Power saving load-handling devices

Abstract

An automated storage and retrieval system (ASRS) comprises a tracked system on which load handling devices move, and a transmitter to transmit commands. Each load handling device has a plurality of su

Description

Technical Field The present disclosure relates generally to the field of automated storage and retrieval systems, and in Background Some commercial and industrial activities require systems that enable the storage and retrieval of a large number of different products. For example, WO2015 / 185628A2 (Ocado) describes an automated storage and fulfilment system (ASRS) in which stacks of storage containers are arranged within a grid storage structure. The containers are accessed from above by load-handling devices operative on rails or tracks located on the top of the grid storage structure. The load-handling devices may be those described in WO2015 / 019055A1 (Ocado). Within the storage and fulfilment system, it is important to reduce the power draw of the load-handling devices during periods of low ASRS activity, and for example overnight. It is against this background that the present invention has been devised. Summary In a first aspect, there is an automated storage and retrieval system, ASRS, comprising: a first set of parallel tracks extending in a first direction and a second set of parallel tracks extending in a second direction which is transverse to the first direction; a plurality of load-handling devices, each load-handling device being configured to move on the first and second sets of tracks; wherein the ASRS comprises: a transmitter configured to transmit first and second commands; wherein each load-handling device comprises: a controller; a plurality of sub-systems controlled by the controller to operate the loadhandling device; a power source; and receiver circuitry; and wherein the controller is configured to: disable power from the power source to the controller, the plurality of sub-systems and receiver circuitry upon receipt of the first command to enable a low-power or sleep mode; periodically activate the controller and receiver circuitry for a length of time; and enable power from the power source to the plurality of the subsystems upon receipt of the second command via the receiver circuitry during the length of time else maintain the low-power or sleep mode and periodic activation of the controller and receiver circuitry for the length of time. This allows the load-handling device to minimise power draw during periods of low activity whilst resuming an active state on receipt of a sleep and wake commands respectively (i.e. the first and second commands respectively). The load-handling device may comprises a real-time clock, wherein the controller is configured to: use the real-time clock to control the periodic activation of the controller and receiver circuitry for the length of time, and / or reset the real-time clock absent the second command to maintain the periodic activation of the controller and receiver circuitry for the length of time. This allows the power draw to be set. A longer periodic activation and / or a shorter length of time will minimise the power used during the low-power or sleep mode. Similarly, a shorter periodic activation and / or a longer length of time will increase the power used during the low-power or sleep mode. Accordingly, the power draw can be balanced against the ability to exit the low-power or sleep mode as soon as possible. Each-load handling device may comprise a switch to terminate the low-power or sleep mode, and wherein the controller is configured to determine the switch has been activated to terminate the low-power or sleep mode. This allows the low-power or sleep mode to be overridden. The switch may be is configured to stop the real-time clock to terminate the low-power or sleep mode, wherein the controller is configured to detect whether the real-time clock has been stopped during the low-power or sleep mode, and exit the low-power or sleep mode if the real-time clock has been stopped during the low-power or sleep mode by enabling the power from the power source to the plurality of the sub-systems, or maintain the low-power or sleep mode if the real-time clock has not been stopped, absent the second command during the length of time. This means the load-handling device does not remain in the low-power or sleep mode if overridden by the switch. The real-time clock may comprise volatile memory and the controller is configured to write a bit sequence to the volatile memory upon enablement of the low-power or sleep mode, determine whether the bit sequence is stored in the volatile memory upon providing power from the power source to the controller; and exit the low-power or sleep mode if the bit sequence is not stored in the volatile memory by enabling the power from the power source to the plurality of the sub-systems, or maintain the low-power or sleep mode if the bit sequence is stored in the volatile memory, absent the second command during the length of time. This allows the override condition to be detected. The real-time clock may comprise an oscillator that oscillates upon activation of the low-power or sleep mode, and the controller is configured to determine whether the oscillator is oscillating upon providing power from the power source to the controller, and exit the low-power or sleep mode if the oscillator is not oscillating by enabling the power from the power source to the plurality of the sub-systems, or maintain the low-power or sleep mode if the oscillator is oscillating, absent the second command during the length of time. This allows the override condition to be detected. The switch comprises a master switch to turn the load-handling device to an off state to isolate the power source from the plurality of sub-systems, the receiver circuit, the controller, and the real-time clock. This allows the master switch to fully control the