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 201a 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.

Such a vehicle is described in detail in e.g. NO317366.

<FIG> shows another container handling vehicle, which is in the form of a container delivery vehicle <NUM> that comprises a container carrier arranged above a vehicle body 401a to receive a storage container <NUM>. The container delivery vehicle <NUM> comprises drive means 401b in first direction X, and drive means 401c in the second direction Y, similar to that of the other aforementioned container handling vehicles <NUM>, <NUM>.

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'.

<CIT>, illustrates a typical configuration of rail system <NUM> comprising rails and parallel tracks in both X and Y directions.

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 storage system comprising a multi trolley vehicle for transporting storage containers. The multi trolley vehicle comprises a plurality of trolleys coupled to each other and a first and second drive vehicles.

<CIT>, describes a material storage system comprising a push-pull assembly for driving a skip car to move along a circulating conveying line.

<CIT>, describes a storage system comprising diverting means adapted to divert containers from a moving means to a storage positions and from the storage positions to the moving means.

<CIT>, describes a storage system, where the container handling vehicles are arranged with sensors that can detect the location of the vehicle, and proximity sensor to detect the location of nearby vehicles, and communicate that information to the control system. The control system communicates with a plurality of container handling vehicles and commands the container handling vehicles to form a "train" of vehicles, i.e. a plurality of container handling vehicles proximately arranged in series and arranged to move with one another in tandem. The assembly of the train is accomplished with help of the sensors in the container handling vehicles, by the control system's knowledge about the container handling vehicles' relative positions, or a combination of both. However, the position of a container handling vehicle on the rail system is not known with certainty until it has passed a track crossing, after which the position of the container handling vehicle may be transmitted to the control system which processes this information. This results in a delay due to the command being relayed through, and processed in, the control system, and in insufficient positioning information for effective train driving for the container handling vehicles. Various methodologies to mitigate this problem is described, such as adding proximity sensors on each container handling vehicle or physical coupling such as latches, magnetic coupling etc..

<CIT> describes, in accordance with its abstract, a support vehicle for performing support operations in an automated storage and retrieval system. The support vehicle comprises a vehicle body. The support vehicle comprises a drive system comprising wheels provided in a lower part of the vehicle body, where the drive system being configured to drive the support vehicle along a track system of the automated storage and retrieval system. The support vehicle comprises a connection system provided on a first side of the support vehicle. The connection system comprises a connector member protruding through a aperture of the vehicle body. The connection system comprises an actuator for moving the connector member in the aperture in relation to the vehicle body. The document also relates to an automated storage and retrieval system.

The delay is particularly problematic around ports and similar where the container handling vehicles has a tendency to queue up. This is illustrated with reference to <FIG>. A first and second container handling vehicles <NUM>, <NUM> both have the same grid cell as their final target position TP1. The grid cell will typically be a port, where the container handling vehicles performs actions such as lifting and lowering storage containers.

<FIG> illustrates the first step where the first container handling vehicle <NUM> is instructed to move to the final target position TP1, and the second container handling vehicle <NUM> is instructed to move the position (grid cell) next to the final target position TP1.

<FIG> illustrates the next step where the first container handling vehicle <NUM> has completed its actions in the final target position TP1, and starts to move out of TP1. The second container handling vehicle <NUM> does not move.

<FIG> illustrates the next step where the first container handling vehicle <NUM> is out of TP1, that is the first container handling vehicle <NUM> has passed a track crossing on the rail system <NUM>. After the first container handling vehicle <NUM> is all out of TP1, it sends a confirmation message to the control system that is has moved out of TP1. The second container handling vehicle <NUM> does not move.

<FIG> illustrates the next step, where the second container handling vehicle <NUM> has been instructed to move into the final target position TP1.

The present invention regards a solution for queue driving of container handling vehicles in order to save time around ports avoiding the need to wait for the confirmation messages and instructions to move.

