EP4673893A1

EP4673893A1 - A system for monitoring the location of stock in a warehouse

Info

Publication number: EP4673893A1
Application number: EP24707763.9A
Authority: EP
Inventors: David Edgar; Matthew WROE; Milos BOZIC
Original assignee: Three Smith Group Ltd
Current assignee: Three Smith Group Ltd
Priority date: 2023-02-27
Filing date: 2024-02-27
Publication date: 2026-01-07
Also published as: JP2026507685A; GB202302785D0; GB2627737A; AU2024229079A1; CN120858366A; WO2024180032A1

Abstract

A system for monitoring the location of stock in a warehouse. The system comprising: a mobile sensor system for attaching to a vehicle that moves around the warehouse. The mobile sensor system comprises an RFID antenna that is configured to: provide RFID-signalling that is representative of one or more RFID-tag-signals received from one or more RFID tags. The system for monitoring the location of stock in the warehouse further comprises a controller configured to: process the RFID-signalling to determine one or more infrastructure-RFID-tag-identifiers that are associated with RFID tags that are associated with items of static infrastructure in the warehouse; determine an antenna-location based on the determined one or more infrastructure- RFID-tag-identifiers; process the RFID-signalling to determine one or more stock- RFID-tag-identifiers that are associated with RFID tags that are associated with moveable items of stock in the warehouse; associate the stock-RFID-tag-identifiers with the determined antenna-location; and provide stock-location-signalling based on the association between the stock-RFID-tag-identifiers and the antenna-location.

Description

A SYSTEM FOR MONITORING THE LOCATION OF STOCK IN A WAREHOUSE

The present disclosure relates to systems and methods for monitoring the location of stock in a warehouse, and in particular to systems and methods that use an RFID antenna.

According to a first aspect of the present disclosure, there is provided a system for monitoring the location of stock in a warehouse, the system comprising : a mobile sensor system for attaching to a vehicle that moves around the warehouse, the mobile sensor system comprising : an RFID antenna that is configured to: transmit an RFID-scanning-signal to excite one or more RFID tags in the vicinity of the RFID antenna; and provide RFID-signalling that is representative of one or more RFID-tag-signals received from one or more RFID tags; the system for monitoring the location of stock in the warehouse further comprising a controller configured to: process the RFID-signalling to determine one or more infrastructure- RFID-tag-identifiers that are associated with RFID tags that are associated with items of static infrastructure in the warehouse; determine an antenna-location based on the determined one or more infrastructure-RFID-tag-identifiers, wherein the antenna-location represents the location of the RFID antenna in the warehouse when the RFID-signalling was acquired; process the RFID-signalling to determine one or more stock-RFID-tag- identifiers that are associated with RFID tags that are associated with moveable items of stock in the warehouse; associate the stock-RFID-tag-identifiers with the determined antennalocation for RFID-signalling that was acquired at substantially the same time; and provide stock-location-signalling based on the association between the stock-RFID-tag-identifiers and the antenna-location.

Advantageously such a system can provide a convenient and efficient way of monitoring the location of stock in a warehouse. The stock-location-signalling may include a location for each detected item of stock such that the location of those items of stock can be visually represented on a map of the warehouse.

The items of static infrastructure in the warehouse may comprise one or more of a post, a barrier, a racking leg, a post-cap, a gate post, and a shelf.

The controller may be configured to: process the RFID-signalling to determine a first-infrastructure-RFID-tag- identifier and a second-infrastructure-RFID-tag-identifier, which are associated with RFID tags that are associated with different items of static infrastructure in the warehouse; compare the signal strength of the RFID-tag-signal for the first infrastructure- RFID-tag-identifier with the signal strength of the RFID-tag-signal for the second infrastructure-RFID-tag-identifier in order to determine if the RFID antenna is closer to the RFID tag associated with the first infrastructure-RFID-tag-identifier or the RFID tag associated with the second infrastructure-RFID-tag-identifier; and provide the stock-location-signalling based on the comparison of the signal strengths.

The system may further comprise: a static sensor system that is attached to any stationary item of infrastructure in the warehouse, wherein the static sensor system comprises: a static RFID antenna at a known location in the warehouse, wherein the RFID antenna is configured to: transmit an RFID-scanning-signal to excite one or more RFID tags in the vicinity of the RFID antenna; and provide RFID-signalling that is representative of one or more RFID-tag-signals received from one or more RFID tags; and wherein the controller is configured to: process the RFID-signalling from the static RFID antenna to determine one or more stock-RFID-tag-identifiers that are associated with RFID tags that are associated with moveable items of stock; associate the stock-RFID-tag-identifiers determined from the RFID- signalling provided by the static RFID antenna with the known location of the static RFID antenna; and provide the stock-location-signalling based on the association between the stock-RFID-tag-identifiers determined from the RFID-signalling provided by the static RFID antenna and the known location of the static RFID antenna.

