Method and system for determining gripper assembly depth or obstruction - Patents.com

Abstract

A method and system for determining the depth or obstruction of a container gripping assembly is disclosed.The method and system uses a sensor to determine the depth or obstruction of a container gripping assembly.

Description

[Technical Field]

[0001] The present invention relates to a method and system for determining the depth of a gripper assembly such as that used in a load handling device. [Background technology]

[0002]

[0003] Several commercial and industrial activities require systems that allow for the storage and retrieval of a large number of different products. WO2015 / 185628A describes a storage and fulfillment system in which stacks of storage containers are arranged within a grid framework structure. The containers are accessed from above by load handling devices that operate on rails or tracks located at the top of the grid storage structure. Load handling devices are further described in WO2015 / 019055A1.

[0003] The load handling device includes a container lifting assembly that uses a lifting assembly to raise and / or lower the container gripping assembly. The lifting assembly controls the raising and lowering of the container gripping assembly according to the vertical position of the container gripping assembly. For example, as the container gripping assembly is lowered and approaches a container, the container gripping assembly slows down. In order to control the deceleration, it is important to accurately determine the vertical position of the container gripping assembly, as well as when the container gripping assembly is raised and approaches the load handling device. It is also important to determine whether the container gripping assembly is obstructed during the raising and lowering process. It is against this background that the present invention has been devised. Summary of the Invention

[0004] In a first aspect, there is a lifting assembly for raising and / or lowering a container from and / or to a stack of containers in a grid storage structure, the lifting assembly comprising: a gripping assembly configured to grip a load; and a lifting assembly configured to lift and lower the gripping assembly, the lifting assembly comprising: at least one tether connected to the gripping assembly; a motor for winding and / or unwinding the or each tether to raise and / or lower the gripping assembly, wherein the lifting assembly further comprises: a sensor configured to detect movement of the gripper assembly, wherein the sensor comprises: an input engaged by movement of the gripper assembly; and a controller configured to use the output of the sensor to determine the vertical position of the gripper assembly, meaning that the extent to which the gripper assembly has been raised and / or lowered can be monitored.

[0005] The lifting assembly may include an electric cable connected to the gripping assembly, where the electric cable is configured to reel in and / or unreel in as the gripping assembly is raised and / or lowered, and where the sensor is configured to detect the extent to which the electric cable has been reeled in and / or unreeled. This means that a direct extension of the electric cable can be used to accurately determine the vertical position. In one implementation, the lifting assembly further includes an electric cable spool about which the electric cable is reeled in and / or unreeled, and where the sensor comprises a rotational encoder configured to engage with the electric cable spool to detect the extent to which the electric cable spool has rotated as the electric cable is reeled in and / or unreeled.

[0006] The electrical cable may have a higher modulus of elasticity than the or each tether, which means that the effects of stretching are reduced and precision is maximised.

[0007] The lifting assembly may further comprise a tether spool for the or each tether onto which the or each tether is wound and / or unwound, wherein the electric cable spool and the or each tether spool are mounted on a shaft such that the electric cable spool can rotate relative to the or each tether spool. In one implementation, the claimed lifting assembly further comprises a biasing assembly configured to oppose the unwinding of the electric cable spool or the winding of the electric cable spool so that the electric cable is tensioned between the lifting assembly and the gripping assembly. This means that the electric cable remains taut, maximizing precision.

[0008] An electrical cable may communicate electrical signals to the gripping assembly. The electrical cable may comprise a flat fixed flexible cable, FFC, or ribbon cable.

[0009] The sensor may include a motor encoder for the motor, where the motor encoder is configured to detect the extent to which the or each tether is wound and / or unwound. This means that a direct extension of the or each tether can be used to accurately determine vertical position. In one implementation, the lifting assembly may further include a tether spool for the or each tether onto which the or each tether is wound and / or unwound, where the motor encoder detects the extent to which the or each tether spool rotates as the or each tether is wound and / or unwound. The sensor may include a rotational encoder configured to detect the extent to which the or each tether is wound and / or unwound, or a rotational encoder for the or each tether, where the or each rotational encoder is configured to engage with the or each spool to detect the extent to which the or each spool rotates as the or each respective tether is wound and / or unwound.

[0010] The sensor may comprise a rotary encoder for the or each tether, wherein the rotary encoder is configured to contact the respective tether such that winding and / or unwinding of the or each respective tether rotates the input of the rotary encoder, meaning that a direct extension of the tether can be used to accurately determine vertical position.

[0011] The lifting assembly may comprise an electrical cable connected to the gripping assembly, wherein the electrical cable is configured to wind and / or unwind as the gripping assembly is raised and / or lowered, and the sensor may comprise a rotary encoder configured to engage the electrical cable such that winding and / or unwinding of the or each tether rotates a shaft of the rotary encoder. This means that a direct extension of the electrical cable can be used to accurately determine vertical position.

[0012] The lifting assembly may further comprise a biasing assembly configured to bias the or each rotary encoder into contact with the or each respective tether or electrical cable, thereby ensuring that the rotary encoder maintains contact with each respective tether or electrical cable.

[0013] The lifting assembly may comprise an electric wire connected to the gripping device, wherein the electric wire is configured to be wound and / or unwound as the gripping assembly is raised and / or lowered, and an electric wire spool onto which the electric wire is wound and / or unwound, wherein the electric wire is wound onto the electric wire spool such that the electric wire on the wire spool is short-circuited, and wherein the sensor may be configured to measure the electrical resistance of the electric wire as it is wound and / or unwound. This means that a direct extension of the electric wire can be used to accurately determine the vertical position.

[0014] The lifting assembly may further comprise a biasing assembly configured to oppose the unwinding of the wire spool or the winding of the wire spool so that the wire is tensioned between the lifting assembly and the gripping assembly, meaning that the wire remains taut and precision is maximized.

[0015] The sensors may comprise time-of-flight, ToF, sensors, which means that direct movement of the gripping assembly can be used to accurately determine vertical position.

[0016] The sensor may include a light source and a photodetector, where the light source is configured to transmit an optical signal onto a surface that moves as the gripping assembly is raised and / or lowered, and the photodetector is configured to detect reflection of the optical signal from the surface to detect movement of the surface. This means that direct movement of the gripping assembly can be used to accurately determine vertical position. In one implementation, the lifting assembly may include an electric cable connected to the gripping assembly, where the electric cable is configured to be wound and / or unwound as the gripping assembly is raised and / or lowered. The lifting assembly may include a wheel that contacts the or each respective tether spool or electric cable spool about which the electric cable is wound and / or unwound, where the wheel includes a surface. The or each tether spool or electric cable spool may include a surface.

[0017] The controller may be configured to use the determined vertical position to control / adjust the raising and / or lowering of the gripping assembly, which means that the gripping assembly can be precisely controlled using feedback.

[0018] In another aspect, there is a load handling device for lifting and moving storage containers stacked in a grid framework structure; a first set of parallel rails or tracks and a second set of parallel rails or tracks extending substantially perpendicular to the first set of rails or tracks in a substantially horizontal plane to form a grid pattern comprising a plurality of grid spaces, wherein the grid is supported by a set of uprights to form a plurality of vertical storage locations beneath the grid such that containers are stacked between and guided by the uprights vertically through the plurality of grid spaces; a body or skeleton attached to a first set of wheels arranged to engage the first set of parallel tracks and a second set of wheels arranged to engage the second set of parallel tracks; a container lifting assembly comprising the lifting assembly of any preceding aspect, wherein the gripping assembly comprises a container gripping assembly configured to grip a container.

[0019] In another aspect, there is a method for determining a vertical position of a gripper assembly of a lifting assembly of any preceding aspect, wherein the method includes: using a motor to raise and / or lower the gripper assembly; and using a controller to determine a vertical position of the gripper assembly using an output of the sensor.

[0020] In another aspect there is a computer program comprising instructions which, when executed by a computer, cause the computer to perform the method of the previous aspect.

[0021] In an aspect, there is a lifting assembly for raising and / or lowering a container from and / or to a stack of containers in the grid storage structure, the lifting assembly comprising: a gripping assembly configured to grip a load; and a lifting assembly configured to lift and lower the gripping assembly, the lifting assembly comprising: at least one tether connected to the gripping assembly; a motor configured to wind and / or unwind the or each tether about at least one shaft to raise and / or lower the gripping assembly, wherein the lifting assembly further comprises: a sensor configured to detect movement of the gripper assembly; and a controller configured to determine a fault in the gripper assembly if the current output of the sensor does not correlate with the winding and / or unwinding of the or each tether around the or each shaft to raise and / or lower the gripper assembly. This means that malfunctions or incorrect movements during the raising and / or lowering of the gripper assembly can be detected.

[0022] The lifting assembly of claim 1 further comprises a second sensor, wherein the second sensor directly detects rotation of the at least one shaft, meaning that it can detect winding and / or unwinding of the or each tether.

[0023] In one implementation, the second sensor may comprise a motor encoder of the motor, wherein the controller may be configured to determine a gripper assembly failure when a current output of the sensor does not correlate with a current output of the motor encoder. The controller may be configured to determine a grid assembly failure when the current output of the sensor does not correlate with a current output of the motor encoder by a threshold value. This means that a tolerance is allowed to account for stretching of the or each tether.

[0024] In another implementation, the lifting assembly may further include a tether spool for the or each tether onto which the or each tether is wound and / or unwound, and wherein the second sensor may include a tether rotation encoder for the or each tether spool, and wherein the or each tether rotation encoder may be configured to engage with the or each spool to detect the degree to which the or each spool has rotated as the or each tether is wound and / or unwound, and wherein the controller is configured to determine a fault in the gripper assembly if the current output of the sensor does not correlate with the current output of the or each tether rotation encoder. The controller may be configured to determine a fault in the gripper assembly if the current output of the sensor does not correlate with the current output of the tether rotation encoder by a threshold value, meaning that a tolerance is allowed to account for stretching of the or each tether.

[0025] In another implementation, the lifting assembly may include an electric cable connected to the gripping assembly, wherein the electric cable is configured to reel in and / or unreel as the gripping assembly is raised and / or lowered, and an electric cable spool about which the electric cable reels in and / or unreels, wherein the electric cable spool is fixedly mounted to the or each shaft, wherein the second sensor includes an electric cable rotational encoder for the electric cable spool, wherein the or each electric cable rotational encoder is configured to engage the electric cable spool to detect the extent to which the electric cable spool has rotated as the electric cable reels in and / or unreels, and wherein the controller is configured to determine a fault in the gripping assembly if a current output of the sensor does not correlate with a current output of the electric cable rotational encoder.

[0026] In another implementation, the lifting assembly may further comprise a tether spool for the or each tether onto which the tether is wound and / or unwound, and wherein the second sensor comprises a tether spool sensor comprising a light source and a light detector, wherein the light source is configured to transmit a light signal onto a surface that moves as the gripping assembly is raised and / or lowered, and wherein the light detector is configured to detect reflection of the light signal from the surface to detect movement of the surface, and wherein the controller is configured to determine a fault in the gripping assembly if a current output of the sensor does not correlate with a current output of the tether spool sensor. The lifting assembly may comprise a wheel in contact with the or each respective tether spool onto which the tether is wound and / or unwound, and wherein the wheel comprises a surface. The or each tether spool may comprise a surface.