operational state of the load-handling device. The power source may comprise a removable power source, wherein the removable power source is configured such that removal of the removable power source activates the switch to terminate the low-power or sleep mode. This allows the removable power source to fully control the operational state of the load-handling device. The real-time clock may comprises a back-up power source, and the controller is configured to disable power from the power source to the real-time clock to enable the low-power or sleep mode. This allows the power draw during the low-power or sleep mode to be further reduced. The back-up power source may be disabled when the switch is activated to terminate the low-power or sleep mode. This allows the override condition to be detected. The transmitter may be dedicated for issuing the first and / or second commands. The first command and / or second command is a global command for all of the load-handling devices, or a command for a subset of the load-handling devices, or a command for an individual load-handling device. This allows full control of a fleet of load-handling devices when issuing the sleep and wake commands. The receiver circuitry may comprise a dedicated communication channel for receiving the first and / or second command. The ASRS may comprise a master controller for issuing specific operating commands to respective load-handling devices, a global communications system for transmitting the specific commands to respective loadhandling devices, wherein each load-handling device comprises a communications system to receive respective specific commands, wherein the communications system is either separate from the receiver circuitry or comprises the receiver circuitry. The first command may be received via the communications system or the receiver circuitry. The controller may be configured to disable power from the power source to the communications system when the low-power or sleep mode is enabled, and enable power from the power source to the communications system upon receipt of the second command via the receiver circuitry during the length of time. This allows the existing communication system used in the ASRS to be re-purposed and / or modified to enable the low-power or sleep mode. The first set of parallel tracks and the second set of parallel tracks may form a grid 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 for containers to be stacked between and be guided by the uprights in a vertical direction through the plurality of grid spaces, wherein each load-handling device may comprise: a body or skeleton mounted on a first set of wheels being arranged to engage with the first set of parallel tracks and a second set of wheels being arranged to engage with the second set of parallel tracks; and the plurality of sub-systems may comprise: a first sub-system comprising a drive assembly configured to drive the first or second sets of wheels to move the load-handling device along the first or second set of parallel rails respectively; a second sub-system comprising a direction-change assembly configured to raise or lower the first set of wheels and / or lower or raise the second set of wheels with respect to the body or skeleton to engage and disengage the wheels with the parallel tracks; and a third sub-system comprising a container-lifting assembly configured to raise or lower a gripping device in the vertical direction. The controller may be configured to move the load-handling to a designated area of the ASRS before effecting the first command, and / or ensure the load-handling device has is stationary before effecting the first command, and / or complete a current operation of the load-handling device before effecting the first command. This allows the low-power or sleep mode to be used in safe way. For example, a load-handling device in low-power or sleep mode does not interfere with active load-handling devices. The load-handling device may comprise a signal, such as an LED, to indicate low-power or sleep mode. The controller may be configured to set the periodic activation at about 15 minutes and the length of time at about 3 seconds. In a second aspect, there is a method of using a low-power or sleep mode in the ASRS of any preceding aspect, the method comprising using the controller to: disable power from the power source to the plurality of sub-systems, controller, and receiver circuitry upon receipt of the first command to enable a low-power or sleep mode; periodically activate the controller and receiver circuitry for a length of time; and enable power from the power source to the plurality of the sub-systems upon receipt of the second command via the receiver circuitry during the length of time, else maintain the low-power or sleep mode and periodic activation of the controller and receiver circuitry for the length of time. In a third aspect, there is a computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method of the second aspect. In a fourth aspect, there is a data processing system comprising a processor configured to carry out the method of second aspect. Brief Description of Drawings The invention is described with reference to the accompanying drawings, wherein: Figure 1 shows a known automated storage and retrieval system that uses load-handling devices; Figure 2 shows a known single load-handling device with container-lifting means in a lowered configuration; Figure 3 shows a system for operating a load-handling device; Figure 4 shows a method for enabling a low-power or sleep mode; and Figure 5 shows a systems diagram for a low-power or sleep mode in a load-handling device. Detailed Description WO2015 / 185628A (Ocado), hereby incorporated by reference, describes a known ASRS in which stacks of containers are arranged within a grid framework structure. The containers are accessed by one or more load-handling devices, otherwise known as “bots”, operative on tracks