The invention hence solves the problem by letting the container handling vehicles <NUM>, <NUM> queue up mechanically. The container handling vehicles <NUM>, <NUM> drives bumper to bumper without actually having anything holding them together. They stay bumper to bumper by having the last container handling vehicle drive a little faster than the front container handling vehicles, and by letting the front container handling vehicle brake a little more than the last container handling vehicle.

The solution may also be used for longer trains, in which case a third container handling vehicle moves faster than the second container handling vehicle, a fourth container handling vehicle moves faster than the third container handling vehicle and so on.

In one aspect he present invention relates to a method of 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 handle storage containers, and where the following steps are performed by a control system which is in communication with a local controller in each container handling vehicle,.

An advantage of this invention is that it allows a plurality of container handling vehicles to queue up mechanically in order to save time around ports avoiding the need to wait for the confirmation messages and instructions to move.

The target position may be any position on the rail system. The target position may be a final position on the rail system, such as port position, or the target position may be any intermediate positions on its way to a final position. The vehicle may for example be instructed to move to a first position on the rail system where the vehicle waits for another vehicle to pass, before getting instructions to move to a second position in step-by-step instructions.

Instructing to apply a push force may comprise instructing the second container handling vehicle to exceed a non-pushing force required for movement of the second container handling vehicle. The non-pushing force may be exceeded by <NUM> - <NUM>%, preferably <NUM> - <NUM> %, or most preferably <NUM> - <NUM> %.

The push force and the non-pushing force may be determined by measuring power usage of the second container handling vehicle.

Instructing to apply a push force may comprise instructing the second container vehicle to move according to a movement vector exceeding a corresponding movement vector of the first container handling vehicle in the first direction. The corresponding movement vector of the first container handling vehicle in the first direction may be exceeded by <NUM> - <NUM>%, preferably <NUM> - <NUM> %, or most preferably <NUM> - <NUM> %.

In one embodiment, the method may further comprise after determining that the first container handling vehicle has not moved within a predetermined time interval, stopping applying the push force on the first container handling vehicle. The determination that the first container handling vehicle has not moved within the predetermined time interval may comprise determining with the second container handling vehicle that the second container handling vehicle has not moved within the predetermined time interval.

In one embodiment, the method may further comprise initiating an emergency stop of the second container handling vehicle after determining, with the second container handling vehicle, a deceleration above a predefined threshold.

In one embodiment, the method may further comprise upon determining with the second container handling vehicle that the first container handling vehicle is moving, increasing the push force on the first container handling vehicle.

In a second aspect, the present invention also relates to a an automated storage and retrieval system comprising a plurality of container handling vehicles on a rail system arranged at least partially across a top of framework structure of the automated storage and retrieval system, on which rail system the plurality of container handling vehicles are operable to handle storage containers, and a control system adapted to be in communication with the local controller in each controller handling vehicle, the control system further being adapted to perform the steps of:.

Instructing to apply a push force may comprise instructing the second container handling vehicle to exceed a non-pushing force required for default movement of the second container handling vehicle. The non-pushing force may be exceeded by <NUM> - <NUM>%, preferably <NUM> - <NUM> %, or most preferably <NUM> - <NUM> %.

The second container handling vehicle may be adapted to stop applying the push force on the first container handling vehicle after determining that the first container handling vehicle has not moved within a predetermined time interval.

The second container handling vehicle may be adapted to determine that the first container handling vehicle has not moved within the predetermined time interval by determining that the second container handling vehicle has not moved within the predetermined time interval.

In one embodiment, the system may further be adapted to initiate an emergency stop of the second container handling vehicle after determining, with the second container handling vehicle, a deceleration above a predefined threshold.

The second container handling vehicle may be adapted to upon determining that the first container handling vehicle is moving, increasing the push force on the first container handling vehicle.

The contact areas between the first container handling vehicle and the second container handling vehicle may provided with a low friction protection surface.

In a third aspect, the present invention also relates to a computer program product for a control system described above, wherein the computer program product comprising instructions that when performed on the control system performs the method described above.