The mobile sensor system may further comprise a second RFID antenna, which is configured to: transmit a second RFID-scanning-signal to excite one or more RFID tags in the vicinity of the RFID antenna; and provide second-RFID-signalling that is representative of one or more RFID-tag- signals received from one or more RFID tags.

The controller may be further configured to: process the second RFID-signalling to determine one or more infrastructure- RFID-tag-identifiers that are associated with RFID tags that are associated with items of static infrastructure in the warehouse; determine a second-antenna-location based on the determined one or more infrastructure-RFID-tag-identifiers, wherein the second-antenna-location represents the location of the second RFID antenna in the warehouse when the second-RFID- signalling was acquired; process the second-RFID-signalling to determine one or more stock-RFID-tag- identifiers that are associated with RFID tags that are associated with moveable items of stock in the warehouse; associate the stock-RFID-tag-identifiers with the determined second-antenna- location for second-RFID-signalling that was acquired at substantially the same time; and provide the stock-location-signalling based on the association between the stock-RFID-tag-identifiers and the second-antenna-location.

The RFID antenna may be configured to: provide subsequent RFID-signalling in response to subsequent transmission of an RFID-scanning-signal. The controller is configured to: process the subsequent RFID-signalling to determine one or more subsequent infrastructure-RFID-tag-identifiers that are associated with RFID tags that are associated with items of static infrastructure in the warehouse; determine a subsequent antenna-location based on the determined one or more subsequent infrastructure-RFID-tag-identifiers, wherein the subsequent antenna- location represents the location of the RFID antenna in the warehouse when the subsequent RFID-signalling was acquired; process the subsequent RFID-signalling to determine one or more subsequent stock-RFID-tag-identifiers that are associated with RFID tags that are associated with moveable items of stock in the warehouse; associate the subsequent stock-RFID-tag-identifiers with the subsequent antenna-location for the subsequent RFID-signalling that was acquired at substantially the same time; and determine if the stock-RFID-tag-identifiers and the subsequent stock-RFID-tag- identifiers are associated with the same RFID tags but are associated with different antenna-locations, and if they are, then provide an output-signal that indicates that the movable items of stock that are associated with the RFID tags are in transit with the vehicle to which the mobile sensor system is attached.

The controller may be further configured to: control the RFID antenna such that it periodically transmits an RFID-scanning- signal.

The controller may be configured to set the period with which the RFID antenna transmits an RFID-scanning-signal based on the speed of the vehicle to which the mobile sensor system is attached.

The RFID tags may be passive.

The controller may be configured to: determine that an RFID-tag-signal is present in the RFID-signalling only if the RFID-tag-signal has a signal strength that is greater than a threshold value.

According to a further aspect of the present disclosure, there is provided a method of monitoring the location of stock in a warehouse, the method comprising: an RFID antenna that is attached to a vehicle that moves around the warehouse transmitting an RFID-scanning-signal to excite one or more RFID tags in the vicinity of the RFID antenna, and providing RFID-signalling that is representative of one or more RFID-tag-signals received from one or more RFID tags; processing the RFID-signalling to determine one or more infrastructure-RFID- tag-identifiers that are associated with RFID tags that are associated with items of static infrastructure in the warehouse; determining an antenna-location based on the determined one or more infrastructure-RFID-tag-identifiers, wherein the antenna-location represents the location of the RFID antenna in the warehouse when the RFID-signalling was acquired; processing the RFID-signalling to determine one or more stock-RFID-tag- identifiers that are associated with RFID tags that are associated with moveable items of stock in the warehouse; associating the stock-RFID-tag-identifiers with the determined antenna-location for RFID-signalling that was acquired at substantially the same time; and providing stock-location-signalling based on the association between the stock- RFID-tag-identifiers and the antenna-location.

There may be provided a computer program, which when run on a computer, causes the computer to configure any apparatus, including a controller, system or device disclosed herein or perform any method disclosed herein. The computer program may be a software implementation, and the computer may be considered as any appropriate hardware, including a digital signal processor, a microcontroller, and an implementation in read only memory (ROM), erasable programmable read only memory (EPROM) or electronically erasable programmable read only memory (EEPROM), as non-limiting examples. The software may be an assembly program.

The computer program may be provided on a computer readable medium, which may be a physical computer readable medium such as a disc or a memory device, or may be embodied as a transient signal. Such a transient signal may be a network download, including an internet download. There may be provided one or more non-transitory computer-readable storage media storing computer-executable instructions that, when executed by a computing system, causes the computing system to perform any method disclosed herein.

