Patent Description:
Each prior art container handling vehicle <NUM>,<NUM> also comprises a lifting device (not shown) 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 one or more gripping / engaging devices which are adapted to engage a storage container <NUM>, and which gripping / engaging devices can be lowered from the vehicle <NUM>,<NUM> so that the position of the gripping / engaging devices with respect to the vehicle <NUM>,<NUM> can be adjusted in a third direction Z which is orthogonal the first direction X and the second direction Y. Parts of the gripping device of the container handling vehicle <NUM> are shown in <FIG> indicated with reference number <NUM>. The gripping device of the container handling device <NUM> is located within the vehicle body 301a in <FIG>.

The storage volume of the framework structure <NUM> has often been referred to as a grid <NUM>, where the possible storage positions within this grid are referred to as storage cells. Each storage column may be identified by a position in an X- and Y-direction, while each storage cell may be identified by a container number in the X-, Y and Z-direction.

The central cavity container handling vehicles <NUM> shown in <FIG> may have a footprint that covers an area with dimensions in the X and Y directions which is generally equal to the lateral extent of a storage column <NUM>, e.g. as is described in <CIT>.

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

In <FIG>, columns <NUM> and <NUM> are such special-purpose columns used by the container handling vehicles <NUM>,<NUM> to drop off and/or pick up storage containers <NUM> so that they can be transported to an access station (not shown) where the storage containers <NUM> can be accessed from outside of the framework structure <NUM> or transferred out of or into the framework structure <NUM> Within the art, such a location is normally referred to as a 'port' and the column in which the port is located may be referred to as a 'port column' <NUM>,<NUM>.

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 not removed from the automated storage and retrieval system <NUM>, but are returned into the framework structure <NUM> again once accessed. A port can also be used for transferring storage containers to another storage facility (e.g. to another framework structure or to another automated storage and retrieval system), to a transport vehicle (e.g. a train or a lorry), or to a production facility.

When a storage container <NUM> is to be stored in one of the columns <NUM>, one of the container handling vehicles <NUM>,<NUM> is instructed to pick up the storage container <NUM> from the pick-up port column <NUM> and transport it to a 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>,<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.

<CIT> describes a system for controlling movement of plurality of container handling vehicles where the container handling vehicles transport storage containers, store and retrieve storage containers into/from storage columns.

The framework structure <NUM> and the rail system <NUM> is specified and constructed to allow operation of the plurality of container handling vehicles <NUM>, <NUM> at full speed and acceleration. However, after installation or during operation it may be determined that some areas of the framework structure <NUM> and/or the rail system <NUM> are outside specifications. This may lead to operational errors of the container handling vehicles <NUM>, <NUM>. The operational errors may lead to system stop or crash of container handling vehicles <NUM>, <NUM>. In order to be safe and avoid the operation errors, the speed and/or acceleration is reduced for all container handling vehicles <NUM>, <NUM> on the rail system <NUM>. This leads to a considerably reduced capacity of the automated storage and retrieval system <NUM>.

In <CIT> an access control method is utilized in order to guarantee the structural integrity of a grid-like storage facility. The access control method limits the number of transporting devices in a constraint area by granting or withholding clearance to each transporting device to traverse the constraint area. It does not address operational errors of the transporting vehicles.

<CIT>, which the EPO identified in the examination procedure as the closest prior art, describes, according to a machine translation, a conveying system which includes a track and a suspended traveling vehicle. Below the track, a processing device, a load port, a storage device, etc. are arranged. The storage device is a device, such as a hanging shelf, for temporarily storing FOUPs and the like until the processing device and the load port become available when they are in use. The suspended traveling cart includes a transfer device, a holding device, and a storage container below the base portion. The transfer device includes a mechanism (such as a hoist) for moving the storage container vertically, and a mechanism (such as an arm mechanism that can be extended and retracted horizontally) for moving the storage container horizontally. When semiconductor wafers are accommodated inside the container, it is possible to move the suspended traveling carriage at high speed while reducing the vibrations applied to the semiconductor wafers. Therefore, a higher maximum speed is set in the straight area than in the lattice area. In order to control the maximum speed, there is provided a detection means for detecting the current position of the suspended traveling cart, data recording the positions of the lattice area and the straight area, and a control means for controlling the speed of the suspended traveling cart. As a detection means, the suspended traveling vehicle may be configured to read an identifier (barcode, RFID, etc.) placed on the track. Then, if the current position of the suspended traveling vehicle is in the straight area, the traveling motor of the suspended traveling vehicle is controlled so as not to exceed the maximum speed set in the straight area. This control may be performed by a control device possessed by the suspended traveling cart, or by a control device that supervises the transport system, or by both of them working together.

