizontal area of a grid column <NUM>, i.e. the area along the X and Y directions, may be defined by the distance between adjacent rails <NUM> and <NUM>, respectively (see <FIG>).

In <FIG> the grid <NUM> is shown with a height of eight cells. It is understood, however, that the grid <NUM> in principle can be of any size. In particular it is understood that grid <NUM> can be considerably wider and/or longer and/or deeper than disclosed in <FIG>. For example, the grid <NUM> may have a horizontal extent of more than 700x700 grid cells and a depth of more than twelve grid cells.

The grey area of <FIG> illustrates the projection <NUM> onto a horizontal plane of an irregularly shaped container handling vehicle <NUM> and the side surfaces <NUM>,<NUM>,<NUM>,<NUM> parallel to the first direction X and the second direction Y, on the tangent of the projection <NUM>, thereby forming a rectangular cross section <NUM> represented by the full line. Accordingly, a first side surface <NUM> and a second side surface <NUM> are parallel to a vertical plane V, illustrated by a dashed line, which is also parallel to the second direction Y, whilst a third side surface <NUM> and a fourth side surface <NUM> are parallel to vertical plane V, illustrated by another dashed line orthogonal to the one previously mentioned, which is also parallel to the first direction X. The projection <NUM> illustrates the outermost lateral blocking extent of the container handling vehicle in the first direction X and second direction Y, i.e. the outermost points of the container handling vehicle where another vehicle cannot pass by. As illustrated by the example along the first positive direction X+, the predetermined distance D is measured from the first side surface <NUM> independent of the shape of the container handling vehicle. As a proximity sensor system <NUM> on the container handling vehicle illustrated <FIG> cannot physically be arranged along the first side surface <NUM>, the distance from a sensor in the proximity sensor system <NUM> to the side surface <NUM> needs to be accounted for.

As shown in <FIG> the proximity sensor system <NUM> is arranged to detect along an entire side surface <NUM>,<NUM>,<NUM>,<NUM>. The first side surface <NUM> thus faces a positive first direction X+, a second side surface <NUM> faces a negative first direction X-, a third side surface <NUM> faces a positive second direction Y+ and a fourth side surface <NUM> facing a negative second direction Y-. The negative directions are oriented oppositely to their respective positive directions. The side surfaces <NUM>,<NUM>,<NUM>,<NUM> combined form a rectangular cross section <NUM> in the horizontal plane P such that the first side surface <NUM> and the second side surface <NUM> extend between the third side surface <NUM> and the fourth side surface <NUM> and vice versa.

As illustrated in <FIG>, the directions of detection of the proximity sensor system <NUM> are represented by the arrows pointing out from the side surfaces <NUM>,<NUM>,<NUM>,<NUM>. Thus, a first part sensor system 4X+ is arranged to detect along the first side surface <NUM> in a positive first direction X+, a second part sensor system 4X- is arranged to detect along the second side surface <NUM> in a negative first direction X-, a third part sensor system 4Y+ is arranged to detect along a third side surface <NUM> in a positive second direction Y+ and a fourth part sensor system 4Y is arranged to detect along the fourth side surface <NUM> in a negative second direction Y-.

<FIG> is a perspective view of a container handling vehicle <NUM>, illustrating how the side surfaces <NUM>,<NUM>,<NUM>,<NUM> may be defined on this type of container handling vehicle <NUM>. The dashed lines represent the horizontal and vertical borders of the side surfaces <NUM>,<NUM>,<NUM>,<NUM>, and as shown, the side surfaces <NUM>,<NUM>,<NUM>,<NUM> are parallel to respective vertical planes V and the respective first direction X and second direction Y. In this embodiment, the side surfaces <NUM>,<NUM>,<NUM>,<NUM> thus generally correspond to the physical side surfaces of the container handling vehicles <NUM> exterior housing, but as will be understood by the person skilled in the art, this may not always be the case, especially for an irregularly shaped container handling vehicle <NUM>. A coordinate system is inserted in <FIG> to illustrate how the second side surface <NUM> faces the first negative direction X-, and the fourth side surface <NUM> faces the negative second direction Y-. It should however be noted that the coordinates and the orientation of the container handling vehicle <NUM> in <FIG> are merely an example to illustrate how side surfaces <NUM>,<NUM>,<NUM>,<NUM> may be defined on a container handling vehicle <NUM>. The definition of which side is which, is dependent on the orientation of the container handling vehicle <NUM> as it is placed on a grid <NUM>, which gives the frame of reference as to what are the positive and negative first X, second Y and third Z directions. Four sensors <NUM> of the proximity sensor system <NUM> are exemplified as each being arranged in an upper corner of each side surface <NUM>,<NUM> of the exterior housing of the container handling vehicle <NUM>. As will be apparent, similar sensors may be found on the sides <NUM> and <NUM> of the container handling vehicle <NUM> not shown in <FIG>. Advantageously, the sensors <NUM> are arranged near the boundary of a side surface <NUM>,<NUM>,<NUM>,<NUM> as this allows them to detect the presence of another container handling vehicle moving parallel to said side surface.