[0027] In another implementation, the lifting assembly may include an electric cable connected to the gripping assembly, wherein the electric cable is configured to reel in and / or unreel when the gripping assembly is raised and / or lowered, and an electric cable spool about which the electric cable is reeled and / or unreeled, wherein the second sensor includes an electric cable spool sensor including a light source and a light detector, wherein the light source is configured to transmit an optical signal onto a surface that moves when the gripping assembly is raised and / or lowered, and the light detector is configured to detect reflection of the optical signal from the surface to detect movement of the surface, wherein the controller is configured to determine a fault in the gripping assembly if a current output of the sensor does not correlate with a current output of the electric cable spool sensor. The lifting assembly may include a wheel that contacts the electric cable spool about which the electric cable is reeled and / or unreeled, wherein the wheel comprises the surface. The electric cable spool may comprise the surface.

[0028] The sensor may have an input engaged by movement of the gripper assembly, wherein the controller may be configured to receive a motion profile controlling the raising and / or lowering of the gripper assembly, use the output of the sensor to determine a vertical position of the gripper assembly, and determine a fault in the gripper assembly if the vertical position of the gripper assembly at the current time does not correlate with a corresponding vertical position derived from the motion profile by a threshold value. This means that a single sensor can be used to determine a fault.

[0029] The lifting assembly may include an electric cable connected to the gripping assembly, where the electric cable may be configured to be wound and / or unwound as the gripping assembly is raised and / or lowered, where the sensor may be configured to detect the extent to which the electric cable is wound and / or unwound, and the biasing assembly may be configured to oppose the unwinding of the electric cable spool or the reeling of the electric cable spool so that the electric cable is tensioned between the lifting assembly and the gripping assembly. The lifting assembly may further include an electric cable spool about which the electric cable is wound and / or unwound, where the sensor may include a rotary encoder configured to engage with the electric cable spool to detect the extent to which the electric cable spool is rotated as the electric cable is wound and / or unwound, and where the electric cable spool may be configured to rotate relative to the or each shaft. This means that the electric cable returns to its biased state when movement of the gripping assembly is prevented, which is detected by the rotary encoder. In one implementation, the electrical cable may have a higher modulus of elasticity than the or each tether. In another implementation, the electrical cable may communicate electrical signals to the gripping assembly. In another implementation, the electrical cable may comprise a flat flexible cable, FFC, or ribbon cable.

[0030] The sensor may comprise a rotary encoder for the or each tether, wherein the rotary encoder is configured to contact the respective tether such that winding and / or unwinding of the or each respective tether rotates the input of the rotary encoder. The lifting assembly may comprise an electrical cable connected to the gripping assembly, wherein the electrical cable is configured to wind and / or unwind as the gripping mechanism is raised and / or lowered, wherein the electrical cable optionally comprises a flat flexible cable, FFC, or ribbon cable, wherein the sensor may comprise a rotary encoder, wherein the rotary encoder may be configured to engage the electrical cable such that winding and / or unwinding of the or each tether rotates a shaft of the rotary encoder. This means that loss of contact between the rotary encoder and the or each tether or electrical cable, for example due to slack, is detected by the rotary encoder. A biasing assembly may be configured to bias the or each rotary encoder into contact with the or each respective tether or electrical cable. This ensures good contact between the rotary encoder and the or each respective tether or electrical cable.

[0031] The lifting assembly comprises an electric cable connected to the gripping assembly, wherein the electric cable is configured to reel in and / or unreel when the gripping assembly is raised and / or lowered; an electric cable spool about which the electric cable is reeled in and / or unreeled; wherein the electric cable spool is configured to rotate relative to the or each shaft; and a biasing assembly configured to oppose the reeling in or unreeling of the electric cable spool so that the electric cable is tensioned between the lifting assembly and the gripping assembly; wherein the sensor comprises an electric cable spool sensor comprising a light source and a light detector, wherein the light source is configured to transmit an optical signal to a surface that moves when the gripping assembly is raised and / or lowered, and the light detector is configured to detect reflection of the optical signal from the surface to detect movement of the surface; and wherein the lifting assembly may comprise a wheel in contact with the electric cable spool about which the or each respective tether is reeled in and / or unreeled, wherein the wheel may comprise the surface, or wherein the electric cable spool may comprise the surface. This means that the electrical cable will return to its biased state when movement of the gripper assembly is prevented, which is detected by the electrical cable spool sensor.

[0032] The lifting assembly may comprise an electric wire connected to the gripping device, wherein the electric wire is configured to be wound and / or unwound when the gripping assembly is raised and / or lowered, an electric wire spool onto which the electric wire is wound and / or unwound, wherein the electric wire is wound onto the electric wire spool such that the electric wire on the wire spool is short-circuited, wherein the electric wire spool is configured to rotate relative to the or each shaft, and a biasing assembly configured to oppose the unwinding or rewinding of the electric wire spool so that the electric wire is tensioned between the lifting assembly and the gripping assembly, wherein the sensor is configured to measure the electrical resistance of the electric wire as it is wound and / or unwound, meaning that when movement of the gripping assembly is prevented, the electric wire returns to its biased state, which is detected by the sensor.

[0033] The sensor may comprise a time-of-flight, ToF, sensor, which detects when movement of the gripper assembly is impeded.

[0034] The controller may be configured to stop the motor upon determining a failure of the gripper assembly, which means that unwinding of the otherwise slack tether is prevented.

[0035] In another aspect, there is a load handling device for lifting and moving storage containers stacked in a grid framework structure; a first set of parallel rails or tracks and a second set of parallel rails or tracks extending substantially perpendicular to the first set of rails or tracks in a substantially horizontal plane to form a grid pattern comprising a plurality of grid spaces, wherein the grid is supported by a set of uprights to form a plurality of vertical storage locations beneath the grid such that containers are stacked between and guided by the uprights vertically through the plurality of grid spaces; a body or skeleton attached to a first set of wheels arranged to engage the first set of parallel tracks and a second set of wheels arranged to engage the second set of parallel tracks; a container lifting assembly comprising the lifting assembly of any preceding aspect, wherein the gripping assembly comprises a container gripping assembly configured to releasably grip a container.

[0036] In another aspect, there is a method of determining an obstruction to a gripper assembly of a lifting assembly of any preceding aspect, wherein the method includes: using a motor to raise and / or lower the gripper assembly; and using the controller to determine a fault in the gripping assembly if the current output of the sensor does not correlate with the winding and / or unwinding of the or each tether around the or each shaft to raise and / or lower the gripping assembly.

[0037] In another aspect there is a computer program comprising instructions which, when executed by a computer, cause the computer to perform the method of the preceding aspect. [Brief explanation of the drawings]

[0038] The present invention will now be described with reference to one or more exemplary embodiments thereof as illustrated in the accompanying drawings. [Figure 1] FIG. 1 shows the storage structure and container. [Figure 2] FIG. 2 shows the track on top of the storage structure shown in FIG. [Figure 3] FIG. 3 shows a load handling device on top of the storage structure illustrated in FIG. [Figure 4] Figure 4 shows a single load handling device with the container lifting means in a lowered configuration. [Figure 5A]Figure 5A shows a cutaway view of a single load handling device with the container lifting means in a raised configuration. [Figure 5B] Figure 5B shows a cutaway view of a single load handling device with the container lifting means in a lowered configuration. [Figure 6] [Figure 7] FIG. 7 illustrates a method according to the invention. [Figure 8] FIG. 8 shows a system according to the invention. [Figure 9] FIG. 9 shows a system according to the invention. [Figure 10] FIG. 10 shows a system according to the invention. [Figure 11A] FIG. 11A shows a sensor according to the present invention. [Figure 11B] FIG. 11B shows a sensor according to the present invention. [Figure 12] FIG. 12 shows another sensor according to the present invention. [Figure 13] FIG. 13 shows another sensor according to the present invention. [Figure 14] FIG. 14 shows another sensor according to the present invention. [Figure 15] FIG. 15 shows another sensor according to the present invention. [Figure 16] FIG. 16 shows a system according to the present invention. [Figure 17] FIG. 17 illustrates a method according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0039] Online retail businesses that sell multiple product lines, such as online grocery stores and supermarkets, require systems that can store tens of thousands, or even hundreds of thousands, of different product lines. The use of a single product stack in such cases is impractical because a very large floor area would be required to accommodate all of the required stacks. Furthermore, it may be desirable to store smaller quantities of some items, such as perishable or infrequently ordered items, making a single product stack an inefficient solution.

[0040] International Patent Application WO98 / 049075A (Autostore), the contents of which are incorporated herein by reference, describes a system in which a multi-product stack of containers is arranged within a frame structure.

[0041] PCT Publication No. WO2015 / 185628A (Ocado) describes a further known storage and fulfilment system in which stacks of containers are arranged within a grid framework structure (or grid storage structure). The containers are accessed by one or more load handling devices, otherwise known as "bots", operable on trucks located on top of the grid framework structure. A system of this type is illustrated schematically in Figures 1 to 3 of the accompanying drawings.

[0042] As shown in FIGS. 1 and 2, stackable containers 10, also known as "bins," are stacked on top of one another to form stacks 12. The stacks 12 are arranged within a grid framework structure 14 in a warehousing or manufacturing environment. The grid framework 14 is made up of a plurality of storage columns, or grid columns. Each grid within the grid framework structure has at least one grid column for storing a stack of containers. FIG. 1 is a schematic perspective view of the grid framework structure 14, and FIG. 2 is a schematic top view showing a stack 12 of bins 10 arranged within the framework structure 14. Each bin 10 typically holds multiple product items (not shown). The product items within the bins 10 may be the same product type or different product types, depending on the application.

[0043] The grid framework structure 14 includes a plurality of uprights 16 supporting horizontal members 18, 20. A first set of parallel horizontal members 18 are arranged perpendicular to a second set of parallel horizontal members 20 in a grid pattern to form a horizontal grid structure 15 supported by the uprights 16. The members 16, 18, 20 are typically fabricated from metal. The bins 10 are stacked between the members 16, 18, 20 of the grid framework structure 14 such that the grid framework structure 14 guards the stack 12 of bins 10 against horizontal movement and guides the vertical movement of the bins 10.

[0044] The top level of the grid framework structure 14 comprises a grid or grid structure 15 including rails 22 arranged in a grid pattern across the top of the stacks 12. Referring to FIG. 3 , the rails or tracks 22 guide a plurality of load handling devices 30. A first set 22a of parallel rails 22 guides movement of the robotic load handling devices 30 in a first direction (e.g., X direction) across the top of the grid framework structure 14. A second set 22b of parallel rails 22, positioned perpendicular to the first set 22a, guides movement of the load handling devices 30 in a second direction (e.g., Y direction) perpendicular to the first direction. In this manner, the rails 22 allow the robotic load handling devices 30 to move laterally in two dimensions within the horizontal XY plane. The load handling devices 30 can be moved to a position above any of the stacks 12.