<CIT> describes a controller to control movement of a plurality of transporting devices. The controller limits the loads imparted on a grid of pathways structure by the plurality of transporting devices to prevent non-safety-critical damage from excess loads and/or fatigue.

<CIT> describes systems and methods for specifying safety rules for robotic devices. A computing device can determine information about any actors present within a predetermined area of an environment. The computing device can determine a safety classification for the predetermined area based on the information. After determining the safety classification for the predetermined area, the computing device can provide a safety rule for operating within the predetermined area to a robotic device operating in the environment.

In view of the problems, the present invention aims to provide a system and method for the automated storage and retrieval system which avoids operational errors of the container handling vehicles in out of specification areas without significantly reducing the capacity of the automated storage and retrieval system.

The present invention is set forth and characterized in the independent claims <NUM>, <NUM> and <NUM>, while the dependent claims describe other characteristics of the invention.

In one aspect, the invention is related to a method for controlling movement of a plurality of container handling vehicles on a rail system arranged at least partially across a top of framework structure of an automated storage and retrieval system, on which rail system the plurality of container handling vehicles are operable to raise storage containers from, and lower storage containers into, storage columns arranged in rows between upright members and horizontal members of the framework structure, and also to transport the storage containers above the storage columns. The following steps are performed by a central operational controller which is in communication with a local controller in each container handling vehicle. Receiving data relating to a subsection of the rail system, the data comprising a container handling vehicle movement threshold for the subsection. Instructing a container handling vehicle to follow a path which takes in at least a part of the subsection. Instructing the container handling vehicle to reduce speed and/or acceleration such that the movement of the container handling vehicle within the is below the container handling vehicle movement threshold of the subsection. Driving the container handling vehicle at slower speed/acceleration allows the control system to better handle operational errors. In this way, system stops or crashes can be avoided.

In an embodiment, the method may further comprise, prior to the step of instructing the container handling vehicle to reduce speed and/or acceleration, a step of determining that a current movement of the container handling vehicle exceeds the container handling vehicle movement threshold of the subsection. The central operation controller may then only instruct to reduce speed and/or acceleration when the current movement of the container handling vehicle exceeds the container handling vehicle movement threshold of the subsection. The number of instructions over the communication channel is therefore reduced and unwanted additional load on the communication channels is avoided.

In an embodiment, determining that the container handling vehicle exceeds the container handling vehicle movement threshold may further comprise classifying the container handling vehicle according to a container handling vehicle classification, and determining, based on the container handling vehicle classification, that the container handling vehicle exceeds the container handling vehicle movement threshold. The container handling vehicle classification comprises a default speed and/or acceleration of the container handling vehicle.

In an embodiment, determining that the container handling vehicle exceeds the container handling vehicle movement threshold may further comprise receiving data of the weight of a storage container transported by the container handling vehicle, and determining, based on the weight of the storage container and the container handling classification, that the container handling vehicle exceeds the container handling vehicle movement threshold.

In an embodiment, determining that the container handling vehicle exceeds the container handling vehicle movement threshold may further comprise receiving historical movement data of the container handling vehicle, and determining, based on the historical movement data of the container handling vehicle, that the container handling vehicle exceeds the container handling vehicle movement threshold.

In an embodiment, the method may further comprise instructing the container handling vehicle to revert to a default speed and/or acceleration when the container handling vehicle is leaving and/or about to leave the subsection.

In an embodiment, the container handling vehicle movement threshold sets a maximum speed of the container handling vehicle.

In an embodiment, the container handling vehicle movement threshold sets a maximum acceleration of the container handling vehicle.

According to the invention to which this European patent relates, the container handling vehicle movement threshold sets a maximum linear momentum of the container handling vehicle.