One or more embodiments will now be described by way of example only with reference to the accompanying drawings in which:

Figure 1 shows schematically a plan view of part of the inside of a warehouse;

Figure 2 shows an example embodiment of a system for monitoring the location of stock in a warehouse; Figure 3 shows another example embodiment of a system for monitoring the location of stock in a warehouse

Figure 4 shows a further still example embodiment of a system for monitoring the location of stock in a warehouse;

Figures 5a and 5b illustrate an example embodiment of a system that can identify stock that is in transit with a forklift truck to which a mobile sensor system is attached; and

Figure 6 illustrates an example embodiment of a method of monitoring the location of stock in a warehouse.

It can be difficult to keep track of stock in a warehouse, especially a very large warehouse. Also, in some circumstances, containers that store multiple items of stock (such as totes, boxes or pallets) can accumulate in certain areas of a warehouse. It can be difficult to identify that this is happening and where it is happening.

Figure 1 shows schematically a plan view of part of the inside of a warehouse, which is a suitable environment for systems and methods that are described herein. Figure 1 shows six banks of racking 101, with aisles 102 in between each bank 101. As shown in Figure 1, a forklift truck (FLT) 108 can drive along the aisles in order to access stock that is stored in different banks of racking 101. Each bank of racking 101 has a plurality of racking legs 103. A racking leg 103 is a vertical support that is used to support shelving or pallets. The banks of racking 101 can also include beams (that are generally horizontal) and / or braces (that extend generally diagonally with reference to the ground).

Figure 1 also shows that a part of the warehouse is designated as a pedestrian walkway

104. The pedestrian walkway 104 is separated from an end aisle of racking by a barrier

105. In this example, the barrier 105 is shown as including a plurality of spaced apart posts 106, with rails 107 joining the majority of the adjacent posts 106. A pedestrian access point 109 is shown as a gap in the barrier, through which a pedestrian can walk to move between the pedestrian walkway 104 and a part of the warehouse in which the FLT 108 operates.

Each of the posts 106, barriers 105, racking legs 103, and banks of racking 101 are examples of static items of warehouse infrastructure according to the present disclosure. Additionally, one or more of the following can also be considered as static items of warehouse infrastructure: a post-cap (that is, a cap on a post), a gate post, a shelf, and any other barrier or divider between different areas in a warehouse (including barriers between different stock storage areas).

Figure 2 shows an example embodiment of a system 209 for monitoring the location of stock 215 in a warehouse. The system 209 includes a mobile sensor system 212 that is attached to a vehicle that moves around the warehouse. In this example, the vehicle is a forklift truck (FLT) 210. The mobile sensor system 212 can be powered by a battery that is located on the FLT 210. The system 209 also includes a controller 213 which, as will be disused below, processes signalling received from the mobile sensor system 212 in order to determine the location of the stock 215 in the warehouse. It will be appreciated that some or all of the functionality of the controller 213 can be implemented by one or more devices that are located on the FLT 210 and / or that some or all of the functionality of the controller 213 can be implemented by one or more devices that are remote from the FLT 210.

The mobile sensor system 212 includes an RFID antenna 211 that is shown transmitting an RFID-scanning-signal 216 for exciting one or more RFID tags in the vicinity of the RFID antenna 211. This can also be referred to as the RFID antenna 211 performing an RFID scan. In this example, the RFID antenna 211 is directional in that it transmits the RFID-scanning-signal 216 in a specific direction with respect to the FLT 210. In other examples the RFID antenna 211 may not be directional.

Any RFID tags 219, 220 that are excited by the RFID-scanning-signal 216 transmit an RFID-tag-signal 217,218 in response to the excitation, as is known in the art. In Figure 2, two types of RFID tags are shown: an RFID tag 220 that is associated with moveable items of warehouse stock 215; and RFID tags 219 that are associated with items of static infrastructure 221 in the warehouse. The moveable items of warehouse stock 215 may be individual items of stock, packages of multiple items of stock, and / or a stock container such as a tote or a pallet. The items of static infrastructure in the warehouse that are shown in Figure 2 are posts 221. As will be discussed below, the two different types of RFID tags 219, 220 can be provided with different identifiers, which are provided as part of the RFID-tag-signal 217, 218 such that they can be distinguished from each other. In this example the RFID tags 219, 220 are passive, which is advantageous because batteries do not have to be provided for the RFID tags 219, 220 and therefore there is no need to periodically recharge or replace any such batteries. Furthermore, in this example the RFID tags 219, 220 are ultra high frequency (UHF) tags.