The present invention relates to a system and method that allows a plurality of container handling vehicles to form a "train" of vehicles, i.e. a plurality of container handling vehicles arranged in series or queues and arranged to move with one another in tandem. This save time around ports avoiding the need to wait for the confirmation messages and instructions to move. Compared with the prior art method described with reference to <FIG>, the inventive method saves approximately <NUM> per operation. Given sufficient capacity of container handling vehicles, the inventive method saves <NUM> seconds per hour for a port nominally receiving <NUM> storage containers per hour, this gives a <NUM> % increase in efficiency.

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> schematically illustrates a situation where the first and second container handling vehicle <NUM>, <NUM> both have grid cell TP1 as their designated first target position.

In <FIG>, the first container handling vehicle <NUM> is instructed to move in a first direction towards TP1.

Then in <FIG>, the second container handling vehicle <NUM> is instructed to move in the first direction towards TP1 into physical contact with the first container handling vehicle <NUM>. After contact, the second container handling vehicle <NUM> applies a push force on the first container handling vehicle <NUM>, i.e. urge against the first container handling vehicle <NUM>, to maintain physical contact.

In <FIG>, when the first container handling vehicle <NUM> is finished in TP1 it begins to move out of TP1 and the second container handling vehicle <NUM> follows in contact with the first container handling vehicle <NUM> by applying the push force.

In <FIG>, when the first container handling vehicle <NUM> is out of TP1, the second container handling vehicle <NUM> is ready in TP1. The second container handling vehicle <NUM> move the first container handling device <NUM> without having to wait for any confirmation messages and/or instructions to move.

<FIG> illustrates a second container handling vehicle <NUM> moving in the first direction towards the first target position TP1. TP1 is in this example the position of the first container handling vehicle <NUM>. TP1 is also a storage column <NUM> where both the first container handling vehicle <NUM> and the second container handling vehicle <NUM> have been instructed to retrieve storage containers from, for example, as part of a digging process. TP1 may also be a port position.

<FIG> illustrates the second container handling vehicle <NUM> physically contacting the first container handling vehicle <NUM>. After contacting the first container handling vehicle <NUM>, the second container handling vehicle <NUM> applies a push force, i.e. is urging against the first container handling vehicle <NUM>. The second container handling vehicle <NUM> may continue to apply the push force indefinitely, but in order to avoid burned/damaged electronics will stop applying the push force if the first container handling vehicle <NUM> does not move within a timeout period.

<FIG> illustrates that second container handling vehicle <NUM> moves with the first container handling vehicle <NUM> when the first container handling vehicle starts to move away from TP1. The second container handling vehicle <NUM> may be arranged to determine that the first container handling vehicle <NUM> is moving. Upon determining that the first container handling vehicle <NUM> is moving, the second container handling vehicle <NUM> may increase the push force on the first container handling vehicle <NUM>. The second container handling vehicle <NUM> may apply a low push force while standing still and waiting for the first container handling vehicle <NUM> to move. Upon determining that the first container handling vehicle <NUM> is moving, the second container handling vehicle <NUM> may follow the first container handling vehicle <NUM> using a higher force to keep in contact and avoid bumping. Applying a low force while waiting may avoid burned electronics and/or wear on mechanical components. Determining that the first container handling vehicle <NUM> is moving may be determined based on change in power usage for the second container handling vehicle <NUM>. Alternatively, the second container handling vehicle <NUM> may be provided with pressure sensors in the contact area between the first and second container handling vehicle <NUM>, <NUM> that measures the applied force and/or change in applied force.

In one embodiment the second container handling vehicle <NUM> is instructed to apply a push force exceeding a non-pushing force required for movement of the second container handling vehicle <NUM>. The non-pushing force may be the inertia to movement that has to be overcome before the second container handling vehicle <NUM> starts to move along the rail system from stationary, or the force required to keep the second container handling vehicle <NUM> to move along the rail system by itself. The non-pushing force may be given by the total weight of the second container handling device <NUM> and/or other driving configurations of the second container handling device <NUM>.

