Warehouse rack monitoring system and method

Abstract

The disclosure relates to a system and method for monitoring a warehouse rack assembly. Example embodiments include a rack monitoring system (301) for a warehouse rack assembly (100) comprising a plurality of support legs (1011a-8a, 1011b- 8b), the monitoring system (301) comprising: a distance sensor (302a, 302b) mounted at a first end of the rack assembly (100) and arranged to project a measurement light beam (303a, 303b) along a length of the rack assembly (100); a reflector (305a, 305b) mounted at a second end of the rack assembly (100) and positioned to receive the light beam (303a, 303b) from the distance sensor (302a, 302b); and a control module (304) connected to receive a distance measurement (da, db) from the distance sensor (302a, 302b) and configured to provide an alert signal (306) indicating movement of one of the support legs (1011a-8a, 1011b- 8b) transverse to the length of the rack assembly (100) if the distance measurement (da, db) differs from a predetermined distance measurement.

Description

[0001] WAREHOUSE RACK MONITORING SYSTEM AND METHOD

[0002] Field of the Invention

[0003] The invention relates to a system and method for monitoring a warehouse rack assembly.

[0004] Background

[0005] Rack assemblies are commonly used in warehouses to store large numbers of products within a minimal floor space, and may commonly contain products in palletised form. Such racks comprise vertical supports holding a number of shelves that can reach heights of six metres or more and have lengths that may be up to tens of metres.

[0006] With any type of racking assembly, there is a risk of collapse. This risk is greater as the height and load increase. Incorrect stacking of pallets, and collisions with forklifts, are two common causes of rack collapse. With increased rack lengths in larger warehouses, the risk of a collapse can result in greater damage, since a failure in a single support leg can result in a cascading failure of an entire rack assembly.

[0007] If, for example, a support leg on the rack assembly is damaged whilst under load, for example by an impact with a forklift, the downward pressure from pallets on the rack shelving may force the leg to buckle. The rack may then lose localised structural support, causing a knock-on effect on other support legs and collapse of the rack assembly. In warehouses, racks are often arranged in closely packed rows. If one rack collapses it may hit another rack, causing other racks to collapse, potentially resulting in a domino effect collapsing many racks. Such collapses cause a large loss of stock, and pose a serious and potentially fatal risk to workers in the warehouse.

[0008] Typical safety systems are installed in an attempt to prevent racks from being damaged. For example, barriers are commonly installed around the legs of racks to shield the legs from impacts with forklifts. However, such techniques do not prevent all collisions. A heavy forklift operated at speed may overcome the barrier, for example, and hit a leg of the rack. If such a collision occurs, it is likely that the rack will still collapse.

[0009] Other techniques may be used to either provide notification of potential damage to a rack assembly or to prevent collapse if a rack assembly is damaged. One possibility of notifying of potential damage is to monitor vibrations on the support legs of a rack assembly. Impacts on support legs above a certain threshold, which may be caused by collisions, may then be notified and action taken as appropriate. A problem with this approach is that such impacts may not necessarily result in damage and therefore may not be able to discriminate between potentially dangerous situations and vibrations during normal use. A further problem with such an approach is the multiple vibration sensing modules are required, preferably one on each support leg, which results in a complex and costly monitoring system.

[0010] One possible approach for preventing collapse in the event damage does occur is to provide support for the rack assembly. This may be achieved by using a plurality of support leg cables attached to a load bearing structure above the rack assembly, as disclosed in GB2554109B. This approach can be effective in preventing catastrophic collapse, but does not provide notification in advance of a potential collapse so that remedial action can be taken.

[0011] Summary of the Invention

[0012] In accordance with a first aspect, there is provided a rack monitoring system for a warehouse rack assembly comprising a plurality of support legs, the monitoring system comprising: a distance sensor mounted at a first end of the rack assembly and arranged to project a measurement light beam along a length of the rack assembly; a reflector mounted at a second end of the rack assembly and positioned to receive the light beam from the distance sensor; and a control module connected to receive a distance measurement from the distance sensor and configured to provide an alert signal indicating movement of one of the support legs transverse to the length of the rack assembly if the distance measurement differs from a predetermined distance measurement.