The RFID antenna 211 then provides RFID-sig nailing 214 to the controller 213. The RFID-signalling 214 is representative of the one or more RFID-tag-signals 217, 218 received from one or more RFID tags 219, 220.

The controller 213 processes the RFID-signalling 214 to determine one or more infrastructure-RFID-tag-identifiers that are associated with RFID tags 219 that are associated with items of static infrastructure 221 in the warehouse. In one example, this can be performed by the controller 213 using a look-up table or database to look up an RFID-tag-identifier that is received as part of the RFID-tag-signal 217, 218 in order to determine whether or not it is associated with an item of static infrastructure 221 in the warehouse. If it is, then the RFID-tag-identifier is considered to be an infrastructure-RFID-tag-identifier.

The controller 213 can then determine an antenna-location based on the determined one or more infrastructure-RFID-tag-identifiers. The antenna-location represents the location of the RFID antenna 211 in the warehouse when the RFID-signalling was acquired. In one example, this can be implemented by the controller accessing a lookup table or database that it stored in computer memory. This look-up table or database includes the location in the warehouse of each item of static infrastructure 221 and its associated infrastructure-RFID-tag-identifier. The location can be provided as a set of coordinates or in any appropriate way. If only a single infrastructure-RFID-tag- identifier is identified in the RFID-signalling 214, then the antenna-location can simply be set to be the same as the location of the associated item of static infrastructure 221. If a plurality of infrastructure-RFID-tag-identifiers are identified in the RFID- signalling 214, then the antenna-location can be set based on a combination of the locations of the associated items of static infrastructure 221. For instance, the controller 213 can calculate a mathematical average of the plurality of locations of the items of static infrastructure 221.

One way in which the controller 213 can determine the antenna-location when a plurality of infrastructure-RFID-tag-identifiers are identified is by using the signal strength / power of the received RFID-tag-signals 217 associated with each infrastructure-RFID-tag-identifiers. An example of how the signal strength can be represented is a Received Signal Strength Indicator (RSSI) for the received RFID-tag- signals 217. The controller 213 can compare the signal strength of the RFID-tag-signal 217 for a first infrastructure-RFID-tag-identifier with the signal strength of the RFID- tag-signal 217 for a second infrastructure-RFID-tag-identifier in order to determine if the RFID antenna 211 is closer to the RFID tag 219 associated with the first infrastructure-RFID-tag-identifier or the RFID tag 219 associated with the second infrastructure-RFID-tag-identifier. By comparing the signal strengths in this way, the controller 213 can determine the relative location of the RFID antenna 211. For example, if the locations associated with the first and second infrastructure-RFID-tag- identifiers are offset along a first dimension, then the controller 213 can determine that the RFID antenna is closer to the one of the first and second infrastructure-RFID- tag-identifiers that has the strongest RFID-tag-signal 217.

The controller 213 can also process the RFID-signalling 214 that is received from the RFID antenna 211 to determine one or more stock-RFID-tag-identifiers that are associated with RFID tags 220 that are associated with moveable items of stock 215 in the warehouse. In the same way as that described above, the controller 213 can use a look-up table or database to look up an RFID-tag-identifier that is received as part of the RFID-tag-signal 217, 218 in order to determine whether or not it is associated with a moveable item of stock 215. If it is, then the RFID-tag-identifier is considered to be a stock-RFID-tag-identifier.

Once the controller 213 has distinguished between infrastructure-RFID-tag-identifiers (that are associated with items of static infrastructure 221) and stock-RFID-tag- identifiers (that are associated with moveable items of stock 215), it can determine the location of the stock in the warehouse. In order to do this, the controller 213 associates the stock-RFID-tag-identifiers with the determined antenna-location for RFID-signalling 214 that was acquired at substantially the same time. This can include RFID-signalling 214 that was acquired at exactly the same time (for example as part of the same RFID scan) or at times that are at least a minimum amount of time apart, such as less than 1, 5 or 10 seconds apart.

The controller 213 can then provide stock-location-signalling 222 based on the association between the stock-RFID-tag-identifiers and the antenna-location. The stock-location-signalling 222 can be implemented in any of a number of ways that represents the location of the stock 215 in the warehouse. For example, the stock- location-signalling 222 can include a location for each detected item of stock 215 such that the location of those items of stock can be visually represented on a map of the warehouse or in an inventory with stock locations. In this way, a graphical representation of where the detected stock is in the warehouse can be provided.

In examples where the stock-RFID-tag-identifiers are associated with moveable totes I pallets in the warehouse, the provision of the stock-location-signalling 222 can be especially useful to identify any regions where there has been an unintended build up of (potentially empty) totes / pallets. It can otherwise be particularly difficult to identify the locations of such build-ups in large warehouses that are heavily automated.