[0045] 4, 5A and 5B—a known form of load handling device 30 is described in PCT Patent Publication No. WO2015 / 019055 (Ocado), which is incorporated herein by reference—wherein each load handling device 30 covers a single grid space of the grid framework structure 14. This configuration allows for a higher density of load handlers and therefore a higher throughput for a system of a given size.

[0046] The load handling device 30 includes a vehicle 32 arranged to travel on the rails 22 of the frame structure 14. A first set of wheels 34, consisting of a pair of wheels 34 at the front of the vehicle 32 and a pair of wheels 34 at the rear of the vehicle 32, are arranged to engage two adjacent rails of the first set 22a of rails 22. Similarly, a second set of wheels 36, consisting of a pair of wheels 36 on each side of the vehicle 32, are arranged to engage two adjacent rails of the second set 22b of rails 22. Each set of wheels 34, 36 can be raised and lowered via a diverting assembly so that either the first set of wheels 34 or the second set of wheels 36 is always engaged with the respective set of rails 22a, 22b. For example, when a first set of wheels 34 is engaged with a first set of rails 22a and a second set of wheels 36 is fully lifted off of the rails 22, the first set of wheels 34 can be driven via a drive assembly housed in the vehicle 32 to move the load handling device 30 in the X direction. To achieve movement in the Y direction, the first set of wheels 34 is lifted off of the rails 22 and the second set of wheels 36 is lowered and engaged with the second set 22b of the rails 22. The drive assembly can then be used to drive the second set of wheels 36 to move the load handling device 30 in the Y direction.

[0047] The load handling device 30 is equipped with a container lifting device, e.g., a crane mechanism, for lifting a storage container from above. The container lifting assembly includes a lifting assembly (an example of which is shown in FIG. 9 ) having a winch tether or cable 38 wound on a spool or reel, and a container gripping assembly 39. The lifting assembly also includes a motor for rotating the spool and thus winding and / or unwinding the tether. The lifting assembly shown in FIG. 4 includes a set of four vertically extending lifting tethers 38. The tethers 38 are connected to or near each of the four corners of the container gripping assembly 39, e.g., a lifting frame, for releasable connection to the storage container 10. For example, each tether 38 is positioned at or near each of the four corners of the container gripping assembly 39. The container gripping assembly 39 is configured to releasably grip the top of the storage container 10 to lift the storage container 10 from a stack of containers in a storage system of the type shown in FIGS. 1 and 2 . For example, the container gripping assembly 39 may include pins (not shown) that mate with corresponding holes (not shown) in a rim forming the top surface of the bin 10, and a sliding clip (not shown) that is engageable with the rim to grip the bin 10. The clip is driven into engagement with the bin 10 by a suitable drive mechanism housed within the container gripping assembly 39, which drive mechanism is powered and controlled by signals carried through the cable 38 itself or a separate control cable (not shown).

[0048] To remove a bin 10 from the top of the stack 12, the load handling device 30 is first moved in the X and Y directions to position the container gripping assembly 39 above the stack 12. The container gripping assembly is then lowered vertically in the Z direction by raising and / or lowering the assembly to engage the bin 10 on the top of the stack 12, as shown in FIGS. 4 and 5B. The container gripping assembly 39 grasps the bin 10 and is then pulled upward by the cable 38 with the bin 10 attached. At the top of its vertical movement, the bin 10 is held above the rails 22 housed within the vehicle body 32. In this manner, the load handling device 30 can be moved to different positions in the XY plane, carrying the bin 10 with it, to transport the bin 10 to another location. Upon reaching the target location (e.g., another stack 12, an access point in a storage system, or a conveyor belt), the bin or container 10 may be lowered from the container receiving portion and released from the container gripping assembly 39. The cable 38 is long enough to allow the load handling device 30 to pick and place bins from any level of the stack 12, including the floor level.

[0049] As shown in Figure 3, multiple identical load handling devices 30 may be provided, each capable of operating simultaneously to increase system throughput. The system illustrated in Figure 3 may include specific locations known as ports, where bins 10 may be transported into or out of the system. Each port may have an additional conveyor system (not shown) associated with it, so that bins 10 transported to the port by the load handling device 30 may be transported by the conveyor system to another location, e.g., a picking station (not shown). Similarly, bins 10 may be moved by the conveyor system from an external location, e.g., a bottling station (not shown), to the port 24, where they may be transported by the load handling device 30 to the stacks 12 to replenish stock in the system.

[0050] Each load handling device 30 can lift and move one bin 10 at a time. The load handling devices 30 have a container-receiving cavity or recess 40 at their bottom. The recess 40 is sized to accommodate the container 10 when lifted by the lifting mechanism, as shown in FIGS. 5A and 5B . When in the recess, the container 10 is lifted off the lower rail 22, allowing the vehicle 32 to move laterally to a different grid location. If a bin 10b that is not located at the top of a stack 12 (the “target bin”) needs to be removed, the bins 10a above (the “non-target bins”) must first be moved to allow access to the target bin 10b. This is accomplished in an operation referred to below as “digging.” Referring to FIG. 3 , during the digging operation, one of the load handling devices 30 sequentially lifts each non-target bin 10a from the stack 12 containing the target bin 10b and places it in an empty position in another stack 12. The target bin 10b can then be accessed by a cargo handling device 30 and moved to a port for onward transportation.

[0051] Each of the provided load handling devices 30 is remotely operable under the control of a central computer. Each individual bin 10 in the system is also tracked so that the appropriate bin 10 can be retrieved, transported, and replaced as needed. For example, the location of each non-target bin is logged so that non-target bin 10a can be tracked during digging operations.

[0052] Wireless communications and networks can be used to provide a communications infrastructure from a central computer, e.g., via one or more base stations, to one or more load handling devices operating on the grid structure. In response to receiving instructions from the central computer, a controller within the load handling device is configured to control various drive mechanisms to control movement of the load handling device. For example, the load handling device may be instructed to retrieve a container from a target storage column at a specific location on the grid structure. This instruction may include various movements in the XY plane of the grid structure 15. As described above, upon reaching the target storage column, the container lifting assembly can be operated to grasp and lift the storage container 10 using the lifting assembly and container gripping assembly 39. Once the container 10 is received within the container receiving space 40 of the load handling device 30, the container 10 is then transported to another location on the grid structure 15, e.g., a “drop-off port.” At the drop-off port, the container 10 is lowered to an appropriate picking station to enable retrieval of any items within the storage container. Movement of the load handling devices 30 on the grid structure 15 may also involve the load handling devices 30 being directed to move to charging stations typically located on the periphery of the grid structure 15 .

[0053] To operate the load handling devices 30 on the grid structure 15, each of the load handling devices 30 includes a motor for driving the wheels 34, 36. The wheels 34, 36 may be driven via one or more belts connected to the wheels or may be individually driven by motors integrated into the wheels. In the case of a single-cell load handling device (where the footprint of the load handling device 30 occupies a single grid cell 17), the motor for driving the wheels may be integrated into the wheel due to the limited space available within the vehicle body. For example, the wheels of a single-cell load handling device are driven by respective hub motors. Each hub motor includes an outer rotor having multiple permanent magnets arranged to rotate around a wheel hub with a coil forming an inner stator.

[0054] 1 to 5 has many advantages and is suitable for a wide range of storage and retrieval operations. In particular, it allows for very dense storage of products and provides a very economical way of storing a large range of different items in bins 10, while still allowing reasonable and economical access to all of the bins 10 when required for picking.

[0055] During storage and retrieval operations, the container lifting assembly uses a lifting assembly (examples of which are shown in FIGS. 4, 5A, 5B, 8, and 9) to raise and / or lower the container gripping assembly in the Z direction. The degree to which the container gripping assembly is raised or lowered varies across the grid storage structure 14. Each stack of containers in the grid storage structure 14 has a current dimension / height in the Z direction defined by the number of containers currently in that stack. The current dimension / height in the Z direction can be determined by tracking, e.g., via a central computer, the containers raised from and / or lowered to each stack of containers. For example, if a stack currently has 10 containers and the containers are of a fixed dimension / height in the Z direction, the current dimension / height of the stack in the Z direction can be determined to be 10 times the fixed dimension / height of the containers in the Z direction. It will be understood that the current dimension / height of the stack in the Z direction can be expressed in absolute terms, for example n metres from the ground, or in relative terms, for example n metres from the bottom of the grid storage structure 14 or n metres from the top of the grid storage structure.

[0056] The current Z-dimensional dimension / height of the stack of containers on which the load handling device is located can be communicated to the load handling device. The lifting assembly of the load handling device can use the current Z-dimensional dimension / height of the stack of containers to control the raising and lowering of the container gripping assembly through operations to retrieve or exchange containers from or into the grid storage structure. To control the raising and / or lowering of the container gripping assembly in this manner, the Z-position (or vertical position, or position perpendicular to the plane in which the container moves across the grid storage structure (i.e., defined by the X and Y directions)) of the container gripping assembly should be known. It will be understood that the Z-position can be an absolute position, for example, n meters from the ground, or a relative position, for example, n meters from the container receiving cavity or recess 40, or n meters from the top of the grid storage structure, or n meters from the top of the top container in the stack of containers on which the load handling device is located. The Z-position allows for determination of how close the container gripping assembly is to the load handling device and / or the top of the top container in the stack of containers. In this way, the container gripping assembly can be appropriately controlled, such as accelerating after being lowered from the load handling device and decelerating as it approaches the top of the top container in the stack of containers. Similarly, the container gripping assembly can be accelerated after being lifted from the top of the top container in the stack of containers and decelerating as it approaches the load handling device.

[0057] During the raising or lowering of a container gripping assembly, the container gripping assembly may become obstructed. For example, the container gripping assembly may encounter a defect in the grid storage structure 14, preventing the container gripping assembly from being raised or lowered smoothly. One such exemplary defect may be a vertical member 16 having a protrusion that contacts the container gripping assembly. Another exemplary defect is when the container lifting assembly does not recognize that it has contacted the top container in a stack and continues to unwind tether. Excess tether may unwind onto an adjacent stack, potentially causing an obstruction within that stack. Yet another defect is when the container gripping assembly is raised and lowered to the point where one side of the container gripping assembly contacts the vertical member 16 to which it then pivots, causing the container gripping assembly to no longer be parallel to the XY plane but potentially become vertical. In either of these cases, the container gripping assembly is thus prevented from operating properly.

[0058] Therefore, it is advantageous to accurately determine the Z position of the container gripping assembly throughout its raising and / or lowering. It is also advantageous to determine whether the container gripping assembly is obstructed during its raising and lowering, and, for example, that the tether 38 is loose. Although Z position and obstructions have been described in the context of a load handling device, it should be understood that it is useful to determine the Z position and obstructions of the gripping assembly in any lifting apparatus, such as a crane (i.e., lifting device) with a motor and tether (i.e., lifting assembly) and a hook (i.e., gripping assembly) that grips, raises, and / or lowers a load.