In an embodiment, the method may further comprise determining, using a rail inspection vehicle traversing the rail system, the container handling vehicle movement threshold for the subsection of the rail system. The container handling vehicle movement threshold may be determined based on detected vertical and/or horizontal movement of the rail inspection vehicle due to movement in the rail system above a fault threshold. The container handling vehicle movement threshold may be determined based on detected changes in horizontal movement of the rail inspection vehicle due to a change in a condition of the rail system. The container handling vehicle movement threshold may also be determined based on visually detected faults in the rail system using the rail inspection vehicle or other method.

In an embodiment, the method may further comprise determining the container handling vehicle movement threshold for the subsection based on a reduced mechanical stability in the subsection of the of rail system compared to a mechanical stability of the rail system outside the subsection.

In an embodiment, the method may further comprise determining the container handling vehicle movement threshold for the subsection based on a displacement of the of rail system in the subsection in relation to the rail system outside the subsection.

In an embodiment, the method may further comprise determining the container handling vehicle movement threshold for the subsection based on a reduced friction in the subsection of the rail system compared to a friction of the rail system outside the subsection.

In an embodiment, the method may further comprise determining the container handling vehicle movement threshold for the subsection based on different environmental conditions in the subsection of the rail system than in the rail system outside the subsection.

In an embodiment, the method may further comprise transmitting the container handling vehicle movement threshold for the subsection to the local controller in the container handling vehicle, and performing, using the local controller in the container handling vehicle, the step of instructing the container handling vehicle to reduce speed and/or acceleration such that the movement of the container handling vehicle within the subsection is below the container handling vehicle movement threshold of the subsection.

In a second aspect, the invention concerns a system comprising a rail system arranged at least partially across a top of framework structure of an automated storage and retrieval system, a plurality of container handling vehicles operating on the rail system to raise storage containers from, and lower storage containers into, storage columns arranged in rows between upright members and horizontal members of the framework structure, and also to transport the storage containers above the storage columns, each container handling vehicle comprising a local controller adapted to control movements of the container handling vehicle, and a central operational controller in communication with the local controller in each container handling vehicle. The central operational controller is adapted to perform receiving data relating to a subsection of the rail system, the data comprising a container handling vehicle movement threshold for the subsection, instructing a container handling vehicle to follow a path which takes in at least a part of the subsection, and instructing the container handling vehicle to reduce speed and/or acceleration such that the movement of the container handling vehicle within the subsection is below the container handling vehicle movement threshold of the subsection. Driving the container handling vehicle at slower speed/acceleration allows the control system to better handle operational errors. In this way, system stops or crashes can be avoided.

In an embodiment of the system, the central operational controller may be further adapted to, prior to instructing the container handling vehicle to reduce speed and/or acceleration, determining that a current movement of the container handling vehicle exceeds the container handling vehicle movement threshold of the subsection. The central operation controller may then only instruct to reduce speed and/or acceleration when the current movement of the container handling vehicle exceeds the container handling vehicle movement threshold of the subsection. The number of instructions over the communication channel is therefore reduced and unwanted additional load on the communication channels is avoided.

In an embodiment of the system, determining that the container handling vehicle exceeds the container handling vehicle movement threshold may further comprise classifying the container handling vehicle according to a container handling vehicle classification, and determining, based on the container handling vehicle classification, that the container handling vehicle exceeds the container handling vehicle movement threshold. The container handling vehicle classification comprises a default speed and/or acceleration of the container handling vehicle.

In an embodiment of the system, determining that the container handling vehicle exceeds the container handling vehicle movement threshold may further comprise receiving data of the weight of a storage container transported by the container handling vehicle, and determining, based on the weight of the storage container and the container handling classification, that the container handling vehicle exceeds the container handling vehicle movement threshold.

In an embodiment of the system, determining that the container handling vehicle exceeds the container handling vehicle movement threshold may further comprise receiving historical movement data of the container handling vehicle, and determining, based on the historical movement data of the container handling vehicle, that the container handling vehicle exceeds the container handling vehicle movement threshold.

In an embodiment of the system, the central operational controller may be further adapted to instructing the container handling vehicle to revert to a default speed and/or acceleration when the container handling vehicle is leaving and/or about to leave the subsection.

In an embodiment of the system, the container handling vehicle movement threshold sets a maximum speed of the container handling vehicle.

In an embodiment of the system, the container handling vehicle movement threshold sets a maximum acceleration of the container handling vehicle.