located on the top of the grid framework structure. A system of this type is illustrated schematically in Figure 1. As shown in Figures 1, stackable containers 10, also known as “bins” or “totes”, are stacked on top of one another to form stacks 12. The stacks 12 are arranged in a grid framework structure 14. The grid framework structure 14 is made up of a plurality of storage columns or grid columns. Each grid in the grid framework structure has at least one grid column to store a stack of containers. Each bin 10 typically holds a plurality of product items (not shown). The grid framework structure 14 comprises a plurality of upright members 16 that support horizontal members 18, 20. A first set of parallel horizontal grid members 18 is arranged perpendicularly to a second set of parallel horizontal members 20 in a grid pattern comprising respective grid spaces to form a horizontal grid structure 15 supported by the upright members 16. The members 16, 18, 20 are typically manufactured from metal. The bins 10 are stacked between the members 16, 18, 20 of the grid framework structure 14, so that the grid framework structure 14 guards against horizontal movement of the stacks 12 of bins 10 and guides the vertical movement of the bins 10. The top level of the grid framework structure 14 comprises a grid or grid structure 15, including rails 22 arranged in a grid pattern comprising respective grid spaces across the top of the stacks 12. The rails or tracks 22 guide a plurality of load-handling devices 30. A first set 22a of parallel rails 22 guide movement of the robotic load-handling devices 30 in a first direction (e.g. an X-direction along track 22a) across the top of the grid framework structure 14. A second set 22b of parallel rails 22, arranged perpendicular to the first set 22a, guide movement of the load-handling devices 30 in a second direction (e.g. a Y-direction along track 22b), perpendicular to the first direction. In this way, the rails 22 allow the robotic load-handling devices 30 to move laterally in two dimensions in the horizontal X-Y plane. A load-handling device 30 can be moved into position above any of the stacks 12. A known form of load-handling device 30 shown in Figure 2 is described in WO2015 / 019055 (Ocado), hereby incorporated by reference. The load-handling device 30 comprises a vehicle 32, which is 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 on the front of the vehicle 32 and a pair of wheels 34 on the back of the vehicle 32, is arranged to engage with 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, is arranged to engage with two adjacent rails of the second set 22b of rails 22. Each set of wheels 34, 36 can be lifted and lowered, by way of a direction-change assembly (i.e. a third subsystem), so that either the first set of wheels 34 or the second set of wheels 36 is engaged with the respective set of rails 22a, 22b at any one time. For example, when the first set of wheels 34 is engaged with the first set of rails 22a and the second set of wheels 36 is lifted clear from the rails 22, the first set of wheels 34 can be driven, by way of a drive assembly (i.e. a first sub-system) housed in the vehicle 32, to move the loadhandling device 30 in the X-direction. To achieve movement in the Y-direction, the first set of wheels 34 is lifted clear of the rails 22, and the second set of wheels 36 is lowered into engagement with the second set 22b of 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. The load-handling device 30 is equipped with a container-lifting device (i.e. a second-sub-system) or assembly, e.g. a crane mechanism, to lift a storage container from above. The lifting device comprises a winch tether or cable 38 wound on a spool or reel and a gripper device 39. The lifting device shown in Figure 2 comprises a set of four lifting tethers 38 extending in a vertical direction. The tethers 38 are connected at or near the respective four corners of the gripper device 39, e.g. a lifting frame, for releasable connection to a storage container 10. The gripper device 39 is configured to releasably grip the top of a storage container 10 to lift it from a stack of containers in a storage system of the type shown in Figure 1. To remove a bin 10 from the top of a stack 12, the load-handling device 30 is first moved in the X- and Y-directions to position the gripper device 39 in a respective grid space above the stack 12. The gripper device 39 is then lowered vertically in the Z-direction to engage with the bin 10 on the top of the stack 12. The gripper device 39 grips the bin 10, and is then pulled upwards by the cables 38, with the bin 10 attached. At the top of its vertical travel, the bin 10 is held above the rails 22 accommodated within the vehicle body (or skeleton) 32. In this way, the load-handling device 30 can be moved to a different position in the X-Y plane, carrying the bin 10 along with it, to transport the bin 10 to another location. On reaching the target location (e.g. another stack 12, an access point in the storage system, or a conveyor belt) the bin or container 10 can be lowered from the container receiving portion and released from the grabber device 39. Each load-handling device has a power source that is recharged or replaced by the loadhandling device moving to a charging area or battery swap area respectively of the ASRS. The ASRS has a master controller that coordinates the movement and operation of the load-handling devices. Therefore, the master controller instructs each loadhandling device to move containers to and from different locations in the ASRS and recharge / replace the power source when needed in a way that maximises throughput efficiency. In other words, the ASRS ensures that the required number of load-handling devices to achieve a required throughput, is available. However, there may be times of low or zero ASRS activity, such as overnight or at the weekends. In such a case, each load-handling device