In an alternative embodiment of the present invention the proximity sensor is placed on the top most surface of the container handling vehicle. In this embodiment a single proximity sensor can be used. This proximity sensor can be tilted or rotated in order to cover the entire <NUM> ° area around the container handling vehicle.

In yet another embodiment of the present invention four proximity sensors can be placed on the top most surface of the container handling vehicle. Using four sensors it is possible to cover the entire <NUM> ° area around the container handling vehicle without having to move the sensors. Each sensor covers one side of the container handling vehicle. A first proximity sensor is directed outwards in the positive first direction and is capable of detecting another container handling vehicle within said predetermined distance from the first side surface, and a second proximity sensor is directed outwards in the negative first direction and being capable of detecting another container handling vehicle within said predetermined distance from the second side surface, and a third proximity sensor is directed outwards in the positive second direction and being capable of detecting another container handling vehicle within said predetermined distance from the third side surface, and a fourth proximity sensor is directed outwards in the negative second direction and being capable of detecting another container handling vehicle within said predetermined distance from the fourth side surface.

<FIG> is a perspective view of a container handling vehicle <NUM>, illustrating how the side surfaces <NUM>,<NUM>,<NUM>,<NUM> may be formed on this type of container handling vehicle <NUM>. In this embodiment, it should be noted that the side surfaces <NUM>,<NUM>,<NUM>,<NUM> do not generally correspond to the exterior housing of the container handling vehicle <NUM>, apart from the second side surface <NUM>. Due to the cantilever construction of this container handling vehicle <NUM>, it is the outermost part of the cantilever <NUM> which defines the third side surface <NUM> since it extends over a grid cell <NUM> and blocks other container handling vehicles from occupying that cell <NUM>. The fourth side surface <NUM> thus also extends from the edge of the cantilever <NUM> to the second side surface <NUM>. Three sensors <NUM> of the proximity sensor system <NUM> are exemplified as each being arranged in an upper corner of the second side surface <NUM> and third side surface <NUM> of the exterior housing of the container handling vehicle <NUM>, whilst a fourth sensor <NUM> is arranged near the edge of the cantilever <NUM>. As will be apparent, similar sensors <NUM> may be found on the sides <NUM> and <NUM> not fully shown in <FIG>, with sensors <NUM> also being arranged in the outermost edge of the cantilever <NUM> facing the positive first direction X+. Advantageously, the sensors <NUM> are arranged near the boundary of a side surface <NUM>,<NUM>,<NUM>,<NUM> as this allows them to detect the presence of another container handling vehicle moving parallel to said side surface <NUM>,<NUM>,<NUM>,<NUM>.

<FIG> illustrates another type of container handling vehicle <NUM> with a contact area against the rail system <NUM> which has a horizontal extension that is equal to the lateral area defined by a grid column <NUM> or grid cell <NUM>. The container handling vehicle <NUM> also comprises a protruding section <NUM>, as shown in <FIG>, which extends laterally beyond the contact area of the container handling vehicle <NUM> and, when the container handling vehicle <NUM> is positioned above a grid cell <NUM>, into a neighbouring grid cell <NUM>. The container handling vehicle <NUM> comprises a vehicle body 301a and drive means 301b for driving in the first direction X, and drive means 301c for driving in the second direction Y. Though the drive means 301c in the second direction Y are not shown in the side view of <FIG>, they can be seen in <FIG> and are similarly arranged as the drive means 301b in the first direction X.