In an embodiment of the system, the system may further comprise a rail inspection vehicle adapted to traverse the rail system, and is adapted to determining, using the rail inspection vehicle, the container handling vehicle movement threshold for the subsection of the rail system. The container handling vehicle movement threshold may be determined based on detected vertical and/or horizontal movement of the rail inspection vehicle due to movement in the rail system above a fault threshold. The container handling vehicle movement threshold may be determined based on detected changes in horizontal movement of the rail inspection vehicle due to a change in a condition of the rail system. The container handling vehicle movement threshold may also be determined based on visually detected faults in the rail system using the rail inspection vehicle or other method.

In an embodiment of the system, the container handling vehicle movement threshold for the subsection may be determined based on a reduced mechanical stability in the subsection of the of rail system compared to a mechanical stability of the rail system outside the subsection.

In an embodiment of the system, the container handling vehicle movement threshold for the subsection may be determined based on a displacement of the of rail system in the subsection in relation to the rail system outside the subsection.

In an embodiment of the system, the container handling vehicle movement threshold for the subsection may be determined based on a reduced friction in the subsection of the rail system compared to a friction of the rail system outside the subsection.

In an embodiment of the system, the container handling vehicle movement threshold for the subsection may be determined based on different environmental conditions in the subsection of the rail system than in the rail system outside the subsection.

In an embodiment of the system, the central operational controller may be further adapted to transmitting the container handling vehicle movement threshold for the subsection to the local controller in the container handling vehicle, and the local controller in the container handling vehicle may be further adapted to instructing the container handling vehicle to reduce speed and/or acceleration such that the movement of the container handling vehicle within the subsection is below the container handling vehicle movement threshold of the subsection.

In a third aspect the invention is directed to a computer program product for a central operational controller in a system comprising a plurality of container handling vehicles on a rail system arranged at least partially across a top of framework structure of an automated storage and retrieval system, on which rail system the plurality of container handling vehicles are operable to raise storage containers from, and lower storage containers into, storage columns arranged in rows between upright members and horizontal members of the framework structure, and also to transport the storage containers above the storage columns, each container handling vehicle comprising a local controller adapted to control movements of the container handling vehicle, and the central operational controller is in communication with the local controller in each container handling vehicle, the computer program product comprises instructions that when executed on the central operational controller performs the method according to the first aspect of the invention.

One embodiment of the automated storage and retrieval system according to the invention will now be discussed in more detail with reference to <FIG>, <FIG> and <FIG>.

<FIG> is a schematic overview of a part of the rail system <NUM>, where it is shown container handling vehicles <NUM>, <NUM> instructed to follow paths <NUM>, <NUM>, respectively, taking in at least a part of two subsections 401a, 401b. The two subsections 401a, 401b are for simplicity defined in terms of integer units of storage columns but may also be defined by fractional units of storage columns, or by other suitable coordinates. An exemplary third subsection 401c is defined by one and a half storage column in the Y-direction two storage columns in the X-direction. The subsections 401a, 401b, 401c are areas of the rail system <NUM> where there is a higher likelihood for operational errors of the container handling vehicles <NUM>, 301compared to the remaining areas of the rail system <NUM>. Operational errors may include that the container handling vehicles <NUM>, <NUM> are incapable of stopping in the correct position, or the container handling vehicles <NUM>, <NUM> detects that sensor data does not correlate with expected data. The operation errors may lead to a system stop, or worse, a crash between container handling vehicles.

Driving the container handling vehicle <NUM>, <NUM> at slower speed/acceleration allows the control system <NUM> to better handle operational errors, in this way, system stops or crashes can be avoided.

Each container handling vehicle <NUM>, <NUM> comprises a local controller adapted to control movements of the container handling vehicle <NUM>, <NUM>. Controlling the movements of the container handling vehicle <NUM>, <NUM> includes controlling electric motors driving the driving means, such as wheels, of the container handling vehicle. The container handling vehicle <NUM>, <NUM> usually run at full speed and acceleration. The full speed and acceleration of the container handling vehicle <NUM>, <NUM> is defined by the construction of the electric motors driving the driving means of the container handling vehicle. Depending on the type of the electric motor, the speed and acceleration of the electric motor may be controlled by adjusting frequency and or voltage of the power supplied to the electric motor. In real life electric motors, while being manufactured to a certain specification, there will be deviations from the specification in manufacture, thus different electric motors supplied with identical power may move at different speeds. The actual speed of the container handling vehicle <NUM>, <NUM> may vary within the deviations from the specifications. Hence, the speed and acceleration of the container handling vehicle <NUM>, <NUM> referred herein is not the true speed and acceleration of the container handling vehicle <NUM>, <NUM>, rather it is the speed and acceleration obtained by each the container handling vehicle <NUM>, <NUM> at a given power supplied to the electric motors. Furthermore, a reduced speed and acceleration is obtained by supplying the electric motors of the container handling vehicles <NUM>, <NUM> with a fraction of the power supplied to the motors at full speed and acceleration. The term acceleration should be seen to also include negative acceleration, e.g. deceleration.