will be awaiting further instruction from the master controller. Although power intensive operations such as moving the load-handling device to a different location, or changing direction, or lifting / hoisting a heavy container are not occurring, the respective sub-systems of the load-handling device are still in an active state. The power draw can be significant and will eventually deplete the power source, and can happen in as little as 5 hours. Whilst one solution may be to constantly recharge / replace the power source of the load-handling devices, this is a wasteful use of power, which across a fleet of load-handling devices can be significant. It would be useful to have a low-power of sleep mode that can minimise power use in the load-handling device during times of low or zero ASRS throughout. Figure 3 shows a system 300 according to the invention. A controller (or processor) 310 may interact with local storage 315. The controller controls a number of sub-systems such as the container lifting assembly 320, direction-change assembly 330, and drive assembly 340, described above. Each of these sub-systems typically has at least one motor, and associated sensors and control electronics. The controller 310 can receive instructions form the master controller via a communications system 350. The communications system may be a cellular communications system, such as that described in WO2015185726A2, where a global cellular communications system is used in the ASRS to control the load-handling devices. Whilst separate receiver circuitry 370 is shown, the communications system may also be configured to offer the same functionality as the receiver circuitry as described below. The controller is connected to power source 360 and can control power to each of the sub-systems such as the container lifting assembly 320, direction-change assembly 330, and drive assembly 340, communications system 350, and receiver circuitry 370. It will be appreciated that power may not be routed directly through the controller, but via respective power switches, such as relays. In general, the system shown in Figure 300 can be used for a low-power or sleep mode in the load-handling device. The ASRS will typically have a transmitter for issuing commands from the master controller. The transmitter may be part of the existing global communications system (which may be cellular based) or a separate dedicated system for the low-power or sleep mode. Regardless of the type of transmitter used, the transmitter sends first and second commands to the load-handling device. A method 400 for enabling the low-power or sleep mode is shown in Figure 4. On receipt of the first command, the controller is configured to disable 410 power from the power source to the controller (i.e. itself), the plurality of sub-systems (such as the container lifting assembly 320, direction-change assembly 330, and drive assembly 340, and communications system 350) and receiver circuitry. This reduces the power consumption of the load-handling device to be as low as possible, and to an extent is indistinguishable from fully isolating / removing the power source. The controller is then periodically 420 activated along with the receiver circuitry for a length of time. The period of activation and length of time are both configurable, but in one example the activation period is every ~15 minutes and the length of time is ~3 seconds. During the length of time, if a second command is received, the controller is configured to enable 430, 440 power from the power source to the plurality of the sub-systems. In effect, the load-handling device returns to an active state where each of the sub-systems can be used to operate the load-handling device as described above. Absent the second command being received (and thus transmitted), the low-power or sleep mode along with the periodic activation of the controller and receiver circuitry for the length of time is maintained 430, 420. It will be appreciated that the second command may be continuously transmitted, but the second command will only be received (i.e. detected) by the controller during the length of time. It will be appreciated that both the first and second commands may be global or only to a subset of load-handling device, or an individual load-handling device. Additionally, before effecting the low-power or sleep mode, the load-handing device may move to a designated area (such as a corner of the grid pattern so that other load-handling devices of the ASRS may operate unimpeded in a centre region of the grid pattern), and / or ensure the load-handling device is stationary, and / or complete a current operation (such as direction change, a raising / lowering of the container-lifting assembly, or a movement to a grid space). In general, after the load-handling device enters low-power or sleep mode on receipt of a sleep signal (i.e. the first command), a periodic check for a wake-up signal (i.e. the second command) takes place. By only checking periodically using the controller and receiver circuitry, the overall power demand in the load handling device is minimised during the low-power or sleep mode. In one example, the controller may only boot up to the extent that is required to check for receipt of the second command via the receiver circuitry. Similarly, the receiver circuitry may provide a dedicated communications channel for the sole purpose of receiving the second command, which in general will result in a simple circuit with minimal power draw. An example receiver circuit is the ‘Radiosafe’ series produced by Jay Electronique™ The receiver circuitry may also receive the first command. In one example, the power use during low-power or sleep mode, with an activation period of -15 minutes for a length of time of -3 second, is -0.03% of that in active mode (where all systems are ready to act on commands issued by the master controller). Figure 5 shows an example diagram of system 500 