However, the protruding section <NUM> does not prevent another container handling vehicle <NUM> from travelling over the neighbouring grid cell <NUM>, i.e. the grid cell <NUM> into which the protruding section <NUM> of the first vehicle extends. To achieve this, the container handling vehicles <NUM> each comprise a recessed section <NUM> arranged opposite the protruding section <NUM>, which recessed section <NUM> is capable of accommodating the protruding sections <NUM> of other vehicles <NUM> when they pass over a neighbouring grid cell <NUM>. The recessed section <NUM> may have a shape which is complementary to the shape of the protruding section <NUM> and may extend across the whole width or length of the container handling vehicle <NUM>, thus allowing vehicles <NUM> to pass each other over adjacent grid cells <NUM>. When the vehicles <NUM> operate on the rail system <NUM>, the recessed section <NUM> of each container handling vehicle <NUM> is capable of accommodating the protruding sections <NUM> of other container handling vehicles <NUM> when they pass over a neighbouring grid cell <NUM>, thus allowing container handling vehicles <NUM> to travel along neighbouring rows of grid cells, as illustrated in <FIG>.

The container handling vehicle <NUM> in <FIG> is included herein to illustrate that a protruding section <NUM> does not necessarily block access to an adjacent grid cell <NUM>, but that this is dependent on the shape of the container handling vehicle. It will therefore be apparent to the person skilled in the art that other variations of container handling vehicles with protrusions, or even without corresponding recesses, can be employed on a rail system <NUM> without the protrusions acting to block other container handling vehicles from accessing adjacent grid cells <NUM>. The difference between the container handling vehicles of <FIG> and <FIG> is therefore noteworthy, as both comprise parts extending over an adjacent grid cell <NUM>, yet only the container handling vehicle <NUM> of <FIG> has a side surface <NUM> defined from the edge of the cantilever <NUM>, contrary to the container handling vehicle <NUM> of <FIG>, where the first side surface <NUM> is not defined by the outermost edge of the protruding section <NUM>.

<FIG> illustrates another aspect of a container handling vehicle according to the invention, where a container handling vehicle <NUM> for container delivery, is shown in <FIG> and in relation to an automated storage and retrieval system <NUM> in <FIG>.

As <FIG> illustrates, the container delivery vehicle <NUM> is arranged for top-down receival of a storage container <NUM>, and therefore comprises a container carrier <NUM> arranged above a vehicle body 601a to receive a storage container <NUM>. The container delivery vehicle <NUM> comprises drive means 301b in first direction X, and drive means 301c in the second direction Y similar to that of the other aforementioned container handling vehicles <NUM>,<NUM>,<NUM>. Side surfaces <NUM>,<NUM>,<NUM>,<NUM> are defined for the container delivery vehicle <NUM> as for the other container handling vehicles, with the second <NUM> and fourth <NUM> side surfaces visible in <FIG>. Possible proximity sensor locations are also illustrated by reference <NUM>.

<FIG> illustrates a container delivery vehicle <NUM> operating on a rail system <NUM>' below the rail system <NUM> of a storage grid <NUM>. The delivery rail system <NUM> may be constructed in the same way or a similar way as the rail system <NUM> for the container handling vehicles <NUM>,<NUM>.

A container handling vehicle <NUM>, according to the embodiment of <FIG> is shown operating on the rail system <NUM> of the storage grid <NUM>. However, as will be apparent to the person skilled in the art, any kind of container handling vehicle <NUM>,<NUM>,<NUM> may be operated on the rail system <NUM> of the grid, for example according to the embodiments illustrated in <FIG>. The container handling vehicles <NUM> may thus lower storage containers down to container delivery vehicles <NUM> operated on the lower rail system <NUM>'. The container delivery vehicles <NUM> are typically arranged for delivery of storage containers <NUM> to an access point (not shown) at the periphery of the rail system <NUM>, where the storage containers <NUM> may be picked. Though not illustrated herein, the lower rail system <NUM>' typically comprises a multitude of container delivery vehicles <NUM>, and as they move between cells below port columns and access points on the periphery of the lower rail system <NUM>', problems of congestion and queuing may arise. Thus, the invention is advantageously applied to rail systems <NUM>' with container delivery vehicles <NUM> in a similar manner as for container handling vehicles <NUM>,<NUM>,<NUM> of a rail system <NUM> of a grid <NUM> <FIG> illustrates the projection <NUM> on a rail system, side surfaces <NUM>,<NUM>,<NUM>,<NUM> and rectangular cross sections <NUM> formed by several different examples of container handling vehicles. The rectangular cross section <NUM> labelled A could for example be from the container handling vehicle <NUM> of <FIG>, <FIG> or <FIG>, as the rectangular cross section <NUM> formed by its side surfaces is equal to the lateral area defined by a grid cell <NUM>. The rectangular cross section <NUM> labelled B is equal to the area defined by one (in the X direction) times one and a half (in the Y direction) grid cells <NUM>, and could for example be from a container handling vehicle with some similarities to the one illustrated in <FIG> but where one side wall of the vehicle is enlarged and takes up the area of half a grid cell <NUM>. The rectangular cross section <NUM> labelled C has an irregular projection and may be of a container handling vehicle <NUM> similar to that of the illustrative example of <FIG>. The rectangular cross section <NUM> labelled D, could for example be from the container handling vehicle <NUM> of <FIG> or <FIG>. However, it is conceivable that a container handling vehicle similar to that of <FIG>, with a lateral area corresponding to two grid cells <NUM> and capable of lifting two storage containers <NUM> simultaneously from adjacent grid cells <NUM> could also form a rectangular cross section <NUM> as that labelled D. As will be apparent to the person skilled in the art based on the disclosure of the invention herein, many more variations of container handling vehicles are conceivable.