[0059] FIG. 6 shows a schematic diagram 600 of a load handling device 30 in accordance with the present invention. Dashed lines indicate the load handling device's body 32, which moves on the grid 22 via wheels 34 / 36. A lifting assembly 610 (as shown in FIGS. 4, 5A, 5B, 8, and 9), driven by a motor (not shown), raises and lowers the container gripping assembly 39 by winding and unwinding the tether 38. One or more sensors 640 are configured to detect movement of the container gripping assembly. The load handling device 600 can receive and transmit data from and to each of the lifting assembly 610 and one or more sensors 640 using a processor or controller 650. This data can be stored in a memory device 660. The data in the memory device 660 can be periodically transmitted for further processing via one or more networks, such as a base station.

[0060] FIG. 7 illustrates steps of a method 700 for use with a lifting assembly (such as those used in a load handling device or crane) comprising a gripping assembly configured to grip a load, a lifting assembly configured to raise and lower the gripping assembly, the lifting assembly comprising at least one tether connected to the gripping assembly, and a motor for reeling in and / or unreeling the or each tether to raise and / or lower the gripping assembly. It should be understood that the method of FIG. 7 may be performed using a controller (such as, for example, controller 650 of the load handling device of FIG. 6). In step 710, the motor of the lifting assembly is used to raise and / or lower the gripping assembly, as shown, for example, in FIG. 8 or FIG. 9. In step 720, a sensor is used to detect movement of the gripping assembly. Examples of sensors configured to detect movement of the gripping assembly are described below in connection with FIGS. 9-15. Generally, the sensor comprises an input that is engaged by movement of the gripping assembly. In step 730, a controller is used to determine the vertical position of the gripping assembly using the output of the sensor. It will be appreciated that the detected movement of the gripper assembly can be correlated to a vertical position. For example, if it is detected that one meter of tether (or FFC) has been unwound from the lifting assembly, the vertical position of the gripper assembly has changed by one meter relative to the unwound. If the starting position of the gripper assembly for the one meter unwound is absolutely known (e.g., determined from when the gripper device is fully retracted into the container receiving space 40 of the load handling device 30 located on the grid storage framework 14), the current absolute vertical position of the gripper assembly can be determined. In optional step 740, a controller is used to control / adjust the motion profile of the gripper assembly based on the determined vertical position. Typically, a motor is controlled using the motion profile. In the example of a load handling device, the motor controls the raising and / or lowering of the container gripper assembly according to the motion profile.One such example is a trapezoidal velocity versus time motion profile, which should result in the container gripping assembly being in a particular vertical position at a particular time. Thus, monitoring this vertical position can provide feedback that is used to control / adjust the motion profile.

[0061] An exemplary container lifting assembly (further described in PCT Application No. PCT / EP2022 / 081364 (Ocado)) is shown in FIG. 8 . In FIG. 8 , container lifting assembly 800 has a lifting assembly 802 including four spools 810 for winding and unwinding respective tethers 38. A drive belt 820 is driven by a motor (not shown) to rotate the spools on drive shaft 805 in the opposite direction to drive shaft 806. By rotating drive shafts 805 and 806 in the opposite directions, each tether 38 can be located at or near a corner of the lifting assembly. In particular, as shown in FIG. 8 , the point at which each tether is wound onto or unwound from the spool is at or near a respective corner of the lifting assembly. This allows the tethers to connect to container gripping assemblies 39 at each corner of the container gripping assembly, which increases stability when lifting and lowering the container gripping assembly 39.

[0062] The tether may be a cable, or rope, or tape, or any other form of tether having the necessary physical properties to lift the container. In one implementation, four tethers are used. In one implementation, the tether may comprise steel tape. In one implementation, the tether may be formed of or comprise a polyester material (e.g., a woven polyester material). In particular, the tether may comprise a woven polyester tape or belt, such as a seat belt (i.e., a seat belt may be used as a tether). In another implementation, the tether may comprise a Dyneema RTMThe tether may be made from ultra-high molecular weight polyethylene, UHMVPE or UHMW (also known as high modulus polyethylene, HMPE), such as tape. RTM The tether may comprise a polyester material (e.g., woven polyester) combined with tape. In another implementation, the tether may comprise a cotton material. In another implementation, the tether may comprise a webbing material, such as, for example, webbed polyester, nylon, cotton, or the like. In another implementation, the tether may comprise a conductive material, for example, a woven fabric or woven polyester material with conductive elements or wiring (e.g., copper) woven into the fabric or textile of the tether. In another implementation, the tether may comprise a woven belt (e.g., a seat belt) having conductive elements or wiring woven into the belt. In another implementation, the tether may comprise conductive elements or wiring (e.g., copper) woven into the fabric or textile of the tether to provide power and / or communication (i.e., electrical communication) to the gripping device.

[0063] Also shown is an optional fixed flexible cable (or ribbon cable), FFC, 830, and FFC spool 840 for communicating electrical signals to the gripper assembly 39 to power and control the gripping of the container, as described above with respect to Figure 4. That is, the FFC is used to power and control the pins or clips that engage the bins 10 by a suitable drive mechanism housed within the container gripping assembly 39. One suitable FFC is the Axon'Cable RTM Although an FFC is shown, it will be understood that at least one electrical wire may be used instead for the same purpose, or the conductive element may be integrated with the tether, as described above.

[0064] A system that uses the method of Figure 7 to determine the vertical position of a container gripping assembly is described below. While the lifting assembly shown in Figure 8 (and Figure 9 below) is shown with four spools 810 and respective tethers that raise and lower the container gripping assembly using the configuration shown, it should be understood that the system described below is not limited to the particular number of spools, tethers, and configuration shown for raising and / or lowering the container gripping device.

[0065] 9, 10, 11A, and 11B, a container lifting assembly 900 having sensors capable of determining the vertical position of the container gripping assembly is described. Similar to FIG. 8, the lifting assembly includes four spools 910 for winding and unwinding respective tethers 38. Drive belt 920 is driven by motor 901 (via drive belt 925 and spool 911) to rotate the spools on drive shaft 905 in the opposite direction to drive shaft 906. Drive belt 920 drives pulleys connected to spools 910. By rotating drive shafts 905 and 906 in the opposite directions, each tether 38 can be positioned at or near a corner of the lifting assembly. In particular, as shown in FIG. 9, the point at which each tether is wound onto or unwound from the spool is at or near a respective corner of the lifting assembly. This allows the tethers to connect to the container gripping assembly 39 (not shown) at each corner of the container gripping assembly, thereby improving stability when raising and lowering the container gripping assembly 39. The container lifting assembly also includes an FFC spool 940. An FFC (not shown) is wound on the spool and extends to the container gripping assembly 39 for transmitting electrical signals to the container gripping assembly 39. Thus, the FFC is wound and unwound as the motor rotates the drive shaft 906. A stator 960 is used to send signals to and receive signals from the FFC on the FFC spool 945.

[0066] In one implementation, the FFC spool 940 includes a rotary encoder 950 (i.e., a sensor) for detecting movement of the FFC spool 940. By way of example, the rotary encoder 950 may be held in position between the stator and horizontal bar 925 (although other means of interfacing the rotary encoder 950 with the FFC spool are apparent). The rotary encoder 950 includes a rotating electromechanical device that generates pulses as the FFC spool rotates. For example, pulses are generated for a predetermined amount of angular rotation of the FFC spool. As shown in FIGS. 11A and 11B, the encoder apparatus 1000 includes an encoder disk 945 attached to the FFC spool 840 / 940. The encoder disk 945 includes slots 946 around its periphery. The slots allow transmitter and receiver elements 951 of the encoder 950 to transmit and receive optical signals. Solid space between the slots prevents reception of optical signals. Thus, an optical signal is received and interrupted as the FFC spool rotates, which can be correlated to the angular rotation of the FFC spool 940. While an optical rotary encoder has been described, a mechanical encoder could alternatively be used where the FFC spool 940 directly engages and rotates the input of a mechanical encoder. Alternatively, the motor 920 could have an encoder that could be used to determine the number of rotations of the FFC spool 940. Regardless of the type of rotary encoder implementation, the angular rotation and direction of the FFC spool 940 can be determined as the container gripping assembly 39 is raised or lowered.

[0067] The dimensions of the FFC spool 940 and the FFC can be used to correlate the angular rotation and orientation of the FFC spool 940 to the length of the FFC currently extending from the FFC spool 940. The length of the FFC currently extending from the FFC spool 940 can be correlated to the vertical position of the container gripping assembly, as described above with respect to FIG.

[0068] While the use of a rotational encoder 950 for use with the FFC spool 840 / 940 has been described, it will be understood that the encoder device 1100 depicted in FIGS. 11A and 11B can be used to monitor either of the tether spools 810 / 910. That is, an encoder disk is attached to the tether spool 810 / 910. Thus, the rotation of the tether spool 910 can be monitored instead. Using the dimensions of the tether spool 910 and the tether 38, the angular rotation of the tether spool 910 can be correlated to the length of tether currently extending from the tether spool 910, which can be correlated to the vertical position of the container gripping assembly 39, as described above with respect to FIG. 7. Alternatively, the motor 901 may have a motor encoder that can be used to determine the number of rotations of the tether spool 910. Regardless of the type of rotational encoder implementation, the angular rotation and direction of the tether spool 910 can be determined as the container gripping assembly 39 is raised or lowered.

[0069] It will also be appreciated that, as shown in FIGS. 11A and 11B , an encoder device 1100 can be used to monitor each tether spool 810 / 910 and FFC spool 840 / 940. Using two encoder devices 1100 allows for redundancy in case one of the encoder devices fails. Using two encoder devices 1100 on each tether spool 910 allows for a determination of whether the container gripping assembly 39 is level during a lifting or raising operation. If the two encoder devices 1100 detect the same angular rotation of each tether spool 910, it can be inferred that the container gripping assembly 39 is level. This can occur if one tether spool slips on the shaft on which it rotates. One of the encoder devices 1100 having an output that deviates from the other encoder devices 1100 can indicate that the container gripping assembly 39 is not level. Using four encoder devices 1100 allows the orientation of the container gripping assembly to be detected.

[0070] Using FFC spool 940 to determine the vertical position of the container lifting assembly can be advantageous when the FFC has a relatively higher modulus of elasticity than tether 39, for example, when a polyester woven belt is used for tether 39. A polyester woven belt tends to stretch when unwinding and rewinding in response to the load carried by container gripping assembly 39. Similarly, a polyester woven belt tends to unwind from and rewind onto spool 910 in an unpredictable manner. In comparison, because an FFC has less tendency to stretch and unwinds from and rewinds onto the FFC spool in a predictable manner, detected movement of the FFC spool provides a more accurate determination of the vertical position of container lifting assembly 39.