[0013] The distance sensor may be mounted to a first one of the plurality of support legs.

[0014] The reflector may be mounted to a second one of the plurality of support legs.

[0015] The rack assembly may comprise a first set of support legs on a first side of the rack assembly and a second set of support legs on a second opposing side of the rack assembly, the rack assembly comprising a plurality of shelves supported by the plurality of support legs.

[0016] The distance sensor may be a first distance sensor mounted on the first side of the rack assembly and the reflector a first reflector mounted on the first side of the rack assembly, the system further comprising a second distance sensor mounted on the second side of the rack assembly and a second reflector mounted on the second side of the rack assembly.

[0017] The control module may be connected to receive distance measurements from a plurality of distance sensors mounted to a respective plurality of rack assemblies.

[0018] The distance sensor may be a photoelectric laser distance sensor.

[0019] The control module may be configured to provide the alert signal with an indication identifying one of the plurality of support legs derived from dividing the measured distance by a distance between adjacent support legs of the rack assembly.

[0020] The control module may be configured to provide the alert signal if the measured distance differs from the predetermined distance for longer than a minimum threshold time.

[0021] According to a second aspect, there is provided a computer-implemented method for automatically monitoring a rack assembly comprising a plurality of support legs, the method comprising: receiving a distance measurement from a distance sensor mounted at a first end of the rack assembly and arranged to project a measurement light beam along a length of the rack assembly to a reflector mounted at a second end of the rack assembly and positioned to receive the light beam from the distance sensor; comparing the distance measurement to a predetermined distance measurement; and providing an alert signal indicating movement of one of the support legs transverse to the length of the rack assembly if the distance measurement differs from the predetermined distance measurement.

[0022] The distance measurement may be a first distance measurement, the distance sensor a first distance sensor mounted on a first side of the rack assembly, the measurement light beam a first measurement light beam and the reflector a first reflector mounted on a second side of the rack assembly, the method further comprising receiving a second distance measurement from a second distance sensor mounted on an opposing second side of the rack assembly and arranged to project a second measurement light beam along the length of the rack assembly to a second reflector mounted on the second side of the rack assembly and positioned to receive the second measurement light beam from the second distance sensor, the alert signal being provided if the first or second distance measurements differ from the predetermined distance measurement. The method may comprise receiving distance measurements from a plurality of distance sensors mounted to measure a distance along a respective plurality of rack assemblies.

[0023] The distance sensor may be a photoelectric laser distance sensor.

[0024] The alert signal may be provided with an indication identifying one of the plurality of support legs derived from dividing the measured distance by a distance between adjacent support legs of the rack assembly.

[0025] The alert signal may be provided if the measured distance differs from the predetermined distance for longer than a minimum threshold time.

[0026] According to a third aspect, there is provided a computer program comprising instructions for causing a computer to perform the method according to the second aspect. The computer program may be provided in the form of a computer-readable storage medium.

[0027] Detailed Description

[0028] The invention is described in further detail below by way of example and with reference to the accompanying drawings, in which: figure 1 is a schematic elevation view of an example warehouse rack assembly; figure 2a is a schematic plan view of an example warehouse rack assembly; figure 2b is a schematic plan view of the example warehouse rack assembly of figure 2a after a collision event; figure 3a is a schematic plan view of an example warehouse rack assembly incorporating a rack assembly monitoring system; figure 3b is a schematic plan view of the example warehouse rack assembly of figure 3a after a collision event; figure 4 is a flow diagram illustrating an example method of monitoring a rack assembly; figure 5 is a schematic diagram illustrating an example monitoring system for a plurality of rack assemblies in a warehouse; figure 6 is an example screenshot of a user interface for a rack monitoring system; and figure 7 is a further example screenshot of a user interface for a rack monitoring system for multiple warehouse rack systems.