<FIG> is a flow diagram schematically representing the steps of a method for operating an automated storage and retrieval system <NUM>. The method is typically initiated by a step <NUM> where the central control unit <NUM> detects a conflict over a grid cell <NUM> by two container handling vehicles <NUM>,<NUM>. A container handling vehicle on route to a target cell <NUM> is labelled as a first container handling vehicle <NUM>, and the container handling vehicle blocking access to the target cell <NUM> of the first container handling vehicle <NUM> is labelled as a second container handling vehicle <NUM>. A target cell may typically be a grid cell <NUM>, on rail system <NUM>,<NUM>', where a container handling vehicle has received a command from the central control unit <NUM> to move. In the next step, the first container handling vehicle <NUM> moves to a grid cell <NUM> adjacent to its target cell <NUM>, and receives a data signal from the central control unit <NUM> which it processes in its vehicle control unit <NUM>. The data signal comprises a command to activate the first container handling device's <NUM> proximity sensor system <NUM>, i.e. to start monitoring for another container handling vehicle in the direction of the target cell <NUM> which coincides with its the direction of travel. The data signal may also comprise specification of a predetermined distance D within which the first container handling vehicle <NUM> is to detect the second container handling vehicle <NUM> and to move into the target cell <NUM> once the second container handling <NUM> vehicle is beyond said distance D. Another data signal is transmitted from the central control unit <NUM> to the vehicle control unit <NUM> of the second container handling vehicle <NUM> commanding the second container handling vehicle <NUM> to move clear of the target cell <NUM>. In some aspects, the second container handling vehicle <NUM> may have already received a command to move clear of the target cell <NUM> before first container handling vehicle <NUM> receives a command to activate its proximity sensor system <NUM> and move, but the second container handling vehicle <NUM> has not yet moved, for example because it is busy lowering or lifting storage containers <NUM>. Thus the data signal from the central control unit to the first container handling vehicle <NUM> is illustrated by step <NUM>, and the activation of its proximity sensor system <NUM> by step <NUM>. In any case, the second container handling vehicle <NUM> moves away from its blocking position of the target cell <NUM>, as illustrated by step <NUM>. The vehicle control unit <NUM> of the first container handling vehicle <NUM> continuously monitors data from its proximity sensor system <NUM>, and upon the predetermined distance D being free from an object i.e. the second container handling vehicle <NUM>, the vehicle control unit <NUM> controls the first container handling vehicle <NUM> to move into the target cell <NUM> represented by step <NUM>. Depending on the direction of travel of the second container handling vehicle <NUM> relative to the first container handling vehicle <NUM>, the vehicle control unit <NUM> may continue to monitor whether the second container handling vehicle <NUM> is within the predetermined distance during movement of the first container handling vehicle <NUM>.

In the following, with reference to <FIG>, various steps of methods of operating an automated storage and retrieval system are exemplified in accordance with the invention. To illustrate these, a schematic rail system and two of one type of container handling vehicle <NUM>,<NUM> are used throughout <FIG>. The container handling vehicles <NUM>,<NUM> exemplified in <FIG> have a rectangular cross section <NUM> equal to one by one and a half grid columns (i.e. 1x1. <NUM>), as described in relation to portion B of <FIG>, and comprise a container receiving space <NUM> arranged to one side of the vehicle body. The container handling vehicles <NUM>,<NUM> may further comprise a proximity sensor system <NUM> such as that shown in <FIG>, but only activated sensors <NUM> are illustrated in <FIG>, i.e. sensors which monitor whether the second container handling vehicle <NUM> is within the predetermined distance D. However, the remaining sensors <NUM> may also be active during execution of the method.