that can carry out the method of Figure 4. The controller 520 may be one implementation of controller 310. Controller 520 interacts with real-time clock 510. It will be appreciated that the real-time clock may actually be a direct function (i.e. sub-unit) of the controller or a separate unit / circuit / chip, such as MCP79510 SPI RTCC by Microchip Technology™. The controller 520 interacts with a sub-system power control unit, 590 which in effect is a power switch for each of the sub-systems. The controller 520 also interacts with receiver circuity 580, where the receiver circuitry also has antenna 585. A power source 570 of the load-handling device provides power to each of the component / units shown in Figure 5. The controller, upon receiving the first command, triggers an alarm function 520 in the real-time clock to set an alarm condition (i.e. a pre-defined period of time in the future). After the controller has triggered or armed the alarm function, power is removed from the controller itself, the sub-systems (via the sub-system power control unit), and the receiver circuitry. It will be appreciated that as part of triggering or arming the alarm function, the controller may set both the periodic activation and the length of time to control activation of the controller and receiver circuitry as described above. Once the alarm condition has been reached, an output pin of the real-time circuit sends a signal to activate the controller and the receiver circuitry. Assuming the second command is received when the receiver circuitry is active, the controller will interface with the subsystem power control unit to enable power to the respective sub units. That is, the loadhandling unit will return to an active state. Absent the second command, the controller will reset the alarm function on the real-time clock and repeat the above process in line with the method of Figure 4. To minimise the power draw during the low-power or sleep mode, the real-time clock itself may also be powered down so that only the alarm function is powered by the power source. Alternatively, the real-time clock may comprise a back-up power source 540. Thus, when the first command is received and the alarm function has been set, the controller also disables the power supply to the real-time clock. The back-up power supply can be charged when connected to the power source. Additionally or alternatively, it may be necessary to override the low-power or sleep mode so that the load-handling device can return to an active state prior to receiving a second command. Thus, a switch 560 can be used to stop the real-time clock and terminate the low-power or sleep mode. The controller is configured to detect that the real-time clock has been stopped prior to the alarm condition arising. If the controller detects the real-time clock has been stopped prior to the alarm condition arising, the controller will proceed to boot-up and return the load-handling device to an active state. In one example, the real-time clock has volatile memory 530, such as SRAM. Upon receiving the first command, the controller writes a bit sequence to the SRAM. If the switch 560 were to remove power from the real-time clock, this bit sequence will not persist. Thus, when the controller is activated, it can check whether the bit sequence is stored in the volatile memory of the real-time clock. If the bit sequence is detected, the controller can proceed in line with the method of Figure 4 and exit low-power or sleep mode if the second command has been received. If the bit sequence has not been detected, the controller will then proceed to boot-up and return the load-handling device to an active state. That is, the override has been detected and the second command is not required to disable the low-power or sleep mode. In an additional or alternative example, if the switch 560 were to remove power from the real-time clock, an oscillator of the real-time clock will stop. Thus, when the controller is activated, it can check whether the oscillator is still oscillating. If oscillation of the oscillator is detected, the controller can proceed in line with the method of Figure 4 and exit low-power or sleep mode if the second command has been received. If oscillation of the oscillator is not detected, the controller will then proceed to boot-up and return the load-handling device to an active state. That is, the override has been detected and the second command is not required to disable the low-power or sleep mode. In either of the above examples, switch 560 may remove power from the load-handling device (and thus the real-time circuit). Switch 560 may be a master switch (i.e. on off switch) that isolates the power supply from the load-handling device. Alternatively or additionally, switch 560 may be disengaged and engaged when the power source is removable, and is removed and replaced respectively. If a back-up power supply is used in the real-time clock, a switch 550 will be triggered in line with switch 560 to isolate power to the real-time clock. It will be appreciated that instead of the examples above, switch 560 may directly trigger an input to the controller that overrides the low-power or sleep mode. In this document, “controller” is intended to include any hardware which is suitable for controlling (e.g. providing instructions to) one or more other components. For example, a processor equipped with one or more memories and appropriate software to process data relating to a component or components and send appropriate instructions to the component(s) to enable the component(s) to perform its / their intended function(s). Furthermore, the invention can take the form of a computer program embodied as a computer-readable medium having computer executable code for use by or in connection with a computer. 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 alterations to the disclosed embodiments without departing from the scope of this invention.