[0029] Figure 1 illustrates in simplified form an example warehouse rack assembly 100. The visible side of the rack assembly 100 comprises a plurality of support legs 1011-5. A corresponding plurality of support legs are provided on an opposing side of the rack assembly 100. The support legs 1011-5 support a plurality of shelves 1021-7, on which items 103 may be stored. In a typical warehouse rack assembly 100 the items 103 are palletised for ease of placement and removal using a forklift.

[0030] Figure 2a illustrates a plan view of the example warehouse rack assembly 100, in this case with eight support legs on each side of the rack. A first set of support legs 101 ia-8a are on a left side of the rack assembly 100 and a second set of support legs 101 ib-8b are on a right side of the rack assembly 100. The stability of the rack assembly 100 depends primarily on the support legs remaining vertical and in position. If any of the support legs are moved out of position, for example due to a collision, the integrity of the entire structure can be compromised.

[0031] Figure 2b illustrates the rack assembly 100 upon being subjected to a collision, which results in a force 201 applied to the fourth right side support legs lOhb- This results in both of the fourth left and right hand support legs 10 ha, lOhb shifting leftwards. This distorts the shape of the rack assembly 100, as indicated by the dotted lines in figure 2b. Depending on how far the support legs lOha, lOUb are shifted, the collision could result in actual or potential collapse of the rack assembly 100. Even if the rack assembly 100 does not immediately collapse, a distortion resulting from the collision may result in a weakening of the structure that could result in later collapse, for example if additional loading is applied following the collision.

[0032] Given that any collision is more likely to be lower down on the rack assembly, the result of a collision as indicated in figure 2b may result initially in a leftward shift of the support legs lOha, 10 Ub, followed by the support legs lOha, lOUb moving back to their original position. If, however, the right hand support leg lOhb is damaged during the collision, both support legs 10 ha, lOhb may then shift back beyond their original positions, resulting in a permanent distortion of the rack assembly, with the fourth left and right hand support legs 10 I4a, 10 l4b shifted out of alignment with the other support legs. This potentially weakens the rack assembly 100 due to a bent part of one of the support legs not being capable of supporting the same load as before.

[0033] Figures 3a and 3b illustrate the rack assembly 100 with a monitoring system 301 in place for determining whether any of the support legs are out of alignment, which may indicate a potential weakening of the structure. The monitoring system 301 comprises first and second distance sensors 302a, 302b on respective first (left) and second (right) sides of the rack assembly 100. The first distance sensor 302a is mounted to a first one 101 iaof the left side support legs and the second distance sensor 302b is mounted to a first one 101n> of the right side support legs. In some examples, a single distance sensor may be provided, although a pair of distance sensors has an advantage of monitoring deflection of support legs in either direction. The distance sensors 302a, 302b may be alternatively mounted adjacent the rack assembly 100, for example on an wall or other structure next to the rack assembly 100.

[0034] The first and second distance sensors 302a, 302b are each arranged to project a measurement light beam 303a, 303b along a length of the rack assembly 100, i.e. in a direction parallel to a longitudinal axis 304 of the rack assembly 100. Each of the light beams 303a, 303b are directed towards respective reflectors 305a, 305b. The reflectors 305a, 305b are indicated extending transverse to the rack assembly 100 to allow the light beams 303a, 303b to measure a distance along the length of the rack assembly 100. The reflectors 305a, 305b are indicated as being mounted to a second one 10 I8a, 1018b of the left and right side support legs, which in this case is the eighth left and right side support legs 1018a, lOlsb- The reflectors 305a, 305b may alternatively be mounted adjacent the rack assembly, for example on a wall or other structure next to the rack assembly 100. In a practical implementation, the number of support legs may be greater or fewer than that shown. In an example implementation, a spacing between the support legs may be around 2 m and the number of support legs may be twelve or more, depending on the size of the warehouse in which the rack assembly 100 is located. In a typical implementation therefore, the total length of the rack assembly may be 22 m or more.