Figures 3 and 4 provide further illustrations of example embodiments of systems for monitoring the location of stock in a warehouse.

In Figure 3, a FLT 310 is shown within a warehouse. Stock 315 is shown in an area that is bounded by various items of static infrastructure in the warehouse, one or more of which can be fitted with an RFID tag (not shown). In this example, the items of static infrastructure shown are posts 321, barriers 324, and a post-cap (that is, a cap on the top of a post) 323. In other examples, one or more of the following items of static infrastructure in the warehouse can also be provided, along with an associated RFID tag: a gate post, a shelf and a racking leg.

The FLT 310 includes an RFID antenna 311 that transmits an RFID-scanning-signal 316 in the same way that is described for Figure 2 in order to excite RFID tags that are associated with the stock 315 and the items of static infrastructure 321, 323, 324 in the warehouse.

Also in Figure 3, the system for monitoring the location of stock 315 in the warehouse includes a static sensor system 340. The statis sensor system 340 can be attached to a wall of the warehouse (as shown), or to any stationary item of infrastructure in the warehouse. The static sensor system 340 also includes an RFID antenna (not shown), which is at a location that is known to the system. For example, the location of each static RFID antenna can be stored in memory when the static sensor system 340 is installed. The static sensor system 340 can be powered by mains electricity.

In the same way as the RFID antenna 311 of the mobile sensor system, the RFID antenna of the static sensor system transmits an RFID-scanning-signal to excite one or more RFID tags in the vicinity of the RFID antenna, and provides RFID-signalling that is representative of one or more RFID-tag-signals received from one or more RFID tags. A controller of the system for monitoring the location of stock in a warehouse can then process the RFID-signalling from the static RFID antenna to determine one or more stock-RFID-tag-identifiers that are associated with RFID tags that are associated with moveable items of stock 315. Since the location of the static RFID antenna is already known to the system, the controller can then associate the stock- RFID-tag-identifiers with the known static RFID antenna location; and provide the stock-location-signalling based on: i) information received from the static RFID antenna, i.e. the stock-RFID-tag-identifiers determined from the RFID-signalling provided by the static RFID antenna along with the associated static RFID antenna location; and ii) information received from the mobile RFID antenna 311, i.e. the association between the stock-RFID-tag-identifiers determined from the RFID- signalling provided by the mobile RFID antenna and the determined antenna-location.

In this way, the controller can be provided with information from the static RFID antenna that can be used to verify the locations of the stock 315 that is determined by the mobile sensor system. If the controller identifies that there is a discrepancy between the location of any item of stock 315 as it is determined from signals that are provided by the mobile and static RFID antennas, then the controller can provide an alert to a user to indicate that the system is malfunctioning.

In Figure 4, a FLT 410 is shown that has a first RFID antenna 411a and a controller that is housed within a truck top box 413. The first RFID antenna 411a transmits a first RFID-scanning-signal 416a that excites RFID tags 420 associated with stock / totes 415, and also excites RFID tags associated with items of static infrastructure such as the barrier / post that is fitted with a post-cap 425 as shown in Figure 4. The first RFID antenna 411a can thus provide first-RFID-signalling.

In Figure 4, the FLT 410 also has a second RFID antenna 411b. The second RFID antenna 411b transmits a second RFID-scanning-signal 416b that can also excite RFID tags associated with stock / totes and RFID tags associated with items of static infrastructure. The second RFID antenna 411b can thus provide second-RFID- signalling. The controller of the system can process each of the and the second-RFID- signalling to determine the location of stock in the same way that is discussed above. In Figure 4, the first and second RFID antennas 411a, 411b are directional and point in opposite directions away from the FLT 410. In this way, the system for identifying stock 415 can perform RFID scans that cover a large area.

In another embodiment, the first and second RFID antennas 411a, 411b can be directional and point in the same direction. As shown in Figure 4, they are still spaced apart from each other in a first dimension. In such an example, the controller can compare the signal strength of an RFID-tag-signal in the first-RFID-sig na I li ng with the signal strength of an RFID-tag-signal in the second-RFID-signalling in order to determine the location of the associated tag with respect to the FLT 410 in the first dimension. By comparing the signal strengths in this way, the controller can determine if the associated RFID tag is closer to the first RFID antenna 411a or the second RFID antenna 411b, and therefore it can determine the relative location of the associated RFID tag in the first dimension (the dimension along with the first and second RFID antennas 411a, 411b are offset). This can improve the accuracy with which the location of stock can be determined.