Claims

1. An automated storage and retrieval system, ASRS, comprising:a first set of parallel tracks extending in a first direction and a second set of parallel tracks extending in a second direction which is transverse to the first direction;a plurality of load-handling devices, each load-handling device being configured to move on the first and second sets of tracks;wherein the ASRS comprises:a transmitter configured to transmit first and second commands;wherein each load-handling device comprises:a controller;a plurality of sub-systems controlled by the controller to operate the loadhandling device;a power source; andreceiver circuitry; andwherein the controller is configured to:disable power from the power source to the controller, the plurality of sub-systems and receiver circuitry upon receipt of the first command to enable a low-power or sleep mode;periodically activate the controller and receiver circuitry for a length of time; andenable power from the power source to the plurality of the subsystems upon receipt of the second command via the receiver circuitry during the length of time else maintain the low-power or sleep mode and periodic activation of the controller and receiver circuitry for the length of time.

2. The ASRS of claim 1, wherein the load-handling device comprises a real-time clock, wherein the controller is configured to:use the real-time clock to control the periodic activation of the controller and receiver circuitry for the length of time; and / orreset the real-time clock absent the second command to maintain the periodic activation of the controller and receiver circuitry for the length of time.

3. The ASRS of claim 2, wherein each-load handling device comprises a switch to terminate the low-power or sleep mode, and wherein the controller is configured to determine the switch has been activated to terminate the low-power or sleep mode.

4. The ASRS of claim 3, wherein the switch is configured to stop the real-time clock to terminate the low-power or sleep mode, wherein the controller is configured to:detect whether the real-time clock has been stopped during the low-power or sleep mode; andexit the low-power or sleep mode if the real-time clock has been stopped during the low-power or sleep mode by enabling the power from the power source to the plurality of the sub-systems; ormaintain the low-power or sleep mode if the real-time clock has not been stopped, absent the second command during the length of time.

5. The ASRS of claim 4, wherein the real-time clock comprises volatile memory and the controller is configured to:write a bit sequence to the volatile memory upon enablement of the low-power or sleep mode;determine whether the bit sequence is stored in the volatile memory upon providing power from the power source to the controller; andexit the low-power or sleep mode if the bit sequence is not stored in the volatile memory by enabling the power from the power source to the plurality of the sub-systems;ormaintain the low-power or sleep mode if the bit sequence is stored in the volatile memory, absent the second command during the length of time.