[0071] Additionally or alternatively, the FFC spool 940 may be rotatably mounted on the shaft 906, for example, via a bearing, such that the FFC spool 940 can rotate independently of or relative to the shaft 906. Thus, the FFC spool 940 unwinds, allowing the FFC cable to extend as the tether unwinds, lowering the container gripping assembly 39. Furthermore, the FFC does not support the load of the container gripping assembly 39. A biasing assembly may be used to ensure that the FFC unwinds onto the FFC spool 940 as the container gripping assembly 39 rises. The biasing assembly opposes the unwinding of the FFC to maintain tension, thereby ensuring a more accurate determination of the vertical position of the container gripping assembly 39. For example, if the FFC extends one meter from the FFC spool 940 and the FFC is determined to be tensioned, it may be determined that the position of the container gripping assembly has changed one meter. As shown in FIG. 10 , the biasing assembly includes a biasing plate 960 and a torsion spring 930 that acts on an FFC spool 940 rotatably mounted on a shaft 906. The biasing plate 960 is fixedly mounted on the shaft 906. The torsion spring 930 is connected to the biasing plate 960 and the FFC spool 945 so as to oppose the unwinding of the FFC spool 945. In other words, the FFC spool 945 is spring-loaded to oppose the application of a rotational force (within the elastic limits of the torsion spring) in the unwinding direction relative to the stationary shaft 925. Thus, the FFC spool unwinds (within the elastic limits of the torsion spring) when this rotational force is removed. In general, any biasing assembly can be used as long as it acts on the rotatably mounted FFC spool 940 to maintain the FFC in tension. For example, a tension spring can be used to connect the biasing plate 960 and the FFC spool 945. Alternatively, the FFC spool 945 may be fixedly attached to the shaft 906 and the biasing device may be located within the container gripping assembly 39. The biasing device in this implementation opposes the winding of the FFC spool 940.This ensures that the FFC remains taut while the container gripping assembly 39 is raised and lowered.

[0072] Referring to FIG. 12 , another sensor 1200 capable of determining the vertical position of a container gripping assembly is illustrated. A spool, which may be any of spools 810 / 910 / 840 / 940, is used to wind and / or unwind the respective tether 38 or FFC 830. A rotary encoder wheel 1210 is biased against the tether 38 or FFC 830 using arm 1220, and the wheel 1210 rotates via pivot 1215. As shown in FIG. 12 , the rotary encoder wheel 1210 rotates as the tether 38 or FFC 830 moves during winding and / or unwinding from the spool 810 / 910 / 840 / 940. That is, the shaft / input of the rotary encoder wheel is rotated by the tether 38 or FFC 830. The rotation of the encoder wheel 1210 can be correlated to the length of the tether 38 or FFC 830 that caused the rotation, which can then be correlated to the vertical position of the container gripping assembly according to the implementations described above. The encoder wheel may be part of an optical or mechanical encoder.

[0073] Referring to FIG. 13 , another sensor 1300 capable of determining the vertical position of a container gripping assembly is described. A spool 1310 can be attached to a shaft 805 / 806 / 905 / 906. Thus, the spool 1310 rotates as the lifting assembly raises and lowers the container gripping assembly. The spool 1310 can be electrically conductive. Additionally or alternatively, the spool 1320 has channels or grooves that allow the conductive wire 1320 to be wound so that wires in adjacent channels / grooves are in physical contact. This means that at a fully wound spool 1310, the conductive wire 1320 is shorted, and a voltage applied between the first end 1310 (connected to the spool) and the second end 1320 (connected to the container gripping assembly) of the conductive wire 1320 returns a given current value. When the spool 1310 is unwound, as shown in FIG. 13 , the length of the conductive wire 1320 is no longer shorted. Thus, a voltage applied between the first and second ends of the conductive wire 1320 returns a decreased current value due to the increased electrical resistance of the conductive wire 1320 configuration. In one implementation, the second end can be connected to an FFC connection on the container gripping assembly 39 to form a closed circuit that allows the current value to be determined. The change in electrical resistance as the conductive wire 1320 is wound and unwound can be correlated to the length of the conductive wire (and thus the tether 38 or FFC 830) that caused the change in electrical resistance, which can then be correlated to the vertical position of the container gripping assembly according to the above implementation. A biasing assembly (such as that described above with respect to the FFC spool) can be used with the spool 1310, provided that the biasing assembly maintains the spool in tension. That is, the biasing assembly opposes the winding or unwinding of the spool 1310, as described above with respect to the FFC spool.

[0074] Referring to FIG. 14, another sensor 1400 capable of determining the vertical position of a container gripping assembly is described. FIG. 14 shows the same configuration as described above with respect to FIG. 8. The description of FIG. 8 applies to that shown in FIG. 8. Additionally, a time-of-flight (ToF) sensor 1410 is attached to the container lifting assembly 39. The ToF sensor 1410 is configured to transmit an optical signal 1420 to a reflective surface (not shown) and receive a reflection 1430 of the transmitted optical signal 1420. The time between transmission and reception of the optical signal (e.g., laser or LED) can be used to calculate the distance between the container lifting assembly 39 and the reflective surface. The reflective surface does not move as the container lifting assembly 39 rises and / or falls. For example, the reflective surface may be positioned on the lifting mechanism 802 or any other suitable part of the load handling device or system. Thus, the distance between the container lifting assembly 39 and the reflective surface can be used to determine the vertical position of the container gripping assembly 39. It should be appreciated that the ToF sensor 1410 may alternatively be located at a fixed location within the lifting mechanism 802 or any other suitable portion of the load handling device or system, and transmit and receive optical signals on a reflective surface of the container lifting assembly 39. Suitable ToF sensors include those available from Texas Instruments RTM This is the OPT3101 ToF-based Long Range Proximity and Distance Sensor AFE Evaluation Module. In general, any laser sensor that measures distance can be used. In principle, any rangefinder type sensor, such as Light Detection and Ranging, LiDAR, or Ultrasonic, could be used to implement the ToF sensor in this implementation.

[0075] 15, another sensor 1500 capable of determining the vertical position of a container gripping assembly is illustrated. A spool, which may be any of spools 810 / 910 / 840 / 940, is used to reel in and / or unreel in the respective tether 38 or FFC 830. A wheel 1510 is biased against spool 810 / 910 / 840 / 940 using arm 1520, and wheel 1510 rotates via pivot 1515. As shown in FIG. 15 , as the spool 810 / 910 / 840 / 940 rotates, the wheel 1510 rotates. The wheel 1510 has a textured outer surface that allows the sensor 1530 to track its movement. One such suitable surface is aluminum or nylon. The sensor 1530 projects an optical signal (such as a laser or LED) onto the textured outer surface of the spool 1510 so that reflected light 1550 can be detected (e.g., via a photodiode) to track the movement of the textured outer surface of the spool 1510. This operation is similar to the operation of an optical computer mouse. The detected movement of the textured outer surface of the spool 1510 can be correlated to the rotation of the spool 810 / 910 / 840 / 940 and therefore the extension of the tether 39 or FFC 820, which can then be correlated to the vertical position of the container gripping assembly, in line with the implementations described above. It will be appreciated that the wheels 1510 may be omitted if the spools 810 / 910 / 840 / 940 instead have a surface that allows the sensors 1530 to track their movement.

[0076] Referring to FIG. 16 , a system using the sensors described above to determine a fault in the container gripping assembly 39 is described. The motor 901 reels in and unreels the tether 38 / 830. Therefore, any of the sensors described above that directly monitor the motor actually detect whether the motor is currently operating and, therefore, whether the tether is being reeled in or unreeled. In other words, if the motor is activated, any of the sensors described above that directly monitor the motor detects the motor's operation. If the container gripping assembly 39 is obstructed, the motor will continue to reel in and / or unreel the tether, while the tether 38 / 830 and / or FFC 830 will experience a change in configuration. For example, if the container gripping assembly 39 encounters an obstacle during descent, the tether 38 / 830 and / or FFC 830 will slacken. Therefore, the sensors described above that can detect changes in the state of the tether 38 / 830 and / or FFC 830, in conjunction with the sensor that detects the state of the motor 901, can be used to determine a fault in the container gripping assembly 39. In particular, if the motor is running as detected by a particular sensor and the tether 38 / 830 and / or FFC 830 is loose as detected by a particular sensor, it can be assumed that a fault has occurred in the gripper assembly 39. That is, if there is a fault when lowering the container gripper assembly, the motor will no longer cause the container gripper assembly 39 to lower.

[0077] Processor / controller 1610 (which may be the same as processor / controller 650) can receive input from motor actuation sensors 1620. Sensors 1620 include sensors such as those described above: Motor encoder for motor 910 FFC or tether spool 810 / 910 / 840 / 940 monitored using encoder device 1100 as shown in FIGS. 11A and 11B As shown in Figure 15

[0078] All of the sensors 1620 detect motor actuation either directly or through the movement of a spool (either an FFC or tether spool 810 / 910 / 840 / 940) fixed to the shaft rotated by the motor. Generally, the motor actuation sensor 1620 indicates whether the motor is actuated to reel in and / or unreel in the tether 38 / 830. If the motor is rotating the shaft onto which the tether / FFC is reeling in and / or unreeling, it is assumed that the container lifting assembly 39 is being raised and / or lowered.

[0079] The processor / controller 1610 can receive different inputs to verify that the container lifting assembly 39 is actually raising and / or lowering. One input that can be used for this purpose is that provided by a sensor 1630 that detects movement of the gripper assembly. The sensor 1630 can include sensors such as those described above: FFC spool 940, encoder 950, and biasing device shown in FIG. As shown in Figure 12 13 and the biasing device As shown in Figure 14 As shown in Figure 15 when used with FFC spool 940 / 940 and biasing device

[0080] The output of sensor 1630 depends on the movement of the container gripping assembly 39. That is, sensor 1630 can indicate, to the extent possible, the extent to which the container gripping assembly 39 is being raised and / or lowered. Thus, processor / controller 1610 can determine whether operation of the motor (indicated via sensor 1620) actually results in the raising and / or lowering of the container lifting assembly 39 (indicated via sensor 1630).

[0081] Alternatively, a given sensor 1630 may indicate, to the extent possible, the degree to which the container gripping assembly 39 is being raised and / or lowered, and the processor / controller 1610 may correlate the output of the sensor 1630 to a motor motion profile used to control the raising and / or lowering of the container gripping assembly 39. That is, the processor / controller 1610 may determine whether the current raising and / or lowering of the container gripping assembly 39 (as indicated via the sensor 1630) correlates with that controlled by the motor. For example, a trapezoidal motion profile of the motor, which maps time to the speed of the container gripping assembly 39, may be converted by the controller into a corresponding time versus distance profile. From the converted time versus distance profile, deviations of the container gripping assembly 39 from a determined vertical position may be detected.

[0082] In general, the system of Figure 16 can be used to determine mismatches between the actuation of a motor and the resulting raising and / or lowering of a container gripping assembly. The presence of such mismatches can be detected using the method of Figure 17.