Figures 5a and 5b illustrate an example embodiment of a system that can identify stock 515 that is in transit with a FLT 510 to which a mobile sensor system 512 is attached. Figure 5a shows the FLT 510 at a first instant in time, at which it is near a first post 526. Figure 5b shows the FLT 510 at a second instant in time, subsequent to the first instant in time, at which it is near a second post 528. In the same way as described above, the mobile sensor system 512 includes an RFID antenna 511 and a controller 513.

Referring initially to Figure 5a, the RFID antenna 511 transmits an RFID-scanning- signal 516a at the first instance in time. In response to receiving RFID-tag-signals 518a, 530 from any RFID tags 520, 527 in the vicinity of the RFID antenna 511, the controller 513 provides RFID-signalling 514a to the controller 513.

The controller 513 then processes the RFID-signalling 514a to determine one or more infrastructure-RFID-tag-identifiers that are associated with RFID tags 527 that are associated with items of static infrastructure in the warehouse (in Figure 5a this is the first post 526). In the same way as described above with reference to Figure 2, the controller 513 can then determine an antenna-location based on the determined one or more infrastructure-RFID-tag-identifiers, wherein the antenna-location represents the location of the RFID antenna 511 in the warehouse when the RFID-signalling 514a was acquired (i.e. at the first instant in time).

Similarly, the controller 513 can process the RFID-signalling 514a to determine one or more stock-RFID-tag-identifiers that are associated with RFID tags 520 that are associated with moveable items of stock 515 in the warehouse. As shown in Figure 5a, an item of stock 515 with the RFID tag 520 is located on the forks of the FLT 510 such that the stock 515 is in transit with the FLT 510. The controller 513 can then associate the stock-RFID-tag-identifiers with the determined antenna-location for the RFID-signalling 514a that was acquired at the first instant in time.

Turning now to Figure 5b, the RFID antenna 511 transmits a subsequent RFID- scanning-signal 516b at the second instance in time. In response to receiving subsequent RFID-tag-signals 518b, 531 from any RFID tags 520, 529 in the vicinity of the RFID antenna 511, the controller 513 provides subsequent RFID-signalling 514b to the controller 513.

The controller 513 then processes the subsequent RFID-signalling 514b to determine one or more subsequent infrastructure-RFID-tag-identifiers that are associated with RFID tags 529 that are associated with items of static infrastructure in the warehouse (in Figure 5b this is the second post 528). In the same way as described with reference to Figure 2, the controller 513 can then determine a subsequent antenna-location based on the determined one or more subsequent infrastructure-RFID-tag-identifiers, wherein the subsequent antenna-location represents the location of the RFID antenna 511 in the warehouse when the subsequent RFID-signalling 514b was acquired (i.e. at the second instant in time).

The controller 513 can also process the subsequent RFID-signalling 514b to determine one or more subsequent stock-RFID-tag-identifiers that are associated with RFID tags 520 that are associated with moveable items of stock 515 in the warehouse. As shown in Figure 5b, the same item of stock 515 (with the same RFID tag 520) that is shown in Figure 5a is still located on the forks of the FLT 510. The controller 513 can then associate the subsequent stock-RFID-tag-identifiers with the subsequent antennalocation for the subsequent RFID-signalling that was acquired at substantially the same time (i.e. at the second instant in time). The controller 513 can then determine if the stock-RFID-tag-identifiers (from the initial RFID-signalling 514a that is shown in Figure 5a) and the subsequent stock-RFID-tag- identifiers (from the subsequent RFID-signalling 514b that is shown in Figure 5b) are associated with the same RFID tag 520 but are associated with different antennalocations. If they are, then the controller can provide an output-signal that indicates that the movable items of stock 515 that are associated with the RFID tags 520 are in transit with the FLT 510. Optionally, the controller 513 may only provide such an output-signal if there is at least a minimum distance between the antenna-location determined for the initial RFID-signalling 514a and the antenna-location determined for the subsequent RFID-signalling 514b. Such a minimum distance may be at least the range of the RFID antenna 511. In this way, the likelihood of identifying that a stationary item of stock 515 is in transit can be reduced.

In some examples, the controller 513 can control the RFID antenna 511 such that it periodically performs RFID scans. The controller 513 can optionally set the period between successive RFID scans based on the speed of the FLT 510. For instance, the controller 513 can receive a vehicle-speed-signal that represents the speed of the FLT 510. A speed sensor associated with the FLT 510 can provide the vehicle-speed-signal. The controller 513 can then set the time period between successive RFID scans based on the vehicle-speed-signal such that the RFID scans are performed more frequently for relative fast speeds than for relatively slow speeds. In this way, the RFID scans can be performed in such a way that most, if not all, stock 515 is identified, yet an unnecessarily high number of RFID scans do not need to be performed. Thereby being efficient with the energy consumption that is required for the RFID scans. Furthermore, RFID scans may be temporarily suspended when the FLT 510 is stationary.