The system is provided with a central operational controller <NUM> in communication with the local controller in each container handling vehicle <NUM>, <NUM>. The communication between the local controller and the central operational controller may be any suitable wired or wireless communication technology. The central operational controller <NUM> is also in communication with the control system <NUM> using any suitable wired or wireless communication technology.

With additional reference to <FIG> illustrating a method of controlling movement of the container handling vehicle <NUM>, <NUM>. The central operational controller <NUM> receives data relating to a subsection 401a, 401b of the rail system <NUM>, the data comprises a container handling vehicle movement threshold for the subsection 401a, 401b. The central operation controller <NUM> may receive the container handling vehicle movement threshold from the control system <NUM>. The container handling vehicle movement threshold may set at least one of a maximum speed of the container handling vehicle <NUM>, <NUM>, and a maximum acceleration of the container handling vehicle <NUM>, <NUM>. The container handling vehicle movement threshold sets a maximum linear momentum of the container handling vehicle <NUM>, <NUM>.

The central operational controller <NUM> instructs the container handling vehicle <NUM>, <NUM> to follow a path <NUM>, <NUM> on the rail system <NUM>. The central operation controller <NUM> may receive data from the control system <NUM> related to columns on the rail system <NUM> that requires a container handling vehicle <NUM>, <NUM> to pick up a storage bin, and to columns where the storage bin should be dropped off. The central operational controller <NUM> may instruct the container handling vehicle to follow the path <NUM>, <NUM> by step-by-step instructions. The central operational controller <NUM> may instruct the container handling vehicle <NUM>, <NUM> to follow a path <NUM>, <NUM> which takes in at least a part of the subsection 401a, 401b. Furthermore, the central operational controller <NUM> instructs the container handling vehicle <NUM>, <NUM> to reduce speed and/or acceleration such that the movement of the container handling vehicle within the subsection 401a, 401b is below the container handling vehicle movement threshold of the subsection 401a, 401b. While instructing the container handling vehicle to follow a path and instructing the container handling vehicle to reduce speed and/or acceleration is described in separate steps, both instructions may be part of a joint step-by-step instruction from the central operational controller to the container handling vehicle. In one embodiment, some of the steps may be performed by the local controller in each container handling vehicle <NUM>, <NUM> under the control of the central operational controller <NUM>. In one example, the container handling vehicle movement threshold of the subsection 401a, 401b may be transmitted to and stored in the local controller. The local controller of the container handling vehicle <NUM>, <NUM> may then make the determination to reduce speed and/or acceleration on its own behalf.

The central operational controller <NUM> having knowledge of the path <NUM>, <NUM> of the container handling vehicle may instruct the container handling vehicle <NUM>, <NUM> prior to the container handling entering the subsection 401a, 401b, such that the container vehicle <NUM>, <NUM> has reduced the speed prior to entering the subsection. The central operational controller <NUM> having knowledge of the container handling vehicle <NUM>, <NUM> may also predict the latest point in time when the instructions needs to be effectuated in order for the container handling vehicle to have reduced its speed below the vehicle movement threshold at the time a side of the container handling vehicle crosses a border of the subsection 401a, 401b.

In another embodiment, the central operational controller <NUM> having knowledge of the path <NUM>, <NUM> of the container handling vehicle <NUM>, <NUM> may instruct the container handling vehicle <NUM>, <NUM> to reduce the speed and/or acceleration below the vehicle movement threshold once a side of the container handling vehicle <NUM>, <NUM> crosses a border of the subsection 401a, 401b. Instructions to the container handling vehicle <NUM>, <NUM> to reduce speed and/or acceleration may be part of the instructions to the container handling vehicle <NUM>, <NUM> to follow the path <NUM>, <NUM>.