[0083] 17 illustrates steps of a method 1700 for use in a lifting assembly (such as those used in a load handling device or crane) comprising a gripping assembly configured to grip a load, a lifting assembly configured to raise and lower the gripping assembly, the lifting assembly comprising at least one tether connected to the gripping assembly, and a motor for reeling and / or unreeling the or each tether around at least one shaft to raise and / or lower the gripping assembly. It should be understood that the method of FIG. 17 may be performed using a controller (e.g., controller 650 of the load handling device of FIG. 6). In step 1710, a motor (e.g., motor 901) rotates at least one shaft (e.g., 805, 906, 906) to reel and / or unreel the or each tether (e.g., tether 38) to raise and / or lower the gripping assembly (e.g., container gripping assembly 39). In step 1720, a sensor (such as sensor 1630) is used to detect movement of the gripper assembly. Examples of sensors 1630 configured to detect movement of the gripper assembly are described above in connection with FIGS. 9-15. In step 1730, a controller is used to determine a fault in the gripper assembly if the current output of the sensor does not correlate with the winding and / or unwinding of the or each tether around the or each shaft to raise and / or lower the gripper assembly. That is, the controller determines a discrepancy between the drive of the motor and the resulting raising and / or lowering of the gripper assembly. An example of how step 1730 may be implemented using sensors 1620 and / or inputs 1640 is provided below.

[0084] In optional step 1740, the controller is used to stop the motor upon determining a gripper assembly failure, meaning that the tether is not further wound and / or unwound, thus avoiding damage to the gripping device (such as the container gripping assembly 39), and / or the lifting device (such as the container lifting assembly 39), and / or the surrounding environment (such as the grid storage structure 14).

[0085] In one implementation of the method of FIG. 17, the sensor 1620 is a motor encoder of a motor (such as motor 901), and the controller is configured to determine a fault in the gripping assembly if the current output of the sensor does not correlate with the current output of the motor encoder. By way of example only, both the motor encoder and the sensor 1630 may be configured to generate a corresponding output for each increment of at least one shaft rotation. Thus, a deviation in the outputs between the motor encoder (i.e., sensor 1620) and the sensor 1630 may be used to indicate that the shaft rotation is no longer resulting in the lifting assembly being raised and / or lowered. The controller may be configured to determine a grid assembly fault when the current output of the sensor 1630 does not correlate with the current output of the motor encoder by a threshold value. The threshold value may, of course, be set to allow for a small deviation before a fault is determined. For example, the threshold value may require that two subsequent outputs differ.

[0086] Another implementation of the method of FIG. 17 uses a tether spool (e.g., spool 810 / 910) for the or each tether onto which the or each tether is wound and / or unwound. The or each tether spool is fixedly attached to a shaft that is rotated by a motor. Sensor 1620 is a tether rotation encoder for the or each tether spool. The or each tether rotation encoder is configured to engage with the or each spool to detect the degree to which the or each spool has rotated as the or each respective tether is wound and / or unwound. Any of the rotation encoders described above, such as those shown in FIGS. 11A and 11B, can be used as the tether rotation encoder. The controller is configured to determine a fault in the gripper assembly if the current output of the sensor does not correlate with the current output of the or each tether rotation encoder. By way of example only, both the tether rotation encoder and sensor 1630 can be configured to generate a corresponding output for each increment of rotation of at least one shaft. Thus, a deviation in the output between the or each tether rotation encoder (i.e., sensor 1620) and sensor 1630 can be used to indicate that shaft rotation is no longer resulting in raising and / or lowering of the lifting assembly. The controller may be configured to determine a gripper assembly fault if the current output of sensor 1630 does not correlate with the current output of the tether rotation encoder by a threshold value. The threshold value can, of course, be set to allow for a small deviation before a fault is determined. For example, the threshold value may require that two subsequent outputs be different.

[0087] Another implementation of the method of FIG. 17 uses an electric cable spool (such as FFC spool 840 / 940) from which an electric cable (such as FFC 830) is unwound and wound. The electric cable spool is fixedly attached to a shaft that is rotated by a motor. The electric cable spool is connected to and in electrical communication with the gripper assembly. Sensor 1620 is an electric cable rotation encoder for the electric cable spool. The electric cable rotation encoder is configured to engage with the or each respective spool to detect the degree to which the or each spool has rotated as the or each respective tether is wound and / or unwound. Any of the rotation encoders described above, such as those shown in FIGS. 11A and 11B, can be used as the electric cable rotation encoder. The controller is configured to determine a fault in the gripper assembly if the current output of the sensor does not correlate with the current output of the tether rotation encoder. By way of example only, both the electric cable rotation encoder and sensor 1630 can be configured to generate a corresponding output for each increment of rotation of at least one shaft. Thus, a deviation in the outputs between the electric cable rotation encoder (i.e., sensor 1620) and sensor 1630 can be used to indicate that shaft rotation is no longer resulting in raising and / or lowering of the lifting assembly. The controller may be configured to determine a grid assembly fault if the current output of sensor 1630 does not correlate with the current output of the electric cable rotation encoder by a threshold value. The threshold value can, of course, be set to allow for a small deviation before a fault is determined. For example, the threshold value may require that two subsequent outputs be different.

[0088] In another implementation of the method of FIG. 17 , a tether spool (e.g., spool 810 / 910) for the or each tether is used onto which the or each tether is wound and / or unwound. The or each tether spool is fixedly attached to a shaft rotated by a motor. Sensor 1620 comprises a tether spool sensor, as described above and shown in FIG. 15 , comprising a light source and a light detector. As described above, the light source is configured to transmit a light signal onto a surface that moves as the gripper assembly is raised and / or lowered. The light detector is configured to detect reflection of the light signal from the surface to detect movement of the surface. The lifting assembly comprises a wheel that contacts the tether spool onto which the or each respective tether is wound and / or unwound, wherein the wheel comprises the surface, or alternatively, the or each electrical cable spool comprises the surface. The controller is configured to determine a fault in the gripper assembly if the current output of the sensor does not correlate with the current output of the tether spool sensor. By way of example only, both the tether spool sensor and sensor 1630 can be configured to generate a corresponding output for each increment of at least one shaft rotation. Thus, a deviation in the output between the or each tether spool sensor (i.e., sensor 1620) and sensor 1630 can be used to indicate that shaft rotation is no longer resulting in the lifting assembly being raised and / or lowered. The controller may be configured to determine a gripper assembly fault if the current output of sensor 1630 does not correlate with the current output of the tether spool sensor by a threshold value. The threshold value can, of course, be set to allow for a small deviation before a fault is determined. For example, the threshold value may require that two subsequent outputs be different.

[0089] Another implementation of the method of FIG. 17 uses an electric cable spool (such as FFC spool 840 / 940) from which an electric cable (such as FFC 830) is unwound and reeled. The electric cable spool is fixedly mounted on a shaft that is rotated by a motor. The electric cable spool is connected to and in electrical communication with the gripper assembly. Sensor 1620 comprises an electric cable spool sensor, as described above and shown in FIG. 15, comprising a light source and a light detector. As described above, the light source is configured to transmit an optical signal onto a surface that moves as the gripper assembly is raised and / or lowered. The light detector is configured to detect reflection of the optical signal from the surface to detect movement of the surface. The lifting assembly comprises a wheel that contacts the electric cable spool from which the electric cable spool is wound and / or unwound, wherein the wheel comprises the surface, or alternatively, the electric cable spool comprises the surface. The controller is configured to determine a gripping assembly fault if the sensor's current output does not correlate with the current output of the electric cable spool sensor. By way of example only, both the electric cable spool sensor and sensor 1630 can be configured to generate a corresponding output for each increment of at least one shaft rotation. Thus, a deviation in the output between the electric cable spool sensor (i.e., sensor 1620) and sensor 1630 can be used to indicate that shaft rotation is no longer resulting in the lifting assembly being raised and / or lowered. The controller may be configured to determine a gripping assembly fault if the sensor's 1630 current output does not correlate with the electric cable spool sensor current output by a threshold value. The threshold value can, of course, be set to allow for a small deviation before a fault is determined. For example, the threshold value may require that two subsequent outputs differ.

[0090] The above five implementations use a sensor 1620 that indicates the motor's actuation directly to a processor controller that implements the method of FIG.

[0091] Additionally or alternatively, the controller can receive a motion profile so that it can derive an expected state of the gripper assembly. That is, the controller is instructed on how the gripper assembly should move. As described above, a motor motion profile can be provided to the controller, which maps time to the velocity of the container gripper assembly 39. A corresponding time-vs.-distance profile can instead be provided or derived from the motion profile by a processor. Thus, as soon as the controller detects movement of the gripper assembly via sensor 1630, the controller can compare the movement of the gripper assembly to the expected movement according to that derived from the motion profile. This can be used to further verify that a fault has occurred if input 1640 is used in addition to input 1620.

[0092] The method of FIG. 17 also uses a sensor 1630, examples of which are described below.

[0093] One implementation of the method of FIG. 17 uses an electrical cable spool (such as FFC spool 840 / 940) from which an electrical cable (such as FFC 830) is unwound and reeled. The electrical cable spool is rotatably mounted on a shaft that is rotated by a motor, such as FFC spool 940 and biasing device described above and shown in FIG. 9 . The electrical cable spool is connected to and in electrical communication with the gripper assembly. Sensor 1630 includes a rotary encoder, such as encoder 950. When the gripper assembly is disturbed, FFC spool 940 of FIG. 9 returns to its biased state. That is, the FFC spool and FFC are no longer under tension from the movement of the container lifting assembly and snap back to their biased state. The return to the biased state means that the rotary encoder output of sensor 1630 in this implementation no longer correlates with the output provided by sensor 1620, and a fault is detected as described above. Additionally or alternatively, the vertical position of the gripper assembly may be derived from sensor 1630 in this implementation and compared to the input provided by 1640 to determine a fault.

[0094] In another implementation of the method of Figure 17, sensor 1630 comprises a rotary encoder, such as encoder 1210 described above and shown in Figure 12. When the gripper assembly is obstructed, rotary encoder 1210 of Figure 12 no longer rotates due to reduced traction with either tether 38 or FFC 830. The loss of traction means that the rotary encoder output of sensor 1630 in this embodiment no longer correlates with the output provided by sensor 1620, and a fault is detected as described above.

[0095] Another implementation of the method of FIG. 17 uses a wire spool (such as wire spool 1310) from which wire (such as wire 1320) is unwound and wound. The wire spool is rotatably mounted on a shaft that is rotated by a motor, such as the wire spool 1310 and biasing device described above and shown in FIG. 13. The wire spool is connected to a gripper assembly. Sensor 1630 comprises sensor 1300. When the gripper assembly is obstructed, wire spool 1310 of FIG. 13 returns to its biased state. That is, wire spool 1310 is no longer under tension from the movement of the container lifting assembly and snaps back to its biased state. The return to the biased state means that the output of sensor 1300 in this implementation no longer correlates with the output provided by sensor 1620, and a fault is detected as described above. Additionally or alternatively, the vertical position of the gripper assembly may be derived from sensor 1630 in this implementation and compared to the input provided by 1640 to determine a fault.

[0096] In another implementation of the method of FIG. 17 , sensor 1630 comprises a ToF sensor as described above and shown in FIG. 14 (ToF sensor 1410, or generally any laser sensor that measures distance, can be used). When the gripper assembly is obstructed, the ToF sensor no longer detects a change in distance. Alternatively, the gripper assembly can be tilted to such an extent that the ToF sensor no longer detects a returning optical signal due to loss of alignment with the reflective surface. The lack of a change in distance measurement, or the absence of a returning optical signal, means that the output of sensor 1630 in this implementation no longer correlates with the output provided by sensor 1620, and a fault is detected as described above. Additionally or alternatively, the vertical position of the gripper assembly can be derived from sensor 1630 in this implementation and compared to the input provided by 1640 to determine a fault.