In any of the examples disclosed herein, the controller may determines that an RFID- tag-signal is present in the RFID-signalling only if the RFID-tag-signal has a signal strength that is greater than a threshold value. One example of how the signal strength can be represented is a Received Signal Strength Indicator (RSSI) for the received RFID-tag-signals. In this way, weak RFID-tag-signals, perhaps because they are too far away to be considered in the vicinity of the RFID antenna, can be excluded from further processing.

Figure 6 illustrates an example embodiment of a method of monitoring the location of stock in a warehouse. At step 650, the method includes an RFID antenna, which is attached to a vehicle that moves around the warehouse, transmitting an RFID-scanning-signal. The RFID- scanning-signal is for exciting one or more RFID tags in the vicinity of the RFID antenna, also at step 650, the method involves providing RFID-sig nailing that is representative of one or more RFID-tag-signals received from one or more RFID tags.

At step 651, the method includes processing the RFID-signalling to determine one or more infrastructure-RFID-tag-identifiers that are associated with RFID tags that are associated with items of static infrastructure in the warehouse. An example of how to distinguish an infrastructure-RFID-tag-identifier from an RFID-tag-identifier that is not associated with an item of static infrastructure in the warehouse is described above.

At step 652, the method includes determining an antenna-location based on the determined one or more infrastructure-RFID-tag-identifiers. The antenna-location represents the location of the RFID antenna in the warehouse when the RFID-signalling was acquired.

At step 653, the method includes processing the RFID-signalling to determine one or more stock-RFID-tag-identifiers that are associated with RFID tags that are associated with moveable items of stock in the warehouse. It will be appreciated that steps 651 and 653 can be performed in either order, or even simultaneously.

At step 654, the method includes associating the stock-RFID-tag-identifiers with the determined antenna-location for RFID-signalling that was acquired at substantially the same time. Then at step 655, the method involves providing stock-location-signalling based on the association between the stock-RFID-tag-identifiers and the antennalocation.

Claims

1. A system for monitoring the location of stock in a warehouse, the system comprising: a mobile sensor system for attaching to a vehicle that moves around the warehouse, the mobile sensor system comprising: an RFID antenna that is configured to: transmit an RFID-scanning-signal to excite one or more RFID tags in the vicinity of the RFID antenna; and provide RFID-signalling that is representative of one or more RFID-tag-signals received from one or more RFID tags; the system for monitoring the location of stock in the warehouse further comprising a controller configured to: process the RFID-signalling to determine one or more infrastructure- RFID-tag-identifiers that are associated with RFID tags that are associated with items of static infrastructure in the warehouse; determine an antenna-location based on the determined one or more infrastructure-RFID-tag-identifiers, wherein the antenna-location represents the location of the RFID antenna in the warehouse when the RFID-signalling was acquired; process the RFID-signalling to determine one or more stock-RFID-tag- identifiers that are associated with RFID tags that are associated with moveable items of stock in the warehouse; associate the stock-RFID-tag-identifiers with the determined antennalocation for RFID-signalling that was acquired at substantially the same time; and provide stock-location-signalling based on the association between the stock-RFID-tag-identifiers and the antenna-location.

2. The system of claim 1, wherein the stock-location-signalling includes a location for each detected item of stock such that the location of those items of stock can be visually represented on a map of the warehouse.

3. The system of claim 1 or claim 2, wherein the items of static infrastructure in the warehouse comprise one or more of a post, a barrier, a racking leg, a post-cap, a gate post, and a shelf.

4. The system of any preceding claim, wherein the controller is configured to: process the RFID-signalling to determine a first-infrastructure-RFID-tag- identifier and a second-infrastructure-RFID-tag-identifier, which are associated with RFID tags that are associated with different items of static infrastructure in the warehouse; compare the signal strength of the RFID-tag-signal for the first infrastructure- RFID-tag-identifier with the signal strength of the RFID-tag-signal for the second infrastructure-RFID-tag-identifier in order to determine if the RFID antenna is closer to the RFID tag associated with the first infrastructure-RFID-tag-identifier or the RFID tag associated with the second infrastructure-RFID-tag-identifier; and provide the stock-location-signalling based on the comparison of the signal strengths.