When the container handling vehicle <NUM>, <NUM> is leaving the subsection 401a, 401b, the central operation controller instructs the container handling vehicle <NUM>, <NUM> to revert to a default speed and/or acceleration. The default speed and/or acceleration would typically be the maximum speed and/or acceleration of the container handling device <NUM>, <NUM>. The instructions to the container handling vehicle <NUM>, <NUM> to revert to a default speed and/or acceleration may be part of the instructions to the container handling vehicle <NUM>, <NUM> to follow the path <NUM>, <NUM>. The point in time when the container handling vehicle <NUM>, <NUM> is leaving the subsection 401a, 401b may depend on the specific requirements of the system. However, one suitable point in time may be when a first side of the container handling vehicle <NUM>, <NUM> crosses a border of the subsection 401a, 401b on its way out of the subsection 401a, 401b. Another suitable point in time may be when the container handling vehicle <NUM>, <NUM> has completely left the subsection 401a, 401b.

In some instances, for example when movement of the container handling vehicle <NUM>, <NUM> outside the subsection 401a, 401b is below the container handling movement threshold of the subsection 401a, 401b, the instruction to the container handling vehicle <NUM>, <NUM> is redundant. In an automated storage and retrieval systems <NUM> having many container handling vehicles <NUM>, <NUM> redundant messages may cause an unwanted additional load on the communication channels. With additional reference to <FIG> illustrating one embodiment of the invention, the central operational controller <NUM> is further adapted to, prior to instructing the container handling vehicle <NUM>, <NUM> to reduce speed and/or acceleration, determining that a current movement of the container handling vehicle exceeds the container handling vehicle movement threshold of the subsection 401a, 401b. The central operation controller <NUM> may then only instruct to reduce speed and/or acceleration when the current movement of the container handling vehicle exceeds the container handling vehicle movement threshold of the subsection 401a, 401b.

Determining that a current movement of the container handling vehicle exceeds the container handling vehicle movement threshold of the subsection 401a, 401b, may also be directional for the vehicles themselves, for example, due to a non-symmetry in the container handling vehicle <NUM>, <NUM> and its engagement with the rail system <NUM>. , the container handling vehicle <NUM> might have different length to width thresholds due to asymmetry in the internal arrangement of the components and the resultant asymmetric weight distribution and wheelbase. The container handling vehicle <NUM> are usually arranged as left or right-handed cantilevers. The asymmetry in handling will depend on the load being carried in the container and the balance with respect to the motor weight.

In one embodiment, determining that the container handling vehicle exceeds the container handling vehicle movement may be based on classifying the container handling vehicle <NUM>, <NUM> according to a container handling vehicle classification. The container handling vehicle classification may be different types of container handling vehicles, such as cantilever type <NUM> or cavity type <NUM>, or versions of the same type of container handling vehicles having different specifications, such as different electric motors, different weights, different wheels etc. The container handling vehicle classification comprises a default speed and/or acceleration of the container handling vehicle, e.g. a measured average maximum speed and/or acceleration, or an expected maximum speed and/or acceleration based on the specifications of the container handling vehicles in the classification. The determination that the container handling vehicle exceeds the container vehicle movement threshold in the subsection 401a, 401b, is then simply based on determining the container handling vehicle classification.

In one embodiment, the central operation controller <NUM> may additionally receive data of the weight of a storage container transported by the container handling vehicle. The central operation controller <NUM> may receive the weight from weight sensors in the container handling vehicle or get information about the weight from the control system <NUM> that has knowledge about the content of the storage container. Determining that that the container handling vehicle exceeds the container handling vehicle movement threshold may then be based on the combined knowledge of the weight of the storage container and the container handling classification. Weight in a storage container may for example affect the handling of a cantilever type container handling device in larger degree than a cavity type container handling device.

In one embodiment, the central operation controller <NUM> may receive historical movement data of the container handling vehicle <NUM>, <NUM> and determining that the container handling vehicle <NUM>, <NUM> exceeds the container handling vehicle movement threshold based on the historical movement data. The determination may for example based on that the historical movement data show instability in the vehicle. Other historical movement data may include a number of derailings, a number of navigational errors, such as missed detections of rail crossings, etc..