[0035] Each of the distance sensors 302a, 302b measure a respective distance da, (h to the closest object in the line of sight of each sensor, which in this case is the distance to the reflector 305a, 305b. On setting up the monitoring system 301, the initial measured distances da, db correspond to a nominal predetermined distance dnominai, which is the distance between the first and second left and right side support legs 101 ia, 101sa, 10 lib, lOhb- An offset may be applied to the measured distance to account for any difference in position between the mounting points of the sensors 302a, 302b and the corresponding reflectors 305a, 305b. Each measurement light beam 303a, 303b is positioned close to the intervening support legs between the first and second left and right side support legs while maintaining an unrestricted path between the distance sensors 302a, 302b and the respective reflector flags 305a, 305b. To avoid deflections due to normal use of the rack assembly from interfering with the light beams, the light beams 303a, 303b may be positioned to be a few cm away from the intervening support legs, for example between around 1 and 10 cm, between around 2 and 10 cm or between around 5 and 10 cm.

[0036] A control module 304 is connected to receive the distance measurements from the distance sensors 302a, 302b and is configured to provide an output alert signal 306 indicating movement of one or the support legs transverse to the length of the rack assembly if the distance measurement differs from a predetermined distance measurement. The control module 304 may be separated into a local module mounted in the vicinity of the rack assembly 100 and a remote monitoring unit that monitors the distance measurement and provides the alert signal. The alert signal 306 may trigger another action such as a siren or other type of alarm that indicates an actual or potential fault with the rack assembly 100.

[0037] Figure 3b illustrates schematically the effect of a collision on one of the support legs, in this case the fourth right side support leg lOhb, on the distance measurements da, h. The collision applies a force 201 to the support leg lOhb, causing both left and right side support legs 10 ha, lOhb to deflect leftwards. This does not affect the second measurement light beam 303b, which still indicates a distance (h as before the collision, but the first measurement light beam 303a is now interrupted by the left side support leg lOha, causing the first distance measurement dato be shortened. This will result in the control module 304 providing an alert signal indicating a fault with the rack assembly 100.

[0038] The second distance sensor 302b, being positioned on the right side of the right side support leg 101b, is able to detect a deflection in the opposite direction, i.e. if a collision results in a deflection of any of the intervening support legs to the right. In the example illustrated in figure 3, the first distance sensor 302a is mounted to a left side of the rack assembly 100 and the second distance sensor 302b is mounted to a right side of the rack assembly 100. In alternative examples, the first and second distance sensors 302a, 302b may be mounted to respective left and right sides of the same support leg, with the respective reflector flags 305a, 305b positioned accordingly.

[0039] In an example implementation, each of the distance sensors 302a, 302b may be a photoelectric laser distance sensor such as the efector200(R) distance sensor, model number O ID 106, having a measuring range of up to 75 m. The control module 304 may be partly implemented with a Raspberry Pi module such as the RevPi Connect 4 from Revolution PI. Multiple distance sensors may be connected to a common control module using an expansion module such as the Revolution PI series expansion module. Data may be transmitted to a remote monitor via an Ethernet connection on the Raspberry Pi module.

[0040] Figure 4 illustrates a flow diagram of a method for monitoring the rack assembly 100. In a first step 401, a distance is measured between first and second ones of the plurality of support legs with a distance sensor mounted to a first one of the plurality of support legs and projecting a measurement light beam along a length of the rack assembly to a reflector flag mounted to a second one of the plurality of support legs and position to receive the light beam. A comparison is made at step 402 as to whether the measured distance d is equal to a nominal predetermined distance dnominai. The comparison step 402 may for example compare whether the measured distance is within a specified tolerance of the nominal predetermined distance, which may for example be + / -10%.