6. The ASRS of claim 4 or 5, wherein the real-time clock comprises an oscillator that oscillates upon activation of the low-power or sleep mode, and the controller is configured to:determine whether the oscillator is oscillating upon providing power from the power source to the controller; andexit the low-power or sleep mode if the oscillator is not oscillating by enabling the power from the power source to the plurality of the sub-systems; ormaintain the low-power or sleep mode if the oscillator is oscillating, absent the second command during the length of time.

7. The ASRS of claims 2-6, wherein the switch comprises a master switch to turnthe load-handling device to an off state to isolate the power source from the plurality of sub-systems, the receiver circuit, the controller, and the real-time clock.

8. The ASRS of claims 3-7, wherein the power source comprises a removable power source, wherein the removable power source is configured such that removal of the removable power source activates the switch to terminate the low-power or sleep mode.

9. The ASRS of claims 2-8, wherein the real-time clock comprises a back-up power source, and the controller is configured to disable power from the power source to the real-time clock to enable the low-power or sleep mode.

10. The ASRS of claim 9, when dependent on claims 3-8, wherein the back-up power source is disabled when the switch is activated to terminate the low-power or sleep mode.

11. The ASRS of any preceding claim, the transmitter is dedicated for issuing the first and / or second commands.

12. The ASRS of claim 11, wherein the first command and / or second command is: a global command for all of the load-handling devices; or a command for a subset of the load-handling devices; or a command for an individual load-handling device.

13. The ASRS of claims 11 or 12, wherein the receiver circuitry comprises a dedicated communication channel for receiving the first and / or second command.

14. The ASRS of any preceding claim, further comprising:a master controller for issuing specific operating commands to respective loadhandling devices;a global communications system for transmitting the specific commands to respective load-handling devices;wherein each load-handling device comprises a communications system to receive respective specific commands, wherein the communications system is either separate from the receiver circuitry or comprises the receiver circuitry.

15. The ASRS of claim 14, wherein the first command is received via the communications system or the receiver circuitry.

16. The ASRS of claims 15, wherein the controller is configured to:disable power from the power source to the communications system when the low-power or sleep mode is enabled; andenable power from the power source to the communications system upon receipt of the second command via the receiver circuitry during the length of time.

17. The ASRS of any preceding claim, wherein:the first set of parallel tracks and the second set of parallel tracks form a grid 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 for containers to be stacked between and be guided by the uprights in a vertical direction through the plurality of grid spaces, wherein each load-handling device comprises:a body or skeleton mounted on a first set of wheels being arranged to engage with the first set of parallel tracks and a second set of wheels being arranged to engage with the second set of parallel tracks; and the plurality of sub-systems comprise:a first sub-system comprising a drive assembly configured to drive the first or second sets of wheels to move the load-handling device along the first or second set of parallel rails respectively;a second sub-system comprising a direction-change assembly configured to raise or lower the first set of wheels and / or lower or raise the second set of wheels with respect to the body or skeleton to engage and disengage the wheels with the parallel tracks; anda third sub-system comprising a container-lifting assembly configured to raise or lower a gripping device in the vertical direction.

18. The ASRS of any preceding claim, wherein the controller is configured to:move the load-handling to a designated area of the ASRS before effecting the first command; and / orensure the load-handling device has is stationary before effecting the first command; and / orcomplete a current operation of the load-handling device before effecting the first command.

19. The ASRS of any preceding claim wherein the load-handling device comprises a signal, such as an LED, to indicate low-power or sleep mode.

20. The ASRS of any preceding claim, wherein the controller is configured to set the periodic activation at about 15 minutes and the length of time at about 3 seconds.

21. A method of using a low-power or sleep mode in the ASRS of any preceding claim, the method comprising using the controller to:disable power from the power source to the plurality of sub-systems, controller, and receiver circuitry upon receipt of the first command to enable a low-power or sleep mode;periodically activate the controller and receiver circuitry for a length of time; and enable power from the power source to the plurality of the sub-systems upon receipt of the second command via the receiver circuitry during the length of time, else maintain the low-power or sleep mode and periodic activation of the controller and receiver circuitry for the length of time.

22. A computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method of claim 21.

23. A data processing system comprising a processor configured to carry out themethod of claim 21.

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