<FIG> shows two different container handling vehicles <NUM>, <NUM> instructed to follow paths <NUM> and <NUM>, respectively. The central operational controller <NUM> have knowledge of footprints of the container handling vehicles on the rail system <NUM>. The exemplary container handling vehicles <NUM>, <NUM> illustrates exemplary sizes and footprints of container handling vehicles that may be put on the rail system <NUM>.

The container handling vehicle <NUM> shown in <FIG> may have a footprint which is generally equal to the lateral extent of one storage column <NUM>. The container handling vehicle <NUM> is instructed to follow a path <NUM> that crosses subsection 401a. As discussed above, the central operational controller <NUM> has knowledge of the path <NUM> and that the path crosses subsection 401a, and instructs the container handling vehicle <NUM> to reduce speed and/or acceleration such that the movement of the container handling vehicle <NUM> within the subsection 401a is below the container handling vehicle movement threshold of the subsection 401a. The instructions may in one example be effectuated when the first long side of the footprint of the container handling vehicle <NUM> crosses the perimeter of the subsection 401a. When the container handling vehicle <NUM> leaves the subsection 401a, the central operation controller instructs <NUM> the container handling vehicle <NUM> to revert to the default speed and/or acceleration and continue to follow the path <NUM>. In some embodiments, if the central operation controller <NUM> determine that the container handling vehicle <NUM> does not exceeds the container handling vehicle movement threshold of the subsection 401a both instructions are redundant and none of them are sent to the container handling vehicle <NUM>. When the container handling vehicle is about to enter the next subsection 401b, the instructions to reduce speed and/or acceleration may in one example be effectuated when the first short side of the footprint of the container handling vehicle <NUM> crosses the perimeter of the next subsection 401b.

The container handling vehicle <NUM> shown in <FIG> has a cantilever construction and may have a footprint approximately the lateral extent of two storage columns <NUM>. The container handling vehicle <NUM> is instructed to follow a path <NUM> that takes in subsection 401b. As discussed above, the central operational controller <NUM> has knowledge of the path <NUM> and that the path takes in subsection 401b, and instructs the container handling vehicle <NUM> to reduce speed and/or acceleration such that the movement of the container handling vehicle <NUM> within the subsection 401b is below the container handling vehicle movement threshold of the subsection 401b. The instructions may in one example be effectuated when the first short side of the footprint of the container handling vehicle <NUM> crosses the perimeter of the subsection 401b. In another example, when the container handling vehicle <NUM> enters the subsection 401b with the cantilever first, the instructions may be effectuated when the first wheels following the cantilever crosses the perimeter of the subsection 401b. When the container handling vehicle <NUM> leaves the subsection 401b, the central operation controller instructs <NUM> the container handling vehicle <NUM> to revert to the default speed and/or acceleration and continue to follow the path <NUM>. In this illustrated example, the instructions to revert to default speed and/or acceleration may be effectuated when the first or second long side of the footprint of the container handling vehicle <NUM> crosses the perimeter of the subsection 401b. In some embodiments, if the central operation controller <NUM> determine that the container handling vehicle <NUM> does not exceeds the container handling vehicle movement threshold of the subsection 401b both instructions are redundant and none of them are sent to the container handling vehicle <NUM>.

The higher likelihood for operational errors of the container handling vehicle <NUM>, <NUM> in the subsections 401a, 401b may be due to mechanical differences in the rail system <NUM> and/or the framework structure <NUM> that leads to reduced mechanical stability of the subsection 401a, 401b, or a displacement of the rail system <NUM> in the subsection 401a, 401b in relation to the rail system <NUM> outside the subsection 401a, 401b. The reduced mechanical stability and displacement of the rail system may stem from a floor not according to specifications, erroneous mounting of the framework structure, damages on framework structure, displacement of framework structure, a building that has moved etc..

Determining the container handling vehicle movement threshold for the subsection 401a, 401b may be based on reduced mechanical stability in the subsection 401a, 401b of the of rail system <NUM> compared to a mechanical stability of the rail system <NUM> outside the subsection 401a, 401b.

The higher likelihood for operational errors of the container handling vehicle <NUM>, <NUM> in the subsections 401a, 401b may also be due to reduced friction in the subsection 401a, 401b compared to a friction of the rail system <NUM> outside the subsection 401a, 401b, for example based on detection of oil, water, grease etc. on the rail system <NUM>.