<FIG> is a schematic top view of a rail system <NUM>, illustrating steps of a method where a first container handling vehicle <NUM> and a second container handling vehicle <NUM> are located on adjacent grid cells <NUM> when the method is initiated, as illustrated in portion A by the central control unit <NUM> transmitting a data signal to each of the container handling vehicles <NUM>,<NUM>. The second container vehicle <NUM> is illustrated as covering the entire target cell <NUM>, and is oriented such that its container receiving space <NUM> is also over the target cell <NUM>. Such a starting point as shown in <FIG>, may be common around ports, where the target cell <NUM> is located over a port column <NUM>,<NUM> through which storage containers <NUM> are dropped off and picked up. The first container handling vehicle <NUM> thus activates it proximity sensor system <NUM> as represented by the black dots <NUM> and continuously monitors the predetermined distance D as it moves into the target cell <NUM> to avoid collision with the second container handling vehicle <NUM>.

In portion B of <FIG>, the second container handling vehicle <NUM> is moving, as illustrated by the arrow and the position of the vehicle <NUM> across two grid cells <NUM>. The proximity sensor system <NUM> of the first container handling vehicle <NUM> is monitoring the presence of the second container handling vehicle <NUM> within the predetermined distance D, which may typically be set to <NUM> meters when the container handling vehicles <NUM>,<NUM> move in parallel.

Portion C of <FIG> thus illustrates first container handling vehicle <NUM> after it has detected that there is no second container handling vehicle <NUM> within the predetermined distance D, and both container handling vehicles <NUM>,<NUM> are moving across the rail system <NUM>. The first container handling vehicle's <NUM> proximity sensor system <NUM> may thus continuously monitor in the first positive direction X+ in order to avoid a collision, for example if the second container handling vehicle <NUM> should unexpectedly stop. Note that the second container handling vehicle <NUM> is partially within the target cell <NUM> when the first container handling vehicle <NUM> starts to move.

Portion D of <FIG> illustrates the end result of the method, where the first container handling vehicle <NUM> has moved over the target cell <NUM> and the second container handling vehicle <NUM> has moved to a new position on the rail system <NUM>. Typically, the new position for the second container handling vehicle <NUM> may be related to a new task such as retrieving or depositing a storage container <NUM> somewhere in the grid <NUM>.

<FIG> is a schematic top view of a rail system <NUM>, illustrating steps of a method where a first container handling vehicle <NUM> is located on a grid cell <NUM> adjacent to its target cell <NUM> which is unoccupied, yet the second container handling vehicle <NUM> is blocking access to the target cell <NUM> due to size and thus the rectangular cross section <NUM> of the first container handling vehicle <NUM>. The steps illustrated by the portions A-B in <FIG> are essentially the same as for the steps in <FIG>, however only the sensor <NUM> in the corner of the first container handling vehicle <NUM> which is closest to the second container handling vehicle <NUM> is required to be activated. The central control unit <NUM> may transmit the direction of travel and position for the second container handling vehicle <NUM>, whereupon the vehicle control unit <NUM> of the first container handling vehicle <NUM> may determine which sensors are required to monitor for the presence of the second container handling vehicle <NUM> within the predetermined distance. Alternatively, the central control unit <NUM> may give a direct command to the first container handling vehicle <NUM> regarding which sensors are to be activated.

<FIG> is a schematic top view of a rail system <NUM>, illustrating steps of a method where a first container handling vehicle <NUM> is located on a grid cell <NUM> adjacent to its target cell <NUM> which is partially occupied by a second container handling vehicle <NUM>, due to the orientations of the two vehicles <NUM>,<NUM> on the rail system <NUM> being different. The steps illustrated by the potions A-B in <FIG> are essentially the same as for the steps in <FIG>,.