[0097] One implementation of the method of FIG. 17 uses an electrical cable spool (such as FFC spool 840 / 940) from which an electrical cable (such as FFC 830) is unwound and reeled. The electrical cable spool is rotatably mounted on a shaft rotated by a motor, such as FFC spool 940 and biasing device described above and shown in FIG. 9. The electrical cable spool is connected to and in electrical communication with the gripper assembly. Sensor 1630 comprises an electrical cable spool sensor, as described above and shown in FIG. 15, comprising a light source and a light detector. As described above, the light source is configured to transmit an optical signal onto a surface that moves as the gripper assembly is raised and / or lowered. The light detector is configured to detect reflection of the optical signal from the surface to detect movement of the surface. The lifting assembly comprises a wheel that contacts the electrical cable spool from which the electrical cable is unwound and / or reeled, where the wheel comprises the surface, or alternatively, where the electrical cable spool comprises the surface. When the gripper assembly is obstructed, FFC spool 940 in FIG. 9 returns to its biased state. That is, the FFC spool and FFCs are no longer under tension from the movement of the container-lifting assembly and snap back to their biased state. The return to the biased state means that the rotary encoder output of sensor 1630 in this implementation no longer correlates with the output provided by sensor 1620, and a fault is detected as described above. Additionally or alternatively, the vertical position of the gripper assembly can be derived from sensor 1630 in this implementation and compared to the input provided by 1640 to determine a fault.

[0098] In this document, the phrase "movement in the n-direction," where n is one of x, y, and z (and related phrases) is intended to mean movement substantially along or parallel to the n-axis in either direction (i.e., toward the positive end of the n-axis or toward the negative end of the n-axis).

[0099] In this document, the term "connect" and its derivatives are intended to encompass the possibilities of direct and indirect connections. For example, "x is connected to y" is intended to encompass the possibilities of x being directly connected to y with no intervening components, and the possibilities of x being indirectly connected to y with one or more intervening components. When a direct connection is intended, "directly connected," "directly connected," or similar terms are used. Similarly, the term "support" and its derivatives are intended to encompass the possibilities of direct and indirect contact. For example, "x supports y" is intended to encompass the possibilities of x directly supporting and directly contacting y with no intervening components, and the possibilities of x indirectly supporting y with one or more intervening components that contact x and / or y. The term "mount" and its derivatives are intended to encompass the possibilities of direct and indirect attachment. For example, "x is attached to y" is intended to include the possibility that x is directly attached to y with no intervening components, and the possibility that x is indirectly attached to y with one or more intervening components.

[0100] As used herein, the term "comprises" and its derivatives are intended to have an inclusive, rather than exclusive, meaning. For example, "x comprises y" is intended to include the possibility that x includes one and only one y, multiple ys, or one or more ys and one or more other elements. When an exclusive meaning is intended, the phrase "x is composed of y" is used to mean that x includes only y and nothing else.

[0101] As used herein, a "controller" is intended to include any hardware suitable for controlling (e.g., providing instructions to) one or more other components. For example, a processor with one or more memories and appropriate software may process data for one or more components and send appropriate instructions to the components to enable them to perform their / their intended function.

[0102] As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless clearly indicated otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used herein, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0103] The invention can take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment containing both hardware and software elements, hi a preferred embodiment, the invention is implemented in software.

[0104] Furthermore, the present invention may take the form of a computer program product embodied as a computer-readable medium having computer-executable code thereon for use by or in connection with a computer. For purposes of this description, a computer-readable medium may be any tangible apparatus that can contain, store, communicate, propagate, or transfer a program for use by or in connection with a computer. Furthermore, a computer-readable medium may be an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system (or apparatus or device) or propagation medium. Examples of computer-readable media include semiconductor or solid-state memory, magnetic tape, removable computer diskettes, random access memory (RAM), read-only memory (ROM), rigid magnetic disks, and optical disks. Current examples of optical disks include compact disk-read-only memory (CD-ROM), compact disk-read / write (CD-R / W), and DVD.

[0105] The flowcharts in the figures illustrate the architecture, functionality, and operation of possible implementations of methods according to various embodiments of the present invention. In this regard, each block of the flowchart may represent a module, segment, or portion of code, comprising one or more executable instructions for implementing the specified logical function(s). It should also be noted that in some alternative implementations, the functions shown in the blocks may occur out of the order shown in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may be executed in the reverse order, depending on the functionality involved. It should also be noted that each block of the flowchart, and combinations of blocks in the flowchart, may be implemented by a dedicated hardware-based system that performs the specified functions or operations, or a combination of dedicated hardware and computer instructions.

[0106] It will be understood that the above description is given by way of example only, and that various modifications may be made by those skilled in the art. Although various embodiments have been described above with a certain degree of particularity, or with reference to one or more individual embodiments, those skilled in the art could make numerous changes to the disclosed embodiments without departing from the scope of the invention.

Claims

1. 1. A lifting assembly for raising and / or lowering a container from and / or to a stack of containers in a grid storage structure, said lifting assembly comprising: a gripping assembly configured to grip a load; and a lifting assembly configured to lift and lower the gripping assembly, the lifting assembly comprising: at least one tether connected to the gripping assembly; a motor for winding and / or unwinding the or each tether to raise and / or lower the gripping assembly, wherein the lifting assembly further comprises: a sensor configured to detect movement of the gripper assembly, wherein the sensor has an input that varies with movement of the gripper assembly; a controller configured to use the output of the sensor to determine a vertical position of the gripper assembly.

2. the lifting assembly includes an electrical cable connected to the gripping assembly, wherein the electrical cable is configured to be wound and / or unwound as the gripping assembly is raised and / or lowered; 2. The lifting assembly of claim 1, wherein the sensor is configured to detect the extent to which the electrical cable is wound and / or unwound.

3. 3. The lifting assembly of claim 2, further comprising an electric cable spool about which the electric cable is wound and / or unwound, and wherein the sensor comprises a rotational encoder configured to engage the electric cable spool to detect the extent to which the electric cable spool is rotated as the electric cable is wound and / or unwound.

4. A lifting assembly according to claim 2 or 3, wherein the electrical cable has a higher modulus of elasticity than the or each tether.

5. 5. A lifting assembly according to any one of claims 2 to 4, further comprising a tether spool for the or each tether onto which the or each tether is wound and / or unwound, wherein the electrical cable spool and the or each tether spool are mounted on a shaft such that the electrical cable spool can rotate relative to the or each tether spool.

6. 6. The lifting assembly of claim 2, further comprising a biasing assembly configured to oppose unwinding or rewinding of an electric cable spool such that the electric cable is tensioned between the lifting assembly and the gripping assembly.

7. A lifting assembly according to any one of claims 2 to 6, wherein the electrical cable transmits electrical signals to the gripping assembly.

8. The lifting assembly of claim 2 , wherein the electrical cable comprises a fixed flexible cable, FFC, or ribbon cable.

9. 2. A lifting assembly according to claim 1, wherein the sensor comprises a motor encoder of the motor, the motor encoder configured to detect the extent to which the or each tether has been reeled in and / or unreeled.

10. 10. A lifting assembly as described in claim 9, further comprising a tether spool for the or each tether onto which the or each tether is wound and / or unwound, and wherein the motor encoder detects the extent to which the or each tether spool is rotated as the or each tether is wound and / or unwound.

11. 2. A lifting assembly according to claim 1, wherein the sensor comprises a rotary encoder configured to detect the extent to which the or each tether has been wound and / or unwound.

12. 12. A lifting assembly as described in claim 11, further comprising a tether spool for the or each tether onto which the or each tether is wound and / or unwound, and wherein the sensor comprises a rotary encoder for the or each tether spool, and wherein the or each rotary encoder is configured to engage the or each spool to detect the extent to which the or each spool has rotated as the or each respective tether is wound and / or unwound.

13. 2. A lifting assembly as described in claim 1, wherein the sensor comprises a rotary encoder for the or each tether, wherein the rotary encoder is configured to contact the respective tether such that winding and / or unwinding of the or each respective tether rotates an input of the rotary encoder.

14. the lifting assembly includes an electrical cable connected to the gripping assembly, wherein the electrical cable is configured to be wound and / or unwound as the gripping assembly is raised and / or lowered; 2. A lifting assembly as described in claim 1, wherein the sensor comprises a rotary encoder configured to engage the electrical cable such that winding and / or unwinding of the or each tether rotates a shaft of the rotary encoder.

15. 15. A lifting assembly according to claim 13 or 14, further comprising a biasing assembly configured to bias the or each rotary encoder into contact with the or each respective tether or electrical cable.

16. the lifting assembly includes an electrical wire connected to a gripping device, wherein the electrical wire is configured to be wound on and / or unwound when the gripping assembly is raised and / or lowered; an electric wire spool onto which the electric wire is wound and / or unwound, wherein the electric wire is wound onto the electric wire spool so that the electric wire on the electric wire spool is short-circuited; 2. The lifting assembly of claim 1, wherein the sensor is configured to measure the electrical resistance of the wire as the wire is wound and / or unwound.

17. 17. The lifting assembly of claim 16, further comprising a biasing assembly configured to oppose unwinding or winding of a spool of electrical wire such that electrical wire is tensioned between the lifting assembly and the gripping assembly.

18. The lifting assembly of claim 1 , wherein the sensor comprises a time-of-flight, ToF, sensor.

19. The sensor comprises a light source and a light detector, wherein: the light source is configured to transmit a light signal onto a moving surface as the gripping assembly is raised and / or lowered; The lifting assembly of claim 1 , wherein the optical detector is configured to detect reflection of the optical signal from a surface to detect movement of the surface.

20. 20. The lifting assembly of claim 19, wherein the lifting assembly comprises an electrical cable connected to the gripping assembly, wherein the electrical cable is configured to be wound and / or unwound as the gripping assembly is raised and / or lowered.

21. 21. A lifting assembly as claimed in claim 19 or 20, wherein the lifting assembly comprises a wheel in contact with a tether spool on which the or each respective tether is wound and / or unwound, or an electric cable spool on which an electric cable is wound and / or unwound, and wherein the wheel comprises the surface.

22. 21. A lifting assembly according to claim 19 or 20, wherein the or each tether spool or electrical cable spool is provided with said surface.

23. 23. A lifting assembly according to any one of claims 1 to 22, wherein the controller is configured to use the determined vertical position to control / regulate the raising and / or lowering of the gripping assembly.

24. 24. A lifting assembly according to any one of claims 1 to 23, wherein the number of tethers is four, and optionally wherein the tethers comprise steel tape or woven polyester tape.