Determining the container handling vehicle movement threshold for the subsection 401a, 401b may be based on a displacement of the of rail system <NUM> in the subsection 401a, 401b in relation to the rail system <NUM> outside the subsection 401a, 401b.

The higher likelihood for operational errors of the container handling vehicle <NUM>, <NUM> in the subsections 401a, 401b may also be due to a difference in environmental conditions in the subsection 401a, 401b, such as difference in temperature, air pressure, humidity, ambient gasses etc. Changes in environmental conditions may change the performance of the container handling vehicle <NUM>, <NUM>. In one example, water may condense on the wheels of a container handling vehicle <NUM>, <NUM> entering a cold zone from a warmer and more humid zone, which may cause reduced friction. In another example, the efficiency of the motor may change such that the speed of the container handling vehicle increases.

Determining the container handling vehicle movement threshold for the subsection 401a, 401b may be based on a reduced friction in the subsection 401a, 401b of the rail system <NUM> compared to a friction of the rail system <NUM> outside the subsection 401a, 401b.

The container handling vehicle movement threshold for the subsection 401a, 401b may be different in the first direction X and the second direction Y. The rails are closer together in the first direction X, that may make the structure stronger or more rigid than for the wider spacing between the junction points in the second direction Y.

The higher likelihood for operational errors of the container handling vehicle <NUM>, <NUM> in the subsections 401a, 401b may be determined by physical and/or visual inspection of the rail system <NUM> and the framework structure <NUM>. The physical and/or visual inspection may be performed manually.

In one embodiment, the system comprises a rail inspection vehicle adapted to traverse the rail system <NUM>. The system is adapted to determining, using the rail inspection vehicle, the container handling vehicle movement threshold for the subsection 401a, 401b of the rail system <NUM>.

The rail inspection vehicle may be provided with gyros, accelerometers, or other suitable movement sensor to determine vertical and/or horizontal movement of the rail inspection vehicle due to movement in the rail system while traversing the rail system <NUM>. The system may then determine the container handling vehicle movement threshold based on detected vertical and/or horizontal movement of the rail inspection vehicle due to movement in the rail system above a fault threshold.

In addition, or alternatively, the container handling vehicle movement threshold may be determined by the system based on detected changes in horizontal movement of the rail inspection vehicle due to a change in a condition of the rail system.

The rail inspection vehicle may be provided with an imaging device, such as a camera, in any suitable range of the electromagnetic spectrum, adapted to visually detect faults in the rail system while traversing the rail system <NUM>. The system may then determine the container handling vehicle movement threshold based on visually detected faults in the rail system <NUM>.

In the preceding description, various aspects of the container handling vehicle and the automated storage and retrieval system according to the invention have been described with reference to the illustrative embodiment. For purposes of explanation, specific numbers, systems and configurations were set forth in order to provide a thorough understanding of the system and its workings. However, this description is not intended to be construed in a limiting sense.

Claim 1:
A method for controlling movement of a plurality of container handling vehicles (<NUM>, <NUM>) on a rail system (<NUM>) arranged at least partially across a top of a framework structure (<NUM>) of an automated storage and retrieval system (<NUM>), on which rail system (<NUM>) the plurality of container handling vehicles (<NUM>,<NUM>) are operable to raise storage containers (<NUM>) from, and lower storage containers (<NUM>) into, storage columns (<NUM>) arranged in rows between upright members (<NUM>) and horizontal members (<NUM>) of the framework structure (<NUM>), and also to transport the storage containers (<NUM>) above the storage columns (<NUM>), and where the following steps are performed by a central operational controller (<NUM>) which is in communication with a local controller in each container handling vehicle (<NUM>, <NUM>):
- receiving data relating to a subsection (401a, 401b) of the rail system (<NUM>), the data comprising a container handling vehicle movement threshold for the subsection (401a, 401b);
- instructing a container handling vehicle (<NUM>, <NUM>) to follow a path (<NUM>, <NUM>) which takes in at least a part of the subsection (401a, 401b);
- instructing the container handling vehicle (<NUM>, <NUM>) to reduce speed and/or acceleration such that the movement of the container handling vehicle (<NUM>, <NUM>) within the subsection (401a, 401b) is below the container handling vehicle movement threshold of the subsection (401a, 401b),
characterized in that the container handling vehicle movement threshold sets a maximum linear momentum of the container handling vehicle (<NUM>, <NUM>).