<FIG> is a schematic top view of a rail system <NUM>, illustrating steps of a method where a first container handling vehicle <NUM> and a second container handling vehicle <NUM> are initially located on adjacent grid cells <NUM> similarly to the starting point of the method in <FIG>. Contrary to the steps of <FIG> however, the second container handling vehicle <NUM> moves in a direction orthogonal to the direction in which the first container handling vehicle <NUM> is to travel, as illustrated in Portion B of <FIG>. Thus, the first container handling vehicle's <NUM> sensor <NUM> arranged in the corner of the direction of travel of the second container handling vehicle <NUM> is activated. Furthermore, the predetermined distance D which the proximity sensor system <NUM> is to detect the second container handling vehicle <NUM> may be less than <NUM> (two) meters, for example <NUM> (ten) centimeters, as it is only required to detect when the second container handling vehicle <NUM> has passed its corner. The vehicle control unit <NUM> of the first container handling vehicle <NUM> may receive information from the central control unit <NUM> regarding the predetermined distance D and which sensor to activate, or the vehicle control unit <NUM> may determine the distance and which sensors to activate by receiving information regarding the direction of travel of the second container handling vehicle <NUM>. Once the sensor <NUM> of the first container handling vehicle <NUM> has detected that there is no obstruction, said container handling vehicle <NUM> can move into the target cell <NUM>. In a prior art execution of the method illustrated in <FIG>, the central control unit <NUM> could not know that the target cell <NUM> was free until the second container handling vehicle <NUM> had moved at least to the position illustrated in portion D of <FIG>, thus leaving the first container handling device <NUM> to await moving in to the target cell <NUM> for an excessive amount of time. The steps of the method in <FIG> thus clearly illustrate the time saving aspects of the invention.

The predetermined distance D may be dynamically adapted to the speed the container handling vehicles are moving in. The container handling vehicles are set to have a default predetermined distance D for a given speed. The container handling vehicles themselves will adapt the distance D to the speed they are traveling in.

In the preceding description, various aspects of a method of operating an automated storage and retrieval system, and an automated storage and retrieval system according to the invention have been described with reference to the illustrative embodiment.

However, this description is not intended to be construed in a limiting sense. Various modifications and variations of the illustrative embodiment, as well as other embodiments of the system and the method which are apparent to persons skilled in the art, are deemed to lie within the scope of the present invention as defined by the following claims.

Claim 1:
A method of operating an automated storage and retrieval system (<NUM>), the automated storage and retrieval system (<NUM>) comprising:
- a rail system (<NUM>,<NUM>') comprising a first set of parallel rails (<NUM>) arranged in a horizontal plane (P,P') and extending in a first direction (X), and a second set of parallel rails (<NUM>) arranged in the horizontal plane (P,P') and extending in a second direction (Y) which is orthogonal to the first direction (X), which first and second sets of rails (<NUM>, <NUM>) form a grid pattern in the horizontal plane (P,P') comprising a plurality of adjacent grid cells (<NUM>),
- a central control unit (<NUM>) configured to receive, transmit and process data signals of a plurality of container handling vehicles (<NUM>,<NUM>) for handling storage containers (<NUM>) of the automated storage and retrieval system (<NUM>),
each container handling vehicle (<NUM>,<NUM>) comprising
a vehicle body (101a, 201a, 301a, 601a)
a wheel assembly (101b, 101c, 201b, 201c, 301b, 301c, 601b, 601c) provided on the vehicle body (101a, 201a, 301a, 601a), the wheel assembly (101b, 101c, 201b, 201c, 301b, 301c, 601b, 601c) being configured to move the vehicle (<NUM>,<NUM>) along the rail system (<NUM>,<NUM>') in both of the first direction (X) and the second direction (Y),
a vehicle control unit (<NUM>) configured to receive data signals from, transmit data signals to and process data signals of the central control unit (<NUM>), and
a proximity sensor system (<NUM>) configured to detect another container handling vehicle (<NUM>,<NUM>) of said plurality of container handling vehicles (<NUM>,<NUM>) and determine whether or not it is within a predetermined distance (D),
wherein the method comprises:
- detecting with the central control unit (<NUM>) that access of a first container handling vehicle (<NUM>) to a target cell (<NUM>), which is one of the plurality of grid cells, is blocked by a second container handling vehicle (<NUM>),
- transmitting a data signal (<NUM>) from the central control unit (<NUM>) to the vehicle control unit (<NUM>) of the first container handling vehicle (<NUM>) commanding the first container handling vehicle (<NUM>) to move into the target cell (<NUM>) when the second container handling vehicle (<NUM>) is beyond said predetermined distance (D).