25. 1. A load handling device for lifting and moving storage containers stacked in a grid framework structure, comprising: a first set of parallel rails or tracks and a second set of parallel rails or tracks extending substantially perpendicular to the first set of rails or tracks in a substantially horizontal plane to form a grid pattern comprising a plurality of grid spaces, wherein the grid is supported by a set of uprights to form a plurality of vertical storage locations beneath the grid such that containers are stacked between and guided by the uprights vertically through the plurality of grid spaces; a body or skeleton attached to a first set of wheels arranged to engage the first set of parallel tracks and a second set of wheels arranged to engage the second set of parallel tracks; 25. A cargo handling device comprising: a container lifting assembly comprising the lifting assembly of any one of claims 1 to 24, wherein the gripping assembly comprises a container gripping assembly configured to grip a container.

26. 26. A method for determining the vertical position of the gripper assembly of the lifting assembly according to any one of claims 1 to 25, said method comprising: using the motor to raise and / or lower the gripper assembly; using the controller to determine a vertical position of the gripper assembly using an output of the sensor.

27. 27. A computer program comprising instructions which, when executed by a computer, cause the computer to carry out the method of claim 26.

28. 1. A lifting assembly for raising and / or lowering a container from and / or to a stack of containers in a grid storage structure, said lifting assembly comprising: a gripping assembly configured to grip a load; and a lifting assembly configured to lift and lower the gripping assembly, the lifting assembly comprising: at least one tether connected to the gripping assembly; a motor configured to wind and / or unwind the or each tether around at least one shaft to raise and / or lower the gripping assembly, wherein the lifting assembly further comprises: a sensor configured to detect movement of the gripper assembly; a controller configured to determine a fault in the gripper assembly if the current output of the sensor does not correlate with winding and / or unwinding of the or each tether around the or each shaft to raise and / or lower the gripper assembly.

29. 30. A lifting assembly as described in claim 28, further comprising a second sensor, wherein said second sensor directly detects rotation of said at least one shaft.

30. The second sensor comprises a motor encoder of the motor, and wherein the controller:

30. A lifting assembly according to claim 29, configured to determine the fault of the gripper assembly if the current output of the sensor does not correlate with the current output of the motor encoder.

31. 31. A lifting assembly as claimed in claim 30, wherein the controller is configured to determine the fault in a grid assembly when the current output of the sensor does not correlate with the current output of the motor encoder by a threshold value.

32. further comprising a tether spool for the or each tether onto which the or each tether is wound and / or unwound; wherein the second sensor comprises a tether rotation encoder for the or each tether spool, wherein the or each tether rotation encoder is configured to engage the or each spool to detect the extent to which the or each spool has rotated as the or each respective tether is wound and / or unwound; wherein the controller:

30. A lifting assembly according to claim 29, configured to determine the fault of the gripper assembly if the current output of the sensor does not correlate with the current output of the or each tether rotation encoder.

33. 33. A lifting assembly as claimed in claim 32, wherein the controller is configured to determine the fault of the gripper assembly when the current output of the sensor does not correlate with the current output of the tether rotation encoder by a threshold value.

34. the lifting assembly includes an electrical cable connected to the gripping assembly, wherein the electrical cable is configured to be wound and / or unwound as the gripping assembly is raised and / or lowered; an electric cable spool on which the electric cable is wound and / or unwound, wherein the second sensor comprises an electric cable rotation encoder for the electric cable spool, wherein the or each electric cable rotation encoder is configured to engage the electric cable spool to detect the extent to which the electric cable spool has rotated as the electric cable is wound and / or unwound; wherein the controller:

30. A lifting assembly according to claim 29, configured to determine the fault of the gripper assembly if the current output of the sensor does not correlate with the current output of the electrical cable rotary encoder.

35. further comprising a tether spool for the or each tether onto which the or each tether is wound and / or unwound; wherein the second sensor comprises a tether spool sensor having a light source; a photodetector, wherein: the light source is configured to transmit a light signal onto a surface that moves as the gripping assembly is raised and / or lowered; the optical detector is configured to detect reflection of the optical signal from the surface to detect movement of the surface; wherein the controller:

30. A lifting assembly as claimed in claim 29, configured to determine the fault in the gripper assembly if the current output of the sensor does not correlate with the current output of the tether spool sensor.

36. the lifting assembly comprises a wheel in contact with a tether spool onto which the or each respective tether is wound and / or unwound, wherein the wheel comprises the surface; or 36. A lifting assembly as claimed in claim 35, wherein the or each tether spool comprises said surface.

37. the lifting assembly includes an electrical cable connected to the gripping assembly, wherein the electrical cable is configured to be wound and / or unwound as the gripping assembly is raised and / or lowered; an electric cable spool onto which the electric cable is wound and / or unwound, wherein: the second sensor comprises an electrical cable spool sensor including a light source and a photodetector, wherein the light source is configured to transmit a light signal onto a surface that moves as the gripping assembly is raised and / or lowered; the optical detector is configured to detect reflection of the optical signal from the surface to detect movement of the surface; wherein the controller:

30. A lifting assembly as claimed in claim 29, configured to determine the fault of the gripper assembly if the current output of the sensor does not correlate with the current output of the electrical cable spool sensor.

38. the lifting assembly includes a wheel that contacts an electric cable spool on which the electric cable is wound and / or unwound; wherein the wheel comprises a surface or 38. A lifting assembly as described in claim 37, wherein said electrical cable spool comprises said surface.

39. The sensor comprises an input engaged by movement of the gripper assembly, wherein the controller: receiving a motion profile that controls the raising and / or lowering of the gripper assembly; determining a vertical position of the gripper assembly using the output of the sensor; configured to determine the fault of the gripping assembly if the vertical position of the gripping assembly at a current time does not correlate by a threshold to a corresponding vertical position derived from a motion profile.

39. A lifting assembly according to any one of claims 28 to 38.

40. the lifting assembly includes an electrical cable connected to the gripping assembly, wherein the electrical cable is configured to be wound and / or unwound as the gripping assembly is raised and / or lowered; wherein the sensor is configured to detect an extent to which the electrical cable is wound and / or unwound; 40. A lifting assembly according to any one of claims 28 to 39, comprising a biasing assembly configured to oppose unwinding or rewinding of an electric cable spool such that the electric cable is tensioned between the lifting assembly and the gripping assembly.

41. 41. A lifting assembly as described in claim 40, further comprising an electric cable spool onto which the electric cable is wound and / or unwound, and wherein the sensor comprises a rotational encoder configured to engage the electric cable spool to detect the extent to which the electric cable spool has rotated as the electric cable is wound and / or unwound, and wherein the electric cable spool is configured to rotate relative to the or each shaft.

42. 42. A lifting assembly according to claim 40 or 41, wherein the electrical cable has a higher modulus of elasticity than the or each tether.

43. 43. A lifting assembly according to any one of claims 40 to 42, wherein the electrical cable carries electrical signals to the gripping assembly.

44. 44. A lifting assembly according to any one of claims 39 to 43, wherein the electrical cable comprises a flat flexible cable, FFC, or ribbon cable.

45. 40. A lifting assembly according to any one of claims 28 to 39, wherein the sensor comprises a rotary encoder for the or each tether, the rotary encoder configured to contact the respective tether such that winding and / or unwinding of the or each respective tether rotates an input of the rotary encoder.

46. the lifting assembly comprises an electrical cable connected to the gripping assembly, wherein the electrical cable is configured to be wound and / or unwound as the gripping assembly is raised and / or lowered, wherein the electrical cable optionally comprises a flat flexible cable, FFC, or ribbon cable; 40. A lifting assembly as described in any one of claims 28 to 39, wherein the sensor comprises a rotary encoder configured to engage the electrical cable such that winding and / or unwinding of the or each tether rotates a shaft of the rotary encoder.

47. 47. A lifting assembly according to claim 45 or 46, further comprising a biasing assembly configured to bias the or each rotary encoder into contact with the or each respective tether or electrical cable.

48. The lifting assembly includes: the lifting assembly includes an electrical cable connected to the gripping assembly, wherein the electrical cable is configured to be wound and / or unwound as the gripping assembly is raised and / or lowered; an electric cable spool onto which the electric cable is wound and / or unwound, wherein the electric cable spool is configured to rotate relative to the or each shaft; a biasing assembly configured to oppose unwinding or winding of the electric cable spool so that the electric cable is tensioned between the lifting assembly and the gripping assembly; wherein the sensor comprises an electrical cable spool sensor comprising a light source and a photodetector; wherein the light source is configured to transmit a light signal onto a moving surface as the gripping assembly is raised and / or lowered; the optical detector is configured to detect reflection of the optical signal from the surface to detect movement of the surface; 40. A lifting assembly according to any one of claims 28 to 39, wherein the lifting assembly optionally comprises wheels in contact with the electrical cable spool around which the or each respective tether is wound and / or unwound, and wherein the wheels comprise the surface, or optionally wherein the electrical cable spool comprises the surface.

49. the lifting assembly includes an electrical wire connected to a gripping device, wherein the electrical wire is configured to be wound on and / or unwound when the gripping assembly is raised and / or lowered; an electric wire spool onto which the electric wire is wound and / or unwound, wherein the electric wire is wound onto the electric wire spool such that the electric wire on the electric wire spool is short-circuited, and wherein the electric wire spool is configured to rotate relative to the or each shaft; a biasing assembly configured to oppose unwinding or winding of the wire spool so that the wire is tensioned between the lifting assembly and the gripping assembly; 40. A lifting assembly according to any one of claims 28 to 39, wherein the sensor is configured to measure the electrical resistance of the wire as the wire is wound and / or unwound.

50. 50. A lifting assembly according to any one of claims 28 to 49, wherein the sensor comprises a time-of-flight, ToF, sensor.

51. 51. A lifting assembly according to any one of claims 28 to 50, wherein the controller is configured to stop the motor upon determining a fault in the gripper assembly.

52. 52. A lifting assembly according to any one of claims 28 to 51, wherein the number of said tethers is four, and optionally wherein said tethers comprise steel tape or woven polyester tape.

53. 1. A load handling device for lifting and moving storage containers stacked in a grid framework structure, comprising: a first set of parallel rails or tracks and a second set of parallel rails or tracks extending substantially perpendicular to the first set of rails or tracks in a substantially horizontal plane to form a grid pattern comprising a plurality of grid spaces, wherein the grid is supported by a set of uprights to form a plurality of vertical storage locations beneath the grid such that containers are stacked between and guided by the uprights vertically through the plurality of grid spaces; a body or skeleton attached to a first set of wheels arranged to engage the first set of parallel tracks and a second set of wheels arranged to engage the second set of parallel tracks; 53. A cargo handling device comprising: a container lifting assembly comprising the lifting assembly of any one of claims 28 to 52, wherein the gripping assembly comprises a container gripping assembly configured to grip a container.

54. 54. A method for determining an obstruction to the gripper assembly of a load assembly according to any one of claims 28 to 53, said method comprising: using the motor to raise and / or lower the gripper assembly; using the controller to determine a fault in the gripper assembly if the current output of the sensor does not correlate with winding and / or unwinding of the or each tether around the or each shaft to raise and / or lower the gripper assembly.

55. 55. A computer program comprising instructions which, when executed by a computer, cause the computer to carry out the method of claim 54.

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