When the push force is defined as a force exceeding the non-pushing force, the second container handling vehicle <NUM> may dynamically adjust the push force based on feedback so that the amount of push force is kept within a tight range of just nudging the first container handling device <NUM> and as it moves adjusting the output of the second container handling vehicle to keep within that range. The second container handling vehicle <NUM> may determine the push force and the non-pushing force by measuring power usage of the second container handling vehicle <NUM>. The power use may provide the feedback to dynamically adjust the amount of push force.

The non-pushing force may be exceeded by <NUM> - <NUM> %, <NUM> - <NUM> % or <NUM> - <NUM>% to provide the necessary push force.

In another embodiment, the push force is defined by instructing the second container handling vehicle <NUM> to move according to a movement vector in the direction of the first container handling vehicle <NUM>. The movement vector of the second container handling vehicle <NUM> exceeds a corresponding movement vector of the first container handling vehicle <NUM>:.

The movement vector of the first container handling vehicle <NUM> in the first direction may be exceeded by <NUM> - <NUM> %, <NUM> - <NUM> % or <NUM> - <NUM>% to provide the necessary push force.

The first and second container handling vehicle <NUM>, <NUM> are configured to allow more unexpected behaviour when driving in queue formation than when driving alone before reporting errors to the control system. Still, if the first container handling vehicle <NUM> fails, the second container handling vehicle <NUM> should be instructed by the control system to initiate an emergency stop. Errors in the in the communication system, delays in the control system, delays in the communications system, crashes on the rail system etc. may prohibit the control system to instruct the container handling vehicle <NUM> to stop. The second container handling vehicle <NUM> may therefore be adapted to initiate an emergency stop of the second container handling vehicle <NUM> after determining, with the second container handling vehicle <NUM>, a deceleration above a predefined threshold. This determination may be based on measurements of the push force using power usage, external sensor or other means of measuring force.

<FIG> illustrate both container handling vehicles <NUM>, <NUM> of the cantilever type <NUM> moving in the X-direction, and container handling vehicles <NUM>, <NUM> of the cavity type <NUM> moving in either X- or Y-direction. In order to avoid damage to the container handling vehicles <NUM>, <NUM>, e.g., from metal debris that ends up in the rails or in the electronics etc., the contact surfaces <NUM> is provided with a low friction protection surface, e.g. a gliding surface.

<FIG> illustrate the same movement of two container handling vehicles <NUM>, <NUM> of the cantilever type <NUM> moving in the Y-direction. It is otherwise similar to the sequence of <FIG>.

In one embodiment the queue of container handling vehicles may comprise more than two container handling vehicles <NUM>, <NUM>. In that case a third container handling vehicle applies a larger push force than the second container handling vehicle <NUM>, a fourth container handling vehicle applies a larger push force than the third container handling vehicle and so on for each container handling vehicle further back in the queue of container handling vehicles.

A plurality of container handling vehicles may also drive in queue for a first distance, and then split into several smaller queues. Container handling vehicles in front of the container handling vehicles that split off may continue at the current speed, whereas container handling vehicles behind the container handling vehicles that split off will have to slow down. After splitting the smaller queues will reconfigure and continue as described above.

Claim 1:
A method of controlling movement of a plurality of container handling vehicles (<NUM>, <NUM>, <NUM>) on a rail system (<NUM>) arranged at least partially across a top of framework structure (<NUM>) of an automated storage and retrieval system (<NUM>), on which rail system (<NUM>) the plurality of container handling vehicles (<NUM>, <NUM>, <NUM>) are operable to handle storage containers (<NUM>), and where the following steps are performed by a control system (<NUM>) which is in communication with a local controller in each container handling vehicle (<NUM>, <NUM>, <NUM>):
instructing a first container handling vehicle (<NUM>) to move in a first direction towards a grid cell designated as a first target position (TP1) on the rail system (<NUM>);
instructing a second container handling vehicle (<NUM>) to move in the first direction towards the first target position (TP1) such that the second container handling vehicle (<NUM>) physically contacts the first container handling vehicle (<NUM>), and the second container handling vehicle (<NUM>) after contact applies a push force on the first container handling vehicle (<NUM>) to maintain physical contact.