5. The system of any preceding claim, wherein the system further comprises: a static sensor system that is attached to any stationary item of infrastructure in the warehouse, wherein the static sensor system comprises: a static RFID antenna at a known location in the warehouse, wherein the RFID antenna is configured to: transmit an RFID-scanning-signal to excite one or more RFID tags in the vicinity of the RFID antenna; and provide RFID-signalling that is representative of one or more RFID-tag-signals received from one or more RFID tags; and wherein the controller is configured to: process the RFID-signalling from the static RFID antenna to determine one or more stock-RFID-tag-identifiers that are associated with RFID tags that are associated with moveable items of stock; associate the stock-RFID-tag-identifiers determined from the RFID- signalling provided by the static RFID antenna with the known location of the static RFID antenna; and provide the stock-location-signalling based on the association between the stock-RFID-tag-identifiers determined from the RFID-signalling provided by the static RFID antenna and the known location of the static RFID antenna.

6. The system of any preceding claim, wherein the mobile sensor system further comprises a second RFID antenna, which is configured to: transmit a second RFID-scanning-signal to excite one or more RFID tags in the vicinity of the RFID antenna; and provide second-RFID-signalling that is representative of one or more RFID-tag- signals received from one or more RFID tags; and wherein the controller is further configured to: process the second RFID-signalling to determine one or more infrastructure- RFID-tag-identifiers that are associated with RFID tags that are associated with items of static infrastructure in the warehouse; determine a second-antenna-location based on the determined one or more infrastructure-RFID-tag-identifiers, wherein the second-antenna-location represents the location of the second RFID antenna in the warehouse when the second-RFID- signalling was acquired; process the second-RFID-signalling to determine one or more stock-RFID-tag- identifiers that are associated with RFID tags that are associated with moveable items of stock in the warehouse; associate the stock-RFID-tag-identifiers with the determined second-antenna- location for second-RFID-signalling that was acquired at substantially the same time; and provide the stock-location-signalling based on the association between the stock-RFID-tag-identifiers and the second-antenna-location.

7. The system of any preceding claim, wherein: the RFID antenna is configured to: provide subsequent RFID-signalling in response to subsequent transmission of an RFID-scanning-signal; and the controller is configured to: process the subsequent RFID-signalling to determine one or more subsequent infrastructure-RFID-tag-identifiers that are associated with RFID tags that are associated with items of static infrastructure in the warehouse; determine a subsequent antenna-location based on the determined one or more subsequent infrastructure-RFID-tag-identifiers, wherein the subsequent antenna-location represents the location of the RFID antenna in the warehouse when the subsequent RFID-signalling was acquired; process the subsequent RFID-signalling to determine one or more subsequent stock-RFID-tag-identifiers that are associated with RFID tags that are associated with moveable items of stock in the warehouse; associate the subsequent stock-RFID-tag-identifiers with the subsequent antenna-location for the subsequent RFID-signalling that was acquired at substantially the same time; and determine if the stock-RFID-tag-identifiers and the subsequent stock- RFID-tag-identifiers are associated with the same RFID tags but are associated with different antenna-locations, and if they are, then provide an output-signal that indicates that the movable items of stock that are associated with the RFID tags are in transit with the vehicle to which the mobile sensor system is attached.

8. The system of any preceding claim, wherein the controller is further configured to: control the RFID antenna such that it periodically transmits an RFID-scanning- signal.

9. The system of claim 8, wherein the controller is configured to set the period with which the RFID antenna transmits an RFID-scanning-signal based on the speed of the vehicle to which the mobile sensor system is attached.

10. The system of any preceding claim, wherein the RFID tags are passive.

11. The system of any preceding claim, wherein the controller is configured to: determine that an RFID-tag-signal is present in the RFID-signalling only if the

RFID-tag-signal has a signal strength that is greater than a threshold value.

12. A method of monitoring the location of stock in a warehouse, the method comprising: an RFID antenna that is attached to a vehicle that moves around the warehouse transmitting an RFID-scanning-signal to excite one or more RFID tags in the vicinity of the RFID antenna, and providing RFID-signalling that is representative of one or more RFID-tag-signals received from one or more RFID tags; processing the RFID-signalling to determine one or more infrastructure-RFID- tag-identifiers that are associated with RFID tags that are associated with items of static infrastructure in the warehouse; determining an antenna-location based on the determined one or more infrastructure-RFID-tag-identifiers, wherein the antenna-location represents the location of the RFID antenna in the warehouse when the RFID-signalling was acquired; processing the RFID-signalling to determine one or more stock-RFID-tag- identifiers that are associated with RFID tags that are associated with moveable items of stock in the warehouse; associating the stock-RFID-tag-identifiers with the determined antenna-location for RFID-signalling that was acquired at substantially the same time; and providing stock-location-signalling based on the association between the stock- RFID-tag-identifiers and the antenna-location.

13. A computer program configured to perform the method of claim 12.