[0041] If, at step 402, the measured distance is equal to, or within the specified tolerance of, the nominal predetermined distance, the process repeats by returning to step 401. If, however, the measured distance is not equal to the predetermined distance, an output alert is provided at step 403. The output alert may provide an identification of the rack, which allows a user to identify the affected rack if multiple rack assemblies are being monitored simultaneously. The output may in some examples provide an indication of the support leg affected, which may be readily determined by dividing the measured distance by the known distance between adjacent support legs and providing the closest integer as an output leg number. For example, for the example provided in figure 3, if the distance between adjacent support legs is 2 m, the distance measured by the first distance sensor 302a in figure 3b will be around 6 m. The control module 304 may therefore identify the fourth left side support leg 10 Da by outputting Int(<7a / / )+l, where di is the distance between adjacent support legs. To prevent temporary deflections causing an alert to be provided, for example due to normal movements of the rack assembly during loading or unloading operations, the output alert may be provided only if the measured distance differs from the predetermined distance for longer than a minimum threshold time. The minimum threshold time may for example be longer than 30 seconds, 1 minute or more. This additional check confirms that the change in distance corresponds to a more permanent deflection of the rack assembly, which may require inspection.

[0042] Figure 5 illustrates schematically an example monitoring system 500 in which a plurality of rack assemblies 501a-f are located in a warehouse 502. Each of the rack assemblies is fitted with one or more distance sensors and corresponding reflector flags, as described above, the distance sensors providing distance measurements to a respective controller 504a-f. The controllers 504a-f relay these distance measurements to a remote monitoring unit 506 via a local hub 505 and a network 507, e.g. the internet. The remote monitoring unit 506 can then collate and present distance information and corresponding alerts for the plurality of rack assemblies 501a-f. The remote monitoring unit 506 may also receive distance measurements from distance sensors in other warehouses with similar measurement systems in place. The remote monitoring unit 506 may be accessible via a web interface on a computer, for example via an application on a handheld portable electronic device such as a mobile phone. A user may then receive information and alerts of rack assemblies in multiple locations regardless of their own location.

[0043] Figure 6 is an example screenshot of a user interface presented by a control module via a web interface, which illustrates an output from an example monitoring system arranged to monitor a plurality of rack assemblies in a common warehouse (“Redditch Warehouse 1” in this example). Example alerts 601a-e are indicated for various rows, corresponding to different rack assemblies, in the warehouse. In each case, the alerts 601a-e indicate that a measured distance is less than expected. Other measurements are within a predetermined tolerance of an expected length, which in this example is 75.22 m. Measurements are taken at intervals of between 1 and 2 minutes, resulting in alerts being repeated until they are resolved. The user interface presents an option 602a, 602b of taking action in response to the alerts, in this example relating to rows 2 and 4, where the measured length of 71.46 m and 70.21 m respectively is less than expected. The user may then take action by, for example, indicating that the measurement is correct or by inspecting and the rack assembly indicated and either adjusting the monitoring system or identifying a fault in the rack assembly. As illustrated in Figure 7, the control module may further present a user interface for multiple warehouses, indicating in this case that an alert is raised for one of the warehouses, details of which are indicated in Figure 6. The monitoring system may thereby provide a monitoring ability of multiple warehouse rack systems, enabling a saving in time and resources.

[0044] The above described method of monitoring a rack assembly may be implemented by a computer program, which may be executed on a computer connected to receive measurement signals from one or more distance measurement sensors in one or more warehouses. The computer may be remote from the warehouse, for example implemented on a cloud-based server, and may be implemented to allow for remote monitoring of multiple rack assemblies in multiple warehouses, as illustrated in Figure 7. In alternative implementations, the computer may be located within the warehouse to provide local monitoring of one or more rack assemblies and provide an alert signal as required. Other embodiments are intentionally within the scope of the invention as defined by the appended claims.

Claims

CLAIMS1. A rack monitoring system for a warehouse rack assembly comprising a plurality of support legs, the monitoring system comprising: a distance sensor mounted at a first end of the rack assembly and arranged to project a measurement light beam along a length of the rack assembly; a reflector mounted at a second end of the rack assembly and positioned to receive the light beam from the distance sensor; and a control module connected to receive a distance measurement from the distance sensor and configured to provide an alert signal indicating movement of one of the support legs transverse to the length of the rack assembly if the distance measurement differs from a predetermined distance measurement.

2. The rack monitoring system of claim 1, wherein the distance sensor is mounted to a first one of the plurality of support legs.

3. The rack monitoring system of claim 1 or claim 2, wherein the reflector is mounted to a second one of the plurality of support legs.

4. The rack monitoring system of any preceding claim, wherein the rack assembly comprises a first set of support legs on a first side of the rack assembly and a second set of support legs on a second opposing side of the rack assembly, the rack assembly comprising a plurality of shelves supported by the plurality of support legs.

5. The rack monitoring system of claim 4, wherein the distance sensor is a first distance sensor mounted on the first side of the rack assembly and the reflector is a first reflector mounted on the first side of the rack assembly, the system further comprising a second distance sensor mounted on the second side of the rack assembly and a second reflector mounted on the second side of the rack assembly.

6. The rack monitoring system of any preceding claim, wherein the control module is connected to receive distance measurements from a plurality of distance sensors mounted to a respective plurality of rack assemblies.

7. The rack monitoring system of any preceding claim, wherein the distance sensor is a photoelectric laser distance sensor.

8. The rack monitoring system of any preceding claim, wherein the control module is configured to provide the alert signal with an indication identifying one of the plurality of support legs derived from dividing the measured distance by a distance between adjacent support legs of the rack assembly.

9. The rack monitoring system of any preceding claim, wherein the control module is configured to provide the alert signal if the measured distance differs from the predetermined distance for longer than a minimum threshold time.

10. A computer-implemented method for automatically monitoring a rack assembly comprising a plurality of support legs, the method comprising: receiving a distance measurement from a distance sensor mounted at a first end of the rack assembly and arranged to project a measurement light beam along a length of the rack assembly to a reflector mounted at a second end of the rack assembly and positioned to receive the light beam from the distance sensor; comparing the distance measurement to a predetermined distance measurement; and providing an alert signal indicating movement of one of the support legs transverse to the length of the rack assembly if the distance measurement differs from the predetermined distance measurement.

11. The method of claim 10, wherein the distance measurement is a first distance measurement, the distance sensor is a first distance sensor mounted on a first side of the rack assembly, the measurement light beam is a first measurement light beam and the reflector is a first reflector mounted on a second side of the rack assembly, the method further comprising receiving a second distance measurement from a second distance sensor mounted on an opposing second side of the rack assembly and arranged to project a second measurement light beam along the length of the rack assembly to a second reflector mounted on the second side of the rack assembly and positioned to receive the second measurement light beam from the second distance sensor, the alert signal being provided if the first or second distance measurements differ from the predetermined distance measurement.

12. The method of claim 10 or claim 11, comprising receiving distance measurements from a plurality of distance sensors mounted to measure a distance along a respective plurality of rack assemblies.

13. The method of any one of claims 10 to 12, wherein the distance sensor is a photoelectric laser distance sensor.

14. The method of any one of claims 10 to 13, wherein the alert signal is provided with an indication identifying one of the plurality of support legs derived from dividing the measured distance by a distance between adjacent support legs of the rack assembly.

15. The method of any one of claims 10 to 14, wherein the alert signal is provided if the measured distance differs from the predetermined distance for longer than a minimum threshold time.

16. A computer program comprising instructions for causing a computer to perform the method according to any one of claims 10 to 15.

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